Heart Anatomy and Circulatory System Quiz

The heart is a complex muscle that pumps blood
The circulatory system has three divisions
Systemic circulation: heart to body
Pulmonary circulation: heart to lungs
Coronary circulation: within the heart
The heart has three layers
- Epicardium (outer layer)
- Pericardium (surrounds and protects the heart)
- Myocardium (middle layer, bulk of heart wall)
- Endocardium (inner wall)

The heart muscle is asymmetrical
Humans have four chambers
- Two atria: receive blood into the heart
- Two ventricles: pump blood out of the heart
One atrium and one ventricle are on each side
Right atrium receives deoxygenated blood
- Superior vena cava (jugular vein from brain and arms)
- Inferior vena cava (veins from lower organs and legs)
The coronary sinus drains blood from the heart itself

Deoxygenated blood moves to the right ventricle
The right ventricle pumps blood through pulmonary arteries to the lungs for reoxygenation.
Oxygen-rich blood from the lungs enters the left atrium via pulmonary veins.
The left ventricle pumps oxygen-rich blood out through the aorta (major artery) to organs and muscles.

Valves are flaps that open and close to control blood flow direction.
Atrioventricular valves (tricuspid and mitral/bicuspid).
- Right atrium and right ventricle
- Left atrium and left ventricle
Pulmonic valve: right ventricle to the lungs
Aortic semilunar valve: left ventricle to the aorta

Pulmonary (heart and lungs)
Systemic (heart to other body parts)
Coronary (vessels that serve the heart)
The right side of the heart is less thick than the left, to support blood flow to the legs.

Arteries have three layers
- Innermost: tunica intima (squamous epithelium)
- Middle: tunica media (smooth muscle, thickest layer)
- Outermost: tunica externa (connective tissue with elastic and collagenous fibers)
Arteries carry blood away from the heart
- Pulmonary arteries carry deoxygenated blood to the lungs
- Systemic arteries carry oxygenated blood to the body tissues
Arterioles are smaller branches of arteries which regulate blood flow to capillaries

Veins have similar three layers as arteries.
Veins have less smooth muscle and connective tissue, thinner walls, less pressure.
Veins carry blood toward the heart
- Pulmonary veins carry oxygenated blood from the lungs to the heart
- Systemic veins carry deoxygenated blood from body tissues to the heart
Blood flows from capillaries into venules, then progressively larger veins until reaching the heart.

Capillaries are the smallest and most numerous blood vessels.
They form connections between arteries and veins, exchanging materials between blood and tissue cells.
Capillary distribution varies based on tissue's metabolic activity. Active tissues (muscles, liver, kidneys) have extensive capillary networks.

Feature	Arteries	Veins
Location	Closer to the heart	Closer to the skin
Wall structure	Thicker, more elastic	Thinner, less elastic
Size	Larger than veins	Not as large as arteries
Blood flow	Away from the heart	Back to the heart
Blood pressure	Higher	Lower
Type of blood	Oxygen-rich (except pulmonary)	Oxygen-poor (except pulmonary)

The heart's purpose is to pump blood throughout the body
The cardiac cycle has a repeating sequence of filling and emptying the heart
Electrical signals cause heart muscles to contract (systole) to pump blood
Systole is followed by relaxation (diastole), allowing the heart to fill with blood
Blood pressure is measured using systolic and diastolic readings (e.g., 120/80).

Heart muscle contraction is stimulated by depolarization (reducing negative charge)
The heart has specialized "self-excitable" muscle cells (autorhythmic fibers)
Sinoatrial node (SA node) in the right atrium serves as a pacemaker, generating electrical impulses
Electrical impulses spread through atria and ventricles, causing them to contract to pump blood.
Electrocardiogram (ECG) measures electrical activity of the heart

Blood is a connective tissue with a fluid matrix
Blood has cells and other elements
It transports essential components for cellular metabolism, including oxygen (carried by red blood cells)
Blood regulates temperature and hormones
Blood protects against injury, microbes, and toxins via leukocytes, white blood cells

Plasma: the fluid matrix (about 55%) with proteins, ions, nutrients, wastes, gases
Red blood cells/Erythrocytes: transport oxygen via haemoglobin
White blood cells/Leukocytes: less than 1%, larger than red blood cells, with nuclei, essential for immune defense
Platelets: cell fragments involved in blood clotting.

Less than 1% of blood cells are white blood cells (larger than red blood cells and have nuclei).
White blood cells migrate across capillaries into interstitial fluid
Granular leukocytes (neutrophils, eosinophils, basophils).
Agranular leukocytes (lymphocytes, monocytes).
Granules in the cytoplasm contain lysozyme, defensins, and antioxidants.

Blood cell formation begins in bone marrow.
Stem cells (pluripotent) give rise to the various types of blood cells.
Erythropoietin, produced by the kidneys, stimulates erythrocyte production in response to low oxygen levels (erythropoiesis).
Liver produces erythrocyte during embryonic development
Lymphocyte proliferation is a result of antigen encounters and binding to cell receptors.

Hematopoietic stem cells (HSCs) continuously differentiate into various types of blood cells (e.g. lymphocytes).
HSCs give rise to lymphocytes (T-cells, B-cells, natural killer cells) for immune defense.
MSCs contribute to tissue repair at injury sites through differentiation and paracrine signaling.