block one- tissues Flashcards
what is the concept of the dynamic cell
cells are dynamic, constantly moving and adapting to carry out functions
describe the lipid distribution in the plasma membrane
- composed of a lipid bilayer interspersed with proteins making it dynamic and fluid instead of rigid
- most of the PC and all of the glycolipids are found in the external (extracellular) half of the bilayer
- most of the PS, PE, and PI are in the internal (cytoplasmic) half of the bilayer
- cholestrol is distributed evenly between the two halves
the permeability of the plasma membrane
- gases such as oxygen and carbon dioxide can diffuse freely across the membrane
- ions and large uncharged polar molecules cannot pass freely, they require specific protein channels or transporters
the roles of the membrane proteins
transporters and channels = move molecules across the membrane
anchors = hold components close to the membrane
receptors = detect and transmit signals from the environment
describe the mechanism of glucose uptake in the gut
- sodium potassium pump -> maintains a low sodium concentration by pumping sodium out of the cell
- sodium-glucose co-transporter -> uses the sodium gradient to transport glucose from the gut lumen into the cell
- basolateral transport -> glucose exits the cell into the bloodstream via facilitated diffusion through specific transporter proteins
what are the differences between the apical and basal membrane?
apical membrane = faces the gut lumen and contains more sodium-glucose transporters (contains more clusters)
basal membrane = faces the tissue and facilitates glucose export into the blood
explain the mechanisms of protein transport
- proteins have specific destinations within the cell
- a short amino acid sequence at the beginning of a precursor protein determines it’s destination
- proteins are imported into the mitochondria, via specialized translocases. They unfold, cross the mitochondrial membranes, and refold in the matrix.
describe the steps of ER transport within protein production?
- signal recognition particle(SRP): recognizes the signal sequence on the protein and binds to it.
- SRP receptor: anchors the SRP protein complex to the ER membrane
- translocator: opens to allow the protein to pass into the ER lumen
the role of vesicle transport in the protein transport system
- vesicles bud off from one membrane and fuse with another moving proteins between different compartments of the cell
- key for secreting proteins and delivering them to their final destination
describe how botox works?
- blocks acetylcholine release by cleaving SNARE proteins
- this prevents muscle contraction
- the transport vesicle docks with v-SNARES attatched to it
- the t-SNARES which are attatched to the target membrane interact with v-SNARES to bring protein close to membrane
- membranes of protein and the target combine
- the lipid bilayers fuse
- the v and t SNARE proteins are now left joined together
- botox cleaves these snare proteins
what does SNARE stand for?
= soluble NSF attatchement protein receptor
name the main functions and components of the cytoskeleton
function:
- cell shape
- mechanical support for the cell and tissues
- cellular locomotion (cells change morphology)
- intracellular movements of cytoplasm, organelles and chromosomes
main components:
- microfilaments (actin) = smallest, mobility (5nm)
- microtubules = largest, transport (~25nm)
- intermediate filaments= strength and stability (15nm)
describe the role of actin withi neurons
microfilaments = form dense network near neuronal membranes, giving shape and motility to neuron
neurofilaments(intermediate) = provide strength and stability, absent in the axon terminals
what controls microtubule organisation and describe
microtubules + and - ends/ MTOC/ centrosome
= MTOC (microtubule organizing centre)
- microtubules grow from MTOC and control the number, position and orientation of them.
- in animal cells the main MTOC = centrosome, located at a side of the cell nucleus
- microtubule can have growth at the positive end by addition of alpha / beta tubulin
- prevention of growth at negative end by y tubulin ring complexes
- microtubules can be located in the cilia
describe the action of kinesins and dyneins in intracellular transport
motor proteins:
kinesins: move cargo along microtubules towards the + end using their head groups
dyneins: move cargo along microtubules towards the - end using their head groups
- the proteins they transport may be enzymes, receptors, NT…
what do lysosomes do?
they contain enzymes that break down waste
what do capping proteins do
Regulate actin growth by blocking polymerization at one end.
the normal action of acetylcholine
- Acetylcholine does not go through ER and Golgi apparatus
- Acetylcholine is released from nerve cells at the neuromuscular junction
via calcium mediated exocytosis - Acetylcholine binds to receptors on skeletal muscle to cause contraction
what are the 4 main types of tissue and what is their fucntion?
