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

Chapter 5: The Integumentary System

Structure and Function of the Epidermis

The epidermis is the outermos

t layer of skin, composed of keratinized stratified squamous epithelium. It provides protection and houses several specialized cell types.

• Keratinocytes: Most abundant cells; produce keratin, a tough, fibrous protein that protects skin.

• Melanocytes: Produce melanin pigment, protecting DNA from UV radiation.

• Dendritic (Langerhans) cells: Macrophages that ingest foreign substances and activate the immune system.

• Tactile (Merkel) cells: Sensory receptors for touch; include free nerve endings, Meissner’s corpuscles (dermal papillae), Pacinian corpuscles (reticular dermis).

Layers of the Epidermis

The epidermis consists of several layers, each with distinct cell types and functions.

• Stratum corneum: 20-30 layers of keratinized cells; accounts for most of epidermal thickness.

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

• Stratum granulosum: 1-5 layers; keratinocyte appearance changes drastically.

• Stratum spinosum: Contains melanin granules and dendritic cells.

• Stratum basale: Single row of keratinocyte stem cells; site of mitosis.

Constant sun exposure stimulates callus formation in the stratum corneum.

Structure and Function of the Dermis

The dermis is a connective tissue layer beneath the epidermis, providing structural support and nourishment.

• Tissue type: Connective tissue with collagen and elastic fibers; vascular.

• Papillary region: Loose areolar connective tissue.

• Reticular region: Dense irregular connective tissue; contains scattered adipose tissue.

Skin Color and Associated Conditions

Skin color is determined by several pigments and can indicate health conditions.

• Carotene: Yellow-orange pigment from foods; accumulates in stratum corneum and adipose tissue.

• Hemoglobin: Red pigment in RBCs; causes erythema (reddened skin), indicating fever, hypertension, inflammation, or allergy.

• Cyanosis: Blue skin due to poorly oxygenated blood.

• Pallor: Pale skin; may indicate anemia, low blood pressure, or shock.

• Jaundice: Yellow skin; indicates liver disorder.

• Bronze color: Metallic appearance; sign of Addison’s disease.

• Bruise: Blood clotted beneath skin.

Hypodermis (Subcutaneous Layer)

The hypodermis is a layer deep to the dermis, not technically part of the skin.

• Tissue type: Loose areolar connective tissue and adipose tissue.

• Location: Deep to the dermis.

Hair and Hair Follicles

Hair is composed of dead keratinized cells and grows from follicles embedded in the dermis.

• Structure: Shaft (keratinization complete), root (keratinization ongoing), root plexus (sensory nerve endings).

• Layers: Medulla (core), cortex (bulky layer), cuticle (outermost layer).

• Hair follicle: Epidermal cells fold into dermis; bulb (deep end), papilla (center, contains capillaries), matrix (actively dividing area).

• Arrector pili muscle: Causes piloerection (goosebumps).

Types of Hair

• Vellus hair: Fine, nonpigmented; found in children and adult females.

• Terminal hair: Coarse, pigmented; found in eyebrows, scalp.

Nails

Nails are scalelike modifications of the epidermis, protecting the distal digits.

• Regions: Free edge, nail plate/body, proximal root.

• Nail bed: Deepest layer of epidermis.

• Nail matrix: Responsible for nail growth.

• Cuticle: Skin fold around nail.

Glands of the Skin

• Sweat (Sudoriferous) glands: Eccrine (merocrine), apocrine, ceruminous, mammary.

• Eccrine glands: Thermoregulation; most numerous; excrete waste.

• Apocrine glands: Function at puberty; produce odor; located in axillary/anogenital regions.

• Ceruminous glands: Modified sweat glands; secrete earwax.

• Mammary glands: Modified sweat glands; secrete milk.

• Oil (Sebaceous) glands: Produce sebum (oil); protects against bacterial growth, prevents water loss; empties into hair follicles.

• Acne: Inflammation of sebaceous glands due to bacteria in sebum.

Functions of the Integumentary System

• Protection: Chemical (acid mantle, melanin), physical (keratin), biological (immune cells).

• Thermoregulation: Eccrine sweat glands, blood vessel dilation/constriction.

• Cutaneous sensation: Sensory receptors (Merkel cells, Meissner’s corpuscles, Pacinian corpuscles).

