Excretion Flashcards
What are the liver cells called?
Hepatocytes
How is the liver supplied with blood?
Via the hepatic artery and the hepatic portal vein
What is the function of the hepatic artery?
Oxygenated blood is supplied from the aorta via this artery. Supplies oxygen for aerobic respiration.
What is the function of hepatic portal vein?
Deoxygenated blood from the digestive system enters here from the intestine. This blood is rich in the products of digestion. The blood may also contain toxic compounds. The concentrations in the blood here will be uncontrolled
Where does blood leave the liver and go?
Blood leaves via the hepatic vein and rejoins the vena cava.
What is the fourth vessel connected to the liver?
The bile duct
What is the function of the bile duct?
Bile is secreted from the liver to be used in digestion and excretion. The bile duct carries the bile to the gall bladder.
Why does bile go to the gall bladder?
To be stored until required to aid digestion of fats in the small intestine.
What does bile contain?
Excretory products such as bile pigments like bilirubin which will leave the body with faeces
How is the liver divided?
Into lobes which are dither divided into lobules.
What are the 3 structures to label in a microscopic image of the liver lobules?
Inter lobular vessel
Intra-lobular vessel
Liver lobule
What are the inter-lobular vessels?
The smaller vessels that the hepatic artery and hepatic portal vein split into where they enter the liver. They run between and parallel to the lobules.
What is the sinusoid?
Lined with liver cells
The blood from both the hepatic portal vein and hepatic artery flows along here in close contact with liver cells.
What can the liver cells in contact with the sinusoid do?
They can remove substances from the blood and return other substances to the blood.
What are kupffer cells?
Specialised macrophages that can move about with the sinusoids?
What is the function of kupffer cells?
To breakdown and recycle old red blood cells.
What is the product of haemoglobin?
Bilirubin
What forms the bile duct?
The bile canaliculi
What has happened to the blood by the end of the sinusoid?
The concentrations of the blood components have been modified and regulated.
What is found at the centre of each lobule?
A branch of the hepatic vein known as the intra-lobular vessel.
Describe hepatocytes?
Cuboidal shape
Have many microvilli on the surface
Dense cytoplasm
Metabolic functions that occur in hepatocytes?
Protein synthesis
Transformation and storage of carbohydrates
Synthesis of cholesterol and bile salts
Detoxification
Liver functions?
Detoxification of alcohol and drugs
Breakdown of hormone
Destruction of red blood cells
What levels are controlled by the liver?
Glucose levels
Amino acid levels
Lipid levels
What does the liver synthesise?
Bile
Plasma proteins
Cholesterol
Red blood cells in the fetus
What does the liver store?
Vitamins A, D and B12
Iron
Glycogen
Enzymes contained by liver?
Catalase
Cytochrome P450
Where is alcohol broken down?
In the hepatocytes
Which enzyme action is involved in the detoxification of ethanol?
Ethanol dehydrogenase.
How is ethanol dehydrogenated further?
By the enzyme ethanal dehydrogenase
What is the final compound produced in the detoxification of ethanol?
Ethanoate acetate
This acetate is combined with coenzyme A to form acetyl coenzyme A
What atoms are released from the alcohol?
2H (hydrogen)
What happens to the hydrogen released from the alcohol detoxification?
It combines with a Coenzyme called NAD to then form reduced NAD
Why can’t amino acids be stored?
As the amine group makes them toxic
What is NAD also used for?
The breakdown of fatty acids
Why can drinking to much alcohol cause the liver to become enlarged?
As the liver will have insufficient stores of NAD to break down the fatty acids. The fatty acids will therefore be converted back to lipids and stored as fat in the hepatocytes
Why aren’t amino acids excreted as a whole molecule?
As they contain a lot of energy
What are the two processes to remove and excrete the amino component called?
Deamination followed by the ornithine cycle
What is the process of deamination?
Removes the amino group and produces ammonia.
Describe ammonia?
Very soluble and highly toxic
Must not be allowed to accumulate.
What does deamination produce?
Ammonia and a Keto acid
What can a Keto acid do?
Enter respiration directly to release its energy
What is the structure of an amino acid?
A carbon in the middle
Carboxyl group to the right
2NH2 to the left
Hydrogen below
What gets added to an amino acid in deamination?
Oxygen
What is the structure of a Keto acid?
2 Carbon in the middle
Double bond downwards to oxygen
Carboxyl group to the right
What is the formula for ammonia?
2NH3
What are the 3 parts of a kidney?
Outer- cortex
Inner- medulla
Centre- Pelvis which leads to the ureter
How does ammonia produce urea?
By combining with carbon dioxide
What do ammonia, carbon dioxide combined with the amino acid produce?
Citrulline
What is converted by the further addition?
Arginine
What is arginine re-converted to and how?
To orthinine by the removal of urea
Word equation for deamination?
Amino acid plus oxygen
Equals Keto acid plus ammonia
External kidney structures?
Cortex
Medulla
Pelvis
Where does the pelvis lead to?
Ureter
What is at the start of the nephron?
The Bowmans Capsule
How does blood enter the kidney?
Via the renal artery
Splits to form many afferent arterioles
Describe the glomerulus?
A knot of capillaries
Blood enters the glomerulus via the afferent arterioles and leaves via the efferent arteriole
Surrounded by the Bowmans capsule
Where does ultrafiltration occur?
Barrier between capillary and lumen of Bowmans capsule
What are the 3 layers of ultrafiltration?
Endothelium of capillary
Basement membrane
The epithelial cells of Bowman’s capsule
What is the basement membrane made up of?
Colleges fibres and glycoproteins
How does the blood pass through the endothelium of the capillary?
The gaps between the endothelium cells
The pores within the endothelium cells
Role of basement membrane?
Prevents the passage of molecules of a larger relative molecular mass
What can’t pass through the basement membrane?
Most proteins
All blood cells
What are the cells called than line the Bowmans capsule?
Podocytes
Describe podocytes?
Contain many finger like projections- major processes
On each major process are foot processes
Role of foot processes?
Ensure that there are gaps between the endothelium cells of the capillary
What are the 3 parts of the tubule?
Proximal convoluted tubule
Loop of henle
Distal convoluted tubule
Describe the mechanism of reabsorption?
Sodium ions are pumped out of the cell
Sodium ions diffuse back in cotransporting amino acids or glucose
This decreases water potential so water moves in by osmosis
