MALE REPRODUCTIVE ANATOMY

Internal Structures:

Link to diagram

Testes (testicles) Link to diagram

• primary sex organs; male gonads
• functions: produce _________________________ and ______________________
• each testis suspended from the body by a __________________________, containing nerves, blood vessels and vas deferens Link to diagram Link to another diagram
• each contains about 250 testicular lobules, separated by septa:

• each lobule contains 1-3 coiled seminiferous tubules (the site of ____________________________________________)
• in spaces between tubules, Leydig cells synthesize and secrete ______________________________

• also contain three types of ciliated sex accessory ducts (the tubulus rectus, rete testis, and efferent ductules), which function to _____________________ sperm and transport them from the testis to the epididymus Link to diagram

Epididymus (refer to above link for diagram)

• tightly coiled, elongated tubing network located on the back surface of each testis
• 3 functions: 1) sperm ___________________________ (in head and body), 2) sperm ______________ (in the tail), and 3) sperm ______________________ to the vas deferens

Vas Deferens Link to diagram (click on “view labeled image”)

• two ciliated, straight muscular tubes that connect the epididymus and the ejaculatory ducts
• 2 functions: 1) conducts sperm and associated fluids from the epididymus to the ejaculatory duct, and 2) __________________ in the enlarged distal ends, called the “_____________________"

Seminal Vesicles (refer to above link for diagram)

• paired glands lying next to the ampulla of the vas deferens, adjacent to the urinary bladder
• produce and secrete seminal fluid which comprises most of the volume of semen (________)
• seminal fluid is rich in ________________ and vitamin C (provides energy and nutrients for sperm), and contains ______________ (stimulates contraction of vas deferens and uterus)

Prostate Gland (refer to above link for diagram)

• single doughnut-shaped organ lying below the bladder and surrounding the urethra
• secretes an alkaline fluid which makes up about 1/3 the volume of semen, which enters urethra through many tiny ducts

Ejaculatory ducts (refer to above link for diagram)

• two ducts that pass through the center of the prostate gland, each formed when a ___________________________ joins with a __________________________________ duct
• receive sperm from the vas deferens, seminal fluid from the seminal vesicles, and prostatic fluid from the prostate gland
• immediately ejects the resulting __________________ into the urethra during ejaculation

Cowper’s (Bulbourethral) Glands (refer to above link for diagram)

• paired pea-sized glands located on each side of the urethra, just below the prostate gland
• secrete mucus that ___________________________________ in the urethra and __________________ the tip of the penis during ejaculation

Urethra (refer to above link for diagram)

· straight muscular tube between the bladder, ejaculatory ducts and tip of the penis (located within the corpus spongiosum of the penis)

· functions as conduit for urine from the bladder, semen from the ejaculatory ducts, and fluid from the Cowper’s glands to the outside of the body through the urethral opening at the tip of the penis

External Structures

Penis Link to diagram

• urinary and copulatory organ; averages ___________ inches long when flaccid, ___________ inches when erect
• 4 parts:

1. shaft: body of the penis attached to the pelvic wall; contains 3 cylindrical columns of highly vascular erectile tissue filled with blood sinuses and held together by a connective-tissue sheath:

o corpora cavernosa – two columns, one on each side of the _________ of the shaft; proximal ends are anchored to the bony pelvis

o corpus spongiosum – single column in the ____________ portion of the shaft containing the urethra; expanded at the distal end to form the _________

2. glans: enlarged, acorn-shaped area at the tip of the penis Link to diagram

o densely packed with nerve fibers, making it highly sensitive to touch, pressure, temperature

o rounded ridge at the back end is called the ________________, where the shaft connects to the glans

3. prepuce (foreskin): a thin, loose layer of skin which extends to form a hood over the glans

o is sometimes removed after birth (circumcision) Link to diagram Link to another diagram

o although urinary infections are more common in uncircumcised boys, this risk can be virtually eliminated with proper hygiene

o most common reasons for circumcision are religious, cultural, or aesthetic

4. urethral opening: site of exit for semen and urine

Scrotum Link to diagram

• sac-like pouch, suspended from the groin, divided by a septum into two chambers, each of which contains one testis
• skin is relatively dark and hairless, containing touch, pressure and temperature receptors, numerous sweat glands
• internal temperature is about _________________________ than normal body temperature (required for spermatogenesis)
• left side usually hangs lower than right due to greater length of the left __________________________________
• two muscle layers: Link to diagram

1. _____________________: layer of smooth muscle underneath the scrotal skin; contracts when temperature is too low, causing skin to wrinkle and testes to ascend closer to abdomen

2. ______________________ muscle: layer of striated muscle located just under the tunica dartos; contracts when inner thigh is stroked

Click for question review