Liver and Excretion Flashcards
(26 cards)
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
