EPITHELIAL TISSUE 2 Types: Membranous (covering or lining) Glandular Functions: Protection Sensory functions Secretion Absorption Excretion

HISTOLOGY Epithelial Tissue

EPITHELIAL TISSUE (cont) Characteristics Little matrix Present in surface layers (free surface) Basement membrane - “glue” layer that holds epithelial tissue to connective tissue below it Avascular; gets nutrients via diffusion through basement membrane

CLASSIFICATION Cell Type: Squamous - Flat; scalelike (view from top; looks like an egg) Cuboidal - Square shape Columnar - More tall than wide; Nuclei tend all be in the same place Pseudostratified columnar - Columnar cells are odd shapes; all touch BM; Some nuclei at top and some at bottom

CLASSIFICATION (cont) Cell Layers: Simple – one layer of cells Stratified – more than one layer of cells of the same shape Transitional – more than one layer of varying shapes

Simple Squamous Function: diffusion & filtration Location: alveoli, lining blood & lymph vessels (endothelium), pleura, pericardium, and peritoneum (mesothelium)

Simple Cuboidal Function: secretion, excretion, & absorption Location: glands and their ducts & ducts and tubules of organs such as the kidney

Simple Columnar Function: protection, secretion & absorption Location: lining most of the digestive tract Structure: goblet cells, cilia, and microvilli can be present

Pseudostratified Columnar Function: protection (trap and move "pollutants" to the mouth where they are swallowed) Location: respiratory tract and part of male repro Structure: Cilia & goblet cells present

Stratified squamous Function: protection 2 types: Keratinized Dry No nuclei in top layer Location: skin Nonkeratinized Moist Nuclei in top layer Location: lining of vagina, mouth, esophagus, & anus

Keratinized vs. Nonkeratinized

Keratinized or Nonkeratinized?

Stratified Cuboidal Function: protection Location: pharynx, ducts of sweat glands, & epiglottis

Stratified Columnar Top layer (superficial) is the only one that appears columnar in shape Function: protection Location: male urethra & mucous layer near anus

Stratified Transitional Cell shape varies Function: allows for stretching Location: urinary bladder

Glandular Epithelium Function – secretion (requires energy; therefore a form of active transport) Structure Unicellular gland – cell working alone Multicellular gland – cells working in cluster, cords, or follicles Location – make up the 2 types of glands present in the body 1. Exocrine – use ducts to distribute products 2. Endocrine – do NOT use ducts to distribute products; instead release products directly into bloodstream or interstitial fluid

Classification of Exocrine Glands Two Methods: 1. Structural Based on duct shape & # of ducts Shapes 1.Tubular 2.Alveolar # of ducts 1.Simple 2.Compound

Classification cont’d. 2. Functional Based on discharge method 3 types: 1.Apocrine  Secretory product collects at tip of cell causing distention; eventually distended end pinches off; some damage to cell  Ex – mammary glands 2.Holocrine  Secretory product collects in cell & eventually causes it to rupture; cell destroyed  Ex – sebaceous glands 3.Merocrine  Majority are this  Secretory product leaves cell through cell membrane; cell not damaged  Ex - salivary glands

Quiz time!!!! Epithelium Practical Practice