Paper on This Type of Stuff

Lecture: Reproductive Physiology

I. Spermatogenesis: Sperm Production in Seminiferous Tubules

A. From Spermatogonia to Spermatids (occurs in seminiferous tubules of testes)

basal lamina spermatogonia ("germ cell") ->

Type A daughter cell (remains on wall)

Type B daughter cell (spermatogenesis) ->

primary spermatocyte (meiotic divisions) ->

2 secondary spermatocytes (meiosis I) ->

lumen 4 spermatids (each haploid "n")

B. Spermiogenesis: From Spermatid to Spermatozoon

1. acrosome - package of enzymes at top of sperm; allows penetration of the eggs for fertilization

2. nucleus - positioned in "head" of sperm along just behind acrosome; allows for delivery of DNA to egg

3. tail - microtubules arrange into 9+2 configuration to form "flagellum" for locomotion

4. mitochondria - located around the base of the tail; provide ATP for the swimming motion

5. cytoplasm - excess cytoplasm in "sloughed off"

C. The Role of Sustentacular Cells (Antigen Barrier)

1. sustentacular cells (Sertoli cells) - with tight junctions, divide the seminiferous tubule into "basal compartment" and "adluminal compartment"

a. blood-testis barrier - these cells prevent leakage of proteins from "new genetic cells" (from crossing over) to stimulate an autoimmune response, which would kill the gametes

b. absorb excess cytoplasm "sloughed off"

c. chemical signals that regulate entire process

D. Effects on Spermatogenesis and Fertility

1. autoimmune disorder - immune system attacks "new" sperm cells which are different from somatic cells due to crossing over during mitosis

2. other factors: radiation, lead poisoning, some pesticides, marijuana, alcohol can lead to abnormal sperm...