Anatomy and Physiology I: Tissue Overview

Cell Biology and Tissue Overview

• Histology: Study of tissues; defined as collections of cells with similar structures and functions.

• Four Basic Types of Tissues:

  • Epithelial

  • Connective

  • Muscle

  • Nervous

Cell Junctions

• Types of Cell Junctions:

  • Desmosomes: Provide mechanical strength, found in high-stress tissues like skin.

  • Hemidesmosomes: Anchor cells to extracellular matrix.

  • Tight Junctions: Form watertight seals; prevent leakage (e.g., intestine lining).

  • Gap Junctions: Allow direct communication between cells.

Glands

• Endocrine Glands: Release hormones into the bloodstream (no ducts).

• Exocrine Glands: Release secretions via ducts.

Epithelial Tissue

• Characteristics:

  • Avascular, anchored to basement membrane.

  • Functions: protection, absorption, secretion.

• Classification:

  • By Layers: Simple (1 layer) or Stratified (multiple layers).

  • By Shape: Squamous (flat), Cuboidal (cube-shaped), Columnar (tall).

Types of Epithelial Tissue

• Simple:

  • Squamous: Lungs, blood vessels.

  • Cuboidal: Ovaries, kidney tubules.

  • Columnar: Digestive tract, respiratory tract (often with microvilli or cilia).

• Stratified:

  • Squamous: Skin, mucous membranes.

  • Columnar: Rare, found in certain areas.

  • Transitional: Bladder, can stretch.

Connective Tissue

• Definition: Consists of cells and an extracellular matrix.

• Components:

  • Protein fibers (mainly collagen), ground substance, possibly fluid.

• Functions: Support, connections, protection, storage (e.g., adipose tissue).

• Types:

  • Loose (Areolar, Adipose)

  • Dense (Tendons, Ligaments)

  • Specialized (Cartilage, Bone, Blood).

Muscle Tissue

• Types:

  • Striated (Skeletal): Voluntary, striated, attached to bones.

  • Cardiac: Involuntary, striated, found only in the heart.

  • Smooth: Involuntary, non-striated, in walls of hollow organs.

Nervous Tissue

• Composed of neurons and glial cells; responsible for transmitting nerve impulses.

Membranes

• Sheets of tissues covering organs. Types include:

  • Mucous

  • Serous

  • Synovial

  • Cutaneous

Integumentary System

• Components: Skin (largest organ), including the epidermis, dermis, and hypodermis.

• Functions: Protection, sensation, temperature regulation.

• Skin Layers:

  • Epidermis: Avascular, five layers including the stratum corneum.

  • Dermis: Vascular, houses glands and sensory receptors.

  • Hypodermis: Mainly adipose tissue, provides insulation.

• Skin Color Factors: Melanin (UV protection), carotene, blood flow.

Temperature Regulation via Skin

• Mechanisms: Vasoconstriction, vasodilation, sweat secretion.

• Reactions to Temperature Change: Blood flow adjustments to conserve or lose heat.