Week 1 - F - Physiology 2 - Kidney structure and function Flashcards
On average, how much water do the kidneys produce per day?
On average produce around 1.5 litres of water per day
It is important for kindeys to maintain the plasma volume and plasma osmolarity What will an imbalance in the water or salt concentration of the ECF cause?
It will change the osmolarity of the ECF resulting in a fluid shift between ECF and ICF to restore fluid imbalance
Kidneys play an important role in the acid-base balance What are three examples of waste products excreted in the urine?
Urea Bilirubin Uric acid Damage to the kidneys can result in build up of waste products
What do the kidneys secrete to help maintain the blood pressure? What do the kidneys secrete when we become hypoxic or anaemic?
Secretes renin to help control the blood pressure Also secretes erythropoitein which stimulates RBC production
Where is vitamin D synthesised from?
From the diet or from the sun
What is the precursor to vitamin D3 (cholecalciferol), absorbed from the sun before being synthesised to vitD3 in the skin?
7-Dehydrocholesterol
Once vitD3 is synthesised, what does the liver convert it to?
Converts it to 25OHvitD3 (25hydroxy vitamin D3)
What does the liver then convert the 25OH VitD3 to?
Converts it to 1,25dihydroxy VitD3
What is 1,25 dihydroxy vitD3 known as? (also used in psoriasis treatment)
Cacitriol and absorbs calcium from the gut to help make bones strong
What in the urinary system produces the urine? Where is the urine stored?
Kidneys produce the urine It is stored in the bladder
What further modification does the urine undergo once released from the kidneys? What connects the kidney to the bladder?
Doe not undergo any further modification Connected via the ureters
What is the typical weight of an adult kidney? What percentage of the cardiac output does the kidneys recieve?
Typical weight is 150g Receives about 25% of the cardiac output
What is the walls of the ureter surrounded by that can cause peristaltic contraction to push urine into the bladder?
Surrounded by smooth muscle
The renal medulla has a striated appearance, what is the renal medulla made up of?
pyramids
What is a functional unit? What is the functional unit of the kindey? each kidney is composed of millions of these functional units
Functional unit is the smallest unit of the body able to perform the functions of that organ The functional unit of the kidney is the nephron
What is the functional unit of skeletal muscle?
Sarcomere
Functional mechanisms of the nephron: 1. Filtration 2. Reabsorption 3. Secretion Which parts of the nephron are located in the medulla and which are in the cortex?
The glomerulus, proximal convoluted tubule, distal convuluted tubule and proximal collecting duct are within the cortex The loop of henle and the distal collecting duct are in the renal medulla
The Renal artery subdivides into afferent arteriole which enters the glomerulus, what does the blood from the glomerulus then enter after filtration at the glomerulus has occured?
It enters the efferent arteriole
What is the region of the distal convoluted tubule that passes between the afferent and efferent arterioles known as?
The juxtaglomerular apparatus
What are the two types of nephron and which is more common?
There is a juxtamedullary and a cortical nephron Cortical nephrons account for 80% of nephrons Juxtamedullary nephrons account for 20%
What are the two main differences between the juxtamedullary nephron and the cortical nephron?
Juxtamedullary nephron has a much longer loop of henle penetrating way deeper into the medulla Juxtamedullary nephron does not have peritubular cappilaries that follow the tubular component but instead has a single capillary following the loop of Henle
Which type of nephron is this? What is the single capillary following the loop of henle known as?
This is the cortical nephron Single capillary is known as the vasa recta
Do the juxtamedullary or the cortical nephrons produce more concentrated urine?
The juxtamedullary nephrons produce more concentrated urine
Which arteriole drains into the glomerulus? What arethe specialized cells of inner layer of Bowmans caspule?
The afferent arteriole drains into the glomerulus Bowmans capsule inner layer is made up of specialized cells called podocytes
What is the function of the podocytes?
To wrap around the glomerulus forming a blood-kidney barrier with filtration slits for filtered blood to pass through into the Bowmans capsule and into the proximal convoluted tubule
Through the process of glomerular filtration, a portion of the plasma is filtered across and enters the lumen of the bowmans capsule to enter the proximal tube What is the aceullar membrane located betweent the endothelial layer of the glomerulus and the podocyts of the Bowmans membrane?
This is the basement membrane rich in collagen and glycoproteins
What are the specialised cells of the juxtaglomerular apparatus that produces renin?
The juxtaglomerular cells (aka granular cells)
What are the other specialised cells in the juxtaglomerular apparatus that are salt sensitive cells and detect the sodium (salt levels) in the distal convoluted tubule?
This is the macula densa
The macula densa can release vasoactive mediators that act on the smooth muscle of the affernet arteriole What would the macula densa release vasocative mediators to cause vasoconstriction?
If there was a drop in blood pressure - also the renin would be released from the granular cells of the juxtaglomerular apparaturs to increase sodium reabsorption
What is urine? Modified filtrate of the blood What processes occur in the nephron tubules after fluid enters from the glomerulus?
Tubular reabsoprtion and secretion
IN the tubules, substances can be absorbed back into the blood or secretion from the blood into the tubular fluid What does the intitial tubular fluid lack making it different from plasma?
Red blood cells and large proteins
What percentage of the plasma entering the glomerulus is filtered? The remaining percentage is also filtered via tubular reabsorption and secretion
Only 20% of the plasma entering the glomerulus is filtered
What is the syndrome that is usually caused by damage to the clusters of tiny blood vessels (glomeruli) of your kidneys? It can result in the glomeruli not functioning causing loss of protein which will lead to proteinuria and oedema
This is nephrotic syndrome
In regards to the rate of secretion, reabsorption and filtration What does the rate of excretion equal?
Rate of excretion = rate of secretion (TS) + rate of filtration (GF) - rate of reabsorption (TR)
Rate of filtration of X = [X]plasma x GFR What does this mean? What is the normal glomerular filtration rate?
Rate of filtration of X = mass of X filtered into the Bowman’s capsule per unit time. Rate of filtration of a subatnce is equal to the concentration of the substance in the plasma times the GFR Normal GFR is 125mls per minutes
Rate of excretion of X = [X]urine x Vu What does this mean?
Rate of excretion of substance X is the concentration of the substance in the urine times the volume of urine produced per time (rate of urine production) Rate of excretion of X = mass of X excreted per unit time. (measured in mg/min)
If the rate of filtration of the substance exceeds the rate of excretion of a substance, what must have happened?
There must be a net tubular reabsorption Rate of reabsorption of X = rate of filtration of X – rate of excretion of X
If the rate of excretion exceeds the rate of filtration what must there be?
A net tubular secretion Rate of secretion of X = rate of excretion of X – rate of filtration of X
Rate of filtration (1) and rate of excretion (2) are relatively easy to measure. What do rates of reabsorption and secretion show?
reflect tubular modification of filtrate Obtained by the difference between filtration and excretion
Cl- filtered = [Cl-]plasma × GFR
- = 110 mmol/l × 0.12 litre/min
- = 13.2 mmol/min Cl- excreted = [Cl-]urine × Vu
- = 200 mmol/l × 0.001 litre/min
- = 0.2 mmol/min
KEEP UNITS CONSTANT
What is this telling us?
The rate of filtration of chlorine exceeds the rate of excretion of chlorine
As Rate of reabsorption of X = rate of filtration of X – rate of excretion of X
Then the rate of reabsroption of chlorine was 13mmol/min
