Anatomy and Physiology: Integumentary System, Bone and Bone Tissue, Skeletal System, and Articulations (Chapters 5-8) Study Notes

Chapter 5: The Integumentary System

Overview of the Integumentary System

The integumentary system is the body's largest organ system, primarily composed of the skin (cutaneous membrane) and its accessory structures. It serves as the first line of defense and performs multiple vital functions.

• Skin (Cutaneous Membrane): Consists of two main layers: the epidermis (superficial, avascular) and the dermis (deep, vascular).

• Accessory Structures: Include hair, nails, sweat glands, and sebaceous glands, all derived from the epidermis but located in the dermis.

• Hypodermis (Subcutaneous Layer): Lies below the dermis, composed mainly of adipose tissue. It is not technically part of the skin but anchors it to underlying tissues and provides insulation.

Main Functions of the Integumentary System

• Protection: Physical barrier against pathogens, chemicals, and physical trauma.

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

• Thermoregulation: Regulates body temperature via sweat production and blood flow adjustments.

• Excretion: Eliminates waste products through sweat.

• Vitamin D Synthesis: Initiates synthesis of vitamin D when exposed to UV light.

Thermoregulation

• Hot Weather: Sweat glands produce sweat; blood vessels dilate (vasodilation) to release heat.

• Cold Weather: Blood vessels constrict (vasoconstriction) to conserve heat; arrector pili muscles contract, causing goosebumps.

Epidermis

• Location: Outermost (superficial) layer of skin.

• Tissue Type: Keratinized stratified squamous epithelium.

• Cells: Primarily keratinocytes (produce keratin), with melanocytes (produce melanin), Langerhans (dendritic) cells (immune defense), and Merkel cells (touch receptors).

• Main Protein: Keratin provides strength and waterproofing.

• Layers (from deep to superficial):

  • Stratum basale: Single row of stem cells; site of mitosis; contains melanocytes and Merkel cells.

  • Stratum spinosum: Several layers; contains Langerhans cells; cells appear spiny.

  • Stratum granulosum: 3-5 layers; cells contain granules of keratin and glycolipids.

  • Stratum lucidum: Present only in thick skin (palms, soles); thin, clear layer.

  • Stratum corneum: Outermost; many layers of dead, keratinized cells.

• Thick Skin: Found on palms and soles; has stratum lucidum; thicker stratum corneum; lacks hair and sebaceous glands.

• Thin Skin: Covers most of the body; lacks stratum lucidum; thinner stratum corneum; contains hair and sebaceous glands.

• Callus: Localized thickening of the stratum corneum due to repeated friction.

Dermis

• Location: Deep to the epidermis.

• Tissue Type: Connective tissue (areolar in papillary layer, dense irregular in reticular layer).

• Layers:

  • Papillary layer: Superficial; areolar connective tissue; contains dermal papillae (form fingerprints).

  • Reticular layer: Deep; dense irregular connective tissue; provides strength and elasticity.

• Functions: Supports epidermis, houses blood vessels, nerves, and accessory structures.

• Sensory Receptors:

  • Meissner (tactile) corpuscles: Detect light touch; located in papillary layer.

  • Pacinian (lamellated) corpuscles: Detect deep pressure and vibration; located in reticular layer.

Skin Markings

• Dermal Ridges: Thickened areas of dermis; form epidermal ridges (fingerprints).

• Tension (Cleavage) Lines: Patterns of collagen fiber bundles; important for surgical incisions.

• Flexure Lines: Skin folds at joints (e.g., palms, fingers).

Pigmentation and Melanin

• Melanin: Pigment produced by melanocytes in the stratum basale; protects keratinocytes from UV damage.

• Primary Function: Absorbs UV radiation, preventing DNA damage.

• Secondary Function: Contributes to skin color.

• Skin Tone Variation: Due to type and amount of melanin, carotene (yellow-orange pigment), and hemoglobin (red pigment in blood).

• Freckles: Localized overproduction of melanin.

• Mole (Nevus): Benign proliferation of melanocytes.

• Albinism: Genetic lack of melanin production.

• Color Changes:

  • Erythema: Redness (increased blood flow).

  • Pallor: Paleness (decreased blood flow).

  • Cyanosis: Bluish color (low oxygen).

Accessory Structures

• Hair:

  • Functions: Thermoregulation, protection (e.g., eyelashes, scalp).

