Cells and Tissues Flashcards
Which germ layer do mesenchymal tissue arise from?
Mesoderm
What tissues are included in the term mesenchymal tissues?
Blood, Lymph, Fat, Cartilage, Muscle, Bone
What are the 2 main components of connective tissue?
Cells and ECM
What makes up the extracellular matrix?
Ground substance containing glycosaminoglycans (structural carbohydrates), glycoproteins and proteins, through this runs collagen fibres (Strength) and elastin fibres (elasticity) also contains percolating tissue fluid
What cells are found within the ECM in connective tissue>
1) Fibroblasts (active during healing, make collagen, elastin and glycosaminoglycans)
2) Adipocytes (Store fat)
3) Immune cells: Macrophages, mast cells (produce vasoactive substances) and Plasma cells
What are mononuclear leucocytes and name one?
No lobed nuclei, include lymphocytes (B and T cells)
What are granulocytes and name some?
Have lobed nuclei and granules in cytoplasm, include neutrophils, eosinophils, basophils
Other than leucocytes what are the other components of blood?
Erythrocytes, platelets, Proteins (including immunoglobulins, albumin and fribrinogen), hormones, nutrients, gases and plasma
What might occur if lymph nodes are removed?
Lymphodema because lymph cannot be removed from tissues
What are the cells found in the ECM (called osteoid) of bone?
1) Osteoblasts: make osteoid
2) Osteocytes: found in mature bone, osteoblasts which have become trapped once bone calcifies and now maintain bone
3) Osteoclasts
What are the cells found in the ECM (called osteoid) of bone?
1) Osteoblasts: make osteoid (collagen fibres are found within it)
2) Osteocytes: found in mature bone, osteoblasts which have become trapped once bone calcifies and now maintain bone
3) Osteoclasts: resorb bone (break it down) in response to stress on bone, growth, calcium status
How is bone formed?
First bone formed by osteoblasts is woven and immature, collagen fibres are random, as immature bone is calcified (initiated by osteoblasts) bone becomes harder and woven bone is replaced by lamellae bone where collagen fibres are in parallel layers
What is compact and cancellous bone?
Compact outer bone, shafts of long bones,
Cancellous (spongy) inner bone, found at end of long bones
What is periosteum and endosteum?
Periosteum = dense fibrous layer on outside of bone Endiosteum = tissue lining inner bone
What are the functions of cartilage?
1) form a supporting framework for organs
2) form articulating surfaces for bone
3) form a template for development and growth of long bones
What are the constituents of cartilage?
1) ECM made up of ground substance and collagen fibres
2) Cells including chondroblasts (make ECM and collagen fibres) and chondrocytes (mature chondroblasts trapped in collagen)
What are the 3 types of cartilage and where are they found?
1) Hyaline: glossy, nose trachea
2) Fibrocartilage: intervertebral discs, pubic symphysis
3) Elastic cartilage: found in ears
What is Marfan’s syndrome?
Defect in fibrillin protein, joint laxity, cataracts, valvular heart disease, aortic wall weak
What is scurvy?
connective tissue disorder that results from ascorbic acid deficiency
What role does histology have in medicine?
Diagnosis of cancer and many non malignant diseases, identifying prognostic features, therapeutic information can be gained from histology and special stains can identify the presence of drug targets within tissues
In histology what is the purpose of fixation?
Prevent degradation of tissues either by bacteria, autolytic enzymes or trauma, heat or chemicals may be used, achieved by forming covalent bonds within proteins or venturing proteins
What is formalin?
Most common Fixative in histology, forms covalent bonds between proteins
In histology what are the pros and cons of formalin?
Reliable, penetrates tissue well but its toxic/an irritant and not good for cytoplasmic structures but good for overall morphology
In histology what are the pros and cons of the Fixative glutaraldehyde?
Good for cytoplasmic structures and used for electron microscopy but doesn’t penetrate tissue well so only small pieces can be fixed
In histology what are the pros and cons of the Fixative ethanol?
