Unit 5 - Excretion, homeostasis and the liver Flashcards
Respiratory acidosis
Effect of lowered blood pH (excess CO2)
Why must nitrogenous compounds be removed from the body
This is because the body cannot store amino acids, but it would be toxic to excrete them
Deamination
Process by which potentially toxic NH2 group is removed from amino acids to produce keto acids and ammonia. The ammonia is then coverted into urea (less toxic)
Where is CO2 from respiring tissues excreted
Lungs
Where is water from respiration excreted
Lungs
Bladder
Skin
Where is urea from the kidney excreted
Bladder/ kidney
Where are poisons excreted
Liver
Bladder
Where are drugs excreted
Liver
Bladder
Where are bile pigments from liver reactions excreted
Rectum (bilirubin in faeces)
Excretion
Removing metabolic waste from the body
Hepatic Portal Vein
Carries blood loaded with the products of digestion straight from the intestine to the liver (75% of the blood)
Hepatic Artery
Supplies liver w/ oxygenated blood (25% of the blood)
Hepatic Vein
Connects to inferior vena cava and carries deoxygenated blood back to heart
Sinusoids
Run from central vein to portal triads. Mixing increases O2 content of the blood from hepatic portal vein
Kuppfer cells
Hepatic macrophages that move within sinusoids
Ingest foreign particles
Recycle old RBC’s
What do hepatocytes do
Relatively unspecialised to carry out many functions
Synthesise proteins (enzymes and hormones)
Transform and store carbs (glycogen)
Synthesise cholesterol and bile salts
Form bile and secrete into bile canaliculi
Absorb substances from blood and also secrete products
Shape of hepatocytes
Cuboidal w/ many microvilli (increases SA for contact w/ sinusoids)
Organelles in hepatocytes
Rough ER
Golgi Apparatus
Mitochondria
Vesicles
Role of the liver in excretion
Break down excess amino acids and haemoglobin
Detoxifies alcohol
Produces urea
Basic functional unit of liver
Lobule
Protein metabolism in the liver
Protein synthesis of plasma proteins
Deamination to form keto acid and NH2
Transamination to make new amino acids
Fate of keto acids
Kreb’s cycle (respration)
Portal triads
Hepatic Artery
Bile duct
Hepatic Portal Vein
Bile canaliculi
Drains bile from hepatacytes to bile duct
Where does deamination occur
In hepatocytes
Keto acid
An acid with a carboxylic acid group and a ketone group
Equation of deamination
Amino acid + oxygen —> keto acid + ammonia
Ornithine cycle
2NH3 + ornithine + CO2 (from respiration) —> H2O + urea (circulates in blood until filtered by kidney)
Detoxification of alcohol
Alcohol is broken down by hepatocytes by alcohol dehydrogenase to make ethanal which is further dehydrogenated by ethanal dehydrogenase to make ethanoate
NAD is needed to oxidise and breakdown fatty acids
Uses of ethanoate
Build up fatty acids
Cellular respiration
Pressures in the glomerulus
Hydrostatic pressure
Oncotic pressure
Capsular pressure
Calculating net pressure in the nephron
Hp - (Op + Cp)
Where does blood leave from the nephron
Efferent arteriole
Whats in the glomerular filtrate
Glucose Amino acids Ions (sodium, potassim, etc) Urea Water
Where does ultrafiltration occur
Bowman’s Capsule
Process of ultrafiltration
Blood flows through fenestrations in endothelium then basement membrane then podocytes (3 layers)
Basement membrane consists of fine mesh of collagen fibres and glycoproteins, preventing proteins and rbc’s leaving
Podocytes have projecting fingers that wrap around capillaries
Tiny slits are left between interlocked podocytes
How does blood reach Bowman’s capsule
Diameter of afferent arteriole > diameter of efferent arteriole
Build up of hydrostatic pressure in glomerulus capillaries so blood is forced through slits of podocytes into Bowman’s Capsule
Components of nephron
Glomerulus Bowman's capsule Loop of Henle Proximal convoluted tubule Distal convoluted tubule Collecting duct
Glomerulus
High hydrostatic pressure mass of capillaries that filters blood
Function of proximal convoluted tubule
Selective reabsorption
Function of the Loop of Henle
Osmoregulation - creates a high conc. of Na+ and Cl- in the tissue fluid of the medulla to allow water to be reabsorbed in the collecting duct
Hairpin counter current multiplier
Collecting ducts
Where several tubules join to collect the filtrate and final sodium regulation takes place in the ureter
Features of proximal convoluted tubule
Form microvilli (increases SA for reabsorption) Many mitochondria Sodium/ potassium pump RER to synthesise proteins Co transporter proteins Vesicles to transport substances across cell Tight junction between cells to prevent filtrate passing between cells
Selective reabsorption
All glucose, amino acids, hormones, vitamins, and 65% Na+ and Cl- and some water are reabsorbed back into the blood
Na gets actively transported out of cytoplasm of PCT cells (Na/K pump in outer membrane)
Glucose or amino acids enter cells with Na+ by facilitated diffusion (co transporter proteins)
Water and Cl- diffuse down conc gradient as wp has increased
Blood now flowing is isotonic to tissue fluid and glomerular filtrate
All diffuse into extensive network of capillaries
Survival advantage of Loop of Henle
V. concentrated urine can be produced
Conserves water and prevents dehydration
Descending limb of Loop of Henle
Water moves down conc. gradient from nephron and into surrounding fluid (high salt conc.)
