Ch 1-3

Chapter 1: Epithelial Tissue

  • Polarity:

    • Apical surface: Faces the external environment or lumen; may have cilia (for movement) or microvilli (for absorption).

    • Lateral surface: Where cells connect with each other.

    • Basal surface: Anchors the tissue to the underlying connective tissue via the basal lamina.

  • Characteristics:

    • Attachment: Connected to a basement membrane.

    • Avascularity: Lacks blood vessels, so it gets nutrients by diffusion.

    • Regeneration: Cells divide rapidly for repair.

    • Cellularity: Cells are tightly packed with little extracellular material.

  • Cell Junctions:

    • Tight junctions: Seal between cells to prevent passage of substances.

    • Gap junctions: Allow ions/molecules to pass for communication.

    • Button desmosomes: Strong connections that resist stretching.

    • Hemidesmosomes: Anchor epithelial cells to the basement membrane.

  • Classification of Epithelial Cells:

    • Simple: One layer of cells.

    • Stratified: Multiple layers of cells.

  • Types of Epithelial Tissue & Functions:

    • Simple squamous: Thin, flat cells (like fried eggs); allows rapid diffusion.

      • Location: Air sacs of lungs, blood vessels, serous membranes.

    • Stratified squamous: Many layers; protects against abrasion.

      • Nonkeratinized: Found in moist areas (mouth, esophagus, vagina).

      • Keratinized: Found in the skin; has keratin for water resistance.

    • Simple cuboidal: Cube-shaped; involved in secretion & absorption.

      • Location: Kidney tubules, glands.

    • Simple columnar: Tall, narrow cells; absorption & movement.

      • Location: GI tract, uterine tubes, bronchioles.

    • Pseudostratified columnar: Looks layered but is actually one layer; often ciliated.

      • Location: Respiratory tract.

Connective Tissue

  • Functions: Provides support, binding, protection, and transport (e.g., blood).

  • Components:

    • Specialized Cells: Unique to each connective tissue type.

    • Fibers:

      • Collagen: Strong & flexible.

      • Reticular: Form a meshwork for support.

      • Elastic: Stretchy and resilient.

  • Types of Connective Tissue:

    • Loose Connective Tissue:

      • Areolar: Cushions organs, supports blood vessels & nerves.

      • Adipose: Stores fat, insulates, cushions.

    • Dense Connective Tissue:

      • Dense Regular: Parallel collagen fibers (tendons, ligaments).

      • Dense Irregular: Randomly arranged fibers (dermis, capsules of organs).

    • Fluid Connective Tissue:

      • Blood: Transports oxygen, nutrients, and immune cells.

    • Supporting Connective Tissue:

      • Cartilage:

        • Hyaline: Smooth, reduces friction (joints, ribs).

        • Elastic: Flexible (ear, epiglottis).

        • Fibrocartilage: Resists compression (intervertebral discs).

      • Bone: Hard, calcified matrix for support & protection.

Muscle Tissue

  • Functions: Contraction for movement.

  • Types:

    • Skeletal: Voluntary, striated, multinucleated.

    • Cardiac: Involuntary, striated, single nucleus, intercalated discs.

    • Smooth: Involuntary, non-striated, spindle-shaped cells (digestive tract, blood vessels).

Nervous Tissue

  • Function: Conducts electrical impulses for communication.

  • Cell Types:

    • Neurons: Transmit signals.

    • Neuroglia: Support, protect, and nourish neurons.

Review Questions & Answers

  1. Define homeostasis.
    → The body's ability to maintain a stable internal environment despite external changes.

  2. Why is homeostatic regulation important to an organism?
    → It keeps conditions optimal for survival, preventing damage from extreme changes.

  3. What is meant by dynamic equilibrium?
    → A state where internal conditions fluctuate within a normal range.

  4. Explain the function of negative feedback systems.
    → They maintain stability by reversing a change (e.g., body temperature regulation).

