Study Guide: Histology, Integumentary System, and Bone Structure (Ch. 4–6, ANP College Level)

Chapter 4: The Tissue Level of Organization (Histology)

Epithelial Tissues

Epithelial tissues cover body surfaces, line cavities, and form glands. They are specialized for protection, absorption, secretion, and sensation.

• Key Features: High cellularity, polarity (apical/basal), attachment to basement membrane, avascularity, rapid regeneration.

• Specializations: Cilia, microvilli, secretory cells, germinative (basal) layer.

Classification of Epithelia

• By Layers: Simple (one layer), Stratified (multiple layers)

• By Shape: Squamous (flat), Cuboidal (cube), Columnar (tall)

Simple Squamous Epithelium

• Structure: Single layer of flat cells

• Locations: Alveoli, blood vessels (endothelium), serous membranes (mesothelium), kidney tubules

• Functions: Diffusion, filtration, reduces friction

Simple Cuboidal Epithelium

• Structure: Single layer of cube-shaped cells

• Locations: Glands, ducts, kidney tubules, thyroid gland

• Functions: Secretion, absorption, limited protection

Simple Columnar Epithelium

• Structure: Single layer of tall cells, often with microvilli or goblet cells

• Locations: Stomach, intestines, gallbladder, uterine tubes

• Functions: Protection, secretion, absorption

Pseudostratified Columnar Epithelium

• Structure: Appears layered but all cells touch basement membrane; often ciliated with goblet cells

• Locations: Trachea, bronchi, nasal cavity, male reproductive tract

• Functions: Protection, secretion, movement of mucus by cilia

Stratified Squamous Epithelium

• Structure: Multiple layers; surface cells are flat

• Locations: Skin (keratinized), mouth, esophagus, anus, vagina (non-keratinized)

• Functions: Protection against abrasion, pathogens, chemicals

Transitional Epithelium

• Structure: Multiple layers; cells change shape (dome-shaped when relaxed, flat when stretched)

• Locations: Urinary bladder, ureters, renal pelvis

• Functions: Permits expansion and recoil after stretching

Connective Tissues (CT)

Connective tissues support, bind, and protect organs. They have specialized cells, protein fibers, and ground substance (matrix).

• Cell Types: Fibroblasts (make fibers), adipocytes (store fat), macrophages (phagocytes)

• Fiber Types: Collagen (strong), elastic (stretchy), reticular (network)

Areolar (Loose) Connective Tissue

• Structure: Loose arrangement of fibers, abundant ground substance

• Locations: Under epithelia, around organs

• Functions: Cushions organs, provides support, allows movement

Adipose Tissue

• Structure: Large, closely packed adipocytes (fat cells)

• Locations: Under skin, around eyes/kidneys, within abdomen

• Functions: Energy storage, insulation, cushioning

Dense Regular Connective Tissue

• Structure: Parallel collagen fibers, few cells

• Locations: Tendons, ligaments

• Functions: Strong attachment, resists pulling forces in one direction

Dense Irregular Connective Tissue

• Structure: Collagen fibers in multiple directions

• Locations: Dermis, organ capsules

• Functions: Withstands tension from many directions

Cartilage (Supportive CT)

• General Features: Chondrocytes in lacunae, avascular, firm matrix

• Types: Hyaline (most common), elastic, fibrocartilage

Hyaline Cartilage

• Structure: Glassy matrix, chondrocytes in lacunae

• Locations: Ends of long bones, nose, trachea, larynx, costal cartilage

• Functions: Support, reduces friction, absorbs shock

Bone (Osseous Tissue)

• Structure: Osteocytes in lacunae, hard mineralized matrix, organized in osteons (compact bone)

• Functions: Support, protection, movement, mineral storage, blood cell formation

Membranes

• Mucous Membranes: Line passages open to exterior; secrete mucus

• Serous Membranes: Line closed cavities; secrete serous fluid

• Cutaneous Membrane: Skin

• Synovial Membranes: Line joint cavities; secrete synovial fluid

Muscle Tissue

• Skeletal Muscle: Voluntary, striated, multinucleate

• Cardiac Muscle: Involuntary, striated, branched, intercalated discs

• Smooth Muscle: Involuntary, non-striated, spindle-shaped cells

Nervous Tissue

• Neurons: Conduct electrical impulses; have cell body, dendrites, axon

• Neuroglia: Support, protect, and nourish neurons

Tissue Injury and Repair

• Inflammation: Response to injury; involves swelling, redness, heat, pain

• Regeneration: Replacement of damaged tissue; varies by tissue type

Chapter 5: The Integumentary System (Skin)

Overview and Functions

The integumentary system includes the skin and its accessory structures (hair, nails, glands). It protects the body, regulates temperature, synthesizes vitamin D, and provides sensation.

