Mass transport in animals Flashcards
The role of haemoglobin and red blood cells in the transport of oxygen
The majority of oxygen transported around the body is bound to the protein haemoglobin in red blood cells
Red blood cells are also known as erythrocytes
Each molecule of haemoglobin contains four haem groups, each able to bond with one molecule of oxygen
This means that each molecule of haemoglobin can carry four oxygen molecules, or eight oxygen atoms in total
The loading, transport and unloading of oxygen in relation to the oxyhaemoglobin dissociation curve
The oxygen dissociation curve shows the rate at which oxygen associates, and also dissociates, with haemoglobin at different partial pressures of oxygen (pO2)
Partial pressure of oxygen refers to the pressure exerted by oxygen within a mixture of gases; it is a measure of oxygen concentration
Haemoglobin is referred to as being saturated when all of its oxygen binding sites are taken up with oxygen; so when it contains four oxygen molecules
The ease with which haemoglobin binds and dissociates with oxygen can be described as its affinity for oxygen
When haemoglobin has a high affinity it binds easily and dissociates slowly
When haemoglobin has a low affinity for oxygen it binds slowly and dissociates easily
In other liquids, such as water, we would expect oxygen to becomes associated with water, or to dissolve, at a constant rate, providing a straight line on a graph, but with haemoglobin oxygen binds at different rates as the pO2 changes; hence the resulting curve
It can be said that haemoglobin’s affinity for oxygen changes at different partial pressures of oxygen
The effects of carbon dioxide concentration on the dissociation of oxyhaemoglobin (the Bohr effect)
Increases dissociation of oxygen, by decreasing blood pH
When the partial pressure of carbon dioxide in the blood is high, haemoglobin’s affinity for oxygen is reduced
This is the case in respiring tissues, where cells are producing carbon dioxide as a waste product of respiration
This occurs because CO2 lowers the pH of the blood
CO2 combines with water to form carbonic acid
Carbonic acid dissociates into hydrogen carbonate ions and hydrogen ions
Hydrogen ions bind to haemoglobin, causing the release of oxygen
This is a helpful change because it means that haemoglobin gives up its oxygen more readily in the respiring tissues where it is needed
On a graph showing the dissociation curve, the curve shifts to the right when CO2 levels increase
This means that at any given partial pressure of oxygen, the percentage saturation of haemoglobin is lower at higher levels of CO2
The general pattern of blood circulation in a mammal
Mammals have a double circulatory system
Blood passes through the heart twice on a complete circuit of the body
Oxygenated blood leaves the heart through the aorta to the rest of the body, oxygen is given to respiring tissue, then deoxygenated blood enters the heart through the vena cava
The blood leaves to the lungs via the pulmonary artery, becomes oxygenated, then enters the left side of the heart via the pulmonary vein, ready to be pumped out through the aorta
The renal artery takes blood to the kidneys, where it leaves by the renal vein
The coronary arteries take oxygenated blood to heart cells
The gross structure of the human heart
Right atrium:
Deoxygenated blood flows into the right atrium from the body
The vein that pumps deoxygenated blood into the right atrium is called the vena cava
The right atrium is the first chamber that deoxygenated blood flows through
Right ventricle:
When the walls of the right atrium contracts, deoxygenated blood flows into the right ventricle
The atrioventricular valves prevent blood from flowing back into the atria from the ventricles
Then the walls of the right ventricle contracts, blood is pumped out of the pulmonary artery to the lungs
The semi-lunar valves prevent blood from flowing back into the right ventricle from the pulmonary artery
Left atrium:
Oxygenated blood flows into the left atrium from the lungs
The vein that pumps oxygenated blood into the left atrium is called the pulmonary vein
Left ventricle:
When the walls of the left atrium contracts, oxygenated blood flows into the left ventricle
The atrioventricular valves prevent blood from flowing back into the atria from the ventricles
The walls of the left ventricle are considerably thicker than the right ventricle
The left ventricle has to transport blood all the way around the body but the right ventricle only has to transport blood to the lungs
Aorta:
When the left ventricle contracts, blood is pumped out of the heart to the rest of the body
Oxygenated blood leaves the heart through the aorta
The semi-lunar valves prevent blood from flowing back into the left ventricle from the aorta
Pressure and volume changes and associated valve movements during the cardiac cycle that maintain a unidirectional flow of blood
- Atria contract, ventricles relax
Volume ↓inside atria , ∴ pressure ↑.
This pushes blood into ventricles. Ventricular pressure ↑ slightly, Chamber volume ↑. - Ventricles contract, atria relax
pressure ↑, becomes ↑er than in atria.
AV valves shut to prevent backflow.
SL valves open, (as ventricular pressure is ↑er than in aorta/pulmonary artery).
3.Ventricles relax, atria relax
↑er pressure in pulmonary artery/aorta shuts SL valves.
Atria begin to fill again (↑er pressure in vena cava + pulmonary vein)
Atria have higher pressure than V’s so AV Valves open and blood flows passively (gravity) into ventricles…
contract (systole)
relax (diastole)
The structure of arteries, arterioles and veins in relation to their function
Pulmonary arteries carry blood low in oxygen exclusively to the lungs for gas exchange
Pulmonary veins then return freshly oxygenated blood from the lungs to the heart to be pumped back out into systemic circulation
Arteries general appearance:
Thick walls with small lumens
Generally appear rounded
Veins general appearance:
Thin walls with large lumens
Generally appear flattened
An arteriole is a very small artery that leads to a capillary
The importance of the arterioles is that they will be the primary site of both resistance and regulation of blood pressure
The formation of tissue fluid and its return to the circulatory system
High hydrostatic pressure forced fluid out
Large proteins remain in capillary
Low water potential in capillary due to plasma proteins
Water re-enters capillary by osmosis
Lymphatic system return excess fluid to circulatory system
