Study Guide: Integumentary System, Bones, Skeleton, and Joints (Chapters 5-8)

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Chapter 5 – The Integumentary System

Overview of the Integumentary System

The integumentary system is composed of the skin and its derivatives (hair, nails, glands). It serves as the body's first line of defense and performs multiple vital functions.

Protection: Acts as a barrier against mechanical, chemical, and biological hazards.
Thermoregulation: Regulates body temperature via sweat glands and blood vessel dilation/constriction.
Cutaneous Sensation: Contains sensory receptors for touch, pain, and temperature.
Metabolic Functions: Synthesizes vitamin D from cholesterol under UV light.
Blood Reservoir: Holds about 5% of the body's blood volume in the dermal vascular supply.
Excretion: Eliminates water, electrolytes, and metabolic wastes.

Structure of the Skin

Epidermis: Outermost layer; composed of keratinized stratified squamous epithelium.
Dermis: Middle layer; made of connective tissue (collagen and elastic fibers), contains blood vessels, nerves, and glands.
Hypodermis (Subcutaneous Layer): Deep to the dermis; consists of loose areolar and adipose tissue, not technically part of the skin.

Cells of the Epidermis

Keratinocytes: Most abundant; produce keratin, a tough, protective protein.
Melanocytes: Produce melanin pigment, protecting DNA from UV radiation.
Dendritic (Langerhans) Cells: Macrophages that activate the immune system.
Tactile (Merkel) Cells: Sensory receptors for touch.

Layers of the Epidermis (Superficial to Deep)

Stratum Corneum: 20-30 layers of dead, keratinized cells; thickest layer.
Stratum Lucidum: Present only in thick skin (palms, soles); absent in thin skin.
Stratum Granulosum: 1-5 layers; keratinocytes undergo major changes.
Stratum Spinosum: Contains melanin granules and dendritic cells.
Stratum Basale: Single row of mitotically active stem cells (keratinocytes).

Dermis Structure

Papillary Region: Loose areolar connective tissue; contains Meissner’s corpuscles (touch receptors).
Reticular Region: Dense irregular connective tissue; contains Pacinian corpuscles (deep pressure receptors) and scattered adipose tissue.

Skin Color

Melanin: Brown-black pigment produced by melanocytes.
Carotene: Yellow-orange pigment from plant foods; accumulates in stratum corneum and adipose tissue.
Hemoglobin: Red pigment in RBCs; gives skin a pinkish hue.

Clinical Correlations:

Cyanosis: Blue skin due to low oxygen (lack of hemoglobin).
Pallor: Pale skin, may indicate anemia or shock.
Jaundice: Yellow skin, indicates liver disorder.
Bronze color: May indicate Addison’s disease.
Bruises: Blood clotted beneath the skin.

Hair and Hair Follicles

Structure: Flexible strands of dead keratinized cells produced by follicles.
Layers: Medulla (core), cortex (bulky layer), cuticle (outermost, overlapping cells).
Hair Follicle: Extends from epidermis into dermis; contains hair bulb, papilla (capillaries), and matrix (growth zone).
Arrector Pili Muscle: Smooth muscle causing hair to stand (goosebumps).
Types of Hair: Vellus (fine, nonpigmented; children, females), Terminal (coarse; scalp, eyebrows).

Nails

Structure: Scalelike modification of epidermis; consists of free edge, nail plate, and root.
Nail Bed: Deeper epidermal layer.
Nail Matrix: Responsible for nail growth.
Cuticle: Skin fold around the nail.

Glands of the Skin

Sudoriferous (Sweat) Glands: Eccrine (thermoregulation, all over body), Apocrine (odor, axillary/anogenital), Ceruminous (earwax), Mammary (milk).
Sebaceous (Oil) Glands: Produce sebum (oil) for lubrication and antibacterial action; empties into hair follicles.

Skin Disorders

Acne: Inflammation of sebaceous glands.
Psoriasis: Autoimmune, scaly skin patches.
Albinism: Lack of melanin production.
Alopecia: Hair loss.
Boils/Carbuncles: Infected hair follicles/sebaceous glands.
Cold Sores: Herpes simplex virus blisters.
Rosacea: Chronic facial redness.

Skin Cancer

Basal Cell Carcinoma: Least malignant, most common, rarely metastasizes.
Squamous Cell Carcinoma: Second most common.
Melanoma: Most dangerous, highly metastatic.

ABCDE Rule for Melanoma:

A: Asymmetry
B: Border irregularity
C: Color variation
D: Diameter > 6 mm
E: Evolving (changes over time)

Burns

Rule of Nines: Body divided into 11 regions, each 9% of surface area (genitals 1%).
First-degree: Epidermis only.
Second-degree: Epidermis and dermis; blisters form.
Third-degree: Full thickness; destroys nerves, risk of dehydration and infection.