Good nuclei acid preservation but useless for morphology
In histology what are the pros and cons of fixing with freezing?
Good for nucleic acids and proteins, morphology isn’t great and need a large freezer
In histology what is block selection?
Selecting blocks of interest, specimen is cut using bread slicing and cross sections examined, small blocks of interest are then cut out and placed in a cassette
In histology how are blocks of interest processed into wax?
Impregnation of tissue in wax gives the tissue sufficient rigidity for sectioning, wax is not water or formation soluble but is soluble in xylene (benzene based hydrocarbon which is missable with alcohol). Cassettes soaked in alcohol, then xylene, then melted wax then cooled and allowed to set
In histology what is sectioning?
Solid wax block is cut into 5 micron sections which are picked up on glass slides
In histology why do sections need to be stained?
Until stained sections are translucent and nothing could be seen down a microscope so contrast must be added
What is the common histochemical stain H and E?
Haemotoxylin and Rosin. H is basic and stains acidic material purple eg. Nuclei acids. E is acid so stains basic material pink eg. Cytoplasmic proteins.
In histology what are the pros and cons of the histochemical stain H and E?
Good robust stain for demonstrating overall anatomy but certain things eg. Fat aren’t stained and you can’t tell the difference between 2 basic things
In histology what are the pros and cons of the histochemical stain H and E?
Good robust stain for demonstrating overall anatomy but certain things eg. Fat aren’t stained and you can’t tell the difference between 2 basic things
What is masons trichrome and what is it used to stain?
Connective tissue stain, haematoxylin, acid fuschin and methyl blue, highlights collagen so is useful to highlight how much fibrosis there is within a section
In histology what is Periodic Acid-Schiff (Disease) stain and what is it used for?
Stains mucin but also stains glycogen so diastase enzyme is used first to get rid of glycogen - some tumours characterised by the presence of mucin in their cytoplasm so PAS-D is used to highlight this, it also highlights fungi
In histology what is Perl’s Prussian blue used for?
Histochemical stain used to highlight iron
In histology what is Orcein stain used for?
Histochemical stain used in liver pathology (highlights elastic fibres, hep B virus and copper associated protein)
In histology what is Oil Red ‘O’ used for?
Histochemical stain used to stain fat
What is immunohistochemistry?
The use of anti bodies to highlight specific molecules within a cell (immunohistochemical stains)
What is the rough process used in immunohistochemistry?
1) Isolate Ag
2) Ag given to rabbit which forms an Ab against it
3) Ab applied to section and binds to Ag if present
4) Second Ab to rabbit Ab is added which has a label attached which is visible by light microscopy
What is the rough process used in immunohistochemistry?
1) Isolate Ag
2) Ag given to rabbit which forms an Ab against it
3) Ab applied to section and binds to Ag if present
4) Second Ab to rabbit Ab is added which has a label attached which is visible by light microscopy
What embryological germ layers are epithelia derived from?
All 3 germ layers but there are subtle differences in the epithelial derived from the ectoderm (skin), mesoderm (vascular endothelium) and endoderm (GI tract)
What are the main characteristics of epithelial?
1) Polar (have a top and a bottom, a feature essential to their secretory and absorptive functions)
2) Avascular (although they are innervated) and rely on diffusion from underlying capillary beds
3) Remarkable regenerative ability, proliferate more than other tissues and can promptly replace surface cells lost through apoptosis, natural shredding or injury
What are the 5 main functions of epithelial?
1) Physical protection
2) Control of transcellular transport
3) Movement
4) Sensation
5) Secretion
How is epithelia adapted to the function of physical protection?
Provide a continuous covering of body surface
Can be multi-layered or keratinised to provide extra strength
If a monolayer, highly replicative to replace sloughed/injured cells
Impermeable to prevent toxin reabsorption
What are the 5 main types of attachments/junctions between epithelial cells?
