Heart Anatomy

Structures

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What houses the heart is a sac called the parietal pericardium - it reduces friction between the heart and nearby organs because of the lubricating fluid in-between the outer (parietal pericardium) and inner (visceral pericardium) layers of the pericardium itself; this fluid is aliased as pericardial fluid.

The heart wall is outer part of the heart; aliased also as the myocardium. It's separated into three layers: the epicardium (outer layer), thin surface layer; myocardium (middle layer), thickest layer; and the endocardium (inner layer), which lines the heart's interior.

Inside the heart wall, contains four muscular sections that are called the chambers of the heart. They briefly hold blood before transporting it. These chambers are as follows: right atrium, left atrium (upper chambers; plural - atria); and right ventricle, left ventricle (lower chambers; plural - ventricles).

Relating to these chambers, there are openings; flaps called valves (they open and close), located right in-between. In the heart, the valves are as follows: tricuspid valve (located between right atrium and right ventricle), pulmonary valve (located between the right ventricle and the pulmonary artery), mitral valve (located between left atrium and left ventricle), and the aortic valve (located between the left ventricle and the aorta).

Then there's the septum, a wall of tissue, that separates the heart into right and left. (fun fact - the word septum comes from the greek word saeptum, which means 'dividing wall or enclosure').

Being apart of the circulatory system, the heart works with and has blood vessels inside it. In fact, it works with 60,000 miles of blood vessels. So, naturally, only the important ones or 'great' vessels of the heart will be covered. The great vessels (veins and arteries) are as follows: aorta (largest artery in body - connects to the left ventricle of the heart running through the chest diaphragm, and abdomen); pulmonary arteries (runs from the right ventricle to the lungs), pulmonary veins (runs from the lungs to the left atrium); inferior vena cava (located along the right anterolateral aspect of the vertebral column; connects to the posterior inferior right atrium of the heart); superior vena cava (located above and behind the right atrium of the heart).

The supply of oxygen, permitting the heart to beat, is due to the coronary arteries that travels from the base of the aorta as it leaves the right ventricle. There are two main coronary arteries: the right coronary artery (located in right atrioventricular groove, between the right atrium and pulmonary trunk) and the left coronary artery (originates from the ascending aorta just above the left cusp of the aortic valve; it branches into smaller arteries on the left side of the heart that supply blood to the heart muscle). (fun fact - the word 'coronary' comes from the Latin word coronarius, which means 'belonging to a crown or wreath', as the arteries resemble a crown as they encircle the heart).

What causes the pace of the heart, aliased as the pacemaker, is the SA node. (located in the upper-right chamber of the heart at the junction of the superior vena cava and the right atrium).

What causes the beating, or contractions of the heart through electrical impulses is The Bundle of His (BOH), also known as the atrioventricular bundle (located in the interventricular septum, the wall that divides the right and left ventricles of the heart. This structure is essential for the heart's electrical conduction system, serving as a pathway that connects the atria (upper chambers) to the ventricles (lower chambers).

The conduction of electricity, causing the heart to beat fibers are located in the subendocardial surface of the heart's ventricular walls, sending electrical signals to the ventricles, causing them to contract; is the fibers aliased as Purkinje Fibers. The subendocardium is a part of the endocardium, which is the inner layer of tissue that lines the heart's chambers. 

Types of Vessels

  • Capillaries

  • Tiniest blood vessel

Venules

  • Smallest veins

  • Join to form larger veins

Veins

  • Carry blood toward the heart

Blood

Erthrocytes

  • Mature red blood cells produced by red bone marrow

  • Transport oxygen to tissues

  • Hemoglobin

  • Oxygen carrying blood protein pigment

Leukocytes

  • Defends the body against infective organisms and foreign substances

  • Neutrophils: Immune system defense

  • Basophils: Cause symptoms of allergies

  • Eosinophils: Destroy parasitic organisms

  • Lymphocytes: Produce antibodies

  • Monocytes: Immunological defense

Thrombocytes

  • Thrombocytes

  • Smallest formed elements

  • Important role in clotting

Blood Types

  • Classified according to the presence or absence of certain antigens

  • Listed as: A, B, A B, O followed by R h factor

    • R h defines presence or absence of R h antigen on red blood cells

    • Rh antigen present = R h positive

    • R h antigen absent = R h negative

Blood Gases

  • Gases normally dissolved in plasma

  • Major blood gases

  • Oxygen, Carbon dioxide, nitrogen