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MEDC0004 2025 latest Exam Questions & Answers
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what are the four functions of the kidneys?
- control of salt and water regulation
- maintain acid-base and salt balance - reabsorbs and secretes many electrolytes, salts, amino acids and sugars
- synthesises EPO which stimulates RBC production
- activates vit. D to allow better calcium absorption how do we measure kidney function?
- clearance of urea and creatinine (breakdown product of creatine phosphate in muscle)
- filtration of water and electrolytes
- production of vit. D and electrolytes
- maintaining a healthy filtration barrier what are the symptoms of kidney failure?
- dirty blood
- fluid accumulation
- acidic blood
- high bp
- anaemia
- bone disease
- lipid abnormalities what are the causes of kidney disfunction?
- genetic
- acquired e.g. blood supply, blockage to urine flow, diseases interfering with nephron function (system diseases or kidney specific diseases) what is the treatment for kidney failure
- AKI due to drug toxicity or infection can be reversed by treatment
- immunological diseases are treated with immunosuppressants
- blood pressure control
- dialysis
- transplantation outline kidney perfusion from big to small renal artery > segmental artery > interlobar artery > arcuate artery > interlobular artery how much is filtration per day? ~ 180 L what does mechanisms of autoregulation refer to? Renal blood flow (RBF) autoregulation is a vital homeostatic mechanism that protects the kidney from elevations in arterial pressure that would be transmitted to the glomerular capillaries and cause injury. the afferent arteriole responds to a change in blood pressure, so pressure change isn't transmitted to glomerulus describe myogenic autoregulation 1 increase in blood pressure
how does Ag II override autoregulation? Ag II normally causes efferent constriction RBF decreases but GFR increases when high circulating levels of Ag II, efferent and afferent constrict and RBF and GFR decrease what is renal blood flow ~1200 mL/min What is a podocyte? Epithelial cells surrounding the glomerulus (foot cells) contains podocyte cell body, primary process, filtration slit, secondary process (pedicel) what does a filtration barrier consist of?
- endothelial pores
- glycocalyx of endothelial cells which stops proteins
- basement membrane ( made of proteoglycans)
- filtration slits - connected by slit diaphragm (made of nephrin) what factors affect glomerular filterability
- electrical charge - negative glycoproteins repel negative solutes and attract positive solute
- molecular weight - small solutes enter
what is the net ultrafiltration formula? Puf = (Pgc - Pbs) - pi gc what are the sites of sodium and water reabsorption PCT 50: DLH 20: LOH 15% water only TALH 20% sodium only DCT 5% sodium only CCT 4 sodium: 19 water what are the apical and basolateral membranes? basolateral faces interstitial fluid apical faces lumen (outside world) what reabsorption happens in the PCT reabsorption is isotonic what is renal glucosuria defective glucose uptake in the proximal tubules diabetes mellitus
what does EAST syndrome affect basolateral K+ channel in DCT what is nephrogenic diabetes insipidus cortical collecting duct doesn't respond to ADH stimulation what is central diabetes insipidus low secretion of ADH from the p gland what is kidney autoregulation helps maintain a stable RBF and GFR across a wide range of arterial pressures what reabsorption happens in proximal tubule isotonic reabsorption of glucose, aa, Na+, Cl-, H2O, PO4+ and HCO3- what reabsorption happens in descending LOH equilibration of na+ and H2O what reabsorption happens in loop of henle H2O
what reabsorption happens in TAL Na+, K+ and Cl reabsorption what reabsorption happens in DT Na+ and Cl- reabsorption what reabsorption takes place in collecting duct regulated reabsorption of H2O and NA+ secretion and reabsorption of K+ secretion of H+ why is water balance important
- need enough blood pressure to perfuse vital organs and tissues and this depends on enough circulating blood volume
- need to maintain the concentration of elements (salts, ions etc) both within the cells and surrounding the cells so that they work optimally what are the symptoms of too little water thirst headache nausea cramps dry mucus membranes
units osmol/kg does not depend on temp and pressure where is body water carried 5% vascular space 40% intracellular fluid 15% interstitium how are volume changes detected? baroreceptors in aortic arch and carotid sins it alters vascular tone and cardiac output how are osmolarity changes detected osmoreceptors in hypothalamus present with thirst and vasopressin release how are pressure changes detected JG cells in kidneys renin-aldosterone and angiotensin salt and water reabsorption