1) Tight junctions
2) Adherents junctions
3) Gap junctions
4) Desmosomes
5) Hemi Desmosomes/focal adhesion
In the epithelia what are tight junctions?
Occlusion/Claudine form seals to protein movement and paracellular diffusion, apically located
In the epithelial what are adheren’s junctions?
Transmembrane proteins connect across cell cytoskeletons, found below tight junctions
In the epithelia what are gap junctions?
Small channels which allow intercellular ion/small molecule exchange between cells but also contribute to adhesion
In the epithelia what are Desmosomes?
Transmembrane proteins (linked to intermediate filaments) connect to others from adjacent cells
In the epithelia what are hemi Desmosomes/focal adhesions?
Provide attachment to the underlying basal lamina
How is epithelia adapted to its function of controlling transcellular transport?
functional complexes stop paracellular transport, ensures epithelial can help to maintain homeostasis by controlling what enters and leaves the body through selective absorption
Cell polarity determines the direction of the various transcellular transport systems
How is the epithelia adapted to its function of movement?
Presence of cilia - coordinated
How is the epithelia adapted to its function of movement?
Presence of cilia - coordinated activity ensures unidirectional flow, participates in mucho culinary escalator in respiratory system, in fallopian tube ensures oocyte movement towards there uterus
How is the epithelia adapted to its function of sensation?
Sensory epithelial comprises sensory cells (which convert external stimuli into electrical impulses) and supporting cells.
How is the epithelia adapted to its function of secretion?
Many epithelia contain there own secretory cells (Eg. Goblet cells) sometimes epithelia are organised into specialised, fully developed multicellular glands, which may (exocrine) or may not (endocrine) have an associated secretory ducal system
What are the 3 types of exocrine gland according to mode of secretion?
1) Merocrine - vacuole based exocytosis (salivary glands, pancreas)
2) Apocrine - Material accumulates at apex of cell which is then pinched off (lactating breast)
3) Holocrine - secretions accumulate in the cytoplasm of the cell but the entire cell is released and disintegrates to release its contents (sebaceous glands of skin)
In exocrine glands what is meant by simple or compound gland?
Simple gland - The ductal component does not branch
Compound gland - The ductal component does branch
In exocrine glands what is meant by tubular or alveolar (Acinar) glands?
Tubular - The secretory portion of the gland is tubular (could be coiled)
Acinar - The secretory portion of the gland has a sac like termini
What are endocrine glands?
Glands that release secretions into the blood stream normally to act on distant target tissues or organs. Endocrine glands tend to have an intimate relationship with their surrounding vascular system
Name some endocrine glands?
1) Pituitary gland
2) Ovaries and testes
3) Corpus luteum (only has a brief existence but secretes progesterone)
4) Pancreas (also has exocrine function too)
What is meant by squamous epithelium?
Flattened cells eg. skin
What is meant by cuboidal epithelium?
Squarish cells usually lining small ducts and tubules
What is meant by columnar epithelium?
Tall cells usually with a basal nucleus
What is meant by Simple epithelium?
Monolayer
What is meant by stratified epithelium?
Several cell layers thick (can be keratinised)
What is meant by pseudostratified epithelium?
Looks stratified but isn’t - all cells make contact with the basal membrane
What is meant by transitional epithelium?
Stratified but appearance changes with stretch
What is meant by pseudo stratified epithelium?
Looks stratified but isn’t - all cells make contact with the basal membrane
What is epidermolysis bullosa?
Collection of genetic disorders with mutations in the genes coding for the proteins involved in maintaining epithelial cohesion, all present with the formation of painful busters following minimal trauma to the skin, some variants also have internal organ involvement.
What is epidermolysis bullosa simplex?
congenital, affects the skin, problem with keratin, affects keratin intermediate filament assembly, causes bullae (blisters) in areas stress
What is junctional epidermolysis bullosa?
