Chapter 4: Tissues

Basic Tissue Types

The human body is composed of four basic tissue types, each with distinct structures and functions.

• Epithelial Tissue: Covers body surfaces, lines cavities, and forms glands. Functions include protection, absorption, secretion, and sensation.

• Connective Tissue: Supports, binds, and protects organs. Includes bone, cartilage, adipose, and blood.

• Muscle Tissue: Responsible for movement. Types include skeletal, cardiac, and smooth muscle.

• Nervous Tissue: Initiates and transmits electrical impulses, coordinating body activities.

Types of Epithelial Tissue

Epithelial tissues are classified by cell shape and number of layers.

• Shapes: Squamous (flat), cuboidal (cube-shaped), columnar (tall), transitional (variable shape).

• Layers: Simple (one layer), stratified (multiple layers), pseudostratified (appears layered but is not).

• Locations & Functions: For example, simple squamous epithelium lines blood vessels for diffusion; stratified squamous epithelium forms the skin for protection.

Cell Junctions

Cell junctions connect adjacent cells and maintain tissue integrity.

• Tight Junctions: Seal cells together, preventing passage of substances between them.

• Gap Junctions: Allow communication between cells via channels.

• Desmosomes: Provide strong adhesion between cells.

• Hemidesmosomes: Anchor cells to the basement membrane.

Exocrine Glands

Exocrine glands secrete substances onto epithelial surfaces.

• Merocrine Glands: Secrete via exocytosis (e.g., sweat glands).

• Apocrine Glands: Release part of the cell with secretion (e.g., mammary glands).

• Holocrine Glands: Entire cell disintegrates to release contents (e.g., sebaceous glands).

Connective Tissue Types

Connective tissues are classified as loose, dense, supportive, or fluid.

• Loose Connective Tissue: Areolar, adipose, reticular.

• Dense Connective Tissue: Dense regular, dense irregular, elastic.

• Supportive Connective Tissue: Cartilage (hyaline, elastic, fibrocartilage), bone.

• Fluid Connective Tissue: Blood, lymph.

Bone and Cartilage

Bone and cartilage are supportive connective tissues with distinct structures and functions.

• Bone: Rigid, supports and protects organs, stores minerals.

• Cartilage: Flexible, cushions joints, forms structures like the ear and nose.

• Comparison: Bone is vascular and hard; cartilage is avascular and flexible.

Dense Regular vs. Dense Irregular Connective Tissue

• Dense Regular: Collagen fibers aligned in parallel (e.g., tendons, ligaments).

• Dense Irregular: Collagen fibers in various directions (e.g., dermis of skin).

Types of Membranes

Body membranes line cavities and cover surfaces.

• Mucous Membranes: Line body cavities open to the exterior (e.g., digestive tract).

• Serous Membranes: Line closed cavities (e.g., pleura, pericardium).

• Synovial Membranes: Line joint cavities.

Connective Tissue Proper

• Loose Connective Tissue: Areolar, adipose, reticular.

• Dense Connective Tissue: Dense regular, dense irregular, elastic.

Muscle Tissue Types

• Skeletal Muscle: Striated, voluntary, attached to bones.

• Cardiac Muscle: Striated, involuntary, found in heart.

• Smooth Muscle: Non-striated, involuntary, found in walls of organs.

Nervous Tissue

• Neurons: Transmit electrical impulses.

• Neuroglia: Support and protect neurons.

• Cell Body, Dendrites, Axon: Main parts of a neuron.

Chapter 5: Integumentary System

Layers of the Skin

The skin consists of three main layers:

• Epidermis: Outermost, avascular, composed of keratinized stratified squamous epithelium.

• Dermis: Middle, vascular, contains connective tissue, nerves, and blood vessels.

• Hypodermis (Subcutaneous Layer): Deepest, contains adipose tissue.

Layers of the Epidermis (from deep to superficial)

1. Stratum basale

2. Stratum spinosum

3. Stratum granulosum

4. Stratum lucidum (only in thick skin)

5. Stratum corneum

Cells of the Epidermis

• Keratinocytes: Produce keratin for waterproofing and protection.

• Melanocytes: Produce melanin pigment.

• Merkel Cells: Sensory receptors for touch.

• Langerhans Cells: Immune defense.

Dermis Structure

• Papillary Layer: Superficial, contains dermal papillae and capillaries.

• Reticular Layer: Deep, dense irregular connective tissue, provides strength.

Blood Supply of the Dermis

• Cutaneous Plexus: Deep network of arteries and veins.

• Papillary Plexus: Supplies the superficial dermis.

Pigmentation and Skin Disorders

• Melanin: Brown-black pigment, protects against UV.

• Carotene: Yellow-orange pigment.

• Hemoglobin: Red pigment in blood.

• Disorders: Vitiligo (loss of pigment), dermatitis (inflammation), cyanosis (bluish skin).

Effects of UV Light

• Stimulates vitamin D production.

• Excessive exposure can cause DNA damage and skin cancer.

Wound Healing

• Stages: Inflammation, migration, proliferation, maturation.

• Includes clotting, new tissue formation, and remodeling.

Burns

• First-degree: Affects epidermis only (redness, pain).

• Second-degree: Affects epidermis and part of dermis (blisters).

• Third-degree: Destroys entire skin layer (may be painless due to nerve damage).

• Burns are life-threatening due to fluid loss and infection risk.

Chapter 6: Osseous Tissue (Study Guide)

Classification of Bones by Shape

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

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

• Flat Bones: Thin, flat (e.g., sternum).

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

Composition of Osseous Tissue

• Cells: Osteoblasts (form bone), osteocytes (maintain bone), osteoclasts (resorb bone).

• Matrix: Collagen fibers and mineral salts (mainly hydroxyapatite).

Long Bone Anatomy

• Diaphysis: Shaft.

• Epiphyses: Ends.

• Metaphysis: Region between diaphysis and epiphysis.

• Medullary Cavity: Contains bone marrow.

• Periosteum: Outer covering.

Compact Bone Structure

• Osteon (Haversian System): Structural unit.

• Lamellae: Concentric rings of matrix.

• Canaliculi: Small channels for nutrient/waste exchange.

• Central Canal: Contains blood vessels and nerves.

• Perforating (Volkmann's) Canals: Connect central canals.

Bone Formation (Ossification)

• Endochondral Ossification: Bone forms from cartilage model (most bones).

• Intramembranous Ossification: Bone develops from fibrous membrane (e.g., skull bones).

Bone Growth

• Interstitial Growth: Lengthening of bone at epiphyseal plate.

• Appositional Growth: Increase in bone thickness.

Hormonal Regulation of Bone

• Parathyroid Hormone (PTH): Increases blood calcium by stimulating osteoclasts.

• Calcitonin: Lowers blood calcium by inhibiting osteoclasts.

• Calcitriol (Vitamin D): Increases calcium absorption from the gut.

Fracture Repair Stages

1. Hematoma formation

2. Fibrocartilaginous callus formation

3. Bony callus formation

4. Bone remodeling

Bone Markings

Bones have specific markings for attachment and articulation.

Additional info: These study notes are based on a list of exam or homework questions, expanded with academic context for clarity and completeness.