THE 4 PRIMARY TISSUES

Epithelial Tissue

Epithelial tissue forms the covering and lining of body surfaces and cavities, and is essential for protection, secretion, and absorption. It is characterized by closely packed cells with polarity and is supported by a basement membrane.

• Function: Covers, lines, secretes, and protects

• Key Features: Avascular, regenerates quickly, has polarity (apical vs. basal), tightly packed cells with Cell Adhesion Molecules (CAM)

• Supported by: Basement membrane (basal lamina + reticular lamina)

• Cancer term: Carcinoma = epithelial cancer

Types of Epithelial Tissue

• Simple Squamous: Diffusion and filtration. Found in alveoli, lining of blood vessels (endothelium), and body cavities (mesothelium). Example: Gas exchange in lung alveoli. Exam cue: "Know simple squamous = endothelium in blood vessels."

• Stratified Squamous: Many layers; protection. Keratinized = skin (epidermis), Non-keratinized = mouth, esophagus, anus, vagina. Exam cue: "Keratinized only in epidermis — know that."

• Simple Cuboidal: Secretion and absorption; found in kidney tubules and glands.

• Stratified Cuboidal: Protection; found in ducts of sweat and salivary glands.

• Simple Columnar: Absorption and secretion; found in stomach, intestines, gallbladder, uterine tubes. Contains microvilli and goblet cells.

• Pseudostratified Ciliated Columnar: Appears layered, but all cells touch the basement membrane. Found in trachea and respiratory passages. Exam cue: "If you see cilia and goblet cells together, that's respiratory epithelium — expect that question."

• Transitional: Stretches; found in urinary bladder, ureters, renal pelvis. Exam cue: "Transitional = urinary system — memorize that."

Connective Tissue

Connective tissue provides support, binds structures, and protects organs. It consists of specialized cells and an extracellular matrix made of fibers and ground substance.

• Components: Specialized cells + extracellular matrix (fibers + ground substance)

• Cancer term: Sarcoma = connective tissue cancer

• Fibers:

  • Collagen: Strength, resists stretch (Most common fiber — remember that)

  • Elastic: Stretch and recoil

  • Reticular: Framework support

CT Types & Where Found

• Loose (Areolar): Cushions organs; under epithelium

• Adipose: Stores fat; insulation

• Dense Regular: Parallel collagen — tendons and ligaments Exam cue: "Dense regular = tendons/ligaments."

• Dense Irregular: Non-parallel collagen — dermis, periosteum, joint capsules Exam cue: "Dense irregular = periosteum or capsule."

• Elastic CT: In vertebral ligaments

• Reticular CT: Structural framework in spleen, liver

• Cartilage:

  • Hyaline: Articular surfaces, trachea

  • Elastic: Ear, epiglottis

  • Fibrocartilage: Intervertebral discs, pubic symphysis

• Bone: Support, protection, mineral storage

• Blood: Transport of gases and nutrients

Important Structures

• Periosteum: Dense irregular CT covering bone

• Sharpey's fibers: Collagen fibers anchoring periosteum to bone Exam cue: "Know Sharpey's fibers anchor periosteum."

• Ligament: Bone to bone

• Tendon: Muscle to bone

Muscle Tissue

Muscle tissue is responsible for movement and force generation. It is classified by structure and function.

• Skeletal: Voluntary, striated, multinucleate

• Cardiac: Involuntary, striated, branched, intercalated discs

• Smooth: Involuntary, non-striated, found in walls of organs and blood vessels

Nervous Tissue

Nervous tissue enables communication, coordination, and control throughout the body. It consists of neurons and supporting glial cells.

• Function: Communication, coordination, control

• Cells:

  • Neurons: Transmit electrical impulses

  • Neuroglia (glial cells): Support, protect, and nourish neurons

• Found in: Brain, spinal cord, peripheral nerves

INTEGUMENTARY SYSTEM

Functions of the Integument

The integumentary system (skin and its derivatives) serves as the body's first line of defense and performs several vital functions.

• Protection

• Excretion

• Temperature regulation

• Melanin production

• Keratin production

• Vitamin D synthesis

• Lipid storage

• Sensation

• Immune defense

Layers of Skin

• Epidermis (Avascular Epithelial Layer): From superficial to deep: C L G S B — Come Let's Get Sun Burned

  • Stratum Corneum: Dead, keratinized cells

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

  • Stratum Granulosum: Keratin production

  • Stratum Spinosum: Strength, desmosomes

  • Stratum Basale: Mitosis, melanocytes, Merkel cells

• Dermis (Connective Tissue Layer):

  • Papillary Layer: Areolar CT, capillaries, nerves Exam cue: "Papillary = superficial; Reticular = deep — they love to ask that!"

  • Reticular Layer: Dense irregular CT, collagen & elastic fibers

• Subcutaneous (Hypodermis): Fat and loose CT; insulation Exam cue: "Hypodermis = subcutaneous = superficial fascia"

Accessory Structures

• Hair: Protection, sensory

  • Types: Lanugo (fetal), Angora (continuous), Definitive (limited growth)

• Nails: Modified epidermis; lunula = white crescent; eponychium = cuticle

• Sebaceous (Oil) Glands: Secrete sebum — waterproof, reduce friction

• Sweat Glands:

  • Apocrine: Odor areas (axilla, groin)

  • Merocrine (Eccrine): Thermoregulation (palms, soles)

  • Mammary: Modified sweat glands

Skin Color & Pigments

• Melanin: UV protection; made by melanocytes

• Carotene: Orange tint; stored in epidermis/fat

• Hemoglobin: Red tint in skin

• Albinism: No melanin due to missing enzyme Exam cue: "Know albinism is enzyme-related, not absence of melanocytes."

