human male A man is an adult male human. Prior to adulthood, a male human is referred to as a boy (a male child or adolescent). Like most other male mammals, a man's genome usually inherits an X chromosome from the mother and a Y chrom ...

anatomy Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having it ...

, the radix () or root of the

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 d ...

is the internal and most

proximal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

potrion of the

human penis The human penis is an external male intromittent organ that additionally serves as the urinary duct. The main parts are the root (radix); the body (corpus); and the epithelium of the penis including the shaft skin and the foreskin (prepuce) c ...

that lies in 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), includi ...

. Unlike the pendulous

body Body may refer to: In science * Physical body, an object in physics that represents a large amount, has mass or takes up space * Body (biology), the physical material of an organism * Body plan, the physical features shared by a group of anima ...

or ''corpus'' of the penis which is suspended from the

pubic symphysis The pubic symphysis is a secondary cartilaginous joint between the left and right superior rami of the pubis of the hip bones. It is in front of and below the urinary bladder. In males, the suspensory ligament of the penis attaches to the pubi ...

, the root is attached to the

pubic arch The pubic arch, also referred to as the ''ischiopubic arch'', is part of the pelvis. It is formed by the convergence of the inferior rami of the ischium and pubis on either side, below the pubic symphysis. The angle at which they converge is kno ...

of the pelvis and is not visible externally. It is triradiate in form, consisting of three masses of

erectile tissue Erectile tissue is tissue in the body with numerous vascular spaces, or cavernous tissue, that may become engorged with blood. However, tissue that is devoid of or otherwise lacking erectile tissue (such as the labia minora, the vestibule/vagina and ...

; the two diverging crura, one on either side, and the median

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 ...

or urethral bulb. Approximately one third to one half of the penis is embedded in the pelvis and can be felt through the

scrotum The scrotum or scrotal sac is an anatomical male reproductive structure located at the base of the penis that consists of a suspended dual-chambered sac of skin and smooth muscle. It is present in most terrestrial male mammals. The scrotum co ...

and in the perineum.

Anatomy

Structure

The root of the penis begins directly below the

bulbourethral glands The bulbourethral glands or Cowper's glands (named for English anatomist William Cowper) are two small exocrine glands in the reproductive system of many male mammals (of all domesticated animals, they are absent only in dogs). They are homolog ...

, or ''Cowper glands'', and consists of three long masses of tissue; the bulb and the crura. The

is an enlarged mass of erectile tissue that is located in the midline of the root and is traversed by the

male 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 ...

. It continues as a long cylindrical body on the ventral aspect of the shaft called

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 ...

. The left and right crura are located laterally on the two sides of the bulb and are attached to the ischiopubic arch. They continue into the dorsal aspect of the shaft forming the two corpora cavernosa that are separated by the

septum of the penis The two corpora cavernosa penis are surrounded by a strong fibrous envelope consisting of superficial and deep fibers. The superficial fibers are longitudinal in direction, and form a single tube which encloses both corpora; the deep fibers are arr ...

. During arousal, the root and the corpora cavernosa engorge with blood and become rigid ( erection). Meanwhile, the corpus spongiosum remains pliable making the urethra a viable channel for

semen Semen, also known as seminal fluid, is an organic bodily fluid created to contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize the female ovum. Sem ...

during

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 compone ...

Muscles

There are four muscles associated with the root of the penis; a pair of

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 ...

and a pair of bulbospondiosus muscles. Each crus is covered by the ischiocavernosus muscle which helps maintain an erection by contracting to force blood from the crura into the corpora cavernosa. The bulb is surrounded by the bulbospongiosus muscle which contracts to help empty the urethra of any residual semen and urine. It also helps maintain the erection by increasing the pressure in the bulb. During

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 chara ...

, the muscles surrounding the root contract involuntarily pushing the semen towards the

urinary meatus The urinary meatus, (, ) also known as the external urethral orifice, is the opening of the urethra. It is the point where urine exits the urethra in both sexes and where semen exits the urethra in males. The meatus has varying degrees of sensit ...

Fascia

Each erectile tissue has fascial coverings, or bands of connective tissue, which surround and support them. The root of the penis lies in the perineum between the

perineal membrane 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. It is the superior border of the su ...

, or ''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 ...

'', and the

fascia of Colles The membranous layer of the superficial fascia of the perineum (Colles' fascia) is the deeper layer ( membranous layer) of the superficial perineal fascia. It is thin, aponeurotic in structure, and of considerable strength, serving to bind down th ...

, the deeper layer of the

superficial perineal fascia The subcutaneous tissue of perineum (or superficial perineal fascia) is a layer of subcutaneous tissue surrounding the region of the perineal body. The superficial fascia of this region consists of two layers, superficial and deep. * The superfi ...

Ligaments

In addition to being attached to the fasciæ and the pubic ramus, the root is bound to the front of the

by the fundiform and

suspensory ligament A suspensory ligament is a ligament that supports a body part, especially an organ. Types include: * Suspensory ligament of axilla, also known as Gerdy's ligament * Cooper's ligaments, also known as the suspensory ligaments of Cooper or Suspensory ...

s. * The

fundiform ligament The fundiform ligament or fundiform ligament of the penis is a specialization or thickening of the superficial ( Scarpa's) fascia extending from the linea alba of the lower abdominal wall. It runs from the level of the pubic bone, laterally aroun ...

springs from the front of the sheath of the

Rectus abdominis The rectus abdominis muscle, ( la, straight abdominal) also known as the "abdominal muscle" or simply the "abs", is a paired straight muscle. It is a paired muscle, separated by a midline band of connective tissue called the linea alba. It exte ...

and the linea alba; it splits into two fasciculi which encircle the root of the penis. * The upper fibers of the

pass downward from the lower end of the linea alba, and the lower fibers from the pubic symphysis; together they form a strong fibrous band, which extends to the upper surface of the root, where it blends with the fascial sheath of the organ.

Images

File:Cunningham's Text-book of anatomy (1914) (20629645520).jpg, Root of the penis File:Cunningham's Text-book of anatomy (1914) (20630878319).jpg, Lateral cross-section of male genitourinary system

References

Mammal male reproductive system Human penis anatomy {{genitourinary-stub