Extretory System Flashcards
homeostasis
an organism’s ability to maintain a constant internal environment
what does the internal environment involve
tempetature, fluid balance, chemistry in the body
excretion
the removal of waste products of metabolism from the body
what are the organs of excretion
skin
lungs
kidneys
how does the excretory system play a role in homeostasis
by regulating body temp-skin
by maintaining fluid balance
what is the largest organ in our body?
the skin
what do the kidneys produce
urine
what is urine made up of
urea, water, salt
what does the skin excrete
sweat (water and salt)
what do the lungs excrete
co2 + water vapour
what do the kidneys excrete
urine
what are the 2 layers of the skin
epidermis
dermis
what is the epidermis made up of
malpighian layer
granular layer
cornified layer
where is the epidermis
outer layer
what does the malpighian layer produce
new cells due to lots of mitosis
what does the granular layer produce
keratin produced causing cells to harden
what does the cornified layer produce
cells die and shed
melanin
pigment that gives us our skin colour
produced by specialised cells in the Malpighian layer
what is the dermis made of
connective tissue and collagen
contains: sweat glands, hair follicles, sebaceous glands
functions of the skin
protection
sense organ
vitamin D production
food storage
excretion of water and salts
temperature regulation
what is the subcutaneous layer?
lies beneath the dermis. contains adipose tissue that protects internal structures and insulates the body
how much does temperature fall by when sleeping
1 degree
why does body temperature fall at night
because less respiration is happening
why does our temperature rise when we are sick?
to destroy the invaders
what things cause slight temperature fluctuations
puberty, menopause, menstrual cycle
vasodilation
blood vessels in the skin expand and move closer to the surface of the skin causing heat loss and cooling us down
sweat
salt and water released through pores onto skin. water evaporates off the surface of the skin cooling us down
why is it important to drink fluids during and after excersise?
water lost through sweating must be replaced to maintain water balance
piloerection
erector muscle contracts which cause hairs to stand up. a layer of warm air is trapped close to the surface of the skin by the hairs reducing heat loss
vasoconstriction
blood vessels in the skin contract and move away from the surface of the skin when we are cold to reduce heat loss
shivering
is the brains response to cold temperature is to cause muscles to contract and relax rapidly to raise body temperature
what does the ureter do
carries urine from kidneys to bladder
what does the urethra do
takes urine out of the body
where is urea made?
the liver
what is urea composed of
excess amino acids
what is the kidneys’ job
to filter the blood
where does filteration occur
cortex
where does reabsorption occur
medulla
what molecules are too large to be filtered from the blood?
red blood cells and proteins
what filters out of the blood?
amino acids, water, glucose, urea salts
why is it important for glucose to be reabsorbed
if it is not, it is an indication of diabetes
where is the bowmans capsule
cortex
where is the loop of henele
medulla
where is the distal/ convoluted tubules
medulla
where exactly does filtration and reabsorption occur?
the nephron
where in the nephron does filtration occur
bowmans capsule
where in the nephron does reabsorption occur
proximal + distal convoluted tubules
how many nephrons are there in each kidney
approx 1 million
what is a nephron
structure in the kidney that filters blood and produces urine
describe how filtration occurs in each nephron
bowman’s capsule surrounds a glomerulus. here smaller molecules in the blood are forced under pressure out of the plasma forming the glomerular filtrate
what is the glomerulus
a ball of capillaries
what is glomerular filtrate
substances that have been removed from the blood
how does the glomerulus help filtration
high pressure
large surface area
walls that are one cell thick
describe how reabsorption works in the nephron
the body reabsorbs most of the glomerular filtrate back as it cannot afford to lose the useful chemicals
describe the proximal convoluted tubule’s role in reabsorption
most water reabsorbed by osmosis
glucose/amino acids/vitamins reabsorbed by active transport and diffusion
most salt reabsorbed by AT and diffusion
describe the distal convoluted tubule’s role in reabsorption
careful control of water salt and pH balance to determine the volume and concentration of urine
ADH causes walls to become more permeable to water so some salts and water can be absorbed if necessary.
describe the loop of Henle’s role in reabsorption
descending = permeable to water only, some water and minerals reabsorbed
ascending = impermeable to water. some salts are reabsorbed by diffusion and AT at the top of the loop
describe the collecting duct’s role in reabsorption
small amount of water reabsorbed by osmosis
where do the left-over wastes go when they reach the collecting duct
forms urine, moves from collecting duct of nephron to pelvis of kidney
what is osmoregulation
the kidney regulating the amount of water in the body by varying the amount of urine produced
what hormone controls osmoregulation
ADH (anti-diuretic hormone)
what does ADH control
whether the distal tubule and collecting ducts reabsorb water or not
where is ADH made
hypothalamus
where is ADH stored
the pituitary gland
what happens if you drink enough water
the hypothalamus detects the diluted blood and turns off ADH production
less water is reabsorbed so a larger volume of urine is produced
what happens if you don’t drink enough water?
ADH is secreted from pituitary gland
more water is absorbed, and a small volume of urine is produced
target area of ADH
distal convoluted tubule+ collecting duct
effects of ADH
causes DCT and collecting duct to become more permeable to water
what is the stem of the renal artery?
aorta
what is the stem of the afferent arteriole
the renal artery
