The Cardiovascular System (heart)

Question 1

Describe the location of the heart and its shape

Answer 1

Rests of the superior surface of the diaphragm, anterior to vertebral column and posterior to the sternum in the mediastinum
Positioned between the second rib and fifth intercostal space and 2/3 of its mass lies to the left of the midsternal line
The posterior surface is flat, directed towards the right shoulder and called the base
The apex is directed anteriorly, inferiorly and to the left
The Hart has four borders (upper, lower, right and left) and three surfaces, anterior (sternocostal), inferior (diaphragmatic) and left.

Question 2

Describe the structure and function of the pericardium

Answer 2

A doubled layered sac
Outer part called fibrous pericardium made up of tough, dense connective tissue which prevents stretching and provides protection. Also anchors the heart to the mediastinum
Inner part called serous pericardium made up of two layers
The parietal layer which lines the fibrous pericardium day the serous layer (epicardium) which is attached tightly to the heart
The space between the fibrous and serous pericardium is called the pericardial cavity and contains a few ml of pericardial fluid

Question 3

What are the three layers of the hear wall?

Answer 3

The epicardium (outer)
The myocardium (middle)
The endocardium (inner)

Question 4

Describe the structure and function of the epicardium (outer layer)

Answer 4

Thin and transparent, so as the visceral layer of pericardium
Composed of mesothelium (single layer of flattened cells forming a epithelium that lines the serous cavities) and delicate connective tissue

Question 5

Describe the myocardium object function

Answer 5

The myocardium is composed mainly of cardiac muscle form the bulk of the heart.
The cardiac muscle is involuntary striated muscle is responsible for the pumping action of the heart

Question 6

Describe the structure of the endocardium (inner layer)

Answer 6

Composed of a single layer of squamous epithelial cells overlying a few layers of connective tissue
It is continuous with the endothelial linings of the blood vessels that enter and leave the heart

Question 7

Describe the anterior surface of the atria

Answer 7

On the anterior surface there Is a wrinkle pouch like structure called an auricle. The auricle is to slightly increase the capacity of the atrium to hold a greater volume of blood

Question 8

Describe the structure and function of sulci

Answer 8

Sulci are the series of grooves on the surface of the heart

They contain coronary blood vessels and some fat and they mark the external boundaries of the chambers

Question 9

Describe the structure and function of the right atrium

Answer 9

Receives venous blood from the body and ejects it through the right AV opening via the tricuspid valve into the right ventricle
The right atrium forms the right border, part of the upper border and part of the anterior (sternocostal) surface and the base of the heart
The lining of the posterior wall is smooth while the anterior wall (auricle) is rough due to the presence of parallel muscular ridges called pectinate muscles

Question 10

Describe the vasculature of the right atrium

Answer 10

The veins that ope into the right atrium are
The superior and inferior vena cava
Coronary sinus (a short venous trunk receiving most of the cardiac veins
The anterior cardiac veins (drain the blood from the anterior wall of the right ventricle)
The venue cordis minimi (numerous small valveless venous channels that open directly into the chambers of the heart from the capillary bed in the cardiac wall)

Question 11

What is the Fossa ovalis

Answer 11

An oval depression in the interatrial septum marking the remnants of the forme ovale (the opening between the atria during the fetal life that normally closes soon after birth)

Question 12

Describe the structure and function of the right ventricle

Answer 12

Receives the blood from the RA and ejects it through the semilunr valve to the pulmonary trunk and then to the lungs for gas exchange
Forms the inferior border + a large part of the anterior (sternocostal) surface and a small part of the inferior (diaphragmatic) surface of the heart .
Inside the RV there are many ridges called trabaculae carneaewhich are formed by raised bundles of cardiac muscle fibers
The cusps of the tricuspid valve are connected to chords called chordate tendineae which in turn are connected to the wall by cone shaped trabeculae carneae called papillary muscles.

Question 13

Describe the structure and function of the left atrium

Answer 13

Forms the left 2/3 of the base, a major part of the upper border and part of the anterior and left surfaces and the left border of the heart
Oxygenated blood from the lungs enter via 4 pulmonary veins and is ejected to the LV though the LAV opening through the bicuspid valve

Question 14

Describe the structure and function of the left ventricle

Answer 14

Receives oxygenated blood from the left atrium and pumps it to the aorta through the semilunar aortic valve
Forms the apex, part of the anterior surface, most of the left border and the left surface and the left 2/3 of the inferior surface of the heart
Like the RV it also contains trabeculae carneae and has chordae tendineae that connect the papillary muscles to the bicuspid valve
The partition between the RV and LV is called the inteventricular septum

Question 15

What is the function of the tricuspid valve ?

