Cardiovascular anatomy

Question 1

Why do physiotherapists need to know about the cardiovascular system? (5)

Answer 1

Cardiovascular conditions (eg. myocardial infarction, heart failure, peripheral vascular disease)
To understand links with the respiratory system and respiratory conditions
For health promotion
To understand physiological signs such as heart rate, pulse and blood pressure.
To understand exercise physiology and exercise testing

Question 2

superior vena cava function

Answer 2

The superior vena cava carries deoxygenated blood from the body (and head) to the right atrium in the right side of the heart.

Question 3

right pulmonary artery function

Answer 3

carries deoxygenated blood from the right ventricle and pulmonary trunk to the lungs for respiratory gas exchange in the pulmonary capillaries.

Question 4

right pulmonary vein function

Answer 4

receive oxygenated blood from the lungs and deliver it to the left atrium of the heart.

Question 5

inferior vena cava function

Answer 5

carries deoxygenated venous blood from the body to the right atrium in the right side of the heart.

Question 6

right ventricle function

Answer 6

pumps deoxygenated blood through the pulmonary semilunar valve into the pulmonary trunk towards the lungs for gaseous exchange in pulmonary capillaries

Question 7

left ventricle function

Answer 7

pumps oxygenated blood into the aorta via the aortic semilunar valve.

Question 8

why are there differences in the thickness of the muscle in the left and right ventricles

Answer 8

The muscular wall of the left ventricle is the thicker than the right ventricle because it is the main pumping chamber in the heart and has to eject blood to the systemic (body) circulation.
The right ventricle needs less muscle as it pumps blood into the pulmonary (lung) circulation which has much lower blood pressure and resistance in its blood vessels.

Question 9

left pulmonary vein function

Answer 9

receive oxygenated blood from the lungs and deliver it to the left atrium in the left side of the heart.

Question 10

left pulmonary artery function

Answer 10

carries deoxygenated blood from the right ventricle and pulmonary trunk to the lungs for gas exchange in the pulmonary capillaries

Question 11

right atrium function

Answer 11

receives deoxygenated venous blood from the inferior and superior vena cava

Question 12

tricuspid / atrioventricular valve location

Answer 12

right side of heart

Question 13

tricuspid / atrioventricular valve function

Answer 13

has 3 cusps which open to allow deoxygenated blood to pass in a forward direction from right atrium to right ventricle. The cusps then close preventing backward movement of blood from ventricle to atrium, known as regurgitation.

Question 14

how can heart valves become damaged and what effects can this have?

Answer 14

Heart valves can be malformed due to congenital heart disease or become damaged due to ageing or disease. This can cause the valve cusps to either fail to completely close or to prolapse into the right atrium during ventricular contraction.

Question 15

Papillary muscle + chordae tendineae function

Answer 15

The papillary muscle extends from parts of the ventricle wall and connects to the chordae tendineae above. These in turn attach to the valve cusps. Both structures help to secure the atrioventricular valve cusps, preventing them from everting into the atrium during ventricular contraction (no backward flow)

Question 16

intraventricular septum function

Answer 16

separates the right and left ventricles to prevent deoxygenated and oxygenated blood from mixing. It also has a part of the heart’s electrical conduction pathway which runs down its length.

Question 17

how can the intraventricular septum become damaged and what effects can this have?

Answer 17

The septum can be breached due to congenital heart disease or following a myocardial infarction (heart attack) which allows mixing of deoxygenated and oxygenated blood or disruption of electrical conduction in the heart

Question 18

Mitral / atrioventricular valve function

Answer 18

a valve with 2 cusps which opens to allow oxygenated blood to pass in a forward direction from the left atrium to the left ventricle

Question 19

left atrium function

Answer 19

receives oxygenated blood from the lungs via the pulmonary veins

Question 20

What are the 3 main functions of the cardiovascular system?

Answer 20

transport, protection & regulation

Question 21

describe transport as a function of the cardiovascular system

Answer 21

Transport of oxygen, nutrients and hormones to all body tissues/cells and removal of carbon dioxide and waste materials, such as lactic acid, from all body tissues and cells. These are transported by the red blood cells and plasma.

