the heart
The heart is a hollow, cone-shaped, muscular pump which is about the size of a man's fist. (approximately weighing 1 lb) located within the _________ of the thorax that is between the lungs and behind the sternum & resting upon the diaphragm.
mediastinum
The heart is in Oblique Position, two-thirds of it lies to the left of the chest midline. The Apex of the heart is at the __________________. This is where you can find the point of maximal impulse (the loudest heart beat) of a normal adult heart.
left midclavicular line, 5th Intercostal Space.
Covering of the Heart
– tough, white fibrous connective tissue that forms a sac that covers the heart.
Pericardium
3 distinct layers of the heart:
1. Epicardium
2. Myocardium
3. Endocardium
– the outer layer of the heart which serves as a protective layer; consists of connective tissue covered by epithelium, blood &lymph capillaries, nerve fibers, some fat, & coronary arteries & veins
Epicardium
– the middle layer of the heart which is thick & consists of muscle tissue
Myocardium
– the innermost lining of the heart
Endocardium
The heart is divided into four chambers. The four chambers are divided by the _________ which separates the left side and the right side of the heart.
septum
The two upper chambers (the left and the right atria) receive and collect blood.
“receiving chambers”
The two lower chambers (the left and right ventricles) pump the blood out of the heart.
“discharging chambers”
The Heart valves
Each chamber has a valve that allows the blood to flow in and out of the heart.
1. tricuspid valve
2. mitral or bicuspid valve
3. pulmonary semilunar valves
4. aortic semilunar valves
controls the blood flow between the right atrium and the right ventricle.
tricuspid valve
allows oxygen-rich blood from the lungs to pass from the left atrium into the left ventricle.
mitral or bicuspid valve
The valves open as blood is pumped through. These are held in place by fibrous cords known as _____________ (“heart strings”) which is attached to the pappilary muscles projecting from the ventricular wall. These help prevent backflow as the valves close.
chordae tendineae
The valves open as blood is pumped through. These are held in place by fibrous cords known as chordae tendineae (“heart strings”) which is attached to the ___________ projecting from the ventricular wall. These help prevent backflow as the valves close.
pappilary muscles
•The _____________ are in charge of controlling the flow as blood leaves the heart. These semilunar valves do not have any attachment to the chordae tendinae.
pulmonary and aortic semilunar valves
–Receives deoxygenated blood (O2-poor blood) from the body via
•Inferior Vena Cava (carries deoxygenated blood from the lower part of the body to the heart),
•Superior Vena Cava (carries deoxygenated blood from the upper part of the body to the heart),
•Coronary sinus (drains deoxygenated blood from the coronary circulation)
•Right Atrium
–Receives deoxygenated blood (O2-poor blood) from right atrium through tricuspid valve
–Pumps blood to lungs passing the Pulmonary Semilunar Valve into the pulmonary arteries
•The pulmonary arteries are the only arteries that carry deoxygenated blood in the body.
•Right Ventricle
–Receives oxygenated (O2-rich blood) coming from the lungs via the 4 Pulmonary Veins
•The pulmonary veins are the only veins that carry oxygenated blood in the body.
•Left Atrium
–Receives blood from Left Atrium via bicuspid valve
–Pumps blood into the aorta passing the Aortic Semilunar Valve which then distributed to the rest of the body.
•Left Ventricle
Flow of Blood through the Heart
-Blood follows this sequence through the heart:
superior and inferior vena cava → right atrium → tricuspid valve → right ventricle → pulmonary semilunar valve → pulmonary trunk and arteries to the lungs → pulmonary veins leaving the lungs → left atrium → bicuspid valve → left ventricle → aortic semilunar valve → aorta → to the body.
The ____________________controls the electrical impulses that cause the heart to contract continuously.
cardiac conduction system
The Specialized heart tissues that set the heartbeat pace
- The ___________________, which generates the normal rhythmical impulse. Since it initiates the normal heartbeat and causes the atria to contract, it is known as the normal “pacemaker” of the heart.
SA (sinoatrial) node,
The __________________ conveys the stimulus and initiates contraction of the ventricles.
AV (atrioventricular) node
The signal for the ventricles to contract travels from the AV node through the _______________ (Bundle of His) which divides into the left and right bundle branches then to the smaller Purkinje fibers which conduct the impulse to all parts of the ventricle.
atrioventricular bundle (Bundle of His)
Flow of the cardiac impulse:
SA (sinoatrial) node
I
AV (atrioventricular) node
I
atrioventricular bundle (Bundle of His)
I
left and right bundle branches
I
Purkinje fibers
Each heartbeat is called a
cardiac cycle.
__________ is the contraction of heart chambers; ____________ is their relaxation.
- Systole
- diastole
- The heart sounds, “lub-dup”, are due to the closing of the atrioventricular valves, followed by the closing of the semilunar valves.
- First heart sound (S1) is the _______________valves at the start of ventricular systole
closing of AV (Mitral and Tricuspid)
- Second heart sound (S2) is the ______________ valves at the end of ventricular systole
closing of the semilunar (Aortic and Pulmonic)
Heart rate =Heartbeat/ min
- The average heart rate of a young adult is around __________
60 to 90 beats/min
= fast heart rate (more than 100 beats/min)
Tachycardia
= slow heart rate (less than 60 beats/ min)
Bradycardia
= irregular heartbeat
Arrhythmia
Some factors that Increase heart rate
a.Sympathetic nervous system
i.Crisis or stress
ii.Low blood pressure
b.Hormones (e.g. Epinephrine, Thyroid hormones)
c.Exercise
d.Decreased blood volume (initial response)
Some factors that may decrease heart rate
a.Parasympathetic nervous system
b.Dereased venous return
c.In Congestive Heart Failure
= amount of blood pump by the heart per minute which is approximately 5000 ml/ min (5L/min)
Cardiac output