Levator ani
Encyclopedia
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.
It supports the viscera in pelvic cavity, and surrounds the various structures which pass through it.
In combination with the coccygeus muscle
, it forms the pelvic diaphragm.
lateral to the symphysis
; behind, from the inner surface of the spine of the ischium; and between these two points, from the obturator fascia.
Posteriorly, this fascial origin corresponds, more or less closely, with the tendinous arch of the pelvic fascia, but in front, the muscle arises from the fascia at a varying distance above the arch, in some cases reaching nearly as high as the canal for the obturator vessels and nerve.
The fibers pass downward and backward to the middle line of the floor of the pelvis; the most posterior are inserted into the side of the last two segments of the coccyx
; those placed more anteriorly unite with the muscle of the opposite side, in a median fibrous raphé (anococcygeal raphé), which extends between the coccyx and the margin of the anus
.
The middle fibers are inserted into the side of the rectum
, blending with the fibers of the Sphincter muscles; lastly, the anterior fibers descend upon the side of the prostate to unite beneath it with the muscle of the opposite side, joining with the fibers of the sphincter ani externus
and transversus perinei
, at the central tendinous point of the perineum
.
The anterior portion is occasionally separated from the rest of the muscle by connective tissue.
From this circumstance, as well as from its peculiar relation with the prostate
, which it supports as in a sling, it has been described as a distinct muscle, under the name of Levator prostatæ.
In the female the anterior fibers of the Levator ani descend upon the side of the vagina
.
, perineal nerve
and inferior rectal nerve in concert. In addition, sacral spinal nerves (S3
, S4
) innervate the muscles directly as well (in ~70% of people). Sometimes (in ~40% of people) the inferior rectal nerve innervates the levator ani muscles independently of the pudendal nerve.
pain, caused by spasm of the levator ani muscle. The etiology
is unknown.
Symptom
s include a dull ache to the left 2 inches above the Anus or higher in the rectum and a feeling of constant rectal pressure or burning. The pain may also be felt in the low pelvis
or perineum
.
The discomfort may be relieved by walking or pelvic tightening exercises similar to Kegel exercise
s. Other treatments include massage
of the muscle, warm baths, muscle relaxant
medications, therapeutic ultrasound
and biofeedback
. Electrical stimulation of the levator ani muscle has been used to try to break the spastic cycle. Injection of botulinum toxin A
has also been used.
Variants of levator ani syndrome include proctalgia fugax
(fleeting pain in the rectum) and coccydynia
(pain in the coccygeal
region). Proctalgia fugax and levator ani syndrome have not been found to be of psychosomatic origin, although stressful events may trigger attacks.
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
, situated on the side 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:...
.
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.
It supports the viscera in pelvic cavity, and surrounds the various structures which pass through it.
In combination with 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....
, it forms the pelvic diaphragm.
Parts
The levator ani is divided into three parts:- Iliococcygeus muscleIliococcygeus muscleThe Iliococcygeus arises from the inner side of the ischium and from the posterior part of the tendinous arch of the obturator fascia, and is attached to the coccyx and anococcygeal raphé; it is usually thin, and may fail entirely, or be largely replaced by fibrous tissue...
- Pubococcygeus musclePubococcygeus muscleThe pubococcygeus muscle or PC muscle is a hammock-like muscle, found in both sexes, that stretches from the pubic bone to the coccyx forming the floor of the pelvic cavity and supporting the pelvic organs. It is part of the levator ani group of muscles.-Function:The Pubococcygeus muscle controls...
- Puborectalis musclePuborectalis muscleThe fibers which form a sling for the rectum are named the Puborectalis or Sphincter recti.They arise from the lower part of the pubic symphysis, and from the superior fascia of the urogenital diaphragm....
Origin and insertion of fibers
The levator ani arises, in front, from the posterior surface of the superior ramus of the pubisPubis (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....
lateral to the 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...
; behind, from the inner surface of the spine of the ischium; and between these two points, from the obturator fascia.
Posteriorly, this fascial origin corresponds, more or less closely, with the tendinous arch of the pelvic fascia, but in front, the muscle arises from the fascia at a varying distance above the arch, in some cases reaching nearly as high as the canal for the obturator vessels and nerve.
The fibers pass downward and backward to the middle line of the floor of the pelvis; the most posterior are inserted into the side of the last two segments of 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...
; those placed more anteriorly unite with the muscle of the opposite side, in a median fibrous raphé (anococcygeal raphé), which extends between the coccyx and the margin of the anus
Anus
The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...
.
The middle fibers are inserted into the side 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...
, blending with the fibers of the Sphincter muscles; lastly, the anterior fibers descend upon the side of the prostate to unite beneath it with the muscle of the opposite side, joining with the fibers of the sphincter ani externus
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 transversus perinei
Transversus perinei
Transversus perinei can refer to:* Transversus perinei superficialis muscle* Transversus perinei profundus muscle...
