The male reproductive system

Humans have 2 types of gametes:Males have sperm – small,

motile, manyFemales have eggs – large,

non-motile, fewMale and female reproductive

systems are designed to maximize chance of fertilization

Sperm production and maturation:Testes (spermatogenesis and testosterone)

Inside scrotumBegin development inside abdomen,

only descending into scrotum in the last 2 months of gestation

Contain seminiferous tubules – sperm cells are made here (spermatogenesis)

Sertoli cells nourish sperm cells

Acrosome contains enzymes that allow sperm to penetrate egg

Head has DNA and nucleus

The tail is also called a flagellum (for swimming)

Interstitial cells: lie between seminiferous tubules

Produce androgens (male hormones) (mainly testosterone)

Testosterone involved in spermatogenesis, and maturation of testes and penis at puberty

Brain break

Why does it take 300 million sperm to fertilize one egg?

Because they won't stop to ask directions.

Epididymis

Where sperm matureTightly coiled tubule (about 20 ft

long)Just outside each testisBelieved that some defective cells

are destroyed here by the immune system

Transport: ductus deferens (vas deferens)

Joined to epididymisGoes from testes, through inguinal

canal and into abdomen to the urethraWhat they cut in a vasectomy to

sterilize a manA hernia is what happens when

inguinal canal gets stretched and a bit of intestine squishes through. Can get painful and sometimes strangulated (circulation cut off)

Seminal fluids

Three glands contribute to seminal fluid for sperm to swim in

Seminal fluid + sperm = semen1: Prostate gland: alkaline fluid to

protect sperm while in the female2: seminal vesicles: sugar solution

for energyProstoglandins: cause contractions

of female reproductive muscles3: Cowper’s glands: lubricating fluid

Penis Copulatory organ Has enlarged end (glans penis) covered in foreskin

at birth (gets “smegma” if you don’t clean under it)

Can be removed by circumcision Contains urethra, which is path taken by sperm

during intercourse During erection, sphincter from bladder closed off

so no entry of urine Penis fills with blood (in blood sinuses) and

becomes erect Impotency: inability to get an errection (sometimes

psychological, sometimes hormone imbalance) Deposits 150 – 300 million sperm outside cervix of

female

Ejaculation

Process by which semen leaves a man’s body via the penis

Path of sperm:Epididymis vas deferens

(seminal fluid comes form the 3 glands) urethra vagina