Psychology 2720A/B Chapter Notes - Chapter 3: Blood Plasma, Integrin, Fibrocartilage

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Published on 18 Apr 2013
School
Western University
Department
Psychology
Course
Psychology 2720A/B
Professor
Chapter 3 Tissues
Tissue group of cells that have a common origin and function to carry out
an activity
Tissues may be hard, semisolid or liquid
Types of Tissues
Four basic types of tissues:
o Epithelial covers body surfaces and lines hollow organs, body
cavities, and ducts; forms glands; allows body to interact with both
the external and internal environments
o Connective tissues protects and supports the body; stores energy
reserves as fat and provides immunity for the body
o Muscular tissue for contraction and generation of force, generates
heat that warms the body
o Nervous tissue detects changes in the body and sends action
potentials
Cell Junctions
Cell junctions contact points between the plasma membranes of tissue cells
5 types of junctions (pg. 64 Figure 3.2)
o Tight junctions
Transmembrane proteins fuse together the outer surfaces of
adjacent plasma membranes
Create fluid-tight seals
o Adherens junctions
Plaque (dense layer of protein) attaches to membrane proteins
and to microfilaments of the cytoskeleton
Cadherins insert into the plaque from the opposite side of the
plasma membrane, partially crosses the intercellular space and
connects to a cadherin of an adjacent cell
Anchor cells to one another
o Desmosomes
Contain plaque, have transmembrane glycoproteins that
extend into the intercellular space between adjacent cell
membranes and attach cells to one another
Plaque doesn’t attach to microfilaments, it attaches to elements
of the cytoskeleton called intermediate filaments
Intermediate filaments extend from desmosomes on one side
of the cell across the cytosol to desmosomes on the opposite
side of the cell
Structural arrangement helps the stability of the cell
Prevent epidermal cells from separating under tension and
cardiac muscles from pulling apart during contraction
Anchor cells to one another
o Hemidesmosomes
Don’t link adjacent cells
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Transmembrane glycoproteins are integrins (rather than
cadherins)
Integrins attachs to intermediate filaments on the inside of the
plasma membrane
On the outside of the plasma membrane, integrins attach to
protein laminin (in the basement membrane)
Hemidesmosomes anchor cells to the basement membrane, not
to each other
o Gap junctions
Membrane protein connexins form fluid-filled tunnels that
connect neighbouring cells
Plasma membranes are separated by a narrow intercellular
space
Small molecules can diffuse through the passage, but the
movement of larger molecules is prevented
Transfer of nutrients and wastes occur in gap junctions
Allow nerve or muscle impulses to spread among tissues
Epithelial Tissue
Consists mostly of cells with little extracellular material between adjacent
plasma membranes
Has three major functions:
o Serve as selective barriers to limit or aid the transfer of substances
into and out of the body
o Release products produced by the cells onto their free surfaces
o Protect against the abrasive influences of the environment
The apical, lateral, and basal surfaces of epithelial cells are modified in
various ways to carry out specific functions
Epithelium is arranged in sheets and attached to the basement membrane
Basement membrane has two layers, the basal lamina and the reticular
lamina
Avascular (no direct blood supply), but has nerve supply
Epithelia have high capacity for renewal
Layers of cells can be simple (one layer, secretion and absorption),
pseudostratified (appears to have several layers but actually only has one),
or stratified (several layers)
The cells can have different shapes: squamous (flat while bumps; rigid),
cuboidal (square, secretion and absorption), columnar (tall rectangles,
secretion or absorption), or transitional (variable)
There are two subtypes of epithelia: lining (covering) and glandular
(secreting portion of glands)
Simple squamous epithelium = single layer of cells and flat shape
o Found in parts of the body where filtration or diffusion are priority
processes
o Endothelium lines the heart and blood vessels
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Document Summary

Tissue group of cells that have a common origin and function to carry out an activity. Tissues may be hard, semisolid or liquid. Cell junctions contact points between the plasma membranes of tissue cells. Transmembrane proteins fuse together the outer surfaces of adjacent plasma membranes. Plaque (dense layer of protein) attaches to membrane proteins and to microfilaments of the cytoskeleton. Cadherins insert into the plaque from the opposite side of the plasma membrane, partially crosses the intercellular space and connects to a cadherin of an adjacent cell. Anchor cells to one another: desmosomes. Contain plaque, have transmembrane glycoproteins that extend into the intercellular space between adjacent cell membranes and attach cells to one another. Plaque doesn"t attach to microfilaments, it attaches to elements of the cytoskeleton called intermediate filaments. Intermediate filaments extend from desmosomes on one side of the cell across the cytosol to desmosomes on the opposite side of the cell. Structural arrangement helps the stability of the cell.

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