Unit 5.2- Excretion as an Examples of Homeostatic control Flashcards
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Excretion definition:
The removal of metabolic waste from the body
Metabolic waste definition:
A substance that is produced in excess by the metabolic presses in the cells; it may become toxic
What are the main excretory products?
- Carbon dioxide from respiration
- Nitrogen-containing products such as urea
- Other compounds, such as the bile pigments found in faeces
Egestion definition:
The elimination of faeces from the body
What are the excretory organs?
- The lungs
- The liver
- The kidneys
- The skin
How do the lungs excrete carbon dioxide?
Carbon dioxide diffuses into the alveoli to be excreted as you breathe out.
How does the liver excrete substances?
- Some substances produced will be passed into the bile for excretion with the faeces, e.g. the pigment bilirubin
- The liver is also involved in converting excess amino acids into urea through deamination and the ornithine cycle
How are the kidneys involved in excretion?
-Urea is removed from the blood to become part of the urine
How is the skin involved in excretion?
Sweating
Why is excretion important?
Allowing the products of metabolism to build up could be fatal
Why are there hydrogen ions in the blood?
Carbon dioxide mostly travels in the blood as hydrogencarbonate ions, but forming this also creates hydrogen ions
What do hydrogen ions change the PH of?
The cytoplasm of red blood cells
What can happen if the PH of the blood drops below 7.35?
-Headaches
-Drowsiness
-Confusion
-Restlessness
-Tremor
-Rapid heart rate
-Changes in blood pressure
This is respiratory acidosis
What causes respiratory acidosis?
Blockage of the airway
Hepatocytes definition:
Liver cells
What are the blood vessels going to and from the liver?
To: -Hepatic artery -Hepatic portal vein Away: -Hepatic vein
What does the hepatic artery do?
Supplies the liver with oxygen for aerobic respiration. it needs a lot of oxygen to carry out all the metabolic processes
What does the hepatic portal vein do?
- Carries deoxygenated blood from the intestine to the liver
- The blood is rich in the products from digestion
- May also contain toxic compounds that have been absorbed from the intestine
- Important that this blood does not circle the rest of the body before the concentrations of these substances have been adjusted.
What does the hepatic vein do?
- Blood leaves liver via hepatic vein
- Joins up with vena cava
What does the bile duct do?
- Carries bile from the liver to the gall bladder where it is stored until required to aid the digestion of fats in the small intestine
- Bile also contains some excretory products such as bile pigments like bilirubin which will leave the body with the faeces
How is the liver arranged?
- To ensure the greatest possible contact between the blood and the hepatocytes
- The liver is divided into lobes which are further divided into cylindrical lobules
What happens to the hepatic artery and hepatic portal vein as they enter the liver?
- They split into smaller and smaller vessles
- The vessels run between and parallel to the lobules
- They are known as inter-lobular vessels
What is a sinusoid?
- A chamber lined with liver cells
- At intervals in the lobules, blood from the hepatic artery and the hepatic portal vein enter, mix, and then pass down a sinusoid
- As the blood flows along a sinusoid it is in close contact with the liver cells, which are able to remove substances from the blood, and return other substances to the blood
- The concentrations of many components are modified along the sinusoid
Kupffer cells definition:
Specialised macrophages