Bio 30- Male Anatomy

Role of the Male Reproductive System

To produce sperm and deliver them to the

female.

When a sperm combines with an egg, it contributes half the genetic material of the offspring and, in humans and other mammals, determines its sex.

Scrotum

•pouch of skin to hold testes outside of the body (membrane forms over canal) which prevents the testes from re-entering the abdomen)

• sperm cannot develop at body temperature (testes do not descend? STERILE MALE)

Urethra and Ejaculatory duct

•conducts semen through the penis

• carries urine from the bladder to the exterior of the body

Epididymis

•coiled tube where sperm matures and develops (becomes motile)

Vas Deferens

•conducts sperm from epididymis to urethra via ejaculatory duct

FYI- the van deferens is also known as the ductus deferens

Penis (Glands Penis and Foreskin)

•transfers sperm from male to female reproductive tract

•contains the urethra

Testes (testicles)

•produces sperm and sex hormones (testosterone)

Seminiferous Tubules

•bundles of coiled tubes (total length 500m) leading to the epididymis

•produce immature sperm cells -site of spermatogenesis (formation of sperm cells)

Urinary Bladder

•holds and eliminates urine

Rectum and Anus

•holds and eliminates waste

Glands that contribute fluids to semen

-seminal vesicles

-prostate gland

-cowpers gland

Seminal Vesicles

•contributes fructose, prostaglandins, and fluid to semen

Prostate Gland

•contributes to alkaline and mucous fluids to semen

•protects sperm against the acidic environment of the vagina

Cowper’s Gland

•contributes alkaline and mucous fluids to semen

•secretes a mucus-rich fluid prior to ejaculation

Path of sperm from production to ejaculation

testis (site of production)

→ epididymis (stored)

→ vas deferens (transfer tube)

→ seminal vesicle (adds fructose, prostaglandins)

→ prostate gland (adds alkaline, mucous)

→ Cowper’s gland (adds alkaline, mucous)

→ urethra (now called semen)

→ out!

Sexual Excitement (erection)

•erectile tissue in penis fills with blood

•parasympathetic: arteries leading to penis dilate

•sinuses swell, veins constrict keeping blood in the penis

*impotency (erectile dysfunction)-penis fails to become erect

Seminiferous Tubules and Interstitial

Tissues

-interstitial cell

-spermatogonium

-sperm

-Sertoli cell

Interstitial Cell

•hormone-secreting cells (secrete testosterone) that lie outside of the seminiferous tubules of the testes

Spermatogonium

•a diploid germ cell that at puberty will be stimulated by hormones to become a sperm cell

Sperm

•the male gametes carry 23 chromosomes to fertilize an egg (female also contains 23 chromosomes)

Sertoli Cell

•cells in the seminiferous tubules that support and nourish developing sperm cells

Mature Spermatozoa (sperm)

•produced by a process called spermatogenesis in the testes.

•meiotic division of spermatocytes produces spermatids which then differentiate into mature sperm

Sperm Info

•sperm are quite simple in structure because their sole purpose is to swim to the egg and donate their genetic material.

•they are composed of three regions: headpiece, midpiece, and tail.

•sperm do not live long (only about 48 hours), but they swim quickly and there are so many of them (millions per ejaculation) that some are able to reach the egg tofertilize it

Acrosome

•stores enzymes needed to penetrate the protective layer of the egg

Nucleus

•contains 23 chromosomes (half the genetic information needed for a human being)

Mitochondrion

•provides energy to move the tail (flagellum)

Head

•contains the nucleus (genetic material) and is covered by the acrosome cap

Midpiece

•contains mitochondria for energy

Tail (flagellum)

•propels the sperm with a lashing motion (speed: about 3mm/hr)

Sperm and the Scrotum

Sperm production occurs at ~ 35°C

(which is a few degrees lower than

body temperature) so the scrotum

holds the testes outside of the body

to facilitate sperm development at

this lower temperature

Sex Characteristics

The chromosome

combination that results in an

offspring that is

• genetically male: XY

• genetically female: XX

Male Reproductive Negative Feedback Loop

LH → interstitial cells →

testosterone

FSH → Sertoli cells

(seminiferous tubules) →

sperm

2 hormones that affect spermatogensis

-testosterone and FSH

Andropause

-Occurs around age 40 when testosterone levels begin to decrease

Symptoms: fatigue, depression, loss of muscle/ bone loss, decreased sperm production

Treatment: low doses of testosterone

Prostate Enlargement

FYI: Hormonal changes can lead to the enlargement of the prostate gland as the male ages.

Symptoms: discomfort, urinary difficulties (prostate squeezes on urethra) such as

burning sensation when peeing or frequent urination

Treatment: surgery (if cancerous); antibiotics (to reduce inflammation of prostate =

prostatitis)

Diagnosis: digital rectal exam, PSA (enzyme) test