Lecture 12: Spermatogenesis pt I

What part of the testes do functional sperm get dumped into

Rete testes of the mediastinum

What compartment of the seminiferous tubule is in direct contact with the circulatory system

Basal compartment

List the four stages of spermatic germ cells

1. Spermatogonia
2. Spermatocyte
3. Spermatid
4. Spermatozoa

Review: describe mitosis

1. DNA replicates
2. 4n parent cell splits
3. 2 2n daughter cells produced (proliferation)

Review: describe meiosis

1. DNA replicates
2. 4n parent cell splits
3. 2 2n daughter cells split
4. 4 1n daughter cells produced

Why are the meiotic spermatic germ cells not in contact with the circulatory system

The body would attack and destroy them because they don’t have the right number of chromosome pairs (1n instead of 2n)

List the stages of spermatogenesis

1. Proliferation
2. Meiosis
3. Differentiation

In what compartment is proliferation happening

Basal compartment

In what compartment are meiosis and differentiation happening

Adluminal compartment

Which of the sperm precursors is 2n, in contact with the circulatory system (basal compartment) and undergoing proliferation (mitosis)

Spermatagonia

Which of the sperm precursors is 4n and undergoing meiosis

Spermatocyte

Which sperm precursor is 1n, and undergoing differentiation

Spermatid

List the four steps of differentiation from spermatid to spermatozoa

1. Golgi
2. Cap
3. Acrosomal
4. Maturation

Describe the Golgi phase of differentiation

* Round spermatid with very active Golgi Apparatus
* Golgi secretes proacrosomic vesicles, around granules, that coalesce on top of the nucleus
* Centrioles move to the pole opposite the vesicles

Describe the two types of centrioles from the Golgi Phase

* Proximal centriole: arrives first, becomes tail attachment point
* Distal centriole: arrives second, becomes the skeleton for the tail (axoneme)

Describe the Cap phase of differentiation

* Distal centriole unwinds toward the lumen to form the axoneme
* Acrosome flattens over nucleus, inner and outer membrane formed

Describe the Acrosomal phase of differentiation

* Nucleus, and acrosome covering it, elongates
* Microtubules, called the manchette, hold acrosome on top of the nucleus
* Annulus forms the joint between the mid and principle tail pieces

Describe the Maturation phase of differentiation

* Manchette now called post nuclear cap
* Excess cytoplasm is exocytosed
* Mitochondria gathered into midpiece, segmented off by annulus