Outline-2, BIO 3220, Reproductive System


A. Development of gonads

1. Genital ridges – Form gonads, just medial to kidneys

2. Germinal epithelium – Forms gametes


1. Testes

a. Seminiferous tubules – Coiled tubules lined with germinal epithelium and formation of sperm in most vertebrates.

b. Some fish, cyclostomes, urodeles – Lack seminiferous tubules; sperm are made within cysts

c. Position

1. Abdominal cavity – Monotremes, elephants, whales, non-mammals

2. Descended permanently – ungulates, carnivores, humans

3. Retractile – rabbit, lower primates

2. Vasa efferentia – Closed system

3. Vas deferens = Spermatic duct = Mesonephric duct

4. Cloaca – below placental mammals

5. Urethra = Urogenital sinus – placental mammals

6. Copulatory organs – Needed for internal fertilization

a. Claspers – elasmobranchs – Pelvic fin modification

b. Gonopodium – teleosts – Anal fin modification

c. Hemipenes – snakes, lizards

d. Penis

1. Turtles, crocs, monotremes, some birds – Thickening on floor of cloaca

2. Placental mammals – External, erectile tissue


1. Ovary

a. Hollow, but lined with germinal epithelium – teleosts

b. Thin-walled sacs – anurans, urodeles

c. Lacunae, fluid filled – Reptiles, birds, monotremes

d. Solid

1. Mammals

2. Follicles – “Bag”; Egg plus surrounding fluid & cells

e. Ovulation into coelom – open system

2. Oviducts, Uterus, Vagina

a. Development

-From Muellerian Ducts [uterus & vagina too] in most

b. Below placental mammals – Empty to cloaca

c. Placental mammals

1. Uterus

a. Marsupials (2)

b. Horns – Most placental mammals have extensions of uterine body, called horns, for multiple births.

c. Cervix – Caudal muscular opening into uterus

2. Vagina

a. Urogenital sinus – Vagina, a cloacal derivative, empties into the urogenital sinus in most placental mammals

b. Exterior genitals = Vulva – In rodents and primates, the vagina opens directly to the vulva

D. Cloaca

1. The cloacal opening, or vent, receives intestine and urogenital structures in all vertebrates except placental mammals.

2. Urorectal fold – A horizontal shelf starts to divide the cloaca in reptiles, birds and monotremes

a. Coprodeum – Collects digestive waste

b. Urodeum – Collects urine

c. Proctodeum – Common, undivided, terminal cloaca

3. Urogenital sinus and Rectum in placental mammals except primates & rodents

4. Urethra, Vagina, Rectum (female primate, rodents)