11.3 The kidney and osmoregulation Flashcards
What is excretion?
The removal from the body of the waste products of metabolic activity
What are the two key6 functions an excretory system performs?
- removes nitrogenous wastes that may be toxic to the body in large concentrations
- removes excess water to maintain osmolarity in the body
How are nitrogenous wastes produced?
From the breakdown of nitrogen containing compounds - amino acids/nucleotides
Why must excess levels of nitrogenous waste be eliminated from the body?
Nitrogenous wastes are toxic to the body
What is correlated with the evolutionary history of the animal and the habitat?
Type of nitrogenous waste in animals
What do most aquatic animals eliminate their nitrogenous waste as?
Ammonia
Why can ammonia be effectively flushed by animals in aquatic habitats?
As it is water soluble
How do mammals eliminate their nitrogenous waste as ?
Urea
How are nitrogenous waste eliminated from reptiles and birds?
Uris acid
What is a downside of Uris acid?
Requires more energy to make
What is a downside of Uris acid?
Requires more energy to make
What are the good things about Uric acid?
relatively non toxic and requires less water to flush
Why are water levels constantly changing?
As a result of metabolic activity
How is water produced?
Via condensation reactions
How is water consumed?
During hydrolysis reactions
What will impact tissue viability?
The concentration of water within cells
What are the two types of animals in accordance to how they manage their internal osmotic conditions?
Osmoconformers or osmoregulators
What are osmoconformers?
Osmoconformers maintain internal conditions that are equal to the osmolarity of their environment
What are osmoregulators?
Osmoregulators keep their body’s osmolarity constant regardless of environmental conditions
By matching osmotic conditions to the environment, what do osmoconformers minimise?
Water movement in and out of cells
What is a more energy intensive process, Osmoconformers and osmoregulators?
Osmoregulation
What are osmoconformers affected by?
Environmental conditions
In mammals is the excretory system separate from the digestive system of the animal?
Yes
In insects, is the excretory system separate from the digestive system?
No it is connected
What is the excretory system in insects?
Malpighian tubules
What is the hemolymph in insects?
A circulating fluid system
Where do Malpighian tubules branch off from?
The intestinal tract
What do Malpighian tubules actively uptake and from where?
Nitrogenous wastes and water from the hemolymph
Where and why do the Malpighian tubules pass the materials onto?
The gut to combine with the digested food products
What are reabsorbed into the hemolymph?
Solutes, water and salts
Where are materials reabsorbed into the hemolymph?
At the hindgut
In insects, where are nitrogenous wastes and undigested food materials excreted?
Via the anus
What do the kidneys function as?
The bloods filtration and water balancing system
What does the kidneys remove?
Metabolic wastes for excretion
How does blood enter the kidneys?
Via the renal artery
How does blood exit the kidney?
Via the renal vein
What filters the blood?
Nephrons
What do nephrons produce?
Urine
How is urine transported from the kidneys?
Via the ureter
Where is urine store prior to excretion?
Bladder
What filters the blood and eliminates wastes?
Nephrons
What will the blood in the renal vein have in comparison to the renal artery?
- less urea
- less water and solutes/ions
- less glucose and oxygen
- more carbon dioxide
Will the blood in the renal artery be different to the blood in the renal vein?
Yes
What is the functional unit of the kidney?
The nephron
What are the four components of the nephron?
- bowman’s capsule
- proximal convoluted tubule
- loop of Henle
- distal convoluted tubule
What us the bowman’s capsule?
First part of the nephron where blood is initially filtered from to form filtrate
What is the proximal convoluted tubule?
Folded structure connected to the bowman’s capsule where selective reabsorption occurs
What is the loop of Henle?
A selectively permeable loop that descend into the medulla and establishes a salt gradient
What is the distal convoluted tubule?
A folded structure connected to the loop of Henle where further selective reabsorption occurs
How does the blood to be filtered enter the bowman’s capsule?
Via an afferent arteriole
How does the blood leave the bowman’s capsule?
Via an efferent arteriole
Where is the blood filtered within the bowman’s capsule?
The glomerulus
What does the efferent arteriole form?
A blood network called the vasa recta
What does the vase recta do?
