Tissues 1 Flashcards
Describe a typical nucleus
Contains cell DNA
Double lipid membrane + pores
Nucleolus (sometimes more than 1) where large ribosome subunits are synthesised from rRNA
What is nuclear lamina
Specialised cytoskeleton on the internal surface which control (dis)assembly of the nuclear envelope during division
Describe a ribosome
2 subunits (rRNA and protein)
Describe the endoplasmic reticulum
Nuclear envelope continuous with the ER
Flattened sacs (cisternae)
RER = +ribosomes
SER = tubular (lipid synthesis + calcium storage)
Describe the golgi apparatus
Flattened membrane sacs
Vesicles bud off
Cis face (towards ER) and trans face (Towards membrane)
Describe the mitohondria
Site of ATP synthesis
Double membrane with folds into Cristae
High numbers = high metabolic activity
Describe peroxisomes
Important in oxidative pathways
Single membrane + contain enzymes involved in lipid metabolism
Eukaryotic cells
Enzymes = high conc. = crystallise into dorm cores
Peroxide produced as a by-product
What are the three main types of cytoskeleton
Microtubules, intermediate filaments and microfilaments
What is the size of microtubules
20nm
What is the size of intermediate filaments
10-15nm
What is the size of microfilaments
5-9nm
What are microtubules a polymer of
alpha and beta tubules heterodimers
What is the function of microtubules
cell shape and tracks for movement of organelles and cellular components
What are microtubules a major component of
cilia and flagellae
cilia = 9 MT doublets and 2 central MT
mitotic spindle
What type of intermediate filaments do the following cells have: epithelia, mesenchymal, neurones. muscle cells
Epithelia - cytokeratins
Mesenchymal - vimentin
Neurones - neurofilament protein
muscle cells - desmin
What is the function of intermediate filaments
Mechanical strength
Desmosome cell-cell adhesions are connected by IFs
What are microfilaments a polymer of
actin
What do microfilaments associate with
adhesion belts in epithelia
What is the functions of microfilaments
cell shape and movement
Give an example of an accessory protein to microfilaments
myosin
What are the 5 main cell groups
Connective tissue cells Contractive muscle Haematopoietic cells Neural cells Epithelial cells
What are tissues made up of
Cells, extracellular matrix and fluid
What is the name of the cancers in the following tissues: epithelial, mesenchymal, haematopoietic, neural
Epithelial - carcinoma
Mesenchymal - Sarcomas
Haematopoietic - Leukaemias (marrow) or lymphomas (lymphocytes)
Neural - neurblastomas (neurones) or gliomas (glial)
What is the ECM
Material deposited by cells to form the insoluble part of the extracellular environment. Fibrillar proteins embedded in a hydrated gel
What is the function of cell-cell junctions
Formation and maintenance of epithelia
What are the 2 forms of cell-cell junctions
Zonula (belts) or maculae (spots)
Describe cell-cell junctions in epithelia
Arranged as an apical junction complex
Tight junctions, adhesion belts and desmosomes
Describe zonula occludens
Tight junction - points on adjacent membranes
more networks = more seals
Blocks paracellular pathways
Prevents ion diffusion (polarity)
Describe zonula adherens
forms before others
closely associated to actin cytoskeleton
cadherins bind to similar molecules on adjacent cells
Describe desmosomes
Macula Adherens Cluster of pores formed my membrane protein Allows passage of ions/small molecules Cadherin-like Associated with intermediate filaments
What are the epithelial classifications
Shape and layering
Describe simple squamous epithelia
Single layer of cells with a flattened plate shape
Exchange
Alveoli, mesothelium, vessel endothelium
Describe simple cuboidal epithelia
Single layer of cells with a cube shape (irregular)
Lining of the kidney collecting duct and other ducts
Describe simple columnar epithelia
Single layer of cells that are pillar-shaped.
