Osmoregulation and Urinary system

Functions of the osmoregulation

• regulating balance of water and ions in body fluid

• removing metabolic wastes

Osmolarity

total concentration of solutes in solution

Osmosis

movement of water across a membrane from low concentration of solute to a high concentration of solute across a membrane

Hypotonic

low concentration of solute

hypertonic

higher solute solution

lyse/turgid

solution is in a hypotonic solution (more water is moving in the cell

Shriveled/Plasmolyzed

in a hypertonic solution because the water is leaving

simple diffusion

where the molecules moves directly across the membrane down a concentration gradient

facilitate diffusion

uses protein channel to move molecules across a membrane down a concentration gradient

active transport

requires (atp) to move across a low-high concentration gradient

Osmoconformers

(conform to environment)

• body isotonic to seawater

• marine invertebrates and hagfish

Osmoregulators

(maintain constant osmolarity different from environment)

• most vertebrates

Marine vertebrates, freshwater vertebrates, and terrestrial vertebrates and what do they gain/lose?

Marine: Hypertonic, excess ions; will lose water, reabsorption of water

Freshwater: Hypotonic, ion deficit; will gain water, reabsorption of ions

Terrestrial: will lose water relative to environment, reabsorption of water

Nitrogenous wastes

• metabolic wastes complicate osmoregulation

• metabolism of proteins and nucleic acids produce ammonia (NH3)

  • very toxic to cells

  • must be highly diluted, or converted

    • aquatic animals can dilute

Ammonia

• is eliminated directly

• most fish, aquatic, invertebrates

  • highly toxic

  • high water requirement

  • low energy cost

Converted to urea

• mammals, amphibians, sharks

• far less toxic

• medium water requirement

Uric acid

• reptiles, birds, insects

• high energy cost

• low water requirement

Osmoregulation processes

1. Filtration of body fluid

2. Reabsorption

3. Secretion

4. Excretion of waste

reabsorption

moving molecules from filtrate back into body fluid

secretion

moving molecules from body fluid directly into filtrate

protists and sponges

contractile vacuoles pump water out

Flatworms

• Protonephridia

• body fluid drawn into flame bulbs

• water and ions reabsorbed

• pores for excretion

Protonephridia

tubules open only to outside body

Annelids

• metanephridia

• Nephrostomes

• ions reabsorbed

• hypotonic urine

Metanephridia

tubules open to body and outside

Nephrostomes

filtration funnels

insects

• Malpighian tubules- extensions of

  digestive tract

• wastes and ions secreted in

• water follows

• water and ions reabsorbed in hindgut

• wastes excreted with feces

Vertebrate Osmoregulatory Organs

kidney

• filters blood under pressure into tubules

• nephron - functional unit of kidney

• selective reabsorption

bony fishes

• use gills to excrete ammonia

Freshwater

• large glomeruli, shorter tubules

• reabsorb ions, excrete water

• ions obtained through gills

• hypotonic urine

marine

• small glomeruli, long tubules

• reabsorb water, excrete ions

• drink large amounts

• isotonic urine

Cartilaginous fishes- sharks

• reabsorb urea from nephron

• urea keeps body nearly isosmotic with seawater

• adaptions to tolerate high urea

Amphibians

• same kidney as freshwater fish

• ions transported through skin

• excrete ammonia in water, urea on land

Reptiles

• Freshwater: similar to freshwater fish

• Marine: similar, but drink seawater

  • Excrete ions through salt glands

• Terrestrial: reabsorb both ions and water

  • Uric acid to retain water

Birds and mammals

• produce hypertonic urine

• loop of Henle allows greater water reabsorption

  • Loop of Henle maintains high osmolarity gradient by countercurrent system

• longer loop —> more concentrated urine

• Mammals have combination of short and long loops for more H2O reabsorption and produce hypertonic urea.

  
  

Brids have short loops why?

• uric acid helps

• salt glands in seabirds

• Birds short loop produce uric acid to preserve water.

Nephron function

• active transport of ions out of filtrate

• water follows, is reabsorbed

• more water reabsorbed in loop of henle, collecting duct

Kidney also

• regulate electrolyte balance in blood

• maintain pH homeostasis

What benefit does the loop of Henle provide?

Maintains concentration gradient by using countercurrent exchange. Extra reabsorption of water, solutes to make hypertonic urine. Excrete more waste while minimizing water loss