5.1.2 excretion as an example of homeostatic control Flashcards
excretion defintion
removal of metabolic waste from the body
importance of removing metabolic wastes?
- eg urea, CO2
- part of homeostasis and maintaining metabolism
- toxic if accumulates in the body. alter pH, and can act as enzyme inhibitors
3 main metabolic waste products
co2
bile pigments
urea
role of lungs in excretion
- CO2 produced as waste product of respiration
- diffuses from respiring tissues into bloodstream, trnasported MOSTLY AS HCO3- to the lungs
- diffuses into alveoli to be exhaled
role of skin in excretion
sweat contains urea, salts, uric acid, water, ammonoia
name of 3 blood vessels in liver
- hepatic vein
- hepatic portal vein
- hepatic artery
hepatic vein
- takes the DEOXYGENATED blood from the liver, joins the vena cava and back to lungs to be oxygenated
how to idnetify hepatic vein in histology
LARGEST LUMEN
hepatic artery
- oxygenated blood goes from heart to aorta to liver via here
hepatic portal vein
- DEOXYGENATED blood from the digestive system carrying digestive (someties toxic) products
need for oxygen
- aerobic respiratoin
- last electron accepter in ox phos
bile duct
carried bile from liver to gall bladder
interlobular vessel is …
branch of hepatic vein (central vein)
sinusoid
blood capillary connecting the ha and hpv to hepativ vein
features of hepatocytes
-MULTIPOTENT, so liver can repair itself
- microvilli
- large nucleis
- lots of golgi
- lots of mitochonrdira
KUPFFER CELLS
- macrophages that move within sinusoids
primary function of kupffer cells
- phagocytose erythrocytes
- digest Hb, made of the haem and protein
- protein goes to AA
- haem goes to IRON (goes to bone marrow and used to produce RBC) and bilirubiin (bile pigments) which are used to produce bile
production of bile
- bile released into bile CANNALICULUS
- goes to BILE DUCT
- transports bile to gall bladder
purpose of bile
EMULSIFICATION and NEUTRALISATION of digested material entering small intestine
function of liver: storage of glycogen (and discuss benefits of glycogen)
- stores glucose in the form of glycogen
- glycogen is: compact, insolubel so doenst affect water potential, and many branched ends for enzymes to attach to the break down fast
formation of urea
- excess amino acids
DEAMINATION:
amino acid + oxygen = ammonia + keto acid
ORINITHINE CUCLE: NH3 and co2 to form UREA amd water
role of liver: hydrogen peroxide
- catalase enzyme breaks it down into water and oxygen
role of liver: alcohol
- alcohol dehydrogenase converts ethanOL to ethanAL
- ethanal dehydrogenase converts ethanAL to ethanoate
- binds w coenzyme A and enters respitartion
why is it important to orinithine cycle quickly
- ammonia v SOLUBLE nad toxic; bad to let it build up
how is high pressure created in the glomerulus?
- diameter of lumen of AFFERENT arteriole wider than that of EFFERENT
- pv constant, therefore vol decreases, pressure increases
renal artery leads to …
glomerulus (cortex)
renal vein leads to …
loop of henle (medulla)
3 layers of ultrafiltraion
- gaps between endothelial cells, fenestrations
- basement membrane (collagen and glycoproteins)
- podocytes. major processes, minor processes
how to recognise BC on a microscope pic
clear ring of c witohut a stain
basement membrane prevents what
anything with an MR of greater than 69000 from leaving
name 5 things filtered out in ultrafiltration
- water
- glucose
- amino acids
- inorganic ions
- urea
what is left in the capillary after ultrafiltraion
- blood cells
- proteins
2 functions of kidney
- filter waste from bloood
- osmoregulation
how to recognise PCT cell vs DCT cell
- PCT brushed border; microvilli
- PCT smaller lumen
what happens in PCT
- selective reabsorption of GLUCOSE and amino acids
adaptations of PCT cells
- folded cell membrane to form microvilli ==> more SA for reabsorption
- CSM contains cotransport proteins
- many mitochondria to produce lots of ATP
mechanism of reabsorption in PCT
- SODIUM POTASSIUM PUMP: Na+ ACTIVELY pumped OUT of PCT wall, K+ pumped IN.
