11.3 The kideny and osmoregulation

Question 1

What is excretion?

Answer 1

Excretion is the removal from the body of the waste products of metabolic activities

Question 2

What are the two main functions of the kidney?

Answer 2

1. to remove urea from our bodies 2. Regulating of water (osmoregulation)

Question 3

What is osmoregulation?

Answer 3

Osmoregulation is the control of water balance of the blood, tissue or cytoplasm of a living organism

Question 4

What are animals known for as an example to different responses to changes in osmolarity?

Answer 4

Animals are either osmoregulators or osmoconformers.

Question 5

Why are many animals known as osmoregulators?

Answer 5

Becuase they maintain a constant internal solute concentration even when living in marine environments with very different osmolarities.

Question 6

What are some examples of osmoregulators?

Answer 6

All terrestrial animals, fresh water animals and some marine organisms like bony fish

Question 7

What are osmoconformers?

Answer 7

animals whose internal solute concentration tends to be the same as the concentration of solutes in the environment

Question 8

What controls reabsorption of water in collecting duct?

Answer 8

In humans, osmoregulation is associated with a hormone known as ADH (inhibits production of urine)

Question 9

How does ADH and water balance work in the system?

Answer 9

1. When a person becomes dehydrated, the hypothalamus will detects an increase in concentration of blood plasma 2. This causes the pituitary to release ADH 3. ADH sends message to the kidneys to reabsorb more water (urine becomes more concentrated)

Question 10

How is osmoregulation involved in insects?

Answer 10

The malpighian tubule system in insects and the kidney carry our osmoregulation and removal of nitrogenous wastes

Question 11

What is hemolymph?

Answer 11

circulating fluid in that combines characteristics of tissue fluid and blood

Question 12

How does osmoregulation occur with hemolymph?

Answer 12

Homeostasis where concentration of hemolymph is kept within certain range

Question 13

What happens when animals break down amino acids?

Answer 13

The nitrogenous waste product is toxic and needs to be excreted. This is in the form of uric acid for insects. In mammals it is urea.

Question 14

What are malpighian tubules?

Answer 14

Tubes that branch off from their intestinal tract in insects. The cells lining the tubules actively transport ions and uric acid from hemolymph into the lumen of the tubules.

This also causes water to enter lumen by osmosis from the hemolymph. (Osmoregulation removes excess water and salt)

The tubules empty their contents into the gut.

In the hindgut most water and salts are reabsorbed while nitrogenous waste is excreted with feces

Question 15

Draw a diagram of a human kidney

Answer 15

• cortex, shown at the edge of kidney
• medulla, shown inside the cortex (with pyramids)
• pelvis, whown on the concave side of the kidney
• ureter, shown connecting with the pelvis/; on concave side/ hilum
• renal artery, shown connected to the concave/ pelvis side/ away from cortex
• renal vein, shown connected to the concave/ pelvis side/ away from cortex

Question 16

Outline what would happen to plasma solute concentration and ADH concentration if a person were to drink water to satisfy his/her thirst. [2]

Answer 16

• after drinking water, blood plasma / solute concentration decreases;
• plasma ADH concentration decreases;
• osmoreceptors in the hypothalamus monitor blood solute / blood plasma / plasma
• concentration;
• impulses passed to ADH neurosecretory cells to reduce / limit release of ADH;
• drop in ADH decreases the effect of this hormone on the kidneys;
• blood solute concentration returns to normal;

Question 17

Is the composition of blood in the renal artery differnt from the renal vein?

Answer 17

Composition of blood in renal artery is different from that in the renal vein because kidneys perform osmoregulation and excretion

Through this they are removing substances that are uneeded or harmful which makes composition of blood different in artery than the vein.

Question 18

What is the renal artery?

Answer 18

• Blood enters the kidney through this tubes

Question 19

What is a renal vein?

Answer 19

Blood leaves the kidney through this tube (flows TO the heart)

Question 20

What substances are present in higher amounts in the renal artery than the renal vein?

