Integumentary System (Chapter 5)

Function of the Integumentary System

The integumentary system is the body's first line of defense and serves multiple vital functions.

• Protection: Shields internal tissues from mechanical damage, pathogens, and dehydration.

• Regulation: Maintains body temperature through sweat and blood flow.

• Sensation: Contains sensory receptors for touch, pain, and temperature.

• Excretion: Removes waste products via sweat.

• Synthesis: Produces vitamin D when exposed to sunlight.

Layers of Skin: Order and Characteristics

The skin consists of three main layers, each with distinct features and functions.

• Epidermis: Outermost layer; composed of keratinized stratified squamous epithelium. Contains several sublayers (strata).

• Dermis: Middle layer; contains connective tissue, blood vessels, nerves, and glands. Divided into papillary and reticular layers.

• Hypodermis (Subcutaneous Layer): Deepest layer; made of adipose and areolar tissue, provides insulation and cushioning.

Epidermis: Fibers, Cells, and Layer Functions

The epidermis is composed of specialized cells and fibers that contribute to its protective role.

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

• Melanocytes: Produce melanin, which gives skin its color and protects against UV radiation.

• Langerhans Cells: Immune cells that help defend against pathogens.

• Strata: Includes stratum basale (deepest), stratum spinosum, stratum granulosum, stratum lucidum (in thick skin), and stratum corneum (outermost).

Apoptosis

Apoptosis is the process of programmed cell death, essential for removing damaged or unnecessary cells in the epidermis.

• Role: Maintains healthy skin by shedding dead cells from the surface.

Dermis: Layers, Characteristics, and Vascularity

The dermis provides structural support and houses various skin appendages.

• Papillary Layer: Thin, superficial layer with dermal papillae that form fingerprints.

• Reticular Layer: Thicker, deeper layer with dense irregular connective tissue.

• Vascularity: Rich blood supply supports skin nutrition and thermoregulation.

Stratum Basale and Dermal Papillae

The stratum basale is the deepest epidermal layer, responsible for cell division. Dermal papillae are projections that increase surface area for nutrient exchange and form fingerprints.

Incision Directions and Cleavage Lines

Cleavage lines (Langer's lines) are patterns of collagen fibers in the dermis. Surgeons use these lines to guide incisions for better healing.

• Additional info: Knowledge of cleavage lines helps minimize scarring.

Blisters

Blisters are fluid-filled pockets between skin layers, usually caused by friction, burns, or disease.

Skin Color: Pigments

Skin color is determined by three main pigments:

• Melanin: Brown-black pigment produced by melanocytes.

• Carotene: Yellow-orange pigment from diet, stored in the stratum corneum.

• Hemoglobin: Red pigment in blood, visible in fair skin.

Hair: Structure, Function, and Types

Hair serves protective and sensory functions and varies in type and color.

• Structure: Shaft (visible part), root (embedded in skin), bulb (base of follicle), arrector pili muscle (causes hair to stand).

• Function: Protection, sensation, and temperature regulation.

• Types: Vellus (fine, unpigmented), terminal (thick, pigmented).

• Color: Determined by melanin type and amount.

Nails: Structure and Function

Nails are protective coverings on fingers and toes, aiding in grasping and manipulation.

• Parts: Nail plate, nail bed, matrix (growth area), lunula (white crescent).

• Function: Protection and support for fingertips.

Glands: Types and Functions

Skin contains several types of glands with distinct secretions and roles.

• Sudoriferous (Sweat) Glands: Eccrine (widely distributed, regulate temperature) and apocrine (found in axillary/genital areas, active after puberty).

• Sebaceous Glands: Secrete sebum (oil) for lubrication and waterproofing.

• Ceruminous Glands: Produce earwax in the ear canal.

Functions and Descriptions of Skin Functions

• Protection

• Temperature regulation

• Sensation

• Excretion

• Vitamin D synthesis

Homeostatic Imbalances

Disorders of the skin can disrupt its normal functions.

• Examples: Acne, eczema, psoriasis.

Skin Cancer: Types and Detection

Skin cancer is classified by cell type and malignancy.

