Heart Anatomy
Heart Anatomy
Objectives
· Describe the gross external properties of the heart, including location, size and shape
· List the layers of tissue that comprise the wall of the heart and the pericardium
· Identify the internal structure of the heart and the arrangement of the four chambers
· Identify the four heart valves, describing the function of each
· Identify the great vessels of the heart and describe their relationship to the chambers they serve
· Describe the differences between the pulmonary circuit and the systemic circuit
· Trace the pathway of blood through the pulmonary circuit and systemic circuit
· Identify the vessels of coronary circulation
Introduction
In the previous lab, you learned about the basic organization of the circulatory system, focusing on the fluid tissue of that system known as blood. In this lab, we narrow our focus to the muscular pump of the system, the heart. We will also look at the vessels that deliver blood directly into or carry blood immediately out of the heart. When studying only the heart and blood vessels it is common to refer to them as the cardiovascular system. While many might use the terms circulatory system and cardiovascular system interchangeably, we want you to be more accurate in differentiating between the two. It would be correct to say that the circulatory system consists of the blood and the cardiovascular system (heart and vessels) that moves and distributes the blood throughout the body.
In the cardiovascular system, there are two major categories of large vessels: arteries and veins. Generally, arteries transport freshly oxygenated blood from the heart to the body’s tissues and veins transport deoxygenated blood from those tissues back to the heart. The exceptions to the pattern are the vessels of the pulmonary circuit (the pulmonary arteries and pulmonary veins).
In a later lab you will learn about more types of vessels than these, but for now, know that these are the major types.
Location, Size, and Shape of the Heart
[Section 19.1.1: Location of the Heart]
[Section 19.1.2: Shape and Size of the Heart]
[Figure 19.2: Position of the Heart in the Thorax]
Ventral body cavity, thoracic cavity, mediastinum.
Inferior mediastinum contains pericardial cavity.
Base, apex, cardiac notch.
Be sure you know the dimensions of the heart (in cm) and its mass (in grams); and describe the differences in these values between males and females
Layers of the Heart
[Figure 19.5: Pericardial Membranes and Layers of the Heart Wall]
[Figure 19.8: Differences in Ventricular Muscle Thickness]
The pericardium is the serous membrane of the heart
· Two layers (parietal and visceral)
o Outer parietal
§ attaches heart to mediastinum
§ has fibrous tissue so heart doesn’t over-expand
o Inner visceral layer (epicardium)
§ lines surface of the heart
· Space between= pericardial cavity
o Filled with serous fluid (reduces friction)
· Both layers have mesothelium which produces serous fluid
The heart wall has 3 layers
· Epicardium
o same as visceral pericardium
· Myocardium
o most of heart wall, composed of cardiac muscle tissue (which is made of uninucleated cardiac muscle cells)
· Endocardium
o thin layer of endothelial tissue that lines the heart chambers
Internal Structure of the Heart
[Section 19.1.5: Internal Structure of the Heart]
[Figure 19.9: Internal Structures of the Heart]
[Figure 19.11: Chordae Tendineae and Papillary Muscles]
[Figure 19.13: Blood Flow from the Left Atrium to the Left Ventricle]
[Figure 19.14: Blood Flow from the Left Ventricle into the Great Vessels]
Septa
· Interatrial septum, fossa ovalis, interventricular septum
Right Atrium
· Coronary sinus, pectinate muscles
Right Ventricle
· Papillary muscles, chordae tendineae, trabeculae carneae
Left Atrium
Left Ventricle
Valves
· Right AV (tricuspid), pulmonary semilunar valve, left AV (bicuspid or mitral), aortic semilunar valve
Circulation Through the Heart
[Section 19.1.3: Chambers and Circulation through the Heart]
[Figure 19.4: Dual System of the Human Blood Circulation]
Blood enters the right atrium by way of the superior vena cava & the inferior vena cava
From the right atrium, the blood flows through the tricuspid AV valve into the right ventricle.
After the ventricle contracts, the blood flows through the pulmonary semilunar valve and into the pulmonary arteries.
The pulmonary arteries deliver the blood to the lungs where it is enriched and exits by the pulmonary veins.
The oxygenated blood is delivered to the left atrium, where it then is pushed through the bicuspid (or mitral) AV valve into the left ventricle.
From here the blood is pushed through the systemic semilunar valve, and the aorta and then out into the body.
Coronary Circulation
[Section 19.1.6: Coronary Circulation]
[Figure 19.15: Coronary Circulation]
Arteries supply the myocardium with nutrients and oxygen
· Left coronary artery, circumflex artery, anterior interventricular artery (aka, LAD)
· Right coronary artery, marginal arteries, posterior interventricular artery (aka, PDA)
Veins remove waste and metabolic by-products from the myocardium
· Great cardiac vein, small cardiac vein, middle cardiac vein, posterior cardiac vein
· Coronary sinus (all coronary veins merge into this)
o Located in posterior region of coronary sulcus
o Empties deoxygenated blood from myocardium into right atrium
Heart Dissection
Follow your TA to the lab where you will find a dissection guide. Follow the instructions on the guide to dissect a sheep heart. Identify all structures studied above. Notice the dimensions of the sheep heart. What are the differences between this hear and the dimensions of your heart as described in your text?