Chapter 18 - Excretory system Flashcards
Explain why living organisms need to excrete
- Some waste products can be poisonous and, if not excreted, can slow down metabolism in cells
- Some waste products like salts and water in are in excess, and if not excreted, can damage cells
Name the main excretory organs, along with the waste products excreted by each organ
Lungs: Carbon dioxide and water vapour
Skin: Water, salts, small amounts of urea
Kidneys: Nitrogenous waste products, excess water and excess salts
Name the waste products of metabolism, and explain how they are formed
- Carbon dioxide: Produced during the Krebs cycle in mitochondria
- Bile pigments: Formed in the liver and spleen during the breakdown of haemoglobin. Excreted in faeces
- Urea: Formed in the liver during deamination
- Water vapour: Formed during cellular respiration
- Excess water: Taken in with fluids during nutrition
- Excess salts: Taken in during nutrition
Name the part in the brain responsible for osmoregulation
Hypothalamus
Define excretion
The removal of metabolic waste from the body, along with the removal of excess substances like water and salts from the body
Describe cellular secretion, and give a few examples
Cells produce usefull substances during metabolism and release it to perform important funcitons, like hormones, digestive juices and milk
Where does the carbon dioxide which is used during deamination come from?
Respiration in the liver
Describe the breaking down of alcohol, drugs and hormones in the liver
- Alcohol is broken down into water and carbon dioxide. This process is known as detoxification
- Drugs are broken down by the liver
- Hormones which are continuously produced by endocrine glands are broken down in the liver to prevent accumilation thereof in tissue
Study the sketches of the kidneys and excretory system
Heh?
Describe the functions of the kidneys
- Excretion of nitrogenous waste
- Osmoregulatory function by excreting excess water or reabsorbing water when necessary
- Regulate salt concentrations by excreting salts or reabsorbing water and salts
- Regulation of pH
- Reabsorbtion of usefull substances
Name the cells, their adaptions and function, of which the inner wall of the bowman’s capsule consists
- Podocytes
- Filtration slits
- Ultra-filtration
Why is the blood pressure in the glomerulus so high?
The diameter of the afferent arteriole is much larger than the efferent arteriole
Study the sketch of the nephron
Ehe!
Give another name for “vasa recta”
Peritubular capillaries
Name the three main functions of the nephron
- Ultra-filtration
- Tubular reabsorbtion
- Tubular secretion
Why are small molecules in blood able to filtrate into the bowman’s capsule?
- The walls of glomerulus is made of one epithelial cell layer
- The podocyte layer has filtration slits which form an ultrafine filter
Name the adaptations of the Malpighian body for ultra-filtration
- Very high blood pressure in glomerulus
- Capillary network of glomerulus provides a large surface area
- Bowman’s capsule is cup-shaped to give it a large surface area
- Thin walls of bowman’s capsule and walls of glomerulus
- Podocytes have filtration slits
- Capillaries of glomerulus are in close contact with the bownman’s capsule
Describe tubular reabsorbtion of usefull substances in the proximal convoluted tubule
- Usefull substances like glucose and amino acids which pass into filtrate must now be reabsorbed
- Selective reabsorbtion of substances like ALL glucose, amino acids etc. are absorbed by active transport
- Usefull minerals such as sodium ions are absorbed by active transport and facilitated diffusion
Name the adaptations of the proximal convoluted tubule for tubular reabsorbtion
- Micro villi to maximise absorbtion area
- Endothelial cells contain many mitochondria to release energy for active transport
- Endothelial layer is a single layer for easy passage of substances
Describe tubular reabsorbtion of water in the loop of Henle
- Filtrate enters the loop of Henle where water is conserved
- There is always a high Na and Cl concentration outside the loop
- The higher the NaCl concentration outside the loop, the more water will be reabsorbed by osmosis
- The descending limb is permeable to water and water is absorbed into vasa recta by osmosis
- Sodium ions are actively pumped out of the ascending limb, and chlorine follows passively
- Water will not follow because the ascending limb is inpermeable to water
- The longer the loop of Henle, the more water can be absorbed
Describe tubular reabsorbtion of usefull substances in the distal convoluted tubule
- Further absorbtion of usefull substances occurs here
- Regulates pH of blood
- When blood is acidic, H+ ions is secreted into the blood
- When blood is alkaline, less H+ ions are secreted and bicarbonate ions are secreted from the blood into the tubules
Describe osmoregulation in terms of hormones released
- Water content too low: Posterior pituitary gland secretes ADH, which causes the walls of the collecting duct to become more permeable so more water can be absorbed
- Vica versa for too high water content
Describe tubular secretion
- Substances are secreted from blood in vasa recta into proximal and distal convoluted tubules
Name the main constituents of urine
- Water
- Metabolic waste
- Inorganic salts
- Foreign substances
- Drugs
Suggest reasons for kidney failure
- Infections of kidneys
- Accidents
- Hypertension
- Diabetes mellitus
- Heart failure
- Cysts
Explain dialysis
- Blood enters from patient’s artery in arm
- Blood pumped
- Blood passes through dialysis tubing
- Tubing is partially permeable and filters blood
- Tubing surrounded by dialysis fluid
- Fluid contains glucose and amino acids, and some salts, BUT NO urea or uric acid
- Dialysis fluid has same osmotic potential as blood
- Waste substances and excess substances diffuses into dialysis fluid
- Bubble trap removes air bubbles and warms blood
- “Clean” blood enters through a vein in patient’s arm
Name the advantages of kidney transplants
- Normal life
- Independent of machines
- Continuous filtration
Name the disadvantages and risks of kidney transplants
- Rejection of transplanted kidneys could occur
- Immunosuppressant drugs need to be taken (may even be lifelong)
- Isolation
- Operation is risky
- Very expensive
- The tissue type and blood group of donor must closely match
Name the advantages of dialysis
- No donor
- Rejection impossible
- A life saver if transplant is not immediately possible
Name the disadvantages of dialysis
- Time consuming
- No normal life
- Must live close to hospital
- There may be a shortage of machines
- Expensive
- No continuous filtration
- Loss of some minerals like calcium and iron
- No sport :(
