1. Introduction Flashcards
Why do we need a vascular system?
While diffusion is an effective method of transporting molecules over short distances, it is very slow over long distances such as between organs. The cardiovascular system provides a faster method of transporting nutrients and oxygen to the cells and waste products such as CO2 away from cells.
Where does diffusion of nutrients take place?
The capillaries are where diffusion takes place, here the exchange of nutrients and molecules between cells of the tissue and the blood can occur.
describe the structure of capillaries that enable efficient diffusion?
Capillaries are composed of a single layer of endothelial cells surrounded by basal lamina.
lipid soluble molecules such as O2 and CO2 can diffuse across the endothelial cells.
This increases the efficiency of gas exchange.
They have fenestrations that allow small water soluble molecules to pass through.
Give the purpose of the Cardiovascular system
- Takes oxygen and nutrients to the tissue capillaries where diffusion can take place
- Take carbon dioxide and waste products from body tissues into the blood at capillaries
- It’s used to deliver between 5 and 25 l.min-1 of blood to the body
- It maintains a blood flow of 750 ml.min-1 to the brain at all times
- It also maintains blood flow to the heart muscle and kidneys at all times
In order to carry out its functions what features does the CVS need
• a pump - the heart
• distribution vessels - the arteries
• a mechanism to control blood flow so that the cardiac output is distributed appropriately.
Flow control is via resistance vessels - the arterioles and pre capillary sphincters.
• The ability to cope with changes in the cardiac output. This requires capacitance in the system - a ‘store’ of blood that can be called upon to cope with temporary imbalances between the amount of blood returning to the heart and the amount that it is required to pump out. This store is in the veins.
what are coronary arteries?
The coronary arteries are the blood vessels (arteries) that transport oxygenated blood to the cells of the heart. The heart requires a continuous supply of oxygen to function and survive. they are the first branch of the aorta.
what are the two main branches of coronary arteries?
The coronary arteries wrap around the entire heart. The two main branches are the left coronary artery (LCA) and right coronary artery (RCA).
where do both the main coronary arteries stem from?
the aorta
what does reduced function of the coronary arteries lead to?
Reduced function of the coronary arteries can lead to decreased flow of oxygen and nutrients to the heart. Not only does this affect supply to the heart muscle itself, but it also can affect the ability of the heart to pump blood throughout the body. Therefore, any disorder or disease of the coronary arteries can have a serious impacts on health, possibly leading to angina, a heart attack, and even death.
what does the right coronary artery branch into?
the posterior interventricular artery/ posterior descending artery and the right marginal artery
what does the left coronary artery branch into?
the anterior interventricular artery/ left anterior descending artery(LAD) and the circumflex artery
describe the circumflex artery
it goes all the way around the back of the heart supplying oxygen to the myocardium
summarise coronary arteries
• Vital to supply well oxygenated blood to the myocardium
BUT
• End arteries (few anastomoses – they don’t connect together much)
• Prone to atheroma (narrowing due to atheromatous plaque formation)
what happens if a coronary artery becomes blocked?
A complete blockage of a coronary artery can result in myocardial infarction. Symptoms include - Sweating - Paleness of the patient - Feeling sock/ vomiting - Severe chest pain - Breathlessness - Pain radiating up the neck and the jaw
why is the left anterior descending artery nicknamed the widow maker?
it is the artery that is usually blocked during a myocardial infarction
where does the heart sit?
heart is located within the thoracic cavity, medially between the lungs in the space known as the mediastinum. the mediastinum is the intervening region in the thoracic cavity between the right and left pleural cavities which are occupied by the lungs. Within the mediastinum, the heart is separated from the other mediastinal structures by a tough membrane known as the pericardium, or pericardial sac, and sits in its own space called the pericardial cavity.
what surrounds the heart?
the pericardial sac
what is the function of the pericardial sac?
The pericardial sac surrounds the heart it fixes the heart to the mediastinum, gives protection against infection and provides the lubrication for the heart.
describe the structure of the pericardial sac?
The pericardial sac has two layers, a serous layer and a fibrous layer. It encloses the pericardial cavity which contains pericardial fluid.
The fibrous layer is the most superficial layer of the heart and it’s made up of loose and dense connective tissue.
The serous layer is divided into two other layers
what are the two layers that the serous layer of the pericardium is divided into?
the parietal layer - further away from heart
the visceral layer - closer to heart
what separates the parietal and visceral layer?
pericardial cavity which contains pericardial fluid.
to which serous layer is the fibrous layer attached to?
the parietal layer
describe the order of the layers of tissue in pericardial sac
fibrous layer parietal layer pericardial cavity visceral layer myocardium endocardium
what is the difference between myocardium and endocardium?
The endocardium is the innermost layer of tissue that lines the chambers of the heart. Its cells are embryologically and biologically similar to the endothelial cells that line blood vessels. The endocardium underlies the much more voluminous myocardium, the muscular tissue responsible for the contraction of the heart
what are the 2 pericardial sinuses?
transverse sinus
oblique sinus
describe the two pericardial sinuses
The lines of reflection between visceral and parietal pericardium form two pericardial sinuses, the transverse pericardial sinus and the oblique pericardial sinus. The transverse pericardial sinus lies anterior to the superior vena cava and posterior to the ascending aorta and pulmonary trunk.
The oblique pericardial sinus lies posterior to the heart in the pericardial sac. On the right side, the oblique sinus is bounded by the lines of reflection of the serous pericardium onto the inferior vena cava and the right pulmonary veins. On the left, the sinus is bounded only by the lines of reflection of serous pericardium onto the left pulmonary veins
what is the function of the cardiac veins?
they drain blood from cardiac cells into the cardiac sinus which drains into the right atrium
describe the route of blood through the heart.
the pulmonary vein brings oxygenated blood from the lungs into the left atrium which flows into the left ventricle and then through the aorta to the rest of the body.
The vena cava brings deoxygenated blood from the cells of the body to the right atrium which flows into the right ventricle and through the pulmonary artery to the lungs.
what is the phrenic nerve?
The phrenic nerve is a nerve that originates in the neck (C3–C5) and passes down between the lung and heart to reach the diaphragm. The phrenic nerves
also supply the pericardium