Question 22

describe protection as a function of the cardiovascular system

Answer 22

Protection of the body via white blood cells as part of the immune system. Prevention of excessive blood loss via blood platelets which clot the blood

Question 23

describe regulation as a function of the cardiovascular system

Answer 23

Regulation of body temperature, pH and fluid balance as part of homeostasis

Question 24

describe the blood flow through the heart

Answer 24

deoxygenated blood from sup & inf. vena cava and coronary veins » right atrium » right ventricle » pulmonary arteries » lungs (oxygenated) » pulmonary veins » left atrium » left ventricle » aorta systemic arteries » capillary bed » restart cycle

Question 25

name the 3 layers of the heart

Answer 25

epicardium, myocardium, endocardium

Question 26

describe the epicardium layer of the heart

Answer 26

the outer layer composed of a thin layer of connective tissue and adipose tissue

Question 27

describe the myocardium layer of the heart

Answer 27

the middle layer composed of myocardial muscle cells (myocytes). This is the thickest layer forming the bulk of the heart.

Question 28

describe the endocardium layer of the heart

Answer 28

the inner layer composed of endothelial cells which line the chambers of the heart, the heart valves and great vessels.

Question 29

The pericardium is a membrane surrounding the heart and consists of several layers. The outermost is the tough fibrous pericardium composed of dense irregular connective tissue. What are its functions?

Answer 29

1. Protection of the heart from overfilling and over distension with blood. 2. Protection of the heart from surrounding structures. 3. Anchoring of the heart in its position in the mediastinum during movement. The outer fibrous pericardium is formed from connective tissue and creates a sac around the heart attaching at the central tendon of the diaphragm below and tunica externa of the great vessels above.

Question 30

Serous pericardium The serous pericardium lies beneath the outer fibrous pericardium (the outermost sac covering the heart). Can you describe the structure and function of this part of the heart wall?

Answer 30

The delicate serous pericardium lies between the outer fibrous pericardium and the middle layer of the heart wall - the myocardium. The serous pericardium itself consists of a double membrane with a cavity between: 1. The outer parietal pericardium which fuses with the fibrous pericardium 2. The pericardial cavity - a narrow gap containing a few mls of serous pericardial fluid which helps lubrication between heart layers giving friction-free movement during beating of the heart. The serous pericardial cells secrete this fluid. 3. The inner visceral pericardium (also known as the epicardium) which fuses with the myocardial layer.

Question 31

list the components of a myocyte

Answer 31

desmosomes mitochondria nucleus sarcolemma intercalated discs gap junctions

Question 32

what are intercalated discs in myocytes?

Answer 32

These are found at the margin between adjacent myocytes and contain gap junctions and desmosomes.

Question 33

what are desmosomes in myocytes?

Answer 33

Desmosomes are found in intercalated discs - in the gap between adjacent myocytes. These anchor the ends of cardiac myofibrils together so they do not pull apart during myocyte contraction. This gives mechanical strength to the myocytes.

Question 34

what is the function of mitochondria in myocytes?

Answer 34

Cardiac myocytes have more mitochondria than skeletal muscle for ATP and energy production. This helps sustain the demands of ongoing heart contraction, preventing fatigue.

Question 35

how are myocytes different to skeletal muscle cells?

Answer 35

Cardiac myocytes are striated but are shorter and thicker than skeletal muscle cells. They are branched to give mechanical strength and have longer T-tubules which allow greater quantities of calcium ions into the muscle cell to aid contraction.

Question 36

what are gap junctions in myocytes?

Answer 36

large conductance pores permeable to ions & molecules between myocytes they allow the spread of action potential waves across myocytes ensuring contraction is coordinated (syncytium)

Question 37

cardiac myocytes are myogenic. what does this mean?

Answer 37

they spontaneously produce a rhythmic electrical impulse in the form of a Cardiac Action Potential which spreads across the heart initiating contraction of the atria followed by the ventricles

Question 38

what components are involved in the electrical stimulation of the heart?

