Animal Tissues and Epithelial Functions

Study Notes

Cells organize into tissues, which combine to form organs.
Tissues are classified into four main types based on cell function and structure.

Composed of closely packed cells with one side exposed to air or fluids and the other attached to a basement membrane.
Acts as a barrier against mechanical injury, pathogens, and dehydration.
Functions in absorption, secretion, and transport of substances.
Examples include skin and lining of various organs.

Cell Shape:
- Squamous: flat cells for diffusion and transport.
- Cuboidal: cube-shaped cells for secretion.
- Columnar: tall, brick-shaped cells for secretion and absorption.
Cell Layers:
- Simple: single layer of cells.
- Stratified: multiple layers of cells for protection.
- Pseudostratified: appears layered but is a single layer, often with cilia.
Simple Cuboidal Epithelium:
- Found in surfaces such as ovaries, kidney tubules, and glands.
- Main function is secretion.
Simple Columnar Epithelium:
- Located in the digestive tract and uterine lining.
- Serves in secretion and absorption.
Simple Squamous Epithelium:
- Present in capillaries and alveoli.
- Facilitates material exchange by diffusion.
Stratified Squamous Epithelium:
- Multilayered and keratinized for protection.
- Found in skin and mucosal surfaces of the mouth and esophagus.
Pseudostratified Columnar Epithelium:
- Found in respiratory tracts like the trachea and bronchi.
- Often has cilia for mucus movement.

Comprises fibrous cells that provide structural support and binding for other tissues.
Characterized by a large extracellular matrix that includes fibers and a non-living matrix.

Blood:
- Composed of plasma (liquid matrix), erythrocytes (RBCs for oxygen transport), leukocytes (WBCs for immune defense), and platelets (for clotting).
- Unique as a fluid connective tissue.
Connective Tissue Proper (CTP):
- Includes loose connective tissue with collagen fibers.
- Found in tendons and ligaments, providing structural integrity.
Adipose Tissue:
- A type of loose connective tissue that stores fat for insulation and energy.
Cartilage:
- Contains collagenous fibers embedded in a chondroitin sulfate matrix for cushioning.
- Cells called chondrocytes secrete these components.
Bone:
- Mineralized connective tissue formed by osteoblasts that deposit collagen.
- Provides body framework, combining collagen with minerals like calcium for hardness.

Composed of long muscle fibers, responsible for movement through contraction.
Categories include:
- Skeletal Muscle: Striated appearance, voluntary control, comprises 30-40% of body mass.
- Cardiac Muscle: Striated and involuntary, found in the heart.
- Smooth Muscle: Non-striated and involuntary, located in walls of hollow organs.