MALE REPRODUCTIVE SYSTEM

Anatomy of the Male Reproductive System

• The primary sex organs are the testes.• The accessory organs include a complex set of ducts

and tubules leading from the testes to the penis.• The penis is the organ of copulation.

Anatomy of the Male Reproductive System

Figure 28.11

Scrotum

• The scrotum is a skin-covered sac that provides the testes with a cooler environment than body temperature.

• Sperm develop successfully at approximately 3 Celsius below normal body temperature.

• The scrotum is homologous to the labia majora in the female.• A raphe separates the two scrotal sacs.• The dartos muscle is a layer of smooth muscle that is part of the wall

of the scrotum.

Scrotum

Figure 28.12

Spermatic Cord

The spermatic cord originates at the inguinal canal. It consists of the following:• Testicular artery—branch of the abdominal aorta• Pampiniform plexus—a network of veins surrounding the testicular artery• Cremaster muscle and fascia—formed from muscle fiber extensions of the internal oblique muscle• Autonomic nerves— travel with plexus and connect to the testes

Spermatic Cord

Figure 28.12

Testes

• The function of the testes is twofold:1.production of sperm2.production and secretion of androgens (male sex hormones), the most

common being testosterone

• Each testis is covered anteriorly and laterally by a serous membrane called the tunica vaginalis

• The tunica vaginalis has an outer parietal layer and an inner visceral layer

Testes

Figure 28.13

Testes

• Located just deep to the visceral layer and in contact with the testis is a thick, whitish fibrous capsule covering the testis called the tunica albuginea.

• The tunica albuginea projects into the interior of the testis as the mediastinum testis through which blood vessels, lymphatic vessels, and some nerves enter and leave the testis.

Testes

• The tunica albuginea projects internally into the testes to form septa.• The septa subdivide to form about 250 lobules.• Each lobule contains four convoluted seminiferous tubules.

Seminiferous Tubules

Seminiferous tubules contain two types of cells:1. Sustentacular cells—nondividing support cells that assist with

sperm development; connected to each other by tight junctions and form the blood-testis barrier

2. A population of dividing germ cells that continuously produce sperm beginning at puberty

Interstitial Space

• Spaces external to and in between seminiferous tubules• Interstitial cells reside in these space and produce hormones called

androgens

Figure 28.13

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Spermatids

Sperm cells

Spermatogonia

Interstitial cells

LM 250x

(b) Seminiferous tubule, cross section

Seminiferoustubule

Tubule lumen

Sustentacularcells

b: © The McGraw-Hill Companies, Inc./Photo by Dr. Alvin Telser

Spermatogenesis and Spermiogenesis

Figure 28.14

Spermatogenesis and Spermiogenesis

Figure 28.14

Stages of Spermatogenesis

Ducts in the Male Reproductive System

Beginning at the testis and extending through the penis, the ducts are:• Rete testis• Efferent ductules• Epididymis• Ductus deferens• Ejaculatory duct• Urethra

Ducts in the Male Reproductive System

Figure 28.15

Rete Testis• Receive sperm from seminiferous tubules

Figure 28.13

Efferent Ductules• Connect rete testis to epididymis

Figure 28.13

Epididymis

• Situated on the posterosuperior surface of the testes, the epididymis has three regions:- head- body- tail

• Internally, the epididymis contains a long convoluted duct of the epididymis

• The epididymis stores sperm and serves in the maturation process of sperm

Epididymis

Figure 28.13

Ductus Deferens

• Sperm leaving the epididymis enter the ductus deferens (vas deferens).

• This tube travels within the spermatic cord and enters the pelvic cavity through the inguinal canal.

• As the ductus deferens approaches the prostate gland, it enlarges to form the ampulla.

• The ampulla unites with the proximal portion of the seminal vesicle to form the ejaculatory duct.

Ductus Deferens

Figure 28.15

Ejaculatory Duct

• Formed by a uniting of the ductus deferens and the seminal vesicle• Located within the substance of the prostate gland between 1–2 cm

long and conducts sperm from the ductus deferens to the prostatic urethra

Ejaculatory Duct

Figure 28.15

Urethra

• Transports semen from both ejaculatory ducts to the outside of the body

• The male urethra is subdivided into three regions:1. prostatic urethra2. membranous urethra3. spongy urethra

Urethra

Figure 28.15

Accessory Glands

• There are three glands that secrete fluids to mix with sperm to create seminal fluid.

