Week 1 Flashcards
=What are the three main functions of skin and examples?
What is peripheral circulation?
Transport of blood around the body allowing the exchange of nutrients in tissues
Label this diagram:
What is the function of the arrector pili?
Connected to hair follicle, when contracted causes hair to stand on end creating goosebumps
What is the eccrine gland?
Major sweat gland abundant in palms and soles.
What is the dermal papilla of the hair follicle?
Main source of blood for hair follicle, delivers oxygen/nutrients
What is the hair follicle composed of?
Several layers of epithelial cells
Four layers of the epidermis?
Stratum basale, spinosum, granulosum and corneum.
What is the basement membrane composed of?
Extracellular matrix proteins.
S+F of stratum basale?
Cuboidal, mitotically active stem cells that regenerate other layers of epidermis.
Structure of stratum spinosum?
Layer of keratinocytes rich in desmosomes giving spiny appearance.
S+F of stratum granulosum?
Flattened cells contain keratohyalin granules which aggregate keratin filaments
Structure of stratum corneum?
Flattened cells that have lost their nuclei with keratin and lipids.
Function of lipids in epidermis?
Act as water barrier
Where is stratum lucidum found?
Only in thick skin e.g. soles of feet
How often is skin shed?
1x month
How is each layer of epidermis formed?
Daughter cells from basal layer migrate upwards and differentiate to form each layer
What changes in each layer of epidermis?
Type and amount of keratin produced
How many keratin types are there?
30
What is the structure of the dermis?
Connective tissue, fibroblasts and immune cells
What is connective tissue made up of?
Collagen type I, elastin and ground substance
Function of fibroblasts?
Produce collagen and elastin
What fibres allow stretch and what fibres allow tensile strength?
Stretch: elastin
Tensile: collagen
What are the structures of the two dermal layers?
Papillary: thinner and looser, fine collagen fibres, most blood vessels and nerves
Reticular: thicker stronger fibres
Functions of dermo-epidermal junction?
- attachment of epidermis to dermis
- aligns cells of epidermis
- base for re-epithelialization in wound healing
- barrier function to and from epidermis
Structure and function of subcutis?
Adipose tissue
Energy source, shock absorption, insulation
Function and location of meissner’s corpuscles?
Mechanoreceptors for touch, papillary dermis of hands and feet
Function and location of Pacinian corpuscles?
Detect deep pressure and vibration, subcutis
What are adnexal structures?
Hair, nails, glands
What are eccrine glands, location?
Sweat glands, everywhere except nails/lips
What are apocrine glands, location?
Scent glands, axillae and genitals
What are sebaceous glands, location?
Produce sebum, everywhere except palms/soles
What type of epthelium is the epidermis?
Stratified squamous keratinised
Function of keratinocytes?
Protection/barrier against foreign substances, vit D production
Function/location of merkel cell?
Strat basale, sensation
Function/location of langerhans cell?
Epidermis, denditic cell (antigen presentation/phagocytosis)
How do langerhans cell long processes aid function?
Help detect foreign antigens
Function of melanocyte?
Protects from radiation
Results of chronic UV exposure?
Loss of skin elasticity/fragility
Abnormal pigmentation
Wrinkles
How does melanocytes work with keratinocytes to protect cells from UV damage?
Melanin is transferred into keratinocytes via cytoplasmic processes and protects nucleus from UV damafe
What are three keratohyalin granules?
Profillagrin, involucrin, loricrin
Function of profilaggrin?
Converted to filaggrin which aggregates keratin into tight bundles
Function of involucrin?
Forms cell envelope around corneum cells
Function of loricrin?
Cross links to involucrin
Function of lymphocytes?
Immunosurveillance
Function of mast cells?
Produce inflammatory mediators e.g. histamine and chemotactic factors
Which molecules hydrate the dermis?
Proteoglycans, glycosaminoglycans
What is a wound?
Breakdown in protective function of the skin, loss of epithlium continuity with/without loss of underlying connective tissue
What is an erosion injury?
Only epidermis lost
What is an ulceration injury?
Structures deep to epidermis
What is a partial thickness injury?
