Excretion - Module 5 Flashcards
what is excretion
The removal of metabolic waste from the body.
e.g: carbon dioxide and urea
how is urea formed
Formed from the breakdown of amino acids
what is deamination
The amino group (-NH2) of an amino acid is removed, together with an extra hydrogen atom. These combine to form ammonia (NH3)
+organic acid
formula for dissociation of carbonic acid
H2CO3 -> H+ + HCO 3-
where is urea produced
the liver
ornithine cycle (simple)
Ammonia + Co2 -> urea + water
why is urea removed from body
Nitrogen in amino acids can’t be stored
nitrogen forms ammonia
ammonia is highly toxic
urea is less toxic
what are the 3 main kidney functions
-osmoregulation- maintaining water balance of the blood
-Excretion - removing waste products such as urea from the blood
-Maintaining correct balance of ions in t he blood
where does Ultra filtration take place
-between glomerulus and bowmans capsule
*first stage of making urine
remove small molecule from blood which enter nephron
what happens in the renal cortex
where blood is filtered
has dense capillary networks that carry blood/ connect renal artery to nephrons
what happens in renal pelvis
collects urine
renal medulla
contains tubules of nephrons which remove salt, urea, water from the blood
renal artery
takes “dirty” blood cotaining urea to kidney
renal vein
“clean” blood away from kidney
Ureter
take urine from kidney to bladder
What s the order of the nephron. From blood to ureter
1) Afferent arteriole
2) Glomerulus
3)Efferent arteriole
4) Bowman’s capsule
5) PCT (Proximal convoluted tube)
7)Loop of Henle
8) DCT ( Distal convoluted tubule)
9) Collecting duct
10) pelvis/ureter?
Afferent arteriole
arteriole that takes blood into the glomerulus
efferent arteriole
arteriole that takes the filtered blood away from the glomerulus
Glomerulus
tangle of capillaries surrounded by the Bowman’s capsule
DCT
Distal convoliuted tubule.
A second twisted tubule located in the cortex
PCT
Proximal convoluted tubule
the first, coiled region of the tubule after the bowmans capsule, found in the cortex
Collecting duct
urine passes down the collecting duct through the medulla to the pelvis
Loop of Henle
A long loop of tubule that runs down from the cortex through the medulla to a bend at the bottom of the loop. The ascending limb travels back up through the medulla to the cortex
describe and explain how the first barrier of ultrafiltration works
-Blood in the glomerulus is under high pressure because the afferent arteriole is wider than the efferent arteriole
-This forces liquid and small molecules in the blood out through the capillary wall.
- The fluid passes through the capillary Endothelium which has narrow gaps and acts like a sieve
describe and explain how the 2nd barrier of ultrafiltration works
-It then passes through the basement membrane which is made up of collagen fibres and other proteins and acts as a second sieve
-Proteins and blood cells cannot pass through the basement membrane so remain in the blood
describe and explain how the 3rd barrier of ultrafiltration works
-The fluid finally passes through the podocyte cells in the epithelium of the Bowman’s capsule
-The podocyte cells act as an additional filter to ensure that any large plasma proteins, platelets etc do not enter the tubule
-The filtrate that enters the bowmans capsule contains amino acids, water, glucose and urea
(small molecules pass the slit in epithelium between podocytes)
The filtrate that enters the bowmans capsule contains…
amino acids, water, glucose and urea
Endothelium
inside wall of blood vessels
epidermis
outside wall
what is the main function of the nephron
To return the useful filtered substances to the blood
Facilitated diffusion
Diffusion of particles through carrier proteins or channel proteins in the plasma membrane. Does not require ATP
specific
Process of selective reabsorption in the PCT
1) Na+ ion pumped out of cell walls of PCT.
