Homeostasis and Human Excretory System Flashcards
excretion
the removal of waste products of metabolism from the body
nephron
the functional unit of the kidney
produces urine
homeostasis
the maintenance of a constant internal environment
endotherm (warm blooded animals)
keep body temperature constant even in cold external conditions by increasing metabolic rate (respiration)
eg birds, mammals
ectotherms (cold blooded animals)
body temperatures vary with that of the environment
eg reptiles, fish, amphibians
vasodilation
blood vessels near the surface of the skin dilate
vasocontraction
blood vessels near the surface of the skin narrow (constrict)
osmoregulation
the control of water or salt levels in the cell or organism
active transport
absorption of substances into cells against a concentration gradient, requiring energy
waste products of homeostasis
skin- source: sweat gland
sweat -> water and salt
lungs - source: break down of carbs in respiration
carbon dioxide
liver- source: deamination of amino acids
urea
skin
regulates body temp
liver and pancreas
regulate blood glucose level
kidneys
regulate water and salt concentration
importance of homeostasis
allows organisms to function efficiently and independently of their external environment
eg constant internal temp required for enzyme action to work efficiently
efficiency of exchange of substances is proportional to the surface area over which diffusion can take place
how unicellular organisms function in homeostasis (amoeba)
no excretory organs: large surface area for exchange of materials
how multicellular organisms function in homeostasis
in humans:
-lungs contain alveoli: excrete co2 which regulates blood pH
in plants:
-stomata: leaves are flat for efficient diffusion of gases
human excretory system parts
kidney
skin
lungs
renal artery
transport blood from heart to kidney
renal vein
transport blood from kidney to heart
kidney
- removal of waste products from the blood and production of urine
- osmoregulation
located in the lower abdominal cavity
ureter
transport urine from kidney to bladder
bladder
stores urine
sphincter muscle
keeps urine in the bladder
urethra
transports urine from bladder to outside the body
adrenal gland
production of adrenaline
cortex
filtration and reabsorption
medulla
reabsorption
ureter
transport urine from kidney to bladder
steps in the production of urine
- filtration : removal of waste products from the blood to the kidney
- reabsorption: useful nutrients returned back into the bloodstream from the kidney
- secretion: active transport of substances from blood to the kidney ( potassium ions, hydrogen ions, urea)
glomerulus and bowman’s capsule function
filtration
items filtered out of the blood into the bowman’s capsule
glucose
urea
salts and water
items that remain in the blood from bowman’s capsule
hormones (too big)
protein (too big)
RBCs, WBCs, platelets
glomerular filtrate vs urine
g . f.
more water
more glucose
amino acids
urine
less water
no glucose
no amino acids
adaptation for efficient filtration at glomerulus
large surface area with capillary network
many pores in glomerulus, b.cap. 1 cell thick
blood pressure is high: efferent arteriole narrower than the afferent arteriole, so force filtering the plasma
proximal convoluted tubule
function: reabsorption glucose vitamins amino acids 80% salts and water
method of reabsorption: diffusion and active transport
adaptations for reabsorption in the proximal convoluted tubule
long (allows time for reabsorption)
many villi in its cells (larger surface area)
high conc. of mitochondria (energy)
walls only one cell thick (diffuse easily)
loop of henle
function: reabsorption of water and salts
descending loop: water (osmosis)
ascending loop: salts (diffusion/active transport)
distal convoluted tubule
functions: reabsorption, secretion of k+ and h+ ions, drugs
if blood is too acidic= h+ conc. very high
h+ ions secreted into the urine at the d.c.t.
by controlling the hydrogen ion conc. in blood, the kidneys control blood pH
collecting duct
function: reabsorption of water
hormone: ADH anti diuretic hormone
site of production: hypothalamus
site of secretion: pituitary gland
site of action: collecting duct
outline process of osmoregulation when body is low on water
blood = increased salt concentration ADH secreted from pituitary gland collecting duct becomes permeable more water is reabsorbed small volume of urine produced less salt in blood
outline process of osmoregulation when body is high in water
blood = too dilute, decreased salt conc.
ADH produced is inhibited
collecting duct becomes impermeable
less water reabsorbed into the blood
larger volume of dilute urine is produced
salt conc. is unchanged in blood
functions of the skin
1. protection epidermis- prevents entry of pathogens melanin- protects against UV rays sebum- keep hair moist, protects skin from cracking, acidic nature kills bacteria 2. excretion (water, salt, sweat) 3. temp regulation 4. vit D production
epidermis cells
produce keratin
build up of keratin causes hardening of cells
more keratin causes cells in cornified layer to die
malpighian layer
produces melanin (protects against UV)
dermis
contains connective tissue (collagen)
protects internal organs
why we sweat
skin receptors detect change in temp. send message to the brain:
- more sweat is produced by sweat glands
- vasodilation of skin arterioles
vasodilation of skin arterioles
blood vessels near the surface of the skin dilate
more blood flows near the skin surface
heat lost by evaporation of sweat
skin in cold conditions
skin receptors detect change in temp. send messages to the brain:
- piloerection
- vasoconstriction of skin arterioles
- increased metabolism (more thyroxine produced, more heat generated from respiration)
piloerection
erector muscles contract
pull hairs erect for trapping more air
thicker layer of air close to skin acts as a good insulator of heat
vasoconstriction of skin arterioles
blood vessels near the surface of the skin narrow
to let less blood flow near the skin surface, reducing heat loss
