Chapter 4 - Tissue: The Living Fabric

Basic Tissue Types

The human body is composed of four basic tissue types, each with distinct structure and function:

• Epithelial Tissue: Covers body surfaces, lines cavities, and forms glands. Functions include protection, absorption, filtration, excretion, secretion, and sensory reception.

• Connective Tissue: Supports, protects, and binds other tissues. Found throughout the body, including bone, cartilage, blood, and adipose tissue.

• Muscle Tissue: Responsible for movement. Types include skeletal, cardiac, and smooth muscle.

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

Example: Epithelial tissue lines the stomach, connective tissue forms tendons, muscle tissue contracts to move limbs, and nervous tissue transmits signals for sensation.

Structural and Functional Characteristics of Epithelial Tissue

• Cellularity: Composed almost entirely of tightly packed cells.

• Polarity: Has an apical surface (exposed) and a basal surface (attached to underlying tissue).

• Attachment: Supported by a basement membrane.

• Avascularity: Lacks blood vessels; nutrients diffuse from underlying tissues.

• Regeneration: High capacity for renewal.

Example: Skin epithelium regenerates rapidly after injury.

Types of Membranes

Three main types of membranes are found in the body:

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

• Mucous Membrane: Lines body cavities open to the exterior (e.g., digestive, respiratory tracts).

• Serous Membrane: Lines closed internal cavities (e.g., pericardium, pleura, peritoneum).

Types of Epithelia: Classification, Function, and Location

• Simple Squamous: Single layer of flat cells; allows diffusion and filtration. Found in alveoli and blood vessels.

• Simple Cuboidal: Single layer of cube-shaped cells; secretion and absorption. Found in kidney tubules.

• Simple Columnar: Single layer of tall cells; absorption and secretion. Found in digestive tract lining.

• Pseudostratified Columnar: Appears layered but is not; secretion and movement of mucus. Found in respiratory tract.

• Stratified Squamous: Multiple layers; protects against abrasion. Found in skin, mouth, esophagus.

• Transitional: Changes shape; allows stretching. Found in urinary bladder.

Special Characteristics of Epithelial Tissues

• Cellularity

• Polarity

• Attachment to basement membrane

• Avascularity

• Regeneration

Glands: Exocrine vs. Endocrine

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

• Exocrine Glands: Secrete products into ducts (e.g., sweat, salivary glands).

• Endocrine Glands: Secrete hormones directly into the bloodstream (e.g., thyroid, pituitary).

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

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

Connective Tissue: Characteristics and Structural Elements

• Common Characteristics: All arise from mesenchyme, have varying degrees of vascularity, and contain an 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) connective tissues.

• Other Connective Tissues: Cartilage, bone, and blood.

Loose vs. Dense Connective Tissues

• Loose Connective Tissue: More ground substance, fewer fibers. Examples: areolar (under epithelia), adipose (fat storage), reticular (lymphoid organs).

• Dense Connective Tissue: More fibers, less ground substance. Examples: dense regular (tendons), dense irregular (dermis), elastic (arteries).

Types of Connective Tissue and Functions

• Areolar: Supports and binds other tissues.

• Adipose: Stores energy, insulates, cushions.

• Reticular: Forms internal skeleton of lymphoid organs.

• Dense Regular: Attaches muscles to bones.

• Dense Irregular: Withstands tension from multiple directions.

• Elastic: Allows stretch and recoil.

• Cartilage: Supports, cushions, resists compression.

• Bone: Supports, protects, stores minerals.

• Blood: Transports nutrients, wastes, gases.

Ground Substance

Ground substance is the unstructured material filling the space between cells and fibers in connective tissue. It contains water, proteins, and polysaccharides.

Connective Tissue Fibers

• Collagen: Strong, provides tensile strength.

• Elastic: Stretch and recoil.

• Reticular: Forms networks for support.

Connective Tissue Cell Types

• Fibroblasts: Produce fibers and ground substance.

• Chondroblasts: Produce cartilage.

• Osteoblasts: Produce bone.

• Adipocytes: Store fat.

• White blood cells: Immune response.

• Mast cells: Inflammation.

• Macrophages: Phagocytosis.

Chapter 5 - The Integumentary System

Layers of Skin and Subcutaneous Tissue

• Epidermis: Superficial layer; composed of epithelial cells.

• Dermis: Deep layer; composed of connective tissue.

• Subcutaneous Tissue (Hypodermis): Not part of skin; consists of adipose and areolar tissue.