Answer 38

sino atrial node atrioventricular node bundle of his purkinje fibres

Question 39

describe the structure and function of the sino atrial node

Answer 39

a small area of specialised autorhythmic conduction cells near the top of the right atrium which form the heart's main pacemaker. These cells can spontaneously depolarise as they have an unstable resting potential known as the Pacemaker potential. This creates a cardiac action potential which transmits to neighbouring conduction cells via gap junctions and eventually reaches the Atrioventricular node. The impulse spreads to myocytes causing both atria to contract to eject blood into the ventricles.

Question 40

what is the innate rate of firing from the SA node?

Answer 40

The innate rate of firing of impulses from the SA node is approximately 100 per minute (in the average resting adult) but the influence of the parasympathetic Vagus nerve lowers this to approximately 70 - 80 per minute.

Question 41

describe the structure and function of the atrioventricular node

Answer 41

The atrioventricular node (AV node) is a group of auto rhythmic cells near the floor of the right atrium. It helps coordinate electrical activity of the atria and ventricles, so the upper and lower chambers of the heart do not contract together.

Question 42

why does the atrioventricular node cause a short delay in transmitting the electrical impulse to the bundle of His?

Answer 42

It receives the electrical impulse from the Sinoatrial node but causes a short delay of approximately 0.09 seconds before transmitting it to the Atrioventricular bundle (Bundle of His). This allows the atria to contract, pushing blood into the ventricles, before the electrical impulse transmits to the ventricles This promoted efficient ventricular filling

Question 43

if there's a problem with the SA node what is the role of the atrioventricular node?

Answer 43

The AV node can act as a secondary pacemaker if the Sinoatrial node fails with an innate rate of firing of 40 - 60 per minute.

Question 44

structure and function of the bundle of His

Answer 44

The Bundle of His (Atrioventricular bundle) located at the top of the interventricular septum, receives electrical impulses from the AV node and then divides to transmits it to the right and left Bundle Branches.

Question 45

why is the impulse limited to traveling down the bundle of His only?

Answer 45

Impulses can only pass to the ventricles via this route because the fibrous skeleton of the heart insulates the atria from the ventricles.

Question 46

if there's a problem with the SA & AV nodes what is the role of the bundle of His?

Answer 46

The Bundle branches can self-generate impulses at a slow rate of approximately 20-40 bpm if the SA AV and nodes fail.

Question 47

purkinje fibres structure and function

Answer 47

The large-diameter Purkinje fibres begin at the heart apex. They receive electrical impulses from the left or right branches of the Bundle of His and rapidly transmit them to the ventricular muscle.

Question 48

what is the correct term for abnormal heart rhythms?

Answer 48

arrhythmias

Question 49

how can arrhythmias come about and what effects can they have?

Answer 49

the rate of electrical impulse firing being too fast or slow, a delay in transmission through the conduction pathway or an electrical stimulus coming from somewhere other than the normal conduction pathway. These can affect the normal functioning of the heart, potentially causing heart failure

Question 50

name the 3 main layers of a blood vessel

Answer 50

tunica externa, media and intima

Question 51

describe the tunica externa

Answer 51

the outermost layer of a blood vessel wall and consists mainly of collagen and elastic fibres.

Question 52

what separated the tunica externa & media

Answer 52

an elastic layer, the external elastic membrane or lamina, separating the Tunica Externa and the middle layer - the Tunica media

Question 53

what supplies the blood vessel walls with blood?

Answer 53

A blood vessel wall receives its blood supply via small arteries called the vaso vasorum.

Question 54

describe the tunica media

Answer 54

The Tunica Media is the middle of the 3 layers. It has mainly smooth muscle and elastic tissue but the relative quantities change according to the blood vessel type.

Question 55

how is the smooth muscle arranged in the tunica media and why is this important?

Answer 55

The smooth muscle is arranged in a circumferential fashion and is integral to controlling the diameter of the blood vessel lumen and therefore resistance to blood flow and blood pressure, especially in medium sized arteries and arterioles.

Question 56

why is the elastic tissue of the tunica media important in arteries?

Answer 56

The elastic fibres are important in large arteries as they allow the vessel wall to stretch and then recoil propelling blood from the heart to the smaller arteries.

