Week 1 - F - Physiology 2 - Kidney structure and function

Question 1

On average, how much water do the kidneys produce per day?

Answer 1

On average produce around 1.5 litres of water per day

Question 2

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?

Answer 2

It will change the osmolarity of the ECF resulting in a fluid shift between ECF and ICF to restore fluid imbalance

Question 3

Kidneys play an important role in the acid-base balance What are three examples of waste products excreted in the urine?

Answer 3

Urea Bilirubin Uric acid Damage to the kidneys can result in build up of waste products

Question 4

What do the kidneys secrete to help maintain the blood pressure? What do the kidneys secrete when we become hypoxic or anaemic?

Answer 4

Secretes renin to help control the blood pressure Also secretes erythropoitein which stimulates RBC production

Question 5

Where is vitamin D synthesised from?

Answer 5

From the diet or from the sun

Question 6

What is the precursor to vitamin D3 (cholecalciferol), absorbed from the sun before being synthesised to vitD3 in the skin?

Answer 6

7-Dehydrocholesterol

Question 7

Once vitD3 is synthesised, what does the liver convert it to?

Answer 7

Converts it to 25OHvitD3 (25hydroxy vitamin D3)

Question 8

What does the liver then convert the 25OH VitD3 to?

Answer 8

Converts it to 1,25dihydroxy VitD3

Question 9

What is 1,25 dihydroxy vitD3 known as? (also used in psoriasis treatment)

Answer 9

Cacitriol and absorbs calcium from the gut to help make bones strong

Question 10

What in the urinary system produces the urine? Where is the urine stored?

Answer 10

Kidneys produce the urine It is stored in the bladder

Question 11

What further modification does the urine undergo once released from the kidneys? What connects the kidney to the bladder?

Answer 11

Doe not undergo any further modification Connected via the ureters

Question 12

What is the typical weight of an adult kidney? What percentage of the cardiac output does the kidneys recieve?

Answer 12

Typical weight is 150g Receives about 25% of the cardiac output

Question 13

What is the walls of the ureter surrounded by that can cause peristaltic contraction to push urine into the bladder?

Answer 13

Surrounded by smooth muscle

Question 14

The renal medulla has a striated appearance, what is the renal medulla made up of?

Answer 14

pyramids

Question 15

What is a functional unit? What is the functional unit of the kindey? each kidney is composed of millions of these functional units

Answer 15

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

Question 16

What is the functional unit of skeletal muscle?

Answer 16

Sarcomere

Question 17

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?

Answer 17

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

Question 18

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?

Answer 18

It enters the efferent arteriole

Question 19

What is the region of the distal convoluted tubule that passes between the afferent and efferent arterioles known as?

Answer 19

The juxtaglomerular apparatus

Question 20

What are the two types of nephron and which is more common?

Answer 20

There is a juxtamedullary and a cortical nephron Cortical nephrons account for 80% of nephrons Juxtamedullary nephrons account for 20%

Question 21

What are the two main differences between the juxtamedullary nephron and the cortical nephron?

Answer 21

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

Question 22

Which type of nephron is this? What is the single capillary following the loop of henle known as?

Answer 22

This is the cortical nephron Single capillary is known as the vasa recta

Question 23

Do the juxtamedullary or the cortical nephrons produce more concentrated urine?

Answer 23

The juxtamedullary nephrons produce more concentrated urine

Question 24

Which arteriole drains into the glomerulus? What arethe specialized cells of inner layer of Bowmans caspule?

Answer 24

The afferent arteriole drains into the glomerulus Bowmans capsule inner layer is made up of specialized cells called podocytes

Question 25

What is the function of the podocytes?

Answer 25

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

Question 26

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?

Answer 26

This is the basement membrane rich in collagen and glycoproteins

Question 27

What are the specialised cells of the juxtaglomerular apparatus that produces renin?

Answer 27

The juxtaglomerular cells (aka granular cells)

Question 28

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?

Answer 28

This is the macula densa

Question 29

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?

Answer 29

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

Question 30

What is urine? Modified filtrate of the blood What processes occur in the nephron tubules after fluid enters from the glomerulus?

Answer 30

Tubular reabsoprtion and secretion

Question 31

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?

Answer 31

Red blood cells and large proteins

Question 32

What percentage of the plasma entering the glomerulus is filtered? The remaining percentage is also filtered via tubular reabsorption and secretion

Answer 32

Only 20% of the plasma entering the glomerulus is filtered

Question 33

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

Answer 33

This is nephrotic syndrome

Question 34

In regards to the rate of secretion, reabsorption and filtration What does the rate of excretion equal?

Answer 34

Rate of excretion = rate of secretion (TS) + rate of filtration (GF) - rate of reabsorption (TR)

Question 35

Rate of filtration of X = [X]plasma x GFR What does this mean? What is the normal glomerular filtration rate?

Answer 35

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

Question 36

Rate of excretion of X = [X]urine x Vu What does this mean?

Answer 36

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)

Question 37

If the rate of filtration of the substance exceeds the rate of excretion of a substance, what must have happened?

Answer 37

There must be a net tubular reabsorption Rate of reabsorption of X = rate of filtration of X – rate of excretion of X

Question 38

If the rate of excretion exceeds the rate of filtration what must there be?

Answer 38

A net tubular secretion Rate of secretion of X = rate of excretion of X – rate of filtration of X

Question 39

Rate of filtration (1) and rate of excretion (2) are relatively easy to measure. What do rates of reabsorption and secretion show?

Answer 39

reflect tubular modification of filtrate Obtained by the difference between filtration and excretion

Question 40

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?

Answer 40

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