Excretory system

Question 1

Why is excretory system needed?

Answer 1

Excretion is the removal of the wastes of metabolism from the body. If not removed, wastes would accumulate and most are toxic to the body

Question 2

What are the two main organs of excretion?

Answer 2

Liver
Kidneys

Question 3

Define deamination

Answer 3

The removal of the amino group from the amino acids that make up proteins

Question 4

What is the function of skin in excretion?

Answer 4

The skin is involved in excretion through sweat glands which excrete salt, lactic acid, urea and some drugs through sweat

Question 5

What happens if all glycogen and fat stores are used up as energy?

Answer 5

The body is able to use large amounts of proteins to supply energy to the body. This requires a series of steps:
-Deamination 1
-Deamination 2

Question 6

What is the equation for deamination 1?

Answer 6

Amino Acid + Oxygen –>(with the presence of enzymes) Carbohydrates + ammonia

Question 7

What is the equation for deamination 2?

Answer 7

energy + CO2 + Ammonia –> urea + water

Question 8

Where does deamination occur

Answer 8

Deamination occurs in the liver

Question 9

What are the products of deamination 1 and 2?

Answer 9

Products of 1 are carbohydrates
Products of 2 are water and urea

Question 10

Why does deamination 2 occur?

Answer 10

Because the ammonia (NH3) is highly toxic to cells and needs to be converted to the less toxic urea by the liver.

Question 11

What happens to the products of deamination and how are they excreted by the body?

Answer 11

• Carbohydrates are readily broken down by the cells to release energy, carbon dioxide and water
• Urea is easily excreted by the kidneys and is eliminated from the body in the urine, Small amounts of urea are also lost in sweat from the sweat glands
• Water is utilised in cell processes

Question 12

What is the passage of urine through macroscopic kidney?

Answer 12

Renal pelvis -> ureter -> urinary bladder -> urethra

Question 13

What is structure of kidneys?

Answer 13

• The kidneys appear bean shape with a concave surface through which the renal arteries enter the kidneys with oxygenated blood and the renal veins leave the kidney with the deoxygenated blood
• The ureter leaves the kidney with the waste products of the blood and drains the urine formed into the urinary bladder which connects to the urethra

Question 14

What is the function of the kidneys in excretion?

Answer 14

• To get rid the body of wastes, especially nitrogenous wastes such as urea
• To regulate the balance of fluid, salt and pH

Question 15

what holds the kidneys in position?

Answer 15

they are embedded in renal fat

Question 16

What is the kidney composed of?

Answer 16

A large number of structures called nephrons and collecting ducts. Nephrons are the functional unit of the kidney. A nephron consists of a renal corpuscle and a renal tubule. Each kidney contains approx 1 million nephrons

Question 17

What are the three steps in production of urine?

Answer 17

Glomerular Filtration
Selective reabsorption
Secretion

Question 18

Ways Glomerular Filtration is enhanced

Answer 18

The filtration is enhanced in 3 ways:
- The renal artery is connected directly to the aorta and blood is under constant high pressure
- The glomerulus is highly coiled (large surface area) so more filtration will take place
- The afferent arteriole is wider than the efferent arteriole leaving the glomerulus. This provides greater pressure. The high pressure forces water and dissolved blood components to enter the Glomerular capsule

• The resulting fluid is called the filtrate
• The filtrate consists of all material in the blood except red and white blood cells and plasma proteins. so consists of water, amino acids, urea etc.

Question 19

Selective reabsorption

Answer 19

Material that are reabsorbed from the tubules include:
- water, glucose, amino acids, ions

This reabsorption occurs along the entire tubule, but is greatest in the proximal convoluted tubule and Loop of Henle.

For efficient reabsorption a large surface area is required. This is achieved due to the:
-long length of the kidney tubule
-large number of nephrons

Active process

Question 20

Tubular secretion

Answer 20

• Tubular secretion adds materials to the filtrate from the blood e.g. Potassium, Hydrogen ions
• It removes unwanted materials from the blood to control its pH
• occurs mainly at the distal convoluted tubule
• The water and other substance that are not reabsorbed drain into the collecting tubules then into the renal pelvis, to the ureter

Question 21

What is the importance of the liver in the excretory system?

Answer 21

-Prepares wastes for removal from the body e.g.
converts the toxic ammonia to urea
-Produces bile, which aids in digestion and
absorption

Question 22

What is the importance of the lungs in the excretory system?

Answer 22

• Carbon dioxide and water diffuse across the respiratory membranes
  -Excreted as gases when we exhale

Question 23

3 main functions of nephrons

Answer 23

Filtration, reabsorbtion, secretion

Question 24

How is blood supplied to nephrons?

Answer 24

• The renal artery supplies oxygenated blood to the kidneys. The renal artery then branches into the many small arteries and arterioles
• The afferent arteriole supplies each nephron, forming a knot of capillaries called the glomerulus which sits in the glomerular capsule of the nephron. The capillaries then rejoin to form the efferent arteriole which leaves the glomerular capsule
• The efferent arteriole is much smaller in diameter that the afferent arteriole which enters the nephron. The efferent arteriole then divides to form a second network of capillaries which surround the proximal convoluted tubule, Loop of Henle, distal convoluted tubule and collecting duct. This capillary network will then rejoin to form the renal vein which carries the blood back to the heart via the inferior vena cava

Question 25

What is in the renal corpuscle

Answer 25

The renal corpuscle includes a glomerulus and glomerular capsule. The glomerulus is a cluster of capillaries, where filtration of blood takes place. Glomerular capsule surrounds the glomerulus and collects the filtrate.

Question 26

What occurs and what is in the renal tubules

Answer 26

From the Glomerular capsule, the filtrate enters the renal tubules, which consist of the proximal convoluted tubule, loop of Henle, and distal convoluted tubule. These tubules are responsible for reabsorbing essential substances, such as water, glucose, and electrolytes, back into the bloodstream, while also secreting waste products, drugs, and excess ions into the tubular fluid.

Question 27

Urine composition

Answer 27

96% water
2% urea
1.5% ions
0.5% other