Cardiovascular System Flashcards
Which organs make up the cardiovascular system, and what are their functions?
Heart- pumps blood to lungs and rest of body
Arteries- supply oxygenated blood to rest of body
Capillaries- exchange nutrients and gases with tissues
Veins/ lymphatics- drain blood/ fluid from tissues
What is vascular tissue made up of?
Connective tissues (elastin and collagen), epithelial cells and muscle cells (smooth in capillaries, cardiac in heart).
Define the mechanism of the blood vascular system.
A closed supply and drainage system forming a continuous loop.
Define the mechanism of the lymphatic vascular system.
An open-entry, one-way system.
What is the purpose of the lymphatic system?
It accumulates and drains the fluid that escapes from the blood vascular system back to the heart.
Name and define the two circulation pathways within the blood and lymph vascular systems.
Pulmonary circulation- deoxygenated blood is received from the right ventricle and is pumped to the lungs for oxygenation.
Systemic circulation- oxygenated blood is received from the lungs and pumped through the LHS of the heart, out the aorta to the rest of the body.
What function do lymph nodes play in the systemic circuit?
They surveil the lymph fluid for any microbes, venom etc., before it goes back into the blood vascular system.
Where are major arteries found? Why?
They are situated to avoid damage: e.g. deep in the trunk, on flexor aspect of limbs like behind the knee
The blood flowing through arteries is travelling at high velocity and high pressure, so damage to the artery would be life-threatening.
How many arteries supply each structure?
One, unless it is an important structure such as the brain or hand, of which there are two.
Name the three types of capillaries in order of increasing permeability.
Continuous
Fenestrated
Sinusoidal
Name the three pathways for drainage, and their locations.
Deep veins- next to supply artery
Superficial veins- just below dermis
Lymphatics
Why are superficial veins near the surface of the skin?
The blood is flowing at low pressure and low velocity, so damage to the veins would not be life-threatening.
How large are veins in comparison to arteries? Why?
Twice the cross-sectional surface area is needed in order to shift the same volume of blood per second, since the pressure and velocity of blood is lower in veins than arteries.
Describe the shape of the heart.
Blunt and cone-shaped. It has a pointed end (apex) and a broad end (base).
Where is the heart located, and how is it positioned?
In the mediastinum (chest cavity).
The apex is in line with the midclavicular line between the 5th and 6th ribs on the LHS. This is the called the point of maximal impulse (PMI).
The base sits level between the 2nd and 3rd ribs. 2/3rds of the heart is on the LHS of the body.
The heart is rotated so the RHS is facing more anteriorly, and the LHS is facing more posteriorly.
What is the apex beat?
The location where the greatest visual and aural heartbeat can be observed. (At the PMI)
Name the four chambers of the heart, and their functions.
Right atrium- receives deoxygenated blood from the body
Right ventricle- pumps deoxygenated blood to the lungs
Left atrium- receives oxygenated blood from the lungs
Left ventricle- pumps oxygenated blood to the body
Name the two septums of the heart, and their functions.
Interventricular septum- blocks any movement of blood between the left and right ventricles
Interatrial septum- blocks any movements of blood between the left and right atriums
Name the two veins feeding the right atrium, and where they transport blood from.
Superior vena cava- head, neck, chest, upper limbs
Inferior vena cava- below diaphragam
How does venous blood drain from the heart itself?
Through the opening of the coronary sinus into the right atrium.
Through which structures does the left atrium receive its oxygenated blood?
The four pulmonary veins.
Name the three layers of the heart wall.
Endocardium
Myocardium
Epicardium
What is the pericardium?
A lubricated sac which acts as a protective layer around the heart.
What makes up the endocardium?
Endothelium- a thin, delicate layer of squamous epithelium
Loose irregular FCT (supports endothelium)
Blood vessels
Purkinje fibres- modified cardiac muscle cells that carry electrical activity
What prevents blood from clotting up against the heart wall?
The endothelium, because it provides a non-stick surface.
What tissue makes up the myocardium?
