unit 2 study guide

Anatomy and Physiology 1 (BSC2085) Unit 2 Study Guide: Chapters 4, 5 & 6

Chapter 4: Tissues

1. The Four Basic Tissue Types

  • Four primary types of tissue in the human body:

    • Epithelial

    • Connective

    • Muscular

    • Nervous

  • Note: Glandular tissue is not a basic tissue type but a function/derivative of epithelial tissue.

2. Epithelial Tissue

  • Function: Covers surfaces, lines cavities, and forms glands.

  • Key Characteristics:

    • Avascular: Lacks blood vessels but is richly innervated (has nerves).

    • Cellular Structure: Tightly packed cells with minimal extracellular space.

    • Basement Membrane: Rests on a basement membrane.

    • Regeneration Capacity: High regenerative capacity.

  • Cell Junctions: Specialized structures that connect epithelial cells:

    • Tight Junctions: Form a leak-proof seal, preventing substances from passing between cells.

    • Desmosomes: Act as "spot welds," providing mechanical strength to resist stress.

    • Gap Junctions: Allow direct communication and the transfer of ions and small molecules between cells.

    • Hemidesmosomes: Anchor the basal layer of epithelial cells to the underlying basement membrane.

3. Connective Tissue

  • Function: Supports, binds, and protects other tissues and organs.

  • Key Characteristic: Characterized by an abundant extracellular matrix (composed of fibers and ground substance), not by tight cell packing.

  • Fiber Types: The three major fibers include:

    • Collagen: Provides strength.

    • Elastic: Provides stretch.

    • Reticular: Forms a fine network for support.

4. Muscular Tissue

  • Function: Specialized for contraction to generate movement.

  • Types of Muscular Tissue:

    • Cardiac Muscle:

    • Found only in the heart.

    • Key identifying feature: Intercalated discs containing gap junctions for rapid electrical communication.

    • Involuntary Control: Not consciously controlled.

5. Nervous Tissue

  • Function: To receive, transmit, and process nerve impulses.

  • Key Characteristic: Contains excitable cells capable of generating action potentials.

  • Cell Types:

    • Neurons: Generate and conduct electrical signals.

    • Neuroglia (Glial Cells): Support, protect, and insulate neurons.

6. Tissue Repair & Embryonic Origin

  • Repair Types:

    • Regeneration: Replacement of damaged tissue with the same, functional tissue.

    • Fibrosis: Replacement of damaged tissue with scar tissue (composed of collagen fibers); more common when damage is severe.

  • Embryonic Origin: The mesoderm is the primary embryonic germ layer that gives rise to both connective tissue and muscular tissue.

Chapter 5: The Integumentary System (Skin)

1. System Components

  • The integumentary system includes:

    • Skin

    • Accessory Structures: Hair, nails, glands, and sensory receptors.

2. Layers of the Skin

  • Epidermis (Superficial Layer):

    • Stratum Lucidum: A thin, clear layer found only in thick skin (e.g., palms of hands, soles of feet).

    • Keratinocytes: The primary cell type; responsible for producing keratin, a tough protein that protects the skin.

    • Melanin: A pigment produced by melanocytes; functions in protecting DNA in skin cells from UV radiation.

  • Dermis (Deep to Epidermis):

    • Composed of connective tissue rich in collagen and elastic fibers, which provide strength and elasticity.

  • Hypodermis (Subcutaneous Layer):

    • Located deep to the dermis.

    • Composed of adipose and areolar tissue, serving as a fat storage reservoir and thermal insulator.

3. Glands of the Skin

  • Eccrine (Merocrine) Sweat Glands:

    • Most numerous; function in thermoregulation (cool body) and waste excretion.

  • Sebaceous Glands:

    • Oil-producing glands that secrete sebum into hair follicles to lubricate skin and hair.

  • Apocrine Sweat Glands:

    • Found in specific areas; associated with hair follicles.

4. Skin Functions

  • Protection: A physical barrier against pathogens and UV light (via melanin).

  • Temperature Regulation: Achieved through sweating and vasodilation/vasoconstriction of blood vessels.

  • Vitamin D Synthesis: Begins when UV rays activate a precursor molecule (7-dehydrocholesterol) in the epidermis.

  • Sensation: Contains sensory receptors for touch, temperature, pressure, and pain.

  • Note: The skin does NOT produce red blood cells; this occurs in the bone marrow.

5. Skin Pathology & Aging

  • Skin Cancer: The three major types are:

    • Basal Cell Carcinoma

    • Squamous Cell Carcinoma

    • Melanoma

  • Burn Assessment: The "Rule of Nines" is used to estimate the percentage of total body surface area affected by burns.

  • Bedsores (Decubitus Ulcers): Caused by prolonged pressure cutting off blood flow to an area.

  • Aging Effects: Include reduced elasticity (leading to wrinkles), thinner skin, and more brittle nails.

Chapter 6: The Skeletal System

1. Functions of the Skeletal System

  • Functions:

    • Support

    • Protection

    • Movement

    • Mineral Storage (Calcium & Phosphorus)

    • Blood Cell Production

  • Note: The skeletal system does NOT perform digestion.

2. Bone Anatomy

  • Parts of a Long Bone:

    • Diaphysis: The shaft of the bone.

    • Epiphyses: The ends of the bone.

    • Metaphyses: The regions between diaphysis and epiphysis.

    • Synovial Cavity: Part of a joint, not a long bone itself.

  • Coverings:

    • Periosteum: A fibrous membrane covering the outer surface of the bone.

  • Bone Marrow:

    • Red Marrow: Site of blood cell production (hematopoiesis).

    • Yellow Marrow: Found in the medullary cavity; stores triglycerides (fat).

3. Bone Tissue & Cells

  • Types of Bone Tissue:

    • Compact Bone: Dense and solid, structurally unit is the osteon (Haversian system).

    • Spongy (Cancellous) Bone: A porous, lattice-like network of trabeculae.

  • Bone Cells:

    • Osteoblast: The "bone-building" cell; secretes bone matrix for formation.

    • Osteocyte: A mature osteoblast that has become trapped in the matrix; maintains the bone tissue.

    • Osteoclast: The "bone-resorbing" cell; breaks down bone to release calcium into the blood.

4. Bone Development & Growth

  • Ossification: The process of bone formation.

    • Endochondral Ossification: Process where cartilage is replaced by bone; forms most bones, including long bones.

    • Intramembranous Ossification: Bone develops directly within mesenchyme; forms flat bones of skull and clavicle.

  • Growth: Bones lengthen at the epiphyseal plates (growth plates), which are layers of cartilage.

5. Bone Remodeling & Healing

  • Remodeling: A continuous, balanced process where osteoclasts resorb old bone and osteoblasts form new bone.

  • Hormonal Control:

    • Parathyroid Hormone (PTH): Increases blood calcium levels by stimulating osteoclast activity.

    • Calcitonin: Decreases blood calcium levels.

  • Fracture Repair (Phases):

    1. Reactive Phase: Hematoma forms at the fracture site.

    2. Reparative Phase: A fibrocartilaginous callus forms then replaced by a bony callus.

    3. Remodeling Phase: The bony callus is remodeled to its original shape.