EPITHELIAL TISSUE

2 Types: Membranous (covering or lining) Glandular

Functions: Protection Sensory functions Secretion Absorption Excretion

HISTOLOGY

Epithelial Tissue

EPITHELIAL TISSUE (cont)

CharacteristicsLittle matrixPresent 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 shapeColumnar - More tall than wide; Nuclei tend

all be in the same placePseudostratified 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 cellsStratified – more than one layer of

cells of the same shapeTransitional – 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 body1. Exocrine – use ducts to distribute products2. 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 glands2. Holocrine

Secretory product collects in cell & eventually causes it to rupture; cell destroyed

Ex – sebaceous glands3. Merocrine

Majority are this Secretory product leaves cell through cell membrane;

cell not damaged Ex - salivary glands

Quiz time!!!!

Epithelium Practical Practice