Pelvis

Pelvis

Overview
In human anatomy
Human anatomy
Human anatomy is primarily the scientific study of the morphology of the human body. Anatomy is subdivided into gross anatomy and microscopic anatomy. Gross anatomy is the study of anatomical structures that can be seen by the naked eye...

, the pelvis (plural pelves or pelvises, sometimes also called pelvic region of the trunk) is the lower part of the trunk, between the abdomen and the lower limb
Lower limb
The lower limb is a limb of the body.According to Terminologia Anatomica, it includes the pelvic girdle, buttocks, hip, and thigh, as well as the components distal to the knee.-References:...

s (legs).
The pelvis includes several structures:
  • the bony pelvis, or pelvic skeleton, the part of the skeleton connecting the lumbar region of the spine to the femur
    Femur
    The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...

    s, subdivided into:
    • the pelvic girdle (the two hip bone
      Hip bone
      The hip bone, innominate bone or coxal bone is a large, flattened, irregularly shaped bone, constricted in the center and expanded above and below...

      s, which are part of the appendicular skeleton
      Appendicular skeleton
      The Appendicular skeleton is composed of 126 bones in the human body. The word appendicular is the adjective of the noun appendage, which itself means a part that is joined to something larger...

      ) and
    • the pelvic region of the spine (sacrum
      Sacrum
      In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...

      , and coccyx
      Coccyx
      The coccyx , commonly referred to as the tailbone, is the final segment of the vertebral column. Comprising three to five separate or fused vertebrae below the sacrum, it is attached to the sacrum by a fibrocartilaginous joint, the sacrococcygeal symphysis, which permits limited movement between...

      , which are part of the axial skeleton
      Axial skeleton
      The axial skeleton consists of the 80 bones along the central axis of the human body. It is composed of six parts; the human skull, the ossicles of the middle ear, the hyoid bone of the throat, the rib cage, sternum and the vertebral column...

      )
  • the pelvic cavity
    Pelvic cavity
    -External links:* * *...

    , typically defined as a small part of the space enclosed by the pelvic skeleton, delimited by the pelvic brim
    Pelvic brim
    The pelvic brim is the edge of the pelvic inlet. It is an approximately apple-shaped line passing through the prominence of the sacrum, the arcuate and pectineal lines, and the upper margin of the pubic symphysis....

     above and the pelvic floor
    Pelvic floor
    The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed by the levatores ani and coccygei, with which may be included the...

     below; alternatively, the pelvic cavity is sometimes also defined as the whole space enclosed by the pelvic skeleton, subdivided into:
    • the greater
      Greater pelvis
      The greater pelvis is a portion of the cavity surrounded by the skeleton of the pelvis, situated above and in front of the pelvic brim...

      or false pelvis , above the pelvic brim
      Pelvic brim
      The pelvic brim is the edge of the pelvic inlet. It is an approximately apple-shaped line passing through the prominence of the sacrum, the arcuate and pectineal lines, and the upper margin of the pubic symphysis....

    • the lesser
      Lesser pelvis
      The lesser pelvis is that part of the space enclosed by the skeleton of the pelvis which is situated between the pelvic inlet and the pelvic floor. Some authors call this cavity the pelvic cavity...

      or true pelvis , below the pelvic brim,
  • the pelvic floor
    Pelvic floor
    The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed by the levatores ani and coccygei, with which may be included the...

    or pelvic diaphragm, below the pelvic cavity,
  • the perineum
    Perineum
    In human anatomy, the perineum is a region of the body including the perineal body and surrounding structures...

    , below the pelvic diaphragm.


In the adult human, the pelvic skeleton is formed in the area of the back (posterior dorsal), by the sacrum
Sacrum
In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...

 and the coccyx
Coccyx
The coccyx , commonly referred to as the tailbone, is the final segment of the vertebral column. Comprising three to five separate or fused vertebrae below the sacrum, it is attached to the sacrum by a fibrocartilaginous joint, the sacrococcygeal symphysis, which permits limited movement between...

 (the caudal portion of the axial skeleton
Axial skeleton
The axial skeleton consists of the 80 bones along the central axis of the human body. It is composed of six parts; the human skull, the ossicles of the middle ear, the hyoid bone of the throat, the rib cage, sternum and the vertebral column...

), and laterally and anteriorly (forward and to the side), by a pair of hip bone
Hip bone
The hip bone, innominate bone or coxal bone is a large, flattened, irregularly shaped bone, constricted in the center and expanded above and below...

s, the lower extremity
Human leg
The human leg is the entire lower extremity or limb of the human body, including the foot, thigh and even the hip or gluteal region; however, the precise definition in human anatomy refers only to the section of the lower limb extending from the knee to the ankle.Legs are used for standing,...

, (parts of the appendicular skeleton
Appendicular skeleton
The Appendicular skeleton is composed of 126 bones in the human body. The word appendicular is the adjective of the noun appendage, which itself means a part that is joined to something larger...

).
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Encyclopedia
In human anatomy
Human anatomy
Human anatomy is primarily the scientific study of the morphology of the human body. Anatomy is subdivided into gross anatomy and microscopic anatomy. Gross anatomy is the study of anatomical structures that can be seen by the naked eye...

, the pelvis (plural pelves or pelvises, sometimes also called pelvic region of the trunk) is the lower part of the trunk, between the abdomen and the lower limb
Lower limb
The lower limb is a limb of the body.According to Terminologia Anatomica, it includes the pelvic girdle, buttocks, hip, and thigh, as well as the components distal to the knee.-References:...

s (legs).
The pelvis includes several structures:
  • the bony pelvis, or pelvic skeleton, the part of the skeleton connecting the lumbar region of the spine to the femur
    Femur
    The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...

    s, subdivided into:
    • the pelvic girdle (the two hip bone
      Hip bone
      The hip bone, innominate bone or coxal bone is a large, flattened, irregularly shaped bone, constricted in the center and expanded above and below...

      s, which are part of the appendicular skeleton
      Appendicular skeleton
      The Appendicular skeleton is composed of 126 bones in the human body. The word appendicular is the adjective of the noun appendage, which itself means a part that is joined to something larger...

      ) and
    • the pelvic region of the spine (sacrum
      Sacrum
      In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...

      , and coccyx
      Coccyx
      The coccyx , commonly referred to as the tailbone, is the final segment of the vertebral column. Comprising three to five separate or fused vertebrae below the sacrum, it is attached to the sacrum by a fibrocartilaginous joint, the sacrococcygeal symphysis, which permits limited movement between...

      , which are part of the axial skeleton
      Axial skeleton
      The axial skeleton consists of the 80 bones along the central axis of the human body. It is composed of six parts; the human skull, the ossicles of the middle ear, the hyoid bone of the throat, the rib cage, sternum and the vertebral column...

      )
  • the pelvic cavity
    Pelvic cavity
    -External links:* * *...

    , typically defined as a small part of the space enclosed by the pelvic skeleton, delimited by the pelvic brim
    Pelvic brim
    The pelvic brim is the edge of the pelvic inlet. It is an approximately apple-shaped line passing through the prominence of the sacrum, the arcuate and pectineal lines, and the upper margin of the pubic symphysis....

     above and the pelvic floor
    Pelvic floor
    The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed by the levatores ani and coccygei, with which may be included the...

     below; alternatively, the pelvic cavity is sometimes also defined as the whole space enclosed by the pelvic skeleton, subdivided into:
    • the greater
      Greater pelvis
      The greater pelvis is a portion of the cavity surrounded by the skeleton of the pelvis, situated above and in front of the pelvic brim...

      or false pelvis , above the pelvic brim
      Pelvic brim
      The pelvic brim is the edge of the pelvic inlet. It is an approximately apple-shaped line passing through the prominence of the sacrum, the arcuate and pectineal lines, and the upper margin of the pubic symphysis....

