Excretion - 5 Flashcards
What is excretion
Excretion is the removal of metabolic waste products
What are the functions of the liver
Breaks down the amino acids into urea
Detoxifies the blood
Stores glycogen
Makes bile
Describe the ornithine cycle
Amino acids are deaminated
The organic acids are respired or stored as glycogen
Ammonia is toxic so it is converted into a less harmful substance
Ammonia reacts with CO2 which converts it to urea
Urea is released into the bloodstream
It is filtered by the kidneys and excreted from the body
Describe the structure of the liver
Hepatic artery - delivers oxygenated blood to the liver
Hepatic vein - takes deoxygenated blood away from the liver
Hepatic portal vein - connects the liver to the intestines
Bile duct - takes bile from the liver to the gall bladder
What is the function of the kidneys
Remove excess water, ions and urea from our blood as urine
What is the gross structure of the kidneys
Medulla - Inner part
Cortex - outer part
Renal vein - filtered blood is taken away from the kidneys
Renal artery - carries blood to the kidney
Describe the structure of a nephron
Bowmans capsule
Glomerulus
descending limb
Ascending limb
Collecting duct
Proximal convoluted tubule
Describe the process of ultrafiltration
Blood enters the glomerulus through the afferent arteriole.
Blood leaves the glomerulus via the smaller efferent arteriole, maintaining a high hydrostatic pressure.
This high pressure forces molecules, like water and small solutes, out of the blood through pores in the capillary endothelium.
The molecules move through the Bowman’s capsule epithelium, which has specialised cells called podocytes with extensions known as pedicels that wrap around capillaries and help to filter the blood.
Filtered fluid collects in Bowman’s capsule.
How are the cells on the Bowmans capsule adapted for ultrafiltration
pores between epithelial cells of capillaries
Fluid can pass between membrane of podocytes
State what happens during selective reabsorption
Occurs in proximal convoluted tubule
Na+ actively transported out of cells into tissue fluid
Glucose/amino acids enter cells with sodium ions by facilitated diffusion
Glucose/amino acids diffuse into blood capillary
Describe the loop of Henle
Involved in reabsorption of water into the blood
Makes kidneys tissue fluid very concentrated
Has a counter current system
allows water to be absorbed by collecting duct
How is water absorbed
The ascending limb is impermeable to water but permeable to ions
Ions are actively transported into the medulla
This lowers the water potential of the medulla
Water moves out the nephron at the descending limb due to osmosis
As water moves out of the nephron, the filtrate becomes more concentrated
Causing ions to move out by facilitated diffusion
This lowers water potential of the medulla, so water moves out the DCT by osmosis
Water in medulla moves into the capillaries
What is the roles of ADH
Attaches to receptors in cell membrane of collecting duct
Series of enzyme reactions happen
vesicles containing water-permeable channels fuse to membranes
More water reabsorbed
Explain how the body reacts to a drop in water potential
Osmoreceptors in the hypothalamus detect a change in water potential
Hypothalamus signals to the posterior pituitary gland to secrete ADH
ADH causes walls of DCT and collecting duct to become more permeable
More water moves by osmosis out of the DCT/collecting duct and reabsorbed into bloodstream
Increasing water potential
A smaller volume of urine is produced
What can cause kidney failure
Kidney infections
Kidney stones
Uncontrolled diabetes
High blood pressure
