General Anatomy of the Male Reproductive System

Male reproductive system Testes – produce sperm and are essential Scrotum Epididymis Vas deferens Seminal vesicles Ejaculatory ducts Prostate Gland Urethra Penis

Male Reproductive System 1.Testes Ovoid glands that are suspended in the scrotum Attached to scrotal tissue and spermatic cords Consist of many lobules ( in each testis) Each lobule contains: –Seminiferous Tubules for spermatogenesis –Interstitial cells of Leydig that secrete testosterone.

Male Reproductive System The testes are each surrounded by two protective coats (or tunics): –Tunica Vaginalis (outer Layer) extension of peritoneum –Tunica Albuginea (Inner Layer) extends between each of the lobules

Male Reproductive System Sperm produced in the testes leave via the tubulus rectus that conveys them to a network of tubules on one side of each testis called the rete testis From here the sperm are carried via efferent ducts to the epididymis.

Male Reproductive System 2. Scrotum This literally means "pouch" or "sac" It is a pouch of skin that is incompletely divided into left and right halves. Each half houses one testis. The appearance of the scrotum changes with temperature. –Eg. Cold (or sexual arousal) it appears shorter and quite wrinkled, because it is pulled closer to the body for warmth. –Eg. Heat, the skin is flaccid (loose) and the testes hang lower in the scrotum to keep them cool.

Male Reproductive System The movement of the scrotum and testes helps to maintain intra scrotal and hence testicular temperature 93° Movement of the scrotum is achieved by two groups of muscles: –Dartos Muscle which is a smooth muscle and causes shrinking of the scrotum –Cremaster Muscle with is skeletal muscle and it elevates the testes. It is attached to the internal oblique muscle of the trunk

3. Epididymis Highly folded duct approx 6m long, for the passage of sperm from the testis to the vas deferens. It has 3 divisions: –Head: connected to the testes receiving immature sperm –Body –Tail: continuous with the vas deferens, contains smooth muscle and during ejaculation, contractions of the smooth muscle expel mature sperm into the vas deferens. Sperm may be stored in the epididymis from 18 hrs - 20 days. During this time the sperm mature, including becoming motile, so they can fertilize an ovum. Epididymis is shaped like a comma

Male Reproductive System 4. Vas deferens Short, fairly straight tube approx 45 cm long. Ascends from the scrotum into the abdomen and passes over the bladder. –Tube cut in vasectomy doesn’t effect erection or performance Vas deferens stores the sperm. –sperm are mature & motile –the local accumulation of CO2 from the normal metabolism of the sperm causes the pH to become acidic. under these conditions sperm lose their motility –on ejaculation, the alkaline seminal fluid will counteract the low pH and the sperm will become motile again.

Male Reproductive System 5. Seminal Vesicles 2 glands behind prostate gland, size & shape of finger, secretes viscous fluid = 60-70% of seminal fluid (nourish & energize sperm) Also secrete fructose, citric acid, amino acids and Prostaglandins.

Male Reproductive System 6. Ejaculatory ducts Short tubes that descend through the prostate gland and terminate in the urethra. Formed by the union of the vas deferens and seminal vesicle ducts

Male Reproductive System 7. Prostate gland –Chestnut-sized gland below bladder. –Surrounds the ejaculatory duct and part of the urethra. –Secretes a thin liquid that is milky, alkaline and constitutes 30% of the seminal fluid volume –Responsible for raising the pH of the female vagina. –Provides lubrication during coitus Cowper’s Glands –below prostate, 2 pea-sized glands connect to urethra by ducts; –secrete thick, clear mucus before ejaculation (at tip of penis) –alkaline to protect sperm from acidic vagina. –Fluid has sperm! (Sperm in urethra > PREGNANT!!)

Male Reproductive System 8. Urethra Tube cm long. Conveys urine and sperm (at different times). –Three regions of urethra –Contains glands which secrete mucus to aid lubrication during intercourse.

Male Reproductive System 9. Penis Copulatory organ of the external genitalia. Contains 3 compartments of erectile tissue which are covered by a loose layer of skin. Two "corpora cavernosa" One "corpus spongiosum" which lies ventrally in the penis and houses the spongy urethra. Expands at the end of the penis into the "glans penis". When aroused, inc. blood into penis, these compartments fill and expand –Leads to erect penis – compression of vessels prevents blood flow out.

A penis, with foreskin retracted

Male Reproductive System 9. Penis continued Erectile tissue is sponge-like containing venous sinuses surrounded by arteries and veins. Upon sexual stimulation, the arteries dilate and the spaces (or caverns) fill with blood. As they fill, the erectile tissue becomes rigid and the penis becomes erect. Two main functions of the penis: –Removal of urine via the urethra –Receipt and ejection of sperm and seminal fluid during copulation, again via the urethra.

Male Reproductive System In uncircumcised males there is a structure that covers the end of the glans penis called the "prepuce or foreskin". –Its proposed functions include protection, lubrication of glans, part of sexual pleasure system. uncircumcised circumcised

All length measurements were taken when the penises were erect, along the top of the penis, from the point where the top of the penile shaft meets the pubic area to the tip.

Male Anatomy & Physiology Factors effecting size: –heredity, vasocongestion, cold air or water, fear, anxiety (penis draws closer to body & smaller size) Erection – urethra/urinary duct closes so semen passes through (ejaculation) Erection not always because of sexual excitement –REM sleep (dreaming)

Myths Penis Size: related to masculinity, aggression, ability to “perform”, sexual attractiveness, virility. Size of shoe predictive of penis size (not research based!). Size not related to ability to have sexual intercourse or pleasure partner. Small flaccid penis enlarges more with erection than larger flaccid penis.

The Ejaculate Ejaculate volume is about 3 ml and ranges from 2 to 6 ml. pH is 7.5, slightly basic to neutralize the acidity of the urethra and the vagina Of the 3 ml of an ejaculate –About 0.2 ml, originates from the Cowper's gland – About 0.5 ml from the prostate gland – about 2 ml is secreted from the seminal vesicles

Reproductive Process Semen production –Seminal Fluid - ejaculated liquid with sperm –Function: nourish sperm, hospitable environment, transportation of sperm Semen is combo of: –seminal vesicle fld., prostate gland fld., sperm mixed in the urethra during ejaculation. Is thick & sticky (clotting factor in fluid) Keeps the sperm together during transport then liquefies so sperm can swim out. Color varies: opalescent (milky white), yellowish or grayish as ejaculate, then becomes clear as it liquefies. 1 tsp. (2-6 Milliliters) semen ejaculated = 200>500 million sperm

Review: Journey of the Sperm

interstitial cells- testosterone

sperm production in the seminferous tubules

sperm storage in the epididymis

transport in the vas deferens

ampulla - storage

fluid from the seminal vessicles ejaculatory duct

fluid from the prostate gland

cowper’s gland

ejaculation Spinal reflex triggers nerve impulses to ducts, glands, muscles of reproductive system.

Spermatogenesis The final step in the development the spermatids formed from spermatogenesis become mature spermatozoa, or sperm. The mature sperm cell has a head, midpiece, and tail. The head, also called the nuclear region, contains the 23 chromosomes surrounded by a nuclear membrane. The tip of the head is covered by an acrosome, which contains enzymes that help the sperm penetrate the female gamete. The midpiece, metabolic region, contains mitochondria that provide adenosine triphosphate (ATP). The tail, locomotor region, uses a typical flagellum for locomotion.