    • the lesser
      Lesser pelvis
      The lesser pelvis is that part of the space enclosed by the skeleton of the pelvis which is situated between the pelvic inlet and the pelvic floor. Some authors call this cavity the pelvic cavity...

      or true pelvis , below the pelvic brim,
  • the pelvic floor
    Pelvic floor
    The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed by the levatores ani and coccygei, with which may be included the...

    or pelvic diaphragm, below the pelvic cavity,
  • the perineum
    Perineum
    In human anatomy, the perineum is a region of the body including the perineal body and surrounding structures...

    , below the pelvic diaphragm.


In the adult human, the pelvic skeleton is formed in the area of the back (posterior dorsal), by the sacrum
Sacrum
In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...

 and the coccyx
Coccyx
The coccyx , commonly referred to as the tailbone, is the final segment of the vertebral column. Comprising three to five separate or fused vertebrae below the sacrum, it is attached to the sacrum by a fibrocartilaginous joint, the sacrococcygeal symphysis, which permits limited movement between...

 (the caudal portion of the axial skeleton
Axial skeleton
The axial skeleton consists of the 80 bones along the central axis of the human body. It is composed of six parts; the human skull, the ossicles of the middle ear, the hyoid bone of the throat, the rib cage, sternum and the vertebral column...

), and laterally and anteriorly (forward and to the side), by a pair of hip bone
Hip bone
The hip bone, innominate bone or coxal bone is a large, flattened, irregularly shaped bone, constricted in the center and expanded above and below...

s, the lower extremity
Human leg
The human leg is the entire lower extremity or limb of the human body, including the foot, thigh and even the hip or gluteal region; however, the precise definition in human anatomy refers only to the section of the lower limb extending from the knee to the ankle.Legs are used for standing,...

, (parts of the appendicular skeleton
Appendicular skeleton
The Appendicular skeleton is composed of 126 bones in the human body. The word appendicular is the adjective of the noun appendage, which itself means a part that is joined to something larger...

). In an adult human being, the pelvic skeleton is thus composed of three large bones, and the coccyx (3–5 bones); however, before puberty
Puberty
Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...

, each hip bone consists of three discrete (separate) bones — the ilium
Ilium (bone)
The ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...

, ischium, pubis
Pubis (bone)
In vertebrates, the pubic bone is the ventral and anterior of the three principal bones composing either half of the pelvis.It is covered by a layer of fat, which is covered by the mons pubis....

 — that have yet to fuse at adulthood; thus, in puberty, the human pelvic skeleton can comprise more than 10 bones, depending upon the composition of the person’s coccyx.

Brief description


The bony pelvis or pelvic skeleton is the section between the legs and the torso that connects the lumbar part of the spine (backbone) to the thigh bones. In adults, it is mainly constructed of two hip bones, one on the right and one on the left of the body. The two hip bones are made up of 3 sections, the Ilium, Ischium and Pubis. These sections are fused together during puberty, meaning in childhood they are separate bones. Along with the hip bones is the Sacrum, the upper-middle part of the pelvis, which connects the spine (backbone) to the pelvis. To make this possible, the hip bones are attached to the Sacrum.

The gap enclosed by the pelvic skeleton, called pelvic cavity, is the section of the body underneath the abdomen and mainly consists of the reproductive organs (sex organs) and the rectum.

Bony pelvis




Functions


The skeleton of the pelvis is a basin-shaped ring of bones connecting the vertebral column to the femurs.

Its primary functions are to bear the weight of the upper body when sitting and standing; transfer that weight from the axial skeleton to the lower appendicular skeleton when standing and walking; and provide attachments for and withstand the forces of the powerful muscles of locomotion and posture. Compared to the shoulder girdle, the pelvic girdle is thus strong and rigid.
Its secondary functions are to contain and protect the pelvic and abdominopelvic viscera (inferior parts of the urinary tracts, internal reproductive organs); provide attachment for external reproductive organs and associated muscles and membranes.

As a mechanical structure


The pelvic girdle consists of the two hip bones. The hip bones are connected to each other anteriorly at the pubic symphysis
Pubic symphysis
The pubic symphysis or symphysis pubis is the midline cartilaginous joint uniting the superior rami of the left and right pubic bones. It is located anterior to the urinary bladder and superior to the external genitalia; for females it is above the vulva and for males it is above the penis...

, and posteriorly to the sacrum
Sacrum
In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...

 at the sacroiliac joint
Sacroiliac joint
The sacroiliac joint or SI joint is the joint in the bony pelvis between the sacrum and the ilium of the pelvis, which are joined together by strong ligaments. In humans, the sacrum supports the spine and is supported in turn by an ilium on each side...

s to form the pelvic ring. The ring is very stable and allows very little mobility, a prerequisite for transmitting loads from the trunk to the lower limbs.
As a mechanical structure the pelvis may be thought of as four roughly triangular and twisted rings. Each superior ring is formed by the iliac bone; the anterior side stretches from the acetabulum up to the anterior superior iliac spine
Anterior superior iliac spine
The anterior superior iliac spine is an important landmark of surface anatomy. It refers to the anterior extremity of the iliac crest of the pelvis, which provides attachment for the inguinal ligament, and the sartorius muscle...

; the posterior side reaches from the top of the acetabulum to the sacroiliac joint
Sacroiliac joint
The sacroiliac joint or SI joint is the joint in the bony pelvis between the sacrum and the ilium of the pelvis, which are joined together by strong ligaments. In humans, the sacrum supports the spine and is supported in turn by an ilium on each side...

; and the third side is formed by the palpable
Palpation
Palpation is used as part of a physical examination in which an object is felt to determine its size, shape, firmness, or location...

 iliac crest
Iliac crest
-External links: - "Superficial muscles of the gluteal region and posterior thigh." - "Anterior Abdominal Wall: Osteology and Surface Anatomy " - "The Back, Posterior View" * *...

. The lower ring, formed by the rami of the pubic and ischial bones, supports the acetabulum and is twisted 80-90 degrees in relation to the superior ring.
An alternative approach is to consider the pelvis part of an integrated mechanical system based on the tensegrity
Tensegrity
Tensegrity, tensional integrity or floating compression, is a structural principle based on the use of isolated components in compression inside a net of continuous tension, in such a way that the compressed members do not touch each other and the prestressed tensioned members delineate the...

 icosahedron
Icosahedron
In geometry, an icosahedron is a regular polyhedron with 20 identical equilateral triangular faces, 30 edges and 12 vertices. It is one of the five Platonic solids....

 as an infinite element. Such a system is able to withstand omnidirectional forces — ranging from weight-bearing to childbearing — and, as a low energy requiring system, is favoured by natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

.
The pelvic inclination angle is the single most important element of the human body posture and is adjusted at the hips. It is also one of the rare things that can be measured at the assessment of the posture. A simple method of measurement was described by the British orthopedist Philip Willes and is performed by using an inclinometer
Inclinometer
An inclinometer or clinometer is an instrument for measuring angles of slope , elevation or depression of an object with respect to gravity...

.

Junctions



The two hip bones are joined anteriorly at the pubic symphysis
Pubic symphysis
The pubic symphysis or symphysis pubis is the midline cartilaginous joint uniting the superior rami of the left and right pubic bones. It is located anterior to the urinary bladder and superior to the external genitalia; for females it is above the vulva and for males it is above the penis...

 by a fibrous cartilage
Fibrocartilage
White fibrocartilage consists of a mixture of white fibrous tissue and cartilaginous tissue in various proportions. It owes its flexibility and toughness to the former of these constituents, and its elasticity to the latter...

 covered by a hyaline cartilage
Hyaline cartilage
Hyaline cartilage consists of a slimy mass, pearly bluish in colour with firm consistency and considerable collagen. It contains no nerves or blood vessels, and its structure is relatively simple....

