Topic 4.4 Circulation Flashcards
Relate the structure of the hearts chambers to their function
- Atria: thin-walled and elastic, so they can stretch when filled with blood
- Ventricles: thick muscular walls pump blood under high preasure. The left ventricle is thicker than the right side because it has to pump blood all the way around the body
Relate the structure of the arteries to their function
Thick muscular walls to handle high pressure without tearing. Elastic tissue allows recoil. Narrow lumen to maintain pressure.
Relate the structure of veins to their function
Thin walls due to lower pressure. Require valves to ensure blood doesn’t flow backwards. Have less muscular and elastic tissue as they don’t have to control blood flow.
Relate the structure of capillaries to their function
- Walls only one cell thick; short diffusion pathway
- Very narrow, so can permeate tissues and red blood cells can lie flat against the wall, effectively delivering oxygen to tissues
- Numerous and highly branched, providing a large surface area
Why are two pumps (left and right) needed instead of one?
To maintain blood pressure around the whole body. When blood passes through the narrow capillaries of the lungs, the pressure drops sharply and therefore would not be flowing strongly enough to continue aroun the whole body. Therefore it is returned to the heart to increase the pressure.
Describe what happens during cardiac diastole
The heart is relaxed. Blood enters the atria, increasing the pressure and pushing open the atrioventricular valves. this allows blood to flow into ventricles. Preasure in the heart is lower than in the arteries, so semilunar valves remain closed.
Describe what happens during atrial systole
The atria contract pushing blood into the ventricles.
Describe what happens during ventricular systole
The ventricles contract. The pressure increases, closing the atrioventricular valves to prevent backflow, and opening the semilunar valves. Blood flows into the arteries.
What does myogenic mean?
The heart’s contraction is initiated within the muscle itself, rather than by nerve impulses.
Name the nodes involved in the heart contaction and where they are situated
- Sinoatrial node (SAN) = wall of right atrium
- Atrioventricular valve (AVN) = in between the two atria
Explain how the heart contracts
- SAN initiates and spreads impulse across the atria, so they contract
- AVN recieves, delays, and then conveys the impulse down the bundle of His
- Impulse travels into the Purkinje fibres which branch across the ventricles, so they contract from the bottom up
Why does the impulse need to be delayed?
If the impulse spreads straight from the atria into the ventricles, there would be not enough time for atrial systole to complete.
What is an ECG?
A graph showing the amount of electrical activity in the heart during the cardiac cycle
What does each element of an ECG represent?
- P-wave shows atrial systole caused by the SAN
- QRS complex shows ventricular systole
- T-wave shows systole as the ventricles repolarise
Describe the function of the blood
- Transport of nutrients and waste
- Forms tissue fluid
- Defend against foreign bodies
What are the main components of blood?
- Erythrocytes (red blood cells)
- Leucocytes (white blood cells)
- Plasma
Describe the structure of erythrocytes and their function
Biconcave shape, no nucleus, contain lots of haemoglobin. Function is to carry oxygen.
Give types of leucocytes
Order them into granulocytes and agranulocytes
Granuloctyes:
* Basophill
* Neutrophill
* Eosenophill
Agranulocytes:
* Lymphocytes
* Monocytes
What are granulocytes?
These leucocytes have granules in the cytoplasm of the cells that take up stain and are obvious under the microscope. They have lobed nuclei
What are agranulocytes?
These leucoytes don’t have granules to take up stain in their cytoplasm. They have unlobed nuclei
Describe the structure of neutrophill and their function
Part of the non-specific immune system, they engulf and digest pathogens by phagocytosis. They have multi-lobed nuclei.
Describe the structure of eosinophill and their function
Part of the non-specific immune system. They are stained red by eosin stain. They are important as they contain enzymes that detoxify proteins.
Describe the structure of basophill and their function
Part of the non-specific immune system. They have a two-lobed nucleus. They produce histimines involved in inflammation and allergic reactions.
Describe the structure of monocytes and their function
Part of the specific immune system. They’re the largest of the leucocytes. They can move out of the blood and into the tissues to form macrophages, that also play an important part of the specifc immune response. they engulf pathogens by phagocytosis.
Describe the structure of lymphocytes and their function
Small leucocytes with very large nuclei that are vitally important in the specific immune response of the body.
Describe the function of plasma
Contains water, proteins, ions, nutrients, gases, and hormones. Delivers them to cells. Makes up 55% of blood.
Why does blood need to clot?
- Prevents blood loss
- Prevents entry of harmful bacteria
- provides a framewrok for repair
Explain the process of blood clotting
- Platelets release thromboplatin in response to damage
- Causes prothrombin to change to its active form, thrombin (calcium and vitimin K are involved in creating thrombin)
- Turns soluble fibrinogen into insoluble fibrin, forming a mesh that traps blood cells
What causes atherosclerosis?
Build-up of fibrous plaque. Endothelium becomes damaged which can cause a blood clot. Cells, salts cholesterol and other substances build up and harden, forming a plaque that narrows the artery.
How does atherosclerosis affect health?
Increases risk of cardiovascular diseases such as hearth attack, stroke and angina
Give factors that increase risk of atherosclerosis
Age, genetics, smoking, alcohol, lack of exercise, obesity, cholesterol levels.
What conditions can atherosclerosis lead to?
- Anuerism
- Raised blood preasure
- Angina
- Heart attack
- Stroke
What is an aneurism?
Where the increased preasure of blood caused by a blockage can lead to the artery bursting, and internal bleeding.
What is angina?
Narrowing of coronary arteries reduces blood flow to the heart and causes chest pain on exercise