• Metabolic functions: Vitamin D synthesis from cholesterol via UV light.

• Blood reservoir: Dermal vascular supply holds ~5% of blood volume.

• Excretion: Water, electrolytes, fatty acids, lactic acid, nitrogen compounds.

Skin Disorders

• Skin cancers: Basal cell carcinoma (least malignant, most common), squamous cell carcinoma (second most common), melanoma (most severe, metastasizes).

• ABCDE rule: Asymmetry, Border irregularity, Color, Diameter (>6mm), Evolving.

• Burns: Rule of Nines (body divided into 11 sections, each 9%); partial thickness (first/second degree), full thickness (third degree).

• Psoriasis: Chronic autoimmune condition with silvery scales.

• Albinism: Inherited lack of melanin synthesis.

• Alopecia: Absence of hair.

• Boils/carbuncles: Inflammation of hair follicles/sebaceous glands.

• Cold sores: Fluid-filled blisters.

• Rosacea: Chronic skin eruption with dilated blood vessels.

Chapter 6: Bones and Skeletal Tissues

Types and Locations of Cartilage

• Hyaline cartilage: Articular, costal, respiratory, nasal, embryonic precursor.

• Elastic cartilage: External ear, epiglottis.

• Fibrocartilage: Meniscus, intervertebral discs, pubic symphysis.

Cartilage Growth

• Appositional growth: New matrix secreted on external face; increases diameter.

• Interstitial growth: Chondrocytes divide within lacunae; increases length.

Functions of Bones

• Support: Framework for body and organs.

• Protection: Skull, vertebrae, rib cage.

• Movement: Levers for muscles.

• Mineral storage: Calcium, phosphate.

• Blood cell formation: Hematopoiesis in red marrow.

• Triglyceride storage: Fat in bone cavities.

• Hormone production: Osteocalcin regulates insulin.

Classification of Bones

• Flat bones: Sternum, scapulae, ribs, skull bones.

• Irregular bones: Vertebrae, coxal bones.

• Short bones: Carpals, tarsals, patella.

• Long bones: Humerus, femur, tibia, etc.

Bone Structure

• Compact bone: Dense, smooth, lamellar.

• Spongy bone: Trabecular, latticework.

• Diaphysis: Shaft; contains marrow cavity.

• Epiphysis: Ends; articulates with other bones.

• Epiphyseal plate: Hyaline cartilage for length growth.

• Epiphyseal line: Remnant of plate.

• Periosteum: Double-layered membrane; anchored by Sharpey’s fibers.

• Nutrient foramen: Opening for nerves/blood vessels.

• Endosteum: Lines marrow cavity and trabeculae.

• Hematopoietic tissue: Red marrow (becomes yellow with age).

Bone Markings

Bone markings provide sites for muscle/ligament attachment, joint surfaces, and passageways for nerves/vessels.

• Projections: Tuberosity, crest, trochanter, line, tubercle, epicondyle, spine, process.

• Joint-forming: Head, facet, condyle, ramus.

• Depressions/openings: Groove, fissure, foramen, notch, meatus, sinus, fossa.

Bone Cells

• Osteoblasts: Bone-forming; secrete matrix; deposit calcium.

• Osteocytes: Mature bone cells; regulate remodeling and homeostasis.

• Osteoclasts: Bone-resorbing; secrete enzymes and acids.

Microscopic Structure of Bone

• Osteon (Haversian system): Structural unit; contains lamellae (matrix tubes).

• Lacunae: Spaces housing osteocytes.

• Canaliculi: Tiny canals connecting osteocytes.

• Central canal: Contains blood vessels/nerves.

• Perforating (Volkmann’s) canals: Allow vessels to enter bone from periosteum.

• Osteoid: Organic matrix produced by osteoblasts.

Bone Development and Growth

• Ossification: Bone formation.

• Endochondral ossification: Replaces hyaline cartilage; forms most bones below skull (except clavicle).

• Intramembranous ossification: Forms from fibrous membrane; creates flat cranial bones and clavicles.

• Postnatal growth: Interstitial growth at epiphyseal plate; bone remodeling (deposition by osteoblasts, resorption by osteoclasts).

