excretion, topic 5 pt1 Flashcards
what is homeostasis?
the ability of an organism to maintain it’s internal makeup
why is homeostasis sometimes called dynamic equillibrium?
because the body bounces between two set limits, one high and one low
what is excretion?
the process of removing metabolic wastes from the body
what is the product of excretion?
urine
how are waste products removed from cell production site?
by the blood
what does the kidney remove?
the waste and excretes it from the environment
what are the 3 functions of the excretory system?
- excretion of metabolic wastes
- osmoregulation
- regulation of body fluid composition (pH etc…)
what is osmoregulation?
regulation of water and salt in body fluids
what are 3 waste products in the excretory system?
-carbon dioxide
-water
-nitrogenous wastes (products of protein and nucleic acids digestion)
how is carbon dioxide excreted?
through the skin and respiratory surfaces
how is water excreted?
through the skin, respiratory surfaces and kidneys
how are nitrogenous wastes excreted?
mainly through the kidneys, and some from the skin
what are 3 nitrogenous wastes?
- ammonia
- uric acids (in birds)
- urea (in mammals)
can ammonia accumulate in body?
no
why and what does ammonia need to convert into?
Because it is very toxic.
-converts into less toxic uric acid and urea
what is uric acid converted from?
ammonia
-uric acid is non toxic
is uric acid soluble?
not really, can be excreted as a paste with little water loss
what is urea converted from?
ammonia
-urea is less toxic than ammonia
what is urea produced by?
the liver
how is urea excreted?
in a concerntrated form
-requires more water to excrete than uric acid
what do the kidneys produce?
urine by filtering the blood
what do the 2 ureters do?
transport urine from kidneys to bladder
what does the urinary bladder do?
stores urine
what does the urethra do?
carries urine to environment
what are the 3 kidney parts?
- cortex: outer region
- medulla: just below the cortex
- pelvis: a hallow chamber within the medulla
what are the cortex and medulla of each kidney made up of?
about one million nephrons
what is a nephron?
structural and functional unit of the kidney
what is the bowman’s capsule?
double walled chamber (start of the tube)
what is the glomerulus?
a network of capillares within the bowman’s capsule
what happens in the glomerulus?
filtration of blood plasma (particle size and blood pressure)
what does high pressure do regarding the glomerulus?
plasma passes through holes in the glomerulus into the bowman’s capsule
what happens when plasma enters the capsule?
it is filtrated
what does the proximal tubule do?
active transport of valuble substances back into the blood
-glucose, amino acids, sodium ions
do all substances get reabsorbed in the proximal tube?
no
-urea, toxic subtances, some salt and alot of water dont get reabsorbed here
