2- Spermatogenesis 3

Male Genital System Overview

• Composed of the following structures:

  • Testicles

  • Ducts

  • Accessory glands

  • Scrotum

  • Penis

  • Pubic bone

  • Urethra

Gametogenesis

• Refers to the process of forming male and female gametes from germ cells.

Germ Cell Migration

• In early mammalian development, primordial sex cells migrate to embryonic gonads (testicles and ovaries).

• They reproduce to form gametes (spermatozoon and ovum).

Germ Cells vs. Soma Cells

• Germ cells are involved in gamete formation.

• Soma cells, or somatoplasm, do not directly influence gametogenesis.

Gametogenesis Stages

1. Origin and Migration: Germ cells originate and migrate to gonads.

2. Mitosis: Germ cells reproduce through mitosis.

3. Meiosis: Chromosome number is halved to produce gametes.

4. Maturation: Gametes undergo final maturation, developing into sperm or ova.

Mitosis in Germ Cells

• Mitosis occurs in different patterns between males and females:

  • In females, high mitotic activity occurs during 2nd to 5th month of pregnancy, resulting in numerous ovogonium.

  • In contrast, males maintain continuous mitotic activity throughout life, producing spermatogonia.

Meiosis in Gametogenesis

• Meiosis is a type of cell division that reduces genetic material.

• Results in the formation of haploid gametes (1n).

• Involves two nuclear divisions with only one DNA replication.

Meiosis I and II

• Meiosis I includes phases: Prophase I, Metaphase I, Anaphase I, Telophase I, Interphase.

• Meiosis II leads to formation of spermatids or ova and polar bodies.

Testes Structure

• Testicles are located in the scrotum, which maintains lower temperatures necessary for spermatogenesis.

• Anatomical Layers:

  • Tunica Vaginalis: Surrounds and supports the testes.

  • Tunica Albuginea: A durable capsule composed of fibrous connective tissue.

Lobular Structure

• Testes contain approximately 300 lobules housing seminiferous tubules (tubulus seminiferus contourus).

  • Around 1-4 seminiferous tubules per lobule.

Leydig and Sertoli Cells

• Leydig Cells: Found in interstitial tissue, secrete hormones (e.g., testosterone).

• Sertoli Cells: Support and nourish spermatogenic cells; play a crucial role in forming the blood-testis barrier and regulating spermatogenesis.

Sperm Morphogenesis

• Spermiogenesis: Involves development of spermatozoa from spermatids; includes:

  • Formation of acrosome

  • Condensation of chromatin

  • Development of a tail

Sperm Structure

1. Head: Contains the nucleus and acrosomal cap for fertilization.

2. Neck: Junction between the head and tail, houses centrioles.

3. Middle Piece: Contains the mitochondria for energy.

4. Principal Piece: Longest part of the tail with spiral filaments.

5. End Piece: Concludes the sperm's structure.

Epididymis and Ductus Deferens

• Structures for transferring and maturing spermatozoa:

  • Consists of convoluted duct leading to the ductus deferens.

  • Takes around 10-15 days for sperm to mature from production to storage.

Accessory Glands

• Glandula Vesiculosa: Enriches ejaculate with nutrients for sperm.

• Prostate Gland: Contributes to seminal fluid and aids in sperm motility.

• Bulbourethral Gland: Pre-ejaculatory function, lubricates and neutralizes urethra.

Urethra Structure

• Comprises three distinct segments: prostatic, membranous, and spongy urethra.

• Functions in expulsion of urine and seminal fluid during ejaculation.