• Hormonal regulation: Calcitonin (stimulates osteoblasts), PTH (stimulates osteoclasts).

Bone Fractures and Repair

• Simple (closed): Bone does not penetrate skin.

• Compound (open): Bone penetrates skin.

• Types: Comminuted, compression, spiral, epiphyseal, depressed, greenstick.

• Repair steps: 1. Hematoma forms; 2. Fibrocartilaginous callus; 3. Bony callus; 4. Remodeling.

Bone Disorders

• Osteomalacia: Poor mineralization.

• Rickets: Children's version; bowed legs.

• Osteoporosis: Bone resorption exceeds deposition; decreased estrogen is a major cause.

• Paget’s Disease: Excessive, haphazard bone deposit/resorption.

Chapter 7: The Skeleton

Components and Organization

• Skeleton: Bones, cartilages, joints, ligaments.

• Total bones: 206.

• Axial skeleton: 80 bones; skull, vertebral column, thoracic cage.

• Appendicular skeleton: 126 bones; limbs, girdles.

Skull

• Total bones: 22.

• Cranial bones (8): Frontal, parietal (2), temporal (2), sphenoid, ethmoid, occipital.

• Facial bones (14): Nasal (2), lacrimal (2), zygomatic (2), inferior nasal concha (2), mandible, maxillae (2), palatine (2), vomer.

• Eye orbits: Formed by frontal, ethmoid, lacrimal, sphenoid, maxilla, zygomatic.

Major Sutures

• Coronal: Frontal and parietal.

• Squamous: Temporal and parietal.

• Sagittal: Parietal bones.

• Lambdoid: Occipital and parietal.

Fontanelles

• Anterior, posterior, sphenoidal, mastoid: Soft spots in newborns.

Hyoid Bone

• Does not articulate with other bones; attached to cervical vertebrae by ligaments.

Vertebral Column

• Total vertebrae: 26 irregular bones.

• Cervical: 7; C1 (Atlas, no body, "yes" motion), C2 (Axis, dens, "no" motion).

• Thoracic: 12; articulate with ribs.

• Lumbar: 5; thickest, weight-bearing.

• Sacral: 5 fused; forms sacroiliac joint.

• Coccyx: 4 fused; tailbone.

• Intervertebral discs: Fibrocartilage (annulus fibrosis) and nucleus pulposus; absorb shock.

• Herniated disc: Disc protrudes, compresses nerves.

Vertebral Curvatures

• Primary: Thoracic, sacral (convex).

• Secondary: Cervical, lumbar (concave).

Thoracic Cage

• Sternum: Manubrium, body, xiphoid process.

• Ribs: 12 pairs; 7 true (direct attachment), 5 false (indirect or floating), 2 floating (no attachment).

Pectoral (Shoulder) Girdle

• Scapula: Glenoid cavity, coracoid process, acromion, scapular spine.

• Clavicle: Articulates with sternum and scapula.

Upper Limb

• Humerus: Head articulates with scapula.

• Radius: Lateral, thumb side.

• Ulna: Medial, pinky side; olecranon process.

• Carpals: 8 wrist bones (scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, hamate).

• Metacarpals: 5.

• Phalanges: 14; thumb (2), digits 2-5 (3 each).

Pelvic Girdle

• Coxal bone: Ilium (superior), ischium (posterior), pubis (anterior).

• Pubic symphysis: Fibrocartilage joint.

• Female pelvis: Larger pelvic brim, wider pubic arch.

• Bone markings: Iliac crest, acetabulum, obturator foramen.

Lower Limb

• Femur: Head fits into acetabulum; largest bone.

• Tibia: Medial, weight-bearing.

• Fibula: Lateral.

• Tarsals: 7 (calcaneus, talus, navicular, cuneiforms, cuboid).

• Metatarsals: 5.

• Phalanges: 14; big toe (2), digits 2-5 (3 each).

Spinal Disorders

• Scoliosis: Lateral curvature.

• Lordosis: Exaggerated lumbar curvature.

• Kyphosis: Hunchback; exaggerated thoracic curvature.

Chapter 8: Joints

Classification of Joints

Joints (articulations) are points where two or more bones meet. They are classified by structure and function.

• Structural: Fibrous, cartilaginous, synovial.

