Session 3 - Filtration Flashcards Preview

Semester 3 - Urinary > Session 3 - Filtration > Flashcards

Flashcards in Session 3 - Filtration Deck (95)
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Outline the sequence of arteries leading into the kidney

• Renal Artery -> Segmental Arteries -> Interlobar Arteries -> Arcuate Arteries -> Interlobular Arteries -> Afferent Arterioles


Give one way in which the structure of the renal arteries increases pressure in the glomerulus

• The diameter of each afferent arteriole is slightly greater than the diameter of the associated efferent arteriole


What is the size limit and effective molecular radius for filtration?

• Size limit - 5,200
• Effective molecular radius - 1.48 nm


Why are proteins not usually filtered into the kidney?

• Size
• Basement membrane and podocyte glycocalyx have many negatively charged glycoproteins which repel protein movement


How much blood is filtered by the renal artery at any one time?

• 20%


What happens to blood not filtered by the glomerulus?

• Exits via efferent arteriole


What are the two types of kidney nephron?

• Cortical
• Juxtamedullary


Why is a juxtamedullary nephron named thus?

• Glomeruli located in cortex, but next to medullary bounds


Give two differences between cortical and juxtamedullary nephrons

• Juxtamedullary has longer loops of henle
• Arrangement of peritubular capillaries around cortical nephrons messy
• Structured and organised arrangement of capillaries in juxtamedullary nephron
• Countercurrent flow in organised juxtamedullary nephron


How is filtration a selective process?

• Cells and large proteins do not get filtered through
• Water, salts and small molecules pass through
• Thanks to filtration mesh provided by podocytes


Where do the glomerula tufts always lie?

• In the cortex


Where does blood to be filtered arrive in the kidney?

• Glomerula tuft


What are the three layers in the filtration barrier?

• Capillary endothelium
○ Water, salts, glucose
• Basement membrane
○ Acellular gelatinous layer of collagen/glycoprotein
○ Permeable to small proteins
○ -'ve charge to repel protein movement
• Podocyte layer
○ Pseudopods interdigitate and form filtration slits


It is more difficult for a positive protein to pass through membrane than a negative. Do you agree?

• No, negative repelled by -vely charged basement membrane


What happens if a clinical conditions results in negative proteins being stripped of their charge?

• They will be filtered and appear in the urine


Give conc of following in plasma and ultrafiltrate

• Glucose 100
• Na+ mmol/l 140
• Urea mg/dl 15
• Creatinine umol/l 60-120


Give three physical forces involved in plasma filtration

• Hydrostatic pressure in the capillary (regulated) (capillary -> tubule)
• Hydrostatic pressure in bowman's capsule (tubule -> capillary)
• Osmotic (oncotic) pressure differences between the capillary and tubular (tubular -> Capillary)


What is the net filtration pressure in the glomerulosa?

• 10mmHg


What is the average hydrostatic pressure between capillaries and tubule?

• 50mmHG (about half of normal pressure)


What is the effect of charge on filtration?

• Neutral molecule - The bigger it is, the less likely to get through
• Anions - Negative charge also repels, more difficult to get through
• Cations - Positive charge allows slightly bigger molecules through


How is blood in afferent arteriole (going out) different to efferent (going in)?

• Oncotic (protein) pressure higher
• Blood is more concentrated


Give one cause of proteinuria involving filtration forces

• In many disease processes the negative charge is lost on the filtration barrier, so proteins are more readily filtered


What is osmotic pressure?

• Force generated because of solute within solvent


What is oncotic pressure?

• Oncotic force in generated because of protein within solute


Why is absorption in kidney called reabsorption?

• Already been absorbed once by GI tract


Give three mechanisms by which reabsorption occurs

• Osmosis
• Diffusion
• Active transport


What is tubular secretion?

• Substances secreted into renal tubular lumen from peritubular capillaries


By what mechanism are substances secreted into the tubular lumen?

• Active transport


What two main types of substances are secreted into the tubular lumen?

• Those present in great excess
• Natural poisons


What does secretion help to maintain?

• Blood pH