Topic 7: histology (tissues) Flashcards
what is a tissue?
-a group of cells with similar structure and function
what are the 4 major tissue types?
-epithelial tissue
-connective tissue
-muscle tissue
-nervous tissue
what is a cell junction?
-points of contact between adjacent cells
-seen in epithelial tissue, some nervous and muscle cells
-not in CT because cells are too far apart
how are cell junctions formed?
-by cell membrane proteins
what are the 3 examples of cell junctions?
-tight junctions
-anchoring junctions
-gap junctions
what are tight junctions?
- a partial fusion of specific proteins (on the lateral surface, furtherest away from center)
-forms a tight ring-like seal
-prevents materials from passing between cells
-bacteria,
proteins, sometimes
fluid or ions (depends on
tissue)
what are anchoring junctions?
-proteins that fasten cells to each other and/or the extracellular material
-rivets
-ex: desmosomes
what are gap junctions?
-open channels through the adjacent cell membranes that interconnect the cytosol of the cells
-allows ions/small molecules to pass (from one cell to another)
-tissues work as a unit
-found in epithelial and cardiac and smooth muscle tissue
why is it important for tissues to work as a unit in smooth and cardiac muscle?
-allows synchronization of contractions
what gives connective tissue its subtypes and characteristics?
-extracellular material
-whats surrounding the cell
what is epithelial tissue?
-lining tissue
-first line of defence
-on the outside of the body (surface)
-lines many organ cavities (ex: stomach)
-found in secretion areas and glands
what is connective tissue?
-supports and connects tissues
-cells are far apart, get separated by the extracellular matrix
-has variable vascularity (has either lots of blood vessels or very few)
connective tissue cell types
-BLAST
-creates matrix
-ex: osteoblast,
chrondroblast,
fibroblast
-CYTE
-maintains the matrix
-ex: osteocyte,
chrondrocyte,
fibrocyte
-CLAST
-breaks down the
matrix
-ex: osteoclast (breaks
because there isn’t
Ca2+
what is muscle tissue?
-contractile tissue
what is nervous tissue?
-signalling tissue
what is an organ cavity? what is it filled with?
-lumen
-filled with fluid typically
what are the characteristics of epithelia?
-has one free surface (not connected to anything)
-little extracellular space between cells
-avascular (NO BLOOD VESSELS) because connective tissue takes care of that
-basement membrane
what is a basement membrane?
-extracellular layer
-attaches epithelium to the underlying connective tissue layer
-like velcro
what happens when the basement membrane breaks?
-BLISTERS
how are epithelial tissues classified?
-named according to the # of layers
-the shape of the cells in the layer that touches the free surface
classification of layers of cells (epithelial)
-number of cell layers sitting on the basement membrane
-one layer is simple
-more than one is stratified
classification of the shape of cells (epithelial)
-flattened (sqaumous)
-round or cube (cuboidal)
-rectangular (columnar)
simple epithelia
-allows the exchange of molecules (gasses, nutrients, etc)
-absorption and secretion
what are the subtypes of simple epithelia?
-simple squamous
-ex: lungs
-simple cuboidal
-ex: kidneys
-simple columnar
-ex: stomach and small
intestine
what are the subtypes of stratified epithelia?
-stratified squamous (common)
-ex:skin
-stratified cuboidal (rare)
-stratified columnar (rare)
stratified epithelia
-protective purposes
-in areas of abrasion
what is the apical layer?
-layer of cells touching the free surface
pseudostratified epithelia
-FAKE
-columnar cells
-appears stratified but is actually simple
-appears this way because nuclei dont line up (random)
-some cells are taller or shorter
-all cells still sit on the basement membrane
-ex: lines most of the respiratory tract (ciliated)
transitional epithelia
-cell shape and layering varies with stretching of the tissue
-only in inner lining of
the urinary system
-cuboidal > squamous when stretched
what happens when epithelial cells form a gland?
-the cell shape and layer classification is not applied
glandular epithelium
-used for secretion
-all glands are epithelium
what are the subtypes of glandular epithelium?
-exocrine glands
-endocrine glands
exocrine glands function
-secrete products onto body surface or into a body cavity
-can be uni or multi cellular
unicellular exocrine glands
-secrete mucus (into a cavity)
-in the digestive, urinary, reproductive, and respiratory tracts
-ex: goblet cells
multicellular exocrine glands
-consists of secretory and duct cells
-ducts connect secretions to a surface or cavity
-ex: glands such as sweat, oil, mammary, or digestive
endocrine glands
-dont have ducts
-secretes hormones to the interstitial fluid and then it enters the blood plasma to be transported to target cells/tissues
-ex: thyroid gland secretes thyroid hormone
what are the functions of epithelia?
