Notes – Chapter 5
Tissues
Tissue: collection of specialized cells and cell products that perform a relatively limited
number of functions
Histology: the study of tissues
Major Types
1. epithelial
2. connective
3. muscle
4. neural
Epithelial tissue: composed of epithelia, layers of cells that cover internal and external
organs, and glands, secretory structures derived from epithelia
Functions of Epithelia
1. physical protection
2. control permeability
3. provide sensation – richly innervated
4. produce specialized secretions (gland cells)
Basement membrane: epithelial cells hold on to each other and remain firmly attached
to the rest of the body
Epithelia
Simple – one cell layer covers the basement membrane, thin and delicate, found where
secretion or absorption takes place ex. Gas exchange and intestines
Stratified – several cell layers cover the basement membrane, found in places of great
mechanical stress
Shapes – squamous, cuboidal, columnar
Types
Simple squamous
Description
Cells flat (fried egg)
Simple cuboidal
Cubed shape
Simple columnar
Cells taller than
wide
Pseudostratified
Some cells fail to
reach the free
surface giving the
appearance of
Function
Diffusion, secretion,
absorption
Secretion,
absorption, ciliary
movement of mucus
Secretion,
absorption, ciliary
movement
Secretion, ciliary
movement
Location
Alveoli, capillaries
Bronchioles, kidney
tubules, liver,
thyroid
Stomach, intestines,
uterus
Nasal cavity,
trachea, bronchi
Stratified squamous
layers, all cells
touch the basement
membrane
Several layers of
flattened cells
Abrasion resistance
Stratified cuboidal
Several layers of
cubed shaped cells
Sex production,
lining of ducts
Stratified columnar
Several layers of
columnar shaped
cells
2-6 layers thick with
the base cells
cuboidal and the
surface cells more
flattened
Transition between
strat. squamous and
simple columnar
Allows for
distention as an
organ fills with fluid
T ransitional
Epidermis, oral
cavity, esophagus,
anal cavity and
vagina
Ducts of sweat
glands and testes,
follicles of ovaries
Scarce, some
regions of larynx
and rectum
Parts of urinary
system only
Connective Tissue
Most variable, abundant and widely distributed
Functions
1. binds structures together
2. provides support
3. serves as a framework
4. fills spaces
5. stores fat
6. produces blood cells
7. provides protection against infection
8. helps to repair tissue damage
Cell types
Resident cells: usually present in relatively stable numbers
Fibroblasts: most common, large star shaped; produce fibers by secreting
proteins in a matrix of connective tissue
1.
collagenous fibers: thick, threadlike composed of
collagen; grouped in long parallel bundles; flexible but
only slightly elastic; great tensile strength ex. tendons
(connect muscle to bone); abundant collagenous fibers
also referred to as dense connective tissue and are
sometimes called white fibers because of their light
coloration
2.
elastic fibers: composed of microfibrils embedded in
elastin (protein); fibers tend to be branched in a mesh
shape; less strength than collagenous fibers, but are very
elastic (easily stretched, but can resume original shape);
sometimes called yellow fibers
3.
reticular fibers: very thin and composed of collagen;
highly branched and form delicate supporting networks
for a variety of tissues
Mast cells: large cells located near blood vessels release heparin (prevents
blood clotting) and histamine (vasodilator)
Wandering cells: appears temporarily in tissues, usually in response to injury or
infection
WBC – macrophage
(Listing of connective tissue see chart)