Tissue Types and Their Functions

Major Functional Differences Among Tissue Types

• Four primary tissue types: epithelial, connective, muscle, nervous.
• Epithelial Tissue: Protection, absorption, secretion, sensation.
• Connective Tissue: Support, binding other tissues, storing energy, transporting substances.
• Muscle Tissue: Movement through contraction, includes skeletal, cardiac, and smooth muscle.
• Nervous Tissue: Transmits electrical impulses, processes information, supports neurological functions.

Structure and Function of the 5 Types of Epithelia

• Simple Squamous: Thin, flat cells; allows for diffusion and filtration.
• Simple Cuboidal: Cube-shaped cells; functions in secretion and absorption (found in glands).
• Simple Columnar: Tall, column-like cells; absorbs nutrients and produces mucus.
• Stratified Squamous: Multiple layers of cells; provides protection against abrasion (skin).
• Pseudostratified Columnar: Appears layered due to varying cell heights; involved in secretion and movement of mucus.

Anatomical Organization of Epithelial Tissue

• Composed of closely packed cells, minimal extracellular matrix.
• Cells are polarized with an apical surface (exposed to environment) and a basal surface (attached to basement membrane).
• Basal lamina supports and anchors the epithelium to underlying connective tissue.

Structural and Functional Differences: Endocrine vs Exocrine Glands

• Endocrine Glands: Ductless; secrete hormones directly into the bloodstream, regulating various bodily functions.
• Exocrine Glands: Have ducts; secrete substances (e.g., enzymes, sweat) onto epithelial surfaces or into cavities.

Structure and Function of Glands

• Unicellular Glands: Single-celled (e.g., goblet cells); produce mucus, important for lubrication and protection.
• Multicellular Glands: Composed of multiple cells; can be categorized based on duct structure (simple or compound) and secretory unit shape (tubular or acinar).

Cell Connections

• Tight Junctions: Seal adjacent epithelial cells to prevent substance passage.
• Desmosomes: Anchor cells together, providing mechanical strength.
• Gap Junctions: Allow for intercellular communication by connecting cytoplasms.

Structure and Function of Connective Tissue Types

• Loose Connective Tissue: Supports and binds other tissues; contains fibroblasts and macrophages.
• Dense Connective Tissue: Provides strength; comprises collagen fibers and is found in tendons and ligaments.
• Adipose Tissue: Stores energy and provides insulation; contains adipocytes.
• Cartilage: Flexible support; three types (hyaline, elastic, fibrocartilage) with varying structures and functions.
• Bone: Rigid support; highly vascularized, composed of osteocytes within a mineralized matrix.
• Blood: Fluid tissue; transports nutrients, gases, and waste; comprises red blood cells, white blood cells, and platelets.

Structure and Function of Nervous Tissue

• Composed of neurons and glial cells.
• Neurons transmit signals via electrical impulses.
• Glial cells support, nourish, and protect neurons.

Structure of a Neuron

• Cell Body (Soma): Contains nucleus and organelles; integrates signals.
• Dendrites: Receive inputs from other neurons; increase surface area for signal reception.
• Axon: Transmits impulses away from the cell body; can be myelinated (increases conduction speed) or unmyelinated.

Structure and Function of Muscle Types

• Skeletal Muscle: Striated, voluntary control; moves skeleton; multi-nucleated fibers.
• Cardiac Muscle: Striated, involuntary control; only found in the heart; intercalated discs facilitate contraction.
• Smooth Muscle: Non-striated, involuntary control; found in walls of hollow organs; spindle-shaped cells enable slow and sustained contractions.