Integumentary System

Overview and Components

The integumentary system is the body's largest organ system, providing protection, sensation, and regulation. It consists of five main parts, each with distinct functions:

• Epidermis: Outermost layer; provides a waterproof barrier and creates skin tone.

• Dermis: Beneath the epidermis; contains tough connective tissue, hair follicles, and sweat glands.

• Hypodermis (Subcutaneous Layer): Made of fat and connective tissue; insulates and cushions the body.

• Accessory Structures: Includes hair, nails, and glands (sebaceous, sweat, and ceruminous).

• Nerve Endings: Detect touch, temperature, and pain.

Cell Types in the Epidermis

• Keratinoctyes: Produce keratin, a protein that strengthens the skin.

• Melanocytes: Produce melanin, which protects against UV radiation.

• Langerhans Cells: Immune cells that help detect pathogens.

• Merkel Cells: Sensory receptors for touch.

Layers of the Epidermis

• Stratum Basale: Deepest layer; site of cell division.

• Stratum Spinosum: Provides strength and flexibility.

• Stratum Granulosum: Cells begin to die and keratinize.

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

• Stratum Corneum: Outermost layer; dead, keratinized cells provide a barrier.

Functions of the Skin

• Protection: Physical (keratin), chemical (acid mantle), and biological (immune cells) barriers.

• Body Temperature Regulation: Sweat glands and blood vessels help dissipate or conserve heat.

• Cutaneous Sensation: Sensory receptors detect environmental changes.

Glands of the Skin

• Sebaceous Glands: Secrete sebum for lubrication and waterproofing.

• Sudoriferous (Sweat) Glands: Eccrine (thermoregulation) and apocrine (odor) types.

• Ceruminous Glands: Produce earwax in the ear canal.

Skin Layers: Dermis vs. Epidermis vs. Subcutaneous

• Epidermis: Stratified squamous epithelium; avascular.

• Dermis: Dense irregular connective tissue; vascular, contains nerves and glands.

• Subcutaneous Layer: Loose connective and adipose tissue; insulates and anchors skin.

Clinical Considerations

• Malfunction: Leads to increased infection risk, dehydration, and impaired sensation.

• Burns: Destroys protective barrier, leading to fluid loss and infection.

• UV Radiation: Damages DNA in skin cells, increasing cancer risk.

Chapter 6

Skeletal System

Types of Skeletal Cartilage

• Hyaline Cartilage: Most abundant; provides support and flexibility (found in nose, trachea, articular surfaces).

• Elastic Cartilage: Contains elastic fibers; maintains shape (found in ear, epiglottis).

• Fibrocartilage: Highly compressible; resists tension (found in intervertebral discs, pubic symphysis).

Cartilage Growth

• Appositional Growth: New layers added to the surface.

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

Bone Membranes

• Periosteum: Outer membrane; contains nerves and blood vessels.

• Endosteum: Lines internal bone surfaces; involved in bone growth and repair.

Functions of Bone

• Support

• Protection

• Movement

• Mineral storage

• Blood cell formation (hematopoiesis)

• Triglyceride storage

• Hormone production

Bone Classification

• 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).

Bone Structure: Spongy vs. Compact

• Compact Bone: Dense, provides strength.

• Spongy Bone: Lattice-like, contains red marrow.

Bone Marrow

• Red Marrow: Hematopoiesis; found in spongy bone.

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

Bone Cells

• Osteogenic Cells: Stem cells.

• Osteoblasts: Build bone matrix.

• Osteocytes: Maintain bone tissue.

• Osteoclasts: Break down bone matrix.

Bone Growth and Remodeling

• Postnatal Growth: Occurs at the epiphyseal plate via endochondral ossification.

• Remodeling: Continuous bone resorption and deposition; regulated by hormones and mechanical stress.

Fractures and Repair

• Types: Simple, compound, comminuted, greenstick, etc.

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

Calcium Homeostasis

• Maintained by parathyroid hormone (PTH) and calcitonin.

• Bone acts as a reservoir for calcium ions.

chapter 8

Joints (Articulations)

Structural and Functional Classification

• Structural: Fibrous, cartilaginous, synovial (with subtypes).

• Functional: Synarthroses (immovable), amphiarthroses (slightly movable), diarthroses (freely movable).

Synovial Joints

• Types: Plane, hinge, pivot, condyloid, saddle, ball-and-socket.

• Movements: Gliding, angular (flexion, extension, hyperextension, abduction, adduction, circumduction), rotation (lateral, medial).

• Features: Articular cartilage, joint cavity, synovial fluid, articular capsule, ligaments, nerves/blood vessels.

• Stability: Determined by shape, ligaments, and muscle tone.

Major Synovial Joints

• Shoulder: Ball-and-socket; stabilized by ligaments (coracoacromial, coracohumeral, glenohumeral), bursae, and rotator cuff muscles.

• Knee: Hinge; stabilized by menisci, collateral/cruciate ligaments, patellar ligament, and surrounding muscles.

Joint Injuries and Repair

• Impact: Injuries can damage cartilage, ligaments, or bone, affecting stability and movement.

• Repairability: Cartilage heals poorly due to low vascularity; ligaments and bone have better repair potential.