Question 57

describe the tunica intima

Answer 57

This is the innermost and thinnest layer of the blood vessel and has direct contact with blood. It consists of an endothelium (simple squamous cells) which lines all blood vessels, myocardium and heart valves. The endothelium sits on the basement membrane - a connective tissue layer anchoring the endothelium to the Tunica media. The outermost part is the internal elastic lamina

Question 58

how are endothelium cells specialised for their role in the capillary

Answer 58

These cells are have an influence on permeability of the capillary and can secrete local chemical mediators capable of stimulating smooth muscle action in the Tunica media to cause vasoconstriction (narrowing of the lumen) or vasodilation (widening of the lumen).

Question 59

what is the role of the internal elastic lamina of the tunica intima

Answer 59

has pores allowing diffusion of materials from the intima to media layers.

Question 60

describe the structure of elastic arteries and how it relates to their function

Answer 60

Elastic arteries (conducting arteries) such as the aorta, are the largest arteries and carry oxygenated blood from the left ventricle to the muscular arteries. Pressure reservoirs: they stretch when blood is pumped into them during left ventricular contraction - storing potential energy in their walls. When the ventricles relax the artery walls recoil, propelling blood forwards. Large amounts of elastic fibres in all tunic layers, especially the tunica media, and 2 elastic laminae aid this recoil and ability to withstand such blood pressure. Elastic arteries have the widest lumens of the arterial system.

Question 61

describe the structure of muscular arteries and how it relates to their function

Answer 61

Muscular arteries (distributing arteries) receive oxygenated blood from the elastic, conducting arteries and distribute blood to the limbs and organs via the arterioles. The artery wall is thick compared to the vessel lumen due to large amounts of smooth muscle, and some elastic fibres, in the Tunica media layer. The smooth muscle lies in a circular arrangement, which can contract to narrow the lumen diameter regulating blood flow to the arterioles. This is called vasoconstriction, which raises resistance blood flow and reduces blood flow. They have inner elastic lamina in the Tunica initma but less elastin is needed as these vessels are not under high blood pressure like the larger arteries. The Tunica Externa is thick but has loose connective tissue allowing changes in vessel diameter.

Question 62

describe the structure of arterioles and how it relates to their function

Answer 62

Arterioles are the smallest arteries and receive oxygenated blood from the medium Muscular arteries. They only have 3 very thin layers. The inner endothelium of the Tunica intima is encircled with bands on smooth muscle (1-2 cells thick) of the Tunica media. This contracts to control the diameter of the vessel lumen and the resistance to blood flow to the capillaries. The smooth muscle is always slightly contracted due to stimulation by the vasomotor nerves (from the vasomotor centre) causing some vasoconstriction called vasomotor tone. Local chemicals mediators can also alter the tone of the smooth muscle and hence vessel diameter. At the capillary end of the arteriole more muscle is present forming the pre-capillary sphincter, which regulates blood flow to the capillary bed. The outer Tunica adventitia, when present, is extremely thin.

Question 63

describe the structure of capillaries and how it relates to their function

Answer 63

Capillaries (exchange vessels) are the smallest blood vessels in the body. They receive oxygenated blood via the metarterioles. They deliver oxygen and nutrients to the interstitial fluid and tissues, and receive carbon dioxide and metabolic waste products from the interstitial fluid and tissues. They then collate to deliver deoxygenated blood to the post-capillary venule. Capillaries have a diameter which only allows passage of one red blood cell at a time - promoting optimal exchange of substances. Capillaries only have an endothelium and basement membrane (Tunica intima) - there is no Tunica media or Tunica adventitia. Capillaries function as part of an extensive capillary bed in the micro circulation.

Question 64

describe the structure of venules and how it relates to their function

Answer 64

The smallest veins, called venules, receive deoxygenated blood from the capillaries and then collate to deliver deoxygenated blood to the medium sized veins. They are part of the microcirculation. Those receiving blood from the capillaries are called post-capillary venules. Venules have a diameter of between 8 and 100 um. They have a Tunica adventitia, media and intima but these are very thin - especially near the capillaries where the Tunica initma have loose intercellular junctions allowing exchange of nutrients, waste and white blood cells. Venules further away from the capillaries have smooth muscle in their Tunica media which can alter the diameter of the venule (vasoconstriction) promoting flow of venous blood towards the heart. Venules, like all veins, also act as blood reservoirs by storing blood.

