Excretory System Flashcards
What does homeostasis mean?
- The maintenance of constant internal environment
What is the functions of the excretory system?
- Filtering blood
- Regulating body fluids
- Removing nitrogenous waste
- Maintaining homeostasis
What is the functions of the kidney?
- Formation of urine
- Production of renin (enzyme)
- Conversion of vitamin D to its active form
- Production of erythropoietin
What is a nephron?
- Within the kidney there are filtering units called nephrons
What are the functions of nephrons?
- Nephrons are supplied with blood by the renal artery, they filter blood to produce urine
- Nephrons ensure waste is excreted, whilst some substances are reabsorbed back into the blood
What are the processes in the nephron?
- Ultrafiltration (removing substances from the blood)
- Selective reabsorption (reabsorbing the substance the body needs)
- Urine formation (substances which are not reabsorbed travel as urine along the nephron to the collection ducts where waste goes to the bladder
What is osmoregulation?
- The balancing of the salt and water concentration in the body
What is the importance of osmoregulation?
- Keeps the cells working
- The concentrations of solutes surrounding cells become too high (hypertonic)➡️cells shrivel
- The concentrations of solutes surrounding cells become too low (hypotonic) ➡️take too much water and burst
What is the mechanism of osmoregulation?
- Physiology process to maintain water balance
- Uses osmoreceptors and endocrine system
- Hypothalamus detects a change in water content via osmoreceptors, initiates response
What happens when there is a high water content?
1.Body=hydrate
2. Osmoreceptors send response to pituitary gland
3. ADH (anti-diuretic hormone) is decreased
4. Less water is absorbed by kidneys
5. More urine produced to lose water
What happens when there is a low water content?
- Body=dehydrated
- Osmoreceptors send response to pituitary gland
- ADH (anti-diuretic hormone) is increased=more water reabsorbed by kidney via osmosis
- Less urine produced
Compare the removal of nitrogenous waste in birds and mammals
- Mammals - produce urine, excrete urine and faeces separately , remove ammonia as urea
- Birds- produce solid waste, urine and faeces are combined, remove ammonia as uric acid
State the hormone involved in osmoregulation
- ADH (antidiuretic hormone)
Describe two roles of the loop of henle
- Conducts urine along a u-shaped portion of the tubule in a nephron
- Reabsorbs water - prevents dehydration- in the descending limb
- Reabsorbs ions into the bloodstream
Explain two functions of the excretory system
- Filtering blood- to remove toxic waste products
- Maintaining homeostasis- by maintaining salt and water levels
- Removing nitrogenous waste - formation of urine
State where urine is stored before being removed from the body in mammals
- Bladder
State the three layers of the kidney
- Renal capsule
- Renal cortex
- Renal medulla /renal pelvis
Describe the three processes that occur in a nephron
- Ultrafiltration- substances are removed from the blood
- Selective reabsorption- substances that the body needs are reabsorbed
- Urine formation- substances that are not reabsorbed are removed as urine, urine is formed along the nephron and is taken to the bladder via collecting duct
Where does ultrafiltration occur?
- Bowman’s capsule
Where does water reabsorption occur?
- Loop of Henle - distal convoluted tubule
Where does salt reabsorption occur?
- Loop of Henle - proximal convoluted tubule
Explain what occurs in the ascending limb of the loop of Henle
- Permeable to water
- Water leaves the nephron via osmosis and is reabsorbed into the bloodstream as much as the body needs is reabsorbed
Explain what occurs in the descending limb of the loop of Henle
- Permeable to ions
- Sodium and chlorine ions diffuse out due to high concentration of water outside the nephron
- The concentration of salt decreases further up the ascending limb
- Sodium and potassium are actively pumped out towards the top of the loop of the limb
Explain what happens in the distal convoluted tubule?
- The final reabsorption of ions and water occurs ADH controls water reabsorption
Name the gland that produces ADH
- Pituitary gland
Explain the effect of dehydration of the kidney
- Water content in the blood drops
- Drop is detected by osmoreceptors in the hypothalamus
- The pituitary gland releases more ADH into the bloodstream
- ADH increases the permeability of the collecting duct
- More water is absorbed via osmosis from the collecting duct into the bloodstream
- Less water lost in urine
Discuss the role of the nephron
- U-shaped portion of the tubule that conducts urine within each nephron of the kidney of reptiles, mammals and birds
- The principal function of the nephron is the recovery of water and sodium chloride from the urine and removal of urea from the blood
- This function allows production of urine that is more concentrated than blood
- Limits the amount of water needed as intake for survival
- Many species that live in arid environments such as deserts have highly efficient loops of Henle
- Adaptations in species in other extreme environments allow them to survive
- Sodium potassium pumps allow reabsorption of water
Discuss the role of the loop of Henle in a camel living in the desert
- U-shaped portion of the tubule that conducts urine
- Recovery of water and sodium chlorine from the urine
- Allows the production of urine that is more concentrated than blood
- Reduces the amount of water needed for survival - highly efficient loops of Henle in environments such as deserts
- Adaptations in species in extreme environments to help them survive
What is the role of the loop of Henle in a camel living in a desert
- The function of the nephron is the removal of urea from the blood
- This function allows the production of urine that is more concentrated than blood
- Limits the amount of water intake for needed for survival
- Many species that live in deserts have highly efficient loops of Henle
- Adaptations in species in other extreme environments allow them to survive
What is hyperglycaemia?
- Too much blood glucose
What is hypoglycemia?
- Too little blood glucose
What cells in the pancreas release glucagon?
- Alpha cells
What cells in the pancreas release insulin?
- Beta cells
What is the definition of filtrate and permable?
Filtrate=water and ions
Permable= allows/lets in