Chapter 6 – Bones and Skeletal Tissues

Cartilage Types and Growth

Hyaline Cartilage: Most abundant; found in articular surfaces, costal cartilage, respiratory tract, nose, embryonic skeleton.
Elastic Cartilage: Flexible; found in external ear, epiglottis.
Fibrocartilage: Strong, compressible; found in intervertebral discs, menisci, pubic symphysis.

Growth:

Appositional: New matrix added to surface (increases width).
Interstitial: Chondrocytes divide within matrix (increases length).

Functions of Bones

Support: Framework for body and soft organs.
Protection: Skull, vertebrae, and rib cage protect vital organs.
Movement: Levers for muscles.
Mineral Storage: Calcium and phosphate.
Blood Cell Formation: Hematopoiesis in red marrow.
Triglyceride Storage: Fat in yellow marrow.
Hormone Production: Osteocalcin regulates insulin.

Classification of Bones

Long Bones: Longer than wide (e.g., femur, humerus).
Short Bones: Cube-shaped (e.g., carpals, tarsals, patella).
Flat Bones: Thin, curved (e.g., sternum, skull bones).
Irregular Bones: Complex shapes (e.g., vertebrae, hip bones).

Bone Structure

Diaphysis: Shaft; contains medullary cavity.
Epiphysis: Ends; articulates with other bones.
Epiphyseal Plate/Line: Growth plate (hyaline cartilage); becomes line after growth.
Periosteum: Double-layered membrane; attached by Sharpey’s fibers.
Endosteum: Lines marrow cavity and trabeculae.
Hematopoietic Tissue: Red marrow (active in infants, replaced by yellow marrow in adults).

Bone Markings

Bone markings serve as attachment sites, joint surfaces, and passageways for vessels and nerves.

Type	Description	Example
Tuberosity	Large, rounded projection	Ischial tuberosity
Crest	Prominent ridge	Iliac crest
Trochanter	Large, blunt process	Greater trochanter
Line	Narrow ridge	Intertrochanteric line
Tubercle	Small rounded projection	Adductor tubercle
Epicondyle	Raised area above condyle	Medial epicondyle
Spine	Sharp, slender projection	Ischial spine
Process	Any bony prominence	Spinous process
Head	Bony expansion on neck	Head of rib
Facet	Flat articular surface	Facet of rib
Condyle	Rounded articular projection	Mandibular condyle
Ramus	Armlike bar	Mandibular ramus
Groove	Furrow	Mandibular groove
Fissure	Narrow slit	Superior orbital fissure
Foramen	Hole for vessels/nerves	Foramen magnum
Notch	Indentation at edge	Lesser sciatic notch
Meatus	Tubelike passage	External acoustic meatus
Sinus	Cavity in bone	Frontal sinus
Fossa	Shallow depression	Olecranon fossa

Bone Cells

Osteoblasts: Bone-forming cells; secrete matrix and deposit calcium.
Osteocytes: Mature bone cells; maintain matrix and regulate remodeling.
Osteoclasts: Bone-resorbing cells; secrete enzymes and acids to dissolve bone.

Microscopic Structure of Bone

Osteon (Haversian System): Structural unit of compact bone; concentric lamellae around a central canal.
Lacunae: Spaces containing osteocytes.
Canaliculi: Tiny canals connecting lacunae for nutrient/waste exchange.
Central (Haversian) Canal: Contains blood vessels and nerves.
Perforating (Volkmann’s) Canals: Perpendicular to central canals; connect periosteum to interior.
Osteoid: Organic matrix produced by osteoblasts.

Bone Development and Growth

Ossification: Process of bone formation.
Endochondral Ossification: Bone replaces hyaline cartilage; forms most bones below skull (except clavicle).
Intramembranous Ossification: Bone develops from fibrous membrane; forms flat bones of skull and clavicles.
Postnatal Growth: Interstitial growth at epiphyseal plate (length); appositional growth (width).
Bone Remodeling: Ongoing process of deposition (osteoblasts, stimulated by calcitonin) and resorption (osteoclasts, stimulated by PTH).

Bone Repair

Hematoma forms (clotted blood at fracture site).
Fibrocartilaginous callus forms (soft callus stabilizes bone).
Bony callus forms (spongy bone replaces soft callus).
Bone remodeling (restores original shape).

Bone Disorders

Osteomalacia: Poorly mineralized bones in adults.
Rickets: Osteomalacia in children; bowed legs.
Osteoporosis: Bone resorption exceeds deposition; decreased bone mass.
Paget’s Disease: Disorganized bone remodeling.

Chapter 7 – The Skeleton

Overview of the Skeleton

Total Bones: 206 in adult human skeleton.
Axial Skeleton: 80 bones (skull, vertebral column, thoracic cage).
Appendicular Skeleton: 126 bones (limbs, pectoral and pelvic girdles).

Skull

Cranial Bones (8): Frontal, parietal (2), temporal (2), occipital, sphenoid, ethmoid.
Facial Bones (14): Nasal (2), lacrimal (2), zygomatic (2), inferior nasal concha (2), mandible, maxillae (2), palatine (2), vomer.
Major Sutures: Coronal (frontal-parietal), sagittal (parietal-parietal), squamous (parietal-temporal), lambdoid (parietal-occipital).
Fontanelles: Soft spots in infant skull (anterior, posterior, sphenoidal, mastoid).
Hyoid Bone: Does not articulate with other bones; supports tongue.