- connective tissue:
role= Packaging or supporting fabric
examples= tendons, blood, cartiliage - nervous tissue
role = communication via nerve and glial cells
examples= brain, spinal cord, nerves - muscle tissue
role= forces generation to produce movement
types= smooth, cardiac, skeletal - epithelia
role= Covers body surfaces
what is the role of epithelia and describe its features?
role = covers and protects body surfaces, forms barriers and glandular structures, lines internal cavities and vessels, creates a tight cohesive sheet
describe the characteristics of epithelia
- highly cellular tissue
- avascular (no blood vessels)
- capable of regeneration
- polar
- derived from all three germinal layers (ectoderm, endoderm, mesoderm)
describe what the three surfaces of epithelial are
free apical surface:
- is exposed to the external environment as it is on the top of the cell
- is not attatched to other cells
- often lines lumen of ducts and cavities
lateral surface:
- attatched to other epithelial cells(junctions)
basal surface:
- attached to basement membrane which attaches epithelia to underlying tissues
- each surface can have its own specialisations
what are the specialisations of the apical surface?
- microvilli
- increases surface area
- often on epithelia that lines internal passages - stereocilia (longer than microvilli, but similar):
- limited distribution
- non motile
- found in male reproductive system and hair cells in inner ear - cilia:
- beats in co-ordination to move substances over them
- found in respiratory epithelium and fallopian tubes
- many per cell
what are the specialisations of the basolateral?
- here epithelial cells are cohesive and closely apposed
- specialisations of junctions:
- join cells together
- exchange information
- maintain polarised state
- anchor everything together
what are the three types of junctions and describe their role?
- occluding/ tight junctions:
- prevents leaking by sealing cells together
- prevents unwanted substances from entering an area - anchoring junctions:
- attaches cells to neighbours
- abundant in tissue subject to severe stress eg skin - communicating/gap junctions:
- passes chemical or electrical signals between cells
- cell communcation
what are the functions of epithelial cells?
- protection of underlying structures
- passage of substances
- acts as a barrier to substances
- secretion
- provides sensory supply
- permeability regulation
the 3 types of layers when identifying epithelial
- Simple:
single layer, good for absorption/secretion,
fragile- Stratified:
2 or more layers of cells, good for protection - Pseudostratified: one layer of mixture of cell shapes
- Stratified:
the three shapes of epithelial
- Squamous: flat shaped
- Cuboidal: cube shaped
- Columnar: tall cylindrical shaped
- Transitional: readily change shape, accommodates stretching
describe the structure, function and location of simple squamous epithelial
structure = flat, single layer with a flat nucleus and hexagonal shaped cells
function= diffusion, filtration, absorption
location= lining of blood vessels, aveoli
describe the structure, function and location of simple cuboidal epithelial
structure= cube shaped, may have microvilli or cilia, more structural protection
function = secretion, absorption, diffusion
location = kidney tubules, glands, lining of lungs
describe the structure, function and location of simple columnar epithelial
structure= tall, narrow cells, may have cilia or microvilli, nucleus further down towards basement membrane
function= secretion, absorption, protection, movement of substances
location = glands, ducts, stomach
describe the structure, function and location of stratified squamous epithelial
structure= multiple layers, that are cubed shaped in basal layer and become flatter towards the apical surface, can be keratinized or nonkeratinized
function= protection, barrier from infection, reduction of water loss
location= skin(keratinized/dry)
mouth, anus (nonkeratinized/moist)
describe the structure, function and location of stratified cuboidal epithelial
structure = multiple layers of cubed shaped cells
function = secretion, absorption, protection
location= swear gland ducts, salivary gland ducts
describe the structure, function and location of stratified columnar epithelial
structure = tall cells on cubed shaped layers
function= protection, secretion
location= mammary ducts, larynx
describe the structure, function and location of pseudostatified columnar epithelial
structure= appears stratified but only one layer, nucleu appear at different levels, often ciliated
function= mucus synthesis, secretion and movement
location = lining of nasal cavity, pharynx, trachea
describe the structure, function and location of transitional epithelium
is a type of stratified
structure = changes between cuboidal(stretched) and squamous(relaxed)
function = accomodates flucuations in volume of fluid in organs or tubes
location= ureters, lining of urinary bladder
- number of layers depends on how stretched it is (less whren stretched)
what are the three main classes of connective tissue
- connective proper tissue
- supporting connective tissue
- fluid connective tissue
what are the functions of connective tissue?
- connection
- tendons connect bone to muscle
- ligaments connect bone to bone - support
- bones and cartaliage provide structural support - enclosure/ protection
- capsules around organs, bones protect vital structures - separation
- sheaths separate muscles from each other - cushioning/insulation
- Adipose tissue absorbs shocks and retains heat. - storage
- adipose tissue stores energy - transportation
- blood(fluid connective tissue) transports oxygen
what is the first major component of connective tissue?
cells
- resident cells= create, maintain or breakdown the ECM
- blasts= create the ECM
- cytes= maintain the ECM
- clasts= breakdown the ECM
other cells which the connective tissue houses:
adipose, mast, macrophages, white blood cells, lymphocytes, undifferentiated mesenchymal stem cells
what is the second major component of connective tissue?
