Chapter 11.3 - The Kidney and Osmoregulation

Question 1

How do insects do osmoregulation?

Answer 1

+ Arthropods hv. a circulating fluid → Hemolymph = combines characteristics of tissue fluid and blood
+ Insect intestinal tracts = Malpighian tubules
→ cells lining tubules = actively transport ions and uric acid from the hemolymph into the lumen of the tubules
+ Draws water by osmosis from the hemolymph through the walls of the tubules into the lumen
+ Tubules empty their contents into the gut
** In the hind gut MOST of the water and salts are absorbed while nitrogenous waste = excreted as faeces

Question 2

Blood capillaries

Answer 2

At high pressure in many of the tissues of the body, and the pressure forces some of the plasma OUT of the capillary walls. to form Tissue fluid

Question 3

Why does in the Glomerulus the volume forced out of the capillaries 100x more than in other tissues? (Glomerulus Filtrate)

Answer 3

+ Pressure particularly HIGH and capillary walls = part. permeable

Question 4

Ultrafiltration

Answer 4

Separation of particles differing in size by a few nanometres

Question 5

What are the 3 parts of the Ultrafiltration site?

Answer 5

1) Fenestrations
2) Basement membranes
3) Podocytes

Question 6

Fenestrations

Answer 6

Between the walls of the capillaries

→ allow fluid to escape but NOT bl. cells

Question 7

Basement membrane

Answer 7

+ Covers and supports the wall of the capillaries
+ Made of negatively charged glycoproteins
→ forms a mesh
+ Prevents plasma proteins from being filtered out
→ due to size and negative charge

Question 8

Podocytes

Answer 8

+ Forming inner wall of Bowman’s capsule
+ Have extensions wrapped around capillaries of glomerulus and many short side branches = foot processes
V. narrow gap betw/ foot processes = help prevent small molecules from being filtered out of blood into Glomerulus

Question 9

Nephron

Answer 9

Basic functioning unit of a Kidney

Question 10

Bowman’s capsule

Answer 10

Cup-shaped w/ high porous inner walls = collects the fluid filtered from the blood

Question 11

Proximal Convoluted tubule

Answer 11

Highly twisted section of the nephron

→ w/ cells in the walls having many mitochondria and microvilli projecting into the lumen of the tube

Question 12

Loop of Henle

Answer 12

Carries filtrate deep into the medulla (descending limb)

→ carries back up to the cortex (ascending limb)

Question 13

Distal convoluted tubule

Answer 13

Highly twisted
→ FEWER and SHORTER microvilli
→ Fewer mitochondria

Question 14

Collecting Duct

Answer 14

Wider tube carries filtrate back through the cortex and medulla to renal pelvis

Question 15

Afferent Arteriole

Answer 15

Blood from renal artery

Question 16

Glomerulus

Answer 16

Tight-knot like, high pressure capillary bed = site of blood filtration

Question 17

Efferent Arteriole

Answer 17

Narrow vessels = restricts blood flow = help gen high pressure in Glomerulus

Question 18

Peritubular capillaries

Answer 18

Low pressure capillary bed that runs around convoluted tubules = absorb fluid from them

Question 19

Vasa Recta

Answer 19

Unbranched capillary
= similar to shape and size of Loop and Henle
+ Descending in the Medulla
+ Ascending in the Cortex

Question 20

Venules

Answer 20

Carry blood to the renal vein

Question 21

Function of the Proximal convoluted tubule

Answer 21

Selectively reabsorbs useful substances by active transport
+ Reabsorbs ALL glucose and aa’s
+ Reabsorbs 80% of water and Na and other minerals

Question 22

How is glucose reabsorbed in the proximal convoluted tubule?

Answer 22

+ Co-transported out of the filtrate and into fluid outside tubule = by co-transporter proteins in the outer membrane of the tubules
+ Na+ ions = move down the conc. grad. from outside the tubules into the tubules cell
→ providing energy for glucose to move at the same time to fluids outside tubule
same process used to reabsorb aa’s

Question 23

How are Na+ ions reabsorbed from the kidney in the proximal convoluted tubule?

Answer 23

+ Move by active transport from filtrate to space outside tubule
→ Then, pass to peritubular capillaries
+ pump proteins = located in outer membrane of tubules

Question 24

How are Cl- ions reabsorbed from the kidney in the proximal convoluted tubule?

Answer 24

+ attracted from filtrate to space outside tubule cuz charge grad. set up by active transport of Na+ ions

Question 25

How is water reabsorbed from the proximal convoluted tubule?

Answer 25

+ Pumping solutes out of filtrate and into the fluid outside the tubules creates a solute conc. grad.
→ causing water to be reabsorbed from filtrate by osmosis