  5. What happens to the body when homeostasis breaks down?
    → It can lead to disease or death.

  6. Explain how a positive feedback system works. Why must it have a termination mechanism?
    → It amplifies a change (e.g., labor contractions). If uncontrolled, it can be harmful.

  7. Why is positive feedback helpful in blood clotting but unsuitable for regulating body temperature?
    → Clotting stops bleeding, but an unchecked temperature rise could be fatal.

  8. Identify stimulus, receptor, control center, effector, and response in a cold day scenario.

    • Stimulus: Cold temperature.

    • Receptor: Skin receptors.

    • Control center: Brain (hypothalamus).

    • Effector: Muscles (shivering) & blood vessels (vasoconstriction).

    • Response: Heat production & retention (negative feedback).

  9. Difference between intracellular and extracellular fluid?
    → Intracellular is inside cells; extracellular surrounds cells. Most water is intracellular.

  10. Differences in electrolytes between compartments?
    → Intracellular: More K⁺; Extracellular: More Na⁺.

  11. Common function of keratinized and nonkeratinized stratified squamous epithelium?
    → Protection.
    Structural difference: Keratinized has dead, toughened cells; nonkeratinized has live cells.

  12. How do the epithelia of the esophagus and stomach differ?
    → Esophagus: Stratified squamous (protection).
    → Stomach: Simple columnar (secretion & absorption).

  13. Compare tight & gap junctions.
    → Tight junctions prevent leakage; gap junctions allow communication.

  14. Common feature of connective tissue?
    → Cells surrounded by extracellular matrix.

  15. What is areolar tissue?
    → A loose connective tissue with fibers & cells in a gel-like matrix.

  16. Difference between dense regular & irregular connective tissue?
    → Regular: Parallel fibers (strong in one direction).
    → Irregular: Random fibers (strong in many directions).

  17. Three formed elements in blood & functions?

  • Red blood cells: Transport oxygen.

  • White blood cells: Fight infections.

  • Platelets: Help with clotting.

  1. Which heals faster: cartilage or bone? Stratified squamous or simple columnar? Why?

  • Bone heals faster (better blood supply).

  • Simple columnar heals faster (better nutrient diffusion & mitotic rate).

Chapter 2: Integumentary System, Membranes, Glands, Burns, and Cancer

Membranes

Membranes are made of epithelial tissue, connective tissue, or both.

  • Cutaneous membrane: The skin; made of keratinized stratified squamous epithelium and connective tissue.

  • Mucous membranes: Line cavities open to the outside (e.g., digestive, respiratory, urinary tracts); secrete mucus.

  • Serous membranes: Line internal body cavities (pleura, pericardium, peritoneum); secrete serous fluid for lubrication.

  • Synovial membranes: Found in joint cavities, secrete synovial fluid for lubrication.

Functions of the Skin

  1. Protection (against infection, dehydration, UV radiation)

  2. Sensation (touch, pressure, pain, temperature)

  3. Thermoregulation (sweating, blood vessel dilation/constriction)

  4. Vitamin D3 synthesis

  5. Excretion (sweat removes waste)

Epidermis

  • Avascular (relies on diffusion for nutrients).

  • Cells connected by desmosomes.

  • Composed of keratinized stratified squamous epithelium (keratinocytes).

Five Layers of the Epidermis (Deep to Superficial):

  1. Stratum basale

    • Stem cells: Divide to produce new keratinocytes.

    • Melanocytes: Produce melanin (pigment for UV protection).

    • Merkel cells: Sensory receptors for touch.

  2. Stratum spinosum

    • Dendritic cells (Langerhans cells): Immune response.

  3. Stratum granulosum

    • Keratin filaments: Strengthen cells.

    • Cells start to die and flatten.

  4. (Stratum lucidum) → Only in thick skin (palms, soles).

  5. Stratum corneum

    • Outermost layer of dead keratinized cells.

    • Protective, water-resistant barrier.

Skin Color

  • Melanin (produced by melanocytes, protects from UV damage).

  • Hemoglobin (gives skin a pinkish hue).

