week 4 Flashcards
What must happen before specimens can be studied under microscope?
Specimen must be preserved and stained. Different parts of cells take up different dyes
acidic stains
negatively charged molecules
Basic stains
positively charged molecules
How are tissues stained for transmission electro microscopy? How does the stain work?
Heavy metal salts. Metals give contrast by deflecting electrons in the beams to different extents. Produces shades of grey because electron waves don’t have color.
scanning electron microscopy
3d pics of unsectioned tissue surface.
Artifacts
minor distortions in tissues caused by preservation
epithelial tissues
cover or line body cavities.
Types of epithelial tissues
- covering and lining membranes
- Glandular epithelium
Covering and lining epithelium
- Makes outer layer of skin
- lines body cavities
- covers organs and walls of organs
Glandular Epithelium
Fashions glands of body
T/F: Nearly all substances received or given off by the body must pass through and epithelium
True
Roles of epithelium
- Protection
- Absorption
- Filtration
- excretion
- Secretion
- Sensory reception
Five distinguishing characteristics of epithelium
- Polarity
- Specialized contacts
- Supported by connective tissue
4.Avascula but innervated - Regeneration
What is Apical-Basal Polarity of epithelium?
has apical and basal layers
Apical surface
not attached to surrounding tissue. Exposed to either outside of body or cavity of internal organ
basal surface
attached to underlying connective tissue
Most apical surfaces have
microvilli
microvilli
fingerlike extensions of plasma membrane. Increase surface area
Brush border
large amounts of microvilli found in absorbing or secreting tissues
cilia
tiny hailike projections that can help propel substances
basal lamina
noncellular, adhesive supporting sheet made of gycoproteins. Next to basal surface of epithelium. Filters which molecules from connective tissue can enter epithelium. Helps transport epithelial cells for wound repair
Specialized Contacts of epithelial tissue
except for glandular epithelium, epithelial cells fit cosely to make continous sheets. Joined by tight juctions and desmosomes.
All epithelial rest upon and are supported by ___________ tissue
connective
Basement membrane
Between epithelial and connective tissues
basement membrane purpose
- helps resist stretching and tearing
- Defines epithelial boundary
parts of basement membrane
basal and reticular lamina
reticular lamina
layer of extracellular material. Has fine layer of fine collagen proteins
Important characteristic of cancerous epithelial cells?
They can’t respect the basement membrane boundary and penetrate tissues underneath
What does avascular but innervated mean?
No blood vessels, but it does have nerve fibers.
What gives epithelial cells nourishment?
Blood vessels in connective tissues
Regeneration of epithelial tissue
highly regenerative.
What causes epithelial cells to regenerate?
exposure to friction, destruction of apical basal polarity and lateral contacts
Simple epithelia
single cell layer
Where is simple epithelia found?
where absorption, filtration and secretion occur
Stratified epithelia
two or more cell layers stacked on top of each other. Where protection is important. Skin surface, lining of mouth.
squamous, cuboidal, columnar
flat disc like, cube shaped, column shaped
stratified epithelia are named after
shape of cells in apical layer
Stratified epithelia naming convention
shape of cells in apical layer
Endothelium
inner covering. Single layer of squamous cells that line the walls of the heart, blood vessels and lymphatic vessels
Mesothelium
Found in serous membranes lining ventral body cavity and covering its organs
capillaries consist exclusively of
endothelium
functions of simple cuboidal epithelium
secretion and absorption. Ducts of glands and kidney tubules
Simple columnar epithelium function
absorption and secretion. has dense microvilli on absorbative cells. Has tubular glands that secrete mucus containing intestinal juice. Some have cilia that move substances along
Where to find simple columnar epithelium
lines digestive tract from stomach to rectum.
Pseudostratified columnar epithelium function
secretes or absorbs substances. lines most of respiratory tract
Most widespread of the stratified epithelium?
stratified squamous epithelium
describe stratified squamous epithelium
free squamous surface cells, cells of deeper layers are cuboidal or columnar.
Where is stratified squamous epithelium found
wear and tear. External surface of skin extends a little into every body opening that is continous with the skin. Outer layer is keratinized.
Keratinized
surface cells contain keratin
stratified cuboidal epithelium found in
ducts of larger glands. Swaet glands and mammary glands. Rare. two layers of cuboidal cells
Stratified columnar epithelium location
limited distribution. Pharynx, male urethra, lining glandular ducts. Transition areas, junctions between other types of epithelia. Only apical layer is columnar
Transitional epthelium
forms lining of hollow urinary organs. stretches. Apical cell shape varies on degree of distension
Gland
one or more cells that secrete a particular product
aqueous fluid that contains proteins. Comes from glands. Can release lipid or steroid rich secretions
secretion
Is secretion passive or active
active
secretion can refer to
both the glad’s product and the process of making the product
How are glands classified?
endocrine and exocrine & unicellular or multicellular
which glands are scattered within epithelial sheets
unicellular
which glands form by invagination “inward growth” of an epithelial sheet into connective tissue
multicellular
How are exocrine glands formed?
retain connecting cells, which form a duct that transports secretions to the epithelial surface
endocrine glands formation
lose ducts during development. Secrete hormones into interstitial fluid. These hormones then enter the blood.