Na+ ions move into blood plasma
2) Na+ ions from filtrate now diffuse by facilitated diffusion into cell wall of PCT
Proteins are Co-transported. Glucose + amino acids diffuse with Na+
3) Water potential of filtrate increases so water moves by osmosis into cells of the wall of the PCT
-some urea also diffuses back through the walls
4) All glucose, amino acids, and some urea are absorbed back into the blood
Hepatic artery
Supplies liver with oxygenated blood
Hepatic portal vein
Blood from small intestine
5 roles or the liver
-controlling glucose levels
-secrete bile
-synthesise plasma proteins such as fibrinogen. Globulin, albumin…
-Transamination
-detoxification of substances such as hydrogen peroxin
What happens in sinusoids
Blood from hepatic artery and portal vein mix in sinosoid
Bile duct
Takes bile to gall bladder to be stored
Why Hepatocytes arranged in thin blocks
Have good blood supply to get enough O2 and break down any harmful materials in the blood quickly
Hepatocytes close contact to ___ which aids ____
Bile canaliculi
Diffusion
Kupffer cells attach to walls of ____ to ____
Sinusoids
Remove bacteria and break down old RBCs
Hepatic vein
Takes deoxygenated blood away from live
Selective reabsorption in the PCT
1)Na+ ions pumped out of PCT.
Na+ ions move into blood plasma
2) Na+ ions from filtrate now diffuse by facilitated diffusion into cell.
Proteins are co-transport so glucose + amino diffuse with Na+
3) water potential of filtrate increases so water moves by osmosis into cells of the wall of the PCT . (from filtrate)
some urea also diffuses back through the walls
4)All glucose, amino acids and some urea are reabsorbed into the blood
Selective reabsorption in the PCT Process
1)Na+ ions pumped out of PCT.
Na+ ions move into blood plasma
2) Na+ ions from filtrate now diffuse by facilitated diffusion into cell.
Proteins are co-transport so glucose + amino diffuse with Na+
3) water potential of filtrate increases so water moves by osmosis into cells of the wall of the PCT . (from filtrate)
some urea also diffuses back through the walls
4)All glucose, amino acids and some urea are reabsorbed into the blood
selective reabsorption of water
where does it take place
describe concentration of tissue fluid coming into loop of henle
-take place in loop of Henle = section of tubule enabling mammals to produce urine more concentrated than own blood
-Filtrate reaching the top of the loop of Henle from the PCT is isotonic with tissue fluid surrounding tubule
what is the mechanism behind the loop of henle called
the Countercurrent multiplier mechanism
how does the the Countercurrent multiplier mechanism work?
1)Near top of ascending limb, Na+ and Cl- ions are actively transported into the medulla.
The ascending limb is impermeable to water, so water stays inside tubule. This creates a low WP inside medulla due to high conc. of ions
2) Because there’s a low water potential in the medulla than in the descending limb, water moves out of the descending limb into the medulla by osmosis. This makes the filtrate more concentrated (the ions can’t diffuse out- descending limb isn’t permeable to them). The water in the medulla is reabsorbed into the blood through the capillary network.
3) Near the bottom of the ascending limb, Na+ and Cl- ions diffuse out into the medulla, further lowering the water potential in the medulla
4) The first three stages massively increase the ion concentration in the medulla, which lowers the water potential. This causes water to move out of the collecting duct by osmosis. As before, the water in the medulla is reabsorbed into the blood via the capillary network.
(The volume of water reabsorbed from the collecting duct into the capillaries is controlled by changing the permeability of the collecting duct ADH)
what is osmoregulation
The control of the water potential of the blood
what happens to water potential of urine when you exercise
WP lowers
ADH =
Anti Diuretic Hormone
Process of ADH release
WP of blood is monitored by cells called osmoreceptors in the hypothalamus. When osmoreceptors are stimulated by a low water potential in the blood, the hypothalamus sends nerve impulses to the posterior pituitary gland to release a hormone called ADH into the blood
Process of ADH effects
ADH molecules bind to receptors on the plasma membranes of cells of the DCT and collecting duct. Protein channels called aquaporins are inserted into the plasma membrane. These channels allow water to pass through via osmosis, making the walls of the DCT and Collecting Duct more permeable to water.
More water is reabsorbed from these tubules into the medulla and into the blood by osmosis.
A small amount of concentrated urine is produced, which means less water is lost from the body.
what happens when a increase in water potential is detected by osmoreceptors in the hypothalamus?
Hypothalamus sends nerve impulses to the pituitary gland. Pituitary gland releases less ADH, walls of collecting duct become less permeable to water. Less water reabsorbed, larger volume of urine produced
What can you expect to find in the urine of a diabetic ?
glucose
What can you expect to find in the urine of someone with high blood pressure
abnormal protein
is glucose found in a healthy persons urine/
no
Summarise how pregnancy tests work
-Urine applied to stick
-If pregnant, hCG will be present in urine
hCG will bind to mobile monoclonal antibodies attached to coloured bead ( antibodies are complementary to hCG)
-Form hCG/antibody complex
-hCG/antibody complex is carried up test
hCG/antibody complex binds to line of immobilised antibodies- forms coloured line AT RESULT WINDOW
-Excess mobile antibodies bind to second line of immobilised antibodies- forms second coloured line to show test is working AT CONTROL WINDOW
How is urine tested for testosterone
gas chromotography
-Urine sampel is vaporised and passed through a column containing a polymer.
