Chapter 3 - Part 5
Tissues – Groups of cells that
are similar in structure and
function.
 There are four primary
tissue types:

1.
2.
3.
4.

Epithelial (covering)
Connective tissue (support)
Nervous tissue (control)
Muscle (movement)
Tissues are organized into organs and the
arrangement of the tissues determines each
organ’s structure and what it is able to do.
 Epithelial
Tissue (Epithelium) – The
lining, covering, and glandular tissue of
the body.
 Glandular
epithelium forms various glands
in the body.
 Covering and lining epithelium covers all
free body surfaces and contains versatile
cells.
One cell type covers the outer layer of the skin.
 Others dip into the body to line its cavities.

1.
Protection

2.
Absorption

3.
Example: Epithelium that lines the stomach
and small intestine.
Filtration

4.
Example: Skin
Example: Epithelium that lines the kidneys.
Secretion

Example: Glands found in the skin such as
sweat and oil glands.
1.
Epithelial cells fit closely together to
form continuous sheets.

2.
Bound together by cell junctions
including desmosomes and tight
junctions.
The membranes always have one free
unattached surface or edge.

This so-called apical surface is exposed
to the body’s exterior or to the cavity of
an internal organ.
3.
4.
The lower surface rests on a
basement membrane, a structureless
material secreted by the cells.
Have no blood supply of their own.

5.
They are avascular and depend on
diffusion from the capillaries in the
underlying connective tissue for food
and oxygen.
If well nourished, epithelial cells
regenerate themselves easily.
 Each
1.
First Name: Indicates the relative number
of layers it has.


2.
epithelium is given two names.
Simple Epithelium – Epithelium that contains
one layer of cells.
Stratified Epithelium – Epithelium that
contains more than one cell layer.
Second Name: Describes the shape of its
cells.



Squamous Cells – Flattened like fish scales.
Cuboidal Cells – Cube-shaped like dice.
Columnar Cells – Shaped like columns.
 Simple
Squamous Epithelium –Single layer of
thin squamous cells resting on a basement
layer.




Cells fit closely together, much like floor
tiles.
Usually forms membranes where filtration
or exchange of substances by rapid
diffusion occurs.
Also forms the serous membranes, or serosae, the
slick membranes that line the ventral body cavity
and cover the organs in that cavity.
Example: Air sacs of lungs
 Simple
Cuboidal Epithelium –
One layer of cuboidal cells
resting on a basement
membrane.
Common in glands and in their
ducts.
 Forms the walls of the kidney
tubules.
 Covers the surface of the
ovaries.

 Simple
Columnar Epithelium –
Made up of a single layer of tall
cells that fit closely together.


Lines the entire length of the
digestive tract from the stomach to
the anus.
Includes:


Mucosae (Mucus Membranes) – Epithelial
membranes that line body cavities open
to the body exterior.
Goblet Cells – Produce a lubricating
mucus.
 Pseudostratified
Columnar
Epithleium – All of the cells rest on
a basement membrane; Some of
its cells are shorter than others and
their nuclei appear at different
heights above the basement
membrane.



This epithelium gives the false (pseudo) impression
that it is stratified.
Mainly functions in absorption and secretion.
A ciliated form lines the respiratory tract and
propels the mucus upward and away from the lungs.
 Stratified
Squamous Epithelium –
Consists of several layers; cells at
the free edge are squamous
whereas those close to the basement
membrane are cuboidal or columnar.


Most common stratified epithelium in the body.
Found in sites that receive a good deal of abuse or
friction, such as the esophagus, the mouth, or the
outer portion of the skin.
 Statified
Cuboidal Epithelium – Usually has
just two cell layers with (at least) the
surface cells being cuboidal in shape.


Fairly rare in the body.
Found mainly in the ducts of large glands.
 Stratified
Columnar Epithelium – At least
two cell layers; the surface cells are
columnar in shape, but its basal cells vary in
size and shape.


Fairly rare in the body.
Found mainly in the ducts of large glands.
 Transitional
Epithelium – Highly
modified, stratified squamous
epithelium that forms the lining
of only a few organs – the urinary
bladder, the ureters, and part of
the urethra.

All of the organs are part of the
urinary system and are subject to
considerable stretching.
 The
ability of transitional cells to slide
past one another and change their shape
allows the bladder, ureters, and urethra
to stretch.
When the organ is not stretched: Membrane is
many- layered and the superficial cells are
rounded and domelike.
 When the organ is stretched: The epithelium
thins and the surface cells flatten and become
squamouslike.

 Gland
– Consists of one or more
cells that make and secrete a
particular product.
 Secretion – Product secreted by a
gland


Typically contains protein molecules
in an aqueous fluid.
Secretion is an active process, in
which glandular cells obtain needed
materials from the blood and use
them to make their secretion,
which they then discharge.
Endocrine Glands – Do not contain ducts;
their secretions diffuse directly into the
blood vessels that weave
through the glands.
1.

2.
Examples: Thyroid, adrenal,
and pituitary glands.
Exocrine Glands – Do contain
ducts; secretions empty
through ducts to the
epithelial surface.


Are found both internally and
externally.
Examples: Sweat and oil glands, liver, and
pancreas.