Bulbospongiosus muscle

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Bulbospongiosus muscle
Bulbospongiosus-Male.png
Muscles of male perineum (bulbocavernosus visible in red)
Bulbospongiosus-Female.png
Muscles of the female perineum (bulbocavernosus visible in red)
Details
Origin Median raphe
Artery Perineal artery
Nerve Pudendal nerve
Actions In males, empties the urethra; in females, clenches the vagina
Identifiers
Latin musculus bulbospongiosus
TA98 A09.5.02.005
TA2 2418
FMA 19729
Anatomical terms of muscle

The bulbospongiosus muscles (in older texts bulbocavernosus and, for female muscle, constrictor cunni) are a subgroup of the superficial muscles of the perineum. [1] They have a slightly different origin, insertion and function in males and females. In males, these muscles cover the bulb of the penis, while in females, they cover the vestibular bulbs.

Contents

In both sexes, they are innervated by the deep or muscular branch of the perineal nerve, which is a branch of the pudendal nerve.

Structure

In males, the bulbospongiosus is located in the middle line of the perineum, in front of the anus. It consists of two symmetrical parts, united along the median line by a tendinous perineal raphe. It arises from the central tendinous point of the perineum and from the median perineal raphe in front.

In females, there is no union, nor a tendinous perineal raphe; the parts are disjoint primarily and arise from the same central tendinous point of the perineum, which is the tendon that is formed at the point where the bulbospongiosus muscle, superficial transverse perineal muscle, and external anal sphincter muscle converge to form this major supportive structure of vagina and other organs, and from the clitoris in front. [2]

Fibers

Its fibers diverge; the most posterior form a thin layer, which is lost on the inferior fascia of the urogenital diaphragm; the middle fibers encircle the bulb and adjacent parts, of the corpus cavernosum urethrae, and join with the fibers of the opposite side, on the upper part of the corpus cavernosum urethrae, 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 urethra.

Function

In males, it contributes to erection, the contractions of orgasm and ejaculation. [3] In females, it contributes to clitoral erection [4] and the contractions of orgasm, and closes the vagina.

Rhythmic contractions of bulbospongiosus muscles during male orgasm

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 urination 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 spongiosum, 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.

Related Research Articles

<span class="mw-page-title-main">Perineum</span> Region of the body between the genitals and anus

The perineum in mammals is the space between the anus and the genitals. The human perineum is between the anus and scrotum in the male or between the anus and vulva in the female. The perineum is the region of the body between the pubic symphysis and the coccyx, including the perineal body and surrounding structures. The perineal raphe is visible and pronounced to varying degrees. The perineum is an erogenous zone. This area is also known as the taint or gooch in American slang.

<span class="mw-page-title-main">Levator ani</span> Broad, thin muscle group, situated on either side of the pelvis

The levator ani is a broad, thin muscle group, situated on either side of the pelvis. It is formed from three muscle components: the pubococcygeus, the iliococcygeus, and the puborectalis.

<span class="mw-page-title-main">Ischiocavernosus muscle</span> Sheet of fibrous tissue between the thigh and the front of the perineum

The ischiocavernosus muscle is a muscle just below the surface of the perineum, present in both men and women.

<span class="mw-page-title-main">Corpus spongiosum (penis)</span> Spongy tissue within the human penis

The corpus spongiosum is the mass of spongy tissue surrounding the male urethra within the penis. It is also called the corpus cavernosum urethrae in older texts.

<span class="mw-page-title-main">External anal sphincter</span> Flat plane of skeletal muscle fibers

The external anal sphincter is an oval tube of skeletal muscle fibers. Distally, it is adherent to the skin surrounding the margin of the anus. It exhibits a resting state of tonical contraction and also contracts during the bulbospongiosus reflex.

<span class="mw-page-title-main">External sphincter muscle of male urethra</span>

The external sphincter muscle of male urethra, also sphincter urethrae membranaceae, sphincter urethrae externus, surrounds the whole length of the membranous urethra, and is enclosed in the fascia of the urogenital diaphragm.

<span class="mw-page-title-main">Bulb of vestibule</span> One of two elongated masses of erectile tissue in the human clitoris

In female anatomy, the vestibular bulbs, bulbs of the vestibule or clitoral bulbs are two elongated masses of erectile tissue typically described as being situated on either side of the vaginal opening. They are united to each other in front by a narrow median band. Some research indicates that they do not surround the vaginal opening, and are more closely related to the clitoris than to the vestibule. They constitute the root of the clitoris along with the crura.

<span class="mw-page-title-main">Perineal nerve</span> Nerve of the perineum

The perineal nerve is a nerve of the pelvis. It arises from the pudendal nerve in the pudendal canal. It gives superficial branches to the skin, and a deep branch to muscles. It supplies the skin and muscles of the perineum. Its latency is tested with electrodes.

