Midterm 2 Study Guide: Tissues, Skin, and Skeletal System

Tissues

Primary Tissue Classes and Their Subclasses

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

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

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

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

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

Tissue Healing Processes

Tissue repair involves several overlapping stages:

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

• Organization: Granulation tissue forms, restoring blood supply.

• Regeneration/Fibrosis: Epithelial cells regenerate, or fibrous tissue replaces lost tissue (scar formation).

Regenerative Abilities of Tissue Classes

• Epithelial and connective tissues (except cartilage) have high regenerative capacity.

• Muscle tissue regenerates poorly (skeletal) or moderately (smooth).

• Nervous tissue in the brain and spinal cord has very limited regeneration.

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: Connective tissue (areolar and dense irregular)

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

Skin and Thermoregulation

• Regulates body temperature via sweat production and blood vessel dilation/constriction.

• Evaporation of sweat cools the body; constriction conserves heat.

Aging and the Skin

• Thinning of epidermis and dermis

• Decreased collagen and elastin fibers (wrinkling)

• Reduced sweat and oil gland activity

• Slower healing

Types of Burns and Complications

• First-degree: Only epidermis; redness, pain, no blisters.

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

• Third-degree: Full thickness; may appear white, leathery, painless (nerve endings destroyed).

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

Rule of Nines

Used to estimate the percentage of body surface area affected by burns.

Body Region	Percentage
Head and Neck	9%
Each Upper Limb	9%
Each Lower Limb	18%
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 between the layers.

Skin Diseases and Epidermal Derivatives

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

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

Skin Color and Health

• Skin color is influenced by melanin, carotene, and hemoglobin.

• Changes in color can indicate health issues (e.g., cyanosis, jaundice, pallor).

Skeletal System

Functions of the Skeletal System

• Support

• Protection

• Movement (leverage for muscles)

• Mineral storage (calcium, phosphate)

• Blood cell formation (hematopoiesis)

• Triglyceride storage

Classification of Bones by Shape

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

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

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

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

• Sesamoid bones: Embedded in tendons (e.g., patella)

General Features of a Long Bone

• Diaphysis: Shaft, compact bone surrounding medullary cavity

• Epiphyses: Ends, spongy bone covered by compact bone

• Metaphysis: Region between diaphysis and epiphysis

• Articular cartilage: Covers joint surfaces

• Periosteum: Outer fibrous covering

• Endosteum: Lines internal surfaces

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, organized in osteons

• Spongy bone: Porous, trabecular, found in epiphyses and 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, clavicle)

• Endochondral ossification: Forms most bones from hyaline cartilage templates

Bone Maintenance

• Bone remodeling: continuous resorption and deposition

• Influenced by mechanical stress, hormones, and nutrition

Nutrition and Bone Maintenance

• Calcium, vitamin D, protein, and other minerals 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

• Sex hormones: promote bone growth and closure of epiphyseal plates

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 (shoulder and pelvic)

Vertebrae and Vertebral Regions

• Parts: body, vertebral arch, processes, foramen

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

Joints: Types, Structures, and Functions

• Fibrous: Bones joined by dense connective tissue (e.g., sutures)

• Cartilaginous: Bones joined by cartilage (e.g., intervertebral discs)

• Synovial: Bones separated by a joint cavity, freely movable (e.g., knee, shoulder)

Knee Joint Features

• Largest synovial joint; contains menisci, ligaments (ACL, PCL, MCL, LCL), bursae

Joint Movements and Limitations

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

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

Joint Disorders

• Arthritis (osteoarthritis, rheumatoid arthritis), bursitis, tendonitis, dislocations

Associated Structures: Tendons, Ligaments, Bursae, Tendon Sheaths

• Tendons: Connect muscle to bone

• Ligaments: Connect bone to bone

• Bursae: Fluid-filled sacs reducing friction

• Tendon sheaths: Tubular bursae surrounding tendons