Excretory system Flashcards
What is the process of excretion?
it is the process of separating and removing metabolic wastes from the body
what does homeostasis refer to
refers to the ability of an organism to maintain its internal makeup, and maintain fairly stable conditions necessary for survival.
what happens during the metabolic processes of the body
waste products are removed from the site of production by the blood
what happens as wastes accumulate
the kidney removes them from the blood and excretes them to the environment
what does the kidney turns the excretory products into
urine
what do the kidneys filter and regulate from the blood
- they regulate the amount of water, salts, and other substances in the blood
- ## they remove nitrogenous wastes (urine) and excess salts from the blood
what are the three functions of the excretory system
- EXCRETION of metabolic wastes
- OSMOREGULATION: regulation of water and salt in body fluids
- REGULATION of body fluid composition (ex: pH, etc.)
What are 3 nitrogenous wastes
- Ammonia
- Urea
- uric acid
what is ammonia (5)
- the first metabolic product of amino acid deamination – (protein digestion).
- highly toxic
- cannot accumulate in the body
- must be converted into less toxic: uric acid and urea
- quickly converts into the less toxic form
what is amino acid deamination
- IN situations of excess protein intake, deamination is used to break down amino acids for energy. the amino group is removes from the amino acid and converted into ammonia
- the removal of an amino group from a molecule
what is urea (7)
- only in mammals
- converted from ammonia
- less toxic than ammonia
- produced in the liver from the breakdown of protein
- can be excreted in concentrated form
- problem: requires more water to excrete than uric acid
- the main component of urine
what is uric acid (5)
- (in birds)
- produced from ammonia
- not very soluble. can be excreted as a paste with little water loss
- non-toxic
- usually produced from breakdown of DNA or RNA
what are ureters
they are tubes that carry urine from the pelvis of the kidneys to the urinary bladder
what is the urinary bladder
it temporarily stores urine until it is released from the body
what is the urethra
the tube that carries urine from the urinary bladder to the outside of the body.
what is a sphincter
it is a circular muscle that controls the outer end of the urethra, there are two of them. it is to prevent drainage. the inner most one is involuntarily controlled by the brain. during childhood, we learn to volunarily control relaxation of the other one
what is the principle function of the kidney
it is to filter blood in order to remove cellular (consisting of living cells) waste products from the body. It also maintains water balance.
how much blood is in the kidneys at any given time
20%.
What happens if one human kidney fails to work
-humans can function with one kidney
- if one ceases to work, the other increases in size to handle the workload
What are some examples of cellular wastes the kidney excretes?
- urea
- Uric acid
- creatine
what is creatine
a waste product of muscle action
the kidney is composed of three sections, which are
- the outer (renal) cortex
- the (renal) medulla
- the hollow inner (renal) pelvis
cortex
the outside of the kidney. it is where the blood is filtered
medulla
- contains the collecting ducts with carry filtrate (filtered substances) to the pelvis
pelvis
a hollow cavity where urine accumulates and drains into the ureter
deamination (2)
- excess proteins are turned into carbs, but the NH3 needs to be discarded
- The liver converts 2 ammonia molecules and CO2 into urea
nephrons (4)
- the filtering units of the kidney, filtering various substances from blood, transforming it into urine.
- approximately one million nephrons in each kidney
- located within the cortex and medulla of the kidney
- tubes of the nephrons are surrounded by cells and a network of blood vessels
Each nephron consists of the following parts
- glomerulus
- bowmans capsule
- proximal tubule
- loop of henle
- distal tubule
- collecting duct
label the kidney
a
label the nephron
a
bowman’s capsule
a double walled, cup-shaped structure
1. large pores to allow water and dissolved substances through
2. blood pressure in the glomerulus is high, which forces filtration
- in each capsule, the renal artery enters and splits into a network on capillaries called the glomerulus
glomerulus
- network of capillaries within the bowmans capsule
- acts as a filtration device
- high pressure (4x higher than in the capillaries (bundle of microscopic blood vessels))
- moves water and solutes (no proteins) from blood into the nephron
- where filtration of blood plasma occurs; plasma that enters capsule = FILTRATE
- moves filtrate into Bowmans capsule
proximal tubule
- leads from the bowmans capsule to the loop of henle
- mitochondria help with activetransport, passive transport also used
- active transport of many valuable substances back into blood network happens here
in the proximal tubule, what are the substances that go back into blood network by active transport? what doesnt get reabsorbed back into the blood?
- glucose
- amino acids
- sodium
not:
- urea
- some salts
- other toxic substances
loop of henle
- the long hair-pin that extends into medulla
- some of the remaining water, ions, and salt in the (glomerular) filtrate will be returned to the blood
distal tubule
- like the proximal tubule, but on the opposite side
- connects the loop of henle to the collecting duct
distal tubule and collecting ducts
- more water reabsorption occurs here
- this depends on the presence of certain hormones – antidiuretic hormone (ADH)
- EXACT amounts of substances are reclaimed to the blood (very precise)
what is not considered to be a process of excretion
wastes of food residue– feces