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Epithelial and Connective Tissues
• Classes of Tissues
– Two classes—epithelial, connective
– Muscle and Nervous Tissue (don’t fit in classes)
• Epithelial tissues
– General characteristics
– Cell shapes
• Connective Tissues
– General characteristics (areolar)
– Types of connective tissues
Human Anatomy, Larry M. Frolich, Ph.D.
General Types of Tissues
Tissue: a group of closely associated cells
that have a similar structure and perform a
related function
•Broad Classes of Tissues
-Epithelial: sheet of cells.
-Connective: cells in a matrix
•More specific tissue types
-do not fit as epithelial or connective
-will treat in section two of course
-Nervous: carries messages in body
-Muscle: effects movement
•Virtually all organs will have all four types
Human Anatomy, Larry M. Frolich, Ph.D.
• Cells connect, on their lateral surfaces, forming
sheets
– Gap junctions
– Tight junctions
– desmosomes
Epithelial Tissues
• Cells can have appendages, on their apical
surface, to interact with environment
– Cilia
– Microvili
– Flagella
• Cells sit, on their basal surface, on a thin basal
membrane of collagen fibers for support
– Underlying connective tissue further supports
epithelium
– Blood vessels/nerves travel in underlying connective
tissue, nerve endings on epithelium
Examples of epithelium: epidermis, lining of gut, mucous membranes,
lining of celom, glands
Human Anatomy, Larry M. Frolich, Ph.D.
Appendages on apical surface
• Microvilli: (ex) in small intestine
– Finger-like extensions of the plasma
membrane of apical epithelial cell
– Increase surface area for absorption
• Cilia: (ex) respiratory tubes
– Whip-like, motile extensions
– Moves mucus, etc. over epithelial surface 1way
• Flagella: (ex) spermatoza
– Extra long cilia
– Moves cell
Cilia in
tracheaa
Human Anatomy, Larry M. Frolich, Ph.D.
Connections
between
epithelial cells
• Desmosome: binding
spots between cells
with proteins called
cadherins
• Tight junctions:
impermeable
– E.g. gut tube, doesn’t
let enzymes from gut
into blood stream
• Gap junctions: tubes
that let small
molecules pass
between cells
Human Anatomy, Larry M. Frolich, Ph.D.
Name that Epithelial Feature!
(name and location on cell)
3
1
2
• Cilia 3
• Tight
1
junction
• Microvilli 2
• Basement 4
membrane
4
Human Anatomy, Larry M. Frolich, Ph.D.
Classes of Epithelia
• Simple: just one
layer or cell
shape
• Stratified:
multiple layers
and cell shapes
Human Anatomy, Larry M. Frolich, Ph.D.
Simple Epithelia
Type
Cell shape
Example
Squamous
Squashed
Cuboidal
Cubed
Endotheliu m (lin es blood
vessels), mesothelium
(serous lining of celom)
Walls of glands
Columnar
Columns
Pseudo-stratified
Flat cells give rise
to columns
Linin g of gut tube;
sometimes with cilia lik e
lining of uterine tube
With cilia in respiratory
tubes to move
mucous/particles out of
lungs
Simple squamous
epithelium from
alveolus of lung
Human Anatomy, Larry M. Frolich, Ph.D.
Stratified Epithelia
• Squamous
– E.g. epidermis
• Transitional
epithelium
– E.g. urinary
structures--bladder
– Stretches from 6
cells to 3 cells thick
as bladder fills and
expands
Human Anatomy, Larry M. Frolich, Ph.D.
Human Anatomy, Larry M. Frolich, Ph.D.
Quiz!!
E
Can You Identify the
Classes of Epithelium?
D
A
B
C
Human Anatomy, Larry M. Frolich, Ph.D.
Glands: epithelial cells that make
and secrete a water-based substance
• Exocrine Glands
– Secrete substance onto body
surface or into body cavity
– Have ducts
– E.G., salivary, mammary, pancreas,
liver
• Endocrine Glands
– Secrete product into blood stream
– Either stored in secretory cells or in
follicle surrounded by secretory cells
– Hormones travel to target organ to
increase response
– No ducts
Human Anatomy, Larry M. Frolich, Ph.D.
CONNECTIVE TISSUES
• “Areolar tissue” as model
• Universal in body
• Underlies epithelium, supports
capillaries, small nn.
• Always originates from mesenchyme
• CELLS in MATRIX
Human Anatomy, Larry M. Frolich, Ph.D.
Extracellular matrix
• Fibers
– Collagen gives structure
– Reticular fibers (crossed collagen) gives
order
– Elastin gives elasticity
• Ground substance
– Jelly-like material made of sugarprotein molecules (proteoglycans)
Human Anatomy, Larry M. Frolich, Ph.D.
Cells of Connective Tissues
• Fibroblasts make fibers
• Immune cells in areolar tissue
–
–
–
–
Macrophages
Plasma cells
Mast cells
Neutrophils, Lymphocytes
Human Anatomy, Larry M. Frolich, Ph.D.
Human Anatomy, Larry M. Frolich, Ph.D.
Areolar connective tissue
Human Anatomy, Larry M. Frolich, Ph.D.
“Loose” connective tissues
• Adipose tissue mostly under skin and
in mesenteries
• Reticular: organized 3-D network of
fibers that support lots of cells
– E.g. marrow, spleen, lymph nodes
Human Anatomy, Larry M. Frolich, Ph.D.
Human Anatomy, Larry M. Frolich, Ph.D.
“Dense” Connective tissues
• Irregular
– Thick fibers running in many planes
– E.g. dermis, fibrous capsules around
organs
• Regular
–
–
–
–
Aligned parallel fibers
Resists tension
E.g. tendon, ligaments, aponeuroses
Sometimes with elastic fibers (e.g.
ligamentum nuchae)
Human Anatomy, Larry M. Frolich, Ph.D.
Human Anatomy, Larry M. Frolich, Ph.D.
Other Connective Tissues
• Bone
• Cartilage
• Blood
Human Anatomy, Larry M. Frolich, Ph.D.