what determines intracellular osmotic pressure K+ what determines extracellular osmotic pressure Na+ what determines water distribution between vascular and extracellular compartments plasma oncotic pressure - osmotic pressure exerted by plasma proteins that cannot freely move across capillary walls balance between hydrostatic pressure pushing fluid out of capillary and oncotic pressure pulling fluid in describe neural regulation of blood pressure
- baroreceptors detect changes in arterial pressure
- signals are sent to the medulla of brain stem
- vagus nerve adjusts heart rate
- sympathetic nerves adjust cardiac contractility and peripheral resistance What is ANP? atrial natriuretic peptide
how do clearance values change
- if substance undergoes net reabsorption, clearance will be less than that of inulin
- if not freely filtered, clearance will be less than inulin
- if solute undergoes net secretion, clearance will be greater than that of inulin inulin vs creatine clearance inulin:
- polysaccharide of fructose must be infused intravenously
- freely filtered, not reabsorbed, not secreted
- continual blood and urine sampling required
- chemical analysis is cumbersome creatine:
- endogenous
- released in blood at constant rate
- plasma conc is fairly stable so only need one blood sample
- freely filtered, not reabsorbed, some secretion what is the equation for volume of plasma cleared (PAH) cPAH = uPAH * V / pPAH = RPF how to convert RPF to RBF RBF = RPF/(1-Hc)
factors affecting plasma creatine levels
- muscle mass/ usage
- age
- gender - male > female
- ethnicity
- diet (low protein) = drugs what is uraemia a clinical syndrome with various symptoms that arise as a result of progressive kidney failure associated with multiple biochemical and physiological abnormalities examples of uraemic toxins
- small water soluble eg urea
- small lipid soluble or protein bound eg phenols
- larger middle molecles eg beta 2 microglobulin - take longer to accumulate to lethal dose p - cresyl sulphate and indoxyl sulphate protein bound so not easily removed by dialysis levels increase in patients with CKD proinflammatory effects absorption inhibited by AST- 120
is CO2 a volatile or fixed acid? volatile vs sulphate is not volatile and it is excreted by the kidneys how oxygen is transferred between cell and Hb?
- CO2 forms carbonic acid in Hb
- protons are released
- oxyhaemoglobin exchanges its oxygen for a proton
- oxygen diffuses back to cells
- cell releases CO2 into extraceullular fluid
- protein spreads throughout the body so spreads the effects of H+
- eventually buffering molecules get swamped so dont work anymore What is respiratory acidosis and examples? insufficient removal of CO2 eg inadequate breathing or CO2 in the air. Rise in plasma CO increases production of carbonic acid and therefore more H+ and more bicarbonate ACUTE
- decreased CNS stimulation: sedative drugs
- neuromuscular ventilation failure
- structural/mechanical ventilation failure
- airway obstruction: acute asthma, inhaled foreign object CHRONIC
- decreased CNS stimulation: sedative drugs
- neuromuscular ventilatory failure
- structural/mechanical ventilatory failure: severe obesity, thoracic deformity
- chronic airway obstruction: trachea stenosis, COPD what is metabolic acidosis? caused by excess production of non volatile acids eg voluntary ingestion of methanol or loss of base from the gut as in diarrhoea. Fall in plasma pH and fall in bicarbonate what is respiratory alkalosis? caused by excess removal of CO2 such as hyperventilation or high ventilation. Fall in plasma CO2 decreases production of carbonic acid and therefore less H+ and less bicarbonate ACUTE
- increased CNS stimulation: anxiety/psychiatric causes, drugs (aspirin)
- subarachnoid haemorrhage
- mechanical over-ventilation of intubated patient CHRONIC
- increased CNS stimulation: stroke
- increased hypoxic drive eg high altitude what is metabolic alkalosis? excess of non volatile bases eg after vomiting increase in bicarbonate
- Toluene (glue)
- alkaline urine - failure of acid secretion in urine
- metabolic acidosis
- osteomalacia - buffer effect from bone phosphate > loss of bone minerals
- hypercaulcuiria = increased Ca2+ in urine
- kidney stones and nephrocalcinosis (Calcification of kidney)
- hypokalaemia = K+ to balance what is type 2 RTA? failure of PCT cells - bicarbonate is not reabsorbed
- causes mild metabolic alkalosis fanconi syndrome: found in urine...
- phosphate
- urate
- glucose
- amino acids
- low molecular weight proteins causes:
- acetozalamide/topirimate (CA inhibitors)
- myeloma (too many antibodies cannot exit kidney)
- tenofir for Hep B and AIDS
- tubulointerstitial nephritis
what is type 3 RTA? mixed distal and proximal RTA
- carbonic anhydrase 2 mutations What is Type 4 RTA? hypoaldosteronism high aldosterone - hypokalaemia and metabolic alkalosis (increased bicarbonate reabsorption) low aldosterone: hyperkalaemia metabolic alkalosis in patients with:
- diabetes and CKD
- NSAIDs
- calcineurin inhibitors (immunosupressants)
- heparin
- primary adrenal insufficiency what are the symptoms of acidosis? headache sleepiness confusion loss of consiousness coma shortness of breath
