Tissues Flashcards
tissue defintion
groups of cells that are similar in terms of structure and perform a common function
nervous tissue function
communication and control
connective tissue function
support and protection
epithelial tissue function
covering and lining body surfaces
muscular tissue function
movement and generation of heat
nverous tissue characteristics
Makes up nervous system
- Excitable
- Concerned with
communication and control - Highly cellular
- 2 maior cell types
- Neurons that generate and
conduct nerve impulses
(excitable) - Supporting cells
epithelium function
Covers body surfaces, lines body cavities & tubes,
forms the secretory portion of glands
Functionally = selective barrier
(secretion, absorption, transport, protection, receptor function)
how to tell if cell is epithelium
is there freee space (white void) above it, highly cellular,
Cells are in very close contact - very little intercellular (= between cells) space due to cell junctions
Cells exhibit polarity (top, sides & bottom) - morphology & function
Arranged in sheets
Highly regenerative (mitotic)
vascular (nourishment via diffusion)
Basement membrane - BM + cell unctions are indicative of epithelium (explained soon).
Sits on connective tissue
why do epithelial cells have highest rate of cancer
Epithelial cells are so mitotically active
(barrier /protective function) that theyundergo the highest number of replications of all tissue types. Increased replications,
increases risk of mutations.
Due to their protective function, epithelium is exposed to higher amounts of carcinogenic compounds - these often mutate DNA.
three domains of epithelia (3)
Apical Domain - faces free surface;
apical specialisations may be present
Lateral Domain - specialisations to keep cells very closely packed and tightly bound
Basal Domain - rests on a basement
membrane to which it is tightly bound
All 3 domains contribute to epithelium’s function of “barrier”.
Epithelial apical specialisations -
cilia and microvilli.
Cilia are much taller and wider
compared to microvilli and they have
a more complicated internal structure
lateral domain function
Resist stress
Controls what can go
across cells (barrier)
Communication between
cells
three types of cell junctions
cells very closely packed
(little extra-cellular / inter-
cellular matrix) and tightly bound
(tight junctions, desmosomes)
+ gap junctions
(cell to cell communication)
basal domain of epithelia
all epithelium is in direct association with a basement membrane
basement membrane function, defintion, what is it made up of?
Basement membrane (BM) = basal lamina (attachment site for
overlying epithelial cells and underlying connective tissue)
+ hemidesmosomes
+ underlying layer of connective tissue fires attached to BM
(4)
Functions = structural attachment - provides binding sites for cell
adhesion molecules; tissue organisation during development;
guides cellular differentiation & inhibits or promotes cell
proliferation & migration; semi-permeable selective barrier.
classification of epithelia in terms of numbers of layers
1 = simple
more than 1 = stratified
classification of epithelia cell shapes
squamous
cuboidal
columnar
simple squamous cells, location, function, description. (4)
Simple squamous cells are flat (width greater than height), nucleus bulges but is flattened and lies
parallel to the surface of the epithelium.
function Simple barrier
Rapid transfer / exchange
- fluids and gases
location
Lines blood vessels (endothelium
Body cavities (mesothelium)
Kidneys
(part of the glomerular capsule)
Lungs (forms alveoli)
simple cuboidal (4)
Simple cuboidal - cells as wide and deep as they are tall, nucleus is round, microvilli sometimes present
Functions:
Barrier
Absorption
Secretion
loication
Secretary portions and ducts of small glands
Surface of the ovary,
Kidney tubules,
Thyroid follicles
simple colomnar
single layer of cells taller than they are wide, sausage shaped nucleus tends to be positioned at the cell’s base.
May have microvilli (brush border) or cilia on apical surface.
Note the simple squamous epithelium lining the blood vessels.
simple colomnar function
Barrier (e.g. from
stomach acid)
Absorption
Secretion
simple colomnar location
Stomach,
Small & large
intestines
Pseudostratified Columnar description
Pseudostratified Columnar - looks stratified because of the way the nuclei are arranged but not all
cells reach the surface.
All cells sit on the basement membrane so classified as simple.
