Spermatogenesis

Overview

Introduction

A process by which spermatogonia develop into spermatozoa
- begins at puberty
- requires 64 days (approximately 2 months)
Broken down into
- spermatogenesis
  - the formation of spermatids from spermatogenic cells
- spermiogenesis
the process of spermatids maturing into mature sperm

Spermatogenesis

Spermatogenic cells are organized in poorly defined layers of progressive development between adjacent Sertoli cells in seminiferous tubules
Spermatogonia (2N), most immature spermatogenic cells, rest on basal lamina
- spermatogonia occupy basal compartment in seminiferous tubules
Spermatogonia (2N) divide by mitosis
- produces primary spermatocytes (2N)
Primary spermatocytes (2N) replicate DNA (4N)
- primary spermatocytes move across Sertoli cell – Sertoli cell junctional complexes into luminal compartment in seminiferous tubules
Primary spermatocytes (4N) divide by meiosis I
- produces 2 haploid secondary spermatocytes (2N)
- nondisjunction at this stage can lead to Klinefelter syndrome
Secondary spermatocytes (2N) divide by meiosis II
produces 4 haploid spermatids (1N)

Spermiogenesis

Spermatids (1N) differentiate into spermatozoa (1N) by an extensive remodeling process
Loss of cytoplasm, gain of acrosomal cap, and flagellum (tail)
- acrosomal cap develops via Golgi apparatus
flagellum (tail) develops via centrioles

Spermatozoa

Head