, at the central tendinous point of the perineum
Perineum
In human anatomy, the perineum is a region of the body including the perineal body and surrounding structures...
.
The anterior portion is occasionally separated from the rest of the muscle by connective tissue.
From this circumstance, as well as from its peculiar relation with the prostate
Prostate
The prostate is a compound tubuloalveolar exocrine gland of the male reproductive system in most mammals....
, which it supports as in a sling, it has been described as a distinct muscle, under the name of Levator prostatæ.
In the female the anterior fibers of the Levator ani descend upon the side of the 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...
.
Innervation
The levator ani muscles are mostly innervated by the pudendal nervePudendal 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...
, perineal nerve
Perineal nerve
The perineal nerve is a nerve arising from the pudendal nerve that supplies the perineum.-Structure:The perineal nerve is the inferior and larger of the two terminal branches of the pudendal nerve, is situated below the internal pudendal artery....
and inferior rectal nerve in concert. In addition, sacral spinal nerves (S3
Sacral spinal nerve 3
The sacral spinal nerve 3 is a spinal nerve of the sacral segment..It originates from the spinal column from below the 3rd body of the sacrum -Muscles:...
, S4
Sacral spinal nerve 4
The sacral spinal nerve 4 is a spinal nerve of the sacral segment..It originates from the spinal column from below the 4th body of the sacrum -Muscles:...
) innervate the muscles directly as well (in ~70% of people). Sometimes (in ~40% of people) the inferior rectal nerve innervates the levator ani muscles independently of the pudendal nerve.
Tail-wagging in animals
The levator ani muscles, in quadruped animals with tails, are responsible for moving the tail around in the act of "wagging." These muscles are not as strong as their human equivalents, as tail-wagging is less demanding than the support function that the muscles serve in humans.Levator ani syndrome
Levator ani syndrome (also known as levator syndrome and proctodynia) is episodic rectalRectum
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...
pain, caused by spasm of the levator ani muscle. The etiology
Etiology
Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....
is unknown.
Symptom
Symptom
A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...
s include a dull ache to the left 2 inches above the Anus or higher in the rectum and a feeling of constant rectal pressure or burning. The pain may also be felt in the low 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:...
or perineum
Perineum
In human anatomy, the perineum is a region of the body including the perineal body and surrounding structures...
.
The discomfort may be relieved by walking or pelvic tightening exercises similar to Kegel exercise
Kegel exercise
A pelvic floor exercise, more commonly called a Kegel exercise , consists of contracting and relaxing the muscles that form part of the pelvic floor, which are now sometimes colloquially referred to as the "Kegel muscles". Several tools exist to help with these exercises, though many are ineffective...
s. Other treatments include massage
Massage
Massage is the manipulation of superficial and deeper layers of muscle and connective tissue to enhance function, aid in the healing process, and promote relaxation and well-being. The word comes from the French massage "friction of kneading", or from Arabic massa meaning "to touch, feel or handle"...
of the muscle, warm baths, muscle relaxant
Muscle relaxant
A muscle relaxant is a drug which affects skeletal muscle function and decreases the muscle tone. It may be used to alleviate symptoms such as muscle spasms, pain, and hyperreflexia. The term "muscle relaxant" is used to refer to two major therapeutic groups: neuromuscular blockers and spasmolytics...
medications, therapeutic ultrasound
Therapeutic ultrasound
Therapeutic ultrasound refers generally to any type of procedure that uses ultrasound for therapeutic benefit. This includes HIFU, lithotripsy, targeted ultrasounddrug delivery, trans-dermal ultrasound drug delivery, ultrasound hemostasis, and ultrasound assisted thrombolysis.-Physical...
and biofeedback
Biofeedback
Biofeedback is the process of becoming aware of various physiological functions using instruments that provide information on the activity of those same systems, with a goal of being able to manipulate them at will...
. Electrical stimulation of the levator ani muscle has been used to try to break the spastic cycle. Injection of botulinum toxin A
Botulinum toxin
Botulinum toxin is a protein produced by the bacterium Clostridium botulinum, and is considered the most powerful neurotoxin ever discovered. Botulinum toxin causes Botulism poisoning, a serious and life-threatening illness in humans and animals...
has also been used.
Variants of levator ani syndrome include proctalgia fugax
Proctalgia fugax
Proctalgia fugax is a severe, episodic, rectal and sacrococcygeal pain. It can be caused by cramp of the pubococcygeus or levator ani muscles.-Presentation:...
(fleeting pain in the rectum) and coccydynia
Coccydynia
Coccydynia is a medical term meaning pain in the coccyx or tailbone area, usually brought on by sitting too abruptly.-Diagnosis:A number of different conditions can cause pain in the general area of the coccyx, but not all involve the coccyx and the muscles attached to it. The first task of...
(pain in the coccygeal
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...
region). Proctalgia fugax and levator ani syndrome have not been found to be of psychosomatic origin, although stressful events may trigger attacks.