, the interpubic disk, within which a non-synovial cavity might be present. Two ligaments, the superior
Superior pubic ligament
The superior pubic ligament connects together the two pubic bones superiorly, extending laterally as far as the pubic tubercles....

 and inferior pubic ligament
Inferior pubic ligament
The inferior pubic ligament is a thick, triangular arch of ligamentous fibers, connecting together the two pubic bones below, and forming the upper boundary of the pubic arch.Above, it is blended with the interpubic fibrocartilaginous lamina; laterally, it is attached to the inferior rami of...

s, reinforce the symphysis.

Both sacroiliac joint
Sacroiliac joint
The sacroiliac joint or SI joint is the joint in the bony pelvis between the sacrum and the ilium of the pelvis, which are joined together by strong ligaments. In humans, the sacrum supports the spine and is supported in turn by an ilium on each side...

s
, formed between the auricular surfaces of the sacrum and the two hip bones. are amphiarthroses, almost immobile joints enclosed by very taut joint capsules. This capsule is strengthened by the ventral
Anterior sacroiliac ligament
The anterior sacroiliac ligament consists of numerous thin bands, which connect the anterior surface of the lateral part of the sacrum to the margin of the auricular surface of the ilium and to the preauricular sulcus....

, interosseous
Interosseous sacroiliac ligament
The Interosseous Sacroiliac Ligament lies deep to the posterior ligament, and consists of a series of short, strong fibers connecting the tuberosities of the sacrum and ilium. The major function of the interosseous sacroiliac ligament is to keep the sacrum and ilium together and therefore prevent...

, and dorsal sacroiliac ligaments
Posterior sacroiliac ligament
The posterior sacroiliac ligament is situated in a deep depression between the sacrum and ilium behind; it is strong and forms the chief bond of union between the bones.It consists of numerous fasciculi, which pass between the bones in various directions....

.
The most important accessory ligaments of the sacroiliac joint are the sacrospinous
Sacrospinous ligament
-External links: - "Posterior view of the bones and ligaments of the hip joint."*...

 and sacrotuberous ligament
Sacrotuberous ligament
The sacrotuberous ligament is situated at the lower and back part of the pelvis. It is flat, and triangular in form; narrower in the middle than at the ends....

s which stabilize the hip bone on the sacrum and prevent the promonotory from tilting forward. Additionally, these two ligaments transform the greater
Greater sciatic notch
Above the ischial spine is a large notch, the greater sciatic notch, converted into a foramen by the sacrospinous ligament.It transmits the Piriformis, the superior and inferior gluteal vessels and nerves, the sciatic and posterior femoral cutaneous nerves, the internal pudendal vessels, and the...

 and lesser sciatic notch
Lesser sciatic notch
Below the ischial spine is a smaller notch, the lesser sciatic notch; it is smooth, coated in the recent state with cartilage, the surface of which presents two or three ridges corresponding to the subdivisions of the tendon of the Obturator internus, which winds over it.It is converted into a...

es into the greater
Greater sciatic foramen
-Boundaries:It is bounded as follows:* anterolaterally by the greater sciatic notch of the illium* posteromedially by the sacrotuberous ligament* inferiorly by the sacrospinous ligament and the ischial spine* superiorly by the anterior sacroilliac ligament...

 and lesser foramina
Lesser sciatic foramen
An opening between the pelvis and the posterior thigh, the foramen is formed by the sacrotuberous ligament which runs between the sacrum and the ischial tuberosity and the sacrospinous ligament which runs between the sacrum and the ischial spine.-Boundaries:...

, a pair of important pelvic openings.
The iliolumbar ligament is a strong ligament which connects the tip of the transverse process of the fifth lumbar vertebra to the posterior part of the inner lip of the iliac crest. It can be thought of as the lower border of the thoracolumbar fascia
Thoracolumbar fascia
The thoracolumbar fascia is a deep investing membrane which covers the deep muscles of the back of the trunk. It is made up of three layers, anterior, middle, and posterior. The anterior layer is the thinnest and the posterior layer is the thickest. Two spaces are formed between these three...

 and is occasionally accompanied by a smaller ligamentous band passing between the fourth lumbar vertebra and the iliac crest. The lateral lumbosacral ligament is partly continuous with the iliolumbar ligament. It passes between the transverse process of the fifth vertebra to the ala of the sacrum
Ala of sacrum
On either side of the body of the base of the sacrum is a large triangular surface, which supports the Psoas major and the lumbosacral trunk, and in the articulated pelvis is continuous with the iliac fossa...

 where it intermingle with the anterior sacroiliac ligament.
The joint between the sacrum and the coccyx, the sacrococcygeal symphysis, is strengthened by a series of ligaments. The anterior sacrococcygeal ligament is an extension of the anterior longitudinal ligament
Anterior longitudinal ligament
The anterior longitudinal ligament is a ligament that runs down the anterior surface of the spine. It traverses all of the vertebral bodies and intervertebral discs....

 (ALL) that run down the anterior side of the vertebral bodies
Body of vertebra
The body is the largest part of a vertebra, and is more or less cylindrical in shape. For vertebrates other than humans, this structure is usually called a centrum....

. Its irregular fibers blend with the periosteum
Periosteum
Periosteum is a membrane that lines the outer surface of all bones, except at the joints of long bones. Endosteum lines the inner surface of all bones....

. The posterior sacrococcygeal ligament has a deep and a superficial part, the former is a flat band corresponding to the posterior longitudinal ligament
Posterior longitudinal ligament
The posterior longitudinal ligament is situated within the vertebral canal, and extends along the posterior surfaces of the bodies of the vertebræ, from the body of the axis, where it is continuous with the membrana tectoria, to the sacrum....

 (PLL) and the latter corresponds to the ligamenta flava
Ligamenta flava
The ligamenta flava are ligaments which connect the laminae of adjacent vertebrae, all the way from the axis to the first segment of the sacrum...

. Several other ligaments complete the foramen
Foramen
In anatomy, a foramen is any opening. Foramina inside the body of humans and other animals typically allow muscles, nerves, arteries, veins, or other structures to connect one part of the body with another.-Skull:...

 of the last sacral nerve
Sacral spinal nerve 5
The sacral spinal nerve 5 is a spinal nerve of the sacral segment..It originates from the spinal column from below the 5th body of the sacrum S5 supplies the Coccygeus muscle...

.

Articulations


The lumbosacral joint
Lumbosacral joint
The lumbosacral joint is a joint of the body, between the last lumbar vertebra and the first sacral segment of the spinal cord....

, between the sacrum and the last lumbar vertebra, has, like all vertebal joints, an intervertebral disc
Intervertebral disc
Intervertebral discs lie between adjacent vertebrae in the spine. Each disc forms a cartilaginous joint to allow slight movement of the vertebrae, and acts as a ligament to hold the vertebrae together.-Structure:...

, anterior
Anterior longitudinal ligament
The anterior longitudinal ligament is a ligament that runs down the anterior surface of the spine. It traverses all of the vertebral bodies and intervertebral discs....

 and posterior ligaments
Posterior longitudinal ligament
The posterior longitudinal ligament is situated within the vertebral canal, and extends along the posterior surfaces of the bodies of the vertebræ, from the body of the axis, where it is continuous with the membrana tectoria, to the sacrum....

, ligamenta flava
Ligamenta flava
The ligamenta flava are ligaments which connect the laminae of adjacent vertebrae, all the way from the axis to the first segment of the sacrum...

