Excretion 5.1.2

Question 1

What is the difference between excretion and egestion?

Answer 1

-Excretion is the removal of metabolic waste whereas egestion is the elimination of faeces from the body

Question 2

What are the four main excretory organs?

Answer 2

Lungs, Liver, Skin and Kidneys

Question 3

How does blood get to and from the liver?

Answer 3

-Oxygenated blood travels to the liver via the aorta and hepatic artery
-Blood removed from the liver to the heart travels along the hepatic vein which joins to the vena cava
-Liver is also supplied by the hepatic portal vein which carries products of digestion from the intestines

Question 4

What are liver cells called and their functions?

Answer 4

-Hepatocytes
-Have large nuclei, prominent Golgi apparatus, many mitochondria (metabolically active cells)

Question 5

Where is Bile produced and what is it used for?

Answer 5

-Liver
-It is released via bile duct into small intestines to emulsify fats

Question 6

What do Kupffer cells do?

Answer 6

-Found in the sinusoids(air spaces surrounded by hepatocytes) in the liver
-Act as macrophages ingesting foreign particles

Question 7

What are the functions of the liver?

Answer 7

-Control blood glucose, amino acid and lipid levels
-Synthesis of bile, plasma proteins and cholesterol
-Storage of vitamins A,D and B12 iron and glycogen
-Detrofication of alcohol and drugs
-Breakdown of hormones and RBC

Question 8

Where does the liver store sugars and how does the liver control levels of glucose?

Answer 8

-The liver stores sugars in the form of glycogen granules in the cytoplasm of the hepatocytes
- Homeostatic control, when blood glucose rises, insulin levels rise, stimulating hepatocytes to convert glucose into glycogen and vice versa when they fall except the hormone is glucagon

Question 9

What enzymes does the liver contain?

Answer 9

-Catalase: converts hydrogen peroxide to oxygen and water
-Cytochrome p450: group of enzymes that breakdown drugs
-Alcohol dehydrogenase: breaks down ethanol into ethanal, ethanal is then converted to ethanoate

Question 10

What is transamination?

Answer 10

-Conversion of one amino acid to another, this process is carried out by hepatocytes

Question 11

Describe the process of the ornithine cycle?

Answer 11

-chain of enzyme controlled reactions
1. Ammonia and carbon dioxide combine with ornithine to produce citrulline and water
2. Citrulline is converted to arginine (with the removal of water)
3. Arginine is the re-converted to ornithine by the addition of water and removal of urea

Question 12

What does the word renal refer to?

Answer 12

-The kidney

Question 13

What are the functions of the kidney?

Answer 13

-Osmoregulation
-Excretion
-Filter urea and other mineral ions out the blood excreting them, therefore they help maintain water and ion balance

Question 14

Draw the gross anatomy of the kidney?

Question 15

Do revision cards

Answer 15

Do revision cards

Question 16

How are hepatocytes adapted?

Answer 16

-Hepatocytes are thin for short diffusion distance
-Fenestrated (tiny openings) to increase permeability

Question 17

How is blood circulated through the kidney?

Answer 17

-Renal arteries carry unfiltered blood to kidneys, the arteries branch off from the abdominal aorta
-Blood that has been circulated through the kidneys goes out through the renal vein which drains into the inferior vena cava

Question 18

How does urine collect in the kidney and how does it get to the bladder?

Answer 18

-Urine collects via the renal pelvis
-The ureter carries urine to the bladder where it is stored

Question 19

What is a Nephron?

Answer 19

-A nephron is a basic structural and functional unit of the kidney

Question 20

Why is the afferent arteriole larger in diameter than the efferent arteriole and what is the glomerulus?

Answer 20

-This helps maintain a higher hydrostatic pressure in the glomerulus than the bowman’s capsule pushing fluid from the blood in
-The glomerulus is a tangle of capillaries within the bowman’s capsule

Question 21

What are the three layers of the bowman’s capsule?

Answer 21

-Capillary endothelium: pores allowing blood plasma and dissolved substances to pass out but not RBCs
-Basement membrane: mesh of collagen fibres and glycoproteins that acts as a filter
-Epithelial cells of Bowmans capsule: makes sure cells platelets and plasma proteins don’t enter tubule

Question 22

What is filtered out of the blood?

Answer 22

-Urea, glucose, Amino acids, water and inorganic mineral ions