•Tissue

•Histology

•The Four Primary Tissue TypesEpithelialConnectiveMuscularNervous

Epithelial Tissue

Epithelium / -a = cell layer (barrier)– Covering or lining—inside and out– Permeability control– Sensation– Glands = secretory structure

BM

apical

basal

Structural Characteristics of Epithelia

Cellularity

Polarity

Avascular

Innervated

Regenerative ability

Polarity of Epithelial Cells

Classification of EpitheliaThe function of the epithelium determines

which type.

Typically classified according to

1. Number of cell layersSimple vs. Stratified

2. Shape of cellSquamous, cuboidal, columnar

Special features Cilia, villi, goblet cells

End with epithelium to complete the naming

Arrangements

• Simple• Stratified• Pseudostratified• Transitional

Shapes

• Squamous

• Cuboidal

• Columnar

Special Features

• Cilia• Goblet Cells• Microvilli• Villi

Simple Squamous Epithelium

1 cell thick

Friction reduction

Diffusion/filtration

Locations:

•Lining of ventral body cavities, e.g. peritoneum•Lining of blood vessels (endothelium)

•Alveoli

Simple Cuboidal Epithelium

• Function:

Secretion

Absorption• Location:

Lining of ducts

Glands (salivary, pancreas, thyroid)

Kidney tubules

Thyroid Follicle

Simple Columnar Epithelium

• FunctionsSecretionAbsorption

• LocationsGI tractExcretory ductsReproductive tract

• Special Features

Pseudostratified Ciliated Columnar Epithelium

Function:Mucociliary Blanket

Mixture of cell heights nuclei located at various distances from surface.

LocationsRespiratory tract except for lungs Male reproductive ducts

Stratified Squamous Epithelium

• Multiple layers = better protection

• Keratinized vs. non-keratinized

• Location? Where we need protection!Skin surfaceEntrances/exits of body

Stratified cuboidal and columnar: rare, found in glands and ducts

Transitional Epithelium

• Function

Extreme expansion & recoil

• Layered appearance due to overcrowding.

• Location

Bladder, ureters

stretched

Location in the Body

Connective Tissue: Supports, protects, binds tissues

Structural characteristics:

• Specialized cells

• Extracellular matrix– Protein fibers – Ground substance

• Mostly highly vascular

Functions

• Structural framework

• Transport

• Support and protection

• Energy storage

Classification of Connective Tissue

Connective Tissue ProperTypes:

Areolar Dense regular ReticularAdipose Dense irregular

Types of Fibers:

CollagenElasticReticular

Defense:

MacrophagesPlasma CellsMast CellsOther WBC

Membranes = Combination of Epithelia & C.T.

• Mucous membranes– Lining of cavities that communicate with exterior

• Serous membranes– Lining of sealed, internal cavities

• Cutaneous membranes– Skin

• Need to know membranes

• Parietal vs. visceral