BI 231 Human Anatomy & Physiology: Tissues, Skin, and Skeletal System Study Guide

Tissues

Primary Tissue Classes and Subclasses

The human body is composed of four primary tissue classes, each with distinct structures and functions.

• Epithelial Tissue: Covers body surfaces, lines cavities, and forms glands. Subclasses include simple (single layer) and stratified (multiple layers) epithelia, with further classification by cell shape (squamous, cuboidal, columnar).

• Connective Tissue: Supports, binds, and protects organs. Subclasses include connective tissue proper (loose and dense), cartilage, bone, and blood.

• Muscle Tissue: Responsible for movement. Subclasses: skeletal (voluntary), cardiac (heart), and smooth (walls of hollow organs).

• Nervous Tissue: Initiates and transmits electrical impulses. Composed of neurons and supporting glial cells.

Example: The skin contains epithelial tissue (epidermis), connective tissue (dermis), muscle tissue (arrector pili), and nervous tissue (sensory receptors).

Tissue Healing Processes

Tissue repair involves several overlapping phases:

• Inflammation: Damaged cells release chemicals, increasing blood flow and attracting immune cells.

• Organization: Granulation tissue forms, restoring blood supply.

• Regeneration/Fibrosis: Regeneration replaces damaged cells with the same type; fibrosis forms scar tissue.

Regenerative Abilities of Tissue Classes

• Epithelial and Connective Tissues: High regenerative capacity.

• Muscle Tissue: Moderate (smooth muscle) to poor (skeletal, cardiac) regeneration.

• Nervous Tissue: Very limited regeneration in the central nervous system.

Factors Affecting Tissue Repair

• Nutrition (especially protein and vitamin C)

• Blood supply

• Age

• Extent of injury

• Health status (e.g., diabetes, infection)

Skin (Integumentary System)

Functions of Skin

• Protection (physical, chemical, biological barriers)

• Thermoregulation

• Sensation

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

• Blood reservoir

• Excretion

Layers of Skin and Tissue Types

• Epidermis: Stratified squamous epithelium

• Dermis: Dense irregular connective tissue (contains papillary and reticular layers)

• Hypodermis (subcutaneous): Adipose and areolar connective tissue (not technically part of skin)

Skin and Thermoregulation

• Sweat glands secrete sweat for evaporative cooling.

• Blood vessels dilate (vasodilation) or constrict (vasoconstriction) to regulate heat loss.

Skin Changes with Aging

• Thinning of epidermis and dermis

• Decreased collagen and elastin (wrinkling)

• Reduced sweat and oil gland activity

• Slower healing

Types of Burns and Complications

• First-degree: Epidermis only; redness, pain.

• Second-degree: Epidermis and part of dermis; blisters, pain.

• Third-degree: Full thickness; may appear white or charred, no pain (nerve endings destroyed).

• Complications: Fluid loss, infection, temperature regulation issues.

Rule of Nines

The "Rule of Nines" estimates the percentage of body surface area affected by burns:

Body Region	Percentage
Head and Neck	9%
Each Upper Limb	9% (x2 = 18%)
Each Lower Limb	18% (x2 = 36%)
Anterior Trunk	18%
Posterior Trunk	18%
Perineum	1%

Blister Formation

• Blisters form when the epidermis separates from the dermis, often due to friction or burns, and fluid accumulates in the space.

Skin Diseases and Epidermal Derivatives

• Common diseases: eczema, psoriasis, skin cancer (basal cell carcinoma, squamous cell carcinoma, melanoma).

• Epidermal derivatives: hair, nails, sweat glands, sebaceous glands.

Skin Color and Health

• Pallor, cyanosis, jaundice, and erythema can indicate underlying health conditions.

Skeletal System

Functions of the Skeletal System

• Support

• Protection

• Movement (leverage for muscles)

• Mineral storage (calcium, phosphate)

• Blood cell production (hematopoiesis)

• Triglyceride storage

Classification of Bones by Shape

• Long bones: e.g., femur, humerus

• Short bones: e.g., carpals, tarsals

• Flat bones: e.g., skull, ribs

• Irregular bones: e.g., vertebrae

• Sesamoid bones: e.g., patella

General Features of a Long Bone

• Diaphysis: Shaft

• Epiphyses: Ends

• Metaphysis: Between diaphysis and epiphysis

• Medullary cavity: Contains marrow

• Periosteum: Outer covering

• Endosteum: Lines medullary cavity

Principal Cell Types in Osseous Tissue

• Osteogenic cells: Stem cells

• Osteoblasts: Bone-forming cells

• Osteocytes: Mature bone cells

• Osteoclasts: Bone-resorbing cells

Spongy vs. Compact Bone

• Compact bone: Dense, forms outer layer

• Spongy bone: Lattice-like, contains trabeculae, found at ends of long bones and inside flat bones

Hematopoiesis

• Production of blood cells, occurs in red bone marrow (mainly in flat bones and epiphyses of long bones in adults)

Bone Formation (Ossification)

• Intramembranous ossification: Forms flat bones (e.g., skull)

• Endochondral ossification: Forms most bones from cartilage templates

Bone Maintenance

• Bone remodeling: balance of bone deposition (osteoblasts) and resorption (osteoclasts)

• Influenced by mechanical stress, hormones, and nutrition

Nutrition and Bone Maintenance

• Calcium, phosphate, vitamin D, and protein are essential for bone health

Hormones and Bone Maintenance

• Parathyroid hormone (PTH): increases blood calcium by stimulating osteoclasts

• Calcitonin: lowers blood calcium by inhibiting osteoclasts

• Growth hormone, sex hormones: stimulate bone growth

Bone Disorders

• Osteoporosis, osteomalacia, rickets, Paget's disease

Fracture Types and Repair

• Types: Simple (closed), compound (open), comminuted, greenstick, spiral, etc.

• Repair Steps: Hematoma formation, fibrocartilaginous callus, bony callus, bone remodeling

Skeletal Abnormalities

• Microcephaly, hydrocephaly, cleft palate, spina bifida, lordosis, kyphosis, scoliosis, herniated disc

Axial vs. Appendicular Skeleton

• Axial: Skull, vertebral column, rib cage

• Appendicular: Limbs and girdles

Vertebrae and Vertebral Regions

• Regions: cervical (7), thoracic (12), lumbar (5), sacral (5 fused), coccygeal (4 fused)

• Parts: body, vertebral arch, processes (spinous, transverse), vertebral foramen

Joints: Types, Structures, and Functions

• Fibrous: Sutures (skull), syndesmoses (radius/ulna), gomphoses (teeth)

• Cartilaginous: Synchondroses (epiphyseal plate), symphyses (pubic symphysis)

• Synovial: Most movable; features include joint cavity, articular cartilage, synovial fluid

Knee Joint Features

• Largest synovial joint; contains menisci, cruciate ligaments, collateral ligaments, bursae

Joint Movements and Limitations

• Movements: flexion, extension, abduction, adduction, rotation, circumduction, etc.

• Limitations: joint structure, ligaments, muscle tone, soft tissue apposition

Joint Disorders

• Arthritis (osteoarthritis, rheumatoid arthritis, gout), dislocations, sprains

Associated Structures

• Tendons: Connect muscle to bone

• Ligaments: Connect bone to bone

• Bursae: Fluid-filled sacs reducing friction

• Tendon sheaths: Tubular bursae surrounding tendons