Cardiovascular system Flashcards
What is the cardiovascular system?
organ system responsible for transporting oxygen, carbon dioxide and nutrients etc.
Where does gas exchange occur in the CVS?
capillaries
Components of the CVS
heart, blood vessels, blood, (lymphatic system works in conjunction with CVS)
Components of blood
erythrocytes, leucocytes, platelets, plasma
What is the lymphatic system?
Organ system that transports excess interstitial fluid as lymph before returning it to venous circulation. Key part of immune system.
Description of capillary microcirculation
The high HP at the arteriole end of the capillary forces out blood plasma to form interstitial fluid. As the volume of blood plasma has decreased in the venous end, this causes a lower HP but increases the osmotic pressure. This draws interstitial fluid back into capillaries.
What are the two loops of circulation?
pulmonary and systemic circulation
Outline of pulmonary circulation
deoxygenated blood is transported out of the RV via the pulmonary trunk which bifurcates into the left and right pulmonary arteries. Gas exchange occurs in lungs. 4 pulmonary veins (2 each side) transport oxygenated blood from lungs to the LA.
Outline of systemic circulation
Oxygenated blood is transported from the LV to the body via the aorta. Deoxygenated blood returns to the RA via the SVC and IVC.
What is the mediastinum?
anatomical region in middle of thorax bordered by pleural cavities (contain lungs)
How is the mediastinum divided?
Into the superior and inferior mediastinum. The inferior mediastinum is further divided into the anterior, middle and posterior mediastinum.
Borders of the superior mediastinum
Bordered superiorly by T1 posteriorly and the superior aspect of the manubrium anteriorly. Bordered inferiorly by the sternal angle anteriorly and T4/5 posteriorly.
What structures are found in the superior mediastinum?
Aortic arch and its branches (SCCS), trachea, oesophagus, thymus gland.
Function of thymus gland
Immune system development in childhood after which it atrophies.
Borders of inferior mediastinum
anteriorly extends from sternal angle to diaphragm, posteriorly extends from T5 to T12
Structures found in anterior mediastinum
remnants of thymus, fat
Structures found in middle mediastinum
heart
Contents found in posterior mediastinum
oesophagus and descending aorta
What is the pericardium?
Double-layered membrane that surrounds the heart
Structure of the pericardium
made of 2 layers - outer fibrous layer and inner serous layer (divided into parietal and visceral layers with pericardial cavity between)
Function of fibrous layer of pericardium
dense CT that protects the heart and anchors it to the diaphragm (and prevents over-expansion, can restrict in case of pericardial effusion)
What is pericardial effusion?
Abnormal accumulation of serous fluid in pericardial cavity/space
Structure of serous pericardium
made of a parietal layer that lines inner surface of fibrous pericardium and a visceral layer that adheres to the heart surface. Separated by pericardial space/cavity
Function of pericardial space/cavity
contains lubricating serous fluid that reduces friction during heart beats
Function of superior vena cava
transports deoxygenated blood from head, neck and upper limbs to RA
Function of inferior vena cava
transports deoxygenated blood from below the level of the heart to the RA
Function of pulmonary trunk
carries deoxygenated blood from RV towards lungs and bifurcates into left and right pulmonary arteries
Order of branches from the aortic arch (R->L)
Brachiocephalic trunk (branched into right subclavian and right common carotid artery), left common carotid artery, left subclavian artery. (SCCS)
Which arteries branch from brachiocephalic trunk
Right subclavian artery, right common carotid artery.
What is an auricle?
A muscular pouch that can increase atrial capacity and relieve high atrial pressure during times of stress.
Alternative name for auricle
atrial appendage
Where are auricles found?
Anterior surface of each atria
Which blood vessel transports oxygen rich blood from the mother to the foetus?
Umbilical vein
What happens at the placenta?
Exchange of oxygen and nutrients between foetal and maternal blood
Name of structure used to bypass liver in foetal circulation?
Ductus venosus
Where does 30% of the blood in the umbilical vein enter foetal circulation?
IVC (to RA) as the blood bypasses the liver via the ductus venosus
What is the remnant of the ductus venosus
ligamentum venosum
Where is the ligamentum venosum found?
passes superiorly from porta hepatis to IVC (near caudate lobe)
How does blood bypass the lungs in foetal circulation?
Foramen ovale allows blood to flow from RA to LA (then to LV and systemic circulation. Ductus arteriosus links pulmonary trunk to aorta (for any blood that doesn’t pass though foramen ovale)
What is the foramen ovale?
Opening between the right and left atria that allows oxygenated blood to bypass lungs and enter the systemic circulation (RA -> LA -> LV -> aorta)
What is the remnant of the foramen ovale?
fossa ovalis
What is the ductus arteriosus?
A vessel connecting the pulmonary trunk to the aorta, allowing blood to bypass the lungs and enter systemic circulation.
Why are the lungs bypassed in foetal circulation?
They are not yet fully developed - filled with fluid and not yet involved in gas exchange.
Function of umbilical artery
carry deoxygenated blood and waste products away from the foetus to the placenta for exchange with mother’s blood.
After birth, which structures from foetal circulation are sealed?
Ductus venosus, foramen ovale, ductus arteriosus.
Name of thick, muscular layer of heart wall
myocardium
Function of myocardium
thick, muscular layer that contracts and relaxes to pump and receive blood
What is the myocardium composed of?
cardiac muscle cells (cardiomyocytes)
Name of innermost layer of heart wall
endocardium
What is the endocardium?
the innermost layer of the heart wall. It is thin (single layer of endothelial cells) and has a smooth lining.
Function of endocardium
reduces friction and prevents blood clot formation
Name of irregular muscular projections on the inner surface of ventricles
trabeculae carnae
Where are trabeculae carnae found?
Inner surface of ventricles
What layer of the heart contains coronary arteries and veins?
epicardium (visceral layer of serous pericardium) - outermost layer of heart wall before cavity
Which heart layer makes up the epicardium?
Visceral layer of serous pericardium - outermost layer of heart wall
Function of coronary arteries
supply oxygenated blood to the heart muscle from the aortic sinus.
Function of coronary veins
transport deoxygenated blood from the heart muscles into the RA (mainly via coronary sinus)
What are the aortic sinuses?
3 widenings/dilations of the blood vessel wall above the aortic valve
Where to the left and right coronary arteries arise from?
the left and right aortic sinuses (2/3)
Where an external pacemaker typically placed?
Right auricle / appendage (close to SAN)
Name of muscle in inner atrial wall
Pectinate muscles / musculi pectinate
Function of pectinate muscles
Allows the atria to stretch and increase its volume when filling with blood
Function of coronary sinus
drains deoxygenated blood from the coronary veins into the RA
Location of pulmonary valve
base of pulmonary trunk between the RV and the pulmonary trunk. Anterior portion of heart
How many cusps/leaflets does the pulmonary valve have?
3
Where is the aortic valve located?
Between the LV and aorta (middle/anterior of heart)
How many cusps/leaflets does the aortic valve have?
3
Function of pulmonary valve
prevents backflow into RV
What is the infundibulum of the RV?
(aka conus arteriosus) is a smooth walled funnel shaped part of the RV leading towards the pulmonary valve (no trabeculae)
Name of the AV valve between the RA and RV
tricuspid valve (3 leaflets)