  • Cyanosis (bluish tint due to low oxygen in blood).

Vitamin D3 and the Epidermis

  • UV light stimulates Vitamin D3 (cholecalciferol) production.

  • Essential for calcium absorption in the intestines.

Dermis

Located between the epidermis and subcutaneous layer.

Two Layers of the Dermis:

  1. Papillary Layer

    • Contains papillary ridges (fingerprints).

    • Composed of areolar connective tissue.

  2. Reticular Layer

    • Made of dense irregular connective tissue.

    • Contains blood vessels, nerve endings, and glands.

Subcutaneous Layer (Hypodermis)

  • Not part of the skin but connects skin to underlying structures.

  • Made of adipose tissue (fat storage, insulation, cushioning).

Accessory Structures of the Skin

Cutaneous (Exocrine) Glands

  1. Sebaceous Glands

    • Secrete sebum (oily substance with fats, proteins, salts).

    • Lubricates and waterproofs skin and hair.

  2. Sweat (Sudoriferous) Glands

    • Eccrine glands: Found all over the body; produce watery sweat for thermoregulation.

    • Apocrine glands: Located in armpits, groin; produce thicker sweat that interacts with bacteria (causing odor).

Clinical Notes

  • Psoriasis: Overproduction of skin cells → scaly patches.

  • Blisters: Fluid-filled separation of epidermis and dermis.

  • Calluses: Thickening of skin due to friction.

  • Skin Cancer: Uncontrolled cell growth due to UV damage.

Review Questions & Answers

  1. Major histological difference between thick and thin skin? Locations?

    • Thick skin has a stratum lucidum and a thicker stratum corneum; found on palms and soles.

    • Thin skin lacks stratum lucidum and has hair follicles; found on most of the body.

  2. How does the skin adjust body temperature? Negative or positive feedback?

    • Sweating (cooling) and vasodilation (heat loss).

    • Vasoconstriction and shivering (heat retention).

    • This is negative feedback because it reverses temperature changes.

  3. Five layers of epidermis (deep to superficial) & features?

    • Stratum basale: Stem cells, melanocytes, Merkel cells.

    • Stratum spinosum: Dendritic cells for immune defense.

    • Stratum granulosum: Keratin production; cells start dying.

    • (Stratum lucidum): Only in thick skin.

    • Stratum corneum: Dead, keratinized cells.

  4. Two layers of the dermis & connective tissue types?

    • Papillary layer → Areolar connective tissue.

    • Reticular layer → Dense irregular connective tissue.

  5. What gland is associated with hair follicles? How does its secretion differ from sweat glands?

    • Sebaceous glands (oil glands) secrete sebum, an oily substance.

    • Sweat glands (eccrine & apocrine) produce watery sweat for cooling.

  6. Why should the epidermis be effective but not too effective at blocking UV?

    • Too much UV exposure causes DNA damage → skin cancer.

    • Too little UV exposure prevents Vitamin D synthesis, leading to bone disorders like rickets.

Chapter 3: Skeletal System Physiology Review

Functions of the Skeletal System

  1. Support – Provides structural framework.

  2. Protection – Shields organs (e.g., skull protects brain, ribs protect heart/lungs).

  3. Movement – Acts as levers for muscles.

  4. Storage – Stores calcium, phosphate, and fat in the bone matrix.

  5. Blood Cell Production – Red bone marrow produces red and white blood cells.

Bone Histology

  • Bone matrix:

    • Calcium salts provide hardness.

    • Collagen fibers provide flexibility.

    • Rickets occurs when bones lack calcium (due to low Vitamin D).

Bone Anatomy

  • Epiphyses – Ends of long bones.

  • Epiphyseal line – Remnant of growth plate.

  • Diaphysis – Shaft of the bone.

  • Medullary cavity – Contains bone marrow.

  • Articular cartilage – Reduces friction at joints.

Microscopic Bone Anatomy

Compact Bone (External Layer & Diaphysis)

  • Osteons: Cylindrical structures of compact bone.

