Cells and Tissues Flashcards
Tissue Definition
Groups of similar cells working together to carry out a common function
Organ definition
made
up of several tissue types performing specific set of functions.
(morphologically recognisable structure)
What composes a simple tissue
One cell type
What composes a compound tissue
Multiple cell types
What is a parenchyma tissue
a “working tissue”
What is a stroma tissue
Scaffold and nutrition
What does ECM stand for and what is it
Extracellular matrix, the material between cells.
What is the function of a connective tissue?
protects and supports e.g. fat, blood,
cartilage
What is the function of an epithelial tissue?
covers/lines body surfaces
What is the function of a muscle tissue?
cells contract to generate force
What is the function of a nervous tissue?
generate electrical signals in response
to environment
How are cells anchored to other cells/structure in tissue?
Cell junctions
What is the process of epithelia cancer?
Dedifferentiation (by a mutation), the mutated cell proliferates and expands, invades connective tissue, local invasion (organ), approaches vessels, enters vessels, metastasis
What is metastasis
the
spread of a disease-producing agency (such as cancer cells) from the initial or
primary site of disease to another part of the body
What are the 4 stages of tissue precessing for histology?
Fixation, embedding, sectioning, staining
What is the process of fixation and its purpose
Freezing with dry ice or liquid nitogen to about -80 degrees
Chemical fixation which is aldehyde based (ie, formaldehyde)TO PRESERVE TISSUE
What is the process of embedding and its purpose
Embed the frozen samples in paraffin wax
PROVIDES SUPPORT FOR TISSUE WHEN SECTIONING
What is the process of sectioning
Use a microtome to cut thin sections. (2D representation of 3D object)
the thinner the slice the higher the resolution
What is the purpose of staining
Most cells are colourless and transparent so staining colours the tissue allowing individual components to be identified.
What is the most common stain pair
Stain and counter stain.
Haematoxylin and Eosin (H&E)
How does Haematoxylin dye work
A basic dye and so stains acidic (basophilic) structures purple/blue. e.g. the nucleus
How does eosin work
An acidic dye that stains basic (acidophilic) structures red/pink e.g. the cytoplasm
Explain PAS staining
(periodic-acid/Schiff) staining is for complex carbohydrates and glycogen. Tissues stained with pas are PAS+
e.g. the liver is PAS+ (lots of glycogen), stained magenta
PAS stains mucus, basmement membranes, brush borders (intestines)
Why do lipids appear colourless when stained.
They are optically empty due to being dissolved by the staining process.
Describe electron microscopy
Focused beam of electrons instead of photons, Increases resolution (view smaller structures)
Describe epithelial tissue
Cells in close contact, polarised (sit on BM), not vascularised, covers and protects, combines with Nervous tissue to make special senses, can tighten to prevent toxins entering and water leaving.
What is the function of the basement membrane (BM)
Provides site of attachment for cells and acts as a selective filtration barrier
What is the apex of the cell
Part of the cell that faces outwards.
i.e. in digestive tracts the apex faces into the lumen.
List the 4 types of epithelia
Covering, glandular, exocrine glands, endocrine glands
function of covering epithelia
to cover/line all body surfaces, cavities, tubes
describe the glandular epithelia
secretory epithelium arranged into glands, invaginations of epithelium, also involved in glandular organs
describe exocrine glands
these glands retain continuity woth the surface and so secrete via ducts
describe endocrine glands
these have lost contact with the surface and so secrete directly into the bloodstream
list 3 ways to classify epithelium tissue based on number of layers
simple, stratified, pseudostratified
explain simple epithelia
single layer, good for absobtion and secretion, very fragile
describe stratified epithelia
2 or more layers of same cell shape, good for protection
describe pseudostratified epithelia
one layer with a mixture of cell types. Can appear stratified as nuclei lie at different levels and not all cells reach the surface, BUT one layer as all cells in contact with the BM
list the 4 classifications of epithelium tissue based on shape of cells
squamous, cuboidal, columnar, transitional
describe squamous epithelia
flat shaped, hexagonal cells. fuction: diffusion, filtration, secretion, absorbtion.
little barrier/protection
found in blood vessel lining and heart, alveoli
dexcribe cuboidal epithelium
(stucture, function, and location)
cube-shaped cells, some cells have microvilli.
