Chapter 18 - The Cardiovascular System:Heart

Trace the pathway of blood through the heart.

(Left side of the heart is the systemic circuit pump and the right side of the heart is the pulmonary circuit pump) • superior vena cava, inferior vena cava, right atrium, tricuspid valve, right ventricle, pulmonary artery, lung capillaries, pulmonary vein, left atrium, mitral valve, left ventricle, aorta

Endocardium

(inside the heart), is a glistening white sheet of endothelium (squamous epithelium) resting on a thin connective tissue layer

Tricuspid AV valve

(right AV valve), between the right atrium and the right ventricle, has three flexible cusps, prevents backflow of blood into the right atrium

Foramen ovale

- is a small hole located in the atrial septum that is used during fetal circulation to speed up the travel of blood through the heart

End systolic volume

- is the volume of blood in a ventricle at the end of contraction, or systole, and the beginning of filling, or diastole. ESV is the lowest volume of blood in the ventricle at any point in the cardiac cycle

Pericardium

a double walled sac where the heart is enclosed

Superior vena cava

a large vein carrying deoxygenated blood into the heart, carrying blood from the head, arms, and upper body

Inferior vena cava

a large vein carrying deoxygenated blood into the heart, carrying blood from the lower body

Coronary sinus

a wide venous channel that receives blood from the coronary veins and empties into the right atrium of the heart

Trabeculae carneae

irregular ridges of muscles that mark the internal walls of the ventricular chambers, project from the inner surface of the right and left ventricles of the heart

Mitral AV valve

is a dual-flap with two cusps, the mitral valve lies between the left atrium and the left ventricle

Atrioventricular (AV) node

is a part of the electrical control system of the heart that coordinates the top of the heart, it electrically connects atrial and ventricular chambers

Isovolumetric contraction phase

is a term used in cardiac physiology to refer to an event occurring in early systole, during which the ventricles contract with no corresponding volume change. This short-lasting event takes place when both the AV valve and SL valve are closed.

End diastolic volume

is the volume of blood in the right and/or left ventricle at end load or filling in (diastole) or the amount of blood in the ventricles just before systole.

Left ventricle

located at the bottom left portion of the heart below the left atrium, separated by the mitral valve, the thickest of all the chambers, the left ventricle pumps oxygenated blood to tissues all over the body

Right Ventricle

located in the lower right portion of the heart below the right atrium, the heart chamber responsible for pumping deoxygenated blood to the lungs

Myocardium

middle layer, composed of mainly cardiac muscle and forms the bulk of the heart

Papillary muscles

muscles located in the ventricles of the heart, attach to the cusps of the atrioventricular valves (mitral/tricuspid valves) via the chordae tendineae and contract to prevent inversion or prolapse of the valves on systole

Right atrium

one of the four chambers, blood enters to the heart through the two atriums, deoxygenated blood inter the right atrium through the inferior and superior vena cavas

Left atrium

one of the four chambers, found on the upper right hand side of the heart, oxygen-rich blood enters the left atrium from the pulmonary veins; the left atrium then pumps this blood directly into the left ventricle

Epicardium

one of the layers of the heart, the superficial (outside) layer, the visceral layer of the serous pericardium, often infiltrated with fat

Aortic semilunar valve

one of the two semilunar valves

Interventricular septum

separates the ventricles

Intrinsic cardiac conduction system

sets the basic rhythm of the beating heart. It consists of autorhythmic cardiac cells that initiate and distribute impulses (action potentials) throughout the heart

Chordae tendineae

strong, fibrous strings attaches to the cusps of the heart on the ventricular side, these strings originate from small mounds of muscles tissue, the papillary muscles, which project inward from the walls of the ventricles

Sinoatrial (SA) node

the impulse-generating (pacemaker) tissue located in the right atrium of the heart and the generator of normal sinus rhythm

Systemic circuit

the left side of the heart receives the oxygenated blood returning from the lungs and pumps this blood throughout the body to supply oxygen and nutrients to body tissues, the blood vessel that carry blood to and from all body tissues

Aorta

the left ventricle ejects blood into the aorta, the largest artery in the body

Mediastinum

the medial cavity of the thorax, a membranous partition between two body cavities or two parts of an organ, especially that between the lungs

Systole

the phase of the heartbeat when the heart muscle contracts and pumps blood from the chambers into the arteries

Distole

the phase of the heartbeat when the heart muscle relaxes and allows the chambers to fill with blood

Pulmonary circuit

the right side of the heart receives oxygen-poor blood from body tissues and then pumps this blood to the lungs, the blood vessels that carry blood to and from the lungs to pick up oxygen and dispel carbon dioxide

Pulmonary semilunar valve

the semilunar valve of the heart that lies between the right ventricle and the pulmonary artery and has three cusps

Pulmonary trunk

where the right ventricle pumps blood to and routes blood to the lungs were gas exchange occurs

Name the heart valves and describe their location and function.

