The Heart and Fetal Circulation

Flashcards covering key vocabulary and concepts related to the structure and function of the heart, fetal circulation, and associated systems.

Heart Chambers and Major Vessels: Path through Right Side

Deoxygenated blood returns from the body via the superior and inferior vena cava into the right atrium, passes through the tricuspid valve into the right ventricle, then is pumped through the pulmonary semilunar valve into the pulmonary artery, which leads to the lungs.

Heart Chambers and Major Vessels: Path through Left Side

Oxygenated blood returns from the lungs via the pulmonary veins into the left atrium, passes through the bicuspid (mitral) valve into the left ventricle, then is pumped through the aortic semilunar valve into the aorta, which distributes blood to the entire body.

Heart Sounds: S1 (Lub)

The 'lub' sound (S_1) is caused by the closure of the atrioventricular (AV) valves (tricuspid and bicuspid) at the beginning of ventricular systole, preventing blood backflow into the atria as the ventricles contract.

Heart Sounds: S2 (Dub)

The 'dub' sound (S_2) is caused by the closure of the semilunar valves (pulmonary and aortic) at the beginning of ventricular diastole, preventing blood backflow into the ventricles as they relax and fill.

Cardiac Chamber Internal Features: Right Atrium

Internal features of the right atrium include the pectinate muscles (rough anterior wall), crista terminalis (ridge separating smooth and rough parts), and the fossa ovalis (remnant of the foramen ovale) on the interatrial septum.

Cardiac Chamber Internal Features: Right Ventricle

Internal features of the right ventricle include the trabeculae carneae (irregular ridges), papillary muscles (projecting from walls, attach to chordae tendineae), chordae tendineae (connect papillary muscles to tricuspid valve leaflets), and the moderator band (septomarginal trabecula).

Cardiac Chamber Internal Features: Left Atrium

Internal features of the left atrium include a largely smooth posterior wall, with pectinate muscles found only in the auricle.

Cardiac Chamber Internal Features: Left Ventricle

Internal features of the left ventricle include a significantly thicker muscular wall, trabeculae carneae, and two large papillary muscles connected by chordae tendineae to the bicuspid (mitral) valve leaflets.

Coronary Circulation: Arteries

The heart muscle is supplied by the right coronary artery (branches into right marginal and posterior interventricular arteries) and the left coronary artery (branches into the anterior interventricular/LAD and circumflex arteries, which further gives off a left marginal artery).

Coronary Circulation: Veins

Deoxygenated blood from the heart muscle is collected by cardiac veins: the great cardiac vein, middle cardiac vein, and small cardiac vein. These largely drain into the coronary sinus, which then empties into the right atrium.

Intrinsic Conduction System: Components & Pathway

The intrinsic conduction system pathway is: Sinoatrial (SA) node (pacemaker)
ightarrow Atrioventricular (AV) node
ightarrow Atrioventricular (AV) bundle (Bundle of His)
ightarrow Right and left bundle branches
ightarrow Purkinje fibers. This system ensures coordinated heart contractions.

Fetal Circulation: Key Differences & Shunts

Fetal circulation differs significantly due to non-functional lungs and digestive system. Key shunts include:

• Foramen ovale: Shunts blood from right to left atrium, bypassing lungs.
• Ductus arteriosus: Shunts blood from pulmonary artery to aorta, bypassing lungs.
• Ductus venosus: Shunts oxygenated blood from umbilical vein past the liver to the inferior vena cava.
• Umbilical arteries/vein: Connect fetus to placenta for nutrient/gas exchange.

Post-Natal Remnants of Fetal Structures

After birth, fetal structures close or transform into adult remnants:

• Foramen ovale
  ightarrow Fossa ovalis
• Ductus arteriosus
  ightarrow Ligamentum arteriosum
• Umbilical vein
  ightarrow Ligamentum teres hepatis (round ligament of liver)
• Umbilical arteries
  ightarrow Medial umbilical ligaments
• Ductus venosus
  ightarrow Ligamentum venosum

Cardiovascular System

The system comprising the heart, blood vessels, and blood that is responsible for transportation of nutrients, oxygen, waste products, and hormones.

Pulmonary Circuit

The circuit where the right side of the heart pumps deoxygenated blood to the lungs to become oxygenated before returning to the left side of the heart.

Systemic Circuit

The circuit where the left side of the heart pumps oxygenated blood to the entire body and returns deoxygenated blood to the right side of the heart.

Atrioventricular Valves

Valves that prevent backflow into the atria; include the tricuspid valve (right) and bicuspid (mitral) valve (left).

Semilunar Valves

Valves that prevent backflow into the ventricles; include the pulmonary semilunar valve and aortic semilunar valve.

Systole

The phase of the heart cycle in which the ventricles contract to pump blood out of the heart.

Diastole

The phase of the heart cycle in which the ventricles relax and fill with blood.

Intrinsic Conduction System

The system that initiates and distributes impulses throughout the heart to regulate heartbeats.

Foramen Ovale

A hole that shunts blood from the right atrium to the left atrium in fetal circulation to bypass the non-functioning lungs.

Ductus Arteriosus

A vessel that shunts blood from the left pulmonary artery to the aorta in fetal circulation, which closes to form the ligamentum arteriosum after birth.

Umbilical Vein

The vessel that carries oxygenated blood from the placenta to the fetal heart.

Coronary Circulation

Circulation that supplies blood to the heart muscle itself, allowing for its functioning and nourishment.