<span class="mw-page-title-main">Fascia of Colles</span>

The membranous layer of the superficial fascia of the perineum is the deeper layer of the superficial perineal fascia. It is thin, aponeurotic in structure, and of considerable strength, serving to bind down the muscles of the root of the penis. Colles' fascia emerges from the perineal membrane, which divides the base of the penis from the prostate. Colles' fascia emerges from the inferior side of the perineal membrane and continues along the ventral (inferior) penis without covering the scrotum. It separates the skin and subcutaneous fat from the superficial perineal pouch.

<span class="mw-page-title-main">Corpus cavernosum penis</span> Sponge-like region of erectile tissue

A corpus cavernosum penis (singular) is one of a pair of sponge-like regions of erectile tissue, which contain most of the blood in the penis during an erection.

<span class="mw-page-title-main">Dorsal artery of the penis</span> Artery of the penis

The dorsal artery of the penis is a bilaterally paired terminal branch of the internal pudendal artery which passes upon the dorsum of the penis to the base of the glans penis, where it unites with its contralateral partner and supply the glans and foreskin.

<span class="mw-page-title-main">Transverse perineal muscles</span>

The transverse perineal muscles are the superficial and the deep transverse perineal muscles.

<span class="mw-page-title-main">Perineal membrane</span> Anatomical term

The perineal membrane is an anatomical term for a fibrous membrane in the perineum. The term "inferior fascia of urogenital diaphragm", used in older texts, is considered equivalent to the perineal membrane.

<span class="mw-page-title-main">Superficial perineal pouch</span>

The superficial perineal pouch is a compartment of the perineum.

<span class="mw-page-title-main">Deep perineal pouch</span> Anatomic space enclosed partly by the perineum

The deep perineal pouch is the anatomic space enclosed in part by the perineum and located superior to the perineal membrane.

<span class="mw-page-title-main">Urogenital triangle</span> Anterior part of the perineum

The urogenital triangle is the anterior part of the perineum. In female mammals, it contains the vulva, while in male mammals, it contains the penis and scrotum.

<span class="mw-page-title-main">Urethral sphincters</span> Muscles keeping urine in the bladder

The urethral sphincters are two muscles used to control the exit of urine in the urinary bladder through the urethra. The two muscles are either the male or female external urethral sphincter and the internal urethral sphincter. When either of these muscles contracts, the urethra is sealed shut.

<span class="mw-page-title-main">Root of penis</span> Internal portion of the human penis

In human male anatomy, the radix or root of the penis is the internal and most proximal portion of the human penis that lies in the perineum. Unlike the pendulous body of the penis, which is suspended from the pubic symphysis, the root is attached to the pubic arch of the pelvis and is not visible externally. It is triradiate in form, consisting of three masses of erectile tissue; the two diverging crura, one on either side, and the median bulb of the penis or urethral bulb. Approximately one third to one half of the penis is embedded in the pelvis and can be felt through the scrotum and in the perineum.

<span class="mw-page-title-main">Muscular branches of perineal nerve</span> Nerve of the perineum

The deep branch of the perineal nerve is a nerve of the perineum. It is a branch of the perineal nerve, from the pudendal nerve. It supplies the superficial transverse perineal muscle, bulbospongiosus muscle, ischiocavernosus muscle, the bulb of penis, levator ani, and the external anal sphincter.

<span class="mw-page-title-main">Vaginal support structures</span> Structures that maintain the position of the vagina within the pelvic cavity

The vaginal support structures are those muscles, bones, ligaments, tendons, membranes and fascia, of the pelvic floor that maintain the position of the vagina within the pelvic cavity and allow the normal functioning of the vagina and other reproductive structures in the female. Defects or injuries to these support structures in the pelvic floor leads to pelvic organ prolapse. Anatomical and congenital variations of vaginal support structures can predispose a woman to further dysfunction and prolapse later in life. The urethra is part of the anterior wall of the vagina and damage to the support structures there can lead to incontinence and urinary retention.

References

  1. Maclean, Allan; Reid, Wendy (2011). "40". In Shaw, Robert (ed.). Gynaecology. Edinburgh New York: Churchill Livingstone/Elsevier. pp. 599–612. ISBN   978-0-7020-3120-5; Access provided by the University of Pittsburgh{{cite book}}: CS1 maint: postscript (link)
  2. "Human Anatomy, The Female Perineum, Muscles of the Superficial Perineal Pouch". act.downstate.edu. SUNY Downstate Medical Center. Archived from the original on 2019-07-31. Retrieved 2018-02-03.
  3. Marieb, Elaine (2013). Anatomy & physiology : books a la carte edition. Benjamin-Cummings. p. 895. ISBN   9780321887603.
  4. Dean O'Loughlin, Valerie; Stouter Bidle, Theresa; McKinley, Michael P. (2022). "Muscular System: Axial and Appendicular Muscles". Anatomy and Physiology: An Integrative Approach (Fourth ed.). McGraw Hill. p. 395. ISBN   9781264265411.