5.1.2 Excretion (Finish) Flashcards
What is excretion?
Excretion is the removal of metabolic waste from a cell or from the body.
what are three examples of metabolic waste products
Carbon dioxide
Urea
Bile pigments
what are the individual liver cells knowns as?
hepatocytes
what is it called when Hepatocytes are grouped into dense structures?
lobules
what in in the core of each lobule
central vein
how do liver cells regenaerate when damaged?
Mitosis
what are the three vessels in the liver?
hepatic artery
hepatic portal vein
hepatic vein
what is the hepatic artery?
branch from the aorta
brings oxygenated blood (for areobic respiration)
what is the hepatic portal vein?
Comes from the small intenstine
blood rich in the products of digestion (glucose, amino acids etc)
what is the hepatic vein?
branches into the inferior vena cava
takes deoxygenated blood
ratio of blood between hepatic artery : hepatic portal vein
25% hepatic artery : 75% hepatic portal vein
where do the two blood supplies from the liver meet?
at the sinusoids
what are the function of the sinusoids?
carry blood through the liver tissue in close contact with hepatocytes.
what are the walls of the sinusoids made up of?
The walls of sinusoids are made up of the hepatocytes themselves, plus some Kupffer cells
what are kupffer cells?
essentially macrophages
held in a fixed position as part of the sinusoid wall
capable of phagocytosis, removing pathogens from the blood
why are sinusoid NOT considered capillaries?
they do not have walls made of endothelium tissue.]
where does blood from the sinusoids drain into?
The central vein
what do all of central veins of all lobules eventually merge with?
the hepatic vein
what vessel does blood leave the liver?
the hepatic vein, joining the inferior vena cava
how do the hepatocytes produce and secrete bile? 6 steps.
hepatocytes secrete bile
bile canaliculi (tube)
bile ductiles (wider vessels)
ball gladder (storage)
bile duct
small intestine
what is bile, and what is its roles?
what:
alkaline fluid
function:
emulsify lipids into smaller droplets
neutralise stomach acid
what are the three basic functions of the liver?
storage of glycogen
detoxification
formation of urea via the ornithine cycle
what are the functions of the liver related to?
homeostasis
How does glycogen strorage work?
Hepatocytes are a store of glycogen
Glycogen is insoluble
branched structure ∴ easily hydrolysed (glycogenolysis)
how are hepatocytes affected by insuin?
RESPONSE TO HIGH BLOOD SUGAR
insulin released by β‐cells in the pancreas
hepatocytes to increase their uptake of glucose
increased conversion of glucose to glycogen (glycogenesis)
increased respiration rate
these actions bring the blood sugar level down
how are hepatocytes affected by glucagon?
RESPONSE TO LOW BLOOD SUGAR
Glucagon released by α‐cells in the pancreas
hepatocytes to decrease their uptake of glucose
increase hydrolysis of their stored glycogen to glucose (glycogenolysis)
hepatocytes to release this glucose into the blood
these actions bring the blood sugar level up
Extra: gluconeogenesis - produce more glucose from non‐carbohydrates (amino acids or fatty acids)
What does adrenaline with the storage of glycogen?
mimics the effect of glucagon
what is detoxification?
The removal of toxins from the blood and their breakdown or conversion into less harmful products
suggest two examples of detoxification
Breakdown of hydrogen peroxide into water and oxygen
Conversion of ingested alcohol (ethanol) into less harmful ethanal
Describe the breakdown of hydrogen peroxide into water and oxygen
hydrogen peroxide —–> water and oxygen
catalase enzyme
inside the membrane-bound organelles (similar to lysosomes) called peroxisomes
Describe the conversion of ingested alcohol (ethanol) into less harmful ethanal. Learn image.
oxidation of ethanol
inside the cytoplasm of hepatocytes
ethanol + [O} —-> Ethanal
Ethanal + [O] ——> Ethanoic acid
How is urea formed?
via the orthanie cycle
how are process from one protein to another?
proteins are digested by protease enzymes in the stomach and small intestine
absorbed into the blood
Body cells absorb amino acids from the blood for use in translation
what happens to excess amino acids?
INSIDE LIVER:
Transamination
Deamniation
what is transamination? Why is it useful?
what:
one type of amino acid (excess) converted into a different type of amino acid
why useful:
realtive proportions of 20 amino acids from diet do not match the proportions needed for protein synthesis
what is deamination?
the amine (NH2) group of the amino acid is removed
amine group - converted to to ammonia (orthanie cycle)
carbon skeleton - converted to pyruvate or fatty acid
Draw out the ornathine cycle
describe the 3 steps of the orthanince cycle
- Ammonia and carbon dioxide combine with an acceptor molecule, ornithine, producing an intermediate called citrulline;
- Citrulline combines with a further ammonia molecule, producing arginine;
- Arginine is split into urea (which leaves the cycle) plus ornithine: since the acceptor molecule ornithine is regenerated, the cycle can continue and more ammonia can be converted to urea.
is the ornathine cycle passive or active?
Active, it requires ATP
What is the main function of the kidneys?
filtering the blood
producing urine (urea and water)
osmoregulation
label this kidney
How does one remember the order of the kidney strucutre?
Its in alphabetical order.
capsule
cortex
medulla
ureter
label this nephron
what is a nephron
the tubules which make up the main functional strucutres of the kidneys.
what is the bowman’s capsule? what is its function?
cup‐like structure
in the cortex
start of a nephron
contains the glomerulus
the site of ultrafiltration of the blood, since water and small solutes are pushed out of the blood into the Bowman’s capsule
what is the glomerulus?
tangle of capillaries in the bowman’s capsule
what is the proximal convoluted tubule (PCT)?
cortex
selective reabsorption of glucose, salt ions etc back into the blood of
an adjoining capillary
Most of the water is reabsorbed here.
what is the Loop of Henle?
elongated hairpin‐shaped section of the nephron
descending limb and ascending limb
creates a very high solute concentration in the tissue fluid of the medulla, to increase reabsorption of water
allows for more concentrated urine
what is the Distal convoluted tubule (DCT)?
cortex
permeability of its walls to water depends on ADH (anti‐diuretic hormone) concentration
role:
finetuning the extent of water reabsorption
selective reabsorption of ions including H (conctrolling blood pH)
What is the collecting duct?
takes fluid from the DCTs of multiple nephrons
cortex->medulla->pelvis
sensitive to ADH, hence in determining the final concentration of urine produced
what is the hydrostatic pressure like in the blood vessels?
very high hydrostatic pressure
what is the order of ultrafilration?
afferent arteriole brings blood to glomerulus (from renal artery)
very high hydrostatic pressure
water plus small solutes forced through the permeable walls of the glomerular capillaries into the bowman’s capsule
——————————————————————————————————–Blood leaves the glomerulus via efferent arteriole (narrower lumen thyan afferent arteriole to maintain high hydrostatic pressure)
efferent arteriole branches into a network of capillaries (around the PCT, loop of Henle and DCT)
^Allows for the reabsorbtion of water and small solutes^
capillaries merge into venules which converge into the renal vein to heart
what is the blood leaving the kidneys like?
very low urea concentration
concentrations of glucose and amino acids that are (almost) as high as in the blood that entered the kidney
salt ion concentration and water potential that should have been corrected to optimal levels
what are the main three functions of the kidney?
ultrafiltration;
selective reabsorption;
production of urine
