Group of cells & their intercellular substances 

with common or related functions

Primary Tissue Types

Epithelial

Primary Tissue Types

Muscle

Primary Tissue Types

Connective

Primary Tissue Types

Nervous

-Covers body surfaces

-Sheet of closely adhering cells 

Mucosa

Serosa

Special Characteristics of Epithelium

High Cellularity

-Almost entirely cells

-Forming Sheets

-Little Extracellular Matrix

Epithelial Cell Structural Polarity

Apical

-Not attached

-Exposed to exterior or inner cavities

-Microvilli e.g. small intestine

-Cilia e.g. in trachea

Epithelial Cell Structural Polarity

Lateral

-Attached to other epithelial cells

-Specialized contacts to restrict permeability

& form layers

Epithelial Cell Structural Polarity

Basal

-Attached to basement membrane

-Provide reinforcement & stability

-Specialized type of extracellular material

-Secreted by epithelial cells & connective tissue

-Nourishment through basement membrane

-Many Layers

-Most active & viable cells are close to basement membrane

-Dead cells are farther away from basement membrane

E.g. Epidermis of the skin

-A lot of nerve endings

-Very sensitive

-High level

-Constant renovation

-Quick repairing without a scar

Classification of Epithelium

2 Names

-First: number of cell layers

-Second: shape of cells

Regular Epithelia by layers

Simple

-One layer

-One level of nuclei location

Regular Epithelia by layers

Pseudostratified

-One layer

-Many levels of nuclei location

Regular Epithelia by layers

Stratified

Regular Epithelia by Cell Shape

Squamous

Regular Epithelia by Cell Shape

Cuboidal

Regular Epithelia by Cell Shape

Columnar

-One layer

-Very thin

-Not protective, but very permeable

Functions: Absorption, secretion, filtration

-Very permeable

Cells: Flat

Location: Lungs alveoli, kidney glomeruli, cardiovascular system Endothelium, serous membranes Mesothelium

-Mid permeability

Cells: Cube-like

Location: Kidney tubules

-Not permeable

Cells: Tall; may have cilia; Globlet cells

Location: nonciliated-GIT; ciliated-bronchial; microvilli-small intestine

All cells on basement membrane, but not all reach surface

Cells: columnar

Location: Ciliated-trachea 

-More than one layer

-Regeneration from below

-More durable

Major Function: Protection

Stratified Squamous 

Structure

1: Free surface cells are squamous, may be dead & may contain keratin (protective protein)

2: Deeper layers are cuboidal or columnar & active in mitosis

Stratified Squamous

Location

Nonkeratinized: esophagus, mouth, vagina, anus

Keratinized: skin 

Transitional

Structure

Change shape & position during stretching

(dome to squamous)/(10 layers to 3 layers)

E.g. Bladder

Transitional

Location

Ureters

Bladder

Upper part of urethra

-Cluster of cells (or single cell)

-Produces a substance--secretion

-Secretion is to be excreted from or used in the body

-Internally secreting

-Release product into the extracellular space or into the blood

-Ductless

Product: Hormones

-Externally secreting

-Release product to the epithelial surface inside or outside the body

-Have ducts

-One cell

E.g. Goblet cells

-Secretion: mucin (glycoprotein, after dissolving in H20 forms mucus)

Many cells, forming two parts

1: Epithelial--derived duct

2: Secretory Unit

Way (or mode) of secretion releasing

Merocrine

-Cells don't alter

-Pancreas, salivary

Way (or mode) of secretion releasing

Apocrine

-Cells are partly breaking down, then repaired

-Mammary, some sweat glands

Way (or mode) of secretion releasing

Holocrine

-Accumulate secretion until rupture

-Cells are dying, then replaced

-Sebaceous (oily)

E.g. Acne