Excretion (pg2.42-2.53)

Question 1

Metabolism (definition)

Answer 1

The sum total of all the chemical reactions that occur in a cell.

Question 2

Waste products of Metabolism

Answer 2

CO2, excess H2O, salts, and nitrogenous wastes (urea, uric acid and creatinine).

Question 3

Why do waste products need to be removed?

Answer 3

They’ll poison the cells and inhibit their normal functioning if allowed to accumulate.

Question 4

Excretion vs Egestion vs Secretion

Answer 4

Excretion: The removal of metabolic wastes from the body.

Egestion: The removal of undigested substances (substances that were never inside cells or metabolised).

Secretion: The release of useful substances that are produced by cells for important functions.
(E.g digestive juices, hormones, and milk)

Question 5

Describe the path of Excretion in Humans.

Answer 5

Metabolic waste products diffuse out the cells to the blood in the blood vessels via surrounding tissue fluid&raquo_space; Blood transports waste products to several excretory organs which have the ability to remove these waste products from the bloodstream and release them out the body.

Question 6

List the 4 different Excretory Organs

Answer 6

> Lungs
Kidneys and Bladder
Liver and Intestines
Skin

Question 7

Metabolic wastes excreted by: LUNGS

Answer 7

+ CO2
+ Water vapour
+ Heat

Question 8

Metabolic wastes excreted by: KIDNEYS and BLADDER

Answer 8

+ Urine

• excess water
• mineral salts
• nitrogenous waste products (urea, uric acid, and creatinine)

Question 9

Metabolic wastes excreted by: LIVER and INTESTINES

Answer 9

+ Urea (transported in the blood to the kidneys and is excreted in urine)
+ Bile pigments (pass into the small intestine and are excreted as bile salts in the faeces)

Question 10

Metabolic wastes excreted by: SKIN

Answer 10

+ Sweat (via sweat glands)

• excess water
• salts
• small amount of urea

Question 11

Origins of Metabolic Waste Products

Answer 11

> CO2: - cellular respiration.

> Excess water: - cellular respiration.
- intake of fluids and food.

> Urea: - deamination of excess amino acids (in liver).

> Uric acid: - product of metabolism of nucleic acids.

> Creatinine: - creatinine phosphate in the cells.

> Bile pigments: - breakdown of haemoglobin (in liver).

Question 12

Explain the process of the Urinary System (6 points)

Answer 12

1. Kidneys receive OXYGENATED blood that is rich in metabolic waste products (mwp’s), from the RENAL ARTERIES.
2. DEOXYGENATED blood that has been purified of mwp’s is transported away from the kidneys via the RENAL VEINS.
3. A tube known as the URETER extends from each kidney and opens separately into the bladder.
4. The urinal BLADDER is a thin-walled muscular sac in which urine is temporarily STORED.
5. A single tube, the URETHRA, TRANSPORTS the urine from the bladder TO the EXTERIOR.
6. A SPHINCTER MUSCLE, at the base of the bladder, CONTROLS THE FLOW of urine to the urethra.

Question 13

Macroscopic Structure Function:

RENAL CAPSULE

Answer 13

A connective tissue membrane that: 
- Protects kidneys from 
   mechanical injury.
- Insulates the kidneys.
- Keeps the kidneys in position.

Question 14

Macroscopic Structure Function:

CORTEX

Answer 14

The reddish-brown region that:
- Contains lots of blood
capillaries.
- Is the Region of Filtration in the kidney.

Question 15

Macroscopic Structure Function:

MEDULLA

Answer 15

The lighter-coloured, inner region of the kidney that:
- Contains tubes that are arranged
in groups.
- Is a lighter pinkish colour.

Question 16

Macroscopic Structure Function:

RENAL PYRAMID

Answer 16

• A group of many tubes draining waste from the capillaries to the renal pelvis.

Question 17

What is a RENAL PAPILLA

Answer 17

The apex (point) of each renal pyramid that leads to a renal calyx.

Question 18

Macroscopic Structure Function:

RENAL CALYX

Answer 18

- Collects urine from the renal 
   pyramids via tubes in the renal 
   papilla.
- Opens to renal pelvis.
- Plural: Calyces.

Question 19

Macroscopic Structure Function:

RENAL PELVIS

Answer 19

Widened region of the ureter that:

- Collects urine from the calyces.

Question 20

Macroscopic Structure Function:

URETER

Answer 20

-Drains urine to the urinal bladder.