Enterocytes (absorptive intestinal) and absorptive and secretory epithelia
Describe stratified squamous epithelia
Multiple layers of cells with a flattened plate shape
Describe the two types of squamous epithelia
Keratinising - upper layer is dry due to hardening and death (epidermis)
Non-keratnising - upper surface is wet, cells are alive (mouth, oesophagus, anus, cervix, vagina)
Describe pseudo stratified epithelia
“Falsely stratified”
Multiple layers of nuclei and surface cells have contact with the basal membrane
Airway epithelium, ducts, urinary and reproductive tracts
Why is polarity of cells important
Produces directionality so that functions are unidirectional e.g. secretion, transport, absorption
How is activity restricted to only some parts in transporting epithelia
ion pumps and channels are distributed unevenly
What is the difference between paracellular and transcellular
para = between trans = through
What are kiss points
Focal connections
Give an example of transporting epithelia
Mitochondrial membrane
Give an example of absorptive epithelia
Intestinal epithelium (enterocytes)
What are the two types of secretory epithelia and give examples
Exocrine (apical surface to duct or lumen) - goblet cells, acinar cells
Endocrine (apical surface to bloodstream) - islets of langerhans
What can secretion be classified into
Constitutive - secretory vesicles move directly to the plasma membrane
Stimulated - secretory vesicles are stored in the cytoplasm and fuse on stimulation
Give examples of the constitutive and stimulated secretory pathways
Constitutive - plasma protein production in hepatocytes
Stimulated - release of adrenaline from the adrenal medulla
Why do protective epithelia usually form thick layers
Protect underlying tissue from physical and chemical insults (heat, cold solvents, abrasion etc.)
Which cells are replaced every 3-10 days
Gut lining
Which cells are replaced every 8-10 days
Heart muscle, fat tissue, bone
What is the turnover rate of the epidermis
48 days
Give an example of changes in steady turnover rate
cyclic production and loss of the endometrial epithelial lining of the uterus in the menstrual cycle
Increase in no. and size of epithelial glands in the breast
Describe the turnover in intestinal villi
Cells migrate up the villus as cells are constantly lost from the tip. New cells are constantly produced by the crypt stem cells
Describe turnover in the epidermis
Surface cells are constantly lost, but constantly replaced by new cells formed at the basal layer
As cells migrate up they flatten and keratinise
How does pressure affect turnover in the epidermis
Increases the rate of proliferation of stem cells and the loss of cells decreases
What does the ECM comprise of
Proteins and carbohydrates
What are the functions of ECM
Physical support
Mechanical and physiochemical properties of the tissue
Influence growth, adhesion and differentiation status
Development, tissue function and organogenesis
What are the components of ECM
Collagens - I, II, III, IV
Multi-adhesive glycoproteins - fibronectin, fibrinogen, laminins
Proteoglycans - aggrecan, version, decor, perlecan
What proportion of protein mass does collagen make up
25%
Give an example of how alignment of collagen relate to function
in skin, successive layers arrange at right angles to allow resistance to tensile force in all directions
How many types of collagen are there in humans
28 types with 42 genes
Describe the structure of collagen
3 𝛼 chains in a triple helix
Every 3rd amino acid is a glycine that occupies the interior as it is the only AA small enough
Describe the biosynthesis of collagen
- Synthesis on the RER
- Ribosomes synthesise collagen polypeptides
- Hydroxylation with lysine and proline
- Glycosilation
- 3 chains form the helix
- Release from the cell via a vesicle
What is the purpose of lysine and proline hydroxylation
interchain H-bond formation
When is lysine and proline modified
Synthesis of collagen and in formation of cross-linkages after secretion
What is the function of cross-linkages
Tensile strength and stability
Describe type IV collagen
network-forming collagen
Present in all basement membranes
assembles into a sheet-like network
Describe elastin
Important for elasticity e.g. skin, blood vessels, lungs
Core of elastin and surface microfibrils rich in fibrillin
Why are collagen and elastic fibres interwoven
Limit the extent of stretching
Give an example of a disorder relating to elastin
Marfan’s
Elastic fibres cannot function due to mutations in fibrillar 1
What is a basement membrane
Flexible, thin mat of ECM underlying epithelial sheets and tubes.