Reabsorbs components of the filtrate from the nephron
What does each nephron connect to?
A collecting duct
How does each nephron connect to a collecting duct?
Via the distal convoluted tubule
What does collecting duct feed into?
The renal pelvis
Why are collecting ducts not considered to be a part of a single nephron?
The collecting ducts are shared by nephrons
What is the function of nephrons?
To filter blood and then reabsorb useful materials from the filtrate before eliminating the remainder as urine
What are the three stages of the functions of the nephrons?
Ultrafiltration
Selective reabsorption
Osmoregulation
How does the nephron do ultrafiltration?
Blood is filtered out of the glomerulus at the bowman’s capsule to form filtrate
How do the nephrons do the selective reabsorption?
Usable materials are reabsorbed in convoluted tubules
How does the nephron do Osmoregulation?
The loop of Henle establishes a salt gradient, which draws water out of the collecting duct
What is the order of processes in nephron functions alongside the specific structures?
Bowman’s capsule - ultrafiltration
Proximal tubule - selective reabsorption
Loop of Henle - Osmoregulation
Distal tubule - selective reabsorption
Collecting duct - osmosregulation
What is ultrafiltration?
The first of three processes by which metabolic wastes are separated from the blood and urine is formed
What is the non-specific filtration of the blood under high pressure?
Ultrafiltration
Where does ultrafiltration occur?
In the bowman’s capsule
What does the bowman’s capsule encapsulate?
The glomerulus
What is the inner surface of cells of the bowman’s capsule called?
Podocytes
What are the cellular extensions of Podocytes called?
Pedicels
What do pedicels do?
Wrap around the blood vessels of the glomerulus
What is between the Podocytes and the glomerulus?
A glycoprotein matrix called the basement membrane
What does the basement membrane do?
Filters the blood
How can blood freely exit the glomerulus?
Glomerular blood vessels are fenestrated (have pores)
What does the gaps in the Podocytes between their pedicels allow?
For fluid to move freely into the nephron
What is the sole filtration barrier within the nephron?
The basement membrane
What does the basement membrane restrict?
The passage of blood cells and large proteins
Why does the basement restrict the passage of blood cells and large proteins?
It is size selective
When the blood is filtered what does filtrate formed not contain?
Any blood cells
Platelets
Plasma proteins
How does ultrafiltration optimise filtration?
As it involves blood being forced at high pressure against the basement membrane
How does the glomerulus create a high hydrostatic pressure?
By having a wide afferent arteriole and a narrow efferent arteriole
Is it easier for blood to enter or exit the glomerulus?
Enter
What does the fact that blood is easy to enter but difficult to exit the glomerulus increase?
Pressure within the glomerulus
What increases the glomerulus surface area available for filtration?
How the glomerulus forms extensive narrow branches
What does the net pressure gradient within the glomerulus force?
Blood into the capsule space
What does selective reabsorption involve the reuptake of?
Useful substances from the filtration
Where does the majority of the selective reabsorption occur?
In the proximal convoluted tubule
What does the proximal convoluted tubule have to increase the surface area for material absorption from the filtrate?
A microvilli cell lining
How thick is the tubule?
SIngle cell thick
How is the tubule connected by?
Tight junctions
What do the tight junctions function to create?
A thin tubular surface with no gaps
Why is there a large number of mitochondria within the tubule cells?
As reabsorption involves active transport
Where are substances actively transported?
Across the apical membrane
What is the apical membrane?
Membrane of the tubule cells facing the tubular lumen
In selective reabsorption where do substances passively diffuse across?
The basolateral membrane
What is the basolateral membrane?
Membrane of tubule cells facing the blood
What do the tubules reabsorb?
All glucose, amino acids, vitamins, hormones, water and most mineral ions
How are mineral ions and vitamins transported?
By protein pumps and carrier proteins
How are glucose and amino acids transported across the apical membrane?
Co-transported with sodium
How does water follow the movement of the mineral ions?
Passively via osmosis
What is Osmoregulation?
The control of the water balance of the blood, tissue or cytoplasm of a living organism
Where does Osmoregulation occur?
