Excretion Flashcards
What is excretion?
The removal of metabolic waste
What is egestion?
The elimination of faeces
Which substances need to be excreted?
CO2
Nitrogen containing compounds (urea)
Other compounds such as bile pigments
What are the main excretory organs?
Lungs - removal of CO2 & water vapour
Kidneys - removal of urea
Liver - production of bilirubin and urea
Skin - removal of salts, urea, water etc. via sweat
How does oxygenated blood travel to the liver?
Oxygenated blood from the heart travels to the liver via the aorta and hepatic artery
What does “hepatic” refer to?
The liver
How is blood removed from the liver?
Blood leaves the liver and returns to the heart via the hepatic vein which re-joins the vena cava
What is the role of the hepatic portal vein?
It carries the products of digestion to the liver, directly from the intestines
Where is bile produced and secreted?
It is produced and secreted in the liver
What does “renal” refer to?
The kidneys
Where is bile stored?
Bile is stored in the gall bladder
Where is bile released?
Bile is released by the bile duct into the small intestine where it then emulsifies fats
What are hepatocytes?
Liver cells
Features of hepatocytes
Large nuclei
Prominent Golgi apparatus
Lots of mitochondria
What are sinusoids?
The space surrounded by hepatocytes
Functions of the liver
Control blood glucose levels
Synthesis of bile, cholesterol
Breakdown of hormones
Destruction of red blood cells
What is the role of catalase?
Catalase converts hydrogen peroxide to oxygen and water
What is the role of Cytochrome p450?
Cytochrome p450 is a group of enzymes used to breakdown drugs
What is the role of alcohol dehydrogenase?
Alcohol dehydrogenase breaks down ethanol into ethanal.
Ethanal is then converted to ethanoate
Examples of substances broken down by the liver
Alcohol
Paracetamol
Insulin
What is transamination?
The conversion of one amino acid to another. This is important as the diet may not always contain the required amino acids
What are some adaptations of hepatocytes?
Thin/flat cells allow for short diffusion distance
Fenestrated (tiny openings/pores) increases permeability
What is deamination?
Excess amino acids are harmful and can’t be stored as they are nitrogenous.
The hepatocytes remove the amino groups. This forms ammonia which is then converted to urea. Urea is then removed from the blood by the kidneys and excreted via urine
What are the functions of the kidneys?
Osmoregulation
Excretion
Filter urea and waste products out of the blood and excrete them
What is the role of the renal artery and where is it found?
The renal artery carries unfiltered blood into the kidney.
The renal artery branches off the abdominal aorta and are at arterial pressure
What is the role of the renal vein?
The renal vein drains blood once it has circulated through the kidneys and inferior vena cava
Describe the process of the ornithine cycle?
Ammonia and carbon dioxide combine with ornithine to produce citrulline and water. Citrulline is converted to arginine (removal of water). Arginine is then re-converted to ornithine by the addition of water and removal of urea.
Where is the site of ultrafiltration in the nephron?
The glomerulus
What is filtered out of the blood and into the bowman’s capsule?
Water
Amino acids
Glucose
Urea
Inorganic ions (Na+, Cl-)
What is not filtered out of the blood into the nephron and stays in the capillary instead?
Blood cells
Large proteins
Why does the afferent arteriole have a wider lumen than the efferent arteriole?
The afferent arteriole is wider which maintains a higher hydrostatic pressure. More blood enters the glomerulus and less blood leaves.
How does water enter/increase in the body?
Good
Drink
Metabolism (respiration)
How does water leave the body?
Urine
Sweat
Faeces
Water vapour in exhaled air
What happens when water potential falls in the blood?
The pituitary gland is stimulated to produce ADH. Thirst is increased
Which organ detects changes in water potential in the blood?
The brain (hypothalamus)
What organ breaks down ADH when it is no longer needed?
The liver
What kind of control (feedback) is osmoregulation?
Negative feedback control involving osmoreceptors in the hypothalamus
What are possible causes of kidney failure?
Blood loss following an accident
High blood pressure
Diabetes
Overuse of certain drugs
What two substances may be detected in the urine following kidney damage/failure?
Blood
Large proteins
What are some effects of kidney damage/ failure?
Loss of electrolyte balance
Build-up of urea
Weakened bones
High blood pressure
What is the glomerular filtration rate (GFR)?
It is a measure to indicate kidney disease
What is the normal GFR?
90-120 cm3 /min
What is the GFR for chronic kidney disease?
Below 60cm3 / min
What is the GFR for kidney failure?
Below 15cm3 / min
What treatment option are available if both kidneys are damaged?
Renal dialysis
Kidney transplant
What is the name of that hormone that is detected in a pregnant persons urine?
hCG
How are monoclonal antibodies produced?
A mouse is injected with hCG so it makes that appropriate antibody in response.
The B cell that make the antibody are then removed from the mouse and fused with a myeloma (a type of cancer cell). This is now called a hybridoma.
Each hybridoma reproduces rapidly resulting in a clone of million of cells making the desired antibody.
The antibodies are collected, purified and used in a variety of ways
How are sodium ions reabsorbed into the blood from the nephron?
1) Na+ ions are actively pumped out of the cells lining the tubule. K+ ions are moved into the tubule so the charge is equal
2) Na+ conc. in the cells cytoplasm decreases, creating a conc gradient
3) Na+ diffuse into the cell through a co-transport protein - carrying glucose or an amino acid at the same time
4) water moves into the cell by osmosis as a result
5) Glucose/Amino acids diffuse into the blood. Water follows
What is gas chromatography?
Urine same is vaporised and passed through a column containing a polymer. The substances in the urine travel through the column at different speeds so separate out.
