Flashcards in Renal structure and function Deck (101)
How is the ultrafiltrate produced by the glomerulus?
- Efferent arteriole thinner than afferent = pressure gradient
- Ultrafiltrate from capillaries between afferent and efferent
- Podocytes around capillaries prevent passage of proteins
- Fenestrated lining of capillaries
- Negative change of basement membrane
Why is the basement membrane of the glomerulus negatively charged?
- Made up of acellular glycocalyx
- Thick (physical barrier)
- Negative charge (repels anions)
What components of blood can pass thorugh the glomerular barriers easily?
- Micromolecules i.e.:
- Amino acids
- Small hormones
What components are not contained within the normal ultrafiltrate?
- Macromolecules i.e.:
How do podocytes aid the production of the ultrafiltrate?
- Make up inner epithelial layer of Bowman's capsule
- Have pedicels with gaps
- Final barrier
What components are reabsorbed from teh ultrafiltrate in the tubule?
- Plasma proteins if present
- Amino acids
- Urea (partially)
What is filtration dependent on?
- Molecular weight
- Small molecules less than MW 700 Daltons filtered witout restriction
- Medium: MW 17000 Daltons filtered less
- Large: MW 70000 Daltons restricted completely
What is meant by glomerular filtration rate?
- Volume of fluid filtered per unit time
- Measure of kidney function
- Is scaled to bodyweight (thus affected by lean mass)
Where does the majority of the reabsorption of the ultrafiltrate occur and why?
- Proximal tubule
- Is structurally and functionally organised for bulk reabsorption
- Outer cortex
- Cortex receives most blood flow
- Involves cortical glomeruli
What proprtion of glucose and amino acids is reabsorbed from teh ultrafiltrate?
Describe the process of ultrafiltrate reabsorption
- Coupled to movement of Na+ ions
- Generally iso-osmotic
- Filtered proteins reabsorbed
- Waste products retained in tubule to be excreted
- Primary and secondary active transport
How are proteins reabsorbed from the ultrafiltrate?
Endocytosis via recetpros megalin and cubulin)
Decribe primary active transport in ultrafiltrate reabsorption
- Directly uses ATP
- ATP to transport Na across basolateral membrane
- Creates concetration difference and difference in electrical charge due to K leak
- Na passively across apical membrane
- More Na into peritubular capillaries
- Ca-ATPase, H-ATPase and H/K-ATPase also use this
Why is ATP used to transport Na across the basolateral membrane in primary active transport for ultrafiltrate reabsorption?
Na/K+ ATPase not present in apical membrane
Describe secondary active transport in ultrafiltrate reabsorption
- Uses ATP indireclty as uses concentration gradient created by primary Na+ linked glucose transport
- Primary creates concentration difference
- Drives apical Na uptake, couples with other substances to reabsorb them
- Some molecules exchanged for Na
Explain the effects of hyperglycaemia on urine production
- Infection risk (sugary water attracting bacteria)
- Osmotic effects, draws water into tubules and so increased urine production
- Glucose symporters reach saturation, no more water reabsorbed
What is nephrotic syndrome?
Protein appearing in urine
What are the signs of nephrotic syndrome
- Weight loss
How does oedema occur in nephrotic syndrome?
- Altered colloid osmotic pressure
- Abdominal leakage
How does weight loss occur in nephrotic syndrome?
- Loss of protein
- Liver accomodates
- Lose weight
Describe teh process of nephrotic syndrome
- Amyloid blocks glomerular basement membrane leads to loss of normal barrier function thus proteinuria, loss os plasma protein leading to oedema
- Chronic protein loss triggers renal inflammation leading to renal failure
- Chronic proteinuria leads to hypovolaemia acivating RAAS can lead to hypertension
What are the effects of hypertension on filtration?
Expansion of capillaries and so increased passage of large molecules
What is angiotensin II?
- Peptide hormone
- Causes vasoconstriction => increased blood pressure
- Results in enzyme binding (not protein production)
What are the primary functions of ADH?
- Retain water in body
- Constrict blood vessels
Give the biochemical class, site of production, site of action and if water or fat soluble for ADH
- Short peptide
- Kidneys (aquaporins)
Give the biochemical class, site of production, site of action and if water or fat soluble for aldosterone
- Adrenal cortex
Give the biochemical class, site of production, site of action and if water or fat soluble for angiotensin II
- ACE acting on AT1 in the blood
Give the biochemical class, site of production, site of action and if water or fat soluble for erythropoeitin
- Bone marrow
Give the biochemical class, site of production, site of action and if water or fat soluble for renin
- Juxtaglomerular apparatus
- Angiotensinogen in blood