1. 11.3 The Kidney

2. Excretion
All organisms produce waste in the process of metabolism. If the waste is allowed to accumulate, it will cause a problem for the organism
Excretion: is the process of removing waste products of metabolic processes.

3. Osmoregulation
Osmoregulation: a form of homeostasis where the concentrations of hemolymph or blood is kept within a particular homeostatic range.
HEMOLYMPH: the circulating fluid in arthropods
Arthropods are insects, crustaceans, and arachnids
Animals with jointed legs, segmented bodies, and chitin exoskeletons

5. Osmoregulators vs Osmoconformers
OSMOREGULATORS: animals that maintain a constant internal solute concentration
Includes all terrestrial animals, freshwater animals, and some marine organisms such as bony fish
OSMOCONFORMERS: animals whose internal solute concentration tends to be the same as the concentration of solutes in the environment
Most marine invertebrates

7. Estuary: Where the river flows to the sea

8. An osmoconformer

9. Summary of metabolic wastes….

10. Large Intestine – removes waste from the digestive system
Liver- transforms toxins such as alcohol, drugs, heavy metals and products of protein metabolism into soluble compounds that can be eliminated by the kidneys

11. The Kidney and Urinary System
Humans have 2 kidneys, located low in the abdominal cavity

13. Expectation: Draw and label the human kidney.
See page 487

14. Function of Urinary System
remove waste, balances blood pH, and maintains water balance.
The average adult loses ~2L of water every day through urine, perspiration, and exhaled air – and even more under physical activity.
To maintain water balance, adults should drink ~2L of fluids (~8 glasses) daily to replenish lost water.

15. Urine and Dehydration
In reality, your urine should be a pale yellow and not have a strong ammonia order.
If it is very concentrated, and a darker, deeper yellow you are likely dehydrated and not getting enough water.
What are some signs of dehydration?

16. Nitrogenous Waste
Proteins are very important in your diet because they maintain tissues, promote cell growth, and direct cell processes
Excess proteins are often converted into carbohydrates (and then broken down for ATP energy).
Unlike proteins, carbohydrates don’t have nitrogen – so the nitrogen component is a waste component that needs to be removed from your body.

17. Nitrogenous Wastes
During deamination (break down of proteins), ammonia (NH3) is formed.
Ammonia is toxic – even in small amounts
In the liver, ammonia combines with CO2 to produce UREA which is much less toxic.
Uric acid is also produced (from breakdown of nucleic acids).
Both are released in urine.

20. Urinary System – Basic Summary
Blood flows to the kidneys (via the renal artery)
Wastes are filtered from the blood by the kidneys (the filtered blood leaves the kidneys via the renal vein)
These waste products form urine.

21. Urine leaves the bladder via the urethra
Urine leaves the kidney via the ureter and goes to the bladder for temporary storage
When the bladder is full, a signal is sent to the brain (to give you the urge to urinate)
Urine leaves the bladder via the urethra

22. The Nephron
The functional unit of the kidney is a slender tubule called a nephron
There are ~ 1 million nephrons in a single kidney.
Urine is formed inside the nephron

23. ~1 million slender tubules called NEPHRONS make up the kidney

25. Fluid Flow through the Kidneys
Blood is brought to the kidneys via the renal artery
The renal artery branches into the afferent arterioles
The afferent arterioles branch into a capillary bed called the glomerulus

27. Blood leaves the glomerulus via the efferent arterioles
Blood then flows through the peritubular capillaries (which are entwined around the nephron) and joins a venule and then the renal vein to leave the kidney (and eventually return back to the heart for recirculation)

28. The glomerulus is surrounded by a portion of the nephron called the Bowman’s Capsule.
Here, fluids that will be processed into urine enter the Bowman’s capsule from the blood.

29. Fluids then flow through a thinner tubule called the proximal tubule to the loop of Henle to the distal tubule to the collecting ducts where urine from many nephrons merge.
The collecting ducts all merge at the renal pelvis which delivers urine to the ureter

31. FORMATION OF URINE Includes: filtration, reabsorption, and secretion
FILTRATION: fluids moved from the blood to the bowman’s capsule.
(Also referred to as *ultrafiltration)

32. Too large to diffuse through the walls of the glomerulus
Too large to diffuse through the walls of the glomerulus. Only smaller molecules can pass through.
*NOTE: This does NOT include all filtered materials

33. Filtration
Pretty much any solute that is small enough to fit through the pores of the glomerulus will be filtered.
This also includes toxins and other substances that are ingested and absorbed but not fully metabolized (such as drugs)

34. Reabsorption
REABSORPTION: Transfer of essential solutes and water from the nephron back to the blood.
~600mL of fluid flows through kidneys every minute
20% or ~120mL is filtered into the nephrons.
If none of that was reabsorbed, you would form 120mL of urine every minute.

35. Reabsorption
In reality, about 119mL is reabsorbed and 1mL of urine is formed (for every 120mL)
Active and passive transport are both used.
Numerous mitochondria in the surrounding cells provide energy for active transport.
Reabsorption occurs until the threshold level of a substance is reached (homeostasis).
Excess NaCl remains in the nephron to be excreted with urine

36. * A note on Reabsorption….
NOTE: Since blood should always be within homeostasis ranges, even before coming to the kidney, many of the solutes the are filtered into the nephron will be fully reabsorbed. Such as sugar.
But if your body isn’t able to properly maintain homeostasis, there may be an excess of a solute for the kidney to remove from the blood. (Ex: Untreated diabetes and sugar)
Since toxins should not be in the blood there are no “homeostatic ranges” for them and they should not be reabsorbed.

37. Secretion
SECRETION: movement of materials from the blood into the nephron (at locations other than the Bowman’s capsule)
These are wastes such as nitrogen-containing wastes, excess H+ ions, minerals (K+), drugs
Cells with lots of mitochondria line the distal tubule to provide energy for active transport.

38. Animals and the Type of Nitrogenous Wastes
The majority of nitrogenous waste in mammals is in the form of urea.
Aquatic organisms such as fish, echinoderms or coelenterates excrete the waste directly as ammonia as it can be easily diluted within their environment.

39. Echinoderms
Show radial symmetry
Sea urchins, star fish, sea cucumbers

40. Coelenterates (Cnidaria)
Have a tube or cup shaped body, and single opening with tentacles
Includes jelly fish, coral

41. Nitrogenous Wastes in Other Animals
For insects it is in the form of uric acid.
Insects have tubes that branch off from their intestines known as Malpighian Tubules

42. Malpighian Tubule System

43. Malpighian Tubule System
Cells lining the tubules actively transport ions and uric acid from the hemolymph into the lumen of the tubules
Water follows (because of osmosis!)
The tubules empty their contents into the gut
In the hindgut, most of the water and salts are reabsorbed and nitrogenous waste (uric acid) is excreted with feces.
Pg 487