Unit 13 - Excretion in humans

Question 1

Excretion

Answer 1

Removal of toxic materials (products of metabolism) and substances in excess of requirements from organisms. All living organisms can carry out excretion.

The kidneys and liver are responsible for removing toxins from the body, while the lungs remove waste carbon dioxide.

Question 2

Egestion

Answer 2

Involves removing substances that have not become part of the body - they are passing through.

Question 3

Carbon Dioxide

Answer 3

One of the products of aerobic respiration. Excreted through the lungs after being transported there, dissolved in the blood plasma.

Question 4

The urinary system

Answer 4

Organ system responsible for excreting waste and excess substances.

Question 5

Urine

Answer 5

Kidneys excrete urea, excess water and ions as urine. This mixture passes from the kidneys, through the ureters, and to the bladder where it is stored temporarily. When the bladder becomes full, the urethra carries the urine from the bladder to outside of the body.

Question 6

Kidney

Answer 6

Filters waste products out of the blood to form urine. The kidneys remove most of the excess water from the body.

Question 7

Ureter

Answer 7

Structure in the urianry system that carries urine from kidneys to the bladder.

Question 8

Urethra

Answer 8

Carries urine to outside of the body.

Question 9

Bladder

Answer 9

Temporarily stores urine

Question 10

The Liver

Answer 10

Many functions in the body, including:
- assisting the body in taking up amino acids for cellular use
- breaking down excess amino acids.

Question 11

Uptake of Amino Acids

Answer 11

Assimilation is the movement of digested food molecules into the cells of the body to be used.

The liver has a role in the assimilation of amino acids.
- Converts them into proteins, including fibrinogen and other plasma proteins.

Question 12

Excess Amino Acids

Answer 12

Once in the body cells, amino acids can be used to create the new proteins that the cell requires. Excess amino acids are converted into urea in the liver - is called deamination.
- involves the removal of the nitrogen-containing (–NH 2 group) part of amino acid molecules.

The –NH 2 group is converted to ammonia, NH 3 , after it is removed.

Question 13

Structure of the Kidney

Answer 13

The renal artery carries blood to the kidney, and the renal vein carries blood away from it.

Question 14

Cortex

Answer 14

Outer part where blood is filtered and some selective reabsorption happens. (Selective reabsorption - 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 where some selective reabsorption happens, and fluid is collected to form urine.

Question 16

Structure of the nephron

Answer 16

The main functional unit of the kidney, consisting of a glomerulus and a tubule. Its role is to filter the blood, separating waste and returning substances that are needed back to the bloodstream.

Question 17

Glomerulus

Answer 17

Network of capillaries in the kidney nephron where filtration of the blood occurs (the blood is filtered here under pressure (called ultrafiltration)). Water, glucose, urea and ions leave the capillaries and enter the tubule. Protein molecules are too large to leave the capillaries and so they stay in the blood.

Question 18

The tubule

Answer 18

Part of a kidney nephron in which selective reabsorption of substances occurs:
- all of the glucose
- most of the water
- some ions

Urea is not reabsorbed but instead remains dissolved in the liquid inside the tubule. This liquid forms the urine.