Renal system

Question 1

What are the renal systems main functions?

Answer 1

• Excretion or removal from the body of nitrogenous waste in the form of urea.
• Osmoregulation or regulation of the water balance of the body.

Question 2

Why and how is nitrogenous waste expelled from the body?

Answer 2

Proteins and nucleic acids contagion nitrogen. We take in more nitrogen containing compounds in our food than we need daily.

Any excess is converted into urea by the liver.

The urea is transported in the blood to the kidneys where it is removed from the blood during the formation of urine.

Question 3

What are the components of the renal system?

Answer 3

• Kidneys
• Nephron
• Ureter
• Bladder
• Urethra

Question 4

How are the kidneys supplied with blood?

Answer 4

By the left and right renal arteries, which supplies the kidneys with blood from the heart.

Question 5

How does blood leave the kidneys?

Answer 5

Via the renal veins, and back to the heart.

Question 6

How is urine formed in the kidneys transported to the bladder?

Answer 6

It’s transported via the ureter, to the bladder where it is stored prior to urination.

Question 7

What is the function of the kidney capsule?

Answer 7

It’s protects the kidneys.

Question 8

what is the function of a the kidney cortex?

Answer 8

It has layers of tissue and contains the nephron.

Question 9

What is the function of the renal pelvis?

Answer 9

Nephrons drain into it.

Question 10

What is the function of the capillaries?

Answer 10

To reabsorb materials.

Question 11

How many nephrons do each kidney contain?

Answer 11

Each kidney contains about 1 million nephrons.

Question 12

What is the function of the nephron?

Answer 12

This is where blood is filtered and where water and other useful substances are re absorbed, leading to the production of urine.

Question 13

What adaptions does the nephron have?

Answer 13

• The length of the nephron means that there is a large surface areas for exchange.
• The wall of the nephron is a single layer of epithelial cells that is in close contact with capillaries, whose walls are a single layer of endothelial cells. This means that there is a short diffusion pathway.
• The layout of the nephron, with the loop of Henle, helps to maintain a concentration gradient. Therefor, the nephron has all the characteristics of a good exchange surface.

Question 14

What is the function of the ureters?

Answer 14

The left and right ureters take urine from each kidney to the bladder where it is stored until the bladder is emptied via the urethra during urination.

Question 15

Why is urea expelled from the body?

Answer 15

It’s toxic.

Question 16

What pathway does blood take through the nephron?

Answer 16

• Renal artery
• Afferent arteriole
• Glomerulus
• Efferent arteriole
• Blood capillaries
• Renal vein

Question 17

What pathway does urine take through the nephron?

Answer 17

• Bowmans capsule
• Proximal convoluted tubule
• Loop of Henle
• Distal convoluted tubule
• Collecting duct
• Ureter

Question 18

What is the difference between the efferent and afferent arteriole?

Answer 18

The afferent arteriole is thicker and the narrowing of it, causes it to have a high blood pressure.

Question 19

What are the 4 steps to osmoregulation in the nephron?

Answer 19

1) The formation of the glomerular filtrate via ultrafiltration.
2) Reabsorption of glucose and water by the proximal convoluted tubule.
3) Maintenance of a gradient of sodium ions by the loop of Henle.
4) the distal convoluted tubule.

Question 20

Explain the process of ultra filtration.

Answer 20

• This occurs in the glomerulus and bowmans capsule, due to the increased pressure there as a result of the differing volumes of the afferent and efferent arteriole.
• Blood builds up in the glomerulus.
• Water, glucose, amino acids, ions and urea are forced into the bowmans capsule, forming the glomerular filtrate.
• Proteins and cells are too large to be filtered through, so they stay in the blood.

Question 21

Explain the process of reabsorption.

Answer 21

• Sodium ions are actively transported out of the epithelial cells of the proximal convoluted tubule, into the blood, lowering the concentration of sodium in the epithelial cell.
• Sodium ions diffuse down a concentration gradient from the lumen of the proximal convoluted tubule into the proximal convoluted tubules epithelial cells via carrier proteins.
• Carrier proteins carry another molecule, like glucose via co-transport.
• Molecules then diffuse into the blood via facilitated diffusion down a concentration gradient.
• As a result, all the glucose and other valuable molecules like water are reabsorbed.

Question 22

Explain how a gradient of sodium is maintained by the loop of Henle.

(sorry about the length of this answer)

Answer 22

• Sodium ions are actively removed from the ascending limb using ATP from the mitochondria in the cells that line the walls.
• This creates a water potential, causing high osmolarity, in the region of the medulla between two limbs. Normally, water would leave the ascending limb via osmosis as a result. However, the thick walls of the limb prevent this.
• The walls of the ascending limb are very permeable to water, so it passes out of the filtrate via osmosis into the interstitial space, then to the blood capillaries and is carried away.
• The filtrate looses water as it moves down the descending limb, lowering its water potential, increasing osmolarity. It reaches its lowest water potential at the top of the loop of Henle.
• At this point, sodium ions diffuse out of the filtrate as it moves up the ascending limb and are actively pumped out.
• The filtrate decreases in the number of solutes dissolved per litre, but increases in its water potential the further up the medulla it goes.

Question 23

Explain the role of the distal convoluted tubule.

Answer 23

• This alters the PH of the filtrate by absorbing some water or ions by active transport.
• There numerous microvilli and mitochondria in the cells of the DCT.
• Hormones control which ions are to be reabsorbed by changing the permeability of the tubule walls.
• The filtrate is then passed into the collecting duct and then to the ureter.
• ADH is the hormone which control the permeability of the collecting duct. Therefore if you drink loads of water, the walls are more permeable, so the urine concentration is smaller.

Question 24

Why are glucose and amino acids reabsorbed into the bloodstream?

Answer 24

They are required by the body for an array of functions.

Question 25

What role does the renal system have in homeostasis?

Answer 25

It has a role in osmoregulation, which is an important part of homeostasis.

Regulating water balance also plays a part in maintaining blood pressure.

A rise in blood pressure can be caused by a rise in blood volume.

More water is removed by the kidney when the release of ADH is inhibited, leading to a reduction in blood pressure.