Biology - kidneys and homeostasis

Question 1

What are the functions of the kidney?

Answer 1

they regulate the water content in the blood
they excrete/remove the toxic waste products of metabolism

Question 2

What is the order of the excretory system?

Answer 2

1) Blood is brought to the kidney in the renal artery
2)The kidney regulates/controls the water and salt content and removes urea.
3)The filtered excess water, salts and urea form a liquid called urine.
4)The urine is transported to the bladder along tubes called ureters.
5)The bladder stores the urine until it is convenient to expel it from the body through the urethra.
6)The purified blood returns to the circulation through the renal vein and to the heart through the vena cava.

Question 3

What is the structure of the kidney?

Answer 3

Cortex - layer on outside
Medulla - little ball looking things
Pelvis - Centre of the Kidney
Ureter - Tube coming out
Renal artery - Artery of blood going into kidney
Renal vein - Vein of blood coming out of kidney

Question 4

How does the nephron work?

Answer 4

1) Blood goes into a ball of capillaries called a capillary knot
2) High pressure is created in the knot as the entry is bigger than the exit.
3) This pressure results in ultrafiltration where water, salts, glucose and other small molecules pass out of the capillary into the Bowmans capsule which takes it to the tubule. Proteins and blood cells are too big to leave capillaries.
4) All of the glucose and some water and salts are reabsorbed into surrounding capillaries around the tubule by selective reabsorption.
5) The collecting duct is responsible for the selective reabsorption of water and sending urine to the ureter.

Question 5

What is ADH?

Answer 5

Anti-diuretic hormone - It controls the water content in the blood. Helps kidney control amount of water and salt in blood.

Question 6

How can the concentration of blood be altered?

Answer 6

excess drinking (increases water content)
excess sweating (decreases water content)
consumption of salty foods (decreases water content)

Question 7

How does ADH react when there is too little water in blood?

Answer 7

-Brain detects water level
-Pituitary gland releases more ADH
-More water is reabsorbed by the kidneys
-Less water is lost in urine

Question 8

How does ADH react when there is too much water in blood?

Answer 8

-Brain detects water level
-Pituitary gland releases less ADH
-Less water is reabsorbed by the kidneys
-More water is lost in urine

Question 9

How can urine indicate that someone is suffering from a disease?

Answer 9

-Glucose in the urine indicates the person is suffering from diabetes. The glucose levels in the blood are so high the kidney is unable to reabsorb it and it leaves the body in urine.
-Protein in the urine indicates damage in the kidney, as generally proteins in the blood are too large to pass through into the nephron tubule

Question 10

Why is a dialysis machine needed?

Answer 10

In order to remove toxic urea, and to maintain the correct balance of salts and water in the body, a patient whose kidneys are not working properly needs to spend many hours a week attached to a dialysis machine.

Question 11

What are the advantages of a dialysis machine?

Answer 11

-It can keep a patient alive whilst they are waiting for a suitable donor to be found.
-It does not involve major surgery.

Question 12

What are the disadvantages of a dialysis machine?

Answer 12

-Patients need to follow a carefully controlled diet.
-Patients need to spend many hours every week attached to a dialysis machine.
-Dialysis machines are very expensive.
-Dialysis will only be successful for a certain amount of time.

Question 13

What is rejection in transplantation?

Answer 13

This is where the immune system of the patient receiving the kidney recognises the transplant as non-self and destroys it.

Question 14

How can rejection be prevented in transplantation?

Answer 14

It is essential that any transplanted kidney is as similar as possible to the patient’s tissue type. However, the patient will still need to take immunosuppressant drugs for the rest of their life.

Question 15

What are the advantages of kidney transplant?

Answer 15

-Once the transplant has occurred the patient no longer has diet restrictions.
-Long periods of time on dialysis are no longer necessary.
-Although not a life-long cure, a kidney transplant will generally allow the patient to live a fuller life for longer than a patient on dialysis.

Question 16

What are the disadvantages of kidney transplant?

Answer 16

-It is difficult to find a donor organ with a matching tissue type.
-The risk of organ rejection.
-Having to take drugs which suppress the immune system, leaving the patient susceptible to contracting other diseases.
-Regular doctors’ appointments to detect signs of organ rejection.
-Major surgery is required.

Question 17

How does a dialysis machine work?

Answer 17

1)Blood is removed from the patient and flows into the dialyzer where it is kept separated from dialysis fluid by a partially permeable membrane.
2)The dialysis fluid contains the same concentration of glucose and salts as normal blood plasma so there is no net movement of glucose out of the blood by diffusion.
3)Excess salts diffuse into the dialysis fluid.
4)The dialysis fluid contains no urea, so all of the urea diffuses from the blood in to the dialysis fluid from the high concentration in the blood to the lower concentration in the dialysis fluid.
5)The blood and dialysis fluid move in opposite directions across the membrane (a counter current system) in order to maintain concentration gradients all the way along.
The clean blood is returned to the patient and the waste dialysis fluid is disposed of.