Renal Physiology 1 (Renal) Flashcards
What are the functions of the kidney (Hint: Regulation of ???, excretion of ??? and endocrine functions)
Regulates blood volume, blood pressurea and electrolye/acid-base balance.
Responsible for excretion of metabolic products (urea, bilirubin, creatinine), foreign substances and excess water.
Endocrine mechanisms: EPO release
How much of renal blood supply is filtered through the glomerulus?
95%. Rest supplies kidney with nutrients.
In which anatomical parts of the kidney do you find the nephron?
The renal corpuscle (glomerulus and Bowman’s capsule) and both convoluted tubules are found in teh cortex. THe loop of Henle extends into the medulla.
What are the two types of nephrons and their relative abundance?
Cortical nephrons - 80% of nephrons, mainly perform excretory and regulatory functions. Renal corpusle (glomerulus and Bowman’s capsule) is in the outer part of the cortex, with SHORT loops of Henle
Juxtamedullary nephrons - 20% of nephrons, allow us to concentrate very concentrated or very dilute urine. Renal corpulse is deep in the cortex, with LONG loops of Henle
Describe the blood supply of nephron.
Renal artery
Afferent arteriole - supplies glomerular capillaries that filter blood plasma.
Efferent arteriole - drains the glomerulus and forms peritubuluar capillaries (network of capillaries around the nephron) which later join up to the renal vein.
Describe blood flow through the kidney and where filtration, reabsorption etc occurs.
Blood comes in through the afferent arteriole of the renal artery, and is filtered at the glomerular capillaries.
It exits through the efferent arteriole, where it travels next to nephron, undergoing reabsorption from fluid, secretion into fluid and excretion of the fluid (urine) at the end.
What determines GFR?
The relative diameter of hte afferent and efferent arterioles determine PRESSURE inside the glomerular capillaries, and thus the GFR.
Afferent arteriole constriction reduces renal blood flow, reducing pressure, reducing GFR.
Efferent arteriole constriction reduces renal blood flow, increasing pressure, increasing GFR.
Describe the basic physiology of filtration, reabsorption, secretion and excretion in the nephron.
- Glomerular filtration - Water and most solutes in plasma filter out of glomerular capillaries, into the Bowman’s capsule and into renal tubule.
- Tubular reabsorption - 99% of water and useful solutes are reabsorbed back into peritubular space and returned to blood.
- Tubular secretion - material is secreted into tubular fluid (waste, drugs) and is excreted as urine.
Solute excretion = filtration + secretion - reabsorption
Describe the relative hydrostatic pressures of blood being processed in the nephron?
Average hydrostatic pressure of blood is around 100mmHg.
Inside the glomerulus, blood hydrostatic pressure is about 60mmHg. Past this, it has a significantly lower hydrostatic pressure as most solutes and volume of blood have decreased.
Describe the four components that make up net filtration pressure
Pressures that promote filtration:
- Capillary hydrostatic pressure
- Interstitial fluid osmotic pressure
Pressures that promote absorption
- Interstitial fluid hydrostatic pressure
- Plasma colloid osmotic pressure
What factors determine whether something will be filtered through the glomerulus?
Molecular weight and charge. Negatively charged basement membrane repels anions.
Large protein complexes, cells and platelets won’t be filtered.
How much filtrate is formed in the renal corpuscles of the kidneys each minute and each day?
125mL/min or 180L a day.
How do kidneys regulate filtration pressure?
Renal autoregulation
Nerual regulation
Hormonal regulation
Describe the two types of renal autoregulation.
Myogenic mechanisms - stretching triggers contraction of smooth muscle of afferent arterioles to REDUCE GFR.
Tubuloglomerula rmechanism - incresaed NaCl in blood = macula densa (salt sensors) signals to inhibit release of NO, causing afferent arteriole to constrict to REDUCE GFR.
This is imortant as NaCl reabsorption is time dependent.
How do hormonal and nervous factors impact GFR?
Nerves - noradrenaline - constrict the aff/eff arterioles, decreasing GFR.
Hormonal - ANP (increases aff, decreases eff, increasing GFR)
Hormonal - Angiontensin II (regulated by tubuloglomerular feedback)
