Bulbospongiosus muscle
Encyclopedia
Bulbospongiosus is one of the superficial muscle
s 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. In females, it covers the vestibular bulb.
In both sexes, it is innervated by the deep/muscular branch of the perineal nerve
, which is a branch of the pudendal nerve
.
, ejaculation
, and the feelings of orgasm
. In females it contributes to clitoral erection
and the feelings of orgasm, and closes the vagina
.
This muscle serves to empty the canal of the urethra
, after the bladder has expelled its contents; during the greater part of the act of micturition
its fibers are relaxed, and it only comes into action at the end of the process.
The middle fibers are supposed by Krause to assist in the erection of the corpus cavernosum urethræ, by compressing the erectile tissue of the bulb.
The anterior fibers also contribute to the erection of the penis by compressing the deep dorsal vein of the penis as they are inserted into, and continuous with, the fascia of the penis.
, in front of the anus
. It consists of two symmetrical parts, united along the median line by a tendinous raphé
.
It arises from the central tendinous point of the perineum
and from the median raphé
in front.
; the middle fibers encircle the bulb and adjacent parts, of the corpus cavernosum urethræ, and join with the fibers of the opposite side, on the upper part of the corpus cavernosum urethræ, in a strong aponeurosis
; the anterior fibers, spread out over the side of the corpus cavernosum penis
, to be inserted partly into that body, anterior to the Ischiocavernosus, occasionally extending to the pubis, and partly ending in a tendinous expansion which covers the dorsal vessels of the penis.
The latter fibers are best seen by dividing the muscle longitudinally, and reflecting it from the surface of the corpus cavernosum urethræ.
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...
s of the perineum
Perineum
In human anatomy, the perineum is a region of the body including the perineal body and surrounding structures...
. It has a slightly different origin, insertion and function in males and females. In males, it covers the bulb of the penis. In females, it covers the vestibular bulb.
In both sexes, it is innervated by the deep/muscular branch of the 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....
, which is a branch of the pudendal nerve
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...
.
Action
In males it contributes to erectionErection
Penile erection is a physiological phenomenon where the penis becomes enlarged and firm. Penile erection is the result of a complex interaction of psychological, neural, vascular and endocrine factors, and is usually, though not exclusively, associated with sexual arousal...
, ejaculation
Ejaculation
Ejaculation is the ejecting of semen from the male reproductory tract, and is usually accompanied by orgasm. It is usually the final stage and natural objective of male sexual stimulation, and an essential component of natural conception. In rare cases ejaculation occurs because of prostatic disease...
, and the feelings of orgasm
Orgasm
Orgasm is the peak of the plateau phase of the sexual response cycle, characterized by an intense sensation of pleasure...
. In females it contributes to clitoral erection
Clitoral erection
Clitoral erection is a physiological phenomenon where the clitoris becomes enlarged and firm. Clitoral erection is the result of a complex interaction of psychological, neural, vascular and endocrine factors, and is usually, though not exclusively, associated with sexual...
and the feelings of orgasm, and closes 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...
.
This muscle serves to empty the canal of the urethra
Urethra
In anatomy, the urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis, and carries semen as well as urine...
, after the bladder has expelled its contents; during the greater part of the act of micturition
Urination
Urination, also known as micturition, voiding, peeing, weeing, pissing, and more rarely, emiction, is the ejection of urine from the urinary bladder through the urethra to the outside of the body. In healthy humans the process of urination is under voluntary control...
its fibers are relaxed, and it only comes into action at the end of the process.
The middle fibers are supposed by Krause to assist in the erection of the corpus cavernosum urethræ, by compressing the erectile tissue of the bulb.
The anterior fibers also contribute to the erection of the penis by compressing the deep dorsal vein of the penis as they are inserted into, and continuous with, the fascia of the penis.
Location
The bulbospongiosus is located in the middle line of the perineumPerineum
In human anatomy, the perineum is a region of the body including the perineal body and surrounding structures...
, in front 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,...
. It consists of two symmetrical parts, united along the median line by a tendinous raphé
Perineal raphe
The perineal raphe is a visible line or ridge of tissue on the human body that extends from the anus through the perineum.In men, this raphe continues through the midline of the scrotum and upwards through the posterior midline aspect of the penis...
.
It arises from 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...
and from the median raphé
Median raphe
The term Median raphe can refer to one of two different anatomical structures:* The pharyngeal raphe* The perineal raphe, also known as the "median r. of perineum"...
in front.
Fibers
Its fibers diverge like the barbs of a quill-pen; the most posterior form a thin layer, which is lost on the inferior fascia of the urogenital diaphragmUrogenital 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...
; the middle fibers encircle the bulb and adjacent parts, of the corpus cavernosum urethræ, and join with the fibers of the opposite side, on the upper part of the corpus cavernosum urethræ, in a strong aponeurosis
Aponeurosis
Aponeuroses are layers of flat broad tendons. They have a shiny, whitish-silvery color, are histologically similar to tendons, and are very sparingly supplied with blood vessels and nerves. When dissected, aponeuroses are papery, and peel off by sections...
; the anterior fibers, spread out over the side of the corpus cavernosum penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...
, to be inserted partly into that body, anterior to the Ischiocavernosus, occasionally extending to the pubis, and partly ending in a tendinous expansion which covers the dorsal vessels of the penis.
The latter fibers are best seen by dividing the muscle longitudinally, and reflecting it from the surface of the corpus cavernosum urethræ.