The bulbospongiosus muscle (bulbocavernosus in older texts) is one of the superficial

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscle ...

s of the

perineum The perineum in humans is the space between the anus and scrotum in the male, or between the anus and the vulva in the female. The perineum is the region of the body between the pubic symphysis (pubic arch) and the coccyx (tail bone), includin ...

. It has a slightly different origin, insertion and function in males and females. In males, it covers the

bulb of the penis In botany, a bulb is structurally a short stem with fleshy leaves or leaf basesBell, A.D. 1997. ''Plant form: an illustrated guide to flowering plant morphology''. Oxford University Press, Oxford, U.K. that function as food storage organs durin ...

. In females, it covers the

vestibular bulb 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 ...

. In both sexes, it is innervated by the deep or muscular branch of the

perineal nerve 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 tes ...

, which is a branch of the

pudendal nerve The pudendal nerve is the main nerve of the perineum. It carries sensation from the external genitalia of both sexes and the skin around the anus and perineum, as well as the motor supply to various pelvic muscles, including the male or fema ...

Structure

In males, the bulbospongiosus is located in the middle line of the perineum, in front of the

anus The anus (Latin, 'ring' or 'circle') 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, the residual semi-solid waste that remains after food digestion, which, de ...

. It consists of two symmetrical parts, united along the median line by a tendinous

perineal raphe The perineal raphe is a visible line or ridge of tissue on the body that extends from the anus through the perineum to scrotum (male) or labia majora (female). It is found in both males and females, arises from the fusion of the urogenital fold ...

. 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

; 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.

Fibers

Its fibers diverge; the most posterior form a thin layer, which is lost on the inferior fascia of the

urogenital diaphragm Older texts have asserted the existence of a 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 t ...

; the middle fibers encircle the bulb and adjacent parts, of the

corpus cavernosum urethrae 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. Anatomy The proximal part of the corpus spongiosum is expanded to form the uret ...

, and join with the fibers of the opposite side, on the upper part of the corpus cavernosum urethrae, in a strong

aponeurosis An aponeurosis (; plural: ''aponeuroses'') is a type or a variant of the deep fascia, in the form of a sheet of pearly-white fibrous tissue that attaches sheet-like muscles needing a wide area of attachment. Their primary function is to join muscl ...

; the anterior fibers, spread out over the side of the corpus cavernosum

penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males do no ...

, to be inserted partly into that body, anterior to the

Ischiocavernosus The ischiocavernosus muscle (erectores penis ''or'' erector clitoridis in older texts) is a muscle just below the surface of the perineum, present in both men and women. Structure It arises by tendinous and fleshy fibers from the inner surface of ...

, 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 An erection (clinically: penile erection or penile tumescence) is a physiological phenomenon in which the penis becomes firm, engorged, and enlarged. Penile erection is the result of a complex interaction of psychological, neural, vascular, a ...

, the contractions of

orgasm Orgasm (from Greek , ; "excitement, swelling") or sexual climax is the sudden discharge of accumulated sexual excitement during the sexual response cycle, resulting in rhythmic, involuntary muscular contractions in the pelvic region charac ...

and

ejaculation Ejaculation is the discharge of semen (the ''ejaculate''; normally containing sperm) from the male reproductory tract as a result of an orgasm. It is the final stage and natural objective of male sexual stimulation, and an essential component ...

. In females it contributes to

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 exclu ...

and the contractions of orgasm, and closes the

vagina In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hymen ...

. This muscle serves to empty the canal of the

urethra The urethra (from Greek οὐρήθρα – ''ourḗthrā'') is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra con ...

, after the bladder has expelled its contents; during the greater part of the act of

micturition Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, ...

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 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. Anatomy The proximal part of the corpus spongiosum is expanded to form the ure ...

, 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 Deep or The Deep may refer to: Places United States * Deep Creek (Appomattox River tributary), Virginia * Deep Creek (Great Salt Lake), Idaho and Utah * Deep Creek (Mahantango Creek tributary), Pennsylvania * Deep Creek (Mojave River tributary) ...

as they are inserted into, and continuous with, the fascia of the penis.

Gallery

File:Gray407.png, Coronal section of anterior part of the male pelvis, through the pubic arch. Seen from in front. File:Gray542.png, The superficial branches of the internal pudendal artery in the male.

References

External links

* —"Muscles of the male superficial perineal pouch." * —"The Female Perineum: Muscles of the Superficial Perineal Pouch" * —"The urinary bladder and the urethra as seen in a frontal section of the female pelvis." * * {{Authority control Muscles of the torso Perineum