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