function: good for diffusion,secretion and absorbtion
found in kidney tubules, glands and their ducts, ovary surfaces
describe columnar epithelium
tall, narrow cells, some have cilia
funtion: movement of substances, absorbtion and sceretion, offer more protection than flatter cells.
found in glands and some ducts, bronchioles of lungs, audiotry tubes.
describe stratified squamous epithelium
(structure, function, and location)
multiple layers of cells that are cube shaped in basal layer and flattened towards the surface.
can be nonkeratinised (moist) or kertanisied (hard)
function: protection against abrasion, barrier against infection, reduction of water loss
location: keratinised - skin (think hard foot soles)
non keratinised - mouth, throat, anus, vagina, cornea
describe kertanised stratified epithelium
the cytoplasm of cells at the surface is replaced by a protein called keratin, these cells are dead.
describe pseudostratified epithelium
(structure, function, and location)
technically a single layer though appears not to be, almost always ciliated and associated with goblet cells.
function: synthesise and scerete mucus, move mucus/fluid that contains foreign particles over the surface.
location: nasal cavity lining, nasal sinuses, audiotry tubes
describe transitional epithelium
(structure, function, and location)
cuboidal/columnar when not stretched, squamous/flattened when stretched. number of layers also decreases when stretched.
function: accomodate fluctuation in the volume of fluid in organs or tubes and protects against the castic effects of urine.
location: lining of bladder, ureters,superior urethra, pelvis of kidney.
Describe a prokaryotic cell
Found in bacetria, do not have a nucleus so the DNA is free in the cytoplasm, often in plasmids
Describe a eukaryotic cell
Human cells, have a nucelus, organised and compartmentalised
Explain the importance of cytochrome C in regards to compartmentalisation
the ETC needs Cc on inner membrane in order to produce ATP. The release of Cc from mitochondria to cytosol initiates apoptosis. Compartmentalisation important so cellular processes occur when supposed to.
Describe the nucleus
Includes nuclear membrane, nuclear lamina, chromatin, nucleolus. It contains genetic material as DNA and produces RNA through transcription.
Describe the plasma membrane
Includes a phospholipid bilayer, cholesterol, carbohydrates, proteins, lipid/membrane rafts.
The plasma membrane regulates what enters and leaves the cell.
Describe the mitochondria
It is further compartmentalised, contains an outer membrane, inner membrane (cristae), intermembrane space and a matrix.
Involved in ATP production (krebs cycle) and apoptosis. (Refer to Cytochrome C)
Describe ribosomes
Made in the nucleolus. Present in the cytoplasm and the rough endoplasmic reticulum. (no difference in the two types). Site of protein synthesis.
Describe the rER
Associated with ribsosomes, protein synthesis, protein folding and protein modifications. The endoplasmic reticulum is a complex set of membranes continuous with the nuclear membrane.
Describe the sER
Has no ribosomes. Involved in lipid synthesis and calcium storage. The ER is a complex set of membranes continuous with the nuclear membrane.
Describe the nucleoli
Dense staining area in the nucleus. Main role is the synthesis if rRNA and the assembly of ribosomes.
Describe the golgi apparatus
Stack of flattened membrane bound sacs (cisternae) and vesicles. Site of post-translational modifications. Recieves proteins from the ER and modifies and sorts them.
Describe lysosomes
They degrade unwanted molecules. Contain approxiamately 50 degradative enzymes (acid hydrolases). Have an optimal pH of 5.
Describe peroxisomes
Membrane bound organelle that performs biochemical reactions. Contains oxidative enxymes like catalase. Breaks down fatty acids by beta oxidation. Produces cholesterol and bile.
What are lamins
Major architectural proteins in the nucleus. Line the inside of the nucelar membrane as a platfrom for binding of proteins.
What are the fucntions of the cytoskeleton
Organise cell structure, maintain cell shape, support plasma membrane, facilitates organelle movement, allows cell to adopt specific behaviours ie growth, division, motility.
What is the purpose of Intermediate Filaments
Mechanical strength, structural
Two examples of intermediate filaments
Keratin in epithelia, lamins in the nucleus
Describe microtubules in cytoskeleton
Polymers of tubulin involved in dynamic processes. Associated wuth dyenin and kinesin (cell movement and transport)
Describe microfilaments in the cytoskeleton
Polymers of actin involved in dynamic processes. Cell projections, contraction/shape change, membrane extension and contractile ring in cytokinesis.
