The Heart
A-Chapter 12
Objectives:
1. Identify the layers of the heart wall and state the type of tissue in each
layer.
2. Label a diagram of the heart, identifying the chambers, valves, and
associated vessels.
3. Trace the pathway of blood flow through the heart, including chambers,
valves, and pulmonary circulation.
4. Identify the major vessels that supply blood to the myocardium and return
the deoxygenated blood to the right atrium.
5. Describe the components and function of the conduction system of the
heart.
6. Summarize the events of a complete cardiac cycle and correlate the heart
sounds heard with a stethoscope with these events.
7. Explain what is meant by cardiac output and describe the factors that
affect these values.
I. Introduction
A. Importance of the heart
1. Pump which supplies blood to all cells/tissues
2.
3. Normal adult-________________________________
B. Relationships with other systems. P. 224
II. Overview of the heart
A. Form, size & location of the heart
1. Position & importance
a. thoracic cavity/middle mediastinal region
b.
c. CPR, ECG’s
d. Posterior to sternum, anterior to spinal column
2
3. Apex=tip, pointed end of the heart
Direction of apex is inferior, anteriorly and to the left
4. Base~superiorly, posteriorly & to the right
5. Size of the heart is size of a closed fist
B. Coverings of the heart
1. Pericardium
a.
b. surrounds heart & proximal vessels
c. visceral pericardium -fibrous
d. parietal pericardium –serous
e.
f. Pericardial cavity is filled with fluid. This reduces friction
between the membranes
CLINICAL APPLICATIONS
Pericarditis-inflammation of the pericardium. This disrupts the
heart contractions.
III. Structure of the heart
A. Layers of the heart wall (3 layers) fig. 12.2
1.
a. thin, protective layer
b. firmly attached to middle layer
c. location of blood vessels which nourish the heart wall
2. MYOCARDIUM (middle layer of heart)
a. thick layer
b.
c. made of cardiac muscle tissue
d. tissue/cells are connected & communicate
-they lay at different angles & Form the force to pump
the blood
3. ENDOCARDIUM (inner layer of heart)
a.
b. smooth surface allows blood _______________
c. forms valves of the heart
RA—LA—LUNGS—RV—LV—AORTA
B. Chambers of the heart fig. 12.3
(4 chambers)
1. Atria/Atriums (2-right, left)
a. thin walled-only pumps to lower chambers of the heart
b.
-vena cava’s (superior/inferior)
- coronary sinus return deoxygenated blood from heart
muscle to Right atrium
c. holding chamber
d.
e. Left atrium –high O2, low CO2
-receives blood from 4 pulmonary veins returning to the
heart from the lungs (oxygenated)
2.
~Pumping chambers
~Both ventricles hold same amount of Blood
a.
b. Right ventricle
-receives blood from RA and pumps blood to the lungs and
back
-blood low in O2, high in CO2
c.
-receives blood from LA and pumps blood to the entire
body
-very thick myocardium
C. Valves of the heart fig. 12.4,12.5
1.
a. to keep blood in a chamber
b. to keep blood flowing in one direction
c. long cords inside control the opening
2.
a. valves between atrium & ventricles
b. closes to prevent backflow into atrium when ventricles
contracting
c.
3.
d. Left AV valve=Bicuspid valve
a. located at base of large vessels where blood leaves the heart
b. Right side blood leaves RV & enters aorta going to the body
CLINICAL APPLICATIONS
~disease may damage heart valves & they won’t work properly
~backflow of blood may occur
~valvular stenosis=valves become stiff & won’t fully open
E. Pathway of blood through the heart fig. 12.6
1. Remember~
a. both atriums contract at the same time (squeeze together)
b. both ventricles contract at the same time
c. heart functions as 2 separate pumps
Right side ________________________
Left side ________________________
Pulmonary circulation- heart-lung-heart
Systemic circulation-heart-body-heart
2.
-deoxygenated blood enters the RA from the inferior/superior vena cava
-atriums contract pushing blood through the AV valve and to the RV
-ventricles contract pushing blood through semilunar valves into pulmonary arteries
-blood travels to the lung in the pulmonary arteries where gases are exchanged.
CO2-O2
-Blood returns to heart by way of the pulmonary veins & enters the LA
-LA contracts pushing blood through the AV valve and into the LV
-Ventricles contract pushing blood through semilunar valves into the aorta.
F.
1. Myocardium needs a constant supply of O2/nutrients
a. heart muscle CANNOT build up O2 debt like skeletal muscle
b. heart has extensive network of blood vessels to serve the
heart itself
2.
a. coronary arteries
b. anterior interventricular artery
c.
3. Greatest flow when heart contracting
CLINICAL APPLICATIONS
Angina pectoris=chest pain due to demand for O2 greater than you have.
Nitroglycerin tablets dilates vessels to release pressure
MI (myocardial infarction) heart attack
-blockage of coronary causes death of heart tissue
-enzymes are released when heart muscle is damaged. You can tell if you’ve
had a mild heart attack by reading enzyme levels
4. Cardiac veins returns deoxygenated blood to the right atrium
Read p. 230 Pioneers of Anatomy & Physiology
Werner Forssmann
IV.
A. Conduction System-intro
1. Heart must be synchronized & act as one (cells connected by
channels for communication)
2. Contraction of chambers by cardiac muscle cells of the conduction
system
3.
B. Components of the conduction system fig. 12.8
1.
a. posterior wall of RA near entrance to the S. Vena cava
b.
c. PACEMAKER of the heart
d. cause BOTH atria to contract together
e. impulse initiates second part of system
2. Atrioventricular node (AV node) dub sound
a.
b. impulse travels slower than SA
-allows time for atria to finish contracting
c.
CLINICAL APPLICATIONS
When cells contract out of the pattern, it is called an arrhythmia. It
can lead to tachycardia (heart racing) and then death.
3.
a. Impulses conducted through the heart produce electrical
currents which can be measured on the surface of the body
b.
C. Cardiac Cycle fig. 12.10
1. Defined-alternating contraction & relaxation of the myocardial walls
coordinated by the conduction system during one heartbeat
2. Systole3. Diastole-when the heart relaxes
4.
D. Heart sounds
1. one hears the closing of heart valve when listening with a
stethoscope
2. Lub-dub sound
3.
E. Cardiac output
1. Defined-the volume of blood pumped through a ventricle in 1 minute
2. cardiac output=volume x heart rate
Ex. 70 ml/beat x 72 beats/min = 5040 ml/min
3. The heart recycles all your blood in 1 minute!
4. Cardiac output changes with amount of activity
5. Heart rate
a. changes in heart rate controlled by medulla oblongata of the
brain
b. affected by
-oxygen needs
-depression
-CO2 concentrations
-