Ascending limb of Loop of Henle
In the lower part, fluid is v. concentrated and Na+ and Cl- diffuse out into surrounding tisues
In the upper part, there is active transport of Na+ and Cl- out of the nephron. Increases water potential of fluid inside nephron (water moves out)
Functional unit of kidney
Nephron
Why do we call the processes in the Loop of Henle ‘counter current multiplication’
Multiplies effect of gradient
Osmoregulation
Process by which organisms regulate water content of the body
What happens a when the water potential of the blood rises above normal
Change detected by osmoreceptors in hypothalamus
Posterior pituitary gland releases less ADH
Decrease in permeability of collecting ducts
Dilute urine
What happens if the water potential of the blood falls below normal levels
Change detected by osmoreceptors in hypothalamus
Posterior pituitary gland releases more ADH
ADH increases permeability of collecting ducts
Concentrated urine
Osmoregulation at the collecting duct
ADH released by posterior pituitary gland diffuses out of the capillaries
ADH detected by cell surface receptors on the cells of the collecting ducts
Cascade of enzyme reactions triggered by cAMP
Vesicles containing aquaporins fuse to membranes of cells that line CD
More H2O absorbed in the blood
Aquaporins
Channel proteins for H2O
GFR < 60
Chronic kidney disease
GFR < 15
Kidney failure
Treatment for kidney failure
Haemdialysis
Peritoneal dialysis
Transplant
What does dialysate contain
Correct conc for body (same conc as normal blood)
Includes water, glucose, salts and electrolytes
No urea
hCG
A hormone released by pregnant women which prevents uterus lining from shedding
Haemdialysis
Short term
Works inside body
Blood from artery flows into dialysis machine w/ blood thinners where it flows through a partially permeable membrane (basement membrane)
Lose excess ions and urea through diffusion
Blood and dialysate flow in opp. directions to maintain countercurrent exchange system (maximise rate of diffusion)
Cleaned blood returns to veins
Peritoneal dialysis
Short term
Works inside of the body
Abdomen has natural dialysis membrane - peritoneum
Dialysis fluid introduced into abdomen using a catheter - takes place across peritoneum
Urea and excess mineral ions diffuse out of the blood into tissue fluid and out of peritoneal into dialysate
Fluid is then discarded leaving blood balanced
Kidney transplants
Long term (8-10 years) Works inside the body Blood vessels are joined and the ureter of the new kidney inserted into the bladder Tissue types should be matched to reduce chances of rejection
Pros of kidney transplant
Long term
Free from dialysis and dietary monitoring
Healthy kidney
Cons of kidney transplant
Chance of rejection
Always has to take immunosuppressants
Pros of peritoneal dialysis
Can be done at home
Patients can live relatively normal lives
Cons of peritoneal dialysis
Needs to be done 4 times a day
High risk of infection
Pros of haemdialysis
Needs to be done 3/4 times a week
Adds to life expectancy
Cons of haemdialysis
High risk of infection
Sessions are time consuming
Have to be careful managing diet
Quite expensive
Monoclonal antibodies
Produced from one plasma cell
Relationship between length of Loop of Henle and conc of urine
Longer the loop of henle, more ions pass out of ascending limb into medulla
Lowers wp in medulla
More water can be reabsorbed back into blood
Why is protein in urine a sign of chronic high blood pressure
High bp causes larger substances to force through basement membrane and damage capillaries
How do pregnancy tests work?
Urine on reaction site travels up and monoclonal antibodies complementary to hCG bind to hCG in urine.
Mobile antibody/hCG complex binds to immobilised antibodies attached to test site
This activates dyes
How do you know of a pregnancy test is working
Any excess mobile monoclonal antibodies from the reaction site bind to immobile antibodies at the control site
What else can urine test for
Anabolic steroids
Anabolic steroid tests
Used to boost muscle growth and strength
Urine can be tested by gas chromatography in which a gaseous solvent separates substances or mass spec
Kidney dissection
Cut kidney in half (lengthways)
Cortex is lighter than medulla
Medulla contains renal pyramids (striped and cone shaped)
Why do the renal pyramids appear stripy
Contain sections of the nephron e.g. collecting duct and loop of henle
Where does the first part of the ornithine cycle occur
Mitochondria
Characteristics affecting use of creatinine phosphate levels to estimate GFR
Diet - effects levels of cp
Exercise levels - more active patients have a higher conc of cp
Ethnicity/ genetic makeup - Diff alleles affect metabolism of cp
Gender - men and women have diff muscle mass
Effects of kidney failure
Loss of electrolyte balance
Build up of urea in blood
High bp
Weakened bones - Ca/P balance in blood lost
Pain and stiff joints - abnormal proteins build up in the blood
Anaemia
Storage of glycogen
Approx. 100-120g
Stored as granules in cytoplasm
H2O2
Harmful waste product of many metabolic processes
Cytochrome P450
Group of enzymes used to breakdown drugs and have a role in e- transport in respiration
These two functions can interfere w/ each other
What causes fatty liver
If hepatocytes detoxify too much alcohol, lipids are stored in hepatocytes causing the liver to become enlarged
Which liver cells lead to regeneration of the liver
Hepatocytes through cell division (mitosis)
Distal convoluted tubule
Involved with balancing water and salt levels depending on needs and blood pH
Any reabsorption is done actively as all fluids are isotonic