How do cells connect to form tissues
Cell junctions
What are cell junctions
transmembrane protein complexes
What is the function of cell junctions
Connect plasma membrane to adjacent cells or ECM by connecting to the cytoskeleton within the cell
List the types of cell:cell junctions
tight junction, adherens, desmosomes and gap junctions
what are the two cell:ECM junctions
hemi-desmosomes and focal adhesions
Function and example of GAP junction
F: Metabolic and electrical coupling, allows passage of small molecules
E: Electrical properties of cardiac tissue
Function and example of Tight junction
F: Gates & Fences, barrier, selective permeability, cell polarity
E: epithelial cells; distinct apical and basolateral domain
Function and example of adherens junction
F: tissue integrity; contractility and motility
E: links cells to form tissue
fucntion and example of desmosome junction
F: strong adhesion, resist mechanical stress
E: Epidermis (connect cells)
fucntion and example of focal adhesion
F: cell anchorage, mechanical and biochemical signalling
E: cell migration (membrane extension)
function and example of hemidesmosomes
F: cell anchorage
E: Dermal-epidermal junction
How do proteins get to the right place
Proteins are synthesised then dispatched to different locations based on their ‘address labels’ contained in AA sequence.
How do proteins get into organelles?
Nucelar pores, protein translocators (unfold the protein), transport vesicles
Describe phosphorylation
Addition of phosphate group by kinase, alters activity of the protein
Describe acetylation
Addition of acetyle group to histones for example which regulates gene expression
Describe farnesylation
Addition of a farnesyl group which targets proteins to the cytoplasmic face of the plasma membrane
Describe ubiquitination
Addition of a ubiquitin chain which targets proteins for degradation
Describe glycosylation
Addition of a carbohydrate group which helps protein folding in the ER
What post-tranlational modification results in several neurodegenerative disorders
Hyperphosphorylation of the protein Tau
Proteins that are extensively glycosylated are called…
proteoglycans
Proteins with a small sugar component are called…
glycoproteins
3 examples of when proteins must be degraded
When proteins are no longer needed, faulty or foreign.
Two mechanisms of degradation
Lysosomal and proteasomal
Describe lysosomal degradation
Acivated by acidic environment, degrades lipases, nucleases and proteases.
Used for proteins with long half life, membrane proteins, extracellular proteins and pathogenic proteins
Describe proteasomal degradation
P’s are macromolecular complexes within the cytosol. Proteins targeted by ubiquitin labels.
used for proteins with short half lifes, defective and misfolded proteins
3 main fucntions of skin
Protection, regulation and sensation
What are the 5 layers of the epithelium
Basement membrane, basal layer, spinous layer, granular layer, stratum corneum
stratum lucidum in thicker skin, between Sc and SG
Describe the stratum basale
Mitotically active, cells differentiate to form further layers, cuboidal/columnar cells, connected to BM by hemidesmosomes
Describe the stratum spinosum
rich in desmosomes, polyhedral keratinocytes
describe the statum granulosum
cells become flattened, start to lose nucleus and cytoplasm, contain keratohyalin granules
Describe the stratum corneum
large flat plate-like enveloped filled with cross-linked keratin, lipids
Describe the dermis
connective tissue, collagen type 1, elastin and ground substance.
Two layers: papillary and reticular.
Function: immune role, blood supply, tensile strength
describe the subcutis
adipose tissue, connective tissue, fibroblasts, blood vessels and nerves
function:energy source, shock absorbtion and insulation.
describe process of skin regeneration
Stem cells in basal layer divide. On daughter becomes stem cell (constant regeneration) and the other become specialised as a keratinocyte. As further differentiation occurs the cell moves up the layers. By the startum corneum it dies and the skin comes off in desquamation
Difference in skin regen time between homostasis and psoriasis
31 days down to 8 days
Describe eccrine glands
Temperature control through sweat, everywhere except nail beds, lips, external auditory canal and parts of genitalia.
