Circulatory System: The Heart

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Questions and Answers

Which blood vessel receives blood from the left ventricle and distributes it to the body?

Inferior Vena Cava

Aorta (correct)

Superior Vena Cava

Pulmonary Veins

What is the function of the Sinoatrial (SA) Node?

To distribute oxygen-rich blood to the body

To drain blood from the heart muscles

To pump blood from the heart

To regulate the heartbeat (correct)

During which phase of the cardiac cycle does the atria fill with blood?

Systole

Diastolic pressure

Systolic pressure

Diastole (correct)

What is the normal systolic blood pressure?

120 mm Hg Signup and view all the answers

Which veins bring oxygen-rich blood from the lungs to the left atrium?

Pulmonary Veins Signup and view all the answers

What is the function of the Atrioventricular (AV) Node?

To transmit signals to the ventricles Signup and view all the answers

What is the function of the pericardial fluid?

To eliminate friction when the heart expands and retracts Signup and view all the answers

What is the thickest layer of the heart?

Myocardium Signup and view all the answers

What is the purpose of the fossa ovalis?

To bypass the lungs in a fetus Signup and view all the answers

What is the function of the papillary muscles?

To anchor the valves down Signup and view all the answers

What is the name of the valve between the right atrium and right ventricle?

Tricuspid valve Signup and view all the answers

What is the purpose of the semilunar valves?

To control blood flow out of the heart Signup and view all the answers

What is the name of the large blood vessel that receives blood from the right ventricle?

Pulmonary trunk Signup and view all the answers

What is the name of the layer that faces the pericardial cavity?

Epicardium Signup and view all the answers

What is the purpose of the chordae tendineae?

To anchor the valves down Signup and view all the answers

What is the name of the muscle that helps with contraction in the right atrium?

Pectinate muscle Signup and view all the answers

What is the approximate size of the heart?

The size of a fist Signup and view all the answers

What is the term for the space that holds the heart?

Pericardial cavity Signup and view all the answers

What is the direction of the apex of the heart?

Anteriorly Signup and view all the answers

What is the layer of serous pericardium that attaches to the heart?

Visceral layer Signup and view all the answers

What is the purpose of the pericardial fluid?

To facilitate the heart's pumping action Signup and view all the answers

In which intercostal spaces is the heart located?

Between 2nd and 5th Signup and view all the answers

Study Notes

Location and Structure of the Heart

Located within the mediastinum (inferior), between the 2nd and 5th intercostal spaces
2/3 of its mass lies to the left of the body midline
Size: approximately 12 cm (5 inches) in length, 9 cm (3.5 inches) in width, and 6 cm (2.4 inches) in thickness
Shape: blunt cone, with the apex directed anteriorly and the base directed posteriorly

Pericardium

Fibrous pericardium: dense, irregular connective tissue
Serous pericardium:
- Parietal layer: lines the fibrous pericardium
- Visceral layer (epicardium): covers the heart
Pericardial cavity: filled with pericardial fluid, which reduces friction between the heart and surrounding tissues during contraction and relaxation

Layers of the Heart

Epicardium (visceral layer of serous pericardium):
- Faces the pericardial cavity
- Composed of mesothelium and delicate connective tissue
Myocardium:
- Thickest layer
- Composed of cardiac muscle and blood vessels
- Unique cardiac muscle tissue with branching cardiocytes and intercalated disks
Endocardium:
- Endothelium bound to the myocardium by subendothelial connective tissue
- Contains part of the cardiac conduction system

Heart Chambers

2 Atria:
- Right atrium
- Left atrium
- Separated by the interatrial septum
- Fossa ovalis: a remnant of the foramen ovale in the fetal heart
2 Ventricles:
- Right ventricle
- Left ventricle
- Separated by the interventricular septum
- Papillary muscles: attached to tendon-like structures called chordae tendineae

Heart Valves

2 Atrioventricular (AV) valves:
- Tricuspid valve (right AV): between the right atrium and right ventricle
- Bicuspid valve (mitral or left AV): between the left atrium and left ventricle
2 Semilunar valves:
- Pulmonary valve (right semilunar): between the right ventricle and pulmonary trunk
- Aortic valve (left semilunar): between the left ventricle and aorta

Blood Flow

Blood leaving the heart:
- Pulmonary trunk: receives blood from the right ventricle and sends it to the lungs for oxygenation
- Aorta: receives blood from the left ventricle and distributes it to the body
Blood entering the heart:
- Right atrium: receives blood from the superior and inferior vena cavae and the coronary sinus
- Left atrium: receives blood from the pulmonary veins

Cardiac Conduction System

Specialized cells found within the endocardium
Sinoatrial (SA) node: the "pacemaker" of the heart, responsible for regulating heart contractions
Internodal pathways: send signals to the right and left atria
Atrioventricular (AV) node: relays signals from the SA node to the ventricles
Atrioventricular (AV) bundle or bundle of His: splits into the right and left bundle branches
Purkinje fibers: initiate contraction of the ventricles

Cardiac Cycle

Diastole:
- Heart is at rest
- Atria fill with blood
- AV valves are open, and semilunar valves are closed
Systole:
- Atria contract
- AV valves are open, and semilunar valves are closed
- Ventricles contract
- AV valves are closed, and semilunar valves are open

Blood Pressure

Systolic blood pressure: pressure of blood in the vessels when the heart is contracting
- Normal: 120 mm Hg
- High: > 130 mm Hg
- Low: < 90 mm Hg
Diastolic blood pressure: pressure of blood in the vessels when the heart is at rest
- Normal: 80 mm Hg
- High: > 90 mm Hg

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Description

Learn about the location, size, and shape of the heart in the human body. This quiz covers the heart's position within the mediastinum, thoracic cavity, and its dimensions.