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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