Chapter 11.3 - The Kidney and Osmoregulation Flashcards
How do insects do osmoregulation?
+ 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
Blood capillaries
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
Why does in the Glomerulus the volume forced out of the capillaries 100x more than in other tissues? (Glomerulus Filtrate)
+ Pressure particularly HIGH and capillary walls = part. permeable
Ultrafiltration
Separation of particles differing in size by a few nanometres
What are the 3 parts of the Ultrafiltration site?
1) Fenestrations
2) Basement membranes
3) Podocytes
Fenestrations
Between the walls of the capillaries
→ allow fluid to escape but NOT bl. cells
Basement membrane
+ 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
Podocytes
+ 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
Nephron
Basic functioning unit of a Kidney
Bowman’s capsule
Cup-shaped w/ high porous inner walls = collects the fluid filtered from the blood
Proximal Convoluted tubule
Highly twisted section of the nephron
→ w/ cells in the walls having many mitochondria and microvilli projecting into the lumen of the tube
Loop of Henle
Carries filtrate deep into the medulla (descending limb)
→ carries back up to the cortex (ascending limb)
Distal convoluted tubule
Highly twisted
→ FEWER and SHORTER microvilli
→ Fewer mitochondria
Collecting Duct
Wider tube carries filtrate back through the cortex and medulla to renal pelvis
Afferent Arteriole
Blood from renal artery
Glomerulus
Tight-knot like, high pressure capillary bed = site of blood filtration
Efferent Arteriole
Narrow vessels = restricts blood flow = help gen high pressure in Glomerulus
Peritubular capillaries
Low pressure capillary bed that runs around convoluted tubules = absorb fluid from them
Vasa Recta
Unbranched capillary
= similar to shape and size of Loop and Henle
+ Descending in the Medulla
+ Ascending in the Cortex
Venules
Carry blood to the renal vein
Function of the Proximal convoluted tubule
Selectively reabsorbs useful substances by active transport
+ Reabsorbs ALL glucose and aa’s
+ Reabsorbs 80% of water and Na and other minerals
How is glucose reabsorbed in the proximal convoluted tubule?
+ 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
How are Na+ ions reabsorbed from the kidney in the proximal convoluted tubule?
+ Move by active transport from filtrate to space outside tubule
→ Then, pass to peritubular capillaries
+ pump proteins = located in outer membrane of tubules
How are Cl- ions reabsorbed from the kidney in the proximal convoluted tubule?
+ attracted from filtrate to space outside tubule cuz charge grad. set up by active transport of Na+ ions
How is water reabsorbed from the proximal convoluted tubule?
+ 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