Vertebral Column

Total Vertebrae: 26 (7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, 4 fused coccygeal).
Cervical (C1–C7): C1 (Atlas) supports skull, C2 (Axis) allows rotation.
Thoracic (T1–T12): Articulate with ribs.
Lumbar (L1–L5): Largest, support most weight.
Sacrum: 5 fused; forms sacroiliac joint.
Coccyx: 4 fused; tailbone.
Intervertebral Discs: Fibrocartilage (annulus fibrosus, nucleus pulposus); absorb shock.
Curvatures: Primary (thoracic, sacral – convex), Secondary (cervical, lumbar – concave).

Thoracic Cage

Sternum: Manubrium, body, xiphoid process.
Ribs: 12 pairs (7 true, 5 false [2 floating]).

Pectoral Girdle and Upper Limb

Pectoral Girdle: Scapula (shoulder blade), clavicle (collarbone).
Upper Limb Bones: Humerus, radius (lateral), ulna (medial), carpals (8), metacarpals (5), phalanges (14).

Pelvic Girdle and Lower Limb

Pelvic Girdle: Coxal bone (ilium, ischium, pubis); pubic symphysis (fibrocartilage joint).
Lower Limb Bones: Femur, tibia (medial, weight-bearing), fibula (lateral), tarsals (7), metatarsals (5), phalanges (14).
Sex Differences: Female pelvis has larger pelvic brim and pubic arch.

Spinal Disorders

Scoliosis: Lateral curvature.
Lordosis: Exaggerated lumbar curve.
Kyphosis: Exaggerated thoracic curve (hunchback).

Chapter 8 – Joints

Classification of Joints

Structural: Fibrous, cartilaginous, synovial.
Functional: Synarthrotic (immovable), amphiarthrotic (slightly movable), diarthrotic (freely movable).

Fibrous Joints

Connected by: Fibrous connective tissue.
Types: Sutures (skull), syndesmoses (ligament between tibia/fibula), gomphoses (tooth in socket).
Movement: Mostly synarthrotic.

Cartilaginous Joints

Connected by: Cartilage.
Types: Synchondroses (hyaline cartilage; e.g., epiphyseal plate, first rib-manubrium), symphyses (fibrocartilage; e.g., pubic symphysis, intervertebral discs).
Movement: Synchondroses (immovable), symphyses (slightly movable).

Synovial Joints

Features: Articular cartilage (hyaline), joint cavity, articular capsule (fibrous + synovial membrane), synovial fluid, reinforcing ligaments, nerves/blood vessels.
Movement: Diarthrotic (freely movable).
Bursae: Fluid-filled sacs reducing friction.
Tendon Sheaths: Elongated bursae around tendons.

Stability of Synovial Joints

Articular Surfaces: Shape affects range of motion and stability.
Ligaments: Unite bones, prevent excessive movement.
Muscle Tone: Keeps muscles and tendons taut.

Types of Synovial Joints

Type	Movement	Example
Plane (Nonaxial)	Gliding	Intercarpal, intertarsal
Hinge (Uniaxial)	Flexion/Extension	Elbow, knee
Pivot (Uniaxial)	Rotation	Atlas/axis, proximal radioulnar
Condyloid (Biaxial)	Flexion/Extension, Abduction/Adduction	Wrist, knuckle
Saddle (Biaxial)	Flexion/Extension, Abduction/Adduction	Thumb (carpometacarpal)
Ball-and-Socket (Multiaxial)	All movements	Shoulder, hip

Movements at Synovial Joints

Flexion: Decreases angle between bones.
Extension: Increases angle.
Hyperextension: Extension beyond anatomical position.
Abduction: Movement away from midline.
Adduction: Movement toward midline.
Circumduction: Circular movement.
Rotation: Bone turns around its own axis.
Special Movements: Supination/pronation (forearm), dorsiflexion/plantar flexion (ankle), inversion/eversion (foot), protraction/retraction (jaw), elevation/depression (jaw/shoulder), opposition (thumb).

Joint Injuries and Disorders

Sprain: Ligament stretched/torn; slow healing.
Dislocation (Luxation): Bones forced out of alignment; may recur.
Bursitis: Inflammation of bursa.
Osteoarthritis: Degenerative joint disease (aging).
Rheumatoid Arthritis: Autoimmune, crippling.
Gouty Arthritis: Uric acid crystal deposition in joints.

Shoulder vs. Hip Joint Comparison

Joint	Stability	Range of Motion	Socket Depth
Shoulder (Glenohumeral)	Less stable	Greater	Shallow
Hip (Coxal)	More stable	Less	Deep

Additional info: For all equations related to bone growth and calcium homeostasis, the following formula is relevant:

Calcium homeostasis is regulated by parathyroid hormone (PTH) and calcitonin: