Chpt 44 Excretory System osmoregulation

I. Osmoregulation – *management of the body’s water content & solute concentration *absorption & excretion of H 2 O & solutes so that water balance & osmotic pressure are maintained -- homeostasis

A. Types 1. Marine Fish –a. fish body is hypotonic/hypoosmotic = less dissolved solutes in body than in water envr. – b. SO, water is constantly lost through osmosis 1) marine fish must constantly drink & RARELY urinate – the urine is very concentrated 2) secrete excess salt out through gills

2. Fresh water fish a. body is hyperosmotic/hypertonic to envr. – more dissolved solutes IN body than in water envr. b. SO, water is constantly GAINED –1) fresh water fish RARELY drink & constantly urinate – urine very dilute –2) absorb salt through gills

3. Urine – NH 3 is the waste product from the breakdown of amino acids a. aquatic orgs – NH 3 or NH 4 + very concentrated but dilutes quickly in the water envr. b. birds – convert urea to uric acid (highly toxic) that’s insoluble in water so it comes out mostly solid w/ the feces (but it’s energy expensive) –1) this allows bird embryos in the egg to separate their wastes into a separate sack (allantois) so they aren’t “swimming” in their wastes!

c. mammals- convert NH 3 to urea in liver – this requires less water to excrete since it’s less toxic than NH 3

II. Excretory Mechanisms A. Contractile Vacuoles –1. found in protists – paramecium –2. accumulates excess water then merges w/ cell membrane & releases the H 2 O to the envr.

B. Flame Cells (protonephridia) –1. found in flatworms/platyhelminthes – planaria –2. branched system of tubes w/ cilia-containing cells at end of each tube a. cilia move waste fluids through tubes & out a series of pores along sides of body

C. Malpighian Tubules 1. found in insects/arthropods 2. tubes in dig. tract collect body fluids –a. the materials to be kept are reabsorbed & the wastes pass out through the anus

D. Nephridia (metanephridia) 1. found in annelids/segmented worms 2. ciliated funnel system – as fluids travel through the funnel some liquid is reabsorbed so wastes become more concentrated then are excreted out pores along sides of body

E. Kidney 1. found in vertebrates 2. made of 1 million filtering tubes called nephrons –a. wastes pass from kidney  ureter  bladder  urethra then out of the body

medulla Cortex ureter

Normal kidney angiograph

III. Human Kidney A. Know anatomy!! –1. cortex – medulla - renal pelvis –2. nephron

Cell produces metabolic wastes Wastes picked up by blood stream Kidney filters blood & removes wastes

How are cytoplasm, interstitial fluid, blood plasma, and urine related?

B. Physiology 1. Filtration –a. blood enters through renal artery which branches into capillaries of the glomerulus almost immediately –b. this greatly increases pressure –c. water & dissolved substances are forced out of capillaries & in to Bowman’s capsule (leaving the rbc’s, wbc’s, platelets, large proteins & some plasma in the vessels)

2. Secretion –a. as the filtrate passes through the proximal (& later distal) tube some more interstitial fluid enters in (it is secreted into the tube by both active & passive transport)

3. Reabsorption –a. as filtrate goes DOWN through loop of Henle it becomes more concentrated due to the movement of water OUT of the tube –b. as the filtrate goes UP through the loop of Henle is becomes more dilute due to salts moving OUT of the tube –c. as it moves DOWN the collecting duct it again becomes more concentrated -----urine

IV. Excretory System Control A. Hormones –1. ADH – antidiuretic hormone – controls urine volume a. ADH ↑ - increases the reabsorption of H2O by causing the collecting duct to become MORE permeable to water --so more water is reabsorbed –urine becomes more concentrated & less water is released from body

B. Aldosterone – increases both reabsorption of water & Na+ by increasing the permeability of the distal convol. tube & collecting duct to Na + (so more Na + is reabsorbed) the water moves passively in with the Na +

Uric Acid stone Calcium oxalate & blood Limit stones by drinking water and limiting caffiene