Affects the basement membrane and is the most severe kind
What is dystrophic epidermolysis bullosa?
Affects the dermis (So no epithelial)
What is the basic pathology in cystic fibrosis?
- Faulty CFTR Transmembrane channel results in chloride ions being retained within the cell (where they normally would be able to get out)
- This draws sodium into the cell to balance the Transmembrane charges and water follows by osmosis, thus dehydrating secretions
- The situation is reversed in sweat glands where the failure to reabsorb chlorine accounts for the salty sweat characteristic of the disease
What is the affect of CF on the airways and heart?
Impaired mucociliary escalator, recurrent respiratory infections and chronic inflammation which in time causes bronchiectasis, pulmonary hypertension and consequent heart failure.
Recurrent sinusitis and inflammation can lead to the formation of sinonasal polyps which exacerbate breathing difficulties
What is the effect of CF on the GI system?
Meconium ileus, pancreatitis and progressive fibrosis, malabsorption, CF related diabetes, billiard cirrhosis (secondary to bile duct plugging) can lead to portal hypertension and steatorrhoea.
What is the effect of CF on fertility?
Males are infertile, can get amenorrhea in women which is thought to contribute to reduced fertility
What are the 2 common techniques for diagnosing cystic fibrosis?
1) Sweat testing
2) Genetic testing
In terms of cancer what is dedifferentiation of cells?
cells stop having their intended function and are less identifiable as cells of that tissue
What is the course of a carcinoma?
1) Normal epithelial cells
2) Hyper proliferative cells - uncontrolled cell division
3) Early adenoma
4) Late adenoma
5) Carcinoma - cancer moves into tissues
What is a carcinoma and why is it more common than a sarcoma?
Carcinoma is a cancer that begins in skin or epithelial cells - common because epithelial cells are more proliferative so more prone to mutation
What is a sarcoma?
begins in bone, cartilage, muscle, fat, blood vessels or other connective tissue
What is leukaemia?
Cancer that starts in the blood forming tissues such as the bone marrow and causes large numbers of abnormal blood cells to be produced and enter the blood
What are lymphoma and myeloma?
Cancers that begin in cells of the immune system
Name a type of cancer which doesn’t develop tumour?
Leukaemia
In terms of cancer what is a foci formation?
Cancer cells have a loss of ‘contact inhibited cell division’, when grown in a peri deism cancer cells pile up and form what is known as a foci formation. But, when normal cells divide once they cover a surface and are in contact they send signals to each other to prevent further cell division
Why are cancer cells referred to as ‘immortal’?
Healthy cells reach a point where they stop growing and die, cancer cells don’t, they have lost the ordinary process of eventually dying off under normal conditions
What percentage of cancers do inherited pre dispositions account for?
5%
What are Li Fraumeni syndrome and xeroderma pigmentosum?
Inherited cancer syndromes in which people are more prone to developing cancer
What is one of the biggest risk factors for developing cancer?
AGE
Which cancer is caused by the Hep B virus?
Liver cancer
Which cancer is caused by the human papilloma virus?
Cervical cancer
Which cancer is caused by H.Pylori?
Stomach cancer
Which cancer is the chemical carcinogen ‘heterocyclic amines in meat cooked @ high temperatures’ related to?
Colon cancer
Which commonly known chemical carcinogen is bladder cancer related to?
Cigarette smoke
Which cancer is UV in sunlight related to?
Skin cancer
Which cancer are x rays and gamma rays related to?
Leukaemia, having radiotherapy increases your chance of developing leukaemia
What is the difference between melanoma and non melanoma skin cancer?
Melanoma skin cancer - cancer of melanocytes - pigment cells of the skin and is more dangerous
non melanoma skin cancer is more common
What is the biochemistry of UV rays causing skin cancer?
