Tissues Cells work together in functionally

related groups called tissues How is this done?

Attachments Communication

Types of tissues:1. Epithelial – lining and covering2. Connective – support 3. Muscle – movement4. Nervous – control

Epithelial Tissue – General Characteristics & FunctionsCovers a body surface or lines a body cavity

& forms most glandsFunctions of epithelium:

Protection- skinAbsorption, secretion, and ion transport-

pancreatic cellsFiltration- stomach, intestineForms slippery surfaces- lungs

Special Characteristics of EpitheliaCellularity

Mostly cells that are in close contact (tightly packed)… thus they form effective barriers

Specialized contactsSpecialized cell contacts bind adjacent cells

together (helps w/ communication)

Location- body surfaces, lining of hollow organs, forms glandsOutside surface of the bodyLining of digestive, respiratory and urogenital

systemsHeart and blood vesselsLinings of many body cavities

Special Characteristics of Epithelia

SurfacesBasal,

apical and lateral

Supported by connective tissue At the basal

surface, epithelial tissue and connective tissue form the basement membrane

Special Characteristics of EpitheliaAvascular

No blood vessels; nutrients must diffuse

Regenerative epithelial

tissues have a high capacity for regeneration (mitosis!)

Recap.Identify two special characteristics

about epithelial tissue?

Identify two places epithelial tissue can be found.

Bell WorkWhat surface of an epithelial cell

opens up to the outside of the opening of an internal space?

What surface connects to the side of another cell?

Basal SurfaceWhat is it? Where is it?

Non-cellular, non-living supporting sheet two layers (basal lamina & reticular lamina)

Composed of: proteins secreted by the epithelial cells

Function:Selective filter selectively permeable to

molecules from capillaries Point of attachment and support for overlying

epithelial tissues (regenerating cells migrate from this point)

Apical SurfaceWhat is it? Where is it?

Surface that is exposed to the outside or internally to an open space

Located above the Basal LaminaComposed of:

Microvilli – finger-like extensions of plasma membrane Found in the small intestine and kidney Maximize SA across which small molecules enter or leave

Cilia – whip-like, highly motile extensions Found in the lungs Movement is coordinated waves

Lateral Surface FeaturesWhat is it?

sides of epithelial cells that face adjacent cells on either side

Factors holding epithelial cells together:Adhesion proteins link plasma membranes of

adjacent cellsSpecial cell junctions

Tight JunctionsAdherens JunctionsDesmosomesGap Junctions

Tight JunctionsTight junctions– closes off intercellular

space Location: near apical regionPurpose: forms an impermeable junction;

prevents molecules from passing between cells

Formation: transmembrane proteins in the plasma membrane of adjacent cells fuse together

Ie.: epithelial tissue lining the stomach, intestines & urinary bladder prevent contents of these organs from leaking

Adherens JunctionAdherens junctions – anchoring junction

Location- apical lateral bordersPurpose: helps form the tight junction around

apical lateral bordersFormation:

A dense layer of proteins on inside of plasma membrane (plaque) attaches to the cytoskeleton.

Transmembrane linker proteins (cadherins) are anchored into the cell’s plaque and they bind to cadherins of another cell thus joining the two cells.

Ie.: help epithelial surfaces resist separation during contractile activities (food moving through the intestine)

DesmosomesDesmosomes – 2 disc-like plaques

connected across intercellular spaceLocation: found in superficial layers of skinPurpose: reduces tearing, twisting, stretchingFormation:

Plaques of adjoining cells are joined by proteins called cadherins

Desomosomes on one side of the cell are imbedded with intermediate filaments (keratin protein) that extends across the cytosol of a cell to desmosomes on the other side of the same cell

Gap JunctionsGap junctions – passageway between two

adjacent cellsLocation: Present in electrically excitable

tissues (heart, smooth muscle)Purpose: Let small molecules move directly

between neighboring cellsFormation: Cells are connected by a protein

called connexins that form hollow cylinders called connexons

Ie.: lens and the cornea of the eye; enable nerve or muscle impulses to spread rapidly among cells

Bell WorkWhat type of junction is a passage way

between two cells?

What type of junction resists contractile activity?

Create a flip book on the following:Draw & label the surfaces of an epithelial

cell (Basal, apical and lateral)Draw & label each of the following

(include the cell junction’s purpose, where it is found and an analogy to remember it)Tight junction Adherens junction DesmosomeGap junction

Bingo!tissue

EpithelialConnective

Musclenerveapicalbasal

lateral surfacetight junction

adherens junction

desmosomegap junctionConnexonsConnexinsCadherins

plaque microvilli

cilia avascular

impermeaberegenerativeintermediate

filamentlinker proteins