Chapter-12, The Cardiovascular System-1

What are the two major "Circulations" of the body?

Coronary circulation from Arteries and Veins.

Describe the heart and its position in the body.

The heart is located directly on top of the diaphragm behind the sternum. It is positioned in the middle mediastinum, between the left and right lungs. It is roughly cone-shaped with a broad base and a blunt apex. It lies obliquely, the apex pointing forwards and to the left, close to the 5th intercostal space and the base pointing backwards and to the right. Between the base and the apex the heart measures approximately 12 cm; it is approximately 9 cm across its widest diameter and 6 cm from front to back. The heart weighs approximately 300g in the male and 250g in the female

What information is in an electrocardiogram?

Electrocardiogram (ECG) is a graph of the pattern of beating of the heart, recorded using an equipment called electrocardiograph. Doctors ECG to detect heart damage or disturbances of the heart rhythm. The Instrument records the activity of the heart muscles and converts them in the form of a graph over a time period. several pens incorporated in the the instrument make marks on a moving strip of paper as the activity of different heart muscles cause the position of the pens to change. This produces a group of several graph with time represented on the x-axis, and activity of heart muscles on the y-axis.

Name the four chambers of the heart.

Left atrium,left ventricle, right atrium, right ventricleThe chambers are atria and ventricles, and there is a left and right of each. The blood travels from the body into the right atrium and is pumped through the right ventricle to the lungs. Here it exchanges gases and returns to the heart. It enters the left side of the heart and is pumped around the body. The left side of the heart has much further to pump the blood and is therefore larger and more muscular. The two atria and the two ventricles, each having a right and a left half.

What is the myocardium?

Myocardium is the muscular middle layer of the wall of the heart. It is composed of spontaneously contracting cardiac muscle fibers which allow the heart to contract. Heart contraction is an autonomic (involuntary) function of the peripheral nervous system. The myocardium is surrounded by the epicardium (outer layer of the wall of the heart) and the endocardium (inner layer of the heart).

Differentiate between stroke volume and cardiac output.

Stroke volume is how much blood is pumped with each heart beat. Cardiac output is rate of flow generated by the heart, measured by how many liters are pumped each minute. So multiply stroke volume by heart rate to get cardiac output.

Define systole and diastole.

Systole - The time period when the heart is contracting. The period specifically during which the left ventricle of the heart contracts. Diastole - Referring to the time when the heart is in a period of relaxation and dilation.

What is the endocardium?

The endocardium is the inner layer of the heart. It consists of epithelial tissue and connective tissue.This layer is composed of loose connective tissue and simple squamous epithelial tissue. The endocardium regulates the contractions of the heart, aids cardiac development, and may regulate the composition of the blood that feeds the tissues of the heart. • These fibers, also known as subendocardial branches, are located beneath the endocardium, which is the innermost layer of the heart. Purkinje fibers are stretched along heart muscle tissue beginning at the atrioventricular node.

What is the heart's lining called?

The muscular walls of the heart consist of three major "layers." The bulk of the walls is made up of a layer of cardiac muscle and is called the myocardium. The muscle is enclosed on the outside by the epicardium and on the inside by the endocardium. The heart is also covered completely by a protective sac called the pericardium

What is the function of pericardial fluid?

The pericardial fluid in the pericardium serve the same purpose as fluid within the brain membranes or within snivel membranes between the joints: protection. In the case of the heart, it not only acts as a shock absorber, but also as a lubricant to prevent friction with the heart and pericardium, which could result in "friction rubs" and cardiac tamponade, as well as pericarditis.The fluid provides lubercation for the visceral & parital so that they glide smoothly together; friction free movement.

What coverings does the heart have?

The pericardium is a membrane that covers the heart. Peri/o- (Around) -cardi/o- (heart) -ium (tissue).

What structure is the natural "pacemaker' of the heart?

The sinoatrial node is considered the natural pacemaker of the heart. Specialized neurons fire off electrical impulses that make a healthy heart beat between 60-80 beats per minute. These impulses start off an electrical pathway through the heart that makes the heart "beat"--ie, dilate and contract.