UV-B rays cause direct DNA damage
1) Input of energy from UV light causes the formation of covalent bonds between 2 adjacent thymine residues to form a thymine dimer
2) When DNA comes to replicate its difficult to copy the thymine dimer
3) Do possess DNA repair proteins which normally repair this - although not always
How does the chemical carcinogen Benzo[a]pyrene in cigarette smoke cause lung cancer?
Benzo[a]pyrene binds to deoxyguanosine (guanine base in DNA) to form a DNA adduct, DNA polymerase can’t recognise the base (guanine), mutations are more likely to occur during replication if they occur in a gene controlling cell division then get cancer
When a chemical enters a cell why do enzymes add different atoms/molecules to it and why is this a problem in the case of carcinogens?
Add them to make the chemical more polar so it is more soluble and more easily excreted, in the case of carcinogens this makes them more reactive so the carcinogen can now covalently bind to the DNA
What is aflatoxin?
A toxic metabolite which is metabolised in the liver and produced by a fungus which grows on crops such as maize and peanuts, grows during storage particularly in warm humid climates.
What is the link between aflatoxin and liver cancer?
Human hepatocellular carcinoma
1) aflatoxin metabollised in the liver to produce a reactive intermediate
2) Reactive intermediate forms a DNA adduct which leads to a mutation (presence of an adduct means a mutation is more likely to occur)
3) Mutation in a gene controlling cell division = liver cancer
What is the difference between a case control study and a prospective study?
1) Case control studies - compare disease groups with matched control groups to look for factors more common in people with the disease
2) Prospective studies - follow a population over time to confirm that this disease is linked to the suspected cause
In cancer epidemiology why must case control or prospective studies be carried out?
To look for an association between an exposure and cancer
In case control studies how is an odds ratio calculated?
(expected/unexpected) -> (no. exposed cases x non exposed controls) / (no. non exposed cases x exposed controls)
What does the odds ratio define in terms of case control studies?
relative risk of developing cancer if you were exposed to a carcinogen as opposed to if you weren’t - eg. could be 10 x more likely
In cancer epidemiology what is a cohort study?
Healthy people are recruited and followed over time, data collected about exposure is later used to establish if a relationship between exposure and cancer exists
What are the advantages and disadvantages of cohort studies compared to case studies?
Cohort studies takes more time however its considered a better and more reliable study as there is much less chance of bias - eg. in a case control study you may accidentally select an unrepresentative control group to try and show the association
Give an example of observational data that could be gathered before carrying out a case or cohort study into a carcinogen?
Trends of disease over time or geographical incidences of a disease
How can polymorphisms in enzymes alter the outcome of an exposure to a carcinogen?
Poly morphisms in enzymes involved in metabolism (Detoxification of carcinogens) and repair (by removal of adducts) can influence DNA adduct levels and thus the risk of mutation. eg. in the enzyme that metabolises benzo[a]pyrene there are 2 polymorphisms, 1 gives rapid action to a reactive intermediate and 1 give slow activation. Homozygous rapid is the most dangerous
What is harlequin ichthyosis?
Congenital, problem with keratin, get hyperkeratinisation, skin gets stiff and cracks so get a loss of physical barrier, dehydration, poor thermoregulation and sepsis, frequently fatal
What is epithelial basement membrane dystrophy?
To do with basement membrane adhesion, abnormal basement adhesion complexes, to do with the eyes, get recurrent corneal erosions, scar tissue forms and you get visual disturbances
What is autosomal PKD?
Congenital, mutations affecting Ca2+ transport, abnormal amount of Ca2+
What is autosomal PKD?
Congenital, affects transport proteins, mutations affecting Ca2+ transport, abnormal amount of Ca2+ - get renal tubule epithelial proliferation, tubes get blocked cysts form - parenchymal (functional part of kidney) compression - renal failure
What is kartageners syndrome?
congenital, affects the cilia, to do with the cilia moving in the wrong direction, chronic sinusitis, bronchiectasis and sub fertility (cilia can’t push hormones etc. in the right direction)
