Excretion Flashcards
What is Excretion ?
-Excretion is the removal of metabolic waste products from the body.
Examples of Excretion
- Removing c02 - respiration
- Bile pigment- breakdown of haemoglobin
- Nitrogenous waste - amino acids
What are the main parts of the liver and their functions ?
- Hepatic artery - delivers oxygenated blood to the liver,
- Hepatic vein – takes deoxygenated blood away from the liver
- Hepatic portal vein – connects the liver to the intestines. This allows harmful substances that have been removed from the liver to be immediately broken down.
- Bile duct – takes bile from the liver to the gall bladder, where it is stored.
What is the structure of the liver ?
-The liver is made up of liver lobules, which are cylindrical structures made up of hepatocytes (liver cells) that radiate out from the central vein.
- The central vein connects to the hepatic artery and hepatic portal vein via special capillaries called sinusoids. The central vein also connects to the bile duct via tubes called canaliculi.
What are the three main functions of the liver
- Storage of glycogen
- Detoxification
- Formation of urea
Describe the storage of glycogen
the liver converts excess glucose into glycogen
Describe Detoxification
alcohol, drugs and hormones in the blood are also broken down by the liver and their products are excreted from the body in the urine.
Describe the formation of urea
- Deamination - removing the amino group off the excess amino acids and the rest is respired or converted to glycogen or lipids for storage.
What is osmoregulation?
- Maintaining the water balance and PH of the blood
Movement of blood in kidney
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Draw and label kidney diagram
What is the nephron and what does it do ?
-The kidney has millions of nephrons in it, these are filtering units
-Nitrogenous waste is removed
-Water and mineral ions are balanced
- Substances are selectively reabsorbed e.g. glucose
Where does everything happen in the kidney?
- Cortex- where the filtering of the blood takes place, contains a very dense capillary network carrying the blood from the renal artery to the nephrons
-Medulla- contains tubules of the nephron that form pyramids of the kidney and the collecting ducts
-Pelvis- where the urine collects before passing down the ureter
Draw a labelled Nephron
DID YOU GET IT RIGHT PUS
Where is the nephron located in the kidney ?
The majority of the nephron is in the cortex, the loop of Henle drops into the medulla and the collecting duct passes urine into the pelvis
What is Ultrafiltration ?
- Glomerulus receives blood through a wider afferent arteriole
Blood is put under pressure as it travels through the glomerulus
The pressurised blood is pushed out of the walls of the capillary and through 3 layers
Anything smaller enough will pass into the bowman’s capsule (e.g. glucose, urea, water, ions)
Blood exits the glomerulus through the narrower efferent arteriole
Glomerular filtration rate is the volume of blood that is filtered through the kidney in a given time
What is selective reabsorption ?
In the PCT all of the glucose, amino acids, vitamins, hormones move back into the blood via active transport
85% of the water and sodium chloride are reabsorbed as well
Sodium ions are moved via active transport
Water and chloride ions follow passively down their concentration gradient
More about selective absorption
- In the proximal convoluted tubule (PCT), loop of Henle and the distal convoluted tubule (DCT), useful substances are reabsorbed, passing out of the nephron and back into the capillaries. Glucose is reabsorbed in the PCT by active transport and facilitated diffusion. The PCT epithelium has microvilli to provide a large surface area for reabsorption. Water is reabsorbed in the loop of Henle, DCT and collecting duct by osmosis. The remaining filtrate is urine, containing excess water, excess salts and urea. This passes from the collecting duct to the bladder via the ureter. Urine may contain additional substances like hormones, excess vitamins, the breakdown products of medications and recreational drugs.