, interspinous and supraspinous ligament
Supraspinous ligament
The supraspinal ligament is a strong fibrous cord, which connects together the apices of the spinous processes from the seventh cervical vertebra to the sacrum; at the points of attachment to the tips of the spinous processes fibrocartilage is developed in the ligament.It is thicker and broader in...

s, and synovial joints between the articular processes of the two bones. In addition to these ligaments the joint is strengthened by the iliolumbar and lateral lumbosacral ligaments. The iliolumbar ligament passes between the tip of the transverse process of the fifth lumbar vertebra and the posterior part of the iliac crest. The lateral lumbosacral ligament, partly continuous with the iliolumbar ligament, passes down from the lower border of the transverse process of the fifth vertebra to the ala of the sacrum. The movements possible in the lumbosacral joint are flexion and extension, a small amount of lateral flexion (from 7 degrees in childhood to 1 degree in adults), but no axial rotation. Between ages 2–13 the joint is responsible for as much as 75% (about 18 degrees) of flexion and extension in the lumbar spine. From age 35 the ligaments considerably limit the range of motions.
The three extracapsular ligaments of the hip joint — the iliofemoral
Iliofemoral ligament
The iliofemoral ligament is a ligament of the hip joint which extends from the ilium to the femur in front of the joint. It is also referred to as the Y-ligament or the ligament of Bigelow, and any combinations of these names....

, ischiofemoral
Ischiofemoral ligament
The ischiocapsular ligament consists of a triangular band of strong fibers on the posterior side of the hip joint...

, and pubofemoral ligament
Pubofemoral ligament
The pubofemoral ligament is a ligament on the inferior side of the hip joint.This ligament is attached, above, to the obturator crest and the superior ramus of the pubis; below, it blends with the capsule and with the deep surface of the vertical band of the iliofemoral ligament....

s — form a twisting mechanism encircling the neck of the femur. When sitting, with the hip joint flexed, these ligaments become lax permitting a high degree of mobility in the joint. When standing, with the hip joint extended, the ligaments get twisted around the femoral neck, pushing the head of the femur firmly into the acetabulum, thus stabilising the joint.
The zona orbicularis
Zona orbicularis
The zona orbicularis or annular ligament is a ligament on the neck of the femur formed by the circular fibers of the articular capsule of the hip joint...

 assists in maintaining the contact in the joint by acting like a buttonhole on the femoral head. The intracapsular ligament, the ligamentum teres
Ligament of head of femur
The ligament of the head of the femur , or the round ligament of the femur , is a triangular, somewhat flattened band implanted by its apex into the antero-superior part of the fovea capitis femoris; its base is attached by two bands, one into either side of the acetabular notch, and between these...

, transmits blood vessels that nourish the femoral head.

Pelvic cavity

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The pelvic cavity is a body cavity
Body cavity
By the broadest definition, a body cavity is any fluid-filled space in a multicellular organism. However, the term usually refers to the space located between an animal’s outer covering and the outer lining of the gut cavity, where internal organs develop...

 that is bounded by the bones of the pelvis and which primarily contains reproductive organs and the rectum
Rectum
The rectum is the final straight portion of the large intestine in some mammals, and the gut in others, terminating in the anus. The human rectum is about 12 cm long...

.

A distinction is made between the lesser
Lesser pelvis
The lesser pelvis is that part of the space enclosed by the skeleton of the pelvis which is situated between the pelvic inlet and the pelvic floor. Some authors call this cavity the pelvic cavity...

 or true pelvis inferior to the terminal line
Linea terminalis
The linea terminalis or innominate line consists of the pectineal line, the arcuate line, and the sacral promontory.It is part of the pelvic brim, which is the edge of the pelvic inlet. The pelvic inlet is typically used to divide the abdominopelvic cavity into an abdominal and a pelvic cavity...

, and the greater
Greater pelvis
The greater pelvis is a portion of the cavity surrounded by the skeleton of the pelvis, situated above and in front of the pelvic brim...

 or false pelvis above it. The pelvic inlet
Pelvic inlet
The pelvic inlet or superior aperture of the pelvis is a planar surface which is typically used to define the boundary between the pelvic cavity and the abdominal cavity .Its position and orientation relative to the skeleton of the pelvis is anatomically defined by its...

 or superior pelvic aperture, which leads into the lesser pelvis, is bordered by the promontory
Sacral promontory
The sacral promontory is the anatomical term for the superiormost portion of the sacrum. It marks part of the border of the pelvic inlet. The rectosigmoid junction is at the level of the sacral promontory....

, the arcuate line of ilium, the iliopubic eminence, the pecten of the pubis
Pectineal line (pubis)
The pecten pubis or pectineal line of the pubis is a ridge on the superior ramus of the pubic bone.The pecten pubis forms part of the pelvic brim.Lying across it are fibers of the pectineal ligament and the proximal origin of the pectineus muscle....

, and the upper part of the pubic symphysis
Pubic symphysis
The pubic symphysis or symphysis pubis is the midline cartilaginous joint uniting the superior rami of the left and right pubic bones. It is located anterior to the urinary bladder and superior to the external genitalia; for females it is above the vulva and for males it is above the penis...

. The pelvic outlet
Pelvic outlet
The lower circumference of the lesser pelvis is very irregular; the space enclosed by it is named the inferior aperture or pelvic outlet.-Boundaries:It has the following boundaries:* anteriorly: the pubic arch* laterally: the ischial tuberosities...

 or inferior pelvic aperture is the region between the subpubic angle
Subpubic angle
The Subpubic angle is the angle in the human body formed at pubic arch by the convergence of the inferior rami of the ischium and pubis on either side. The subpubic angle is important in forensic anthropology, in determining the sex of someone from skeletal remains...

 or pubic arch
Pubic arch
The eminences of the lower circumference of the true pelvis are separated by three notches: one in front, the pubic arch, formed by the convergence of the inferior rami of the ischium and pubis on either side. The angle at which they converge is known as the subpubic angle.-External links:* *...

, the ischial tuberosities
Tuberosity of the ischium
-External links: - "The Female Perineum: Bones" - "Major Joints of the Lower Extremity: Hip bone "...

 and the coccyx
Coccyx
The coccyx , commonly referred to as the tailbone, is the final segment of the vertebral column. Comprising three to five separate or fused vertebrae below the sacrum, it is attached to the sacrum by a fibrocartilaginous joint, the sacrococcygeal symphysis, which permits limited movement between...

.

  • Ligaments: obturator membrane
    Obturator membrane
    The obturator membrane is a thin fibrous sheet, which almost completely closes the obturator foramen.Its fibers are arranged in interlacing bundles mainly transverse in direction; the uppermost bundle is attached to the obturator tubercles and completes the obturator canal for the passage of the...

    , inguinal ligament
    Inguinal ligament
    The inguinal ligament is a band running from the pubic tubercle to the anterior superior iliac spine. Its anatomy is very important for operating on hernia patients.-Anatomy:...

     (lacunar ligament
    Lacunar ligament
    The lacunar ligament is a ligament in the inguinal region that connects the inguinal ligament to the pectineal ligament near the point where they both insert on the pubic tubercle.-Anatomy:...

    , iliopectineal arch
    Iliopectineal arch
    The Iliopectineal arch is a thickened band of fused iliac fascia and psoas fascia passing from the posterior aspect of the inguinal ligament anteriorly across the front of the femoral nerve to attach to the iliopubic eminence of the hip bone posteriorly...

    )

Development


Each side of the pelvis is formed as cartilage, which ossifies as three main bones which stay separate through childhood: ilium
Ilium (bone)
The ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...

, ischium, pubis
Pubis (bone)
In vertebrates, the pubic bone is the ventral and anterior of the three principal bones composing either half of the pelvis.It is covered by a layer of fat, which is covered by the mons pubis....

. At birth the whole of the hip joint (the acetabulum area and the top of the femur) is still made of cartilage (but there may be a small piece of bone in the great trochanter of the femur); this makes it difficult to detect congenital hip dislocation by X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

ing.

