Anatomy Unit 201: Cell Cycle and Gametogenesis

Cell Cycle and Gametogenesis

• Comprised of mitosis and meiosis, focused on cell division and differentiation of gametes.
• Mitosis occurs in somatic cells for growth and repair; meiosis produces haploid gametes.

Mitosis vs. Meiosis

• Mitosis results in two identical diploid cells, essential for growth.
• Meiosis is a reduction division resulting in four non-identical haploid gametes.
• Meiosis I involves DNA replication, crossing over, and results in two cells; Meiosis II resembles mitosis without DNA replication.

Importance of Meiosis

• Reduces diploid chromosome number to haploid, promoting genetic diversity.
• Facilitates shuffling of chromosomes from maternal and paternal origins, enhancing variation.
• Crossing over during meiosis redistributes genetic material, crucial for evolution.

Spermatogenesis

• Transformation of spermatogonia into spermatozoa occurring in seminiferous tubules.
• Takes approximately 64 days and begins at puberty (ages 13-16).
• Involves spermatocytogenesis (division) and spermiogenesis (maturation).

Seminal Fluid

• Composed of sperm and secretions from reproductive glands (epididymis, prostate, seminal vesicles).
• Normal volume is 3-5cc, characterized by its alkaline reaction and distinct odor.
• Contains nutrients like fructose for sperm survival and prostaglandins to enhance motility.

Abnormalities of Seminal Fluid

• Azospermia: Absence of sperm.
• Oligospermia: Low sperm count.
• Necrospermia: Presence of dead sperm.
• Abnormal shapes include giant or dwarf sperm, which should not exceed 20%.

Oogenesis

• Transformation of oogonia into mature ova occurs in the ovarian cortex.
• Primary oocytes begin meiotic division before birth but remain arrested until puberty.
• Each month, 5-12 primary oocytes resume meiosis, creating a secondary oocyte and a first polar body.

Timing of Oogenesis

• Approximately 2 million primary oocytes at birth, decreasing to about 40,000 by adolescence.
• Around 480 secondary oocytes are released during a woman's reproductive years.

Comparison of Male and Female Gametogenesis

• Spermatogenesis produces numerous sperm continuously from puberty, while oogenesis results in a limited number of ova released cyclically.
• Spermatogenesis leads to four functional sperm per cycle; oogenesis typically results in one mature ovum per cycle, with polar bodies considered non-functional.

Case Scenario

• Oogonia enter meiosis I and replicate DNA to form primary oocytes during fetal life.
• Understanding the timing of gamete development is fundamental in physiology.

This quiz covers the fundamental concepts of the cell cycle, including the processes of mitosis and meiosis. It also explores the differences between these two types of cell division and delves into gametogenesis, focusing on spermatogenesis and oogenesis. Test your understanding of these critical biological processes.