Answer 20

• toxins and other substances that are ingested and absorbed (but not fully metabolized by the body)
• excretory waste products (mainly urea)

Question 21

What other things are removed from the blood by kidney that are not excretoru products?

Answer 21

• excess water (cell respiration/absorbed from food)
• excess salt (absorbed from food)

Question 22

What are excretory products?

Answer 22

Products that are not produced by body cells.

Question 23

Does the renal artery or the renal vein have more constant concentration?

Answer 23

• Renal artery contains variable water/salt content
• renal veins are more constant due to osmoregulation

Question 24

Are unwanted substances present in the renal vein or renal artery?

Answer 24

When kidneys actively reabsorb specific substances that the body needs which leaves unwatned substances pass out (as urine).

Therefore the substances are present in the renal artery as susbtances enter the kidney

Question 25

Is the blood deoxygenated in the renal vein or renal artery?

Answer 25

Blood leaving the kidney through renal vein is deoxygenated because metabolism requires oxygen (ATP)

Question 26

What is a side product of metabolism?

Answer 26

Renal vein has higher partial pressure of carbon dioxide as a side product.

Question 27

Why is the concentration lower in renal vein (compared to renal artery)?

Answer 27

Even though glucose is normally filtered and then reabsorbed, some glucose is used by the metabolism of kidney which lowers the concentration.

Question 28

Where are plasma proteins present?

Answer 28

They are not filtered by kidney (so present in the same concentration) in both blood vessels.

Presence in urine is abnormal

Question 29

Compare the composition of the blood in the renal artery and renal vein. 2 marks

Answer 29

• blood in renal artery more oxygenated than the blood in the renal vein / oxygenated versus deoxygenated
• blood in renal artery contains more urea than the blood in the renal vein / urea versus no urea / nitrogenous waste products
• blood in renal artery contains more glucose than the blood in the renal vein
• variable water / salt content in renal artery but constant / correct / regulated content in vein

Question 30

What is glomerular filtrate?

Answer 30

As the pressure in capillaries is high and the walls permeable, fluid is forced out of the tissues called glomerular filtrate

Question 31

What is ultrafiltration?

Answer 31

When fluid from capillaries leaks into the bowman’s capsule, most molecules (Na ions, Cl ions, glucose, urea) filtrate.

But proteins and blood cells are too large. The separation of particles is called ultrafiltration

Question 32

What separates the capillaries?

Answer 32

Basement membranes

Question 33

What is the function of podocytes?

Answer 33

Acts as a barrier through which waste producs are filtered from the blood

Question 34

What are the three parts of ultrafiltraction?

Answer 34

Fenestrations, basement membrane and podocytes

If particles pass through all three parts, they are part of glomerulus filtrate

Question 35

What are fenestrations?

Answer 35

Gaps in the capillaries walls which allow fluid to escape but not blood cells

Question 36

What does the basement membrane do?

Answer 36

Covers and supports the wall of capillaries and is made of negatively charged glycoproteins (forms a mesh)

Prevents plasma proteins from being filtered out (too big)

Question 37

What forms the inner wall of the Bowman’s capsule?

Answer 37

Podocytes have extensions that wrap around the capillaries of the glomerulus and short side branches (foot processes)

Question 38

What do foot processes do?

Answer 38

Prevent small molecules form being filtured out of blood (in glomerulus)

Question 39

Where does the glomerulus filtrate travel after the bowman’s capsule?

Answer 39

Proximal convulated tubule where most reabsorption occurs

Question 40

How are sodium reabsorbed in the proximal convoluted tubule?

Answer 40

moved by active transport from filtrate to space outside to peritubular capillaries using pumps located in outer membrane of tubule cell

Question 41

How are chloride ions reabsorbed?

Answer 41

Attracted from filtrate to space outside the tubule because of charge gradient (made by Na+)

Question 42

How is glucose reabsorbed?

