Liver and Excretion Flashcards
what is excretion
process by which toxic waste products of metabolism are removed from the body
what are examples of metabolic waste products
Carbon dioxide
- waste products of cellular respiration
- excreted from the lungs
Bile Pigments
- formed from the breakdown of haemoglobin from old red blood cells in the liver
- excreted in the bile from the live into the small intestine via the gall bladder and bile duct
Urea
- formed from the breakdown of excess amino acids by the liver
- excreted by the kidneys in the urine
what are the vessels in the liver
- very rich blood supply
- supplied with oxygenated blood by hepatic artery
- blood removed by hepatic vein
- hepatic portal vein supplies liver with products of digestion from duodenum
- bile duct takes bile to the gall bladder
what is the structure of the liver
- liver lobules known as hepatocytes
- branches of the hepatic artery and hepatic portal vein supply each lobule with blood
- sinusoids are wide capillaries that carry the blood, lined with endothelial tissues
- each lobule connected to a branch of the hepatic vein that drains blood away from the lobule
how does the liver store glycogen
- converts glucose into glycogen (glycogenesis) which helps to regulate blood glucose concentration
- insulin triggers the process after it detects an increased blood glucose concentration
- removes glucose molecules from the blood stream and decreased blood glucose to a normal range
how can the liver form urea and undergo deamination
- amino group is removed with a hydrogen atom
- combine to form ammonia and ammonium ions
- ammonia is highly toxic so is converted to urea
- ornithine cycle - 1 urea molecule is produced from 1 CO2 molecule and 2 amino groups
- urea diffuses through the phospholipid bilayer of the membranes of the hepatocytes and transported to the kidneys
what is detoxification
- breakdown of substances that are not needed or are toxic
- lactate
- alcohol
- hormones
what are the kidneys
Osmoregulatory organ
- regulate water content of the blood- maintain blood pressure
Excretory organ
- excrete toxic waste products of metabolism and excess substances
what is the structure of the kidney
Renal artery - carries oxygenated blood to kidneys
Renal vein - carries deoxygenated blood away from the kidneys
Ureter - carries urine from the kidneys to the bladder
Bladder - stores urine temporarily
Urethra - releases urine outside of the body
what is the fibrous capsule
- surrounds the kidney
Cortex - glomerulus, bowman’s capsule, proximal convoluted tube, distal convoluted tube
Medulla - loop of henele, collecting duct
Renal pelvis - ureter joins kidney
what is a nephron
where urine is formed
how are the network of blood vessels arranged in the nephron
- glomerulus within bowman’s capsule
- glomerulus supplies by afferent arterioles
- capillaries of glomerulus re-join to efferent arteriole
- blood flows from the efferent arteriole into a capillary network
- blood from capillaries flows into the renal vein
what is the process of ultrafiltration
- blood from the renal artery enters arterioles in the cortex
- arteriole splits into glomerulus - bowmans
- afferent wider in diameter than efferent causing high blood pressure
- high BP causes small molecules being carried into the blood to be forced out of the capillaries of the glomerulus into bowman’s capsule to form filtrate
- blood in glomerulus is separated from the lumen of the Bowman’s by : endothelium of capillary, basement membrane, epithelium of Bowman’s capsule
- blood passes through glomerular, gaps in podocytes and holes in endothelial cells allows dissolved substances into Bowman’s
- glomerular filtrate in Bowman’s
- red/ white blood cells, plasma remain in blood
what factors affect water potential in glomerulus and Bowman’s capsule
Pressure
- afferent wider creating high BP
- raises WP of blood plasma in glomerular above WP in capsule
- water moves down WP from blood plasma in glomerular to capsule
Solute concentration
- plasma proteins stay in the blood
- solute concentration higher in blood plasma than capsule
- water moves down WP from capsule to glomerular
what is the process of selective reabsorption
- filtrate flows along PCT through loop of henle along DCT
- useful substances leave nephron tubules and enter capillary network
- epithelium of PCT wall had microvilli to give large surface area for reabsorption
- glucose, AA, vitamins, salts reabsorbed along PCT by active transport + facilitated diffusion
- water enters blood by osmosis as WP of blood is lower than filtrate
- water reabsorbed from loop of Henle, DCT and collecting duct
what is the counter current mechanism
- top of ascending limb Na and Cl pumped out of the medulla
- ascending limb is impermeable to water
- low WP in medulla due to high ion conc.
- water moves out of descending limb into medulla via osmosis
- filtrate more concentrated
-water in medulla reabsorbed into blood - bottom of ascending limb Na and Cl ions diffuse out of the medulla and lowers WP
What is osmoregulation
- WP is measured and monitored by osmoreceptors in hypothalamus
- osmoreceptors are stimulated by low WP the posterior pituitary gland releases ADH
- ADH makes walls of DCT and collecting duct more permeable to water
how do blood ADH levels rise when dehydrated
- water content drops so does WP
- detected by osmoreceptors
- more ADH is released
- more water reabsorbed into the blood via osmosis
- small amount of highly concentrated urine produced
how do blood ADH levels fall when hydrated
- water content rises so does WP
- detected by osmoreceptors
- less ADH reduced
- less water reabsorbed into blood via osmosis
- large amount of dilute urine produced
why is kidney failure bad
- urea, salts, toxins are retained and not excreted
- less blood is filtered by the glomerulus
- build up of toxins in the blood
what can a kidney infection cause
- podocytes and tubules may be damaged
- blood in urine
- glucose in urine = diabetes
what is haemodialysis
- patients blood flows through a dialysis machine
- blood flows on one side of a partially permeable membrane and dialysis on the other side
- waste products, excess water, ions diffuse across the membrane into dialysis fluid removing them
- blood cells, proteins are prevented from leaving
- done by trained health professions, emotional support
- causes fatigue, low blood pressure, blood clots, blood infections
what is peritoneal dialysis
- dialysis fluid through a tube that passes from the patients abdomen into abdominal cavity
- waste products diffuse out into the fluid across the peritoneum
- carried out at home, done by yourself
- difficult, increased risk of infection
how can urine be used to detect pregnancy
- stick is used with application area containing monoclonal antibodies for hCG bound to a blue bead
- urine applied any hCG binds to antibodies on the beads
- urine moves up the test strip carrying beads
- test strip has immobilised antibodies to hCG
- if hcG is present the test strip turns blue
- no HCG present beads pass through the test area without binding to anything
how can urine be used to test for steroids
- anabolic steroids build up muscle tissue
- urine tested by chromatography / mass spectrometry
- in gas chromatography the urine sample is vaporised through a column containing polymer
- different substances move through at different speeds
- substances in urine separate
- mass spectrometer converts substances into ions and then mass/charge
- results are analysed
how is urine used to test for recreational drugs
- test strips contain antibodies that the drug being tested for will bind to
- sample of urine is applied to test strip
- colour change occurs
- first test shows positive result a sample of urine is sent for further testing
