Chapter 4 – Tissue: The Living Fabric

Basic Tissue Types: Structure, Function, and Location

• Epithelial Tissue: Covers body surfaces, lines cavities, and forms glands. Functions include protection, absorption, filtration, excretion, secretion, and sensory reception. Found on skin surface (epidermis), lining of digestive tract, and glands.

• Connective Tissue: Supports, protects, and binds other tissues. Functions include support, storage, transport, and immunity. Found in bones, tendons, fat, and blood.

• Muscle Tissue: Responsible for movement. Types include skeletal (attached to bones), cardiac (heart), and smooth (walls of hollow organs).

• Nervous Tissue: Initiates and transmits electrical impulses. Found in brain, spinal cord, and nerves.

Structural and Functional Characteristics of Epithelial Tissue

• Cellularity: Composed almost entirely of closely packed cells with minimal extracellular material.

• Polarity: Has an apical (free) surface and a basal (attached) surface.

• Attachment: Supported by a basement membrane.

• Avascularity: Contains no blood vessels; nourished by diffusion.

• Regeneration: High capacity for renewal via mitosis.

Types of Body Membranes

• Mucous Membranes (Mucosae): Line body cavities open to the exterior (e.g., digestive, respiratory tracts).

• Serous Membranes (Serosae): Line closed ventral body cavities; secrete serous fluid (e.g., peritoneum, pleura, pericardium).

• Cutaneous Membrane: The skin; covers the body surface.

Classification of Epithelia

• By Layers: Simple (one layer) or stratified (multiple layers).

• By Shape: Squamous (flat), cuboidal (cube-shaped), columnar (tall).

• Chief Functions and Locations:

  • Simple squamous: Diffusion/filtration; alveoli, capillaries.

  • Simple cuboidal: Secretion/absorption; kidney tubules, glands.

  • Simple columnar: Absorption/secretion; digestive tract lining.

  • Stratified squamous: Protection; skin, mouth, esophagus.

  • Pseudostratified columnar: Secretion; trachea (with cilia).

  • Transitional: Stretching; urinary bladder.

Glands: Exocrine vs. Endocrine

• Gland: One or more cells that secrete a product.

• Exocrine Glands: Secrete onto body surfaces or into body cavities via ducts (e.g., sweat, salivary glands).

• Endocrine Glands: Ductless; secrete hormones into blood (e.g., pituitary, thyroid).

• Unicellular: Single cells (e.g., goblet cells).

• Multicellular: Composed of many cells (e.g., most glands).

Connective Tissue: Characteristics and Structural Elements

• Common Characteristics: Mesenchyme origin, varying vascularity, abundant extracellular matrix.

• Structural Elements: Ground substance, fibers, and cells.

Connective Tissue Proper vs. Other Connective Tissues

• Connective Tissue Proper: Includes loose (areolar, adipose, reticular) and dense (regular, irregular, elastic) types.

• Other Types: Cartilage, bone, blood.

Loose vs. Dense Connective Tissue

• Loose: More ground substance, fewer fibers (e.g., areolar, adipose, reticular); found under epithelia, around organs.

• Dense: More fibers, less ground substance (e.g., tendons, ligaments, dermis).

Connective Tissue Fibers

• Collagen: Strong, provides tensile strength.

• Elastic: Stretch and recoil.

• Reticular: Supportive networks.

Connective Tissue Cell Types

• Fibroblasts: Produce fibers and ground substance.

• Chondroblasts: Cartilage-forming cells.

• Osteoblasts: Bone-forming cells.

• Adipocytes: Store fat.

• White blood cells, mast cells, macrophages: Defense and immune functions.

Ground Substance

• Definition: Unstructured material filling space between cells; contains interstitial fluid, cell adhesion proteins, proteoglycans.

Chapter 5 – The Integumentary System

Layers of the Skin and Subcutaneous Tissue

• Epidermis: Superficial, keratinized stratified squamous epithelium.

• Dermis: Deep, connective tissue layer.

• Subcutaneous Tissue (Hypodermis): Not part of skin; adipose tissue for insulation and anchoring.

Major Cell Types of the Epidermis

• Keratinocytes: Produce keratin for protection.

• Melanocytes: Synthesize melanin pigment.

• Epidermal Dendritic (Langerhans) Cells: Immune defense.

• Tactile (Merkel) Cells: Sensory receptors for touch.

Layers of the Epidermis (from deep to superficial)

• Stratum basale: Mitotically active stem cells.

• Stratum spinosum: Several layers of keratinocytes; some immune cells.

• Stratum granulosum: Keratinization begins; cells flatten.

• Stratum lucidum: Only in thick skin (palms, soles); clear layer.

• Stratum corneum: Dead, keratinized cells; barrier function.

Dermis: Layers, Tissues, and Functions

• Papillary Layer: Areolar connective tissue; forms dermal papillae (fingerprints).

