Recording-2025-02-24T20:23:04.294Z

Intermediate Filaments

• Definition: Intermediate filaments are strong, ropelike structures made of various metal wires twisted together, contributing to the cell's cytoskeleton.

• Properties:

  • Tensile Strength: They possess great tensile strength, meaning they do not easily pull apart or stretch.

  • Functions:

    • Anchor the nucleus, preventing it from moving around within the cell.

    • Important for the survival of the cell, as the nucleus contains genetic material.

• Keratin:

  • A type of intermediate filament found in hair, skin, and nails, keratin provides strength and helps protect the skin surface.

• Histology:

  • Recognizable tissue: Keratinized stratified squamous epithelium.

  • As skin cells move outward, they become keratinized, meaning they fill with keratin and lose their nuclei, resulting in a protective, dead layer on the surface of the skin.

Microtubules

• Definition: Microtubules are made from a protein called tubulin and are analogous to Lego bricks; they can easily assemble and disassemble.

• Functions:

  • Essential for cellular organization and transport.

  • Transport organelles such as ribosomes, lysosomes, and vesicles through the cell.

  • Movement during cell division (mitosis and meiosis) via spindle apparatus formation.

• Centrosome and Centrioles:

  • The centrosome directs the assembly/disassembly of microtubules in animal cells.

  • Centrioles (found in animal cells but not in plants) consist of microtubule triplets arranged at right angles.

Cilia and Flagella

• Cilia:

  • Short, hairlike structures that move in a wave-like fashion.

  • Function similarly to oars; they can move mucus (e.g., in the respiratory tract).

  • Example: Pseudostratified ciliated columnar epithelium in the trachea helps move mucus up and away from the lungs to trap pathogens and particles.

• Flagella:

  • Longer, whip-like structures that propel cells through their environment.

  • The only human cells with flagella are sperm cells.

• Cell Movement:

  • Cilia function to move both mucus and reproductive cells (e.g., ova in fallopian tubes and sperm in male reproductive tract).

Sperm Cell Mechanics

• Cilia's Role in Reproduction:

  • Cilia move sperm through the male reproductive tract until they are ready to swim immediately before ejaculation.

• Energy Supply:

  • Mitochondria within the flagellum provide ATP necessary for movement. Sperms have a unique energy source: fructose added by seminal vesicles.

Fertilization Process

• Only one sperm generally fertilizes an egg (ovum).

• First sperm that reaches the egg starts digesting through the outer layers, allowing another sperm to penetrate and achieve fertilization.

• Importance of the mucus: It guides sperm towards the ovum, with the strongest concentration of hormones at the ovum directing sperm movement.

Challenges in Reproductive Survival

• The female immune system significantly reduces participating sperm, eliminating weaker cells in the process.

• Mutliple sperm may enter the uterus, but only the most viable will fertilize as they navigate through various barriers.