Decribe the two layers of the pericardium.

pericardium, two main layers: fibrous and serous. fibrous is tough, outer, protective layer. serous is underlying and composed of two layers: visceral and parietal. the patietal is attached to the fibrous and the visceral (epicardium) to the myocardium (the muscle of the heart). the serous pericardium has a thin layer of fluid between the two layers, which acts as a lubricant to minimise friction during contractions of the heart. inflammation of the pericardium is pericarditis. pericardial tamonade occurs when a fluid e.g. blood gets between the two serous layers and prevents beating

Trace the path and name the structures involved in the conduction system of the heart.

•Sinoatrial node(SA node)- electrical impulses of heart arises form this structure which is situated in the wall of the right atrium. •Internodal atrial pathways - there are three conduction pathways between SA node and AV node. •Atrioventricular node(AV node)- the only conducting tissue between the atria and ventricles and situated at the lower part of septa dividing two atria. •Bundle of His and its branches - takes over the impulses from the AV node and distributes to the ventricular musculature. •Purkinje fibers - Purkinje fibers are the final conductive tissue leading the electrical impulses to the deeper tissues of ventricles. The electrical conduction in the heart can be monitored by use of an electrocardiogram(ECG).

Name and give the location of the four heart valves.

•The tricuspid valve is between the right atrium and right ventricle. •The pulmonary or pulmonic valve is between the right ventricle and the pulmonary artery. •The mitral valve is between the left atrium and left ventricle. •The aortic valve is between the left ventricle and the aorta. Between the right atrium leading into the right ventricle is an atrioventricular valve called the Tricuspid valve. It is named for the three flaps from which it is made. Between the right ventricle and the pulmonary veins is a semilunar valve called the Pulmonary valve. Coming in between the left atrium and the left ventricle is an atrioventricular valve known as the Mitral valve (the shape is similar to the mitres worn by bishops) then in between the left ventricle and the aorta is a semilunar valve called the Aortic valve.

What is angina pectoris?

Angina pectoris is a phrase that comes from Latin and translates as 'tight chest'. People with angina experience pain in the centre of the chest. The chest can feel constricted and tight, but the pain can also be oppressive, as if something is crushing your chest. Pain starts in the centre of the chest behind the breast bone (sternum) or on the left side of the front of the chest. It can spread out to other parts of your body like your arms and stomach

Trace the flow of blood from the superior vena cava to the aorta.

Right Side: Blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium. Blood flows from your right atrium into your right ventricle through the open tricuspid valve. When the ventricles are full, the tricuspid valve shuts. This prevents blood from flowing backward into the atria while the ventricles contract (squeeze). Blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs. Left Side:The pulmonary vein empties oxygen-rich blood, from the lungs into the left atrium. Right Side:Blood flows from your left atrium into your left ventricle through the open mitral valve. When the ventricles are full, the mitral valve shuts. This prevents blood from flowing backward into the atria while the ventricles contract (squeeze). Blood leaves the heart through the aortic valve, into the aorta and to the body. This pattern is repeated, causing blood to flow continuously to the heart, lungs and body.

What are systole and diastole of the heart?

Systole is the contraction phase of the heartbeat. Diastole is the relaxation phase of the heartbeat.

What are the function of the atria and ventricles of the heart?

The atria of the heart receive blood returning to the heart from other areas of the body. •Right Atrium: Receives blood returning to the heart from the superior and inferior venae cavae. The superior vena cava returns de-oxygenated blood from the head, neck, arm and chest regions of the body to the right atrium. The inferior vena cava returns de-oxygenated blood from the lower body regions (legs, back, abdomen and pelvis) to the right atrium. •Left Atrium: Receives blood returning to the heart from the pulmonary veins. The pulmonary veins extend from the left atrium to the lungs and bring oxygen-rich blood back to the heart The ventricles of the heart function to pump blood to the entire body. •Right ventricle: Receives blood from the right atrium and pumps it to the main pulmonary artery. The main pulmonary artery extends from the right ventricle and branches into left and right pulmonary arteries, which extend to the lungs. Here oxygen-poor blood picks up oxygen and is returned to the heart via the pulmonary veins. •Left ventricle: Receives blood from the left atrium and pumps it to the aorta. The aorta carries and distributes oxygen-rich blood to the rest of the body.