Chapter 20 Flashcards
Heart
Relatively small, roughly the same size as your closed fist. Is about 12 cm (5 in.) long, 9 cm (3.5 in.) wide at its broadest point, and 6 cm (2.5 in.) thick, with an average mass of 250 g (8 oz) in adult females and 300 g (10 oz) in adult males. Rests on the diaphragm, near the midline of the thoracic cavity.
Mediastinum
An anatomical region that extends from the sternum to the vertebral column, from the first rib to the diaphragm, and between the lungs. Where the heart lies.
Apex (of the heart)
Is formed by the tip of the left ventricle (a lower chamber of the heart) and rests on the diaphragm. It is directed anteriorly, inferiorly, and to the left.
Base (of the heart)
Opposite the apex and is its posterior aspect. It is formed by the atria (upper chambers) of the heart, mostly the left atrium.
Anterior surface (of the heart)
Is deep to the sternum and ribs.
Inferior surface (of the heart)
Is the part of the heart between the apex and right surface and rests mostly on the diaphragm.
Right surface (of the heart)
Faces the right lung and extends from the inferior surface to the base.
Left surface (of the heart)
Faces the left lung and extends from the base to the apex.
Pericardium
The membrane that surrounds and protects the heart. It confines the heart to its position in the mediastinum, while allowing sufficient freedom of movement for vigorous and rapid contraction.
What two main parts does the pericardium consist of?
- Fibrous pericardium
- Serous pericardium
Fibrous pericardium
Superficial; is composed of tough, inelastic, dense irregular connective tissue. Prevents overstretching of the heart, provides protection, and anchors the heart in the mediastinum.
Serous pericardium
Deep; a thinner, more delicate membrane that forms a double layer around the heart.
The outer ______ of the serous pericardium is fused to the fibrous pericardium. The inner ______ of the serous pericardium, which is also called the ______, is one of the layers of the heart wall and adheres tightly to the surface of the heart.
Parietal layer; visceral layer; epicardium
Pericardial fluid
A thin film of lubricating serous fluid between the parietal and visceral layers of the serous pericardium. Reduces friction between the layers of the serous pericardium as the heart moves.
What are the three layers that the wall of the heart consists of?
- Epicardium
- Myocardium
- Endocardium
Epicardium
The external layer; imparts a smooth, slippery texture to the outermost surface of the heart. Contains blood vessels, lymphatics, and vessels that supply the myocardium.
What two tissue layers is the epicardium composed of?
- Visceral layer of the serous pericardium: thin, transparent outer layer of the heart wall. Is composed of mesothelium.
- A variable inner layer of delicate fibroelastic tissue and adipose tissue.
Myocardium
The middle layer; is responsible for the pumping action of the heart and is composed of cardiac muscle tissue. Makes up approximately 95% of the heart wall.
Endocardium
The inner layer; is a thin layer of endothelium overlying a thin layer of connective tissue. Provides a smooth lining for the chambers of the heart and covers the valves of the heart. The smooth endothelial lining minimizes the surface friction as blood passes through the heart. Is continuous with the endothelial lining of the large blood vessels attached to the heart.
Atria
The two superior receiving chambers. Receive blood from blood vessels returning blood to the heart, called veins. Have thin walls, so deliver blood under less pressure into the adjacent ventricles.
Ventricles
The two inferior pumping chambers. Eject the blood from the heart into blood vessels called arteries. Have thicker walls, so pump blood under higher pressure over greater distances.
Auricle
Wrinkled pouchlike structure on the anterior surface of each atrium. Slightly increases the capacity of an atrium so that it can hold a greater volume of blood.
Sulci
A series of grooves on the surface of the heart that contain coronary blood vessels and a variable amount of fat. Each sulcus marks the external boundary between two chambers of the heart.
Coronary sulcus
Encircles most of the heart and marks the external boundary between the superior atria and inferior ventricles.
Anterior interventricular sulcus
A shallow groove on the anterior surface of the heart that marks the external boundary between the right and left ventricles on the anterior aspect of the heart.
Posterior interventricular sulcus
Marks the external boundary between the ventricles on the posterior aspect of the heart.