Cardiac muscle tissue
How thick is the myocardium layer in the left and right ventricles? Why?
LHS: 0.5cm
RHS: 1.5cm
More cardiac muscle tissue is required in the RHS, because it must pump the same volume of blood to the body that the LHS is pumping just to the lungs.
What makes up the epicardium?
Visceral pericardium
Blood vessels
Loose irregular FCT
Adipose tissue
Name the four components of the pericardium and their locations.
Visceral pericardium- part of epicardium/ envelops the heart
Pericardial cavity- between two layers (filled with fluid)
Parietal pericardium- faces wall of mediastinum
Fibrous pericardium- leathery bag surrounding other layers
Name the types of valves in the heart, and their functions.
Semilunar valves- prevent blood returning to ventricles during filling (diastole)
Atrioventricular (AV) valves- prevent blood returning to atria during ventricular contraction
Name the two AV valves and their positions.
Tricuspid valve- between right atrium and right ventricle
Mitral/ bicuspid valve- between left atrium and left ventricle
Name the two semilunar valves and their positions
Pulmonary valve- between right ventricle and pulmonary arteries
Aortic valve- between left ventricle and aorta
Describe diastole in terms of valves.
The phase where the ventricle is filled with blood. The AV valves are open and the semilunar valves are closed.
Describe systole in terms of valves.
The phase in which the ventricular muscle contracts and exerts pressure on the ventricle. The AV valves are closed and the semilunar valves are open, so blood has to move through the arteries.
Why doesn’t blood fall back into the ventricles?
The semilunar valves close as blood starts to backflow.
How are the AV valve leaflets prevented from slamming up the atrium when the pressure gets too high in the ventricle?
Papillary muscles- fingerlike projections- in the ventricular wall attach the leaflets through chordae tendineae. They develop tension early in systole.
Why don’t semilunar valves need chordae tendineae?
The valve is smaller and the leaflets support each other up.
Name the arteries that supply the heart.
Right coronary artery
Left coronary artery- splits into circumflex artery and anterior interventricular artery
Where does the right coronary artery run?
From the root of the aorta- in the epicardium- down the coronary groove between the right atrium and right ventricle to the posterior aspect of the heart. It branches off and supplies the bulk of the muscle- ventricular chamber.
Where does the anterior interventricular artery run?
From the left coronary artery- in the epicardium- across the anterior of the heart, over the interventricular septum.
Where does the circumflex artery run?
From the left coronary artery- in the epicardium- down the coronary groove between the left atrium and left ventricle to the posterior aspect of the heart.
Name the veins that drain the heart, and which parts they drain.
Great cardiac vein (LHS) and small cardiac vein (RHS).
Where do the cardiac veins run and collect?
Up the coronary grooves to the posterior of the heart, arriving in a big bulging vein called the coronary sinus- into the right atrium.
How does cardiac muscle differ from other types of muscle?
They are striated, unlike smooth muscle. The nucleus (one, occasionally two) is in the centre of the cell, unlike pushed to the periphery in muscle cells.- organelles are at poles of nucleus Consists of short. branched cells, unlike long skeletal fibres.
Why are capillaries in cardiac muscle so narrow?
They are the diameter of one red blood cell to force them to travel in single file. This ensures they are as close to the wall of the capillary as possible, so gas exchange is improved.
Why are there many capillaries in cardiac muscle?
It needs a good blood supply because its metabolism is very oxygen-dependent.
Which organelle takes up 20% volume of a cardiac muscle cell and why?
Mitochondria- because cardiac muscle has a very oxygen-dependent, ATP-driven metabolism.
How are the sarcomeres in cardiac muscle organised and why?
Irregularly (they are also branched), so the force of contraction is spread out
What is the name for a cardiac muscle cell?
Cardiomyocyte
Name the three types of intercalated disks (ICD’s) between cardiomyocytes.
Adhesion belts
Desmosomes
Gap junctions
Describe adhesion belts.
