Chapter 4: Tissues Study Guide – Anatomy & Physiology

Epithelium

Primary Tissue Types

In human anatomy, tissues are groups of cells with similar structure and function. There are four primary tissue types in the body:

• Epithelial tissue

• Connective tissue

• Muscle tissue

• Nervous tissue

Additional info: These tissue types form the basic structural and functional units of organs.

Characteristics of Epithelium

• Cellularity: Composed almost entirely of cells with minimal extracellular material.

• Polarity: Has an apical (top) surface and a basal (bottom) surface.

• Attachment: The basal surface is attached to a basement membrane.

• Avascularity: Lacks blood vessels; nutrients diffuse from underlying tissues.

• Regeneration: High capacity for cell division and renewal.

Functions of Epithelial Tissue

• Protection: Shields underlying tissues from mechanical and chemical injury.

• Absorption: Takes in substances, such as nutrients in the intestines.

• Secretion: Produces and releases substances like enzymes and hormones.

• Excretion: Removes waste products.

• Sensation: Contains sensory nerve endings.

Example: The epithelium lining the stomach secretes digestive enzymes and mucus.

Types of Epithelium: Shape and Arrangement

• Squamous: Flat, scale-like cells; found where diffusion or filtration occurs (e.g., alveoli of lungs).

• Cuboidal: Cube-shaped cells; found in glands and kidney tubules.

• Columnar: Tall, column-shaped cells; found in the digestive tract lining.

Arrangement:

• Simple epithelium: Single layer of cells; functions in absorption, secretion, and filtration.

• Stratified epithelium: Multiple layers; provides protection against abrasion.

Example: Simple squamous epithelium lines blood vessels for efficient exchange.

Surface Features of Epithelium

• Microvilli: Increase surface area for absorption (e.g., small intestine).

• Cilia: Move substances across the cell surface (e.g., respiratory tract).

Example: Ciliated epithelium in the trachea moves mucus upward.

Types of Glands

• Exocrine glands: Secrete products into ducts (e.g., sweat glands).

• Endocrine glands: Release hormones directly into the bloodstream (e.g., thyroid gland).

Example: Salivary glands are exocrine; the pancreas has both exocrine and endocrine functions.

Connective Tissue

Major Characteristic

Connective tissue is distinguished by its abundant extracellular matrix, which separates the cells and provides structural support.

Major Functions

• Support: Forms structural framework (e.g., bone, cartilage).

• Protection: Cushions and insulates organs (e.g., adipose tissue).

• Transport: Blood transports nutrients, gases, and wastes.

• Storage: Stores energy (e.g., fat in adipose tissue).

• Defense: Immune cells in connective tissue fight pathogens.

Example: Bone tissue supports the body and protects vital organs.

Types of Connective Tissue

• Loose connective tissue: Areolar, adipose, reticular.

• Dense connective tissue: Dense regular, dense irregular, elastic.

• Cartilage: Hyaline, elastic, fibrocartilage.

• Bone: Compact and spongy bone.

• Blood: Fluid connective tissue.

Example: Adipose tissue stores energy and insulates the body.

Muscle Tissue

Unique Features and Types

Muscle tissue is specialized for contraction, enabling movement of body parts and substances.

• Skeletal muscle: Voluntary, striated, attached to bones; responsible for body movement.

• Cardiac muscle: Involuntary, striated, found in the heart; pumps blood.

• Smooth muscle: Involuntary, non-striated, found in walls of hollow organs; moves substances.

Structure and Function:

• Skeletal muscle cells: Long, cylindrical, multinucleated; contract to move skeleton.

• Cardiac muscle cells: Branched, interconnected, single nucleus; contract rhythmically.

• Smooth muscle cells: Spindle-shaped, single nucleus; contract to move food, urine, etc.

Example: Cardiac muscle contracts to pump blood throughout the body.

Nervous Tissue

Structure and Function

Nervous tissue is specialized for communication via electrical and chemical signals.

• Neurons: Conduct impulses; consist of cell body, dendrites, and axon.

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

Example: Neurons transmit signals from the brain to muscles for movement.

Types of Membranes

Classification and Functions

Body membranes cover surfaces, line cavities, and form protective sheets around organs. They are classified by location and function.

Membrane Type	Location	Function
Mucous	Lines cavities open to exterior (e.g., digestive, respiratory tracts)	Secretion and protection
Serous	Lines closed cavities (e.g., thoracic, abdominal)	Reduces friction via serous fluid
Synovial	Lines joint cavities	Produces synovial fluid for lubrication
Cutaneous	Skin (external body surface)	Protection

Inflammatory Response

When tissues are injured, the body initiates an inflammatory response to protect and repair.

• Redness (rubor): Increased blood flow.

• Heat (calor): Increased metabolic activity.

• Swelling (tumor): Accumulation of fluid.

• Pain (dolor): Stimulation of nerve endings.

Example: A cut on the skin triggers redness, swelling, heat, and pain as part of the healing process.

Additional info: Chronic inflammation can lead to tissue damage and disease.