Muscle, nerve, fat/
Give an example of a disorder relating to the basement membrane
Alport syndrome
Mutations n gene for type IV collagen
Basal membrane is split and laminated - filtration issues and loss of kidney function
Describe the structure of the basement membrane
Glycoprotein network associated with cells
Constituents - collagen IV and laminins
Describe the structure of multi-adhesive glycoproteins
Large and modular
Multifunctionality due to multiple binding sites for matrix components and receptors
Describe the structure of laminins
𝛼 chain, β chain, 𝛾 chain Very large (160-400 AA) and multi-adhesive
What is the function of laminins
Interacts with receptors such as integrins and dystroglycan
Self-associate with the basement membrane and other components (type IV collagen, proteoglycans)
Give an example of a condition associated with laminins
Congenital muscular dystrophy
or
Epidermolysis bullose
What occurs in congenital muscular dystrophy
Absence of 𝛼2 in laminin 2 Symptoms evident from birth Hypotonia Weakness Deformities of joints
Describe fibronectin
A family of major connective tissue glycoproteins
Insoluble fibrillar matrices or soluble plasma protein
Derived from one gene where different forms arise from splicing or mRNA
Describe the structure of fibronectin
Multi-adhesive Large multi domain molecule open hairpin shape/horeshoe Collagen, integrin and heparin binding sites 50nm
What is the function of fibronectin
Regulating cell adhesion and migration in embryogenesis and tissue repair
wound healing
continuum with actin
What is a proteoglycan
Core protein with one or more glycosaminoglycan chains covalently attached
What is a glycosaminoglycan chain
GAGs are long, unbranched sugars of repeating disaccharides
Which property of GAGs contribute to function
Large volume to mass ratio and the hydrated gel can be very resistant to compression
Give an example of a glycosaminoglycan chain
Perlecan
Aggrecan
Decorin
Syndecans
Describe the structure of a GAG
1 of the 2 sugars is always amino sugar
sulphated or carboxylate -> highly -ve
Describe hyaluronan
Long repeated disaccharide with NO core protein
Unsulphated
Synthesised at the cell surface
Describe decorin
Small proteoglycan
Binds to collagen, essential for fibre formation
What is the cartilage matrix composed of
Type II collagen fibrils embedded in a network of proteoglycans
Describe hyaline cartilage
Abundant type of cartilage found in many places
Cushions ends of long bones
What is hyaline cartilage rich in
Aggrecan
Describe the structure of aggrecan
GAGs are highly sulphated and present in a no. of carboxyl groups -ve charge (sodium attracted) Feather like structure Chondroitin sulfate attachment largest Keratan sulfate attachment Hyaluronan binding region
What is the function of aggrecan and how is structure related
Resistance of compressive forces
-ve charge helps retain water which is lost when compressed but then regained
Give an example of a disease related to proteoglycans
osteoarthritis (aggrecan)
Describe osteoarthritis
excessive loss of ECM so cushioning properties are lost
Cleavage of aggrecan by aggrecanase and metalloproteinase - loss to the synovial fluid
Give an example of a fibrotic disorder
Liver cirrhosis
Excessive production of fibrous connective tissue
What is the proportion of water in human adults
female = 55% male = 60%
What are the proportions of extracellular and intracellular fluids
intra = 55% extra = 45%
How much of fluids does blood plasma make up
7%
How much of fluids does interstitial fluid make up
36%
What are the main cation and anions extracellularly
sodium and chloride (+calcium)
What are the main cation and anions intracellularly
Potassium and phosphate
Is there more protein extracellularly or intracellularly
intracellularly
Define diffusion
Spontaneous movement of solute down its concentration gradients until equilibrium is reached
Define osmosis
Movement of water down its own concentration gradient toward the area of higher osmolarity
Define osmolarity
Osmolarity is a measure of the concentration of all solute particles in a solution
What is the osmolarity of CaCl2
3
Define tonicity
The strength of a solution that takes into account cell permeability
What makes up the university of Wisconsin solution
No sodium or chloride to prevent influx and swelling
extracellular impermeant solutes e.g. raffinose
How do the following pass through the capillary wall: plasma proteins, lipid-soluble substances, small water-soluble substances, exchangeable proteins
plasma proteins = cannot cross
lipid-soluble substances = through the endothelium
small water-soluble substances = pores
Exchangeable proteins = vesicular transport
What is solute and fluid movement across a vessel wall determined by
balance between osmotic pressure (plasma proteins) and hydrostatic pressure (blood)
What is the name given to osmotic pressure due to plasma membranes
colloid osmotic pressure
When does oedema occur
Leakage of plasma into the interstitial exceeds the capacity of the lympahtcis to collect and return it to the circulation so fluid accumulates
Give an example of inflammatory oedema
insect bite causes vessels to become leaky
How does hydrostatic oedema occur
high blood pressure
How may breast cancer treatment cause oedema
Survivors are likely to have the axillary lymph nodes removed which removes the pathway of drainage
Give an example of a disease that associated with oedema
Elephantiasis as parasitic worms block the lymph vessels to prevent lymphatic drainage