• These secretions nourish the sperm and neutralize the acidity of the vagina.

• The three glands are as follows:1. seminal vesicles2. prostate gland3. bulbourethral glands

Seminal Vesicles

• The paired seminal vesicles are located on the posterior surface of the urinary bladder lateral to the ampulla of the ductus deferens.

• They secrete a viscous, whitish-yellow, alkaline fluid containing fructose and prostaglandins.

Seminal Vesicles

Figure 28.15

Seminal Vesicles and Prostate Gland

Figure 28.16

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Seminal vesicle

LM 80xLM 25x

(b) Prostate gland

Tubuloalveolarglands inprostate gland

Mucosal foldsin seminalvesicle

(a) Seminal vesicle

Prostategland

a: © Carolina Biological/Visuals Unlimited; b: © The McGraw-Hill Companies, Inc./Photo by Dr. Alvin Telser

Prostate Gland

• The prostate gland is located immediately inferior to the urinary bladder.

• It produces substances that are secreted directly into the prostatic urethra.

• Prostatic secretion is slightly acidic and contains mucin, citric acid (nutrient for sperm), seminalplasmin (antibacterial),and prostatic-specific antigen (PSA, an enzyme that helps liquify semen).

Prostate Gland

Figure 28.15

Prostate Gland

Figure 28.11

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Urinary bladder

Pubic symphysis

Ductus deferens

Urethra

Urogenital diaphragm

Penis

Glans

Ureters

Ampulla of ductus deferens

Seminal vesicle

Ejaculatory duct

Prostate gland

Bulbourethral gland

Anus

Epididymis

Scrotum

Testis

Bulbourethral Glands

• The bulbourethral glands are located in the urogenital diaphragm on either side of the membranous urethra.

• Mucin is secreted from these glands and enters the spongy urethra at the base of the penis.

Bulbourethral Glands

Figure 28.15

Semen

• Seminal fluid from the three accessory glands combines with sperm from the testes to make up semen.

• When released during intercourse, semen is called ejaculate.• Semen normally measures about 3–5 ml in volume and contains 200–

500 million sperm.

Penis

• The penis and the scrotum form the external genitalia in males.• Internally, the attached portion of the penis is the root forming both

the bulb and the crura of the penis.• The body (shaft) is the elongated portion of the penis.• The tip of the penis is the glans, which surrounds the external

urethral orifice.

Anatomy of the Penis

Figure 28.17

Penis

The shaft of the penis is comprised of three parallel, cylindrical erectile bodies:1. Paired corpora cavernosa are located dorsolaterally and terminate at the distal shaft of the penis2. A single corpus spongiosum is inferior and midline and surrounds the spongy urethra3. The distal end of the corpus spongiosum continues within the glans

Anatomy of the Penis

Figure 28.17

CircumcisionCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Prepuce

(b) Uncircumcised penis(a) Circumcised penis

Erection and Ejaculation

• The erectile bodies are composed of venous spaces, which fill with blood from a central artery to produce an erection.

• Parasympathetic in nervation is responsible for penile erection.• Ejaculation is the expelling of semen from the penis, in part, by the

rhythmic contraction of the smooth muscle of the urethra.• Sympathetic in nervation promotes ejaculation.

Development of the Reproductive Systems

Figure 28.18

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Mesonephros

Genital ridge

Kidney

Mesonephric duct

Cloaca

MaleFemale

Sexually Indifferent Stage

Testes

Efferent ductules

Epididymis

Urinary bladder

Seminal vesicle

Urinary bladder

Seminal vesicle

Prostate gland

Bulbourethral gland

Ductus deferens

Epididymis

Efferent ductules

Testis

Urethra

At birth

Ovaries

Ovary

Uterus

Vagina

UrethraHymen

At birth

Paramesonephricduct

Weeks 5–6

Paramesonephricduct forming theuterine tube

Mesonephricduct(degenerating)

Paramesonephricduct (degenerating)

Mesonephric ductforming the ductusdeferens

Urogenital sinusforming the urethra

Weeks 10–12Weeks 10–12

Urogenital sinus formingthe urethra and inferior vagina

Fused paramesonephricducts forming the uterus

Uterinetube

Urinary bladder(moved aside)

Urinary bladder(moved aside)

Development of the Reproductive Systems

Figure 28.19