Answer 42

co-transportated out of filtrate, by proteins in outer membrane of tubule cells

As Na+ moves down concentration gradient (from outsde to inside), glucose and amino acids can move with this energy at the same time out of tubule

Question 43

How is water reabsorbed in the proximal convoluted tubule?

Answer 43

Because of other reabsorption, solute gradient is created, so water is reabsorbed by capillaries by osmosis

Question 44

annotate diagram of nephron

Answer 44

• Bowman’s capsule
• Proximal convulated tubule
• loop of henle
• distal convoluted tubule
• collecting duct
• blood vessels
  
  • afferent arteroile
  • glomerulus
  • efferent arteroile
  • pertubular capillaries
  • vasa recta
  • venules

Question 45

What is a proximal convoluted tubule?

Answer 45

highly twisted section of the nephron, with cells in the wall with mitochondria and microvilli projecting into lumen

Question 46

Difference between distal convoluted tubul and proximal?

Answer 46

Distal has fewer and shorter microvilli and fewer mitochondria

Question 47

What does the collecting duct do?

Answer 47

carries filtrate back to cortex and medulla to renal pelvis

Question 48

What is the function of the loop of Henle?

Answer 48

• creates gradient of solute concentration in medulla

Question 49

What is interstital fluid?

Answer 49

Sodium ions are pumped out of filtrate in the ascending limb (loop of henle)

(basically outside fluid)

Question 50

What is special about the ascending limb?

Answer 50

the walls are impermeable to water, so water is retained in the filtrate even though interestial fluid is hyper tonic (high in concentration)

Question 51

Why is water drawn out of filtrate in the descending limb of loop of henle?

Answer 51

solute concentraiton of interestial fluid is increased due to Na+

Question 52

What is a countercurrent multiplier system? (Give example)

Answer 52

Flows of fluid in opposite directions causing steeper gradient of solute concentrations

Example: Raising solute concentration in medulla, vasa recta

Question 53

What does the countercurrent system in the vasa recta prevent?

Answer 53

Prevents blood flowing in the vessel to dilute the solute concentration of medulla, so vasa recta can still carry away water removed from filtrate

Question 54

What does it mean when an animal has a longer loop of henle?

Answer 54

the longer, the more water volume will be reclaimed (conserved) and the thicker the medulla

Animals in dry climates often have longer ones

Question 55

What is produced when animals break down amino acids and nucleic acids?

Answer 55

Nitrogenous waste in form of ammonia

Question 56

Why can organisms in marine habitats release waste directly as ammonia, and terrestial aniamsl must convert ammonia?

Answer 56

Ammonia is very basic and toxic

• Released in water, it is diluted easily
• Terrestial must convert into less toxic forms like urea depending on evolutionary history

Question 57

Why do birds and insects release waste as uric acid?

Answer 57

Although it requires even more energy than converting into urea, it is not water soluble and does not require water to be released and crystalizes

For birds, it means less energy on flight

Question 58

Causes and consequences of dehydration

Answer 58

Causes:

• exercise
• insufficient water intake
• diarrhoea

Consequences:

• disruption in metabolic processes
• darkened urine (increased solute concentration)
• tiredness and lethargy (decreased muscle function
• increase heart rate

Question 59

What is used for treatment of kidney failure?

Answer 59

hemodialysis or kidney transplant

Question 60

What happens during hemodialysis?

Answer 60

A steeady flow of blood passes over artificial semi-permeable membrane

Blood is thus purified and returned to patient

Question 61

What are the pros and cons of kidney transplant than dialysis?

Answer 61

Pros:

• More independence (movement and freedom to travel)
• less risk of infections

Cons:

• recipient can reject organ because of immun system

Question 62

What can be tested during urinalysis?

Answer 62

Indicates pH, protein level and glucos level

High levels of protein/glucose –> diabetes

High protein –> damage to kidneys (ultrafiltration is malfunctioning)