6.2 The Blood System Flashcards
What is the circulatory system
The circulatory system is the main transport system in all mammals, including humans. This system is designed to move nutrients, like oxygen, around the body. It acomplishes this task through a muscular pump called the heart and numerous pathways that lead to every part of the body through arteries and veins.
What did William Harvey discover regarding the movement of blood in the body?
William Harvey discovered that blood circulated around the body, pumped by the heart. Harvey said that arteries and veins were part of a single network, with the heart acting as a pump. This network had two circulation loops: one that moved blood from the heart to the body and back (systemic circulaiton), and another one that moved blood from the lungs to the heart and back (pulmonary circulation)
- This overturned theories developed by the ancient Greek philosopher Galen on movement of blood in the body.
What are the arteries that are directly attached to the heart?
The aorta and the pulmonary artery
What are the veins that are directly attached to the heart?
The vena cava and the pulmonary vein
Why is the left ventricle much thicker and stronger than the right ventricle?
The left ventricle has a much thicker muscular wall (myocardium).
Because it has to generate enough pressure to move the blood through out the entire body, while the right ventricle only has to generate enough pressur eto move blood to the lungs.
Pressure changes in the cardiac cycle
As the heart is beating, there are different changes in pressure within each chamber.
Atrial pressure:
- Atrial pressure, is consistently lower than the pressure in the ventricles and the aorta
- This is because the atria only need to push blood into th eventricles, which are directly below them (does not require much pressure.
Ventricular and aortic pressure at their peak:
- During this part of the graph is when the ventricles are contracting and the valves are opening
- The ventricles need to push blood at high pressure, because they have to move the blood either throughout the entire body or to the lungs
The ventricles act as ____ and expel blood from the heart at ____ pressure via ___
pumps, high, arteries
The left side of the heart pumps what type of blood and to where?
oxygenated blood to the body
The right side of the heart pumps what type of blood and to where?
deoxygenated blood to the lungs
What is the structure and function of arteries?
The function of arteries is to convey blood at high pressure from the heart ventricles to the tissues of the body and lungs.
They have:
- a narrow lumen
- a thick wall
- an inner layer of muscle and elastic fibres
What are the muscle and elastic fibres in the arteries for?
They assist in maintaining the high blood pressure between pump cycles.
- The muscle fibres help to form a rigid arterial wall that is capable of withstanding the high blood pressure without rupturing
- The elastic fibres allow the arterial wall to stretch and expand upon the flow of a pulse through the lumen
What is the structure and function of capillaries?
The function of capillaries is to exchange materials between the cells in tissues and blood travelling at low pressure.
They have:
- a very small lumen which allows passage of only a single red blood cell at a time
- are formed of a single layer of cells which are permeable and minimise the diffusion distance for permeable materials
Describe the flow of blood in the capillaries
- Blood flows through the capillaries very slowly and at a very low pressure in order to allow for maximal material exchange.
- The high blood pressure in arteries is dissapated by extensive branching of the vessels and the narrowing of the lumen
The higher hydrostatic pressure at the arteriole end of the capillary forces material from the bloodstream into the tissue fluid
- Material that exits the capillaries at body tissues include oxygen and nutrients (needed by the cells for respiration)
The lower hydrostatic pressure at the venule end of the capillary allows materials from the tissues to enter the bloodstream
- Materials that enters the capillaries at body tissues include carbon dioxide and urea (wastes produced by the cells)
What is the structure and function of veins?
The function of veins is to collect the blood from the tissues and convey it at low pressure to the atria of the heart
They have:
- a very wide lumen
- a thin wall containing less muscle and elastic fibres as blood is flowing at a very low pressure
- because the pressure is low, veins possess valves to prevent backflow and stop the blood from pooling at the lowest extremities
The function of valves in veins
Blood is at very low pressure in the veins which can make it difficult for the blood to move against the downward force of gravity.
- The veins contain numerous one-way valves in order to maintain the circulation of blood by preventing backflow