Links the actin filaments of neighbouring cardiomyocytes by transmembranous proteins. This transfers force from the contractile apparatus of one cell to that of the next- creating a physical propagation of force.
Describe desmosomes.
Link the internal cytoskeletons (cytokeratin) of neighbouring cardiomyocytes- keeps cells stuck together.
Describe gap junctions.
Fuses the plasma membranes of neighbouring cardiomyocytes and forms small porous openings. The junction connects cells horizontally (parallel to contractile plane) to avoid force because of its fragility. Allows electrochemical communication.
What is the purpose of the heart’s conduction system?
It greatly increases its pumping efficiency.
Responsible for co-ordination of AV valves and heart contraction.
Which tissue makes up the conduction system of the heart?
Modified cardiac tissue (not nervous).
Describe Purkinje cells.
Cardiac cells that no longer contract- few desmosomes and adhesion belts.
Surrounded by myofibrils.
Filled with mitochondria and glycogen- function is very energy-dependent.
Lots of desmosomes- communicating cells.
Name the branches of the aorta.
Thoracic aorta: Ascending aorta
Aortic arch
Descending aorta
Abdominal aorta, then bifurcates at bellybutton level
Name the arteries between where the aorta bifurcates, and the foot.
Common iliac artery External iliac artery Femoral artery Popliteal artery Posterior tibial artery Plantar arch
Name the deep veins between the foot and the inferior vena cava.
Plantar venous arch Posterior tibial vein Popliteal vein Femoral vein External iliac vein Common iliac vein
What is the great saphenous vein, and where does it run?
Superficial vein (hypodermis)- longest vein in the body Drains the medial aspect of ankle, medial aspect of knee, and groin, then joins femoral vein in the groin.
Name the layers of a blood vessel.
Tunica intima
Tunica media
Tunica adventitia/ externa
What comprises the tunica intima?
Endothelium- thin, squamous epithelium
Sub-endothelium- sparse pad of loose FCT that cushions the endothelium
Internal elastic lamina (IEL)- thin, condensed sheet of elastic tissue (more distinct in arteries than veins)
Why is the tunica media thicker in arteries than veins?
The blood is under higher pressure.
What comprises the tunica adventitia/ externa?
Loose FCT- high collagen content and varying elastin, determines how far the blood vessel can dilate (collagen fibres get taut)
Vasa vasorum- small blood vessels that supply the smooth muscle of large blood vessels (need their own supply)
Lymphatics and autonomic nerves
What comprises the tunica adventitia/ externa?
Loose FCT- high collagen content and varying elastin, determines how far the blood vessel can dilate (collagen fibres get taut)
Vasa vasorum- small blood vessels that supply the smooth muscle of large blood vessels (need their own supply)
Lymphatics- drain any fluid that has left the blood vascular space
Autonomic nerves- control constriction and dilation of the smooth muscle in the media
What is the difference between elastic arteries and muscular arteries?
Elastic arteries are near the heart, and have elastic tissue all through the tunica media because they require a lot of elasticity (during systole) and recoil (during diastole). Because of this abundance in the media, they don’t need connective tissue in the tunica adventitia.
In muscular tissue, most of the tunica media is smooth muscle, with a few connective fibres (most are in the adventitia).
How do elastic arteries dampen the pulsatility of the blood before it gets to the capillaries?
By taking up some of the energy into the elastic tissue of the vessel walls in diastole, then re-exerting it into the lumen during systole.
Why do muscular arteries constrict or relax to change the size of their lumen?
To distribute the blood however necessary, e.g. to leg muscles when working out.
Describe arterioles.
Last vessels of the supply network, feed into capillary beds. Their smooth muscle tone determines blood pressure.
Describe venules.
First vessels of the drainage system, drain capillary beds. Valves ensure low pressure blood travels in the right direction.
Why is the tunica adventitia/ externa the thickest layer of a vein?
Veins are capacitance vessels- they can hold extra blood volume (e.g. if standing for long period). Collagen in the adventitia prevents over-distension of the vein when it’s holding extra blood.