• Protection: Physical, chemical, and biological barrier

• Excretion: Sweat removes wastes

• Storage: Fat, water, vitamins

• Sensation: Touch, pain, temperature

• Vitamin D Synthesis: UV light converts precursor to vitamin D3

• Thermoregulation: Sweat and blood flow control heat loss

Skin Structure

• Epidermis: Keratinized stratified squamous epithelium; main cell = keratinocyte

• Dermis: Connective tissue (papillary = areolar; reticular = dense irregular)

• Hypodermis: Subcutaneous layer; adipose + areolar tissue

Epidermal Layers (Deep to Superficial)

• Stratum basale (germinativum): Stem cells, melanocytes, Merkel cells

• Stratum spinosum: Keratinocytes, Langerhans cells

• Stratum granulosum: Keratin production, cells begin to die

• Stratum lucidum: Only in thick skin (palms, soles)

• Stratum corneum: Dead, keratinized cells; barrier layer

Other Epidermal Cells

• Melanocytes: Produce melanin (UV protection)

• Dendritic (Langerhans) cells: Immune defense

• Tactile (Merkel) cells: Sensory receptors

Skin Color Factors

• Melanin: Brown-black pigment from melanocytes

• Carotene: Yellow-orange pigment

• Hemoglobin: Red pigment in blood

Accessory Structures

• Hair: Protection, insulation, sensation

• Sebaceous glands: Secrete sebum (oil)

• Sudoriferous glands: Eccrine (watery sweat), apocrine (thicker, odor)

• Nails: Protect digits, aid grasping

Burns (by Depth)

• 1st degree: Epidermis only; red, no scar

• 2nd degree: Epidermis + part of dermis; blisters, may scar

• 3rd degree: Full thickness; white/charred, scars, infection risk

Skin Cancer

• Basal cell carcinoma: Most common, least dangerous

• Squamous cell carcinoma: Can metastasize

• Malignant melanoma: Most deadly; from melanocytes

Aging Effects

• Thinner skin, less elasticity, slower healing, gray hair, less sweat/sebum

Chapter 6: Osseous Tissue & Bone Structure

Functions of Bone

• Support, protection, movement, mineral storage, blood cell formation (hematopoiesis)

Classification by Shape

• Long, short, flat, irregular, sesamoid, sutural

Structure of Long Bones

• Diaphysis: Shaft; compact bone, medullary cavity (yellow marrow)

• Epiphysis: Ends; spongy bone (red marrow), articular cartilage

• Metaphysis: Growth zone (epiphyseal plate in children)

Bone Matrix

• Inorganic: 2/3 calcium phosphate (hydroxyapatite) – hardness

• Organic: 1/3 collagen fibers – flexibility

Bone Cells

• Osteoprogenitor: Stem cells

• Osteoblasts: Build bone matrix

• Osteocytes: Maintain matrix, in lacunae

• Osteoclasts: Break down bone (resorption)

Compact Bone Structure

• Organized in osteons (Haversian systems): central canal, concentric lamellae, lacunae, canaliculi, perforating canals

• Periosteum: Outer covering; Endosteum: Lines medullary cavity

Bone Development & Growth

• Osteogenesis: Bone formation

• Intramembranous ossification: Flat bones (skull)

• Endochondral ossification: Most bones; cartilage model replaced by bone

• Epiphyseal plate: Growth in length; closes at adulthood (epiphyseal line)

Fracture Repair

1. Hematoma (blood clot)

2. Fibrocartilaginous (soft) callus

3. Bony (hard) callus

4. Remodeling

Bone Homeostasis

• Balance between osteoblast and osteoclast activity

• Regulated by hormones (PTH, calcitonin, calcitriol), nutrition, exercise

Calcium Balance

• PTH: Raises blood Ca2+

• Calcitonin: Lowers blood Ca2+

• Calcitriol: Increases Ca2+ absorption in intestines

Aging and Bone Disorders

• Osteopenia: Bone thinning with age

• Osteoporosis: Severe bone loss; increased fracture risk

Quick Exam Tips

• Memorize tissue locations and functions

• Know skin layers and color factors

• Understand bone matrix and cell types

• Practice identifying tissues from images