Chapter 3 - Tissues
1. Introduction
Main tissue types: Epithelial, Connective, Muscle, Nervous
Functions:
Protection, secretion, absorption, connection, movement, information processing
Tissue membranes:
Epithelial membranes: Mucous, Serous, Cutaneous
Connective tissue membranes: Synovial membranes (joints)
2. Types of Tissues
Four categories:
Epithelial: Covers surfaces, lines cavities
Connective: Supports, connects, transports
Muscle: Enables movement
Nervous: Sends and receives signals
Embryonic origin: Derived from ectoderm, mesoderm, endoderm
3. Epithelial Tissue
Characteristics:
Closely packed cells, avascular, polarity (apical/basal surfaces), rapid regeneration
Cell Junctions:
Tight junctions: Barrier function (e.g., intestines)
Anchoring junctions: Stability (e.g., skin)
Gap junctions: Communication (e.g., heart)
Types:
Simple (one layer) vs Stratified (multiple layers)
Shapes: Squamous (flat), Cuboidal (cube-shaped), Columnar (tall)
Specialized types:
Pseudostratified: Appears layered but isn’t
Transitional: Stretchable (e.g., bladder)
Glands:
Endocrine (ductless, secretes hormones into bloodstream)
Exocrine (ducts, secretes onto surfaces)
Modes of secretion:
Merocrine: Exocytosis (e.g., sweat glands)
Apocrine: Pinched off portion of cell (e.g., mammary glands)
Holocrine: Entire cell disintegrates (e.g., sebaceous glands)
4. Connective Tissue
Structure:
Cells dispersed in extracellular matrix (ground substance + protein fibers)
Fiber types:
Collagen (strong, flexible)
Elastic (stretchy)
Reticular (supportive framework)
Categories:
Proper:
Loose (Areolar, Adipose, Reticular)
Dense (Regular, Irregular, Elastic)
Supportive:
Cartilage (hyaline, elastic, fibrocartilage)
Bone (osteocytes in lacunae, vascularized)
Fluid:
Blood (RBCs, WBCs, plasma)
Lymph (immune function)
Functions: Structural support, transport, immune defense, energy storage
5. Muscle Tissue
Properties: Excitable, contractile
Types:
Skeletal: Striated, voluntary, attached to bones
Cardiac: Striated, involuntary, heart muscle (intercalated discs)
Smooth: Non-striated, involuntary (digestive, respiratory, reproductive systems)
6. Nervous Tissue
Function: Conducts electrical impulses, processes information
Cell types:
Neurons: Transmit signals (axon, dendrites)
Neuroglia: Support, protect, nourish neurons
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