Pelvic cavity
Encyclopedia
The pelvic cavity is a body cavity
that is bounded by the bones of the pelvis
. Its oblique roof is the pelvic inlet
(the superior opening of the pelvis). Its lower boundary is the pelvic floor
.
The pelvic cavity primarily contains reproductive organs, the urinary bladder
, the pelvic colon, and the rectum
. The rectum
is placed at the back of the pelvis, in the curve of the sacrum
and coccyx
; the bladder is in front, behind the pubic symphysis
.
In the female, the uterus
and vagina
occupy the interval between these viscera. The pelvic cavity also contains major arteries, veins, muscles, and nerves. These structures have to work together in a little crowded space. They can be affected by many different diseases and by many drugs in many different ways. One part may impact upon another, for example constipation may overload the rectum and compress the urinary bladder, or childbirth might damage the pudendal nerves
and later lead to anal weakness.
(or "true" pelvis) only includes structures inferior to the pelvic brim
.
For example, the pelvic splanchnic nerves
arising at S2-S4 is in the true pelvis, but the femoral nerve
from L2-L4 is only in the "false pelvis", or greater pelvis
.
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
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
. Its oblique roof is 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...
(the superior opening of the pelvis). Its lower boundary is 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...
.
The pelvic cavity primarily contains reproductive organs, the urinary bladder
Urinary bladder
The urinary bladder is the organ that collects urine excreted by the kidneys before disposal by urination. A hollow muscular, and distensible organ, the bladder sits on the pelvic floor...
, the pelvic colon, 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...
. 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...
is placed at the back of the pelvis, in the curve of 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 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 bladder is in front, behind 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...
.
In the female, the uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
and vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...
occupy the interval between these viscera. The pelvic cavity also contains major arteries, veins, muscles, and nerves. These structures have to work together in a little crowded space. They can be affected by many different diseases and by many drugs in many different ways. One part may impact upon another, for example constipation may overload the rectum and compress the urinary bladder, or childbirth might damage the pudendal nerves
Pudendal nerve
The pudendal nerve is a sensory and somatic nerve in the pelvic region which is a large branch of the sacral plexus that innervates the external genitalia of both sexes, as well as sphincters for the bladder and the rectum...
and later lead to anal weakness.
Borders
The boundaries are as follows:| roof: 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.... |
>- | lateral: obturator internus | 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... >- | |
floor: 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... |
Greater and lesser pelvis
The lesser pelvisLesser 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) only includes structures inferior to 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....
.
For example, the pelvic splanchnic nerves
Pelvic splanchnic nerves
Pelvic splanchnic nerves or nervi erigentes are splanchnic nerves that arise from sacral spinal nerves S2, S3, S4 to provide parasympathetic innervation to the hindgut.-Structure:...
arising at S2-S4 is in the true pelvis, but the femoral nerve
Femoral nerve
The femoral nerve, the largest branch of the lumbar plexus, arises from the dorsal divisions of the ventral rami of the second, third, and fourth lumbar nerves...
from L2-L4 is only in the "false pelvis", or greater pelvis
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...
.
Ligaments
| Ligament | From | To >- | broad ligament of the uterus Broad ligament of the uterus The broad ligament of the uterus is the wide fold of peritoneum that connects the sides of the uterus to the walls and floor of the pelvis.-Subdivisions:The broad ligament may be divided into three subcomponents:... |
>- | ovary Ovary The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries... |
>- | Fallopian tube Fallopian tube The Fallopian tubes, also known as oviducts, uterine tubes, and salpinges are two very fine tubes lined with ciliated epithelia, leading from the ovaries of female mammals into the uterus, via the utero-tubal junction... |
>- | >- | >- | ovary | >- | >- |
Measurements
The pelvis can be classified into four main types by measuring the pelvic diameters and conjugates at the pelvic inlet and outlet and as oblique diameters.| Measurement | From | To | Length |
|---|---|---|---|
| Transverse diameter (of inlet) |
Between extreme lateral points of pelvic inlet | 13.5-14 cm | |
| Oblique diameter I | Right sacroiliac joint | Left iliopubic eminence | 12-12.5 cm |
| Oblique diameter II | Left sacroiliac joint | Right iliopubic eminence | 11.5-12 cm |
| Anatomical conjugate | Pubic symphysis | Promontory | ~12 cm |
| True conjugate (obsteric conjugate) |
Retropubic eminence (posterior surface of symphysis) |
Promontory | 11.5 cm |
| Diagonal conjugate* | Inferior pubic ligament | Promontory | 13 cm |
| Straight conjugate | Lower border of symphysis | Tip of coccyx | 9.5-10 cm |
| Median conjugate | Lower border of symphysis | Lower border of sacrum | 11.5 cm |
| Transverse diameter (of outlet) |
Between ischial tuberosities | 10-11 cm | |
| Interspinous distance | Between anterior superior iliac spines | 26 cm (female) |
|
| Intercristal distance | Between furthest lateral points of iliac crest | 29 cm (female) |
|
| External conjugate | Spinous process of fifth lumbar vertebra | Upper edge of symphysis | ~20 cm |
| Intertrochanteric distance | Between femurs | 31 cm | |
| *Because the true conjugate can not be measured directly it is derived from the diagonal conjugate which is measured through the vagina. | |||