Right atrium
Forms the right surface of the heart and receives blood from three veins: the superior vena cava, inferior vena cava, and coronary sinus. Is about 2–3 mm (0.08–0.12 in.) in average thickness. The inside of the posterior wall of the right atrium is smooth, and the inside of the anterior wall is rough due to the presence of pectinate muscles.
Pectinate muscles
Muscular ridges. Extend into the auricle.
Interatrial septum
Thin partition between the right atrium and left atrium. A prominent feature of this septum is the fossa ovalis.
Fossa ovalis
An oval depression; the remnant of the foramen ovale, an opening in the interatrial septum of the fetal heart that normally closes soon after birth.
Tricuspid valve
AKA right atrioventricular valve; a valve in which blood passes from the right atrium into the right ventricle through. Consists of three cusps (AKA leaflets).
Right ventricle
Is about 4-5 mm (0.16–0.2 in.) in average thickness and forms most of the anterior surface of the heart.
Trabeculae carneae
Series of ridges formed by raised bundles of cardiac muscle fibers. Found inside the right ventricle. Some of the trabeculae carneae convey part of the conduction system of the heart.
Chordae tendineae
Tendon-like cords that the cusps of the tricuspid valve are connected to.
Papillary muscles
Cone-shaped trabeculae carneae that the chordae tendineae are connected to.
Interventricular septum
Partition between the right ventricle and left ventricle.
Pulmonary valve
Where blood passes from the right ventricle into the pulmonary trunk through. The pulmonary trunk is a large artery that divides into right and left pulmonary arteries and carries blood to the lungs.
Left atrium
Is about the same thickness as the right atrium and forms most of the base of the heart. It receives blood from the lungs through four pulmonary veins. The inside of both the posterior wall and anterior wall of the left atrium is smooth.
Bicuspid (mitral) valve
AKA left atrioventricular valve; a valve in which blood passes from the left atrium to the left ventricle through. Consists of two cusps.
Left ventricle
Is the thickest chamber of the heart, averaging 10–15 mm (0.4-0.6 in.), and forms the apex of the heart. Like the right ventricle, the left ventricle contains trabeculae carneae and has chordae tendineae that anchor the cusps of the bicuspid valve to papillary muscles.
Aortic valve
Where blood passes from the left ventricle into the ascending aorta through. From here, blood goes to either the heart wall or travels throughout the body.
Ductus arteriosus
A temporary blood vessel that is present during fetal life that shunts blood from the pulmonary trunk into the aorta. Hence, only a small amount of blood enters the nonfunctioning fetal lungs.
Ligamentum arteriosum
What the ductus arteriosus becomes after it closes shortly after birth. Connects the arch of the aorta and pulmonary trunk.
What is the difference between the right ventricle and left ventricle?
Right ventricle: has a much smaller workload than the left ventricle, therefore has thinner walls than the left ventricle – it pumps blood a short distance to the lungs at lower pressure, and the resistance to blood flow is small. Additionally, the perimeter of the lumen (space) is crescent-shaped.
Left ventricle: works much harder than the right ventricle to maintain the same rate of blood flow, therefore has thicker walls than the right ventricle – it pumps blood great distances to all other parts of the body at higher pressure, and the resistance to blood flow is larger. Additionally, the perimeter of the lumen (space) is circular.
Fibrous skeleton of the heart
Dense connective tissue in the heart wall. Consists of four dense connective tissue rings that surround the valves of the heart, fuse with one another, and merge with the interventricular septum. Prevents overstretching of the valves as blood passes through them. It also serves as a point of insertion for bundles of cardiac muscle fibers and acts as an electrical insulator between the atria and ventricles.
Atrioventricular (AV) valves
The tricuspid and bicuspid valves. Located between the atrium and ventricle. When open, the cusps project down into the ventricle. When closed, cusps project upward toward the atria. Prevent the backflow of blood.
Semilunar (SL) valves
The aortic and pulmonary valves. Made up of three crescent moon-shaped cusps. Allow ejection of blood from the heart into arteries but prevent backflow of blood into the ventricles.
There are no valves guarding the junctions between the ______ and the ______ or the ______ and the ______. As the atria contract, a small amount of blood does flow backward from the atria into these vessels. However, backflow is minimized by a different mechanism; as the atrial muscle contracts, it compresses and nearly collapses the weak walls of the venous entry points.
Venae cavae; right atrium; pulmonary veins; left atrium