  • Parts:

    • Shaft: Visible part above skin.

    • Root: Embedded in skin; contains papilla (blood supply) and matrix (growth zone).

  • Hair Follicle: Surrounds root; has epithelial and dermal sheaths.

  • Hair Structure: Medulla (core), cortex (middle), cuticle (outer layer).

  • Arrector Pili Muscle: Smooth muscle causing hair to stand (goosebumps).

  • Types of Hair: Lanugo (fetal), vellus (fine, body), terminal (thick, scalp, eyebrows).

• Nails:

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

  • Growth: Occurs from matrix; rate affected by age, nutrition, health.

• Sweat Glands:

  • Eccrine (merocrine): Most numerous; secrete watery sweat for cooling.

  • Apocrine: Found in axillae, groin; secrete thicker sweat; active at puberty.

  • Ceruminous: In ear canal; produce earwax.

  • Mammary: Produce milk.

• Sebaceous Glands:

  • Location: Associated with hair follicles.

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

  • Influence: Stimulated by hormones (androgens); can develop acne.

Chapter 6: Bone and Bone Tissue

Overview of the Skeletal System

The skeletal system consists of bones, joints, and supporting tissues. Bones are the main organs, providing structure, protection, and facilitating movement.

• Functions of the Skeletal System:

  1. Support

  2. Protection

  3. Movement

  4. Mineral storage (especially calcium and phosphate)

  5. Blood cell production (hematopoiesis)

  6. Fat storage (yellow marrow)

Classification and Structure of Bones

• Bone Types:

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

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

  • Flat bones: Thin, broad (e.g., skull, ribs).

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

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

• Long Bone Structure:

  • Periosteum: Dense connective tissue covering bone.

  • Perforating fibers: Anchor periosteum to bone.

  • Diaphysis: Shaft of long bone.

  • Epiphyses: Ends of long bone.

  • Marrow cavity: Contains yellow or red marrow.

  • Diploe: Spongy bone in flat bones.

• Blood and Nerve Supply: Bones are highly vascularized and innervated.

• Red vs. Yellow Marrow: Red marrow (hematopoietic) predominates in children; yellow marrow (fat storage) increases with age.

Bone Matrix and Cells

• Extracellular Matrix:

  • Inorganic matrix: Hydroxyapatite crystals (calcium phosphate) provide hardness.

  • Organic matrix (osteoid): Collagen fibers and ground substance provide flexibility.

• Bone Cells:

  • Osteoblasts: Build bone; secrete osteoid.

  • Osteocytes: Mature bone cells; maintain bone matrix.

  • Osteoclasts: Break down bone (resorption); large, multinucleated.

Compact and Spongy Bone Structure

• Compact Bone:

  • Osteon (Haversian system): Structural unit; concentric lamellae around a central canal.

  • Lamellae: Layers of bone matrix.

• Spongy Bone:

  • Trabeculae: Lattice-like network; spaces filled with marrow.

  • Lightweight but strong; resists stress from multiple directions.

Bone Formation and Growth

• Ossification (Osteogenesis): Process of bone formation.

• Intramembranous Ossification: Forms flat bones (skull, clavicle); four steps: mesenchymal cell differentiation, osteoid secretion, trabeculae formation, periosteum development.

• Endochondral Ossification: Forms most bones; four steps: cartilage model, bone collar formation, primary ossification center, secondary ossification center.

• Epiphyseal Plate/Line: Growth plate; site of longitudinal growth in children; becomes epiphyseal line in adults.

Bone Growth and Remodeling

• Longitudinal Growth: Occurs at epiphyseal plates; four steps: proliferation, hypertrophy, calcification, ossification.

• Appositional Growth: Increase in bone diameter; occurs throughout life.

• Bone Remodeling: Continuous process of bone deposition and resorption; adapts to stress.

• Hormonal Regulation:

  • Calcitonin: Increases bone deposition.

  • Parathyroid hormone (PTH): Increases bone resorption.

• Osteoporosis: Decreased bone mass; increased fracture risk.

• Osteopenia: Mild reduction in bone mass.

Fractures and Repair

• Simple (closed) fracture: Bone breaks but does not pierce skin.

• Compound (open) fracture: Bone pierces skin.