• Functional: Synarthrotic (immovable), amphiarthrotic (slightly movable), diarthrotic (freely movable).

• Joint cavity: Present only in synovial joints.

Fibrous Joints

• Tissue: Fibrous connective tissue.

• Functional: Synarthrotic.

• Types: Sutures (skull), syndesmoses (ligament between tibia/fibula, radius/ulna), gomphoses (tooth in alveolar process).

• Sutures: Develop into synostoses (ossified) with age.

Cartilaginous Joints

• Types: Synchondroses (hyaline cartilage; epiphyseal plate, manubrium/first rib), symphyses (fibrocartilage; pubic symphysis, intervertebral joints).

• Functional: Synchondroses (immovable), symphyses (slightly movable).

Synovial Joints

• Functional: Diarthrotic (freely movable).

• Anatomy: Articular cartilage (hyaline), joint cavity, articular capsule (fibrous layer, synovial membrane), synovial fluid, reinforcing ligaments, nerves/blood vessels.

• Synovial fluid: Reduces friction, weight-bearing.

• Reinforcing ligaments: Capsular/extracapsular; stabilize joints.

• Nerves/blood vessels: Monitor position/stretch; blood forms synovial fluid.

Bursae and Tendon Sheaths

• Bursae: Bags of synovial fluid; reduce friction.

• Tendon sheaths: Elongated bursae around tendons.

Stability of Synovial Joints

• Articular surfaces: Shape affects stability/range of motion (e.g., hip vs. shoulder).

• Ligaments: Unite bones, prevent excessive motion; more ligaments = stronger joint.

• Muscle tone: Low-level contraction keeps muscles ready.

• Intracapsular ligaments: ACL, PCL (knee stability).

• Extracapsular ligaments: MCL, LCL.

• Lateral knee injury: Damages medial meniscus, MCL, ACL.

Muscle Attachments

• Insertion: Attachment to movable bone.

• Origin: Attachment to immovable bone.

• Movement: Insertion moves toward origin.

Types of Synovial Joints

Type	Axes	Motion	Location
Planar	Nonaxial	Sliding/gliding	Intercarpal, intertarsal, vertebral facet joints
Hinge	Uniaxial	Flexion/extension	Elbow, knee, interphalangeal
Pivot	Uniaxial	Rotation	Atlanto-axial, proximal radio-ulnar
Condyloid	Biaxial	Rotation in two planes	Knuckle, wrist, jaw
Saddle	Biaxial	Rotation in two planes	Carpometacarpal (thumb)
Ball and Socket	Multiaxial	All planes	Shoulder, hip

Shoulder vs. Hip Joint

• Shoulder (glenohumeral): Scapula and humerus; shallow socket, longer ligaments; increased range of motion, decreased stability.

• Hip (coxal): Deeper acetabulum, shorter ligaments; decreased movement, increased stability.

• Hip is stronger; shoulder is more flexible.

Movements at Joints

• Flexion: Decreases angle; brings bones together.

• Extension: Increases angle; straightens joint.

• Hyperextension: Beyond straight line.

• Abduction: Limb away from midline.

• Adduction: Limb toward midline.

• Circumduction: Limb moves in all planes.

• Rotation: Circular motion; occurs at pivot, hip, shoulder, atlanto-axial joints.

Special Movements

• Supination: Radius and ulna parallel.

• Pronation: Radius crosses over ulna; palm posterior.

• Dorsiflexion: Foot bends upward.

• Plantar flexion: Foot points downward (e.g., ballerina).

• Inversion: Sole turns medially.

• Eversion: Sole turns laterally.

• Protraction: Anterior movement (e.g., jaw forward).

• Retraction: Posterior movement (e.g., jaw backward).

• Elevation: Lifting superiorly (e.g., closing jaw).

• Depression: Lowering (e.g., opening jaw).

• Opposition: Thumb touches fingers.

Joint Injuries and Disorders

• Sprain: Ligaments stretched/torn; slow healing; common in ankle, knee, lumbar spine.

• Dislocation (luxation): Bones forced out of alignment; can recur.

• Bursitis: Inflammation of bursa.

• Osteoarthritis: Degeneration with aging.

• Rheumatoid arthritis: Autoimmune, crippling.

• Gouty arthritis: Uric acid crystals in joints.