Excretion Flashcards
define excretion
process by which toxic waste products of metabolism and substances in excess of requirement are removed from the body
examples of waste produces
carbon dioxide from lungs / urine made in kidneys
Nitrogenous waste (ammonia, urea and uric acid)
Bile pigments (produced during the breakdown of haemoglobin)
source of metabolic waste + effect on body if allowed to accumulate
carbon dioxide
source of metabolic waste + effect on body if allowed to accumulate
ammonia
source of metabolic waste + effect on body if allowed to accumulate
urea
source of metabolic waste + effect on body if allowed to accumulate
bile pigments
source of metabolic waste + effect on body if allowed to accumulate
uric acid
where is the liver
below diaphragm
how much blood is received by the liver
rich blood supply – 1dm3 of blood per minute
describe the blood flow through the liver
receives oxygenated blood from the heart via the hepatic artery -
receives deoxygenated blood from the digestive system via the hepatic portal vein
deoxygenated blood leaves the liver via hepatic vein
what is the purpose of the hepatic portal vein
allows the liver to absorb/metabolise nutrients from small intestine / digestion
what is connected to the liver
the gall bladder via the bile duct
what is stored in the gall bladder + its purpose
bile salts (that help to digest fats) a
bile pigments (a waste product from the breakdown of haemoglobin)
all make up bile
where does the bile go after being stored in the gall bladder
bile is then released into the duodenum via the bile duct
how many lobules does the liver have and how are they separated
4
separated from each other by connective tissue
what is a hepatocyte
The main liver cells which are highly metabolically active which divide and replicate
describe the appearance of a hepatocyte
uniform in appearance
large nuclei
prominent golgi apparatus
describe the internal structure of the liver
liver has lobes (right, left) + lobules with hepatocytes arranged radially.
Blood from hepatic artery and portal vein mixes in sinusoids.
Bile canaliculi collect bile, which flows through ducts to the common hepatic duct.
Connective tissue provides structural support.
Central veins drain blood at the lobule center - hepatic vein
gallbladder stores concentrated bile.
what are sinusoids
Spaces between hepatocytes where blood from the hepatic artery and portal vein mixes to increase the oxygen content
allowing to remain active.
what are kupffer cells
Like macrophages,
ingest foreign particles to protect the liver from disease.
Found in sinusoids.
what ar Canaliculi
Spaces in the liver where bile is secreted
from the canaliculi, the bile drains into ductules which transport it to the gall bladder
what is the hepatic artery
Artery which supplies oxygenated blood
what is the hepatic portal vein
Vein which supplies blood rich with digestive products for metabolism.
what is the hepatic vein
Vein which removes deoxygenated blood.
what is the gall bladder
A sac in which bile is stored before being released into the small intestine.
what is the falciform ligmanet
Ligament which separates the left and right lobes of the liver.
what is the portal triad
Between each hepatocyte is a triad of portal veins, arteries and bile ducts
drain into or out of the central vein of a hepatocyte to transfer substances via diffusion
how are sinusoids adapted for exchange
Walls more porous then capillaries
No basement membrane
Wider – slowing blood down
All so in close contact with surrounding hepatocytes
state the functions of the liver - 8
storage of glycogen
formation of urea
deamination
transamination
detoxification
synthesis of phospholipids
bile production
metabolism of RBC’s
what is transamination
Conversion of one amino acid into an other
what does bile consists of
water
electrolytes (bile salts / bicarbonate)
phospholipids
bile pigments – biliverdin + bilirubin
whats the purpose of bile
emulsify large fat globules into smaller droplets
has bicarbonate – neutralises stomach
how does the liver metabolise red blood cells
Broken into haem + globin
Haem– broken into biliverdin
Biliverdin reduced into bilirubin
Becomes water soluble in hepatocytes
Excreted into bile
what is glycogenesis
make glycogen from glucose
where does glycogenesis occur
in the liver and muscles
what is glycogenolysis
breakdown of glycogen into glucose molecules
where does glycogenesis occur
liver and muscles
what is gluconeogenesis
synthesis of glucose from non-carbohydrate precursors
such as amino acids and glycerol
where does gluconeogenesis occur
liver
2 stages of forming urea
deamination
ornithine cycle
how are amino acids deaminated
