Chapter 14 - Excretion Flashcards
1
Q
What is excretion?
A
- the removal of waste products of metabolism from the body
2
Q
What are the 3 main waste products?
A
-Carbon dioxide
-Bile pigments
- Urea
3
Q
Bile pigments
A
- formed from the breakdown of haemoglobin from old RBCs in the liver
- excreted in the bile from the liver into the small intestine via the gall bladder and bile duct
4
Q
Urea
A
- formed from the breakdown of excess amino acids by the liver
- all mammals produce urea as their nitrogenous waste
-excreted by the kidneys in the urine
5
Q
Liver
A
- rich blood supply
-02 blood is supplied to the liver via the HEPATIC ARTERY - removed from the liver and returned to the <3 in HEPATIC VEIN
6
Q
Hepatic portal vein
A
- liver is also supplied with blood by the HEPATIC PORTAL VEIN
- carries blood loaded with the products of digestion straight from the intestines to the liver
7
Q
Hepatocytes (liver cells)
A
- large nuclei
- prominent Golgi apparatus
- lots of mitochondria
- divide and replicate in months
- secrete bile from the breakdown of the blood in spaces called canaliculi + from these the bile drains -> bile ductules -> gall bladder
8
Q
Mixture?
A
- blood from the hepatic artery + hepatic portal vein is mixed in spaces called sinusoids, which are surrounded by hepatocytes
- mixing increases the 02 content of the blood from the hepatic portal vein
9
Q
Sinusoids
A
- contain Kupffer cells, which act as the resident macrophages of the liver, ingesting foreign particles + helping to protect against diseases
10
Q
Carbohydrate metabolism
A
- hepatocytes are involved in the homeostatic control of glucose levels in the blood by interaction with insulin and glucagon
- blood glucose levels ↑, insulin levels ↑ and stimulate hepatocytes to convert glucose to carbohydrate glycogen
11
Q
Deamination of excess amino acids
A
- removal of an amine group from a molecule
- body cannot store either proteins or amino acids
- deaminate amino acids, remove the amino group + converting it to ammonia which is toxic, to urea
- urea is toxic in ↑ conc but not in blood conc
-remainder of amino acids can be converted into lipids for storage or cellular respiration - ammonia produced is converted to urea in the ornithine cycle
12
Q
Detoxification
A
- breakdown of hydrogen peroxide (by-product of various metabolic pathways)
- hepatocytes contain catalase, one of the most active enzymes, that splits the hydrogen peroxide into 02 and H20
- ethanol: alcohol dehydrogenase breaks it down to ethanal-> ethanoate
13
Q
What happens if C02 + ammonia are not excreted properly?
A
- accumulate + change cytoplasm + body fluid pH, which can cause enzymes to work less efficiently
14
Q
What is the effect on body if C02 is allowed to accumulate?
A
- cells damaged if blood pH fall below normal range
15
Q
What is the effect on body if ammonia is allowed to accumulate?
A
- increases cytoplasm pH + interferes with metabolic processes + receptors for neurotransmitters in the brain