• Basal Cell Carcinoma: Most common, least dangerous.

• Squamous Cell Carcinoma: Second most common, can metastasize.

• Melanoma: Most dangerous, arises from melanocytes.

Detection uses the ABCD rule:

• A: Asymmetry

• B: Border irregularity

• C: Color variation

• D: Diameter > 6mm

Burns: Classification and Treatment

Burns are classified by depth and extent, with specific treatments for each type.

• First-degree: Superficial, affects epidermis.

• Second-degree: Affects epidermis and part of dermis.

  • Third-degree: Full thickness, destroys both layers.

Extent is evaluated using the "Rule of Nines" (divides body into regions, each representing 9% of total body surface area).

Skeletal System (Chapter 6)

Cartilages: Types and Locations

Cartilage is a flexible connective tissue found in various body parts.

• Hyaline cartilage: Most common; found in nose, trachea, ends of long bones.

• Elastic cartilage: Flexible; found in ear and epiglottis.

• Fibrocartilage: Tough; found in intervertebral discs and menisci.

Cartilage Growth

Cartilage grows by two mechanisms:

• Appositional growth: New layers added to the surface.

• Interstitial growth: Chondrocytes divide and expand within the tissue.

Functions of Bones

• Support: Framework for the body.

• Protection: Shields vital organs.

• Movement: Acts as levers for muscles.

• Mineral storage: Stores calcium and phosphorus.

• Blood cell formation: Occurs in bone marrow (hematopoiesis).

Types of Bones and Locations

• Long bones: Arms, legs (e.g., femur).

• Short bones: Wrists, ankles.

• Flat bones: Skull, ribs.

• Irregular bones: Vertebrae, pelvis.

Parts of a Long Bone

• Diaphysis: Shaft.

• Epiphysis: Ends.

• Metaphysis: Region between diaphysis and epiphysis.

• Medullary cavity: Central cavity containing marrow.

• Periosteum: Outer covering.

Bone Marrow

Bone marrow is the site of blood cell production.

• Red marrow: Produces blood cells.

• Yellow marrow: Stores fat.

Joints (Chapter 8)

Classification and Examples

Joints are classified by structure and function.

• Fibrous joints: Immovable (e.g., sutures in skull).

• Cartilaginous joints: Slightly movable (e.g., intervertebral discs).

• Synovial joints: Freely movable (e.g., knee, shoulder).

Synovial Joint Structure

Synovial joints have a complex structure allowing movement.

• Articular cartilage: Covers bone ends.

• Joint cavity: Contains synovial fluid.

• Synovial membrane: Produces synovial fluid.

• Ligaments: Stabilize the joint.

• Bursa: Fluid-filled sac reducing friction.

Steps of Bone Repair

Bone repair occurs in several stages:

1. Hematoma formation

2. Fibrocartilaginous callus formation

3. Bony callus formation

4. Bone remodeling

Bone Cells and Functions

Bone Growth and Hormonal Regulation

Bones grow via endochondral and intramembranous ossification. Parathyroid hormone regulates calcium levels.

• Endochondral ossification: Bone replaces cartilage (most bones).

• Intramembranous ossification: Bone develops from fibrous tissue (skull, clavicle).

homeostasis is maintained by parathyroid hormone (PTH) and calcitonin:

increases blood calcium by stimulating osteoclasts.

Fractures: Types and Repair

• Simple fracture: Bone breaks cleanly, does not penetrate skin.

• Compound fracture: Bone breaks and penetrates skin.

• Comminuted fracture: Bone shatters into multiple pieces.

Stress on Bones

Bones adapt to stress via remodeling, increasing strength where needed.

Sequence of Bone Repair

1. Hematoma formation

2. Fibrocartilaginous callus formation

3. Bony callus formation

4. Bone remodeling

Synovial Joint Labeling

Be able to identify and explain the following parts of a synovial joint:

• Articular cartilage

• Joint cavity

• Synovial membrane

• Ligaments

• Bursa

Additional info: This guide covers the essential concepts for exam preparation in Anatomy & Physiology, focusing on the integumentary system, skeletal system, and joints.