Shoulder and intrinsic back



The inferior parts of latissimus dorsi
Latissimus dorsi muscle
The latissimus dorsi , meaning 'broadest muscle of the back' , is the larger, flat, dorso-lateral muscle on the trunk, posterior to the arm, and partly covered by the trapezius on its median dorsal region.The latissimus dorsi is responsible for extension,...

, one of the muscles of the upper limb, arises from the posterior third of the iliac crest. Its action on the shoulder joint are internal rotation, adduction, and retroversion. It also contributes to respiration (i.e. coughing). When the arm is adducted, latissimus dorsi can pull it backward and medially until the back of the hand covers the buttocks.

In a longitudinal osteofibrous canal on either side of the spine there is a group of muscles called the erector spinae
Erector spinae
The Erector spinæ is a muscle group of the back in humans and animals. It is also known as sacrospinalis in older texts. A more modern term is extensor spinae, though this is not in widespread use. The name of the muscle is pronounced e-rec-tor speen-aye, or e-rec-tor spinae-ee.It is really not...

 which is subdivided into a lateral superficial and a medial deep tract. In the lateral tract, the iliocostalis lumborum and longissimus thoracis originates on the back of the sacrum and the posterior part of the iliac crest. Contracting these muscles bilaterally extends the spine and unilaterally contraction bends the spine to the same side. The medial tract has a "straight" (interspinales, intertransversarii
Intertransversarii muscle
The Intertransversarii are small muscles placed between the transverse processes of the vertebræ.-Cervical:In the cervical region they are best developed, consisting of rounded muscular and tendinous fasciculi, and are placed in pairs, passing between the anterior and the posterior tubercles...

, and spinalis
Spinalis
The spinalis is the portion of the erector spinae, a bundle of muscles and tendons, located nearest to the spine. It is divided into three parts.-Spinalis dorsi:...

) and an "oblique" (multifidus
Multifidus muscle
The multifidus muscle consists of a number of fleshy and tendinous fasciculi, which fill up the groove on either side of the spinous processes of the vertebrae, from the sacrum to the axis...

 and semispinalis
Semispinalis muscle
The semispinalis muscle is a transversospinalis muscle of the human body. More specifically, it is one of three muscles:* Semispinalis dorsi* Semispinalis cervicis* Semispinalis capitis...

) component, both of which stretch between vertebral processes; the former acts similar to the muscles of the lateral tract, while the latter function unilaterally as spine extensors and bilaterally as spine rotators. In the medial tract, the multifidi originates on the sacrum
Sacrum
In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...

.

Abdomen


The muscles of the abdominal wall are subdivided into a superficial and a deep group.

The superficial group is subdivided into a lateral and a medial group. In the medial superficial group, on both sides of the centre of the abdominal wall (the linea alba), the rectus abdominis
Rectus abdominis muscle
The rectus abdominis muscle, also known as the "six pack", is a paired muscle running vertically on each side of the anterior wall of the human abdomen . There are two parallel muscles, separated by a midline band of connective tissue called the linea alba...

 stretches from the cartilages of ribs V-VII and the sternum down to the pubic crest
Pubic crest
Medial to the pubic tubercle is the pubic crest, which extends from this process to the medial end of the bone.It affords attachment to the inguinal falx, and to the External Abdominal Oblique and Pyramidalis....

. At the lower end of the rectus abdominis, the pyramidalis
Pyramidalis muscle
The pyramidalis is a small and triangular muscle, anterior to the Rectus abdominis, and contained in the rectus sheath.-Attachments and actions:...

 tenses the linea alba. The lateral superficial muscles, the transversus
Transversus abdominis muscle
The transversus abdominis muscle, also known as the transverse abdominus, transversalis muscle and transverse abdominal muscle, is a muscle layer of the anterior and lateral abdominal wall which is deep to the internal oblique muscle...

 and external and internal oblique muscles, originate on the rib cage and on the pelvis (iliac crest and inguinal ligament
Inguinal ligament
The inguinal ligament is a band running from the pubic tubercle to the anterior superior iliac spine. Its anatomy is very important for operating on hernia patients.-Anatomy:...

) and are attached to the anterior and posterior layers of the sheath
Rectus sheath
The Rectus sheath is formed by the aponeuroses of the Obliqui and Transversus. It contains the Rectus abdominis and Pyramidalis muscles.It can be divided into anterior and posterior laminae....

 of the rectus.
Flexing the trunk (bending forward) is essentially a movement of the rectus muscles, while lateral flexion (bending sideways) is achieved by contracting the obliques together with the quadratus lumborum and intrinsic back muscles. Lateral rotation (rotating either the trunk or the pelvis sideways) is achieved by contracting the internal oblique on one side and the external oblique on the other. The transversus' main function is to produce abdominal pressure in order to constrict the abdominal cavity and pull the diaphragm upward.
There are two muscles in the deep or posterior group. Quadratus lumborum
Quadratus lumborum muscle
The Quadratus lumborum is irregular and quadrilateral in shape, and broader below than above.-Origin and insertion:It arises by aponeurotic fibers from the iliolumbar ligament and the adjacent portion of the iliac crest for about 5 cm., and is inserted into the lower border of the last rib for...

 arises from the posterior part of the iliac crest and extends to the rib XII and lumbar vertebrae I-IV. It unilaterally bends the trunk to the side and bilaterally pulls the 12th rib down and assists in expiration. The iliopsoas consists of psoas major
Psoas major muscle
-External links: - "Posterior Abdominal Wall: Muscles of the Posterior Abdominal Wall"* *...

 (and occasionally psoas minor
Psoas minor muscle
The psoas minor is a long, slender skeletal muscle which, when present, is located in front of the psoas major muscle. This muscle does not exist in about half the human population.-Course:...

) and iliacus
Iliacus muscle
The iliacus is a flat, triangular muscle which fills the iliac fossa.- Course :The iliacus arises from the iliac fossa on the interior side of the hip bone, and also from the region of the anterior inferior iliac spine...

, muscles with separate origins but a common insertion on the lesser trochanter
Lesser trochanter
The lesser trochanter of the femur is a conical eminence, which varies in size in different subjects-Anatomy:It projects from the lower and back part of the base of the femur neck.From its apex three well-marked borders extend:...

 of the femur. Of these, only iliacus is attached to the pelvis (the iliac fossa
Iliac fossa
The iliac fossa is a large, smooth, concave surface located on the internal surface of the ilium...

). However, psoas passes through the pelvis and because it acts on two joints, it is topographically classified as a posterior abdominal muscle but functionally as a hip muscle. Iliopsoas flexes and externally rotates the hip joints, while unilateral contraction bends the trunk laterally and bilateral contraction raises the trunk from the supine position
Supine position
The supine position is a position of the body: lying down with the face up, as opposed to the prone position, which is face down, sometimes with the hands behind the head or neck. When used in surgical procedures, it allows access to the peritoneal, thoracic and pericardial regions; as well as the...

.

Pelvic floor



The pelvic floor
Pelvic floor
The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed by the levatores ani and coccygei, with which may be included the...

 has two inherently conflicting functions: One is to close the pelvic and abdominal cavities and bear the load of the visceral organs, the other is to control the openings of the rectum
Rectum
The rectum is the final straight portion of the large intestine in some mammals, and the gut in others, terminating in the anus. The human rectum is about 12 cm long...

 and urogenital organs that pierce the pelvic floor and make it weaker. To achieve both these tasks, the pelvic floor is composed of several overlapping sheets of muscles and connective tissues.
The pelvic diaphragm is composed of the levator ani
Levator ani
The levator ani is a broad, thin muscle, situated on the side of the pelvis.It is attached to the inner surface of the side of the lesser pelvis, and unites with its fellow of the opposite side to form the greater part of the floor of the pelvic cavity....

 and the coccygeus muscle
Coccygeus muscle
The Coccygeus is a muscle of the pelvic wall , located posterior to levator ani and anterior to the sacrospinous ligament....