Major Cell Types of the Epidermis

• Keratinocytes: Produce keratin for protection.

• Melanocytes: Produce melanin for skin color.

• Langerhans Cells: Immune defense.

• Merkel Cells: Sensory receptors.

Layers of the Epidermis

• Stratum Basale: Deepest layer; cell division.

• Stratum Spinosum: Provides strength and flexibility.

• Stratum Granulosum: Keratinization begins.

• Stratum Lucidum: Only in thick skin; clear layer.

• Stratum Corneum: Outermost; dead, keratinized cells.

Layers of the Dermis

• Papillary Layer: Areolar connective tissue; forms fingerprints.

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

Factors Affecting Skin Color

• Melanin: Brown-black pigment.

• Carotene: Yellow-orange pigment.

• Hemoglobin: Red pigment from blood.

Diseases and Ailments Affecting Skin Color

• Albinism: Lack of melanin.

• Jaundice: Yellowing due to bilirubin.

• Cyanosis: Blue tint from low oxygen.

• Erythema: Redness from increased blood flow.

Glands of the Skin

• Sudoriferous (Sweat) Glands: Eccrine (all over body; thermoregulation) and apocrine (armpits, groin; odor).

• Sebaceous (Oil) Glands: Secrete sebum; lubricates skin and hair.

Eccrine vs. Apocrine Glands

• Eccrine: Most numerous; watery sweat; regulates temperature.

• Apocrine: Larger; found in axillary and genital areas; sweat contains proteins and lipids.

• Modified Glands: Ceruminous (ear wax), mammary (milk).

Functions of the Skin

• Protection

• Regulation of body temperature

• Sensation

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

• Blood reservoir

• Excretion

Skin Cancers and Burn Types

• Basal Cell Carcinoma: Most common, least dangerous.

• Squamous Cell Carcinoma: Can metastasize.

• Melanoma: Most dangerous; arises from melanocytes.

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

Treatment: Depends on severity; may include fluid replacement, skin grafts, and removal of damaged tissue.

Chapter 6 – Bones and Skeletal Tissue

Cartilage Types: Structure, Function, and Location

• Hyaline Cartilage: Most abundant; provides support and flexibility. Found in nose, trachea, ends of long bones.

• Elastic Cartilage: Contains elastic fibers; maintains shape. Found in ear and epiglottis.

• Fibrocartilage: Strongest; resists compression. Found in intervertebral discs, pubic symphysis.

Cartilage Growth

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

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

Functions of Bone

• Support

• Protection

• Movement

• Mineral storage

• Blood cell formation (hematopoiesis)

• Triglyceride storage

• Hormone production

Types of Bone

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

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

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

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

Gross Anatomy of Flat and Long Bones

• Flat Bone: Thin, with two parallel compact bone surfaces and spongy bone in between.

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

Red and Yellow Marrow, Periosteum, and Endosteum

• Red Marrow: Hematopoietic tissue; found in spongy bone.

• Yellow Marrow: Fat storage; found in medullary cavity.

• Periosteum: Outer membrane; contains osteoblasts and osteoclasts.

• Endosteum: Lines internal bone surfaces.

Microscopic Structure of Bone

• Cell Types: Osteoblasts (build bone), osteocytes (maintain bone), osteoclasts (break down bone).

• Osteons: Structural unit of compact bone; concentric lamellae around central canal.

• Spongy Bone: Trabeculae; spaces filled with marrow.

Chemical Composition of Bone

• Organic: Cells, osteoid (collagen fibers).

• Inorganic: Hydroxyapatite (calcium phosphate crystals).

Bone Growth and Epiphyseal Plate

• Epiphyseal Plate: Cartilage growth plate; allows lengthening of bone.

• Bone Growth: Occurs via endochondral and intramembranous ossification.

Bone Remodeling: Negative Feedback Loop

Bone remodeling is regulated by hormones, especially parathyroid hormone (PTH), which increases blood calcium by stimulating osteoclasts.

• Negative Feedback: When blood calcium drops, PTH is released, increasing bone resorption.

Equation:

Fracture Repair and Bone Diseases

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

• Bone Diseases: Osteoporosis (loss of bone mass), osteomalacia (softening), Paget's disease (abnormal remodeling).

Example: Osteoporosis increases fracture risk in elderly.

Additional info: Academic context and definitions were added to expand brief study guide points into full explanations. Table formatting was not required as no tables were present in the original material.