Answer 15

Regulates blood flow between the right atrium and right ventricle it is an AVvalve of three leaflet like cusps

Question 16

What is the function of the pulmonary valve

Answer 16

Controls blood flow from the right ventricle into the pulmonary trunk, which carries blood to the lungs to pick up oxyge. It is a semi lunar valve consisting of 3 crescent-shaped cusps

Question 17

What is the function of the bicuspid valve?

Answer 17

Let’s o2 rich blood from the lungs pass from the LA into the LV. It is an AV valve of two leaflet like cusps

Question 18

What is the function of the aortic valve?

Answer 18

Opens the way for O2 rich blood to pass from the LV into the aorta where it is delivered to the rest of our body. It is a semilunar valve consisting of three crescent shaped cusps

Question 19

What is the difference between pulmonary and systemic circulation during which does hart receive oxygen and nutrients?

Answer 19

Systemic circulation supplies O2 and nourishment to all of the tissue in the body
Pulmonary circulation is the movement of blood from the heart to the lungs and back to the heart again

The heart itself receives its oxygen and nutrients from the systemic circulation via a network of blood vessels called the coronary circulation

Question 20

Which vessels does the left coronary artery give rise to

Answer 20

The left anterior descending coronary branch (the anterior inter-ventricular branch) which supplies the wall of both ventricles

The left circumflex branch which supplies the wall of the left ventricle and left atrium

Question 21

Which vessels does the right coronary artery give rise to

Answer 21

The posterior interventricular branch which supplies the wall of both ventricles

The right marginal branch which supplies the right ventricle

Question 22

What are the four coronary veins and where are they found?

Answer 22

Great cardiac vein in the anterior interventricular sulcus
Middle cardiac vein in the posterior interventricular sulcus
Small cardiac vein in the coronary sulcus
Anterior cardiac veins which open directly into the right atrium

The first three open into a large sinus in the coronary sulcus of the posterior surface of the heart called the coronary sinus
The coronary sinus opens into the right atrium

Question 23

What are the five parts of the conducting system?

Answer 23

The sinoatrial node (SA node)
The Atrioventricular node (AV node)
The Atrioventricular bundle (bundle of his)
The left and right bundle branches 
The purkinje fibers

Question 24

Briefly describe how the Heart conducts

Answer 24

Impulse generated by SA node at a rate of 100bpm
Impulse travels through the atrium, causing them to contract, to the AV node
Impulse generated at AV node and travels down the bundle of his
The bundle of his splits into the left and right bundle branches
The bundle branches then split into the Perkinje fibers
This causes the ventricles to contrast

Question 25

What are the three plates of the cardiac cycle

Answer 25

``` Isovolumetric relaxation (early diastole) Ventricular filling (mid to late diastole) Ventricular systole ```

Question 26

What happens in isovolumetric relaxation (early diastole)

Answer 26

When this starts the AV vale’s are closed and the ventricles start to relax causing a drop in pressure Blood flows back towards the ventricles from the aorta and the pulmonary trunk , closing the semi lunar valves At this stage all the valves are closed and there is no change in the volume of blood in the ventricles this is isovolumetric relaxation Relaxation of the ventricles causes a quick drop in ventricular pressure causing the AV valves to open and ventricular filling starts

Question 27

What happens in ventricular filling

Answer 27

Blood from atrium to ventricles Major part of the ventricular filling takes place just after the AV valves open First third of ventricular filling is rapid and is called the rapid ventricular filling Isovolumetric relaxation and rapid ventricular filling all happen while all four chambers of the heart are in diastole This period is called the relaxation period and lasts 0.4 sec The last third of ventricular filling occurs when the atria contract and lasts only 0.1sec during this only 20-25ml of blood are moved At the end of filling each ventricle contains around 130ml of blood which is called end diastolic volume

Question 28

What happens in ventricular systole

Answer 28

Lasts 0.3sec and is when the atria relax and the ventricles contract When ventricular systole starts the blood is pushed backwards causing a closure of the AV valves At this stage all four valves are closed for 0.05sec which is called isovolumetric contraction As pressure in the ventricles increases the semilunar valves open and blood is ejected into the aorta and pulmonary trunk The pressure rises to about 120mmHg in the LV and around 30mmHg in the RV The amount of blood left in each ventricle after systole is called end systolic volume (ESV) which at rest is around 60