. These arises between the symphysis and the ischial spine and converges on the coccyx and the anococcygeal ligament which spans between the tip of the coccyx and the anal hiatus. This leaves a slit for the anal and urogenital openings. Because of the width of the genital aperture, which is wider in females, a second closing mechanism is required. The urogenital diaphragm
Urogenital diaphragm
Older texts have asserted the existence of an urogenital diaphragm, also called the triangular ligament, which was described as a layer of the pelvis that separates the deep perineal sac from the upper pelvis, lying between the inferior fascia of the urogenital diaphragm and superior fascia of the...

 consists mainly of the deep transverse perineal which arises from the inferior ischial
Inferior ramus of the ischium
The Inferior Ramus of the ischium is the thin, flattened part of the ischium, which ascends from the superior ramus, and joins the inferior ramus of the pubis—the junction being indicated in the adult by a raised line....

 and pubic rami
Inferior pubic ramus
The inferior pubic ramus is a part of the pelvis and is thin and flat. It passes laterally and downward from the medial end of the superior ramus; it becomes narrower as it descends and joins with the inferior ramus of the ischium below the obturator foramen....

 and extends to the urogential hiatus. The urogenital diaphragm is reinforced posteriorly by the superficial transverse perineal.
The external anal
Sphincter ani externus muscle
The Sphincter ani externus is a flat plane of muscular fibers, elliptical in shape and intimately adherent to the integument surrounding the margin of the anus.-Anatomy:...

 and urethral sphincter
Urethral sphincter
The term urethral sphincter refers to one of two muscles used to control the exit of urine in the urinary bladder through the urethra. The two muscles are the external urethral sphincter and the internal urethral sphincter...

s close the anus and the urethra. The former is surrounded by the bulbospongiosus
Bulbospongiosus muscle
Bulbospongiosus is one of the superficial muscles of the perineum. It has a slightly different origin, insertion and function in males and females. In males, it covers the bulb of the penis...

 which narrows the vaginal introitus in females and surrounds the corpus spongiosum in males. Ischiocavernosus
Ischiocavernosus muscle
The ischiocavernosus muscle is a muscle just below the surface of the perineum, present in both men and women.-Function:It helps flex the anus, and stabilize the erect penis or tense the vagina during orgasm...

 squeezes blood into the corpus cavernosum penis
Corpus cavernosum penis
The corpus cavernosum penis is one of a pair of sponge-like regions of erectile tissue which contain most of the blood in the penis during penile erection...

 and clitoridis
Corpus cavernosum clitoridis
The corpus cavernosum clitoridis is one of a pair of sponge-like regions of erectile tissue which contain most of the blood in the clitoris during clitoral erection...

.

Hip and thigh

Muscles of the hip


The muscles of the hip are divided into a dorsal and a ventral group.

The dorsal hip muscles are either inserted into the region of the lesser trochanter
Lesser trochanter
The lesser trochanter of the femur is a conical eminence, which varies in size in different subjects-Anatomy:It projects from the lower and back part of the base of the femur neck.From its apex three well-marked borders extend:...

 (anterior or inner group) or the greater trochanter
Greater trochanter
The greater trochanter of the femur is a large, irregular, quadrilateral eminence and a part of the skeletal system.It is directed a little lateralward and backward, and, in the adult, is about 1 cm lower than the head...

 (posterior or outer group). Anteriorly, the psoas major
Psoas major muscle
-External links: - "Posterior Abdominal Wall: Muscles of the Posterior Abdominal Wall"* *...

 (and occasionally psoas minor
Psoas minor muscle
The psoas minor is a long, slender skeletal muscle which, when present, is located in front of the psoas major muscle. This muscle does not exist in about half the human population.-Course:...

) originates along the spine between the rib cage and pelvis. The iliacus
Iliacus muscle
The iliacus is a flat, triangular muscle which fills the iliac fossa.- Course :The iliacus arises from the iliac fossa on the interior side of the hip bone, and also from the region of the anterior inferior iliac spine...

 originates on the iliac fossa
Iliac fossa
The iliac fossa is a large, smooth, concave surface located on the internal surface of the ilium...

 to join psoas at the iliopubic eminence to form the iliopsoas
Iliopsoas
-External links:*...

 which is inserted into the lesser trochanter.

The iliopsoas is the most powerful hip flexor.

The posterior group includes the gluteii maximus, medius, and minimus. Maximus has a wide origin stretching from the posterior part of the iliac crest and along the sacrum and coccyx, and has two separate insertions: a proximal which radiates into the iliotibial tract
Iliotibial tract
The iliotibial tract or iliotibial band is a longitudinal fibrous reinforcement of the fascia lata. It is attached to the anterolateral iliac tubercle portion of the external lip of the iliac crest and to the lateral condyle of the tibia...

 and a distal which inserts into the gluteal tuberosity
Gluteal tuberosity
The lateral ridge of the linea aspera is very rough, and runs almost vertically upward to the base of the greater trochanter. It is termed the gluteal tuberosity, and gives attachment to part of the Glutæus maximus: its upper part is often elongated into a roughened crest, on which a more or less...

 on the posterior side of the femoral shaft. It is primarily an extensor and lateral rotator of the hip joint, but, because of its bipartite insertion, it can both adduct and abduct the hip. Medius and minimus arise on the external surface of the ilium and are both inserted into the greater trochanter. Their anterior fibers are medial rotators and flexors while the posterior fibers are lateral rotators and extensors. The piriformis
Piriformis muscle
The piriformis is a muscle in the gluteal region of the lower limb. It was first named by Spigelius, a professor from the University of Padua in the 16th century.- Origin and insertion :...

 has its origin on the ventral side of the sacrum and is inserted on the greater trochanter. It abducts and laterally rotates the hip in the upright posture and assists in extension of the thigh.
The tensor fasciae latae
Tensor fasciae latae
The tensor fasciae latae or tensor fasciæ latæ is a muscle of the thigh. The English name for this muscle is the muscle that stretches the band on the side...

 arises on the anterior superior iliac spine and inserts into the iliotibial tract. It presses the head of the femur
Femur head
The femur head is the highest part of the thigh bone . It is supported by the neck of the femur.The head is globular and forms rather more than a hemisphere, is directed upward, medialward, and a little forward, the greater part of its convexity being above and in front.Its surface is smooth,...

 into the acetabulum
Acetabulum
The acetabulum is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint.-Structure:...

 and flexes, medially rotates, and abducts the hip.

The ventral hip muscles are important in the control of the body's balance. The internal
Obturator internus muscle
The obturator internus muscle originates on the medial surface of the obturator membrane, the ischium near the membrane, and the rim of the pubis.It exits the pelvic cavity through the lesser sciatic foramen....

 and external obturator muscles
Obturator externus muscle
The obturator externus muscle is a flat, triangular muscle, which covers the outer surface of the anterior wall of the pelvis.It is sometimes considered part of the medial compartment of thigh, and sometimes considered part of the gluteal region....

 together with the quadratus femoris
Quadratus femoris muscle
The quadratus femoris is a flat, quadrilateral skeletal muscle. Located on the posterior side of the hip joint, it is a strong external rotator and adductor of the thigh, but also acts to stabilize the femoral head in the Acetabulum.- Course :...

 are lateral rotators of the hip. Together they are stronger than the medial rotators and therefore the feet point outward in the normal position to achieve a better support. The obturators have their origins on either sides of the obturator foramen
Obturator foramen
The obturator foramen is the hole created by the ischium and pubis bones of the pelvis through which nerves and muscles pass.- General structure :...

 and are inserted into the trochanteric fossa on the femur. Quadratus arises on the ischial tuberosity and is inserted into the intertrochanteric crest
Intertrochanteric crest
The intertrochanteric crest is a bony ridge located on the posterior side of the head of the femur, stretching obliquely downward and medially from the summit of the greater trochanter to the lesser trochanter....

