9.16.11+-+Anatomy+of+the+Heart+and+Pericardium

**1. Describe in general terms the function of the heart.** The function of the heart is to pump blood to each of the body's organs.

**2. Define the divisions, boundaries and contents of the middle mediastinum.** The middle mediastinum contains the heart and the bases of the great blood vessels and is contained within the pericardium.

**3. Define the following terms and describe their significance:**

**Pericardium-** the sac that contains the heart and great blood vessels. It is composed of fibrous and serous pericardium. **Fibrous pericardium-** the outer sac of the pericardium. It's role is to support the heart and to prevent overfilling of the heart. It is innervated by the phrenic nerve.

**Serous pericardium**- the inner sac of the pericardium. It is composed of the parietal pericardium and the visceral pericardium (epicardium). Between these two layers is the pericardial cavity, which holds serous fluid to provide a near-frictionless environment for the heart.

**Transverse pericardial sinus**- on the posterior of the heart, anterior to the SVC but posterior to the aorta and pulmonary trunk.

**Oblique pericardial sinus**- between the IVC and pulmonary veins

**4. Describe the general structure of the heart including its shape, position, grooves,** **apex, base, surfaces, borders, walls and fibrous skeleton.**

**5. Name and describe the four chambers of the heart and their specific features.** Right atrium- the sinus venarum receives the IVC and SVC, receiving blood from the entire body. The crista terminalis separates the sinus venarum and pectinate muscle, which makes up the anterior wall. The fossa ovalis marks the location of the closed foramen ovale.

Right ventricle- the right ventricle receives blood from the right atrium via the tricuspid valve. From here, blood follows the conus arteriosus to the pulmonary trunk. The interior of the ventricle is composed of trabeculae carneae.

Left atrium- the left atrium receives blood from the pulmonary veins. The internal surface is smooth. The medial wall is marked by the fossa ovalis. The left AV valve mediate blood flow into the left ventricle.

<span style="font-family: Times New Roman,serif;">Left ventricle- the left ventricle receives blood from the left atrium and sends it out via the ascending aorta to the rest of the body. It's walls are thick due to systemic blood pressure being higher than pulmonary blood pressure. The internal surface is marked by trabeculae carneae.

<span style="font-family: Times New Roman,serif;">**6. Name and describe AV and semilunar valves of the heart and associated features.** <span style="font-family: Times New Roman,serif;">AV- <span style="font-family: Times New Roman,serif;">Semilunar- these valves cover the pulmonary artery and aorta. The pulmonary valve has 3 cusps (anterior, right and left), while the aortic valve has posterior, left, and right cusps. Each cusp has a sinus connected by a lunule. At the apex of each lunule is a nodule. During relaxation of the heart, the sinuses fill with blood, closing the valves.

<span style="font-family: Times New Roman,serif;">**7. Identify and describe pathways and distribution of the coronary arteries and cardiac** <span style="font-family: Times New Roman,serif;">**veins.** <span style="font-family: Times New Roman,serif;">Coronary arteries provide oxygenated blood to the epicardium and myocardium. The main arteries of the surface of the heart are the right and left coronary arteries. The right coronary artery divides into the anterior right atrial artery, the right marginal branch and the posterior interventricular (aka posterior descending) artery. The left coronary artery divides into the anterior interventricular artery (aka left anterior descending, or LAD, artery) and the circumflex artery. The left marginal artery breaks off from the circumflex artery. <span style="font-family: Times New Roman,serif;">The major coronary veins are the great, middle and small cardiac veins. These all empty into the coronary sinus.

<span style="font-family: Times New Roman,serif;">**8. Describe the conducting system of the heart. Name its component parts and their** <span style="font-family: Times New Roman,serif;">**area of distribution. In general terms, describe how these components work.** <span style="font-family: Times New Roman,serif;">The heart receives innervation at the sinoatrial (SA) and atrioventricular (AV) nodes. The SA node lies at the junction of the SVC and the crista terminalis. From here, signals travel down to the AV node near the coronary sinus, where it branches off into hte AV bundle to the left and right ventricles.

<span style="font-family: Times New Roman,serif;">**9. Describe the pathways of sympathetics and parasympathetics to the heart and effects** <span style="font-family: Times New Roman,serif;">**upon heart rate, impulse conduction, force of contraction and blood supply.**

<span style="font-family: Times New Roman,serif;">Sympathetic route: Presynaptic fibers arise from T1-T5 and synapse in cervical and thoracic ganglia. Postganglionic fibers travel via the cervical and thoracic sympathetic nerves, pass through the cardiac plexus, and innervate the in the SA and AV nodes.

<span style="font-family: Times New Roman,serif;">Sympathetic effect: increases heart rate, impulse conduction, contractile force, and blood flow.

<span style="font-family: Times New Roman,serif;">Parasympathetic route: fibers travel from the brain stem to the vagus nerve. These fibers synapse in the cardiac plexus, SA, and AV nodes.

<span style="font-family: Times New Roman,serif;">Parasympathetic effect: reduces heart rate, contractile force, and blood flow.

<span style="font-family: Times New Roman,serif;">**10. Describe the cardiac cycle, diastole, systole, “lub” and “dup” sounds.**

<span style="font-family: Times New Roman,serif;">During systole, the ventricles contract due to electrical signals, causing a buildup of pressure and an expulsion of blood into the aorta and pulmonary trunk. In diastole, the ventricles relax and take in blood from the atria.

<span style="font-family: Times New Roman,serif;">The lub and dub sounds are from the AV and semilunar valves opening and closing. The lub is from the opening of the semilunar and closing of the AV valves. The dub is from the opening of the AV and closing of the semilunar valves.