excretion Flashcards
What is ultrafiltration?
The process by which small molecules are filtered out of the blood via diffusion in the kidney
What does the formation of tissue fluid involve?
Small molecules filtered out of the blood, occurring in the capillaries
List the components involved in both ultrafiltration and tissue fluid formation.
- Small molecules
- High hydrostatic pressure
- Ions
- Water
- Sugar
- Neutrophils
- Lymphocytes
- Basement membranes
How do ultrafiltration and tissue fluid formation differ in terms of location?
Ultrafiltration occurs in the kidney, while tissue fluid bathes cells in the intercellular space
What happens to molecules not reabsorbed in ultrafiltration?
They form urine in the kidney
What happens to molecules not reabsorbed from tissue fluid?
They enter the cells or form lymph
What is a key structural difference between ultrafiltration and tissue fluid formation?
Ultrafiltration has a knot of capillaries, while tissue fluid formation has a network of capillaries
What factors affect kidney function?
- Age
- Gender
- Exercise
- Pregnancy
- Body mass
- Ethnicity
- Genetic makeup
What does the presence of albumin in urine indicate?
Kidney damage, large proteins should stay in blood
Why is there less urea in the renal vein compared to the renal artery?
Urea gets filtered out of the blood in the glomerulus and some is reabsorbed in the tubule
What is the effect of kidney function on ion concentrations in the renal vein?
There are slightly fewer ions in the renal vein than in the renal artery due to filtration exceeding reabsorption + some are excreted
What happens to glucose levels between the renal artery and renal vein?
There is slightly less glucose in the renal vein due to reabsorption and usage by kidney cells for respirtation to provide ATP for active processes
How does the oxygen content differ between the renal artery and renal vein?
There is less oxyhaemoglobin in the renal vein as oxygen is used by kidney cells for aerobic respiration
What is the relationship between red blood cells and ultrafiltration?
The same number of red blood cells is found in both renal artery and renal vein as they are too large to be filtered out
Where is ADH produced?
In the hypothalamus/ within the cell bodies of the osmoreceptors
Where are ADH receptors located?
In the walls of the collecting duct and the distal convoluted tubule
How do diuretic drugs lower blood pressure?
By reducing water reabsorption in the collecting duct, reducing ion reabsorption, or blocking ADH action so that more water is excreted so blood vol would decr hence reducing pressure
Define excretion.
The removal of toxic metabolic waste from the body
What are examples of metabolic waste products?
- Urea
- Carbon dioxide
- Water
- Bile pigment
Define secretion.
The release of useful products from glands or ducts via vesicles
What are examples of useful products secreted by the body?
- Hormones
- Enzymes
- Antibodies
- Mucus
- Bile salts
- Neurotransmitters
What is a similarity between excretion and secretion?
Both require ATP and are involved in homeostasis
What happens to excess protein in the body?
It is converted into urea through deamination and the ornithine cycle
What is the role of the loop of Henle?
To establish a water potential gradient in the medulla
What tissue lines the proximal convoluted tubule?
Cuboidal epithelium
How does the proximal convoluted tubule reabsorb substances?
By selective reabsorption via co-transport and facilitated diffusion
What is the effect of caffeine on diuresis?
It prevents the introduction of additional aquaporins into the collecting duct
What are aquaporins?
Channels that allow water molecules to pass through cell membranes
What is the consequence of high protein intake on urea levels?
large amount of amino acids –> excess–>deaminated–>ornithine cycle .–> ureas lots. Increased blood concentration of urea so more urea in the filtrate + then urine + incr water resaportion from urine.
What happens in kidney failure regarding blood composition?
kidney failure –> cannot filter –> substances remain in blood –> Increased urea, ion and water content in blood over time
Where is most water reabsorbed in the nephron?
In the proximal convoluted tubule
What is the significance of a longer loop of Henle in certain animals?
found in animals that live in area where water is scarce –> more na+ and cl- pumped –> builds greater WP grad + allows reabsorption
How often is peritoneal dialysis fluid replaced compared to haemodialysis?
Four times a day for peritoneal dialysis, three times a week for haemodialysis
What hormone stimulates red blood cell production?
Erythropoietin (EPO)
one function of healthy kidney is to make this hormone
pateints w/ kidney failure may need to be given this
What is nephritis?
Inflammation and damage to the glomerulus and proximal convoluted tubule
What can happen if the liver does not break down insulin?
- Blood glucose concentration may fall too low as glucose would continue to be taken up by effector cells
- glucose continually converted into glycogen , which would sotre too much glucose as glycogen
- mitochondria would not be able to generate enough ATP as less glucose available , which would lead to coma + then death
What occurs during drug detoxification of paracetamol?
- 90% is combined with sulfate and glucuronide, and 5% is oxidized by the P450 system to produce NAPQI , which is then metaboilised
- once sulfate+ glucuronide reserves in the liver are used up , the P450 system takes over
- However, continued metabolism of paracetamol will result in high concentrations of NAPQI accumulating in the liver cells, resulting in death.
-This accumulation happens because glutathione has run out - NAPQI cannot cross the cell surface membrane, so cannot leave the cell
What happens when glutathione reserves are depleted during paracetamol metabolism?
High concentrations of NAPQI accumulate, which can lead to cell death
What is the effect of aldosterone on blood water potential?
It makes the water potential of blood more negative, increasing ADH secretion
What are the consequences of high alcohol intake on liver metabolism?
- Build-up of lactate (excess reduced NAD inhits conversion of lactate into pyruvate)
- Disruption of enzyme function(low pH)
- Lack of oxidized NAD for metabloic reactions + deamination would not occur
- build up of fatty acids , resulting in fat deposits in the liver cells –>Fatty liver/cirrhosis
True or False: The glomerulus is adapted for ultrafiltration.
True
What happens to the concentration of creatinine in the blood with reduced kidney function?
It increases due to lower filtration rate
What should be added to blood during dialysis?
Anticoagulant to prevent clotting
What happens to blood at the end of a dialysis session?
No anticoagulant is added to allow normal clotting
