Tissues
Tissue

A group of similar cells, usually of similar
embryonic origin, that function together to
carry out specialized activities
Histology
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The science that deals with the study of
tissues
Pathologist – a scientist who specializes in
laboratory studies of cells and tissues to
make accurate diagnoses. A pathologist
examines tissues for any changes that
might indicate disease.
Types of Tissues
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Epithelial Tissue
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Connective Tissue
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protect and supports the body and its organs, binds
organs together, stores energy reserves as fat,
provides immunity
Muscular Tissue
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Covers body surfaces; lines body cavities, hollow
organs and ducts; forms glands
Generates the force needed to make body structures
move
Nervous Tissue

Detects changes inside and outside the body and
initiates and transmits nerve impulses that coordinate
body activities to help maintain homeostasis
Cell Junctions

Points of contact between plasma
membranes of different cells that join
them into functional units.
Epithelial Tissue
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AKA Epithelium
2 types:
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Covering and Lining Epithelium
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Forms the outer covering of the skin and some
internal organs. It also lines body cavities, blood
vessels, ducts, and the interiors of many of the
body systems.
Glandular Epithelium

Makes the secreting portion of glands
General Features of Epithelium
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1. Closely packed cells with little
extracellular material between them
arranged in sheets
2. Surfaces:
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Apical Surface – exposed to a body cavity, the
outside of the body or lining an internal organ
Lateral Surface – Face adjacent cells
Basal Surface – bottom layer attached to a
basement membrane (extracellular structure
composed mainly of fibers located between
epithelium and underlying connective tissue)
General Features of Epithelium
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3. Avascular – no blood vessels. Epithelial
cells must get their nutrients from
underlying connective tissue through
diffusion
4. Innervated (have a nerve supply)
5. High mitotic rate – high capacity for cell
division because of wear and tear and
injury
Covering and Lining Epithelium –
Cell Shapes

Squamous – flat cells that attach to each other
like tiles
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Cuboidal – cells are as tall as they are wide,
sometimes contain microvilli
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Function in Secretion and Absorption
Columnar – Taller than they are wide,
sometimes contain microvilli or cilia
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Allows for rapid passage of substances through them
Function in Secretion, Absorption and Protection
Transitional – Cells that have the ability to
change shape from Cuboidal to Squamous and
back as organs stretch
Simple Epithelium

A single layer of cells found in areas where
diffusion, osmosis, filtration, secretions
and absorption occur
Simple Squamous Epithelium

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
A single layer of flat cells that resembles a
tile floor when viewed from the apical
surface
Nucleus is a flattened oval found in the
center of the cell
Found where filtration or diffusion take
place, not found in areas of high wear and
tear
Simple Squamous Epithelium


Endothelium – simple squamous that lines
the heart, blood vessels and lymphatic
vessles
Mesothelium – simple squamous that lines
serous membranes (lines cavities not open
to the outside of the body, like the
abdomen or thorax)
Simple Cuboidal Epithelium
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Single layer of cube shaped cells
Found on the surface of the ovary, the
lens of the eye and lining of glands as well
as the secreting portion of glands
Function in Secretion and Absorption
Simple Columnar Epithelium
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Single Layer of Column Shaped Cells
2 Forms – cilliated and noncilliated
Non-cilliated Simple Columnar
Epithelium

Contains absorptive cells and goblet cells
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Absorptive Cells – have microvilli to increase
surface area
Goblet Cells – modified Columnar cells that
secrete mucus at the apical surface
Lines most of the GI tract, ducts of glands
and gallbladder
Ciliated Simple Columnar
Epithelium
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Cells with cilia at the apical surface,
usually interspersed with goblet cells
Mucus secreted by goblet cells forms a
thin layer over the cell surface which is
moved by the ciliated cells.
Found in the respiratory tract
Stratified Epithelium


Contains 2 or more layers of cells used for
protection of underlying tissue in area
where there is a lot of wear and tear
The name of the tissue depends on the
shape of the cell on the apical layer
Stratified Squamous Epithelium
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Cells in the apical layer are flat
Cells in the deep layers vary in shape
Basal cells continuously undergo mitosis

As they move farther from the basal layer
they become dehydrated and harder
Keratinized Stratified Squamous
Epithelium

Tough layer of keratin is deposited on the
top layers to help protect the skin and
underlying tissues from microbes, heat
and chemicals
Nonkeratinized Stratified
Squamous Epithelium

Does not contain keratin

Found on the lining of the mouth, esophagus,
and tongue
Stratified Cuboidal Epithelium
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Fairly Rare
2 or more layers of cells, apical layer is
cuboidal
Found in sweat glands
Stratified Columnar Epithelium
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Fairly Rare
2 or more layers of cells, the top layer is
columnar
Found in excretory ducts of some glands
and some mucous membranes
Transitional Epithelium

Varies in appearance depending on
whether the organ it lines is distended or
relaxed.

Looks similar to stratified cuboidal except the
top layer is large and rounded
Pseudostratified Columnar
Epithelium


Appears to have several layers because
the nuclei of the cells are at various
depths.
All of the cells are attached to the same
basement membrane so there is only 1
layer of cells
Glandular Epithelium
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Functions in Secretion
A gland consists of one cell or a group of
cells
Endocrine Glands – secretions enter the
interstitial fluid
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Hormones
Exocrine Glands – secrete their products
into ducts (tubes) that empty at the
surface of the covering/lining epithelium

Mucus, oil, earwax, digestive enzymes