Skin Pathologies & Burns

• 1st Degree: Epidermis only; redness

• 2nd Degree: Epidermis & dermis; blisters

• 3rd Degree: Full thickness; may reach muscle, no pain if nerves destroyed Exam cue: "Burn degrees and what layers are affected — always on the exam."

Other Pathologies

• Melanoma ABCD: Asymmetry, Border irregular, Color variation, Diameter > 6 mm

• Acne: Sebaceous inflammation

• Alopecia: Hair loss

• Callus: Thick stratum corneum

• Urticaria: Hives

• Warts: HPV infection

• Decubitus ulcers: Pressure sores

• Gangrene: Tissue death

SKELETAL SYSTEM

Bone Functions

Bones provide structural support, protect organs, store minerals, produce blood cells, and enable movement through leverage.

• Support

• Mineral/fat storage

• Blood cell production

• Protection

• Leverage

Bone Classifications

• Sutural (skull joints)

• Irregular: Vertebra, pelvis

• Short: Carpals/tarsals

• Flat: Ribs, sternum

• Long: Femur, humerus

• Sesamoid: Patella

Bone Structure

• Diaphysis: Shaft; compact bone + medullary cavity

• Epiphysis: Ends; spongy bone

• Metaphysis: Between diaphysis and epiphysis

• Periosteum: Outer membrane (dense irregular CT)

• Endosteum: Lines medullary cavity

• Sharpey's Fibers: Anchor periosteum Exam cue: "Know Sharpey's fibers anchor periosteum."

Bone Cells

• Osteogenic: Stem cells — form osteoblasts

• Osteoblasts: Build matrix (osteoid)

• Osteocytes: Mature cells; maintain matrix

• Osteoclasts: Break down bone (osteolysis) Exam cue: "Know the order and what each does."

Bone Composition

• 2% Living cells (osteogenic, blast, cyte, clast)

Compact vs Spongy Bone

• Compact: Osteons (Haversian systems), strong outer shell

• Spongy: Trabeculae, lighter, holds red marrow Exam cue: "Expect diagram question on osteon parts."

Ossification

• Intramembranous: Bone forms directly (flat bones, skull, face)

• Endochondral: Bone replaces cartilage (long bones) Exam cue: "All bones except cranium/face = endochondral."

Bone Growth & Remodeling

• Growth at epiphyseal plate (cartilage → bone)

• When plate closes → epiphyseal line

• Hormones (growth hormone, calcitonin, parathyroid) regulate growth and Ca balance

• Remodeling = balance between osteoblasts and osteoclasts

Fracture Healing (4 Stages)

1. Hematoma formation

2. Fibrocartilaginous callus

3. Bony callus

4. Remodeling Exam cue: "Know the order — 4 stages in sequence."

Pathologies

• Osteoporosis: Weak, brittle bones (Ca loss)

• Osteopenia: Milder bone loss

• Osteomalacia (Rickets): Soft bones; vitamin D deficiency

• Osteoarthritis: Degenerative; wear of cartilage (non-inflammatory) Exam cue: "Osteoarthritis = non-inflammatory arthritis — write that down."

• Rheumatoid Arthritis: Autoimmune inflammation of joints

FLASHCARD SET (Condensed)

• Epithelial Tissue: Covers, lines, secretes, protects; avascular, regenerates fast

• Simple Squamous: Diffusion, filtration | Alveoli, capillaries, endothelium

• Stratified Squamous: Protection | Skin (keratinized), mouth/esophagus (non-keratinized)

• Simple Cuboidal: Secretion/absorption | Kidneys, glands

• Simple Columnar: Absorption/secretion | Stomach, intestines

• Pseudostratified Columnar: Cilia + mucus | Trachea

• Transitional: Stretches | Bladder

• Connective Tissue: Support, bind, protect | Most abundant tissue

• Dense Regular: Parallel collagen | Tendons, ligaments

• Dense Irregular: Non-parallel collagen | Dermis, periosteum

• Papillary Layer: Areolar CT | Superficial dermis

• Reticular Layer: Dense irregular CT | Deep dermis

• Hypodermis: Fat layer under dermis

• Melanoma ABCD: Asymmetry, Border, Color, Diameter > 6 mm

• Bone Functions: Support, Storage, Blood formation, Protection, Leverage

• Keratin: Waterproofing protein | Skin, hair, nails

• Melanin: Pigment — UV shield | Made by melanocytes

• 1st/2nd/3rd Degree Burns: Epidermis // Dermis // Full-thickness

• Osteoblast: Builds bone

• Osteoclast: Breaks bone

• Osteocyte: Maintains bone

• Ossification: Bone formation (intramembranous or endochondral)

• Fracture Healing: Hematoma → Fibrocartilage → Bony Callus → Remodeling

• Osteoarthritis: Degenerative, non-inflammatory

• Rheumatoid Arthritis: Autoimmune joint inflammation

Key Table: Types of Epithelial Tissue

Key Table: Bone Cells

Key Equations & Terms

• Ossification:

• Fracture Healing Stages:

• Bone Remodeling: