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.

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