. The superior
Superior gemellus muscle
The superior gemellus muscle is a muscle of the human body.The Gemelli are two small muscular fasciculi, accessories to the tendon of the Obturator internus which is received into a groove between them....

 and inferior gemelli
Inferior gemellus muscle
The inferior gemellus muscle is a muscle of the human body.The Gemelli are two small muscular fasciculi, accessories to the tendon of the Obturator internus which is received into a groove between them....

, arising from the ischial spine and ischial tuberosity respectively, can be thought of as marginal heads of the obturator internus, and their main function is to assist this muscle.
The muscles of the thigh
Thigh
In humans the thigh is the area between the pelvis and the knee. Anatomically, it is part of the lower limb.The single bone in the thigh is called the femur...

 can be subdivided into adductors (medial group), extensors (anterior group), and flexors (posterior group). The extensors and flexors act on the knee joint, while the adductors mainly act on the hip joint.

The thigh adductors have their origins on the inferior ramus of the pubic bone
Inferior pubic ramus
The inferior pubic ramus is a part of the pelvis and is thin and flat. It passes laterally and downward from the medial end of the superior ramus; it becomes narrower as it descends and joins with the inferior ramus of the ischium below the obturator foramen....

 and are, with the exception of gracilis
Gracilis muscle
The gracilis is the most superficial muscle on the medial side of the thigh. It is thin and flattened, broad above, narrow and tapering below.-Origin and insertion:...

, inserted along the femoral shaft. Together with sartorius
Sartorius muscle
The Sartorius muscle – the longest muscle in the human body – is a long thin muscle that runs down the length of the thigh. Its upper portion forms the lateral border of the femoral triangle.-Origin and insertion:...

 and semitendinosus
Semitendinosus muscle
The semitendinosus is a muscle in the back of the thigh; it is one of the hamstrings.-Structure:The semitendinosus, remarkable for the great length of its tendon of insertion, is situated at the posterior and medial aspect of the thigh ....

, gracilis reaches beyond the knee to their common insertion on the tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....

.

The anterior thigh muscles form the quadriceps which is inserted on the patella with a common tendon. Three of the four muscles have their origins on the femur, while rectus femoris
Rectus femoris muscle
The rectus femoris muscle is one of the four quadriceps muscles of the human body. The others are the vastus medialis, the vastus intermedius , and the vastus lateralis...

 arises from the anterior inferior iliac spine and is thus the only of the four acting on two joints.

The posterior thigh muscles have their origins on the inferior ischial ramus
Inferior ramus of the ischium
The Inferior Ramus of the ischium is the thin, flattened part of the ischium, which ascends from the superior ramus, and joins the inferior ramus of the pubis—the junction being indicated in the adult by a raised line....

, with the exception of the short head of the biceps femoris
Biceps femoris muscle
The biceps femoris is a muscle of the posterior thigh. As its name implies, it has two parts, one of which forms part of the hamstrings muscle group.-Origin and insertion:It has two heads of origin;...

. The semitendinosus
Semitendinosus muscle
The semitendinosus is a muscle in the back of the thigh; it is one of the hamstrings.-Structure:The semitendinosus, remarkable for the great length of its tendon of insertion, is situated at the posterior and medial aspect of the thigh ....

 and semimembranosus
Semimembranosus muscle
The semimembranosus is a muscle in the back of the thigh. It is the most medial of the three hamstring muscles.-Structure:The semimembranosus, so called from its membranous tendon of origin, is situated at the back and medial side of the thigh....

 are inserted on the tibia on the medial side of the knee, while biceps femoris is inserted on the fibula, on the knee's lateral side.

Pregnancy and childbirth


In later stages of pregnancy
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...

 the fetus
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

's head aligns inside the pelvis. Also joints of bones soften due to the effect of pregnancy hormones. These factors may cause pelvic joint pain (Symphysis Pubis Dysfunction
Symphysis pubis dysfunction
Symphysis Pubis Dysfunction is most commonly associated with pregnancy and childbirth. It is a condition that causes excessive movement of the pubic symphysis, either anterior or lateral, as well as associated pain, possibly because of a misalignment of the pelvis. SPD is a dysfunction that is...

 or SPD). As the end of pregnancy approaches, the ligaments of the sacroiliac joint loosen, letting the pelvis outlet widen somewhat; this is easily noticeable in the cow.

During childbirth
Childbirth
Childbirth is the culmination of a human pregnancy or gestation period with the birth of one or more newborn infants from a woman's uterus...

 (unless by Cesarean section) the fetus passes through the maternal pelvic opening.

Sexual dimorphism


Modern humans are to a large extent characterized by bipedal locomotion and large brains
Human brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...

. Because the pelvis is vital to both locomotion and childbirth, natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

 has been confronted by two conflicting demands: a wide birth canal and locomotion efficiency, a conflict referred to as the "obstetrical dilemma
Obstetrical Dilemma
The Obstetrical Dilemma refers to the evolutionary development of the human species through a number of biological changes, specifically the shifting of the females' pelvic bones, thereby shortening the fetal incubation period....

". The female pelvis has evolved to its maximum width for childbirth — a wider pelvis would make women unable to walk. In contrast, human male pelves are not constrained by the need to give birth and therefore are optimized for bipedal locomotion.
The principal differences between male and female true and false pelvis include:
  • The female pelvis is larger and broader than the male pelvis which is taller, narrower, and more compact.
  • The female inlet is larger and oval in shape, while the male sacral promontory
    Sacral promontory
    The sacral promontory is the anatomical term for the superiormost portion of the sacrum. It marks part of the border of the pelvic inlet. The rectosigmoid junction is at the level of the sacral promontory....

     projects further (i.e. the male inlet is more heart-shaped).
  • The sides of the male pelvis converge from the inlet to the outlet, whereas the sides of the female pelvis are wider apart.
  • The angle between the inferior pubic rami
    Inferior pubic ramus
    The inferior pubic ramus is a part of the pelvis and is thin and flat. It passes laterally and downward from the medial end of the superior ramus; it becomes narrower as it descends and joins with the inferior ramus of the ischium below the obturator foramen....

     is acute (70 degrees) in men, but obtuse (90-100 degrees) in women. Accordingly, the angle is called subpubic angle
    Subpubic angle
    The Subpubic angle is the angle in the human body formed at pubic arch by the convergence of the inferior rami of the ischium and pubis on either side. The subpubic angle is important in forensic anthropology, in determining the sex of someone from skeletal remains...

     in men and pubic arch
    Pubic arch
    The eminences of the lower circumference of the true pelvis are separated by three notches: one in front, the pubic arch, formed by the convergence of the inferior rami of the ischium and pubis on either side. The angle at which they converge is known as the subpubic angle.-External links:* *...

     in women. Additionally, the bones forming the angle/arch are more concave in females but straight in males.
  • The distance between the ischia bones is small in males, making the outlet narrow, but large in females, who have a relatively large outlet. The ischial spines and tuberosities are heavier and project farther into the pelvic cavity in males. The greater sciatic notch is wider in females.
  • The iliac crests are higher and more pronounced in males, making the male false pelvis deeper and more narrow than in females.
  • The male sacrum is long, narrow, more straight, and has a pronounced sacral promontory. The female sacrum is shorter, wider, more curved posteriorly, and has a less pronounced promontory.
  • The acetabula are wider apart in females than in males. In males, the acetabulum faces more laterally, while it faces more anteriorly in females. Consequently, when men walk the leg can move forwards and backwards in a single plane. In women, the leg must swing forward and inward, from where the pivoting head of the femur moves the leg back in another plane. This change in the angle of the femoral head gives the female gait its characteristic (i.e. swinging of hips).

