3) Urinary System Structure And Function Flashcards
What is are 2 examples of important roles of the kidney?
Remove urea from the blood (structures in the cortex)
Aid osmoregulation (tubules extending into the medulla)
What is involved in the urinary system? (8)
Aorta
Vena Cava
Renal Vein + Artery
Right + Left Kidney
Ureter
Bladder
Urethra
Sphincter Muscle
What is the function of the renal vein?
The renal vein takes cleaned blood from the kidney to the heart
What is the function of the renal artery?
The renal artery brings blood with wastes (urea) to the kidney to be cleaned
What gives kidneys its distinctive layers?
Due to 1-2million nephrons in each kidney
Where are the 2 kidneys located?
The 2 kidneys sit either side of the aorta at the rear of the abdomen
Where is blood filtered?
In the cortex
What is the purpose of the ureter?
Carry urine to the bladder
What is the functional unit of the kidney?
The nephron
What is the purpose of the Bowman’s capsule?
Has little resistance to fluid leaving the blood but prevents cells and large proteins from passing into the tubule
How is the proximal tubule adapted for rapid absorption?
The wall of the proximal tubule has a large surface area due to microvilli.
ATP readily available from many mitochondria.
How much fluid does the kidney filter out of the blood each day?
Around 180dm³ of fluid
Where does the majority of filtered fluid return to and how?
The blood, by a complex network of blood vessels around the kidney tubules.
What is ultrafiltration?
The process in which kidneys remove urea from the bloodstream
What is the first stage of produce urine?
Filtering of blood in the Bowman’s capsule
What is filtration based off of?
Particle size, most proteins are too big to pass into the tubules
What does the filtrate produced compare to?
The filtrate produced has a composition very similar to plasma
Why is there a very thin barrier between blood in the capillary and the tubule lumen?
Due to many gaps between the capillary endothelium cells
Why is the formation of filtrate promoted?
Because blood enters the glomerulus under pressure
The afferent arteriole entering the glomerulus is wider than the efferent vessel leaving.
How is majority of filtrate is returned to the blood?
Through the proximal convoluted tube (PCT)
What is left in high concentration in the filtrate?
Waste products such as urea.
What does 5 things do active transport recover in the blood?
Glucose, amino acids, proteins, vitamins and hormones.
How is active transport of the blood supplied?
By ATP produced by mitochondria
What does DCT stand for?
Distal convoluted tube
What are the 3 functions of the DCT?
-Secretes waste chemicals such as creatinine into the filtrate
-Pumps ions to control blood pH
-Helps control blood volume and therefore concentration of urine
What is the purpose of the loop of Henle?
Producing a very high concentration of solutes in the medulla of the kidney so it has a very low water potential.
How does low water potential affect urine?
Allows to produce urine more concentrated and less concentrated than plasma
What is hypertonic?
More concentrated
What is hypotonic?
Less concentrated
Explain how filtrate in the loop of Henle is hypertonic to blood plasma in some places
Filtrate is hypertonic at the base of the loop, deepest into the medulla. This is because water has left the filtrate by osmosis as it passes through the medulla, filtrate is isotonic to the medulla tissue.
Explain how filtrate in the loop of Henle is hypotonic to blood plasma in some places
Filtrate becomes hypotonic as it reaches the DCT as ions diffuse and are actively pumped out of the tubule as it passes out of the medulla.
The loop of Henle is a counter current multiplier, what does this mean?
This means that the flow of filtrate in the two limbs is in opposite directions and the longer the loop the greater the effect on the concentration of the filtrate.
Refer to PG.99 for diagram of loop of Henle
What is urine often tested for?
Proteins or glucose
What would finding plasma protein in the kidneys suggest and why?
Damage to the kidney membranes, as plasma proteins are too big to cross the filtration barrier in the Bowman’s capsule
What is the reason that plasma proteins are found in the kidneys? (often)
High blood pressure
What would finding glucose in the kidneys suggest and why? (2 examples)
Mechanism for reabsorption was damaged, as all glucose is normally removed from filtrate in the PCT.
Another possibility is that the concentration of glucose of blood is too high for it all to be reabsorbed as occurs in diabetes
What is mammalian plasma concentration controlled by and where?
Pituitary gland and osmoreceptors, in the hypothalamus of the brain.
What is the hormone released by the pituary gland?
Antidiuretic hormone (ADH)
What is the purpose of ADH?
Affects the permeability of the kidney tubules to water.
Describe the process of osmoregulation
Change in water potential of plasma, osmoreceptors in the hypothalamus detects this.
Nerve impulses stimulate the release of ADH at the posterior pituitary gland.
Then nephron filters the blood to regulate water, and then the normal water potential is restored
What is an example of a negative feedback mechanism
Controlling the water potential of body fluids
What happens when the concentration of blood changes?
The amount of ADH released changes to maintain a dynamic equilibrium.
What controls the amount of ADH released by the pituitary gland?