Which are ductless glands and why?
endocrine glands are “ductless”. They lose their ducts during development.
How do endocrine glands respond?
- Make hormones and put them out through exocytosis,
- Hormones go into blood or lymphatic fluid and travel to targets.
ex. hormones made by intestinal cells cause pancreas to release enzymes
diffuse endocrine system
hormone producing cells can be scattered such as those in digestive tract or in brain
exocrine glands
secrete products onto body surfaces or into body cavities. secretions are carried to a site via a duct. .
endocrine glands
ductless, empty their hormonal products into blood
unicellular exocrine glands
mucous cells and goblet cells, in intestinal and respiratory tract
mucin
made by unicellular exocrine cells. dissolves in water to form mucus
goblet cells
make mucous
multicellular exocrine glands parts
- epithelium derived duct
- secretory unit surrounded by supportive connective tissue. Forms fibrous capsule that divides gland into lobes
Structral classification of multicellular exocrine glands
simple
compound
simple multicellular exocrine glands
unbranched duct
compound multicellular exocrine glands
branched duct
tubular glands
secretory cells form tubes
alveolar/acinar glands
secretory cells form small sacs
merocrine glands
produce secretions intermittenly; secretions don’t accumulate in gland. Products are secreted by exocytosis as they are produced
“merely secrete”
which glands are merocrine glands
pancreas, most sweat glands, salivary glands
holocrine glands
accumulate products until they rupture. Replaced by division of underlying cells
holocrine gland secretions include
synthesized product + dead cell fragments.
example of holocrine glands
sebaceous glands
apocrine glands
accumulate products but just beneath free surface. eventually, apex of cell pinches off. Releasing secretory granules and cytoplasm. Cell repairs damage and it repeats. Maybe mammary gland lactation
Most abundant and widely distributed tissue in the body
connective tissue
major functions of connective tissue
- binding and supporting
- protecting (skeleton)
- insulating
- storing reserve fuel (fat)
- transporting substances within the body (blood)
Common characteristics of connective tissues
- Extracellular matrix
- common origin
extracellular matrix
nonliving. Made of ground substance and fibers; separates living cells
Extracellular matrix function
bear weight, withstand tension, bear physical trauma and abrasion
common origin of connective tissue
all connective tissues come from the mesenchyme (embryonic tissue)
t/f different connective tissues have different vascular supplies
true. Cartilage is avascular, dense connective is poorly vascularized,
three main components of connective tissues
ground substance, fibers and cells
areolar connective tissue
“prototype” connective tissue
ground substance
unstructured material that fills the space between cells . Contains fibers. Has 3 components.
interstitial fluid
Large amounts of fluid found in space around cells. Acts as molecular sieve through which nutrients and dissolved substances can diffuse between blood capillaries and the cells
Cell adhesion proteins
connective tissue glue lets connective tissue cells to attach to extracellular matrix
Proteoglycans
has protein core. Large plysaccharides (glycoaminoglycans) are attached. chondroitin sulfate and hyluronic acid stick out of protein core, like fibers of a bottle brush. GAGs trap water. The higher GAG content, the more viscous the ground substance.
Connective tissue fibers
proteins that provide support. Collagen, elastic, reticular
strongest and most abundant connective tissue fibers
collagen
collagen fibers
extremely tough, high tensile strength. Made by cross-linked fibrils wound together. Stronger than steel
Elastic fibers
Fiber made from elastin protein, gives rubbery and resilient quality to matrix
Elastic fibers found in
Skin, lungs and blood vessel walls
reticular fibers
short, fine fibers. Mafe of different collagen. Branch extensively to make networks. Surround small blood vessels, support soft tissue organs. most common where connective tissue is close to other tissue types
-blast
immature
-cyte
mature
fibroblasts
Young, actively mitotic cells that makes fibers of connective tissue
fibrocytes
Mature fibroblast; maintains matrix of fibrous connective tissue
chondroblasts
mitotically active cell of cartilage
Chondrocytes
mature cell of cartilage
Osteoblasts
Bone forming cells
Osteocytes
mature bone cells
can cells revert back to blast form?
yes, usually in case of injury
hematopoietic stem cell
blood forming cell; not located in blood; doesn’t make plasma matrix of that tissue
adipocytes
fat cells
WBCs
tissue response to injury
mast cells
cluster along blood vessels. detect microorganisms, initiate local inflammatory response
mast cell cytoplasm contains
granules
What do granules contain?
chemicals that mediate inflammation, especially in severe allergies
Heparin
anticoagulant chemical. Prevents blood clotting when free in bloodstream. Human mast cells regulate action of other mast cell chemicals