Chpt 44 Excretory System osmoregulation

I. Osmoregulation – *management of the body’s water content & solute concentration*absorption & excretion of H2O & 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 – NH3 is the waste product from the breakdown of amino acids

• a. aquatic orgs – NH3 or NH4+ 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 NH3 to urea in liver – this requires less water to excrete since it’s less toxic than NH3

II. Excretory Mechanisms• A. Contractile Vacuoles

– 1. found in protists – paramecium

– 2. accumulates excess water then merges w/ cell membrane & releases the H2O 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

medullaCortex

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