    • Lamellae: Concentric rings of bone matrix.

Spongy Bone (Epiphyses & Interior)

  • Trabeculae: Lattice-like structure for strength without weight.

Bone Cells & Their Functions

  1. Osteoblasts – Build bone, secrete osteoid (bone matrix).

  2. Osteocytes – Maintain bone, trapped in lacunae.

  3. Osteoclasts – Break down bone, release calcium into blood.

Bone Physiology

Ossification (Bone Formation)

  • Process of replacing cartilage with bone.

  • Fibrodysplasia ossificans progressiva – A disorder where soft tissues turn to bone.

  • Starts at 6 weeks of fetal development, continues until age 25.

Calcification

  • Deposition of calcium salts in bone & other tissues.

  • Abnormal calcification can occur (e.g., heart valve calcification).

Endochondral Ossification (Bone Formation from Cartilage)

  • Starts as hyaline cartilage.

  • Cartilage is gradually replaced by bone as blood vessels invade and osteoblasts deposit bone matrix.

  • Some cartilage remains in growth plates until adulthood.

Bone Remodeling

  • Ongoing replacement of old bone with new bone.

  • Maintains bone strength and calcium balance.

Calcium Homeostasis & Hormonal Regulation

  • Bone stores 99% of the body’s calcium.

  • Calcium levels in blood are tightly regulated.

If Blood Calcium is TOO LOW:

  • Parathyroid hormone (PTH) & Calcitriol (Vitamin D) increase calcium.

    • Bone response → Osteoclasts break down bone to release calcium.

    • Intestinal response → More calcium absorbed from food.

    • Kidney response → Less calcium excreted in urine.

If Blood Calcium is TOO HIGH:

  • Calcitonin lowers calcium.

    • Bone response → Osteoblasts store calcium in bone.

    • Intestinal response → Less calcium absorbed.

    • Kidney response → More calcium excreted.

Osteoporosis

  • Loss of bone density, making bones fragile.

  • Causes:

    • Aging (especially in postmenopausal women due to estrogen loss).

    • Lack of exercise.

    • Low calcium/Vitamin D intake.

  • Prevention:

    • Weight-bearing exercise.

    • Calcium & Vitamin D supplements.

Review Questions & Answers

  1. Difference between spongy & compact bone?

    • Compact bone: Dense, contains osteons, found in diaphysis.

    • Spongy bone: Lightweight, has trabeculae, found in epiphyses.

  2. Why regulate blood calcium within a narrow range?

    • Calcium is essential for muscle contractions, nerve function, and blood clotting.

    • Too little = muscle spasms & weak bones.

    • Too much = abnormal calcification & kidney stones.

  3. Effects of Calcitonin, PTH, and Calcitriol on blood calcium?

    • Calcitonin ↓ blood calcium (stores it in bone).

    • PTH & Calcitriol ↑ blood calcium (osteoclasts release calcium from bone).

  4. Why does rickets occur with low Vitamin D?

    • Vitamin D is needed to absorb calcium.

    • Without it, bones become weak & deformed (rickets).

  5. What causes osteoporosis? How to prevent it?

    • Causes: Aging, hormonal changes, low calcium intake.

    • Prevention: Exercise, calcium & vitamin D supplements.

  6. Functions of the skeletal system?

    • Support, protection, movement, storage, blood cell production.

  7. Importance of calcium & collagen in bone?

    • Calcium = Hardness.

    • Collagen = Flexibility.

  8. Difference between calcification & ossification?

    • Calcification = Calcium deposits (can happen in soft tissues).

    • Ossification = Formation of actual bone.

  9. Steps of Endochondral Ossification (Cartilage → Bone)?

    • Starts as hyaline cartilage model.

    • Blood vessels invade; osteoblasts replace cartilage with bone matrix.

    • Growth continues at epiphyseal plates until adulthood.

  10. Bone cells & functions?

  • Osteoblasts = Build bone.

  • Osteocytes = Maintain bone.

  • Osteoclasts = Break down bone.