Chapter 18- The heart Flashcards
Trunk definition
Large artery
How much does the heart weigh?
250-350 grams
How long is the heart?
About 5 inches
Why is the heart tipped in the body, and where is the apex pointing to?
The heart is tipped in the body so the blood vessels at the top of the heart stay open. Apex (inferior “tip”) is pointed toward the left hip.
What covers the heart? (3)
- Fibrous pericardium
2. Serous pericardium (visceral and parietal)
What is the fibrous pericardium and what does it do?
External portion of the heart. Prevents heart from filling with too much blood, anchors heart in chest cavity, protects the heart
Serous pericardium
Internal portion of the heart covering. Divided into visceral and parietal layers- forms fluid filled sac around the heart. The visceral and parietal layers are separated by a small amount of serous fluid
3 layers of the heart
- Epicardium
- Myocardium
- Endocardium
Epicardium
Outermost layer of the heart. This is the visceral layer of serous pericardium
Myocardium
Middle layer of the heart. Contains cardiac muscle arranged in spiral/circular bundles- the heart needs to be contracting at the same time or blood flow will be impaired. Also forms the cardiac skeleton.
Cardiac skeleton
Dense connective tissue fibers that link muscle cells together. Importance- action potentials (APs) only spread in certain directions, prevents overstretching of the heart walls from repeated filling/emptying
Endocardium
Innermost layer of the heart. Covers internal surfaces of the heart, including valves. It’s continuous with linings of major blood vessels entering/leaving the heart
What two circuits move blood through the body?
- Pulmonary
2. Systemic
Pulmonary circuit
Any of the blood vessels that carry blood to and from the lungs. Includes the pulmonary arteries and the pulmonary veins.
Pulmonary arteries function
Pump oxygen poor blood from the right side of the heart to the lungs
Definition of arteries
Arteries are the blood vessels that pump blood away from the heart
Definition of veins
Veins return blood to the heart
Pulmonary veins function
Pump oxygenated blood from the lungs to the left side of the heart
Systemic circuit
Any of the blood vessels that carry blood to and from the body tissues. Includes the aorta and the inferior and superior vena cava.
Aorta function
Oxygenated blood leaves the heart through the aorta and its branches to body tissues. Part of the systemic circuit
Superior and inferior vena cava function
Oxygen poor blood returns to the heart via the superior vena cava and the inferior vena cava. Part of the systemic circuit.
What side of the heart is systemic?
The left side of the heart is systemic. Oxygenated blood travels through arteries, oxygen poor blood travels through veins
What side of the heart is pulmonic?
Oxygenated blood travels through veins, oxygen poor blood travels through arteries. This is the only place in the body where oxygen poor blood is carried by arteries and oxygenated blood is carried by veins
How is pressure different on each side of the heart?
The right side (pulmonic) is relatively low pressure, only needs to travel a short distance. The left side (systemic) is high pressure, travels longer distances, and involves more friction. Therefore, the walls of the left side of the heart (especially the ventricles) are very thick. The left ventricle contracts with more force than the right
What separates the atria?
Interatrial septum
Right atrium
The right atrium receives oxygen poor blood from the systemic circuit. The blood enters via the superior and inferior vena cava and the coronary sinus
Left atrium
The left atrium receives oxygenated blood from the lungs. Blood enters via the pulmonary veins
Features of the atria (3)
- Pectinate muscle
- Auricles
- Fossa ovalis
Pectinate muscle
Increases contractile force of the atrium without increasing the mass of the heart. More lightweight than typical cardiac muscle tissue
Auricles
Two “ears” sitting on the surface of the heart. Increase the receptive capacity of the atria
Fossa ovalis
Indentation in the left atrium. Marks where the foramen ovale used to be
What separates the ventricles?
Interventricular septum
Right ventricle
Pumps oxygen poor blood to the lungs using the pulmonary trunk
Left ventricle
Pumps oxygenated blood to the rest of the body using the aorta
Features of the ventricles (2)
- Trabeculae carneae
2. Papillary muscle
Trabeculae carneae
Ridges of muscle that assist with proper functioning of heart valves in the ventricles
Papillary muscle
Assist in opening/closing of the heart valves in the ventricles
Heart valves function
Prevent the backward flow of blood through the heart- you never want blood to flow from the ventricle up to the atria
Atrioventricular valves location
These valves divide the atrium from the ventricle on both sides of the heart. The tricuspid valve (right side) has 3 cusps (flaps), and the mitral/bicuspid valve (left side) has 2 cusps
AV valves (2)
- Tricuspid valve
2. Bicuspid (mitral) valve
Features of the AV valves (2)
- Chordae tendinae
2. Papillary muscles
Function of chordae tendinae and papillary muscles in the AV valves
Chordae tendineae- anchor each cusp to papillary muscle in the ventricle walls- important when valves are closed. The papillary muscles take up the slack of chordae tendineae and contracts with the ventricular muscle
Actions of the AV valves when the ventricles are relaxed and not filled with blood (2)
- Blood flows from blood vessels into atria
2. Cusps of valves hang loosely, allow blood to flow from the atria into the ventricle
Actions of the AV valves when the ventricles contract (3)
- Blood is forced upward in ventricle due to compression- valves close so the blood is forced into the blood vessel
- Compressed blood pushes against the valve flaps
- Valve flaps pushed together, blocking off the atrium
Semilunar valves (2)
- Aortic semilunar valve- sits at base of the aorta
2. Pulmonary semilunar valve- sits at the base of the pulmonary trunk
How many cusps do the semilunar valves have?
Each SL valve has 3 cusps. The cusps have a half moon shape, where the valve gets its name
Actions of the SL valves when the ventricles contract (2)
- Intraventricular pressure increases, blood is pushed upward
- SL valves open and push blood from the ventricle and into the blood vessel
Actions of the SL valves when the ventricles relax (2)
- Pressure decreases in the heart, increases in the blood vessels
- Blood flows back toward the heart due to this pressure difference- blood pushes against the cusps of the SL valve, closing the valve to prevent backflow
Blood regurgitation
This is when blood moves backward due to valve dysfunction. Where this occurs depends on which valve isn’t working. Mitral valve regurgitation is common.
Valve stenosis
This is when the heart valve stiffens and doesn’t allow enough blood through. Can be caused by high cholesterol, makes the valve less flexible.
Heart murmur
A normal heartbeat makes a “lub-dub” sound, but with a heart murmur the heart makes a “lub-whoosh-dub” sound. The whoosh sound is the backward flow of blood. This usually isn’t dangerous, but can indicate other potentially dangerous heart conditions.
Types of heart murmurs (2)
There are innocent murmurs, which are usually congenital, and abnormal murmurs. Abnormal murmurs can indicate congenital heart disease in children and acquired heart valve diseases in adults.
Coronary circulation
blood supply that provides heart tissue with nutrients
The left coronary artery splits into: (2)
- Anterior interventricular artery- supplies interventricular septum, anterior walls of ventricles
- Circumflex artery- supplies left atrium, posterior walls of left ventricle
The right coronary artery splits into: (2)
- Right marginal artery- supplies myocardium of lateral portion of the right side of the heart
- Posterior interventricular artery- supplies posterior ventricular walls
Coronary sinus
Coronary veins combine to form the coronary sinus, which empties oxygen poor blood directly into the right atrium. A sinus is an area where multiple blood vessels dump blood