• Fracture Repair (Four Steps):

  1. Hematoma formation

  2. Fibrocartilaginous callus formation

  3. Bony callus formation

  4. Bone remodeling

Chapter 7: The Skeletal System

Overview of the Skeletal System

The human skeleton consists of approximately 206 bones, divided into axial and appendicular divisions, and associated cartilage.

• Axial Skeleton: Skull, vertebral column, and thoracic cage (ribs, sternum).

• Appendicular Skeleton: Limbs and girdles (shoulder and pelvic girdles).

Bone Markings

• Bone Markings: Projections, depressions, and openings on bones for attachment, articulation, and passage of vessels/nerves. (See Table 7.1 for details.)

Skull

• Cranial Bones: 8 bones; protect the brain.

• Facial Bones: 14 bones; form the face.

• Calvarium: Skullcap; upper part of the cranium.

• Sinuses: Four pairs: frontal, ethmoid, sphenoid, maxillary; air-filled spaces that lighten the skull and enhance voice resonance.

Vertebral Column

• Sections: Cervical (7), thoracic (12), lumbar (5), sacrum (5 fused), coccyx (4 fused).

• Spinal Curvatures: Cervical and lumbar (concave), thoracic and sacral (convex).

• Vertebra Anatomy: Body, vertebral arch, processes (spinous, transverse), vertebral foramen.

• Section Differences: Cervical (small, bifid spinous), thoracic (facets for ribs), lumbar (large, robust).

Thoracic Cage and Limbs

• Ribs: 12 pairs; true (1-7), false (8-12), floating (11-12).

• Upper Limb: Shoulder girdle (clavicle, scapula), humerus, radius, ulna, carpals, metacarpals, phalanges.

• Lower Limb: Pelvic girdle (ilium, ischium, pubis), femur, tibia, fibula, tarsals, metatarsals, phalanges.

Chapter 8: Articulations

Overview of Joints (Articulations)

Joints connect bones and allow for movement and flexibility. They are classified by function and structure.

• Functions of Joints:

  1. Enable movement

  2. Provide stability

  3. Allow bone growth

• Functional Classification:

  • Synarthrosis: Immovable

  • Amphiarthrosis: Slightly movable

  • Diarthrosis: Freely movable

• Structural Classification:

  • Fibrous Joints: Bones joined by dense connective tissue; e.g., sutures (skull), syndesmoses (radius/ulna), gomphoses (teeth).

  • Cartilaginous Joints: Bones joined by cartilage; e.g., synchondroses (epiphyseal plate), symphyses (pubic symphysis).

  • Synovial Joints: Bones separated by a fluid-filled cavity; most movable type.

Synovial Joints

• Structural Elements: Articular cartilage, joint (synovial) cavity, articular capsule, synovial fluid, ligaments, nerves, and blood vessels.

• Stabilization: Ligaments, tendons, muscle tone, and joint capsule.

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

• Functional Classes:

  • Nonaxial: Gliding (plane joints)

  • Uniaxial: Hinge (elbow), pivot (atlas/axis)

  • Biaxial: Condylar (wrist), saddle (thumb)

  • Multiaxial: Ball-and-socket (shoulder, hip)

• Types of Synovial Joints: Plane, hinge, pivot, condylar, saddle, ball-and-socket.

Joint Disorders

• Arthritis: Inflammation of joints; main types include osteoarthritis, rheumatoid arthritis, and gouty arthritis.

Major Synovial Joints

• Knee Joint: Largest, most complex; hinge joint with menisci and ligaments.

• Shoulder Joint: Ball-and-socket; greatest range of motion; stabilized by rotator cuff muscles.

• Hip Joint: Ball-and-socket; deep socket provides stability.

Joint Type	Structural Features	Example	Movement
Plane	Flat surfaces	Intercarpal joints	Gliding
Hinge	Cylinder and trough	Elbow, knee	Flexion/Extension
Pivot	Rounded bone fits into ring	Atlas/axis	Rotation
Condylar	Oval articular surface	Wrist	Flexion/Extension, Abduction/Adduction
Saddle	Concave and convex areas	Thumb (carpometacarpal)	Flexion/Extension, Abduction/Adduction
Ball-and-socket	Spherical head fits into socket	Shoulder, hip	All movements

Additional info: For detailed bone markings and lab-specific lists, refer to your course's Table 7.1 and Lab List Exam 2. For more on the life cycle of keratinocytes and melanocytes, see histology resources.