Animal Organization and Homeostasis - Chapter 31

Animal Organization and Homeostasis

Tissue Overview

• Tissue: A group of similar cells that perform a common function.

Four Classes of Animal Tissue

1. Epithelial Tissue (Epithelium)

   • Covers body surfaces (external and internal).
   • Typically one to a few cells thick.
   • Functions:
     • Protects underlying tissues.
     • Provides sensory surfaces.
     • Secretes materials.
   • Types:
     • Simple Epithelia: Single layer thick, lines internal organs, allows for diffusion via squamous, cuboidal, and columnar cells.
     • Stratified Epithelia: Several layers thick (e.g., skin's epidermis) for protection.
     • Glandular Epithelia: Found in glands, secretes hormones, sweat, milk, saliva, and digestive enzymes.

2. Connective Tissue

   • Functions:
     • Provides structural support.
     • Defends the body.
     • Stores and distributes substances.
   • Types:
     • Immune Connective Tissue: White blood cells (leukocytes) in the bloodstream for defense.
     • Skeletal Connective Tissue: Cartilage (joint surfaces) and bone (major component of skeleton).
     • Transport and Storage Connective Tissue: Red blood cells (erythrocytes) and adipose tissue.
   • Categories:
     • Fibrous Connective Tissue: Includes loose, dense, and adipose connective tissues.
     • Supportive Connective Tissue: Bone and cartilage.
     • Fluid Connective Tissue: Blood and lymph.
   • Examples of Specific Tissues:
     • Loose Fibrous Connective Tissue: Provides support, found beneath the skin.
     • Adipose Tissue: Fat storage and insulation, found around the heart.
     • Dense Fibrous Connective Tissue: Closely packed collagenous fibers for support, found in tendons and ligaments.
     • Hyaline Cartilage: Cells in lacunae, found in the nose, respiratory passages, and bone ends; offers support and protection.
     • Compact Bone: Cells in concentric rings, forms the skeleton for support and protection.

3. Muscle Tissue

   • Function: Provides movement.
   • Types:
     • Skeletal Muscle: Aids in bone movement.
     • Cardiac Muscle: Pumps blood from the heart.
     • Smooth Muscle: Contracts slowly around organs.

4. Nervous Tissue

   • Function: Carries information rapidly throughout the body.
   • Composed of:
     • Neurons: Transmit nerve impulses (signals).
     • Glial Cells: Support neurons with nutrients and insulation.
   • Neuron Structure:
     • Cell Body: Contains the nucleus.
     • Dendrites: Receive signals.
     • Axon: Transmits signals away from the cell body.

Body Organization

• Tissues form Organs, which are structures made of several different tissues functioning together.
  • Examples: Heart (pumps blood), stomach (digests food), lungs (oxygen extraction), skin (protection).
• Organ Systems: Groups of organs working together to perform essential functions.
  • Examples: Circulatory system, digestive system, respiratory system, integumentary system.

Skin Structure

• Outer Layer: First line of defense against microbes, largest organ.
• Layers of Skin:
  • Epidermis: Outermost layer, 10-30 cells thick, continuously renews.
  • Dermis: Beneath epidermis, 15-40 times thicker, supports epidermis.
  • Subcutaneous Layer: Not part of skin, composed of adipose tissue for shock absorption and insulation.