Tissues
Dr. Gerald Brasington
Tissues
Histology: The study of microscopic
structure of tissues.
 Integumentary System: The skin and its
appendages.
 Every tissue of the body falls into one of
4 main categories:
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Epithelial
Connective
Muscle
Nervous
Epithelial Tissue
Distinguished by its close association of
cells  epithelial cells are packed close
together with little material between
them.
 Epithelium is avascular.
 Epithelial tissue covers body surfaces,
lines inside of body cavities and organs,
and forms glands.

Epithelial tissue (continued)

3 main functions:
◦ 1. Protection
◦ 2. Control of permeability
◦ 3. Secretion of needed substances from glands
Epithelial tissue (continued)

Arrangement of cells results in clumps or
sheets
◦ Sheet- like: covering or lining epitheliumCovers the body and organ surfaces.
◦ Lines all hollow structures.
 Often protective  form a barrier  regulates
movement of substances
Epithelial tissue (continued)

Clump- like  Glandular epithelium
◦ Form glands

Glands- 2 types
◦ Exocrine: Secrete products into body cavities
and surfaces by way of tubular ducts.
◦ Endocrine: Secretions diffuse into
bloodstream for transport throughout body.
 Hormones
Epithelial tissue (continued)
Epithelial tissue usually has connection tissue
under it.
 Often borders a hollow space (cavity or
lumen)
 The side exposed to a body space  apical
(free) surface.
 The side exposed to connective tissue is the
basal surface.
 Basement membrane- layer of protein fibers
anchor epithelial sheet to connective tissue.

Classification of epithelial tissue

Cell shape
◦ Squamous- Flat with a thin nucleus
◦ Cuboidal- Cube-shaped with round nucleus near
the center of the cell
◦ Columnar- Tall with an oval nucleus near the basal
surface
◦ Transitional- Shape changing from round when
tissue is relaxed to flat when tissue is stretched.

organization (layers)
◦ Simple- One layer
◦ Stratified- Multiple layered.
Connective Tissue
Arises from Mesenchyme
 Embryological Mesenchyme
 5 types of connective tissue:
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Loose Connective Tissue
Dense Connective Tissue
Cartilage
Bone
Blood
Connective Tissue (Continued)

General function is to connect and
support the tissues and organs of the
body.
Muscle Tissue
Specialized cells containing molecular
filaments of protein (Myosin and Actin)
arranged in parallel bundles.
 The filaments enable the cells to shorten
in length (contract).
 Contraction of many cells in a
coordinated manner cause body
movements.
 Also aids in temperature regulation.

Muscle Tissue (Continued)

3 types of muscle
◦ Skeletal: attached to bones; Main type;
Voluntary; cells and very long & cylindrical.
Striped appearance  striations.
◦ Smooth: Sheets that contribute to the walls of
hollow organs blood vessels, Stomach, Small
intestines. Cells are spindle shaped, lack
striations, involuntary control.
◦ Cardiac: Forms the wall of the heart.
Branched, contain striations. Intercalated
Discs.
Nervous Tissue
Neural tissue is specialized cells that
“communicate” with each other through
electrochemical signals (conductivity).
 The cells are called Neurons. Found in
brain, spinal cord, and nerves.
 Contain a large axon  conducts signal to
other cells.
 Numerous, smaller dendrites  receive
signals from other cells.
 Neuroglia: small non-conductive support
cells.
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The End