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.
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:
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).
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.
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.
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.