Histology and the Integumentary System: Study Guide (Chapters 4-5)

Histology

Categories and Functions of Tissues

Histology is the study of tissues, which are groups of cells with similar structure and function. There are four main categories of tissues in the human body:

• 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. Includes skeletal, cardiac, and smooth muscle.

• Nervous tissue: Conducts electrical impulses and processes information. Composed of neurons and neuroglia.

Epithelial Tissue

• Shape and Layers: Epithelial tissue is classified by cell shape (squamous, cuboidal, columnar) and number of layers (simple, stratified).

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

• Specialized Cells: Some epithelial cells form glands (exocrine and endocrine) and have specialized functions such as cilia for movement or microvilli for absorption.

• Basement Membrane: A thin, fibrous layer that anchors epithelial tissue to underlying connective tissue.

Connective Tissue

• Main Categories: Connective tissue proper, cartilage, bone, and blood.

• Matrix: Consists of extracellular protein fibers (collagen, elastic, reticular) and ground substance (fluid, gel, or solid).

• Cells: Fibroblasts (produce fibers), adipocytes (store fat), chondrocytes (cartilage), osteocytes (bone).

• Dense Connective Tissue: Includes ligaments, tendons, and dermis; provides strength and flexibility.

• Loose Connective Tissue: Includes areolar, adipose, and reticular tissues; provides support and stores energy.

Cartilage and Bone

• Types of Cartilage: Hyaline (flexible support), elastic (resilient and flexible), fibrocartilage (tough, shock-absorbing).

• Bone Tissue: Provides structural support, protects organs, and stores minerals.

Nervous Tissue

• Neurons: Transmit electrical signals.

• Neuroglia: Support and protect neurons.

The Integumentary System

Overview and Functions

The integumentary system consists of the skin, hair, nails, and associated glands. It serves as the body's first line of defense against environmental hazards.

• Protection: Prevents entry of pathogens and minimizes water loss.

• Sensation: Contains sensory receptors for touch, pain, and temperature.

• Thermoregulation: Regulates body temperature through sweat and blood flow.

• Excretion: Removes waste products via sweat.

Skin Structure

• Epidermis: Outermost layer, composed of stratified squamous epithelium. Contains keratinocytes, melanocytes, and other specialized cells.

• Dermis: Middle layer, contains connective tissue, blood vessels, nerves, hair follicles, and glands.

• Hypodermis (Subcutaneous Layer): Deepest layer, composed mainly of adipose tissue for insulation and energy storage.

Accessory Structures

• Hair: Provides protection and sensory input.

• Nails: Protects fingertips and aids in manipulation.

• Glands: Includes sweat glands (eccrine and apocrine), sebaceous glands (produce sebum), and mammary glands.

Glands of the Skin

• Sudoriferous (Sweat) Glands: Eccrine glands are widely distributed and help with thermoregulation; apocrine glands are found in specific areas and become active at puberty.

• Sebaceous Glands: Secrete sebum to lubricate skin and hair.

• Mammary Glands: Specialized for milk production.

Color and Pigmentation

• Melanin: Pigment produced by melanocytes; determines skin color and provides UV protection.

• Carotene: Yellow-orange pigment from diet; accumulates in the skin.

• Hemoglobin: Red pigment in blood; affects skin color based on blood flow.

Classification of Burns

Burns are classified by depth and tissue involvement:

Degree	Depth	Tissue Involved
1st Degree	Superficial	Epidermis only
2nd Degree	Partial thickness	Epidermis and part of dermis
3rd Degree	Full thickness	All layers of skin, may affect underlying tissues

Effects of Aging on the Integumentary System

• Thinning of the epidermis and dermis

• Decreased collagen and elastin production

• Reduced activity of sweat and sebaceous glands

• Slower wound healing

Common Diseases and Disorders

• Albinism: Genetic condition resulting in lack of melanin production.

• Cancers: Includes basal cell carcinoma, squamous cell carcinoma, and malignant melanoma.

• Hair Loss (Alopecia): Can be genetic or due to disease.

• Dermatitis: Inflammation of the skin.

• Acne: Inflammation of sebaceous glands, often during adolescence.

Additional info:

• Histology is foundational for understanding tissue pathology and disease processes.

• Integumentary system disorders can be diagnosed by changes in skin appearance, texture, and function.