1. Sex Determination in Humans

2. Male Reproductive System
Sperm are produced in seminiferous tubules.
Leydig cells, located in interstitial tissue between seminiferous tubules (50 days), secrete testosterone (70 days).
Converts indifferent structures into male external genitalia (penis and scrotum).
In an adult, each testis is composed primarily of seminiferous tubules.
testes descend into scrotum
maintains slightly lowered temperature

3. Human Male Reproductive System

4. Male Reproductive System
Production of sperm
Wall of seminiferous tubule consists of germinal cells which become sperm, by meiosis, and supporting Sertoli cells (secrete products required for spermatogenesis, also engulfs the extra cytoplasm in spermatids).
Each parent cell undergoes mitosis, and one of the two daughter cells then undergoes meiosis to form sperm.

5. Male Reproductive System
Diploid daughter cell - primary spermatocyte
First meiotic division produces two haploid secondary spermatocytes.
Each undergoes second meiotic division to separate the chromatids and produce two haploid cells, spermatids.
Total of four haploid spermatids produced by each primary spermatocyte.

6. Testis and Spermatogenesis

7. Male Reproductive System
Spermatozoa
Head encloses nucleus and capped by an acrosome - contains enzymes that aid in egg penetration.
body and tail provide propulsion

8. Male Reproductive System
Male accessory sex organs
Epididymis (sperm not motile for 18 hrs)
vas deferens
seminal vesicles (fructose rich fluid, 60% sv)
prostate gland (30%sv)
Urethra

9. Male Reproductive System
Male accessory sex organs
erectile tissue
corpora cavernosa - dorsal side
corpora spongiosum - ventral side

10. Male Reproductive System
Hormonal control of male reproduction
FSH stimulates the Sertoli to facilitate sperm development.
LH stimulates Leydig cells to secrete testosterone.
Principle negative feedback inhibition applies to FSH and LF secretion.

11. Hormonal Interactions