-protection
-often stratified
squamous
-ex: epidermis
-secretion
-glandular epithelium
-ex: thyroid or sweat
glands
-control of permeability across membranes
-simple epithelia
typically
-exchange of
materials
-ex:kidney, intestine,
capillaries
what is the extracellular matrix composed of?
-fibres (proteins)
-ground substance
what are the proteins that make up the matrix?
-collagen fibres (for strength)
-elastic fibres (for stretch and recoil)
-reticular fibres (form networks)
-ex: CT part of
basement membrane
what is ground substance?
-unstructured material surrounding the cell and fibres
-composed of water (interstitial fluid) and large organic molecules (proteins + carbohydrates)
what are the classifications of connective tissue?
-CT proper
-cartilage
-bone
-blood
types of CT proper?
-loose CT
-dense CT
loose CT types
-areolar CT
-loosely arranged
collagen and elastin
fibres surrounded by
ground substance
-fibroblasts/fibrocytes for cells
-highly vascular (below epithelia)
-ex: lamina propria
-adipose CT
-very little matrix
-large cells
(adipocytes) store
triglycerides
-tissue looks like
chicken wire
-highly vascular
-lots of energy stored, want to constantly be able
to add or take away
dense CT characteristics
-has many fibres (also known as fibrous CT)
-has little ground substance
-poorly vascular
why is dense CT poorly vascular?
-because they are so dense that there is not enough room for many blood vessels
types of dense CT
-dense regular
-collagen fibres
running in the same
direction (stretch well in that 1 direction)
-ex: tendons + aponeuroses
ligaments
-dense irregular
-collagen fibres are
arranged irregularly (in
multiple ways)
-ex: dermis of the skin
what is the purpose of cartilage? why is it smooth?
-to reduce friction between bones
what cells are in cartilage?
-chrondocytes
-located in the lacunae
(cavities in the matrix)
-chrondoblasts
what is in the matrix of cartilage?
-fibres of collagen and elastin (proteins)
-ground substance
-mostly water, firm due to organic molecules
present
-large amounts of matrix
is cartilage avascular or vasucular?
-avascular
-heals slowly (less blood flow)
what are examples of cartilage?
-hyaline cartilage (most abundant)
-trachea
-ribs
-ends of long bones
-elastic cartilage (many elastic fibres)
-epiglottis
-ear pinna
-fibrocartilage (high in collagen fibres, shock absorber)
-intervertebral discs
-pubic symphysis
what cells are in bone?
-osteocytes (lacunae)
-osteoblasts
-osteoclasts
what is the bones matrix composed of?
-fibres (collagen abundant)
-ground substance
-inorganic calcium, phosphate salts, organic
components (proteins + carbohydrates) to make it
rigid, little water
is bone vascular or avascular?
-very vascular
what cells are in the blood?
-red blood cells
-white blood cells
-platelets
what is in the matrix of blood?
-called plasma
-soluble fibres (fibrinogen)
-ground substance is mostly water with ions and proteins
what is a main characteristic of muscle tissue?
-contractile
what are the subtypes of muscle tissue? which are striated?
-skeletal (striated)
-cardiac (striated)
smooth (non-striated)
what is the difference between striated and non-striated)
-striated
-long, branched,
cylindrical
-voluntary muscles
(ex:arms and legs)
-non-striated
-spindle shaped
-involuntary muscles
(ex:bladder, eyes, skin)
what cell types are in nervous tissue?
-neurons
-glial cells
what do neurons do?
-conduct electrical pulses
-send signals
what do glial cells do?
-support and protect neurons
what surrounds the cells within tissues?
-interstitial fluid (water + ions)
how do tight junctions aid in integral membrane proteins?
-prevent integral proteins from moving between the apical surface (top/exposed) and the basolateral surface (bottom/attached) of the cell
what do the prefixes for the CT cell types mean?
-osteo = bone
-chondro = cartilage
-fibro = fibre
what do tendons + aponeuroses connect?
-muscle to bone
what do ligaments connect?
-bone to bone
why is it hard to heal ligaments, aponeuroses, and tendons?
-because of low vascularity in the tissue (little transport to these areas)
what happens to the collagen in our bones over time?
-lost over time (decrease in flexibility)
what is the most atypical type of connective tissue? what form of this tissue makes it more typical?
-blood (because it is fluid)
-clotted blood is considered more typical
what aids in blood clotting?
-fibrinogen