Epidermis and some dermis
What is a full thickness wound?
Epidermis, dermis and deeper structuresm only wound edge cells left
What cells are involved in wound healing?
Inflammatory cells, keratinocytes are replaced, fibroblasts, endothelial cells for angiogenesis
How long is each phase of wound healing?
Inflammation: 24-48 hrs
Proliferative: 4-21 days
Remodelling: several months
What happens in the inflammatory phase?
Platelets initiate hemostasis/blood clot and healing cascade and attract neutrophils/macrophages to site
Function of neutrophils/macrophages in wound healing?
Phagocytsoe dead tissue and microorganisms
What happens in proliferative phase?
What cells are involved in the proliferative pgase?
Keratinocytes: reepithelialsation
Fibroblasts: ecm formation
Endothelial cells: angiogenesis
2 methods of keratinocyte migration?
What happens in the remodelling phase?
Granulation tissue become mature scar tissue, collagen cross linked to form mature scar, switch from type III to type I collagen
Function of epidermal growth factor signal?
Re-epithelialisation (keratinocyte proliferation and migration)
Function of platelet derived growth factor signal?
Matrix formation (inc number and activiy of fibroblasts)
Function of vascular endothelial growth factor signal?
Angiogenesis (endothelial cell proliferation and migration)
What 3 molecules signal inflammation?
IL-1, IL-6, TNF
Local factors affecting wound healing?
Infection, foreign body, oxygenation, vascular supply
Systemic factors affecting wound healing?
Age, disease, alcohol/smoking, obesity, medication
What is the definition of cells?
Basic structural and functional unit of all living organisms
What are the three points of cell theory?
- all living things are composed of one/more cells
- cells are basic unit of life
- new cells arise from pre-existing cells
What is cytosol?
Intracellular fluid of cytoplasm
What is tissue defined as?
Groups of similar cells working together to carry out common function
What is parenchyma?
Working tissue
What is stroma?
Scaffold and nutritional tissue
What is an organ defined as?
Several tissue types comprised in morphologically recognizable structure performing specific set of functions
What is tissue composed of?
cells +ECM
Four types of tissue and function?
Connective: supports and protects e.g. fat, blood
Epithelial: covers/lines body surfaces
Muscle: cells contract to generate force
Nervous: generate electrical signals in response to environment
Four stages of tissue processing?
Fixation, embedding, sectioning, staining
How are tissues fixated and why?
Freezing with dry ice/nitorgen or chemically with aldehyde
Preserves the tissue
How are tissues embedded and why?
Frozen samples or paraffin wax
Provides support when sectioning
How are tissues sectioned?
Microtome
What type of dye is haemotoxylin?
Basic so stains negatively charged structure bluish purple e.g. nucleus
What type of dye is eosin?
Acidic so stains positively charged structures reddish pink e.g. cytopkasm
What is PAS stain used for?
Staining complex carbohydrates and glycogen e.g. mucus, basement membranes, brush borders of intestines
How do lipids stain?
Optically empty
Why is electron microscopy used over light microscopy sometimes?
Electron microscopy is used to see very small structures and has increased resolution
Functions of epithelial tissue?
Covers and protects body surfaces
Lines internal cavities, blood vessels, respiratory and reproductive organs
Function of covering epithelia?
Covers/lines all body surfaces, cavities, tubes
Function of glandular epithelia?
Secretory epithelial
Produces and releases secretory products: sweat, saliva, mucus, digestive enzymes, hormones etc.
How do exocrine glands secrete?
Via duct, retain continuity w/ surface
How do endocrine glands secrete?
Into bloodstream, lose contact with surface
Where is simple squamous epithelia found? Function?
Blood vessel/heart lining
Alveoli
Lining of kidney tubules
For diffusion/filtration
Location/function of simple cuboidal epithelium?
Kidney tubules, glands, terminal bronchiole lining
Diffusion/secretion
Location/function of simple columnar epithelium?
Glands, bronchioles, auditory tubes, uterus, stomach
Movement of substances, absoprtion
Function/location of stratified squamous epithelium?
Structure/function/location of pseudostratified epithelium?
Structure/function/location of transitional epithelium?
