Cell ConnectionsChapter 4

4 major types of tissuesEpithelial tissue- Covers surface of body,

lines hollow organs and body cavities. Ex: Skin and stomach tissue

Connective tissue- Holds organs in place, protects and supports body. Ex: Tendons and ligaments

Muscular tissue- Generates physical force and movements. Ex: Biceps, quadriceps

Nervous tissue- Helps control and coordinate body movement by detecting changes and responding with nerve impulses. Ex: Brain and spinal cord

To function in a coordinated way as part of a tissue, cells must have cell junctions.

Cell junction- points of contact between neighboring plasma membranes.

Imagine trying to build a house with nothing to hold the lumbar, roof, and walls together.

Plant cellsPlasmodesmata- Channels between adjacent

plant cells. They form a circulatory and communication system connecting the cells in plant tissues.

*Helps water and small molecules pass easily from cell to cell.

Animal cellsAdjacent cells in animal tissues also connect

by cell junctions; there are three types:

Tight junctionsAnchoring junctions

(desmosomes)Gap junctions

Tight junctionsBind cells very tightly togetherForms a leakproof sheetPrevents passage of materialsLines digestive tract, preventing contents from leaking into surrounding tissues.

Anchoring junctionsStrongly link cells together with cytoskeletal

fibersForms strong sheetsCommon in tissues that have to stretch, such

as skin and heart muscle.Helps keep skin cells from separating

Ex: Desmosomes

Gap junctionsChannels similar to plasmodesmata in plant

cellsAllows small molecules to flow between

neighboring cells.Important for chemical communication.