Anatomy Unit 201: Cell Cycle and Gametogenesis

Cell Cycle and Gametogenesis

• Understanding cell cycle includes growth, repair, and reproductive processes.
• Mitosis occurs in somatic cells for growth and maintenance, while meiosis is for gamete formation.

Mitosis vs. Meiosis

• Mitosis results in two identical cells; meiosis results in four genetically diverse gametes.
• Meiosis includes two stages: Meiosis I (reduction division) and Meiosis II (equatorial division).

Importance of Meiosis

• Reduces diploid chromosome number to haploid.
• Facilitates genetic diversity through shuffling of chromosomes and crossing over.

Spermatogenesis

• Definition: Transformation of spermatogonia to spermatozoa.
• Location: Occurs in the seminiferous tubules of the testes.
• Duration: Approximately 64 days; begins at puberty and continues throughout life.
• Includes two main steps: spermatocytogenesis (division to form spermatids) and spermiogenesis (maturation of spermatids).

Seminal Fluid

• Composed of sperm and secretions from multiple male reproductive glands.
• Volume: 3-5cc with a characteristic odor; alkaline reaction to neutralize vaginal acidity.
• Contains fructose for sperm nutrition and prostaglandins for motility.
• Healthy sperm count: 200-600 million with over 80% motility.

Abnormalities of Seminal Fluid

• Azospermia: absence of sperm.
• Oligospermia: low sperm count.
• Necrospermia: presence of dead sperm.
• Abnormal sperm shapes can include giant, dwarf, or multi-headed/tail structures, not exceeding 20% of total count.

Oogenesis

• Definition: Transformation of oogonia into mature ova.
• Location: Outer cortex of the ovaries.
• Primary oocytes initiate meiosis before birth but pause in prophase until puberty.
• Monthly, 5-12 primary oocytes resume meiosis, creating a secondary oocyte and a polar body.

Oogenesis Process

• At ovulation, the secondary oocyte undergoes the second meiotic division, arrested at metaphase until fertilization.
• Newborn females have about 2 million primary oocytes; this number decreases to around 40,000 at adolescence.
• Approximately 480 oocytes are ovulated throughout reproductive life.

Comparative Overview of Spermatogenesis and Oogenesis

• Spermatogenesis produces many sperm cells continuously, while oogenesis results in a limited number of ova, with significant pauses in development.
• Each male gamete is equal in size and morphology, while female gametes maintain a larger size with polar bodies formed during division.

Case Scenario Reflection

• Oogonia enter meiosis I and replicate DNA to form primary oocytes during fetal life, highlighting the significance of developmental timing in gametogenesis.

This quiz delves into the intricacies of the cell cycle, focusing on the processes of mitosis and meiosis. It examines the differences between these types of cell divisions and explores gametogenesis, particularly spermatogenesis and oogenesis. Prepare to differentiate and compare these critical biological processes.