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Tissue Notes
I.
Epithelial Tissue
a. Sheet of cells that cover a body surface
b. Lines a body cavity
c. Glandular – found in the glands of the body
d. Functions
i. Protection
ii. Absorption
iii. Filtration
iv. Excretion
v. Secretion
vi. Sensory reception
e. Special characteristics
i. Cellularity
1. Close-packed cells, little extracellular material and space between
cells
ii. Specialized contacts
1. Fit close together to form sheets
2. Tight junctions and desmosomes
iii. Polarity
1. Cells near the apical surface differ from those at the basal surface
2. Apical surface – free surface of all epithelial cells
a. Most have microvilli to increase surface area for absorption
and secretion
b. Some have cilia –propel substances along the free surface
3. Basal surface – site of attachment
iv. Basement membrane
1. Helps resist stretching and tearing forces
2. Basal lamina – thin sheet between the epithelial tissue and the
underlying connective
a. Acts as a filter
b. Acts as a framework for tissue repair, needed for
regeneration
3. Reticular lamina – fine network of collagen fibers
v. Innervated but avascular
1. Supplied with nerve fibers
2. No direct blood vessels
vi. Regeneration
1. High capacity to regenerate as long as they receive proper nutrition
f. Classification
i. 2 names:
ii. 1st – number of cell layers,
1. Simple – single cell layer
a. Found where absorption and filtration occur
2. Stratified – 2 or more cell layers
iii.
iv.
v.
vi.
vii.
viii.
ix.
x.
a. Common in high use areas
b. Shape is determined by those on the apical surface
3. Pseudo – appears to be multiple layers, but only one
4. Transitional – type of stratified, modified stratified squamous
2nd – shape of the cells
1. Squamous – flattened, scale – like
2. Cuboidal – cube shaped, as tall as they are wide
3. Columnar – column shaped, taller then width
4. The shape of the nucleus matches the shape of the cell
Simple Squamous
1. Single layer of flattened cells, sparse cytoplasm
2. Resemble a tiled floor
3. Found where filtration and exchange of substances occurs
frequently
Simple Cuboidal
1. Single layer of cube shaped cells
2. Functions are secretion and absorption
3. Found in glands, kidney tubules
Simple Columnar
1. Single layer of tall closely packed cells
2. Functions are absorption and secretion
3. Lines the digestive tract
a. Dense microvilli
b. Goblet cells – secrete a protective substance
4. Simple ciliated columnar epithelium – contain cilia on apical
surface
a. Found in the respiratory tract
Pseudostratified Columnar
1. Single layer of columnar cells that vary in height
2. All cells begin on the basement membrane
3. Cell nuclei are at different levels
4. Functions in secretions and absorption
5. Pseudostratified ciliated columnar – contain cilia
a. Found in respiratory tract
Stratified Squamous
1. Most common epithelium
2. Several layers of cells, apical surface are squamous, basal surface
may be cuboidal or columnar
3. Found in high use areas, skin, most body openings
4. Surface cells are constantly being lost and replaced
5. Nutrients are received by diffusion from underlying cells
Stratified Cuboidal and Columnar
1. Rare
2. Forms large ducts of some glands
Transitional
1. Form the lining of urinary organs that need to stretch
2. Basal cells are usually cuboidal and columnar
3. Apical cells vary
4. As the tissue stretches, the membrane moves from 6 layers to 3
layers and back as it relaxes
g. Glandular Epithelium
i. Gland – one or more cells that secrete a product
1. Aqueous fluid that usually contains proteins
2. Secretion is an active process, material removed from the blood
and transformed into the product
3. Endocrine – ductless, no opening to the outside
a. Produce hormones that enter the blood
4. Exocrine – with ducts
a. Secrete products through a duct to body surfaces or into
cavities
b. Ex: mucous, sweat, oil, saliva, etc.
c. Unicellular – single cells with no ducts
i. Produce mucin, dissolves in water
ii. Forms mucus when dissolved – slimy covering
iii. Common – goblet cells
d. Multicellular - epithelium-derived duct and a secretory unit
i. Has supportive connective tissue, blood vessels,
nerve fibers
ii. Defined by shape and method of secretion
II.