• Reticular Layer: Dense irregular connective tissue; provides strength and elasticity.

Factors Affecting Skin Color

• Melanin: Brown-black pigment; genetic and environmental influences.

• Carotene: Yellow-orange pigment from diet.

• Hemoglobin: Red pigment in blood; visible in fair skin.

Diseases and Ailments Affecting Skin Color

• Cyanosis: Blue tint due to low oxygen.

• Pallor: Pale color from anemia or shock.

• Jaundice: Yellowing from bilirubin buildup (liver disorder).

• Erythema: Redness from inflammation or fever.

Glands of the Skin

• Sudoriferous (Sweat) Glands: Eccrine (thermoregulation; most numerous) and apocrine (axillary/anogenital; odor).

• Sebaceous (Oil) Glands: Secrete sebum; lubricate skin/hair; associated with hair follicles.

• Modifications: Ceruminous (earwax), mammary (milk).

Functions of the Skin

• Protection (chemical, physical, biological barriers)

• Body temperature regulation

• Cutaneous sensation

• Metabolic functions (e.g., vitamin D synthesis)

• Blood reservoir

• Excretion

Skin Cancers and Burns

• Basal Cell Carcinoma: Most common, least malignant.

• Squamous Cell Carcinoma: Can metastasize.

• Melanoma: Most dangerous; cancer of melanocytes.

• Burns: First-degree (epidermis), second-degree (epidermis + dermis), third-degree (full thickness).

• Treatment: Fluid replacement, infection control, skin grafting for severe burns.

Chapter 6 – Bones and Skeletal Tissue

Cartilage Types: Structure, Function, and Location

• Hyaline Cartilage: Most abundant; support with flexibility; found in nose, trachea, articular surfaces, costal cartilages.

• Elastic Cartilage: More elastic fibers; maintains shape; found in ear, epiglottis.

• Fibrocartilage: Thick collagen fibers; tensile strength; found in intervertebral discs, pubic symphysis, menisci.

Cartilage Growth

• Appositional Growth: Cells in perichondrium secrete new matrix on surface.

• Interstitial Growth: Chondrocytes divide and secrete matrix within cartilage.

Functions of Bone

1. Support

2. Protection

3. Movement (leverage)

4. Mineral storage (calcium, phosphate)

5. Blood cell formation (hematopoiesis)

6. Triglyceride (fat) storage

7. Hormone production (osteocalcin)

Types of Bones

• Long Bones: Longer than wide (e.g., femur, humerus).

• Short Bones: Cube-shaped (e.g., carpals, tarsals).

• Flat Bones: Thin, flat (e.g., sternum, skull bones).

• Irregular Bones: Complex shapes (e.g., vertebrae, hip bones).

Gross Anatomy of Bones

• Long Bone: Diaphysis (shaft), epiphyses (ends), membranes (periosteum, endosteum), medullary cavity (yellow marrow).

• Flat Bone: Thin plates of spongy bone (diploë) covered by compact bone.

Bone Marrow, Periosteum, and Endosteum

• Red Marrow: Hematopoietic; found in spongy bone of flat bones, epiphyses of long bones.

• Yellow Marrow: Fat storage; found in medullary cavities of adults.

• Periosteum: Double-layered membrane covering bone except at joints; contains osteogenic cells.

• Endosteum: Thin membrane lining internal bone surfaces; contains osteogenic cells.

Microscopic Structure of Bone

• Cell Types: Osteogenic cells (stem cells), osteoblasts (bone-forming), osteocytes (mature bone cells), osteoclasts (bone-resorbing).

• Osteon (Haversian System): Structural unit of compact bone; concentric lamellae around central canal.

• Spongy Bone: Trabeculae align along lines of stress; spaces filled with marrow.

Chemical Composition of Bone

• Organic: Cells, osteoid (collagen fibers, ground substance).

• Inorganic: Hydroxyapatites (mineral salts, mainly calcium phosphate).

Bone Growth and Epiphyseal Plate

• Longitudinal Growth: Occurs at epiphyseal plate via endochondral ossification.

• Appositional Growth: Increase in bone thickness.

Bone Remodeling and Negative Feedback

• Bone is continuously deposited and resorbed.

• Negative Feedback Loop: Maintains blood calcium levels via parathyroid hormone (PTH) and calcitonin.

  • When blood calcium decreases, PTH is released, stimulating osteoclasts to resorb bone and release calcium.

  • When blood calcium increases, calcitonin may promote bone deposition.

Fracture Repair and Bone Diseases

• Fracture Repair: Hematoma formation, fibrocartilaginous callus, bony callus, bone remodeling.

• Diseases: Osteoporosis (bone resorption > deposition), osteomalacia/rickets (poor mineralization), Paget's disease (excessive bone formation and breakdown).

Additional info: For diagrams (e.g., skin, long bone, osteon), refer to textbook figures as indicated (e.g., Fig 5.1, 6.5, 6.8) for labeling practice.