Topic 4 - The Cardiovascular System Flashcards
What is the cardiovascular system responsible for?
The bulk transport of oxygen and nutrients to the tissues and waste products, including carbon dioxide away from the tissues
It also serves a vital role in the endocrine and immune systems, transporting hormones to their target tissues and conveying the cells and molecules needed to fight infection
What is the mediastinum?
The central compartment of the thoracic cavity, situated between the lungs
What does the mediastinum contain?
All the thoracic structures except the lungs and is a highly mobile region in the living because it consists primarily of hollow visceral structures which are joined by loose connective tissues
Where does the mediastinum lie?
The mediastinum extends from the superior thoracic aperture to the diaphragm and from the sternum and costal cartilages to the bodies of the thoracic vertebrae
Where does the superior mediastinum lie?
This extends inferiorly from the superior thoracic aperture to the horizontal place, which includes the sternal angle and passes approximately through the junction of T4 and T5 vertebrae posteriorly
What does the superior mediastinum contain?
The roots of the great vessels, the oesophagus and the trachea
What is the sternal angle?
The joint between the manubrium (top part) and the body (middle part) of the sternum, it is a landmark which identifies the division between the superior and inferior mediastinum
What is the inferior mediastinum subdivided into?
The inferior mediastinum is subdivided into the anterior, middle and posterior parts
Which part of the mediastinum has the heart?
Middle mediastinum
Where does the inferior mediastinum lie?
The inferior mediastinum extends inferiorly from the sternal angle to the diaphragm
Where does the phrenic nerve lie?
The phrenic nerve lies in front of the root of the lung
Where does the vagus nerve lie?
The vergus nerve lies behind the root of the lung
Where does the pulmonary artery lie?
The pulmonary artery lies above the pulmonary veins
What does the heart lie within?
The heart lies within a fibrous pericardial sac
Where is the pericardial sac blended?
The pericardial sac is blended inferiorly with the central tendon of the diaphragm
What is the outer layer of the pericardium like and what does it do?
The pericardial sac has a touch fibrous outer layer (the fibrous pericardium) which protects the heart against sudden over filling by physically preventing over expansion
What is the outer layer of the pericardium called?
The fibrous pericardium
What is the internal surface of the pericardium lined with?
Serous membrane (parietal layer of serous pericardium) which passes onto the surface of the heart (visceral layer of serous pericardium) to provide a continuous membrane surrounding the fluid filled pericardial cavity
What is the epicardium?
The epicardium is the name given to the external layer of the heart but it is actually just the visceral layer of the serous pericardium
What does the pericardium consist of?
The pericardium consists of three layers: fibrous pericardium, parietal pericardium, visceral pericardium
Describe the layers of the pericardium:
The pericardium consists of three layers:
The most superficial is the fibrous pericardium, this strong layer prevents overexpansion of the heart and protects the heart from damage
The two deeper layers are continuous with each other at the root of the great vessels
The more superficial of the two is the parietal pericardium which lines the inner surface of the fibrous pericardial sac
The deeper layer is the visceral pericardium which forms a covering for the heart, also known as the epicardium
The parietal and visceral pericardium enclose the pericardial cavity which contains pericardial fluid
This reduces friction between the two moving surfaces
What does the fluid in the pericardial cavity do?
It allows the heart to beat in an almost frictionless environment, similar to the pleura around the lungs
What is the heart?
The heart is a self-adjusting double pump that propels blood around two circulatory systems in series
What are the two circulatory systems?
The pulmonary and systemic systems
What is the heart made up of?
The heart consists of 4 chambers, 2 atria and 2 ventricles and is formed from specialised cardiac muscle known as myocardium
What is heart muscle called?
Cardiac muscle, myocardium
What does each cycle consist of?
Each cycle consists of contraction and relaxation
What is each cycle of contraction and relaxation known as?
A heart beat
What is contraction of the ventricles known as?
Systole
What is relaxation of the ventricles called?
Diastole
Is pulmonary circulation low or high pressure?
Low pressure, not much force is required to send blood the short distance through the lungs from the right to the left of the heart
What would happen if there was high pressure in pulmonary capillaries?
High pressure in pulmonary capillaries would force fluid out of the blood into the lung tissue and we would drown
Describe the route of blood to the lungs and its relative oxygen concentration:
Blood pumped to the lungs from the right ventricle has very low oxygen concentration, blood leaves the right ventricle through the pulmonary trunk which divides to give right and left pulmonary arteries, oxygenation of this blood occurs in the lungs before it returns to the heart through a series of pulmonary veins which enter the left atrium
What does pulmonary refer to?
