Anatomy and Physiology I: Study Guide for Tissues, Integumentary System, and Skeletal System

Chapter 4: Tissue – The Living Fabric

Overview of the Four Basic Tissue Types

The human body is composed of four primary tissue types, each with distinct structures and functions. Understanding these tissues is fundamental to the study of anatomy and physiology.

• 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, blood, and fat.

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

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

Characteristics of Epithelial Tissue

• Cellularity: Composed almost entirely of closely packed cells.

• Polarity: Has an apical (top) surface and a basal (bottom) surface.

• Attachment: Supported by a basement membrane.

• Avascularity: Lacks blood vessels; receives nutrients by diffusion.

• Regeneration: High capacity for renewal and repair.

Classification and Types of Epithelia

Epithelia are classified by the number of cell layers and the shape of the cells.

• Simple Epithelium: Single layer of cells (e.g., simple squamous, simple cuboidal, simple columnar).

• Stratified Epithelium: Multiple layers (e.g., stratified squamous, stratified cuboidal, stratified columnar).

• Pseudostratified Epithelium: Appears layered but is a single layer with varying cell heights.

• Transitional Epithelium: Specialized for stretching (e.g., urinary bladder).

Chief Functions and Locations:

• Simple Squamous: Diffusion and filtration (e.g., alveoli of lungs, lining of blood vessels).

• Simple Cuboidal: Secretion and absorption (e.g., kidney tubules).

• Simple Columnar: Absorption and secretion (e.g., digestive tract lining).

• Stratified Squamous: Protection (e.g., skin, mouth lining).

Glands: Exocrine vs. Endocrine

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

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

• Endocrine Glands: Ductless; secrete hormones directly into the bloodstream.

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

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

Connective Tissue: Characteristics and Elements

• Common Characteristics: All arise from mesenchyme, have varying degrees of vascularity, and contain an extracellular matrix.

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

• Ground Substance: Unstructured material filling the space between cells; contains interstitial fluid, cell adhesion proteins, and proteoglycans.

• Fibers: Collagen (strength), elastic (stretch), reticular (support).

• Cell Types: Fibroblasts (produce fibers), chondroblasts (cartilage), osteoblasts (bone), adipocytes (fat), and white blood cells (defense).

Types of Connective Tissue and Functions

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

• Cartilage: Hyaline, elastic, fibrocartilage.

• Bone: Compact and spongy.

• Blood: Fluid connective tissue.

Functions: Support, protection, insulation, storage, and transport.

Chapter 5: The Integumentary System

Structure of the Skin

• Two Main Layers: Epidermis (superficial, epithelial tissue) and dermis (deeper, connective tissue).

• Subcutaneous Tissue (Hypodermis): Not part of the skin; consists mainly of adipose tissue, anchors skin to underlying structures.

Cells of the Epidermis

• Keratinocytes: Produce keratin, a protective protein.

• Melanocytes: Produce melanin pigment, protect against UV radiation.

• Langerhans (Dendritic) Cells: Immune defense.

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

Layers of the Epidermis

• Stratum Basale: Deepest, mitotically active layer.

• Stratum Spinosum: Several layers of keratinocytes, some mitosis.

• Stratum Granulosum: Keratinization begins, cells flatten.

• Stratum Lucidum: Only in thick skin (palms, soles).

• Stratum Corneum: Outermost, dead keratinized cells.

Dermis: Layers and Functions

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

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

Skin Color

• Factors: Melanin, carotene, hemoglobin.

• Diseases/Ailments: Cyanosis (blue), erythema (red), jaundice (yellow), pallor (pale), bruises (hematomas).

Glands of the Skin

• Sudoriferous (Sweat) Glands: Eccrine (thermoregulation, all over body), apocrine (axillary/genital, odor).

• Sebaceous (Oil) Glands: Secrete sebum, lubricate skin/hair, antibacterial.

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

Functions of the Skin

• Protection, body temperature regulation, cutaneous sensation, metabolic functions, blood reservoir, excretion.

Skin Cancers and Burns

• Skin Cancers: Basal cell carcinoma, squamous cell carcinoma, melanoma.

• Burns: Classified by depth (first, second, third degree); treatment includes fluid replacement, infection control, skin grafting.

Chapter 6: Bones and Skeletal Tissue

Cartilage Types: Structure, Function, and Location

• Hyaline Cartilage: Most abundant; provides support, flexibility, and resilience. Found in nose, trachea, larynx, costal cartilages, articular surfaces.

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

• Fibrocartilage: Thick collagen fibers; strong, resists compression. Found in intervertebral discs, pubic symphysis, menisci.

Cartilage Growth

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

• Interstitial Growth: Chondrocytes divide and secrete new matrix from within.

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, humerus).

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

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

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

Gross Anatomy of Bones

• Long Bone: Diaphysis (shaft), epiphyses (ends), medullary cavity (contains yellow marrow), periosteum (outer membrane), endosteum (lines internal surfaces).

• Flat Bone: Thin plates of spongy bone (diploë) covered by compact bone; periosteum and endosteum present.

Bone Marrow, Periosteum, and Endosteum

• Red Marrow: Hematopoietic tissue; found in trabecular cavities of spongy bone (e.g., hip bones, sternum).

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

• Periosteum: Double-layered membrane covering external bone surface; contains osteogenic cells.

• Endosteum: Delicate membrane lining internal bone surfaces.

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 a central canal.

• Spongy Bone: Trabeculae align along lines of stress; no osteons.

Chemical Composition of Bone

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

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

Bone Growth and Epiphyseal Plate

• Long bones grow in length at the epiphyseal plate through endochondral ossification.

Bone Remodeling and Negative Feedback

• Bone is continuously remodeled by osteoblasts and osteoclasts.

• Calcium homeostasis is regulated by a negative feedback loop involving parathyroid hormone (PTH):

$\text{If blood Ca}^{2+} \text{ decreases:} \\ \text{PTH is released} \rightarrow \text{osteoclasts resorb bone} \rightarrow \text{Ca}^{2+} \text{ released into blood}$

Fracture Repair and Bone Diseases

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

• Diseases: Osteoporosis (bone resorption outpaces formation), osteomalacia/rickets (soft bones due to vitamin D deficiency).

Tissue Type	Main Function	Location Example
Epithelial	Protection, absorption, secretion	Skin, lining of GI tract
Connective	Support, binding, transport	Bone, blood, fat
Muscle	Movement	Skeletal muscles, heart
Nervous	Control, communication	Brain, nerves

Additional info: Some explanations and examples have been expanded for clarity and completeness based on standard anatomy and physiology textbooks.