Connective Tissue
a. Found everywhere in the body
b. Functions
i. Binding and support
ii. Protection
iii. Insulation
iv. Transportation
c. Common characteristics
i. Common origin – mesenchyme
1. Embryonic tissue
ii. Degrees of vascularity
1. Muscle & nervous are very vascular
2. Cartilage is avascular
3. Dense connective tissue is poorly vascularized
4. Other types vary in vascularity
iii. Extracellular matrix
1. Nonliving
2. Separates the living cells of the tissue
3. Because of the matrix – CT can bear weight, withstand tension
d. Structure of CT
i. Ground substance, fibers, cells
ii. Arrangements vary in different types of tissues and locations
iii. Ground substance
1. Unstructured material that fills the space between the cells
2. Contains fibers
3. Interstitial fluid
4. Holds fluid
5. Functions as a medium through which nutrients can pass between
blood capillaries and cells
6. Cell adhesion proteins – serve as “glue” that allows cells to attach
to matrix elements
iv. Fibers
1. Provide support
2. Collagen
a. Formed from the protein collagen
b. Secreted into the extracellular space and form cross-linked
fibers
c. Tough and have great tensile strength
d. Stronger then steel fibers of the same size
e. Appear shiny white
3. Elastic
a. Formed from the protein elastin
b. Randomly coiled that allows it stretch and recoil
c. CT can only stretch so much before the collagen fibers are
taught
d. When tension releases, the elastic fibers bring the tissue
back together
e. Skin, lungs, blood vessel walls
4. Reticular
a. Fine collagenous fibers
b. Highly branching that form networks
c. Support soft tissue organs
v. Cells
1. Exist as immature and mature cells
2. (Immature) The primary cell of different kinds of tissue –
undifferentiated using the suffix “blast”
a. CT proper – fibroblast
b. Cartilage – chondroblast
c. Bone – osteoblast
d. Blood – hemocytoblast
3. Mature cells – use the suffix “cyte”
a. Maintain the health of the matrix
4. CT is “home” to many other types of cells
a. Fat cells, white blood cells, plasma cells
e. Types of CT
i. Differences in cell type, fiber type, and proportion of matrix contributed
by fibers
ii. Embryonic – mesenchyme
iii. CT proper –
1. Loose CT
a. Areolar CT – most widely distributed in the body
i. Semifluid or gelatinous ground substance appears as
empty spaces
ii. Loose arrangement of fibers
iii. Fibroblasts, fat cells, mast cells
iv. Reservoir for water, salts
v. Soaks up excess fluid during inflammation – edema
b. Adipose – Fat
i. Similar to areolar with higher nutrient storing
ability
ii. Adipocytes – mature fat cells
iii. Nucleus is compressed pushing it to one side by a
droplet of oil
iv. Mature adipocytes can not divide, largest cells in
the body
v. Very vascular
vi. Tightly packed
vii. Without adipose tissues, cease living after a few
days
viii. Different amounts in different parts of the body,
mostly subcutaneous
ix. Gender related
x. Shock absorber & insulation
c. Reticular CT
i. Similar to areolar but only has reticular fibers that
form a network
ii. Reticular cells are scattered in the framework
iii. Only found in few sites in the body
2. Dense Regular CT
a. All have fibers as the majority of the tissue
b. Closely packed bundles of collagen fibers in the same
direction
c. White, flexible tissue with high resistance
d. Limited stretching
e. Tendons – attach muscle to bone
f. Ligaments – connect bone to bone
3. Dense Irregular CT
a. Bundles of fibers are much thicker
b. Interwoven and irregular
c. Run in one or more plane to resist multiple forces
d. Found in the skin, joint capsules, covering around organs
iv. Cartilage
1. Qualities between bone and dense connective tissue
2. Tough but flexible
3. Avascular, not innervated
4. 80% water
5. High amounts of bound collagen fibers
6. Perichondrium – highly vascularized dense irregular CT membrane
that covers most cartilage structures
a. How nutrients reach the cartilage
7. Chondroblsts – predominate cell type, mature cartilage cells
a. Growth continues until the bony skeleton stops growing
8. Hyaline – gristle
a. Most abundant form in the body
b. Large numbers of collagen, but not very visible
c. Provides support with some pliability
d. Articular cartilage – covers the end of bone to absorb shock
e. The end of the nose, connects ribs to sterunum
f. Embryonic skeleton
9. Elastic
a. Almost identical to hyaline
b. Many more elastic fibers
c. Higher tolerance for bending
d. The outer ear, epiglottis
10. Fibrocartilage
a. Found where hyaline cartilage meets a true ligament or
tendon
b. Composition – between hyaline cartilage and dense regular
CT
i. Rows of chondrocytes alternating rows of thick
collagen fibers
c. Compressible, resists tension
d. Found in intervertebral disks, menisci in the knee
v. Osseous
1. Bone
2. Ability to support and protect softer tissues
3. Cavities for fat storage, blood cell formation
4. More abundant collagen fibers then cartilage
5. Calcium salts added to the matrix
6. Osteoblasts produce the matrix
7. Osteocytes are mature bone cells that live in the matrix
8. Very vascular
vi. Blood
1. Fluid in the blood vessels
2. Blood cells surrounded by a nonliving matrix – blood plasma
3. Fibers of blood are present during blood clotting
4. Transports nutrients, oxygen, wastes to all parts of the body
III.
IV.
Muscle tissue
a. Highly cellular, highly vascularized
b. Responsible for body movement
c. Muscle cells – muscle fibers
i. Contain myofilaments - actin and myosin
ii. Shorten, lengthen
d. Skeletal
i. Attached to bone via tendons
ii. Form the flesh of the body
iii. As they contract, pull on bones & skin
iv. Long cylindrical cells with many nuclei
v. Banded – striated appearance
vi. Voluntary contractions
e. Cardiac
i. Found ONLY in the heart
ii. Propel blood through the vessels to the rest of the body
iii. Striated
iv. Uninucleated
v. Branching shape that fit together at intercalated discs
vi. Unvoluntary
f. Smooth
i. No visible striations
ii. Spindle shaped cells
iii. One nucleus
iv. Found in hollow organs, abdomen
v. Contracts to propel material through the organ
vi. Involuntary
Nervous
a. Brain, spinal cord, nerves
b. Regulates and controls body functions
c. Neurons – specialized nerve cells that conduct nerve impulses
i. Cytoplasmic extensions conduct electrical impulses through the body
d. Supporting cells
i. Non conducting cells that support, insulate and protect the neurons