The lungs
What does systemic refer to?
Affecting the whole body
What does the systemic circulation feed?
The systemic circulation feeds into and out of all the organs of the body except the lungs
What is the origin of systemic circulation?
The left ventricle
Where is the termination of systemic circulation?
The right atrium
What level of pressure is the systemic circulation at?
High pressure, considerable force is required to adequately perfuse all the tissues in the human body and the blood has a much larger distance to travel from left to right heart than right to left
What are the layers of the heart (superficial to deep)?
Epicardium (visceral pericardium/serous pericardium): the epicardium consists of a layer of connective tissue and proves a protective layer over the heart
Myocardium: this is the muscular component of the heart wall, it consists of myocytes or cardiac muscle cells
Endocardium: this layer of epithelium and connective tissue lines the heart and covers the heart valves, the endocardium is continuous with the endothelial lining of blood vessels
What is diastole?
Relaxation of heart muscle, conventionally it is used to describe ventricular relaxation but can be atrial; diastole is a valid term to describe atrial relaxation
What is systole?
Contraction of heart muscle, conventionally it is used to describe ventricular contraction but, like diastole, atrial systole is a valid term to describe atrial contraction
What are the 4 chambers of the heart?
Right and Left atrium
Right and Left ventricle
How do the atria lie to the ventricles?
The atria lie superior to the ventricles
What seperates the atria?
The atria are separated by the interatrial (IA) septum
What do the atrium fill with?
The right atrium fills with deoxygenated blood from systemic circulation
The left atrium fills with oxygenated blood from the pulmonary circulation
Which are more muscular atria or ventricles? Which side in particular?
The ventricles are more muscular than the atria
The left ventricle is especially muscular as it has to push blood around the whole body, the right ventricle only pushes blood around the lungs before it returns to the heart
What divides the ventricles?
The ventricles are divided by the interventricular (IV) septum
What drains into which atria?
These thin walled chambers receive blood from the circulatory system, the pulmonary circulation drained into the left atrium through the pulmonary veins and the systemic circulation drains into the right atrium through the superior and inferior vena cava
Blood from the atria then progresses into the ventricles
What are the ventricles?
The ventricles are thick-walled muscular chambers which propel blood around the pulmonary and systemic circulatory systems
Which ventricle is the most muscular?
The left ventricle is more muscular than the right, more force is required from the left ventricle to create the higher pressure needed for tissue perfusion in the systemic circulation
How are muscles fibres in the ventricle organised?
Muscle fibres in the ventricles are arranged so that ventricular contraction prowesses upwards in a spiral from the apex of the heart, towards the vessels leading out of the ventricles
What does the superior vena cava do?
The superior vena cava bring de-oxygenated blood to the right atrium from the systemic circulation superior to the heart i.e. upper limbs, thorax, head and neck
What does the inferior vena cava do?
The inferior vena cava brings de-oxygenated blood to the right atrium from the systemic circulation inferior to the heart i.e. the abdomen, pelvis and lower limbs
What does the pulmonary trunk do?
The pulmonary trunk exits the right ventricle, taking deoxygenated blood to the lungs, immediately superior to the heart it bifurcates into the right and left pulmonary arteries which run into their respective lungs
What are the 4 pulmonary veins and collectively what do they do?
Left super and inferior pulmonary veins
Right superior and inferior pulmonary veins
The pulmonary veins enter the left atrium on the posterior aspect of the heart, carrying oxygenated blood from the pulmonary circulation
What does the aorta do?
The aorta, known as the ascending aorta as it leaves the heart, this vessel carries high pressure, oxygenated blood to the body in the systemic circulation
What have cardiac valves evolved to do?
Cardiac valves have evolved to allow unimpeded unidirectional flow from atria to ventricles or ventricles to great vessels
If it were not for the valves of the heart, contraction of the wall surrounding the ventricles would send the blood both forwards, into the pulmonary artery and aorta, backwards into the atria
Relaxation of the ventricles would also allow blood to re-enter the heart from the pulmonary artery and aorta
The valves prevent backflow of the blood which would render the pumping action of the heart ineffectual
Where is the atrioventricular valve?