• Atrioventricular (AV) Valve - one is located at each atrial-ventricular junction to prevent backflow into the atria when the ventricle contracts • The right AV valve (the tricuspid valve) has three flexible cusps (flaps of endocardium reinforced by connective tissue cores) • The left AV valve, with two cusps (mitral valve) • Attached to each AV valve are tiny white collagen cords called chordae tendineae, which anchors the cusps to the papillary muscles protruding from the ventricular walls • The Aortic and pulmonary (Semilunar (SL) Valve) guards the bases of the large arteries issuing from the ventricles and prevent the backflow into the associated ventricles • Each SL valves is fashioned from three pocket like cusps each shaped roughly like a crescent moon • The SL valves open and close in response to differences in pressure • When the ventricles contract and interventricular pressure rises above the pressure in the aorta and pulmonary trunk, the SL valves are forced open and their cusps flatten against the arterial walls as blood rushes past them

Describe normal heart sounds

• Lub-dub • The first sound occurs as the AV closes, the first sound tends to be louder, longer and more resonant than the second • The second sound occurs as the SL valve snaps shut at the beginning of ventricular relation (diastole) resulting in a short sharp sound

Name the individual waves of a normal electrocardiogram tracing, and indicate what each represents.

• P wave - the smallest, lasts about 0.08 s, results from movement of the depolarization wave from the SA node through the atria • QRS complex - results from ventricular depolarization and precedes ventricular contraction • T wave - cause by the ventricular repolarization, typically last about 0.16s.

Describe how the fetal heart differs from the adult heart.

• The fetal heart has an opening in the atrial septum which is a communicating channel between the systemic and the pulmonary circulation. It is known as the foramen ovale. • As the baby's respiratory system is not functional in utero, the baby receives its oxygen from the mother. This opening helps in diverting blood from the right atrium to the left atrium which in turn pumps it to the whole body. • This opening closes in the adult and is known as fossa ovale, as the lungs are functioning after birth this shunt is not required and pulmonary and systemic circulations function separately now.

Describe the structure and functions of the four heart chambers. Name each chamber and provide the name and general route (circuit)of its associated great vessel(s).

• The heart has four chambers: two superior atria and two inferior ventricles • Right atrium, left atrium and right ventricle, left ventricle Atria: The Receiving Chambers • Right atrium has two basic parts: a smooth-walled posterior part and an anterior portion in which bundles of muscles tissue form ridges in the walls; these muscle bundles are called pectinate muscles • The posterior and anterior regions of the right atrium are separated by a C-shaped ridge called the crista terminalis • The left atrium is mostly smooth muscle and pectinate muscles are found only in the auricle • Blood enters the right atrium via three veins • The superior vena cava returns blood from body regions superior to the diaphragm • The interior vena cava returns blood from body areas below the diaphragm • The coronary sinus collects blood draining from the myocardium Ventricles: The Discharging Chambers • Ventricles make up the most of the volume of the heart • Irregular ridges of muscles called trabeculae carneae mark the internal walls of the ventricular chambers • Other muscles like the papillary muscles play a role in valve function and project into the ventricular cavity • Their walls are more massive than atrial walls • When the ventricles contract, they pump blood into the pulmonary trunk, which route the blood to the lungs where gas exchange occurs • The left ventricle is ejects blood into the aorta, the largest artery in the body • Left ventricle is the major muscle that pumps blood out

Describe the timing and events of the cardiac cycle.

• The heart undergos some dramatic writhing movement as it alternately contracts, forcing blood out of its chambers and the relaxes allowing its chambers to be filled with blood • Systole - refers to the these periods of contraction • Diastole - refers to relaxation Cardiac cycle includes all events associated with the blood flow through the heart during one complete heart - atrial systole and diastole followed by the ventricular systole and diastole (1) Ventricular filling: mid-to-late diastole - (2) Ventricular systole (atria in diastole) (3) Isovolumetric Relaxation

Describe the structure and function of each of the three layers of the heart wall.

• The heart wall is composed of three layers: epicardium, myocardium, and endocardium. • Epicardium - the superficial layer, the visceral layer of the serous pericardium, often infiltrated with fat • Myocardium (muscle heart) - middle layer, composed of mainly cardiac muscle and forms the bulk of the heart • This layer contracts • The branching cardiac muscle cells are tethered to one another by crisscrossing connective tissue fibers and arranged in spiral or circular bundles • There is a cardiac skeleton, that reinforces the myocardium internally and anchors the cardiac muscle fibers • Endocardium - (inside the heart), is a glistening white sheet of endothelium (squamous epithelium) resting on a thin connective tissue layer • the endocardium is continuous with the endothelial linings of the blood vessels leaving and entering the heart