Chapter 3: Tissues

Epithelial Tissue

Epithelial tissue forms the covering and lining of body surfaces and cavities, providing protection, absorption, and secretion.

• Apical & Basal Surfaces: The apical surface faces the body exterior or cavity lumen, while the basal surface attaches to underlying connective tissue.

• Functions: Protection, absorption, filtration, excretion, secretion, and sensory reception.

• Example: The skin's outer layer (epidermis) is composed of epithelial cells.

Exocrine Glands

Exocrine glands secrete their products onto body surfaces or into body cavities.

• Types: Paracrine (local signaling), Endocrine (hormone secretion into blood).

• Examples: Sweat glands, sebaceous (oil) glands.

Connective Tissue

Connective tissue supports, binds, and protects other tissues and organs.

• Components: Ground substance, cells, and fibers.

• Fibers: Collagen (strength), Elastin (elasticity), Reticulin (support).

• Cells: Fibroblasts, adipocytes, immune cells.

• Example: Tendons and ligaments are rich in collagen fibers.

Cartilage

Cartilage is a flexible connective tissue found in joints, ear, nose, and respiratory tract.

• Types: Hyaline, elastic, and fibrocartilage.

• Function: Provides support and cushioning.

Muscle Tissue

Muscle tissue is responsible for movement and force generation.

• Types: Skeletal, cardiac, and smooth muscle.

• Example: Skeletal muscles move bones; cardiac muscle forms the heart.

Nervous Tissue

Nervous tissue transmits electrical impulses for communication and control.

• Cells: Neurons and neuroglia.

• Function: Sensory input, integration, motor output.

Tissue Repair

Tissue repair restores structure and function after injury.

• Inflammation: Initial response to injury; brings immune cells to the site.

• Regeneration: Replacement of damaged cells with the same type.

• Fibrosis: Replacement with scar tissue (collagen).

Stem Cells

Stem cells are undifferentiated cells capable of giving rise to specialized cell types.

• Function: Essential for growth, repair, and regeneration.

• Example: Skin stem cells regenerate the epidermis.

Chapter 4: The Integumentary System

Overview

The integumentary system includes the skin, hair, nails, and associated glands, serving as the body's protective barrier.

Layers of the Skin

The skin consists of three main layers: epidermis, dermis, and hypodermis (subcutaneous layer).

• Epidermis: Outermost layer; composed of stratified squamous epithelium.

• Dermis: Middle layer; contains connective tissue, blood vessels, nerves.

• Hypodermis (Subcutaneous Layer): Deepest layer; consists of adipose tissue for insulation and cushioning.

Layers of the Epidermis

The epidermis is organized into several layers, each with distinct functions.

• Stratum Basale: Deepest layer; contains mitotic cells (stem cells) where new epidermal cells are produced.

• Stratum Spinosum, Granulosum, Lucidum, Corneum: Progressively more superficial layers; cells mature and fill with keratin.

• Keratinocytes: Main cell type; produce keratin for waterproofing and protection.

• Melanocytes: Produce melanin pigment for skin color and UV protection.

Sensory Structures

The skin contains specialized structures for sensation.

• Tactile Discs: Detect light touch.

• Free Nerve Endings: Sense pain and temperature.

Layers of the Dermis

The dermis provides structural support and houses blood vessels, nerves, and glands.

• Papillary Layer: Superficial; contains capillaries and sensory receptors.

• Reticular Layer: Deep; dense irregular connective tissue with collagen and elastin fibers.

• Function: Supplies nutrients and oxygen to the epidermis; contains touch receptors.

Hypodermis (Subcutaneous Layer)

The hypodermis anchors skin to underlying tissues and stores fat.

• Function: Insulation, energy storage, shock absorption.

Hair

Hair is a filamentous structure composed of keratinized cells.

• Arrector Pili Muscle: Smooth muscle that causes hair to stand up (goosebumps).

Glands of the Skin

The skin contains several types of glands with distinct functions.

• Sebaceous Glands: Produce oil (sebum) to lubricate and waterproof skin and hair.

• Apocrine Sweat Glands: Found in axillary and genital areas; secrete a thicker, milky sweat.

• Merocrine (Eccrine) Sweat Glands: Widely distributed; produce watery sweat for thermoregulation.

Skin Changes with Age

Skin undergoes structural and functional changes as it ages.

• Thinning of epidermis and dermis

• Decreased collagen and elastin

• Reduced gland activity

The Rule of Nines

The rule of nines is a method for estimating the percentage of body surface area affected by burns.

• 1st Degree: Affects only the epidermis; causes redness (sunburn).

• 2nd Degree: Involves epidermis and part of dermis; causes blisters.

• 3rd Degree: Destroys epidermis and dermis; may damage nerves, resulting in numbness.

Additional info: The rule of nines divides the body into regions that represent 9% (or multiples) of total body surface area, aiding in clinical assessment of burn severity.