The AV valve is between the atria and ventricles which prevents back flow of blood from the ventricles into the atria during systole
Describe the different AV valves:
The AV valves consist of leaf shaped cusps, increased pressure in the ventricles during systole forces the cusps together to form a tight seal
Papillary muscles and chordae tendineae attached to the cusps ensure proper closure and prevent inversion
The tricuspid valve between the right atrium and ventricle has three cusps, the mitral valve between the left atrium and ventricle is the only heart valve to consists of just two cusps
The tricuspid valve consists of three leaflets (or cusps) and the mitral valve of two, they are prevented from inverting by the action of the papillary muscles and chordae tendineae, during systole the papillary muscles contract, this causes tension in the papillary tendons that are attached to each valve leaflet, which ensures precise closure and prevents inversion
What are semi lunar valves?
Semi lunar valves are the valves between the ventricles and great vessels, they prevent back flow of blood into the heart during diastole
Where is the aortic valve found?
The aortic valve is found between the left ventricle and aorta
Where is the pulmonary valve found?
The pulmonary valves is found between the right ventricle and the pulmonary artery
How many cusps are in semi lunar valves?
Semi lunar valves consist of three cusps shaped like pockets
What are the spaces behind the aortic valves called?
The spaces behind the aortic valves are known as aortic sinuses, blood flow back towards the heart at the end of systole cause these sinuses to fill with blood, ballooning and closing the valve
What causes AV valves to close?
Ventricular contraction causes the AV valves to close, which signals the start of ventricular systole
What causes the semilunar valves to open?
Ventricular contraction increases pressure in the ventricles above the pressure in the aorta and the pulmonary trunk causing the semilunar valves to open
What causes semi lunar valves too close?
When ventricles and pressure drop, blood flowing back towards relaxed ventricles causes semi lunar valves to close, which is the beginning of ventricular diastole, AV remains closed
What causes AV valves to open?
When pressure in ventricles becoming lower than atria, AV valves open and blood flows into ventricles, atria then contract and complete ventricular filling
What is auscultation?
Listening to the sounds of the heart with a stethoscope, this is a valuable diagnostic technique
What causes the heart sounds and what are they?
There are two heart sounds: one corresponding with the closure of the AV valves (lub) and another corresponding to the closure of the semilunar valves (dub)
How many borders of the heart are there?
There are 4 borders of the heart and these are visible in both anterior and posterior views and in particular when the heart is viewed radiographically
What forms the right border?
The right border is formed by the right atrium, it extends from the superior to inferior vena cava
What forms the inferior border?
The inferior border is roughly horizontal and mostly formed by the right ventricle, with a small contribution by the left ventricle
What forms the left border?
The left border is mostly formed from the left ventricle with the superior portion being formed by the auricular appendage of the left atrium
What forms the superior border?
The superior border is formed by both atria; the aorta and pulmonary trunk arise from this border and the superior vena cava enters the heart at the right side of the superior border
What is the anterior surface of the heart?
The anterior/sternocotal surface is formed mostly from the right ventricle, this surface is related anteriorly to the sternum and the ribs
What is the inferior surface of the heart?
The inferior/diaphragmatic surface of the heart is formed mostly by the left and partly from the right ventricle, it is related inferiorly to the centre of the diaphragm
What is the left surface of the heart?
The left/pulmonary surface of the heart is formed mostly by the left ventricle, it is related latterly with the left lung and occupies a depression in the lung known as the cardiac impression
Where is the base of the heart?
The base is situated on the posterior aspect, directed towards the vertebrae T6-9
What forms the base of the heart?
The base of the heart is formed mostly from the left and partly from the right atrium and extends from the bifurcation of the pulmonary trunk superiorly to the atrioventricular groove inferiorly
Where does the apex of the heart lie?
The apex of the heart lies posterior to the 5th intercostal space in the midclavicular line
What direction is the apex of the heart directed?
The apex of the heart is directed anterograde-inferiorly and to the left
Where is the loudest part of the heart beat found?
Directly superficial to the apex, on the surface of the thorax
What are papillary muscles?
Papillary muscles are extensions of the muscles of the ventricular wall in both the left and right ventricles
How are papillary muscles attaches the valves (Which valves?)?
Papillary muscles are attached to the mitral and tricuspid valves via the insensible papillary tendons (AKA chordae tendineae)
What do the papillary muscles do during systole?
During systole the papillary muscles contract and prevent the valves from inverting asa result of the high pressure created in the contracting ventricle
What would happen in there was back flood of blood into the atria?
Backflow of blood into the atria would damage their walls and valves, it would also reduce efficiency of ventricular contract in pumping blood into the pulmonary and systemic circulation
