metabolism
=> sum of both anabolic and catabolic reactions with the body of an organism anabolism: - build up complex molecules catabolism: - break down complex molecules
excretion
process by which metabolic waste products and toxic substances are removed from the body
urinary system
kidneys ureters bladder urethra hilus sphincter muscle
kidney
cortex medulla medulla pyramids kidney tubules renal pelvis
kidney nephron (kidney tubules)
Bowman's capsule proximal convoluted tubule loop of Henle distal convoluted tubule collecting duct
ultrafiltration
- when blood enters the glomerulus, some of the blood plasma (without plasma protein) is filtered or forced out of the blood capillaries into the Bowman’s capsule
- during ultrafiltration in the kidneys, large molecules such as plasma proteins, antibodies and red blood cells remain in the arteriole
=> high hydrostatic pressure
• an afferent arteriole with a wide diameter than the efferent arteriole creates the high blood pressure required for ultrafiltration to occur in the glomerulus
=> a partially permeable membrane
• the basement membrane, which separates the glomerulus from the Bowman’s capsule, allows only water and very small molecules to pass through
filtrate - water, small molecules such as glucose, amino acids, mineral salts and urea
residue - large molecules such as plasma proteins and red blood cells
selective reabsorption
- selective reabsorption occurs mainly in the proximal convoluted tubule
- water and useful substances and reabsorbed from the tubules into the surrounding capillaries
- > excess water and salts, and nitrogenous waste products pass from tubules into the collecting ducts and then into the renal pelvis as urine
osmoregulation
- the water potential of blood plasma needs to be kept relatively constant
- the regulation of the water potential of blood plasma is called osmoregulation
- the water potential of of blood plasma depends on the amount of water and solutes in the plasma
- the water potential of blood plasma is controlled by anti-diuretic hormone (ADH)
- ADH is produced by the hypothalamus and pituitary gland secrete ADH
- ADH increases reabsorption of water by the kidney tubules
- Since kidneys help to regulate the concentration of water and salts in blood, they are called osmoregulators. osmoregulation maintains the concentration of water and salts within an organism. it is a type of homeostasis
- as blood volume is controlled by removing excess salts and water, blood pressure is also indirectly regulated by osmoregulation. hence, the kidney plays a vital role in bod volume and blood pressure regulation
- high blood pressure can cause blood vessels in the brain to burst, ad this would result in a stroke
kidney failure & dialysis
- > kidney are excretory organs and osmoregulators
- > each person have 2 kidneys. therefore, when one kidney fails to function, the person can still lead a normal life
- > a dialysis machine mimics the function of the kidney
- > kidney failure may be caused by
- hypertension
- diabetes
- excessive intake of alcohol
- complications from surgery
- severe injuries or bacterial infection
- drug overdose
blood is drawn from a vein in the patient’s arm
blood is umped into the dialysis machine through a tubing
the tubing is partially permeable
small molecules like urea and metabolic waste products diffuse out of the tubing
larger molecules like platelets and blood cells remain in the tubing
the filtered blood is returned to a vein in the patient’s arm
features of dialysis machine
long, narrow, partially permeable and coiled dialysis tubing
- to increase surface area to volume ratio to speed up the rate of exchange of substances between the patient’s blood and the dialysis fluid
- small molecules, such as urea and mineral salts, can diffuse through the tubing, but blood cells and protein will be retained in the blood
features of dialysis machine
sterile dialysis fluid that contains the same concentrations of useful substances (glucose, amino acids and mineral salts) as blood
- to prevent the diffusion of constituents of blood out of the blood into the dialysis fluid. if these substances are lacking in the patient, they will diffuse into the patient’s blood instead
features of dialysis machine
metabolic waste products are absent from the dialysis fluid
- to establish a steep concentration gradient for efficient diffusion of waste products out from the patient’s blood into the dialysis fluid, hence there is an effective removal of metabolic waste products
features of dialysis machine
dialysis fluid flows in the opposite direction to the flow of blood
- to maintain steep concentration gradient for the efficient diffusion of substances between the patient’s blood and the dialysis fluid.