In the medulla of the kidney
What are the two key events of Osmoregulation?
- Loop of Henle establishes a salt gradient in the medulla
- ADH regulates the level of water reabsorption in the collecting duct
What is the function of the loop of Henle?
To create a hypertonic concentration in the tissue fluid of the medulla
What is the descending limb of the loop of Henle permeable to?
Water but not salts
What is the ascending limb of they loop of Henle permeable to?
Salts but not water
As the loop descends into the medulla what will the interstitial fluid become?
More salty and hypertonic
In what direction does the vasa recta blood network that surrounds the loop of Henle flow?
In the opposite direction
How does the counter current of the vasa recta further establish a salt gradient?
It helps salt released from the ascending limbs are drawn down into the medulla
What do the hypertonic conditions of the medulla draw out and how?
Water by osmosis
When is water drawn out by osmosis in water reabsorption?
As the collecting duct passes through the medulla
What controls the amount of water released from the collecting ducts and retained by the body?
ADH
When is ADH released?
In response to dehydration
Where is ADH released from?
The posterior pituitary
What detects dehydration?
Osmoreceptors in the hypothalamus
How does ADH increase the permeability of collecting duct to water?
By upregulating production of aquaporins
What does the upregulation of aquaporins mean?
Less water remains in the filtrate
Urine becomes concentrated and the individual urinates less
What happens to an individuals ADH levels that is suitably hydrated?
ADH levels decrease and less water is reabsorbed
How to remember when ADH is produced?
ADH is produced when you Are DeHydrated
What cannot be maintained if water levels drop or increase without regulation?
Homeostasis
What is dehydration?
A loss of water from the body such that body fluids become hypertonic
What will happen when an individual is dehydrated?
They will experience thirst
excrete small amounts of heavily concentrated urine
Blood pressure will drop and heart rate increases
Become lethargic and unable to lower body temperature
What is overhydration?
When the over-consumption of water makes body fluids hypotonic
What will individuals do in an effort to remove water from the body?
Produce excessive quantities of clear urine
What will hypotonic body fluids cause cells to do?
Swell which can cause cell lysis and tissue damage
What symptoms can overhydration cause?
headaches and disrupted nerve functions
What will animals in desert environments need more of than animals in moist environments?
More efficient water conservation
How can water conversation be improved by having?
A longer loop of henle
What does having a longer loop of henle increase?
The salt gradient in the medulla
What does a greater salt gradient in the medulla mean more of?
More water is reabsorbed by the collecting ducts and urine is concentrated
What is positively correlated with the degree of water conservation in animals?
The length of the loop of henle
Describe the loops of henle in animals living in moist environments?
Short loops of henle that don’t descend deeply into the medulla
Describe the loops of henle in animals living in arid environments?
Long loops of henle that descend deeply into the medulla
What type of nephrons will animals in moist environments have?
Cortical nephrons
What type of nephrons will animals in arid environments have?
Juxtamedullary nephrons
What will individuals with kidney diseases demonstrate?
A reduced glomerular filtration rate
What do kidneys prevent?
The excretion of blood cells and proteins as well as glucose
What materials can be used as an indicator of disease if present in urine?
Glucose
Proteins
Blood cells
Drugs/toxins
What does the presence of glucose in urine indicate?
Diabetes
What does the presence of proteins in urine indicate?
Disease or hormonal conditions
What does the presence of blood cells in urine indicate?
A variety of diseases, infections and cancer
What is kidney dialysis?
The external filtering of blood in order to remove metabolic wastes in patients with kidney failures
In dialysis what is blood pumped through?
A dialyzer
What are the two key functions of dialyzers that are common to biological membranes?
- contains a porous membrane that is semi-permeable
- introduces fresh dialysis fluid and removes wastes to maintain an appropriate concentration gradient
How often is kidney dialysis treatment?
3 times a week and for 4 hours
What is the best long term treatment for kidney function?
Kidney transplant
What must happen in order to minimise the potential for graft rejection?
Donors must typically be a close genetic match
How is the transplanted kidney grafted into the abdomen?
With arteries, veins and ureter connected to the recipients vessels
Can you survive with just one kidney?
Yes
