Chapter 4
4 major types of tissues
 Epithelial 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 cells
 Plasmodesmata- 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 cells
 Adjacent cells in animal tissues also connect by cell
junctions; there are three types:
 Tight junctions
 Anchoring junctions
(desmosomes)
 Gap junctions
Tight junctions
 Bind cells very tightly together
 Forms a leakproof sheet
 Prevents passage of materials
 Lines digestive tract, preventing
contents from leaking into surrounding tissues.
Anchoring junctions
 Strongly link cells together with cytoskeletal fibers
 Forms strong sheets
 Common in tissues that have to stretch, such as skin
and heart muscle.
 Helps keep skin cells from separating
 Ex: Desmosomes
Gap junctions
 Channels similar to plasmodesmata in plant cells
 Allows small molecules to flow between neighboring
cells.
 Important for chemical communication.