Epithelial Tissue Types

• Tissues are groups of similar cells performing specific functions
• Histology is the study of tissues
• The four basic tissue types are epithelial, connective, muscle, and nervous tissue

Epithelial Tissue

• Covers body surfaces, lines body cavities and forms glands
• Functions include protection, absorption, filtration, excretion, secretion, and sensory reception
• Classified by cell shape and number of layers

Epithelial Tissue: Cell Shape

• Squamous: flattened and scale-like
• Cuboidal: cube-shaped
• Columnar: column-shaped
• Transitional: varying shapes that can distend

Epithelial Tissue: Number of Layers

• Simple: single layer of cells
• Stratified: multiple layers of cells
• Pseudostratified: single layer but appears stratified

Specific Epithelial Tissues

• Simple squamous epithelium: single layer of flattened cells; allows for diffusion and filtration; found in air sacs of lungs and lining blood vessels
• Simple cuboidal epithelium: single layer of cube-shaped cells; involved in secretion and absorption; found in kidney tubules and glands
• Simple columnar epithelium: single layer of column-shaped cells; involved in absorption and secretion; found lining the digestive tract
• Pseudostratified columnar epithelium: single layer of cells of varying heights; involved in secretion and propulsion of mucus; found lining the trachea
• Stratified squamous epithelium: multiple layers of flattened cells; protects underlying tissues in areas subject to abrasion; found in the epidermis of the skin
• Transitional epithelium: multiple layers of cells that can change shape; allows for distension; found lining the urinary bladder

Glandular Epithelium

• Glands are composed of epithelial cells specialized to produce and secrete substances
• Endocrine glands secrete hormones directly into the bloodstream
• Exocrine glands secrete substances onto body surfaces or into ducts

Connective Tissue

• Provides support, binding, and protection for other tissues and organs
• Characterized by an extracellular matrix composed of ground substance and fibers
• Major types include connective tissue proper, cartilage, bone, and blood

Connective Tissue Proper

• Loose connective tissue: fibers are loosely arranged
  • Areolar connective tissue: wraps and cushions organs; found under epithelia
  • Adipose connective tissue: stores fat; provides insulation and support; found under skin and around organs
  • Reticular connective tissue: forms a soft internal skeleton (stroma) that supports other cell types; found in lymphoid organs
• Dense connective tissue: fibers are densely packed
  • Dense regular connective tissue: primarily parallel collagen fibers; provides great tensile strength; found in tendons and ligaments
  • Dense irregular connective tissue: irregularly arranged collagen fibers; provides strength and support; found in the dermis of the skin

Cartilage

• Provides support and flexibility
• Composed of chondrocytes located in lacunae
• Types include hyaline cartilage, elastic cartilage, and fibrocartilage
• Hyaline cartilage: supports and reinforces; found covering the ends of long bones
• Elastic cartilage: maintains shape while allowing flexibility; found in the external ear
• Fibrocartilage: tensile strength allows it to absorb compressive shock; found in intervertebral discs

Bone Tissue

• Provides support, protection, and leverage for movement
• Composed of osteocytes located in lacunae
• Compact bone: dense outer layer of bone
• Spongy bone: inner layer of bone with trabeculae

Blood

• Transports materials throughout the body
• Composed of red blood cells, white blood cells, and platelets
• Plasma is the fluid matrix

Muscle Tissue

• Specialized for contraction and movement
• Three types include skeletal, cardiac, and smooth muscle

Skeletal Muscle

• Attached to bones
• Responsible for voluntary movement
• Cells are long, cylindrical, and striated
• Multinucleated

Cardiac Muscle

• Found in the walls of the heart
• Responsible for involuntary contraction
• Cells are branched and striated
• Single nucleus
• Intercalated discs for coordinated contraction

Smooth Muscle

• Found in the walls of hollow organs
• Responsible for involuntary movement
• Cells are spindle-shaped and non-striated
• Single nucleus

Nervous Tissue

• Specialized for conducting electrical impulses
• Found in the brain, spinal cord, and nerves
• Two main cell types include neurons and neuroglia

Neurons

• Generate and conduct electrical signals
• Composed of a cell body, dendrites, and an axon

Neuroglia

• Support, insulate, and protect neurons
• Types include astrocytes, microglia, oligodendrocytes, and Schwann cells

Learn about epithelial tissue, one of the four basic tissue types. Epithelial tissue covers body surfaces, lines body cavities, and forms glands. It is classified by cell shape (squamous, cuboidal, columnar, transitional) and number of layers (simple, stratified, pseudostratified).