ECM(extracellular matrix)
- is made up of ground substance and extracellular protein fibres
- ground substance
- gel like fluid that fills the space between cells that contains ->
cell adhesion proteins: connective tissue glue such as fibronectin and osteonectin
** proteoglycans: **
- macromolecule with a protein core which GAGs are attached
- the higher the GAG content, the more viscous the fluid is - fibres
- provide support (3 types)
- collagen fibres = most abundant, created by fibroblasts, are strong and rope like, (Type 1 in tendons, ligaments, type II in cartiliage, type III are reticular fibres)
- elastic fibres = long, thin, stretchable, found in lungs and blood vessel wall, secreted by fibroblasts
-** reticular fibres**= thin, short branching networks supporting organs like liver and spleen.
describe connective tissue proper
a connective tissue classification type
- loose
= fewer fibres, more ground substance
- areolar, adipose and reticular - dense
= more fibres, less ground substance
regular -> organized fibres eg tendons
irregular -> randomly arranged fibres
- regular collagenous, regular elastic, irregular collagenous, irregular elastic
name the components of supporting connective tissue
a connective tissue classification type
- cartiliage
-hyaline
- fibrocartiliage
- elastic - bone
- spongy
- compact
name the components of fluid connective tissue
a connective tissue classification type
- blood
- red cells
- white cells
- platelets - haemopoietic
- red marrow
- yellow marrow
describe 4 connective tissue disorders
- Scurvy
- defective collagen fibres
- vitamin C deficiency leads to unstable collagen
- symptoms: surface bleeding such as gums - Marfans syndrome (defective elastin fibres)
- Mutation in Fibrillin-1 causes weak elastic fibres.
Symptoms: Long limbs, dilated arteries. - pulmonary emphysema( elastic fibre destruction)
- increase in elastase activity destroys elastic tissue
- causes-> smoking, air pollution
- can cause the bronchioles to collapse and ifficulty breathing - fibrosis (scar tissue formation)
- Excess fibrous tissue disrupts normal organ function.
- scars cause tissues to harden reducing fluid flow through affected tissues
describe the function, types, treatments and diseases of bone marrow
function
= produces blood cells (red, white, platelets and lymphocytes)
types:
Red Marrow: Found in skull, ribs, vertebrae, long bones (active in blood production).
Yellow Marrow: Stores fat, inactive in blood production.
diseases:
Leukaemia: Overproduction of immature WBCs.
Lymphoma: Abnormal lymphocytes.
Myeloma: Abnormal plasma cells.
treatments:
Radiotherapy, chemotherapy, bone marrow transplant.
outline the anatomical organisation of the nervous system
- CNS
- brain
- spinal cord - PNS
- cranial nerves
- spinal nerves
outline the cells of the nervous tissue
- neurones
- nerve cells -> functional unit of NS, sends signals around the body - glial cells -> support cells -> protect, provide nutrients and immune functions to the neurons
describe the properties of neurons
4
- irritability -> ability to respond to signals
- conductivity -> conduct electrical signals along cell membrane
- longevity -> neurons last a lifetime and are difficult to replace
- high metabolic rate -> require a constant suply of glucose and oxygen
describe the structure of a neuron
- dendrites
- highly branched, receives signals from synapses
- contains organelles such as nissl bodies and mitochondria - cell body (soma)
- Contains central nucleus and organelles.
- Nissl Bodies: Ribosome clusters indicating high protein production.
- Cytoskeleton: Neurofibrils (microtubules and filaments) for stability and transport.
- No Centrioles: Neurons cannot divide (amitotic). - axon (distributor)
- Long, cylindrical structure conducting action potentials.
- May have branches (axon collaterals which are bigger and terminal branches with are smaller).
- Contains mitochondria and cytoskeletal proteins.
outline th overall function of glial cells(neuroglia)
- Smaller, more numerous than neurons.
- Supportive and protective roles; no action potential conduction.
- Capable of division and multiplication.
name the glial cells part of the CNS and PNS
1.CNS
- astrocytes
- microglia
- ependymal cells
- oligodendrocytes
- PNS
- satellite cells
- shwann cells
astrocytes
CNS
star shaped cells that:
- maintain chemical environment and blood brain barrier
- Guide neuronal growth and repair damaged tissue.