- concentration of Na+ lower inside cells than outside filtrate, creating a CG
- Na+ moves down concentration gradient by facilitated diffusion using a COTRANSPORT PROTEIN (with glucose or AA at the same time)
- Lowering WP, so water moves in by osmosis
- increasing conc of glucose/ aa so it FACILITATED DIFFUSES out through channel protein into the blood
need for glucose
- respiratory substrate
- required for glycolysis
mechanism of loop of henle
DESCENDING LIMB:
- water permeable
- down the limb, water moves out into capillaries by osmosis thanks to aquaporins (phospholipids are hydrophobic)
- at the same time, na+ and cl- diffuse into LoH
ASCENDING LIMB
- AT THE BASE: mineral ions diffuse out
- as u go up, they move out to medulla by active transport
- no movement of water
- now the wp of medulla is very low, so water continues to move out of descending limb
collecting duct (finishing loop of henle)
- fluid passes through tissues with an ever decreasing WP as na+ actively trnasprted out
- so water moves out by osmosis into capillaries
- increasing conc of urine
describe conc of glucose as it goes along nephron
- high in the PCT
- sharp decrease back to 0 as glucose is reabsorbed back into the bloodstream
describe conc of Na+ as it moves thorugh the nephron
- constant in PCT
- increase in the loop of henle at first (diffusion into the ascending limb)
- then decrease (active transport out of ascending limb)
describe conc of urea as u move throughout the nephron
- rises gradually throughout as water is withdrawn from the tubule
what animals have long loops of henle
- eg camels
- those living in water deprived aras
- long loops of henle so max vol water can move out by osmosis into bloodstram
- smaller volume of more conc. urine
describe osmoregulation
- hypothalamus in the brain contains osmoreceptors
- when WP is low (very negative) osmoreceptor cells lose water by osmosis, become crenated, stimualtes:
- ADH produced in hyp, then stored in and released from posterior pituitary gland
how does ADH work
- WP low, detected by osmoreceptors
- ADH released by posterior pituitart
- ADH binds to receptrs in the walls of the collecting duct
- chain of enzyme controlled reactions
- vesicles containing aquaporins fuse w CSM, so walls more permeable to water
- water moves into bloodstream by osmosis
example measure of how to assess kidney function
GFR
(glomerular filtrate rate)
GFR values
- normal: 90-120
- disease <60
- failure <15
heamodialysis
- filters the blood
- blood leaves from artery into dialysis machine, flowing through a partilaly permeable dialysis membrane
- add HEPARIN TO AVOID CLOTTING during dialysis
- artificial capillaries surrounded by dialysis fluid flowing in the opposite direction (countercurrent mechnaism for a steep cg)
- blood reenters in a vein
kidney translplant
- involves major surgery
dialysis +-
- allows u to live
BUT - 2/3 times a week at a clinic for several hours
transplant + (3)
- no time consuming dialysis
- physically fitter
- better QOL, can travel
transplant -
- immunosuppressant drugs
- major surgery under GA
- risk of rejection
- drug side effects
3 uses of urine analysis
- preganancy test
- anabolic steroids
- glucose for diabetes
pregnancy testing
- when ur pregnant, you produce hCG
- protein smaller than 69000 so can pass from blood into filtrate at BC
1. urinate on test stick
2. hCG binds to MOBILE antibodies with a dye, as hormone is COMPLEMENTARY to antibody
3. they move down test stick
4. if hCG present: it binds to fixed antibodies holding dye in place, forming a line
4. mobile antibodies with NO HCG bind to another site to prove test is working
how to identify hepatic portal vein
blood enters liver through branched vessel
adaptations of sinudoid cells (2)
- flat cells -> short diffusion distance
- fenestrated -> increases permeability
why can’t podocytes divide by mitosis? (3)
- alraedy differentiated
- it would alter the number of fenestrations
- so negatively affect ultrafiltration
2 factors affecting GFR
- age: it declines with age
- gender: men and women have different muscle mass
purpose of microvilli (2)
- increase SA for resabsorption
- cotransport proteins for active transport
where does ADH act
collecting duct
descrive effect of a longer loop of henle
LONGER DESCENDING:
- more water moves OUT by osmosis, more na+ and cl- move IN by diffusion
LONGER ASCENDING:
- lower volume of water stays constant
- more active transport of na+ and cl- OUT into the medulla
- wp outside nephron decreases, more water reabsorbed in the CD to bloodstream
- smaller vol of more conc urine
PCT adaptations (4)
- microvilli = increased SA for reabsorption
- many mitochondria = more ATP , more energy, active transport with sodium potassium pump
- lots of ribososmes to produce proteins
- carrier/cotransport proteins in the cell membrane
what type of vessel is the intralobular vessel in liver
vein
what tissues line the pCT
epithelial
what pressure is high in the glomerulus
HYDROSTATIC
Explain the need for close matching of the donated kidney to the recipient (3)
- DONATED KIDNEY recognised as foreign
- different antigens on the surface of csm
- causing rejection and immune response
- need to take immunosuppressants
lots of creatinine =
low GFR = problem
where is MOST water reabsorbed into the blood
PCT
simple role of loop of henle
decrease water potential going down medulla
why is deamination better than straight excretion of the amino acids
- lose our keto acids
- can be used in respiration
adaptation of kidney cortex?
- dense capillary network to supply nephrons with lots of blood
what happens in the pelvis of kidney?
urine collects before passing into ureters
why might glucose levels decrease a bit despite reabsorption?
- needed to respire
- to make ATP
- to release energy fro active processes eg selective reabsorption the sodium potassium pump
why does a longer looper henle help those in a drier environment? (3)
- more na+ cl- ions actively transported out of ascending limb into medulla
- greater WPG in the medulla
- more water reabsorbed from the CD into the blood
how many sides of a lobulbe
6
what type of cell is hepatocyte
epithelial
bile duct direction of flow
opposite to the HPV nad hepativ artery in the sinudoid
bile goes to where
gall bladder
importance of excreting CO2
- Co2 + h2o in presence of carbonic anhydrase = carbonic acid. H2CO3 = H+ + HCO3-
- H + alter pH, and interact with tertiary structure HB, lowering affinity for oxygen. also form haemoglobinic acid
- co2+ Hb = carbaminohaemoglobin, also has a lwoer affinity for oxygen
urea compared to ammonia
- less soluble
- less toxic
adaptations of PCT cells
- highly folded CSM to form microvilli. increases SA for reabsorption
- cotransport proteins in CSM
- many mitochondria, lots of ATP for active transport
name of arrangment in loop of henle
- hairpin countercurrent multiplier system
