13. Excretion in humans

Question 1

Urinary system

Answer 1

Organ system involved in excretion of urea, and excess salts and water. It includes the kidneys, ureters and urethra.

Question 2

Urea

Answer 2

Waste product from the breakdown of excess amino acids, coverted in the liver and excreted in urine.

Question 3

Urine

Answer 3

Waste product of urea and excess ions dissolved in excess water secreted by kidneys.

Question 4

Ureter

Answer 4

Tube that transports urine from the kidneys to the bladder.

Question 5

Bladder

Answer 5

Organ that stores urine until it is released from the body.

Question 6

Urethra

Answer 6

A tube that allows the passage of urine from the bladder and out of the body.

Question 7

Examples of excretion in body

Answer 7

• Carbon dioxide is waste product of aerobic respiration –> excreted through the lungs after being transported there, dissolved in the blood plasma
• Urea being converted into urine int he kidnyes, along with excess water and salts and then removed fromt he body.

Question 8

The liver - Assisting the body in taking up amino acids for cellular use

Answer 8

Liver helps the assimilation of amino acids as it can convert amino acids into proteins (eg. fibrinogen)

Question 9

Liver - Breaking down excess amino acids

Answer 9

Protein is broken down in stomach + small intestines to form amino acids –> absorbed via microvilli into the blood

In body cells amino acids are converted into new porteins needed

Excess amino acids are converted into urea in the liver. (This is called deamination)

This involves the removal of the nitrogen-containing (-NH2 group) part of amino acid molecules. (This gets converted into ammonia which is toxic to cells so thus the ammonia gets converted into urea which isn’t toxic)

The other part gets turned into glucose.

Question 10

Liver - Functions

Answer 10

• Assisting the body in taking up amino acids for cellular use
• Breaking down excess amino acids.

Question 11

Excretion

Answer 11

The removal of the waste products of metabolism, toxic materials and substances in excess of requirements from the body.

Question 12

Renal artery/vein

Answer 12

Carries blood to (artery) and from (vein) the kidney.

Question 13

Cortex

Answer 13

Outer part where blood is filtered and some selective reabsorption happens

Question 14

Selective reabsorption (kidney)

Answer 14

The process in the kidney where the nephron reabsorbs only the molecules the body needs back into the bloodstream.

Question 15

Medulla

Answer 15

Inner part of the kidney where some selective reabsorption happens, and fluid is collected to form urine

Question 16

Nephron

Answer 16

The functional unit of the kidney, consisting of a glomerulus and a tubule.

It’s role is to filter the blood, separating waste and returning needed substances back to the bloodstream.

Question 17

Glomerulus

Answer 17

Network of capillaries found in the Bowman’s capsule.

Blood is filtered here under high pressure causing ultrafiltration.

Question 18

Ultrafiltration - Kidney

Answer 18

Water, glucose, urea and ions leave the capillaries in the glomerulus and enter the tubule (proteins stay in the blood bc they’re too big)

Occurs bc blood in glomerulus is under high pressure.

Question 19

Tubule

Answer 19

Sybstances entering the tubule are selectively reabsorbed.

All of the glucose is reabsorbed + most of the water + most of the ions.

Urea is not reabsorbed and remains dissolved in the liquid found in the tubule –> liquid forms urine

Tubule begins in cortex and then travels inwards through the medulla.