Caldwell-Moloy classification


Throughout the 20th century pelvimetric
Pelvimetry
Pelvimetry is the assessment of the female pelvis in relation to the birth of a baby. Traditional obstetrical services relied heavily on pelvimetry in the conduct of delivery in order to decide if natural or operative vaginal delivery was possible or if and when to use a cesarean...

 measurements were made on pregnant women to determine whether a natural birth would be possible, a practice today limited to cases where a specific problem is suspected or following a caesarean delivery. William Edgar Caldwell and Howard Carmen Moloy studied collections of skeletal pelves and thousands of stereoscopic radiograms and finally recognized three types of female pelves plus the masculine type. In 1933 and 1934 they published their typology, including the Greek names since then frequently quoted in various handbooks: Gynaecoid (gyne, woman), anthropoid (anthropos, human being), platypelloid (platys, flat), and android (aner, man).

  • The gynaecoid pelvis is the so-called normal female pelvis. Its inlet is either slightly oval, with a greater transverse diameter, or round. The interior walls are straight, the subpubic arch wide, the sacrum shows an average to backward inclination, and the greater sciatic notch is well rounded. Because this type is spacious and well proportioned there is little or no difficulty in the birth process. Caldwell and his co-workers found gynaecoid pelves in about 50 per cent of specimens.
  • The platypelloid pelvis has a transversally wide, flattened shape, is wide anteriorly, greater sciatic notches of male type, and has a short sacrum that curves inwards reducing the diameters of the lower pelvis. This is similar to the rachitic
    Rickets
    Rickets is a softening of bones in children due to deficiency or impaired metabolism of vitamin D, magnesium , phosphorus or calcium, potentially leading to fractures and deformity. Rickets is among the most frequent childhood diseases in many developing countries...

     pelvis where the softened bones widen laterally because of the weight from the upper body resulting in a reduced anteroposterior diameter. Giving birth with this type of pelvis is associated with problems, such as transverse arrest. Less than 3 per cent of women have this pelvis type.
  • The android pelvis is a female pelvis with masculine features, including a wedge or heart shaped inlet caused by a prominent sacrum and a triangular anterior segment. The reduced pelvis outlet often causes problems during child birth. In 1939 Caldwell found this type in one third of white women and in one sixth of non-white women.
  • The anthropoid pelvis is characterized by an oval shape with a greater anteroposterior diameter. It has straight walls, a small subpubic arch, and large sacrosciatic notches. The sciatic spines are placed widely apart and the sacrum is usually straight resulting in deep non-obstructed pelvis. Caldwell found this type in one quarter of white women and almost half of non-white women.

However, Caldwell and Moloy then complicated this simple fourfold scheme by dividing the pelvic inlet into posterior and anterior segments. They named a pelvis according to the anterior segment and affixed another type according to the character of the posterior segment (i.e. anthropoid-android) and ended up with no less than 14 morphologies. Notwithstanding the popularity of this simple classification, the pelvis is much more complicated than this as the pelvis can have different dimensions at various levels of the birth canal.

Caldwell and Moloy also classified the physique of women
Female body shape
Female body shape or figure is the cumulative product of a woman's skeletal structure and the quantity and distribution of muscle and fat on the body. There are, and have been, wide differences on what should be considered an ideal or preferred body shape, both for attractiveness and for health...

 according to their types of pelves: the gynaecoid type has small shoulders, a small waist and wide hips; the android type looks square-shaped from behind; and the anthropoid type has wide shoulders and narrow hips. Lastly, in their article they described all non-gynaecoid or "mixed" types of pelves as "abnormal", a word which has stuck in the medical world even though at least 50 per cent of women have these "abnormal" pelves.

The classification of Caldwell and Moloy was influenced by earlier classifications attempting to define the ideal female pelvis, treating any deviations from this ideal as dysfunctions and the cause of obstructed labour. In the 19th century anthropologists and others saw an evolutionary scheme in these pelvic typologies, a scheme since then refuted by archaeology. Since the 1950s malnutrition
Malnutrition
Malnutrition is the condition that results from taking an unbalanced diet in which certain nutrients are lacking, in excess , or in the wrong proportions....

 is thought to be one of the chief factors affecting pelvic shape in the Third World
Third World
The term Third World arose during the Cold War to define countries that remained non-aligned with either capitalism and NATO , or communism and the Soviet Union...

 even though there are at least some genetic component to variation in pelvic morphology.
Nowadays obstetric suitability of the female pelvis is assessed by ultrasound
Obstetric ultrasonography
Obstetric sonography is the application of medical ultrasonography to obstetrics, in which sonography is used to visualize the embryo or foetus in its mother's uterus...

. The dimensions of the head of the fetus and of the birth canal are accurately measured and compared, and the feasibility of labor can be predicted.

Evolution


The shape of the pelvis, most notably the orientation of the iliac crests and shape and depth of the acetabula, reflects the style of locomotion and body mass of an animal. In bipedal mammals, the iliac crests are parallel to the vertically oriented sacroiliac joints, where in quadrupedal mammals they are parallel to the horizontally oriented sacroiliac joints. In heavy mammals, especially in quadrupeds, the pelvis tend to be more vertically oriented because this allows the pelvis to support greater weight without dislocating the sacroiliac joints or adding torsion to the vertebral column. In ambulatory mammals the acetabula are shallow and open to allow a wider range of hip movements, including significant abduction, than in cursorial mammals. The lengths of the ilium and ischium and their angles relative to the acetabulum are functionally important as they determine the moment arms for the hip extensor muscles that provide momentum during locomotion.

See also

  • Bone terminology
  • Chronic pelvic pain
  • Coccygeal plexus
    Coccygeal plexus
    The coccygeal plexus is a plexus of nerves near the coccyx bone.-Structure:This plexus is formed by the fifth sacral nerve and the coccygeal nerve...

  • Coccyx (tailbone)
    Coccyx
    The coccyx , commonly referred to as the tailbone, is the final segment of the vertebral column. Comprising three to five separate or fused vertebrae below the sacrum, it is attached to the sacrum by a fibrocartilaginous joint, the sacrococcygeal symphysis, which permits limited movement between...

  • Hip fracture
    Hip fracture
    A hip fracture is a femoral fracture that occurs in the proximal end of the femur , near the hip.The term "hip fracture" is commonly used to refer to four different fracture patterns and is often due to osteoporosis; in the vast majority of cases, a hip fracture is a fragility fracture due to a...

  • Pelvic fracture
    Pelvic fracture
    Pelvic fracture is a disruption of the bony structure of the pelvis, including the hip bone, sacrum and coccyx. The most common cause in elderly is a fall, but the most significant fractures involve high-energy forces such as a motor vehicle accident, cycling accidents, or a fall from significant...

  • Pelvimetry
    Pelvimetry
    Pelvimetry is the assessment of the female pelvis in relation to the birth of a baby. Traditional obstetrical services relied heavily on pelvimetry in the conduct of delivery in order to decide if natural or operative vaginal delivery was possible or if and when to use a cesarean...

  • Pelvis justo major
  • Pubic symphysis
    Pubic symphysis
    The pubic symphysis or symphysis pubis is the midline cartilaginous joint uniting the superior rami of the left and right pubic bones. It is located anterior to the urinary bladder and superior to the external genitalia; for females it is above the vulva and for males it is above the penis...

  • Renal pelvis
    Renal pelvis
    The renal pelvis or pyelum is the funnel-like dilated proximal part of the ureter in the kidney.In humans, the renal pelvis is the point of convergence of two or three major calyces...

  • Sacroiliac joint
    Sacroiliac joint
    The sacroiliac joint or SI joint is the joint in the bony pelvis between the sacrum and the ilium of the pelvis, which are joined together by strong ligaments. In humans, the sacrum supports the spine and is supported in turn by an ilium on each side...

  • Terms for anatomical location

External links