Pseudostratified Columnar function
Functions:
Barrier
Absorption
Secretion
Conduit
Pseudostratified Columnar locations (4)
Location examples:
Trachea & bronchi
Vas deferens & epididymis
of male reproductive tract
two types of stratified squamous (4)
non-keratinised - look at top layer of cells, if you can see nuclei, meaning that that top layer of cells is alive and they’re alive because they’re in a moist environment
keratinised - if you cant see nuclei in the top layer, you are dealing with compacted dead cells
functions of stratified squamous (4)
barrier, protection against abrasion
locations of stratified squamous cells (4)
epidermis, oral cavity, and oesophagus, vagina
transitional epithelium (4)
cell with two nuclei
Functions:
stretches to allow distension of the urinary tract; protects the underlying tissues from osmotic damage from urine (barrier)
Locations:
Parts of the kidney, ureters, bladder,
part of the urethra
Thinking about epithelium in terms of function: Secretion (4)
Columnar epithelium of the stomach and gastric glands
Thinking about epithelium in terms of function: Absorption (4)
Columnar epithelium of intestines & cuboidal epithelium in parts of the nephron in the kidneys
Thinking about epithelium in terms of function: Transport (4)
Transport of materials along the surface of the epithelium (pseudostratified columnar)
Transport of material across an epithelium to and from the underlying connective tissue (simple epithelia)
Thinking about epithelium in terms of function: Protection (4)
Stratified squamous & transitional
Thinking about epithelium in terms of function: Receptor Function
Receive and transduce external stimuli,
e.g. taste bids, olfactory epithelium,
retina
gland definition
Gland = cell or organ that secretes substances for use elsewhere in the body
The gland itself may produce a product (secretion) OR
the product may be something removed from tissues and modified by the gland (excretion)
types of glands
2 types of glands
Exocrine
usually maintains contact with surface by way of duct (a tube of epithelium that conveys
secretion to Surface).
Examples = salivary glands, sweat glands, mammary glands
(I) Endocrine - no contact with surface
(lost during development). so no ducts: product (= hormones) is
secreted directly into the blood.
Examples = pituitary, thyroid, adrenal glands
Some glands are
unicellular. ea. goblet cells
Some
organs have both
exocrine and endocrine
unctions, e.g. pantieds
types of secretion
Serous - thin watery secretion, e.g. tears, sweat, digestive juices
Mucous - secrete mucin (glycoprotein), mixes with H,O to produce mucus
e.g. goblet cells
Mixed - contain both serous and mucous cells, e.g. some salivary glanas
Modes of Secretion
Merocrine = product
released oy
eXoCyIOSIS
sometimes called eccrine (e.g. salivary glands)
Apocrine = droplets covered by cell membrane
and a verv thin laver of cvtoplasm bud off from
cell sunace (e.g. milk lals)
Holocrine = cells accumulate a product and then
cell disintegrates (nereby becomina the produci
lea. sebaceous alands
connective tissue info 2 know (4)
Many varied functions
Most widely variable of all tissue types
Common embryological origin
Extracellular matrix separates cells
Cells are widely spaced compared to
other tissues
May or may not be vascularised
connective tissue function
Binding & packing (epithelium, capsules around organs & joints; fat)
Support (bone, cartilage and fat)
Protection (bone & fat)
Insulation (fat)
Transport (blood - delivers phagocytic anc immune cells where required)
connective tissue what is it (4)
cells + matrix = connective tissue
space occupying matrix will always be greater than space occupied by cells
cell produce the matrix, cells are widely spread
matrix - determine the properties of the CT
= fibres + ground substance
ground substance has fibres and cells
fibres (4)
all proteins by cells (transcription and translation) G1 phase of the cell cycle.
CT cells (4)
can exist in mature and immature phases
prefix often reflects CT type: fibro, osteo, chondro
undifferentiated (immature) cells are actively mitotic and secrete fibres and ground substance: suffix = “blast” (producer)
if tissue matrix is damaged, mature cells can revert to immature forms for the purpose of repair.
ground substance
simplest example = clear. amorphous, viscous fluid / ge
ground substance functionc (4)
Fills up spaces between cells and fibres of CT
Acts as a molecular sieve
Allows for rapid diffusion of small molecules
Acts as a barrier to penetration of large molecules and foreign particles into tissues, e.g. bacteria and toxins
Transport of metabolites to and from blood vessels
Maintenance of electrolvte balance
Composed of interstitial fluid
(- fluid that surrounds cells),
cell adhesion proteins (to anchor cells in place), hydrophilic molecules - proteoglycans (characteristic CT molecules, function is to trap water)
collagen fibres
very strong,
high tensile strength
(resistance to breaking
under tension
- stretch
sionuv wavy albeane
some dive but not elastic.