-the different substances move at different speeds which seperates the substances in urine.
-A mass spectrometer then converts them into ions and separates them
- results analysed by a computer
GFR?
used to ..?
Glomerular filtration rate,
used to measure and to indicate kidney disease
Haemodialysis description
In haemodialysis the patient’s blood is passed through a dialysis machine —
the blood flows on one side of a partially permeable membrane and dialysis
fluid flows on the other side. The blood and dialysis fluid flow
in opposite directions in order to maintain a steep concentration gradient
between the two fluids, to increase the rate of diffusion.
During haemodialysis, waste products and excess water and ions
diffuse across the membrane into the dialysis fluid, removing them from the
blood. Blood cells and larger molecules like proteins are prevented from
leaving the blood.
peritoneal Dialysis description
Before a patient can have peritoneal dialysis for the first time, an operation
is needed to insert a tube that goes from outside the patient’s body into their
abdominal cavity (the space in the body where the intestines, stomach,
kidneys, etc. are found). The abdominal cavity is lined with a membrane
called the peritoneum. During peritoneal dialysis, dialysis fluid is put through
the tube into the abdominal cavity . The fluid remains in the
body while waste products from the patient’s blood diffuse out of capillaries
and across the peritoneum into the dialysis fluid. After several hours, there’s
an exchange — the fluid inside the body is drained out, and a fresh lot of
dialysis fluid is put in. This fluid is left there until the next exchange.
Transplant description
A kidney transplant is where a new kidney is implanted into a patient’s body
to replace a damaged kidney. The new kidney has to be from a person with
the same blood and tissue type. They’re often donated from a living relative,
as people can survive with only one kidney. They can also come from other
people who’ve recently died — organ donors.
Advantages of Haemodialysis
-Have dialysis free days
-keep alive until transplant
-Less risky than transplanmt
-no surgery
Advantages of peritoneal Dialysis
-Can be done by patient at home
-Keep alive until transplant #
-Less risky than transplant
Advantages of kidney transplant
-Cheaper than long term dialysis
-More convenient, don’t feel unwell between sessions
Disadvantages of haemodialysis
-patients feel increasingly unwell between haemodialysis sessions = build up of waste
-Sessions = 3-5 hours , 2-3 sessionns a week, in hospital
-Expensive
-Inconvenient
-Must control diet = protein and starch
Disavdantages of Peritoneal dialysis
-Risk of infection at the tube
-No dialysis free days
-4 exchanges daily or overnight
Disadvantages of Peritoneal dialysis
-Risk of infection at the tube
-No dialysis free days
-4 exchanges daily or overnight
Disadvantages of Transplants
-Risky, Major operation
-Immune system may reject transplant
-Must take immunosuppressants
Explain how the structure of a liver lobule aid the functions of the liver. (4)
Blood from hepatic artery and hepatic portal vein mix
In sinusoid
Hepatocytes arranged in thin blocks
Every hepatocyte has a good blood supply to get enough oxygen and break down any harmful materials in the blood quickly
Hepatocytes close contact to bile canaliculi
Aids diffusion
Detoxification of alcohol
in liver
Ethanol is converted to ethanal by ethanol dehydrogenase
Ethanal is converted to ethanoic acid ( also known as acetic acid) by ethanal dehydrogenase
Ethanoic acid dissociates to produce ethanoate and hydrogen ions
Ethanoate combines with coenzyme A to form acetyl coenzyme A
Acetyl coenzyme A involved in respiration as a source of energy
Liver cirrhosis
The liver tissue is irreversibly damaged.
Hepatocytes dies and are replaced with fibrous tissue.
This means the hepatocytes can no longer divide and replace themselves so the liver shrinks.
Monoclonal antibodies
antibodies from a clone of cells that are produced to be specific to a specific antigen/ chemical
Cells in the proximal convoluted tubule have adaptations for reabsorption:
They are covered with microvilli increase S.A
They have many mitocohondria provide ATP for active transport
