P1 P2 ONLY EXCRETION 2i & 2j excretion + coordination and response Flashcards
why do humans need to excrete?
many of the necessary metabolic reactions that take place produce waste products
what is excretion?
it is the removal of the waste substances of metabolic reactions, toxic minerals and substances in excess of requirements
what are some of the metabolic waste produced in the human body?
- carbon dioxide and water from aerobic respiration in cells
- urea, produced by the breakdown of excess proteins in the liver
- other substances in excess such as medical drugs, and dietary minerals
what are the dangers of waste products?
if they are left in the body
- have toxic effects, like carbon dioxide which dissolves in water easily to from an acidic solution, lowers pH in cells, reduces activity of enzymes
- osmotic effect, concentrated body fluids can cause water to move out of cells, changing their water potential
- using up needed storage
what is the difference between excretion and egestion?
- egestion is the expulsion of food that has not been absorbed by the body, faeces etc
- excretion is the removal of metabolic waste products.
what are the organs of excretion?
- kidneys
- lungs
- skin
- liver
what does skin excrete?
water and mineral ions
what do the kidneys excrete?
urea, water and mineral ions
what do lungs excrete?
carbon dioxide and water
what does the liver excrete?
doesn’t excrete, is produces urea from the breakdown of amino acids
what are the main structures of the urinary system?
- kidney
- bladder
- ureter
- urethra
what do the kidneys do in the urinary system?
two bean shaped organs that filter the blood
what does the ureter do in the urinary system?
tube connecting the kidney to the bladder
what does the bladder do in the urinary system?
organ that stores urine (excess water, salts and urea) as it is produced by the kidney
what does the urethra do in the urinary system?
tube that connects the bladder to the exterior, where urine is released
what are the two main functions of the urinary system?
- to filter waste products from the blood and expel it from the body as urine
- to control the water levels of the body (osmoregulation)
what are the kidneys connected to?
- the renal artery which comes from the aorta and delivers oxygenated blood to the kidney
- and the renal vein which delivers the deoxygenated blood from the kidney to the vena cava
what are the three regions of the kidney and where are they?
- cortex, the outermost region
- medulla, the inner section of the kidney
- renal pelvis, the tube linking the kidney to the ureter
where are the nephrons in the kidney?
start at the cortex and loop down to the medulla and back up to the cortex
what is the nephron made up of?
- bowmans capsule
- proximal convoluted tubule
- loop of henlé
- collecting duct
- glomerulus
what happens in ultrafiltration?
blood is filtered
- first it travels through the glomerulus
- the narrow capillaries increases pressure of travelling blood so it causes smaller molecules to be forced out of the blood and into the bowmans capsule
- this is called the filtrate
what are the substances in the filtrate?
- glucose, water, urea and salt get pushed out of the blood
where does the reabsorption of glucose occur?
- first tube, or proximal convoluted
where does the reabsorption of water occur?
loop of henle and collecting duct
where does the reabsorption of salts occur?
loop of henle
where does the reabsorption of urea occur?
it isn’t reabsorbed
why can glucose only be reabsorbed at the first convoluted tubule?
only place that facilitates active transport of glucose
how does the glucose get reabsorbed?
active transport
how is the first tubule adapted for the reabsorption of glucose?
has many mitochondria to provide energy for the active transport of glucose molecules
how are water and salts reabsorbed?
as the filtrate drips through the loop of henle the necessary salts are reabsorbed back into the blood by diffusion
- as salts are reabsorbed water follows by osmosis
- water is also reabsorbed from the collection duct in different amounts dependent on how much the body needs
what happens to the remaining fluid in the collecting duct?
will form urine which is concentrated urea
what is homeostasis?
the maintenance of a constant internal environment
what is osmoregulation?
process of maintaining water and salt concentrations across membranes within the body
what is the importance of osmoregulation?
vital to prevent harmful changes occurring to cells as a result of osmosis
what happens if the body has too much water?
results in cells swelling as water moves into them, leads to cells bursting