What are intracellular processes?
Processes that take place within a cell
What are two strategies to segregate molecules?
Multicomponent complexes e.g. ribosome
Compartmentalization into organelles
What are organelles?
Cellular subunit performing specific function in cell
Where are proteins synthesised?
In cytosol on ribosomes
What is ribosome composed of?
Proteins and rRNA , two subunits
What is svedberg?
Non-linear measurement measuring sedimentation rate (how quickly it will settle at the bottom after centrifugation)
Why is ribosome main antibiotic target of bacterial cell?
It is larger than human ribosome so easy target: bacteria will die if it cannot make more proteins
3 methods of proteins imported into organelles?
Nuclear pores: selective gates for nuclear proteins
Protein translocators: for proteins moving from cytosol to ER, mitochondria, peroxisomes
Transport vesicles: for proteins moving from ER onwards
How do ribosomes know to go to the ER?
signal peptide on protein being made
What is a signal peptide?
Specific sequence on N-terminal amino acid.
How is the signal peptide guided to the ER?
Signal recognition particle in cytosol binds to signal peptide
What do vesicles that carry proeteins from ER to golgi become?
Fuse to become cis cisterna
What happens as proteins move through golgi stack?
Undergo enzymatic modification
Function of phosphorylation?
Alters activity of protein
Function of acetylation?
Regulates gene expression in histones
Function of farnelysation?
Targets proteins to cytoplasmic face of plasma membrane
Function of ubiquitination?
Targets protein for degregation
When is protein degregation required?
Faulty proteins, proteins past sell by date, foregn proteins
Two methods of protein degradation?
Lysosomal degradation
Proteasomal degradation
What are the two outcomes for transport vesicles in golgi apparatus?
Exocytosis: vesicles from ER fuse with plasma membrane
Endocytosis: mannose-6-phosphate address label targets them to become endosome then matures to lysosome
What is lysosomal degregation carried out by and activated by?
Lysosomal enzymes e.g. lipases/proteases
Lysosomal acidic environment
When is lysosomal degregation used?
Proteins with long half life >20 hrs
Mmebrane proteins
Where does proteasomal degregation happen? Dependent on?
In cytosol at proteasomes
ATP
What is proteasomal degregation used for?
Proteins with short half life
What is the nuclear lamina?
Strong Mesh that supports nuclear membrane
- organises nucleus and chromatin
What is chromatin?
DNA combined with histone proteins
What is the nucleoleus function?
Site of rRNA and ribosome synthesis
Which things can you view under a light microscope?
Eukaryotes, bacteria, organelles
Which things can you view only under electron microscope?
Virus, proteins lipids
Which organeles are not membrane bound?
Ribosomes
Size of prokaryotic vs eukaryotic cells?
Pro: 1-10 microns
Eukaryote: 5-100 microns
Organelle definition?
Subcellular structures that carry out different functions
Where are nuclear pores found, function?
Nuclear membrane
Allows certain molecules to pass through
Nucleus functions?
Chromosomes replicated
Genetic information found
Dna transcribed into RNA
Function of plasma membrane?
Regulates what moves in and out of cell
Detects signals from outside of cells
Function of cholesterol in plasma membrane?
Maintains fluidity of membrane
Function of carbohydrates in plasma membrane?
Stabikises membrane and maintains fluidity
Function of lipid rafts in plasma membrane?
Cholesterol rich
Concentrate proteins and signalling receptors for specific functions
Where are proteins for energy production found in mitochondria?
Genome
What is the structure and function of the inner membrane of mitochondria
Cristae: invaginate cell to increase surface area
Function of mitochondria?
ATP production and apoptosis
Which 3 ways does mitochondria produce ATP?
- krebs cycle
- electron transport chain
- oxidative phosphorylation
Which molecules does the electron transport chain require?
Cytochrome c
How is apoptosis initiated in the mitochondria?
cytochrome c is released from mitochondria into cytosol
Functions of RER?
- protein synthesis
- protein folding
- protein modifications
Functions of SER?
- lipid synthesis
- ca storage
Structure + Function of lysosomes?