Nervous stimulation from the hypothalamus
What would occur to the filtrate if there is no ADH?
The hypotonic filtrate passes through the collecting duct unchanged, producing high volumes of dilute urine.
What does the quantity of ADH released by the pituitary gland control?
Concentration of urine produced by the kidneys
Volume of urine produced by the kidneys
What does the control of the concentration + volume of urine help to do?
The quantity of ADH helps to maintain the water potential of body fluids within a very narrow range
What two properties of fluids in the kidney affects the effect of ADH on urine concentration?
1) The filtrate as it reaches the end of loop has water potential than that of plasma (more dilute)
2) The medulla has a very low water potential
How does ADH allow water to pass through?
By causing channels to open in the collecting duct
The medulla has a very low water potential, what does this cause?
Water will leave the filtrate by osmosis as it pass through
What does ADH to walls of the collecting duct?
Makes them permeable by water
How does water leave the filtrate?
By osmosis
What is vessel carry the water away?
Capillaries
What does arid mean?
Excessively dry
What kind of conditions do kangaroo rats live in
Arid conditions, so they are never able to drink water
How do kangaroo rats obtain water?
From food and biochemical reactions
How do they conserve water?
By producing very little and very concentrated urine
How does the kidney structure adapt to produce concentrated, low amounts of urine in kangaroo rats?
They have nephrons with very long loops of Henle to produce a very low water potential in the medulla
The tubules have more microvilli and mitochondria than other animals, for efficient reabsorption
What is the term to describe the kidney maintaining balance in the body?
Homeostasis
What are the 3 things the kidney does to maintain balance in the body?
Regulate the amount of water in the plasma
Maintain blood pressure + electrolyte balance
Regulate the pH of the plasma
What mechanism is used by the kidneys to maintain blood pressure + electrolyte balance?
Angiotensin-aldosterone mechanism
What are the steps in the renin-angiotensin-aldosterone mechanism? ( 7 STEPS)
1) Decrease in blood pressure, juxtaglomerular cells of kidneys increase renin in blood stream
2) Renin splits angiotensinogen (made and released by liver) to make angiotensin I.
3) Angiotensin I (inactive) is split by ACE inhibitors in the lungs, to make angiotensin II.
4) Angiotensin II causes the vasoconstriction of arterioles which increases blood pressure until it returns to normal.
5) Angiotensin II also triggers the adrenal cortex to produce aldosterone and pituitary gland to produce ADH.
6) Aldosterone increases water and sodium absorption in the kidneys. And increases potassium and hydrogen secretion into urine.
7) Increase in sodium and water absorption causes the blood volume to increase and blood pressure to increase.
What does pH stand for?
Potential of hydrogen
What does a low pH mean?
That it is acidic
What does a high pH mean?
That it is alkaline
What is the scale of pH range?
0-14
What is the number of neutral pH?
7
What makes a solution acidic?
A high concentration of hydrogen ions, a low pH.
What is a base?
A substance that produces hydroxide (OH-) in solution and/or accepts hydrogen ions.
What range of pH does fluids in the body have to lie in between?
pH 7.35 -pH 7.45
Why do fluids have to have a pH in between a certain range?
Otherwise enzymes will be denatured.
Do kidneys respond slowly to pH imbalance
Yes
What does the kidney do if the tissue fluid is too acidic?
Hydrogen ions are absorbed into the tubular fluid and bicarbonate ions are excreted
What does the kidney do if the tissue fluid is too alkaline?
Hydrogen ions are excreted and bicarbonate ions are absorbed into the tubular fluid.
What happens when the kidneys fail?
They stop removing toxic waste from the blood such as urea, these toxins can build up and kill the person.
Give 3 examples of why the kidneys may fail.
Diabetes mellitus
Hypertension
Infection
How does dialysis work?
It takes over the job of the kidneys, and their blood passes through the machine. It removes waste products and balances the levels of water and salts in the blood.
How often does dialysis need to be carried out per week.
3-4 times a week, each time lasting 4-5 hours.
What are the 2 types of dialysis?
Haemodialysis
Peritoneal dialysis
What does counter current mean in dialysis?
Blood flows one way and dialysis fluid flows the opposite way
Why are the urea levels in the dialysis fluid 0?
Maintains a concentration gradient, so all the urea leaves the blood and enters the dialysis fluid and is taken away
What are the 2 types of kidney transplants?
-From a live donor
-From a dead donor
How does the kidney connect to the recipient during transplant?
Joined to the blood vessels and the bladder in the groin.
What is the benefit of a kidney transplant?
If successful, kidneys can clean and balance the blood and recipient can lead a normal life.
What is the risks of a kidney transplant?
The antigens on a donor kidney may be different from the recipient. The recipient immune system detects the difference and may reject the new kidney.
How do we reduce the risk of a kidney transplant?
Find a donor with a tissue type as close to the recipient as possible.
Why are immunosuppressants drugs given to the recipient during a kidney transplant?
To suppress the immune system to prevent rejection.
