Chapter 7 - Kidneys Flashcards
Why are fluctuations in homoeostasis dangerous?
They can disrupt biochemical activities and large fluctuations can kill the cells
What is homoeostasis?
The maintenance of a constant internal environment
What four internal features must be kept constant?
Chemical composition – blood pH ranging from 7.35 to 7. 45 – osmotic pressure, Osmo regulation – temperature
What are effectors?
Things that change in response to stimuli in order to correct and achieve homoeostasis
Name some of the response mechanisms that change in the body to correct temperature?
Blood vessels constrict or dilate – sweat produced – piloerection – shepherding thermogenesis
What does it mean if one solution is hyperosmotic to another?
Hyper osmotic – means the solution contains more solutes than other solution it therefore contains less water
What does it mean if one solution is hypoosmotic to another?
It means it contains less solutes than the other solution therefore contains more water
Define osmolarity
The number of osmoles solute per litre of solution
Name the three important regulatory functions of the kidney
Removal of nitrogenous waste –
regulation of water content of the body – regulation of salt balance, sodium, potassium, chlorine, magnesium, calcium this is known as ionic regulation
What three ways can ammonia be excreted?
As ammonium, urea and you uric acid
Describe the toxicity levels from high to low for ammonia, Urea and uric acid
Ammonia high - urea low - uric acid very low
Describe the solubility for ammonia, urea, Uric acid
Ammonia has high solubility levels, urea has a low solubility levels, uric acid is almost not soluble
Describe the metabolic cost for ammonia, urea, uric acid – from high to low
Ammonia has no metabolic cost
Urea has some metabolic cost
Eurich acid has a high metabolic cost
What animals would have ammonia in the form of nitrogenous waste?
Fish or aquatic animals
What animals with have urea in the form of nitrogenous waste?
Mammals, adult terrestrial amphibians
What animals would have uric acid in the form of the nitrogenous waste,
birds and insects
What percentage of the bodyweight are the kidneys?
1%
What did juxtamedullary nephrons mean
Urine is very concentrated
What are the two types of nephrons?
Cortical and juxtamedullary
What does cortical nephrons mean?
Less concentrated urine
What percentage of nephrons are cortical and juxtamedullary and humans?
85% are cortical and 15% of juxtamedullary
What animals have both juxtamedullary and cortical nephrons?
Birds and mammals
What animals contain only cortical nephrons?
Reptiles and amphibians
How does fluid escape Bowmans capsule?
It moves by the process of ultrafiltration – the hydrostatic pressure of the blood plasma a.k.a. blood pressure forces fluid and solutes through the glomerular capillaries into Bowmans capsule
What type of energy process as the movement of fluid out of the Bowmans capsule?
It is a passive process therefore no energy is required
What can pass freely into Bowmans space?
Anything less than 1.8 nm filter freely – water, glucose, urea, amino acids
What is able to filter list file into Bowman space?
Anything between 1.8 to 4. 2 nm
What molecules do not filter through Bowman space?
Anything larger than 4. 2 nm
What prevents the movement of large molecules through the capillaries?
The pores in endothelium range between 50 to 200 nm wide – podocyte split pores size are also 4 nanometres wide
What Are podocyte split pores?
They determine what can pass into bowmans space
Define glomerular filtration rate
the amount of fluid filtered into the kidney tubules per minute
How many litres of blood passed through the kidneys every minute
1.25 L
How many litres of blood passes through the nephrons of the kidney daily?
180 L
How much water did the kidneys reabsorb from the blood?
98 to 99%
How many litres of urine is actually excreted a day?
1 to 2.5 L
What is energy process for forming urine?
Both Mechanisms involve active transport
What are the two mechanisms of forming urine?
One requires the tubular reabsorption of water and solites back into the body and the other is the secretion of salts into the tubules to be lost in the urine
What percentage of water and solUtes Are reabsorbed into the proximal and distal tubules?
70 to 75% although it is mostly reabsorbed into the proximal tubes
What is the maximum renal threshold mechanism for glucose?
180 mg/ 100 ml
What is the renal threshold mechanism?
The limit as substance can be absorbed or filtered
What does it mean if glucose is secreted in
urine?
This as a sign of diabetes mellitus
Where is the highest grading of NaCl in the loop of Henley?
At the top of the hairpin
How is NaCl filtered out of the thick ascending limb?
Via facilitated diffusion as the wall is not permeable to water it is actively transported out of the thick segment in the outer medulla
Where does water leave by osmosis in the loop of Henley?
In the descending limb as the wall was not permeable to NaCl
What happens in the collecting duct?
More NaCl leaves, some uvea also leaves, water leaves by osmosis,
What animals have only juxtamedullary nephrons?
Desert mammals
Why do desert mammals have very long Loops of Henley?
This is due to their lots of NaCl pumps that produce minute quantities are very concentrated urine hyperosmotic to the blood
Describe the kidney function of freshwater fish
Freshwater fish are hyperosmotic to their surroundings so suffer a loss of salts and a large intake of water
What is unique about the nephron structure and freshwater fish?
Freshwater fish have no loops of Henley
Describe the kidney physiology in marine salt water fish
They are bony fish hypoosmotic to their surroundings so in danger of getting lots of salt and dehydrating
What is unique about the nephron structure in salt water marine fish?
The lack of glomeruli and Bowmans capsule
What is unique about the role of gills in Osmo regulation in fish?
Gills perform more osmoregulatory functions than the kidneys
What hormones released from the posterior pituitary gland in response to dehydration?
The anti-diuretic hormone a.k.a. ADH
What does a DH trigger in the kidney?
The release and insertion of Aquaporins a.k.a. proteins that allow water to be reabsorbed into the kidneys – the service water channels and lead to the formation of hyperosmotic urine
What is diabetes insipidus?
Lack of the ability to produce ADH or kidneys do not react to ADH