The amino group (-NH2) of an amino acid is removed, together with an extra hydrogen atom
These combine to form ammonia (NH3)
forms ammonium ions (NH₄⁺) in the cytoplasm
remaining keto acid
purpose of the keto acid after deamination
enter krebs cycle
converted to glucose / glycogen
why is the ornithine cycle important
Ammonia – very toxic / very soluble – dangerous when accumulates
Must be converted into urea
describe the ornithine cycle
what is the overall equation for the ornithine cycle
what happens to the urea formed
diffuses through the phospholipid bilayer of the membranes of the hepatocytes
then transported to the kidneys dissolved in the blood plasma
examples of things detoxified in the liver
Alcohol
Artificial chemicals – paracetamol
Lactic acid
Hormones e.g insulin
Hydrogen peroxide
where does detoxification of alcohol occur
occurs in surface of SER
explain how the detoxification of alcohol occurs
- ethanol is oxidised into ethanal by ethanol dehydrogenase
- hydrogen lost reduces NAD into NADH
- ethanal is oxidised into ethanoate by ethanal dehydrogenase
- hydrogen lost reduces NAD into NADH
label the liver cells
describe the flow of blood / urine in the kidney
oxygenated blood enters kidney via afferent arteriole from renal vein
passes through the nephron
leaves via efferent arteriole + renal vein
ureter carries urine from the collecting ducts to the bladder
urethra releases urine outside of body
describe the structure of the kidney
surrounded by capsule
has three main areas - cortex / medulla / renal pelvis
functional unit - nephron
label this diagram of the kidney
what are the parts of the 3 part filter
Endothelium of capillary
Basement membrane
epithelium of bowman’s capsule
how does the epithelium of the bowman’s capsule act as a filter
podocytes – specialised cells
pedicels - foot-like extensions from surface of cell + wrap around capillaries
Fit loosely together leaving filtration slits – 25nm wide
Filtered fluids pass through slits
describe selective reabsorption in the loop of henle
filtrate entering descending from PCT – isotonic with blood
top of the ascending limb = sodium ions are actively pumped into the medulla/ capillaries
bottom of ascending limb = ions leave via diffusion
lowers the water potential of the medulla
water moves out of the nephron by osmosis from the descending limb
As water moves out of the nephron = filtrate becomes more concentrated.
Fluid that reaches bend = very conc + hypertonic to blood
causes sodium ions to move out of the nephron at the bottom of the ascending limb down conc gradient by diffusion
lowers the water potential of the medulla even further, causing water to move out of the DCT. + collecting duct by osmosis.
Water that has moved into the medulla eventually moves into the capillary.
Sodium ions move back into the loop of Henle – conc gradient = increases conc of loop of Henle = cycle repeats
what is the overall effect of ADH
Causes luminal membranes to be more permeable
describe the process of haemodialysis
connected to machine via fistula
heparin + citrate added
blood flows through machine with partially permeable membrane
in machine – counter current
no net movement of glucose
ion content in dialysate same as blood -movement only occurs where there is an imbalance
net movement of urea out of blood
dialysate continuously refreshed to maintain conc gradient
describe the process of peritoneal dialysis
catheter surgically inserted into the patient’s abdomen
One end of the catheter remains outside the body
patient introduces the dialysis solution into the abdominal cavity through the catheter
peritoneum acts as a natural partially permeable membrane.
Waste products - urea /creatinine - diffuse from the blood vessels in the peritoneum into the dialysis solution
Osmosis occurs - excess fluid in the blood also moves into the dialysis solution as conc gradient of solutes.
advantages of kidney transplant
improves quality of life
no need to control diet so religiously
no more dialysis
disadvantages of kidney transplant
risk of rejection can be reduced NOT ELIMINATED by tissue typing – matching blood antigens
immunosuppressants – any surgery with general anaesthetic is high risk
limited donor organs
describe the process of how pregnancy tests work
Wick soaked in urine
mobile monoclonal antibodies that have small coloured beads
Only bind to hCG
Forms hCG-antibody complex with coloured beads
Urine reaches first window
Immobilised monoclonal antibodies arranged in line only bind to hCG-antibody complex
Coloured pattern if pregnant
Second window – line of immobilised monoclonal antibodies in pattern that only bind to mobile antibodies - don’t have to be bound to hCG
Coloured line forms regardless if test is positive