- Recycle neurotransmitters and form scar tissue after brain injury
- provides nutrients to neurons
microglia
CNS
- small cells involved in CNS protection by phagocytosis of pathogens and microbes
- clears away the debris of dead cells
Ependymal cells
CNS
- lines brain ventricles and spinal cord central canal
- produces and circulates CSF
- selectively permeable for exchange of nutrients and waste
what is cerebrospinal fluid and what does it do?
A. Substance derived from blood that contains nutrients such as oxygen, ions and glucose to nourish the brain while protecting it from toxins
Can also protect the rest of the body from escaped neurotransmitters
oligodendrocytes
CNS
- Provide structural support.
- Form myelin sheath around multiple CNS axons.
- named because of thei dendrite like processes
- not limited to one axon
schwann cells
PNS
- Wraps around single axonal segments in the PNS to form myelin sheath.
- Essential for repair and electrical insulation - makes up white matter(axons).
satellite cells
PNS
- flattened cells around cell bodies of neurons
- regulate the chemical environment and assist in repair
desribe two disorders of the nervous system
- tumours
- Commonly gliomas (from glial cells as they regenerate).
- Symptoms vary depending on location, size, and growth rate. - demyelination
- Damage or loss of myelin sheaths disrupts electrical conduction.
- Can result in neurological deficits, including paralysis.
eg MS, Guillain Barre Syndrome
relation of nervous tissue to disorders
- High dependency on metabolic supply makes neurons vulnerable to oxygen/glucose deprivation.
- Non-regenerative properties (amitotic nature) complicate repair.
- Glial cell proliferation often leads to scar tissue or tumour formation.
describe the functions of muscle tissue
- movement
- posture and joint stability
- protein supply
- regulation of organ volume
- propelling of fluids and food
- heat generation
describe the properties of muscle tissue
- tightly packed and well vascularised
- excitability -> ability to respond to stimuli
- contractility -> generate force( not always shortening)
- extensibility -> can stretch without tearing
- elasticity -> can stretch and return to original shape
- has a close relationship with surrounding connective tissue
- Describe cardiac muscle cell and its different features
- located in the heart
- large fibre diameter of 10-20um
- small fibre length of 50-100um
- branched, cylindrical shape (allows cells to connect to each other)
- has one centrally located nucleus
-intercalated discs (joining points between adjacent cells)
striated
describe smooth muscle cells and their features
- located in the walls of viscera(internal organs), blood vessels and skin
-small fibre diamter of 3-8um - medium fibre length of 30-200um
- fusiform shape( looks like flat oval)
- one central nucleus
- non- striated
describe skeletal muscle cells and their features
- mainly attached to bone
- very large fibre diameter 10-100um
- very large fibre length 100um-30cm
- long, cylindrical shape
- many peripherally located nuclei
- striated
how is skeletal muscle stimulated to contract
- via the neuromuscular junction (NMJ) -> where the neuron meets the muscle
- voluntary control with the exception of some
reflexes
what are the functions of the fascia and where is it found
- surrounds muscle
- connects muscle to surrounding tissue allowing it to pull on it and contract
- separates individual muscles
- prevents overextension
- attaches or stabilises muscle
describe the layers of skeletal muscle and the structure
layers:
epimysium = outer connective tissue
fascicile= bundle of muscle fibres that is surrounded by perimysium
perimysium = surrounds fasicles
endomysium = inner connective tissue
structure of myofibrils:
muscle fibres/myofibril (individual muscle cells)
-> many peripheral nuclei, contain abundant mitochondria, and sarcoplasmic reticulum which stores calcium.
Sarcomeres: Functional unit of contraction (thin/light filaments, thick/dark filaments
cylindical, striations seen here
Sarcolemma:
cell membrane of muscle cell
how do cardiac muscle cells contract
- Autorhythmic pacemaker
- speed and strength of contractions regulated by hormones and neurotransmitters.
how do smooth muscle cells contract
- Autorhythmic in some areas (e.g., GI tract); regulated by the autonomic nervous system (ANS) and endocrine system
- controlled by hormones and neurotransmitters.
describe the diseases of muscle
- myopathy: abnormal disease of muscle tissue
- dystrophy: progressive degeneration of fibres caused by disease eg Duchenne’s
- neuromuscular disease: affecting motor units (neuron, fibre, NMJ)
- metabolic myopathies: Defects in ATP metabolism (e.g., glycogen storage diseases, mitochondrial myopathies).
can cause fatigue, cramps and pains - inflammatory myopathies: Chronic inflammation; autoimmune in origin.
How do cardiac muscle cells communicate for coordinated contraction?
Via intercalated discs, which connect cells and allow electrical signals to pass between them.
