Ch 13 - (Excretion in Humans)

Question 1

What do the lungs excrete?

Answer 1

Carbon dioxide

Question 2

What do the kidneys excrete?

Answer 2

Excess water, salts, and urea

Question 3

Define excretion

Answer 3

The removal of toxic waste substances of metabolic reactions (chemical reactions that take place in the cells), toxic materials and substances in excess of requirements.

Question 4

Why should CO2 be excreted?

Answer 4

• dissolves easily in water to form acidic solution.
• lowers down the pH of cells
• reduces the activity of enzymes
• It is toxic

Question 5

Describe the structure of the kidney.

Answer 5

Two bean - shaped organs that filter the blood.

Question 6

Describe the structure of the ureter.

Answer 6

Tube connecting to the kidney to the bladder

Question 7

Describe the structure of the bladder.

Answer 7

Organ that stores urine (excess water, salts, urea) as it is produced by the kidney

Question 8

Describe the structure of the urethra.

Answer 8

the tube that connects the bladder to the exterior, where urine is released.

Question 9

Where are the kidneys located?

Answer 9

In the back of the abdomen.

Question 10

What are the two functions of the kidneys?

Answer 10

• They regulate water content of the blood (vital for maintaining blood pressure)
• They excrete the toxic waste products of metabolism (urea) and substances in excess of requirements.

Question 11

What are the million tiny structures around the kidney?

Answer 11

Nephrons (kidney tubules or renal tubules)

Question 12

Where does the nephron start?

Answer 12

Cortex of the kidney, loops down into medulla and back up to cortex.

Question 13

What is the First process that happens in the glomerulus?

Answer 13

Ultrafiltration.

Question 14

What is glomerulus?

Answer 14

Knot of capillaries

Question 15

Describe the ultrafiltration process.

Answer 15

• capillaries get narrower as they get into glomerulus.
• increases the pressure of the blood (which is already since it’s connected to renal artery)
• Forces small molecules out of the capillaries into the Bowman’s capsule, where it forms filtrate.

Question 16

What are the substances forced out of capillaries?

Answer 16

Glucose, water, urea, salts. (Some is reabsorbed into the blood)

Question 17

Where is water absorbed at?

Answer 17

loop henle and collecting duct

Question 18

Where is salt reabsorbed at?

Answer 18

loop of Henle

Question 19

Where is glucose reabsorbed at?

Answer 19

proximal (first) convoluted

Question 20

Where is urea reabsorbed at?

Answer 20

Not reabsorbed

Question 21

What is the second process that takes place in the nephrons?

Answer 21

Selective Reabsorption

Question 22

Describe the process of selective reabsorption of glucose in nephrons

Answer 22

• Glucose is reabsorbed in the proximal (first) convoluted tubule
• Takes place by active transport
• Nephron has many mitochondria to provide energy for active transport of glucose molecules

Question 23

Why can the reabsorption of glucose not take place anywhere else in the nephrons?

Answer 23

The gates that facilitate the active transport are only found in the proximal convoluted tubule.

Question 24

Describe the selective reabsorption of water and salts.

Answer 24

• Filtrate drips through loop of henle, necessary salts are reabsorbed back into blood by diffusion and active transport.
• as salts are reabsorbed, water follows by osmosis.
• Water is reabsorbed in the collecting duct in diff amounts

Question 25

Why does the doctor take a urine test for diabetic patients?

Answer 25

• cannot control their blood glucose level, they are too high.
• Not all glucose filtered can be reabsorbed into blood.
• it continues in the filtrate and ends up in the urine.

Question 26

What happens to the digested food molecules absorbed into the blood of the small intestines?

Answer 26

• Carried to the liver for assimilation (when food molecules are converted to other molecules that the body needs)
• Includes amino acids, used to build protein such as fibrinogen (a protein found in blood plasma that is important in blood clotting)

Question 27

What happens to excess amino acids absorbed in the blood that are not needed to make proteins?

Answer 27

• cannot be stored, so they are broken up by deamination.

Question 28

Define the process of deamination.

Answer 28

Removal of the nitrogen - containing part (amine group) of amino acids to form urea.

Question 29

Describe the process of deamination.

Answer 29

• Enzymes in liver split up the amino acid molecules
• Part of the molecule which contains carbon is turned into glycogen and stored
• The part that contains nitrogen, is turned into ammonia, which is highly toxic. Which is later converted to urea.

Question 31

What happens after deamination.

Answer 31

Urea dissolves in the blood and is taken to the kidneys to be excreted.

Small amount is excreted by sweat

Question 32

What are the consequences of High urea kevels?

Answer 32

• cell death
• reduces response to insulin, leading to diabetes
• deposits inside blood vessels.

Question 33

Define egestion

Answer 33

Expulsion of undigested food the waste.