- degrade unwanted molecules
50 degregative enzymes - acid hydrolyses
pH 5
Structure + Function of peroxisomes?
- membrane bound organelle
- biochemical reactions
- oxidative enzymes e.g. catalase
- breakdown fatty acids
Examples of reasons to localise different functions of the cell?
cytochrome c in mitochondira
lysosome degregation
peroxisome
Glycocalyx structure and function ?
-layer of carbohydrate covering cells
- cell recognition
- prominent in gut
Which molecules determine ABO blood grouping?
carbohydrates
Four compartments of mitochondria?
Outer membrane
Inner membrane
Matrix
Intermembrane space
Function of mitochondria outer membrane?
selective permeability
Function of mitochondria inner membrane ?
Electron transport chain
Function of mitochondria matrix?
Enzymes for citric acid cycle
Function of mitochondria inter membrane space?
location of cytochrome c
Functions of the cytoskeleton?
Organises cell structure
Maintains cell shape
Supports plasma membrane
Allows organelle movement
Allows growth, division, motility
Three types of cytoskeleton?
- microtubules
- microfilaments
- intermediate filaments
Function of intermediate filaments?
Provide strength and structure in a cell
Examples of intermediate filaments?
Keratin in skin epithelial cells
Vimentin in fibroblasts
Lamins in nuclei of eukaryotes
Structure + Functions of microtubules?
Constantly assembling and disassembling
A and b tubulin
Cell movement, intracellular organelle transport, mitotic spindle
How do microtubules move organelles intracellularly ?
Kinesins: move cargo away from centrosome
Dyneins: move cargo towards centrosome
Structure and Function of axonomes?
Microtubule and dynein composition
Cytoskeletal component of cilia and flagella
Allow bending
Composition of microfilaments?
polymers of actin
Functions of microfilaments?
Cell projections: microvilli, stereocillia
Cytoplasm: cell contraction, shape change
Membrane extensions for motility: lamellopodia, filopodia
Contractile ring: cytokenesis
Functions of cell junctions?
Connect plasma membrane to adjacent cells, basement membrane, cytoskeleton of other cell
Functions of anchoring junctions?
Anchor cells to other cells or the ECM
Which junctions are cell-cell junctions?
Adherens, desmosomes
Which type of cytoskeleton is adherens and focal adhesions?
actin
Which junctions are cell-ecm junctions?
Focal adhesions, hemidesmosomes
Which type of cytoskeleton is desmosomes and hemidesmosomes?
intermediate filaments
Function of gate in tight junction?
Regulates paracellular permeability (what can enter cell)
Function of fence in tight junction?
Forms apical and basolateral inter membrane diffusion barrier
Which type of junction is paracellular?
tight
Function of GAP junctions?
Allows passage of small molcules
Structure of GAP junctions? Where are they found?
cell-cell contact
hexamers and connexins
cardiac tissue
Which structures are composed from microtubules?
Flagella and cillia
Function of hepatocytes?
Liver cells
Lipid biosynthesis
Location and function of leydig cells?
Testes
Steroid hormone biosynthesis
Which molecule do muscle cells rely on?
Calcium
What is epidermolysis bullosa?
Defects in hemidesmosome
Causes fragile skin
Skin blistering, tearing upon touch
What is kartegeners syndrome?
Defective cilia - effects mucus clearance, circulation of CSF and fertility as sperm aren’t motile
How are microtubules stabilised?
Presence of proteins tat bind to them
Effect of Tau protein not being present in microtubules?
Alzheimers
Microtubules dissassemble
What is tay-sacks disease?
Mutation in genes that encode lysosomal enzymes
Genetic
build up of gangliosides in brain and spinal cord
Where is E-cadherin found?
Adherens junction
What happens when adherens junctions are defective?
Cancer as E-cadherin is lost so carcinomas can metastasise
Function of tight junctions and where are they found?
barrier - selectively permeable, cell polarity
epidermis
What are tight junctions composed of?
Claudins
What are adherens junctions composed of?
cadherins
What are desmosomes composed of?
desmosomal cadherins
What are focal adhesions and hemidesmsomes composed of?
integrins
What cytoskeleton does focal adhesions have?
actin