Classification of Epithelial Tissue (a) Layer - Simple - One Layer Stratified - Many Layers Pseudostratified - One layer but it looks like more than one layer because the cells are different shapes and the nuclei are located at different levels (b) Shape - Squamous - flat Cuboidal - cubed/square Columnar - column/rectangular Transitional - changes shape due to amount of pressure exerted on it - contains the ability to stretch and expand as a response to pressure

Characteristics of Epithelial Tissue cells packed together (cellularity) always has a free surface exposed to outside or empty internal space (apical surface) & attached to underlying tissue (basal surface) (polarity) anchored to connective tissue by a thin membrane called the basement membrane (attachment) lacks blood vessels - blood diffuses from connective tissue (avascularity) cells reproduce quickly - as a result, healing occurs rapidly (more quickly than any other tissue) (regeneration) acts as a barrier

Specific Types of Covering & Lining Epithelial Tissue Simple Squamous - Location: blood vessels (capillaries), alveoli (air sacs) of lungs, kidney tubules Function: (very thin tissue) diffusion & filtration Simple/Stratified Cuboidal - Location: glands and ducts, kidneys Function: secretion &/or absorption Simple Columnar - Location: lining of stomach, intestine, & gallbladder Function: protection, secretion, & absorption Pseudostratified Ciliated Columnar - Location: respiratory system (nasal cavity & bronchi) Function: protection & secretion

Covering & Lining Epithelial (cont.) Stratified Squamous - Location - surface of skin, lining of mouth, throat, esophagus, rectum, anus, and vagina Function - provides physical protection against abrasion, pathogens, and chemical attack (protection against wear and tear / friction) Transitional - Location - urinary bladder Function – permits expansion and recoil after stretching

Glandular Epithelium Composed of cells that specialize in production and secretion of specific substances Endocrine - secrete their products within/into tissue and blood (hormones) (ductless glands) Exocrine - secrete their products into ducts opening onto internal or external surfaces (sweat, saliva)

Characteristics of Connective Tissue binds/connects structures provides support & protection insulates fills spaces within body cavities stores fat transports produces blood cells protects against infection helps repair tissue damage cells farther apart & intercellular material (matrix) between cells usually reproduce well & good blood supply so well nourished (healing generally occurs quickly)

Structure of Connective Tissue LIVING PORTION Cells ResidentWandering NONLIVING PORTION Matrix (1)Ground Substance (2)Fibers

Structure of Connective Tissue (cont.) Cells – * Resident – stable numbers, always there, don’t move... Fibroblasts, Mast Cells, Specific Cells * Wandering – move temporarily into tissue from bloodstream, usually as a response to infection/injury... White Blood Cells/Macrophages (perform phagocytosis to clear foreign particles)

Structure of Connective Tissue (cont.) Fibroblasts – most common type of resident cell, large and usually star- shaped, produce fibers by secreting proteins Mast Cells – large & widely distributed, near blood vessels secrete two types of chemicals: heparin – prevents blood clotting & histamine – promotes reactions related to allergies & inflammation

Structure of Connective Tissue (cont.) Specific Cells: chondrocytes – cartilage cells adipocytes – adipose cells osteocytes – bone cells

Structure of Connective Tissue (cont.) Matrix: Ground Substance: Fluid, Semifluid or Gel-like (which is semisolid), Rigid Fibers: * Collagenous - Structure: thick threads of collagen protein grouped in long, parallel bundles (WHITE) Function: provide great strength Location: important components of body structures that hold things together (for example: tendons & ligaments)

Structure of Connective Tissue (cont.) Fibers (cont.): * Elastic – Structure: thin fiber of elastin protein that branches (YELLOW) Function: weaker, but stretch easily & snap back into place Location: vocal cords & elastic cartilage * Reticular – Structure: very thin fiber that is highly branched (BROWN) Function: form delicate supporting networks Location: walls of blood vessels, basement membrane

Types of Connective Tissue Rigid/Supporting CT: Bone Cartilage – Fibrocartilage, Hyaline, Elastic CT Proper: Loose Fibrous CT – Areolar, Adipose, Reticular Dense Fibrous CT – Tendons & Ligaments Fluid CT: Blood Lymph