Cell Junctions and Tissue Types Quiz

Cell Junctions

• Cell junctions are contact points between plasma membranes of adjacent tissue cells.
• Five main types of cell junctions: Tight Junctions, Adherens Junctions, Desmosomes, Hemidesmosomes, and Gap Junctions.

Gap Junctions

• Comprised of connexons, facilitating rapid energy or electrical transfer between neighboring cells, functioning like "tunnels."

Tissue Types

• Four primary tissue types: Epithelial, Connective, Nervous, and Muscular.
• Tissues consist of groups of similar cells performing specific functions.

Epithelial Tissue

• Characterized by closely packed cells arranged in continuous sheets.
• Forms outer body coverings, lines cavities, and covers organs.
• Avascular and capable of rapid reproduction.

Surfaces of Epithelia

• Apical surface: Faces the body surface, both internally or externally.
• Basal surface: Adheres to the basement membrane.

Basement Membrane

• Comprises the basal lamina and reticular lamina, providing support and anchoring epithelial tissues.

Vascularity in Tissues

• Avascular tissues do not have a direct blood supply, while vascular tissues have their own supply.

Classification of Epithelia

• Classified by cell layers (Simple vs. Stratified) and cell shape (Squamous, Cuboidal, Columnar).
• Simple epithelium allows diffusion and absorption, whereas stratified epithelium provides protection.

Epithelial Shapes

• Squamous: Thin and flat cells.
• Cuboidal: Cube-shaped cells.
• Columnar: Tall, column-like cells.
• Transitional: Cells that change shape under different conditions.

Glandular Epithelium

• Composed of cells in clusters that produce secretions; categorized into endocrine and exocrine glands.

Endocrine vs. Exocrine Glands

• Endocrine glands secrete hormones directly into the bloodstream, bypassing ducts.
• Exocrine glands release secretions through ducts onto body surfaces or into cavities.

Gland Types

• Gland types include Tubular (tube-like), Acinar (round), and Tubuloacinar (both).

Modes of Secretion

• Merocrine: Glands secrete via vesicles (most common).
• Apocrine: Glands lose a portion of the cell during secretion.
• Holocrine: Entire cell ruptures, releasing its contents.

Connective Tissue

• The most abundant tissue type in the body, derived from mesenchyme, has a vascular supply, and is classified based on its composition.

Functions of Connective Tissue

• Provides protection, support, binding, insulation, and transportation.

Composition of Connective Tissue

• Consists of cells and an extracellular matrix, which includes ground substance and fibers.

Cell Types in Connective Tissue

• "Blast" cells are immature forms that typically secrete extracellular matrix components.
• "Cyte" cells are mature forms of connective tissue cells.

Types of Connective Tissue

• Includes Loose connective tissue (Areolar, Reticular, Adipose) and Dense connective tissue (Regular, Irregular, Elastic).
• Adipocytes specialize in energy storage through triglycerides.

Cartilage Types

• Hyaline cartilage: Most abundant, provides flexible support and reduces friction.
• Elastic cartilage: Strong and elastic.
• Fibrocartilage: Strongest type, lacks perichondrium.

Muscle Tissue

• Composed of three types: Skeletal, Cardiac, and Smooth.
• Skeletal muscle is striated, voluntary, and multinucleated; it attaches to bones.
• Cardiac muscle is striated, involuntary, and uninucleated; found in the heart.
• Smooth muscle is non-striated, involuntary, and uninucleated; located in the walls of hollow structures.

Nerve Tissue

• Composed of neurons and neuroglia.
• Neurons consist of a cell body, axon, and dendrites, functioning in signal transmission.
• Neuroglia includes protective and supportive cells for neurons.