bio 1002 Osmoregulation and Excretion

Osmoregulation

The process by which animals :

control solute regulation

balance water gain and loss

partial pressure facilitates diffusion of oxygen

Osmolarity

number of moles of solute per litre of solution

Mammal blood osmolarity

300 mOsm/L

Seawater osmolarity

10000 mOsm/L

Hyperosmotic

solution with higher concentration of solutes

Hypoosmotic

solution with lower concentration of solutes

Osmoconformer

lets water flow freely in and out of its body

Internal osmolarity = external osmolarity

Osmoregulators

Keeps internal osmolarity constant

Osmoregulation balances the update and loss of __

water and solutes

Osmoregulation is based largely on controlled movement of__

solutes between internal fluids and the external environment

The driving force for movement of solutes and water is __

a concentration gradient of one or more solutes across the plasma membrane

***Stenohaline

Very sensitive to changes in external osmolarity

***Euryhaline

Can tolerate large fluctuations in external osmolarity

Marine (salt water) environments

Many marine invertebrates are osmoconformers

Many marine vertebrates are osmoregulators

For osmoregulators the marine environment is a dehydrating environment

For osmoregulators the marine environment is a __environment

dehydrating

osmoregulation in a marine fish

osmoregulation in freshwater fish

Salt vs. freshwater

salt:

 Constantly lose water by osmosis

 Drink seawater – intake of salts

 Salts removed via gills and kidneys

 Have very minimal urine

fresh:

 Osmotic gain of water

 Drink very little

 Take up salts via food/gills

 Have very dilute urine

Diadromy (watch lecture capture)

Smoltification

physiological and anatomical changes to the osmoregulatory system

Dehydration in land animals (lecture capture)

Specialized cells

Transport epithelia – one or more layers of epithelial cells that are specialize for moving particles (solutes) in a specific direction

Can face the outer environment in organisms with simple body plans

Can line channels that lead to an opening

E.g., nasal ducts in sea birds

An animal’s nitrogenous wastes reflect its __

phylogeny and habitat.

The type and quantity of an animal’s waste products may greatly affect its __

water balance

Among the most significant wastes are __

nitrogenous breakdown products of proteins and nucleic acids

Some animals convert toxic__ to less toxic compounds prior to excretion

ammonia (NH3)

What is the waste product

Mostly a byproduct of breakdown of proteins and nucleic acids

Nitrogenous molecules

Ammonia (NH3) is very toxic → NH4+ interferes with biochemistry of the body

ammonia

Directly produced waste

Only used in animals which excrete directly into surroundings

e.g., bony fish

urea

Requires ATP and enzymes

Has to be dissolved in water; so causes water loss

e.g., mammals, amphibians

uric acid

Requires even more ATP and enzymes

Conserves water

e.g., birds, reptiles, insects

****key steps to the excretory system

1. Filtration: driven by blood pressure. Large cells in blood cannot go through membrane, but water and small solutes can (→ filtrate)

2. Reabsorbtion: a selective process (facilitated by epithelium via active transport) recovers useful molecules from the filtrate and passes them into the blood

3. Secretion: Nonessential molecules left in the filtrate OR actively transported out of the blood

4. Excretion: Processed filtrate is released from the body as urine

Variations across taxa

Protonephirdium

Metanephridia

Malpighian tubules

Protonephirdium

network of dead-end tubules connected to external openings

dilute urine

Metanephridia

tubules that collect coelomic fluid and produce dilute urine for excretion

dilute urine

Malpighian tubules

remove nitrogenous wastes from hemolymph

dry waste (uric acid)

The human kidney - structure

Renal cortex – outer layer of kidney Renal medulla – inner layer of kidney

Renal artery – brings blood that requires filtration to the cortex and medulla

Renal vein – takes filtered blood and recovered substances to the rest of the body

Renal pelvis – collects waste fluid as urine, and carries it out of the kidney (through ureter)

How big is a kidney?

10 cm (length of a popsicle stick)

The nephron

The nephron is organized for stepwise processing of blood filtrate

Filtrate contains salts, glucose, amino acids, vitamins, nitrogenous wastes, other small molecules

How many nephrons are in one kidney?

1 million

How much blood flows through your kidneys daily?

1600 L

85% of the nephrons are __

cortical (short)

15% of the nephrons are

The rest are juxtamedullary – essential for water conservation – produces urine that is hypoosmotic to body fluids

Glomerulus

ball of capillaries branching from the afferent arteriole

Bowman’s capsule

a swollen end of the tube system that surrounds the glomerulus

Filtrate

is formed when the blood pressure forces fluid component from blood into the lumen of Bowman’s capsule

Filtrate passes through the proximal tubule, the loop of Henle, and the distal tubule.

Reabsorption happens in the __

proximal tubule, the loop of Henle, and the distal tubule.

The distal tubule empties into __, which empties into the __, and from there to the __

a collecting duct , renal pelvis , ureter

describe kidney function (lecutre capture)

Ascending limb is __to water

impermeable

As filtrate travels through the nephron, osmolarity __along the descending arm of the loop of Henle

increases

Which nephron is from a desert animal?

how are bats adapted with their kidneys

Vampire bat drinks blood at night – so much volume that it gets too heavy to take off and fly back to roost.

Solution – excrete large volumes of very dilute urine as you feed

At night – processing proteins in the blood creates large quantities of urea, but they do not have drinking water in the cave to dilute it.

Solution – excrete highly concentrated urine

Main hormone regulating osmotic balance is __

antidiuretic hormone (ADH)

another word for antidiuretic hormone (ADH)

vasopressin

ADH signals are triggered by __

osmolarity of blood

what facilitate reabsorption of water

ADH sends signals to receptor molecules on the membrane of the collecting duct

blood osmolarity loop

label