Question 65

describe the structure of medium sized veins and how it relates to their function

Answer 65

Medium sized veins receive deoxygenated blood from the collated venules and deliver it to the large veins. They have a relatively thick Tunica adventitia with loose fibro-elastic connective tissue, with some elastin for structural support. The Tunica media and intima are thinner with mainly collagen fibres and little smooth muscle or elastin. Intermittent one-way valves, formed from thickened endothelium, close to prevent backflow of blood towards the capillaries due to gravity. These are mainly in the limbs. Vaso vasorum (arterial blood supply) and nervi vasorum (neuronal supply) are in all layers.

Question 66

describe the structure of large veins and how it relates to their function

Answer 66

Large veins receive deoxygenated blood from the medium sized veins and deliver it to the right atrium as venous return. They have a similar structure to the medium sized veins with all 3 tunics present, but as with all veins, the Tunica adventitia is the thickest and contains loose collagen, elastic fibres and a few smooth muscle cells. Compressible and distensible: accommodate limb bending and the large volume of venous blood. Veins do not have elastic laminae like arteries because they are not subjected to the same (higher) blood pressure. Deep veins run between skeletal muscles (mainly in lower limbs) and the contraction and relaxation of these muscles aid the movement venous blood towards the heart. Superficial veins run in the subcutaneous tissue but have connections with deep veins via small connecting veins (anastomoses). Vein wall layers are thin but they have a larger, less circular lumens than arteries. Many veins, especially limb veins, have valves formed from folds of Tunica intima projecting into the lumen pointing towards the heart. These can close to prevent backflow of blood away from the heart due to gravity and low blood pressure in veins.

Question 67

describe the passage of bloodflow through the capillary bed

Answer 67

Oxygenated blood from the medium, muscular arteries enter the arterioles. From an arteriole a smaller vessel emerges - metarteriole Where this meets the proximal end of a true capillary, a ring of smooth muscle exists called the precapillary sphincter - monitors and regulates blood flow to the capillary bed. When the smooth muscle of the precapillary sphincter contracts, blood flow ceases or slows. At the distal end of a metarteriole, there is no smooth muscle or sphincter: blood flows freely. This can fast track blood from arteriole to postcapillary venule by-passing the capillaries and is known as a thoroughfare channel.

Question 68

name the 3 types of capillary

Answer 68

continuous, fenestrated & sinusoid

Question 69

describe the structure of continuous capillaries

Answer 69

consists of a Tunica intima made of an endothelial layer and basement membrane. It has very tight junctions (intercellular clefts) between neighbouring endothelial squamous cells

Question 70

describe transport of substances in continuous capillaries

Answer 70

some breaches to the endothelium allowing other molecules such as glucose, gases and leukocytes (white blood cells) to pass water and ions can pass though selective in what is allowed in and out

Question 71

describe the structure of fenestrated capillaries

Answer 71

These capillaries have pores in the plasma membrane of the endothelial cells. The pores can vary in size according to the location of the capillary

Question 72

where can fenestrated capillaries be found?

Answer 72

The small intestine villi - allowing nutrient absorption The kidney - allowing blood filtering Many endocrine sites such as the pituitary gland, thyroid gland and hypothalamus Choroid plexus of the brain ventricles

Question 73

describe the structure of sinusoid capillaries

Answer 73

They are wider and more winding than other capillary types. They have a flattened appearance, endothelial cells with very large intercellular gaps and an incomplete basement membrane.

Question 74

what are transported through sinusoid capillaries?

Answer 74

large plasma proteins and cells

Question 75

where can sinusoid capillaries be found?

Answer 75

liver, bone marrow (allowing red blood cells to pass out to blood) spleen and anterior pituitary glands

Question 76

give an overview on the arrangement of the coronary arteries

Answer 76

arise from the ascending aorta and encircle the heart via 3 main branches. These subdivide to ensure all parts of the heart wall are perfused.

Question 77

what are anastomoses and why are they important?

Answer 77

they are connections between coronary arteries If one artery becomes partially blocked in coronary artery disease, then oxygen can still be deliver by blood flow through other collateral vessels