Pre-clinical SAQs (Foundation topics) Flashcards
young girl, PMH of long bone fractures, resulting from minor injuries.
sclerae appears blue, skin is hyperextensible and she has difficulty hearing.
patient most likely has
- osteogenesis imperfecta
- type 1 collagen defect
effect of dietary deficiency of vitamin C on collagen
- ascorbic acid required as a co-factor
- required for hydroxylation of amino acids in collagen (proline and lysine)
- hydroxylation allows increased hydrogen bonding
- to stabilise triple helix
- lack of vitamin C –> weak tropocollagen triple helices –> scurvy
how might you screen for CF?
- newborn screening via immunoreactive trypsinogen
- The concentration of IRT is elevated in babies with CF since pancreatic ducts are partially blocked leading to abnormal enzyme drainage.
penetrance
proportion of individuals carrying a particular variant of a gene that also expresses an associated phenotype
CF briefly caused by
- autosomal recessive
- CFTR mutation on chromosome 7
Duchennes muscular dystrophy is inherited as
X-linked recessive
skeletal muscle
- striated
- peripheral located nuclei
- multi-nucleated
- voluntary
smooth muscle
- non-striated
- centrally located nuclei
- spindle shaped cells
- involuntary
Smooth criminal in central station ;)
cardiac muscle
- striated
- centrally located nuclei
- branching cells
markers of muscle cell damage
- myoglobin
- troponin
- AST
Duchenne muscular dystrophin
no dystrophin protein produced,
dystrophin needed for sarcolemma stability
progressive proximal muscular dystrophy
distinctive psuedohypetrophy of calves
Beckers muscular dystrophy
abnormal dystrophin produced
which cells form collagen in cartilage
chondrocytes
factors that cause a right shift of the oxygen dissociation curve
- increased temp
- decreased pH
- increased 2,3 DPG
60 y/o male, sudden dysponea, pleuritic chest pain. D-Dimer elevated. resp rate 32. BP 95/60mmHg
pulmonary embolism
summarise 4 neurological cells in brain
- astrocytes
- oligodendrocytes (myelin sheath in CNS)
- microglial cells (scavenger cells that remove cellular debris from sites of injury)
- ependymal cells (production of CSF)
by which process is bone formed directly without using cartilage as a template?
- intramembranous ossification
- process uses mesenchymal tissue in development of long bones
endochondral ossifcation
- uses hyaline cartilage
- as a model for formation of long bones
goblet cells are what type of epithelium
simple columnar epithelium
what type of epithelium is found in areas that are highly secretive or absorptive
simple columnar epithelium
what epithelium is found is larger respiratory airways of the nasal cavity, trachea and bronchi
psuedostratified epithelium
transitional epithelium is found in
tissues that stretch
like the lining of bladder and urethra
which cells secrete glycosaminoglycans to protect the bronchiole lining?
- clara cells
- found in ciliated simple epithelium
how does alcohol cause hypoglycaemia?
- excess alcohol intake leads to increase in ratio of NADH:NAD+
- build up of NADH inhibits gluconeogenesis
- leading to hypoglycaemia
why is bicarbonate low in patients with diabetic ketoacidosis?
- compensatory reaction
- bicarb is used up to react with ketoacids to achieve normal pH
why does diabetic ketoacidosis commonly occur as a result of:
- insulin deficiency
- excess stress hormone release
- absence of insulin results in decreased glucose uptake peripherally by muscle and fat
- excess stress hormone causes mobilisation of free fatty acids from fat cells
two clinical features associated with Cushings
- hypernatraemia
- hypokalaemia
why does diabetes result in polyuria?
- excess glucose filtered out
- glucose in urine
- glucose draws in water via osmosis
type 1 diabetes
autoimmune destruction of beta cells in the islet of langerhans
type 2 diabetes
reduced insulin secretion and/or increased insulin resistance
45 y/o female, increased sweating and palpitations. los 2kg in past six months. appears agitated, non tender mass on anterior aspect of neck.
bloods show:
high free T3
high T4
low TSH
Grave’s disease
- hyperparathyroidism
IgG autoantibodies bind and activate G protein coupled thyrotrophin receptors.
40 y/o woman presents with fever and dysphagia, examination reveals tender and enlarged thyroid, blood tests reveal raised T3 and T4 with decreased TSH. has previous viral infection
likely cause of her presentation
De Quervain’s thyroiditis
- commonly occurs post viral infection
23 y/o female presents to clinic complaining of shortness of breath, palpitations/ she is disproportionately tall and thin with long arms and legs compared to her trunk.
on auscultation you hear a systolic murmur
which protein is affected in this underlying condition
Marfan’s syndrome
autosomal dominant
mutations in FBN1 gene that encodes fibrillin 1
58 y/o woman presents with fatigue, feeling cold, with constipation and weight gain. on examination you notice her skin is dry, she has a pulse rate of 45 bpm. thyroid is firm and enlarged.
what test might you do to confirm diagnosis
- hypothyroidism
- usually elevated TSH and low T4
- thus measurement of TSH levels
how does chronic alcoholism lead to chronic liver cirrhosis?
- damage to hepatocytes
- releasing reactive oxygen species
- inducing activation of hepatic stellate cells
- subsequent liver injury
- causes apoptosis of hepatocytes
- leads to tissue inflammation, fibrogenesis and cirrhosis
35 y/o female with muscle weakness, double vision, drooping of eye, weakness being worse during exertion but improves with rest.
pathophysiology behind condition
- Myasthenia Gravis
- autoimmune
- antibodies to nicotinic acetylcholine receptors at junction between the nerve and muscle
Phase 1 metabolism
- involves modification that can be via oxidation, reduction or hydrolysis
Phase 2 metabolism
- involves conjugation making the metabolite more water soluble
- therefore facilitating excretion
Barret’s oesophagus is an example of
metaplasia
granuloma
- consists of epitheloid macrophages
- which fuse together
- to form a giant cell
MHC class II molecules present antigen to ….
helper CD4+ cells
MHC class I molecules present antigen to ….
cytotoxic CD8+ cells
briefly describe the allergic response
- extrinsic allergen causes a TH2 response
- causes B cells to produce IgE antibodies (priming)
- IgE antibodies bind to receptors on surface of mast cells (mast cells now sensitised)
- re-exposure to allergen (elicitation) causes IgE to trigger release of mediators
- ————> histamine
- ————> prostaglandins - mediators cause
- ———–> vasodilation
- ———–> smooth muscle contraction
why are adrenaline and corticosteroids given in anaphylactic reactions?
- Adrenaline
- –> constriction of resistant arterioles on alpha-1 receptors
- –> increases BP and relaxes airways via beta-2 receptors - corticosteroids
- –> suppress allergic immune/inflammatory effect
Type 4 hypersensitivity involves
T cells
in viral infection, which cells are responsible for antigen recognition and how are the antigens generated within a cell?
Cytotoxic T cells
- antigens are degraded into peptides within the cell
- displayed at surface of the cell with MHC class I
- which are recognised by CD8+ T cell
opsonins
molecule that enhances phagocytosis by binding to another molecule