Describe apocrine glands
Scent glands, axillae and genitals
Describe sebaceous glands
Formed from hair follicle, everywhere except palms and soles, enlarge during puberty in response to androgens
Location and function of keratinocyte
Keratinised stratified squamous epithelium, protection and barrier/vitamin D production
Location and function of stem cell
Stratum basale, self renewal and repopulation of epidermal layers
Location and function of Merkel cell
Epidermis (mostly basal layer), sensation
Location and function of langerhans cell
epidermis (mostly stratum spinosum) and upper dermal layer, dendritic cell; antigen presentation and phagocytosis
Location and function of melanocyte
basal layer, protection from radiation
How does the body synthesise vitamin D
UVB converts 7-dehydrocholesterol in the plasma membrane of keratinocytes into previtamin D3
What does chronic exposure of UV to humans lead to
Loss os skin elasticity, abnormal pigmentation, haemorrhage of blood vessels, wrinkles and premature aging
Location and function of keratins
All epidermal layers, major structural proteins; intermediate filaments
Location and function of profilaggrin
Keratohyalin granules, converted to filaggrin which aggregates keratin filaments into tight bundles
Location and function of involucrin
keratohyalin granules, formation of a cell envelope around cells in stratum corneum
Location and function of loricrin
keratohyalin granules, cross-links to involcrin
Location and function of polysaccharides, glycoproteins and lipids
lamellar granules, extrude into intercellular space; form the ‘cement’ that holds together the stratum corneum cells
Location and function of fibroblast
Dermis, synthesis of collagen & elastin/growth factors
Location and function of lymphocytes
dermis, immunosurveillance
Location and function of dermal dendritic cells
dermis, phagocytosis and antigen presentation
Location and function of mast cells
dermis, produce inflammatory mediators; chemotactic factors for eosinophils and neutrophils
Location and function of collagen type 1
dermis, major structural fibrous proteins
Location and function of elastin
dermis, confer elasticity and recoil
Location and function of proteoglycans and glycosaminoglycans
dermis, hydration
What are the 3 stages in wound healing
Inflammation, proliferative and remodelling
Describe the first stage in wound healing
Inflammation: platelets initiate blood clotting (haemostasis), attraction of other cells to the wound, neutrophils and macrophages phagocytose dead tissue and microorganisms. This phase takes 24-48 hours
Describe the second stage in wound healing
Proliferative; re-epithelialisation, cells loosen cell:cell adhesions and migrate to wound. Wound is covered in keratinocytes which then proliferate. Type 3 collagen forms. Then neovascularisation takes place.
What is neovascularisation
Proliferation and migration of endothelial cells
Two methods of keratinocyte migration
Train and leapfrog
Describe the third stage in wound healing
Remodelling; the granulation tissue is replaced from type 3 to type 1. collagen is organised into thick bundles and cross-linked to form a mature scar
What is the function of EGF
Epidermal growth factor signals for re-epithelialisation (keratinocyte proliferation and migration)
What is the function of PDGF
Platelet derived growth factor signals for matrix formation (increased number and activity of fibroblasts) and remodelling (protease production)
What is the function of VEGF
Vascular endothelial growth factor signals for angiogenesis (endothial cell proliferation and migration)
What is the function of Il-1
Interleukin-1 signals for inflammation
What is the function of Il-6
Interleukin-6 signals for inflammation
What is the function of TNF alpha
Tumour necrosis factor alpha signals for inflammation
List 4 local factors affecting wound healing
Infection, foreign body, oxygenation, vascular supply
List 7 systemic factors affecting wound healing
Age, disease, alcohol, smoking, immunocompromised conditions, obesity, medications
When will a cell undergo adaptation
if environmental change (cell stress) is more that what can be dealt with by homeostasis
Definition of neoplasia
Abnormal cell growth (may be cancer)
4 categories of disease
Developmental, inflammatory, neoplastic, degenerative
Fucntion of Involucrin
Formation of a cell envelope around cells in the Stratum Corneum
What is a langerhans cell
Dendritic cell; Antigen presentation and phagocytosis
What is used to replace water in the sample during embedding
Xylene - disolves adipose tissue
What GAGs form Syndecan and where can it be found?
Chondroitin Sulphate, Heparan sulphate - Cartilage
What GAGs form Aggrecan and where can it be found
Chondroitin Sulphate, Keratan sulphate - Cartilage
What GAG forms Perlecan and where can it be found
Heparan sulphate - Basement membrane
What GAGs form Decorin and where can it be found
Chondroitin sulphate, Dermatan sulphate - Connective tissue
What is an adnexal structure
Serve as a reservoir of epithelial cells to repopulate the wound
