Cardiovascular system Flashcards
Heart=
- Pumps blood around the body
- Located in the mediastinum, behind the sternum angled slightly to the left.
- Surrounded by the pericardium
What does the cardiovascular system include?
Heart & blood vessels
Blood vessels=
- Transports blood, which carries nutrients, gases, waste products, hormones and immune cells.
What is the pulmonary circuit?
- Carries deoxygenated blood from the heart to the lungs and returns oxygenated blood back to the heart.
Requires low pressure
What is the systemic circuit?
- Circulates oxygenated blood from the heart to the entire body and returns deoxygenated blood to the heart.
Requires higher pressured
What is the pericardium?
- The heart is surrounded by the pericardium
- Consists of parietal (outer) layer and visceral (inner) layer
What are the functions of the pericardium?
- Protect the heart
- Anchor the heart in position
- Prevent overfilling of heart with blood
- Fluid within pericardial cavity provides a ‘friction-free’ environment.
What is the pulmonary trunk?
- Major artery that carries deoxygenated blood from right ventricle to the lungs for oxygenation. It is in the pericardial sac
What are the three layers of the heart?
- Epicardium- on outer layer, visceral pericardium, and supports blood vessels and nerves
- Myocardium- is the middle layer, made of cardiac muscle
- Endocardium- is the inner layer, made up of squamous epithelium
What are the chambers and sets of valves in the heart?
There are four chambers and two sets of valves:
- 2x atria & 2x ventricles
- 2x atrioventricular valves & 2x semilunar valves
What is the heart separated by?
- Interventricular septum
Explain the right ventricle vs left ventricle
- Right ventricle pumps blood to lungs
- Left ventricle pumps blood to the body
What are valves?
- Prevent backflow of blood- ensure unidirectional blood flow.
- They open and close in response to pressure changes.
What are atrioventricular valves?
- Involve bicuspid and tricuspid valves.
- Located between atria and ventricles
What are semilunar valves?
- Involve pulmonary and aortic semilunar valves
- Located between ventricles and arteries leaving the heart
What are the different heart sounds?
- Lub (S1)= closure of AV valves
- Dub (S2)= closure of SL valves
What are the two main blood vessels?
- Arteries= carry blood away from heart
- Veins= carry blood towards the heart
- Arteries & veins have three layers (tunica’s) to their wall.
Name the different types of tunica’s?
- Tunica externa= outer layer, connective tissue rich in collagen
- Tunica media= middle layer, made of smooth muscle and elastic fibres. More tunica media allows blood flow to be controlled.
- Tunica intima= inner layer, made of simple squamous epithelia
What are the different types of arteries?
- Elastic= thick walled (e.g., the aorta and branches), large amounts of elastic tissue, allows for expansion and contraction causing smooth blood flow.
- Muscular= smaller, branch from elastic arteries, distribute blood to parts of the body.
- Arterioles= made of smooth muscle, surrounds endothelium, held together by outer layer of collagen fibres.
Describe smooth muscle
- Allows for regulation of blood flow to the capillaries.
- When smooth muscle is contracted, lumen of blood vessel is smaller so less blood can flow= vasoconstriction.
- When smooth muscle is relaxed, lumen of blood vessel is larger so more blood can flow= vasodilation.
What are the different types of veins?
- Capillaries= smallest of blood vessels, thin walled often just tunica intima, are sites of exchange, blood flow is much slower to allow exchange to take place, capillaries create a large surface area.
- Venules & veins= venules are formed by capillaries joining together, veins are formed by venules joining together. The blood pressure in veins is much smaller than in arteries, the tunica’s of veins are much thinner.
Explain the return of blood flow to the heart
- Superior vena cava
- Right atrium
- Tricuspid valve
- Right ventricle
- Pulmonary semi lunar valve
- Pulmonary artery
- Lungs for oxygenation
- Blood returns to heart through pulmonary veins
- Left atrium
- Bicuspid valve
- Left ventricle
- Aortic valve
- Aorta
- Body
Pulse=
- The pressure wave felt in an artery that lies close the surface of the body. The pressure wave is a result of the left ventricles contracting.
- You can count the heart rate by counting the pulse rate
- Examples of pulses: superficial temporal artery, radial artery, temporal artery
How does the heart get nourishment?
- Through coronary arteries, left coronary artery and right coronary artery, so through coronary circulation. These are located in the epicardium and branch inwards to supply the myocardium.
- The left coronary artery divides into two branches: anterior interventricular and circumflex artery.
The right coronary artery divides into two branches: right marginal artery, posterior inter ventricular artery. - Through coronary veins: Venus blood is collected by the cardiac veins, these veins join to form the coronary sinus which empties blood into the right atrium.
Blood pressure=
- Pressure exerted by the blood on the wall of a blood vessel, expressed in mmHg
- Blood pressure is measures with a sphygmomanometer and is important to maintain normal body function.
Systolic pressure=
- The highest pressure and is measured when left ventricle is contracting and expelling blood into the aorta
Diastolic pressure=
- The lowest pressure and is measures when left ventricle is relaxing and blood is flowing into peripheral blood vessels.
Pulse pressure=
- Difference between systolic and diastolic blood pressure and can be felt at the arteries.
e.g., if blood pressure is 120(SBP)/ 80(DBP)mmHg, pulse pressure is= 120-80= 40mmHg
Mean arterial pressure=
- Pressure that propels blood through the tissues. it is equivalent to the DBP + one third of PP.
What determines blood pressure?
- Cardiac output
- Peripheral resistance
- Blood volume
- Blood viscosity
How is blood pressure controlled?
- By blood pressure receptors called baroreceptors
Explain a homeostatic system for low BP=
- Stimulus= low Bp
- Receptor= baroreceptors are inhibited
- Control centre= baroreceptors stimulate cardioacceletory centre
- Effector= Increased heart rate, increased contractility, increased cardiac output. Vasoconstriction happens.
- Response= blood flow returns to homeostatic range
(same for high Bp but a decrease and vasodilation)
What is Marey’s law?
- There is an inverse relationship between Bp and Hr. If Bp is too high, Hr will decrease to compensate.
Franks sterling law of the heart=
- The force of ventricular contraction is determined by length of cardiac muscle fibres
Stroke volume=
- Amount of blood ejected from ventricle during one contraction.
SV= EDV (end diastolic volume) - ESV (end systolic volume)
What is preload and afterload?
- Preload is the degree to which ventricular muscle is stretched before contracting.
- Afterload is the pressure the ventricles must overcome to push blood through semilunar valves as the ventricles are contracting.
What is the Bainbridge reflex?
occurs when the heart rate increases in response to a rise in atrial pressure, e.g., during exercise. This happens to clear the extra blood from the increased atrial filling.
Proprioceptors vs Chemoreceptors=
Proprioceptors= detects increased muscle activity.
Chemoreceptors= detect increase in acidity, heart transfer and respiratory rate.