manv different tvoes
elastic fibres
finer than collagen
capacitv to stretch and recoil
reticular fibres (4) (first sentence)
very fine form of collagen
not visible in most
photomicrographs used in HB1
General (fibrous) connective tissue = connective tissue proper
(i) General (fibrous) connective tissue = connective tissue proper
Two subgroups
Loose CT (Areolar, Reticular)
Dense CT (Dense regular, Dense irregular)
Specialised Connective tissues
(ii) Specialised Connective tissues
Adipose tissue
Lymphoid tissue
Blood
Cartilage
Bone
Differences between different classes and subgroups reflect cell type, fibre type and the proportion of matrix occupied by fibres
Loose Connective Tissue
2 types: reticular and areolar
Not expected to recognise reticular
(photomicrograph is FYI only)
Features = abundance of reticular fibres.
Provides a supportive mesh for cells in delicate, cellular organs like liver,
spleen, bone marrow and lymph nodes
Loose Connective Tissue
Areolar CT = all 3 fibre types + fibrocytes
(fibroblast used interchangeably)
+ white blood cells, macrophages
(= big phagocytes), adipocytes (fat cells).
Areolar CT = widely distributed packing material of the body.
Binds body parts but allows them to move freely over one another
Fibres run in multiple directions.
This allows for movement in many directions because the ground substance is semi-fluid / gelatinous.
dense connective tissue types
regular and irregular
Predominant fibre type is collagen
Fibres occupy more space than either cells or ground substance.
dense regular
Fibres all aligned in
same direction.
Thick bundles of
collagen
Poor blood supply
Fresh tissue is white
High tensile strength
(= resists a lols Ol Torce neire breaking)
Very flexible so
bends but doesn’t stretch much
dense irregular
Same elements as dense
regular but fibres are arranged
in many different directions.
Forms sheets of tissue where
tension is exerted in many
different directions
Examples = dermis of the skin,
joint capsules,
fibrous capsules of many
organs, e.g. kidneys, testes,
bones and muscles.
adipose tissue (4)
areolar CT that has been modified to store fat droplets
brown adipose tissue
associated with infants
white adipose tissue features (4)
Features: well vascularised
Predominant cell type = adipocvte
Very little matrix as cells occupy so
much space. Areolar tissue can
always convert to adipose tissue.
white adipose tissue functions
Functions:
Stores nutrients
Absorbs shock
Insulates
Holds some organs in place, e.g,
kidneys, spinal cord and eyes
= structural fat
white adipose tissue locations
Locations: as above + subcutaneous
blood as a CT (4)
Cells = BC (anucleate) & WBC (nucleate),
platelets (fragments)
Ground substance = liquid, plasma
Fibres are soluble in the plasma and only evident during clotting.
Functions:
Transport - O nutrients, waste, hormones
Protection - WBC, antibodies, platelets
Regulation - Homeostasis
(pH, body temperature, fluid distribution)
three types of cartilage (4)
hyaline, elastic, & fibrocartilage
all avascular, Intermediate between dense CT and bone
toiugh but some flexibility
can attach muscles and tendons to it
cells called chondroblasts and chondrocytes
no nerve supply so good for covering joints
most cartiliafge is covered by perichondrium
(dense irregular CT)
functions of cartilage (4) (4)
provides shape and support; template for bone growth; resists compressive forces
locations of cartilage
hyaline (synovial joints, trachea, fetal skeleton, growth zones off skeleton)
elastic (epiglottis, external ear)
fibrocartilage (pubic symphysis, intervertebral discs)
Chondroblasts - actively deposit matrix
Chondrocytes-maintenance
vascular so nourished via diffusion from the perichondrium (dense irregular CT capsule)
= limit to cartilage thickness because there is a limit to effective diffusion
Perichondrium houses chondroblasts - can add
to cartilage.
Ground substance has firmly bound collagen fibres (whether or not they are visible depends on collagen type and number of fibres).
Ground substance contains up to 80% water bound to hydrophilic molecules to create stiffness
cartilage growth
Cartilage grows by both
interstitial and appositional
means.
Interstitial
Interstitial = intervening space
- grows from the middle
outwards - cells sitting the
matrix divide and then lay
down more matrix.
Appositional
Appositional - to apply
adding more cartilage to the
outside.
