Excretory System

Question 1

Types of metabolic waste produced by living systems

Answer 1

○ Digestive waste
○ Respiratory waste
○ Excess water and salt waste
○ Nitrogenous waste

Question 2

Excretion

Answer 2

○ The removal of wastes produced by metabolism within cells
○ The main organs of excretion are
□ Lungs
- Carbon dioxide and water
□ Sweat glands
- Water, salt, and urea
□ Alimentary canal
- Water and bile pigments
□ Kidneys
- Water, salt, and urea

Question 3

Elimination

Answer 3

• The removal of undigested materials from the body
• The bulk of feces is elimination (except for bile pigments)

Question 4

Functions of the organs

Answer 4

○ Kidneys
- Filter blood to remove wastes and produces urine
○ Ureters
- Transports urine from the kidney to the bladder
○ Bladder
- Temporary storage of urine and contracts to ‘squeeze’ urine out of the body
○ Urethra
- Transports urine from the bladder to outside the body

Question 5

Basic kidney structure

Answer 5

• Capsule (outside)
  □ Clear
  □ Smooth/skin like
• Cortex (outer)
  □ Where the filtration occurs
  □ Light reddish brown
  □ Granular
• Medulla (middle)
  □ Where useful substances are reabsorbed
  □ Dark brown/red
  □ Striated
• Pelvis (inside)
  □ Where the urine collects before traveling down the bladder
  □ Centre
  □ White/yellow
  □ Smooth

Question 6

Microscopic structure of the kidney

Answer 6

○ The structural and functional unit of the kidney is the nephron
○ There are approximately 1 million per kidney

Question 7

Three basic parts of the nephron

Answer 7

□ Glomerulus
□ Kidney - cortex
□ Tubules
□ Kidney - medulla
□ Collecting duct
□ Kidney - pelvis

Question 8

Formation of urine in the nephron

Answer 8

Three major stages - glomerular filtration, reabsorption, and tubular secretion

Question 9

Glomerular filtration

Answer 9

□ Blood enters the glomerulus via the afferent arteriole and is connected to a knot of capillaries called the glomerulus.
□ The glomerulus is surrounded by the glomerular capsule
□ Some of the liquid parts of blood is forced into the glomerular capsule - the red and white blood cells and plasma proteins are left behind and leave via the efferent arteriole
□ The liquid in the glomerular capsule is now called filtrate

Question 10

Reabsorption

Answer 10

□ The filtrate passes into the proximal convoluted tubule – many useful substances are reabsorbed into the peritubular capillaries
□ The filtrate then passes through the Loop of Henle and the distal convoluted tubule where further reabsorption of useful substances occurs
□ The Loop of Henle is particularly important for water reabsorption
- E.g. water, glucose, salts

Question 11

Tubular secretion

Answer 11

□ Tubular secretion adds substances to the filtrate
□ The food you eat is slightly acidic, but blood needs to have a pH of 7.4-7.5
□ Hydrogen and ammonium ions are added to the filtrate so that blood pH remains stable (the body will lose these ions via the urine, and so the pH of the blood will rise)
□ Other materials such as potassium and some drugs are also removed from the body this way
□ The fluid is now called urine and passes into the collecting duct and to the ureter