Lab 3: Heart Dissection, Recording and Interpreting ECG Flashcards
How many sides and chambers does the heart contain?
- Two-sided
- Four chambered
What is the ventral surface of the heart called? What does it face?
- Auricular surface
- Facing the left thoracic wall
Explain the name of the auricular surface.
The tips of the two auricles projects on the left thoracic wall
What does the atrial surface project?
Right thoracic wall
Which grooves are found in the auricular and atrial surfaces?
- Auricular: paraconal interventricular groove
- Atrial: subsinuosal interventricular groove
What is the thin membrane that covers the heart called?
Pericardium
What is the pericardium?
Double-layered closed sac that surrounds the heart
What forms the phrenicopericardial ligament?
The continuation of the pericardium to the sternum and diaphragm
What are the two tissue layers of the pericardium? Differentiate them.
- Visceral pericardium (covers the surface of the heart)
- Parietal pericardium (covers the inner surface)
What is the pericardial cavity? What is its function?
- Gap between the parietal and visceral surfaces
- Filled with fluid to reduce friction between the layers as the heart pumps
Which muscle is located below the pericardium? Where is it mostly located?
- Myocardium
- Mostly located in the ventricles
What is the tip of the heart called?
Apex
Which ventricle extends all the way to the apex?
Left ventricle
How would you place a heart on your bench so that it would be positioned the same as within our body?
Ventral side towards you
What is the function of the coronary artery?
Supplies fresh blood with oxygen and nutrients to the heart muscle itself
Where does the coronary artery lie? Where does it branch?
- In the groove on the front of the heart
- Branches over the front and back side of the heart
Where is the pulmonary artery found? What is its function?
- Curving out of the right ventricle
- Branches and carries blood to the lungs to receive oxygen
Where is the aorta found?
- Near the right atria
- Behind the pulmonary trunk
What is the curved part of the aorta called?
Aortic arch
What branches from the aortic arch? What is its function?
- Brachiocephalic artery
- Supplies blood to the upper body
What is the function of pulmonary veins?
Return oxygenated blood from the right and left lungs to the left atrium
Where are the inferior and superior vena cava found? What is their function?
- Connect to the right atrium
- Deoxygenated blood enters the body through these vessels
How does the muscular walls of the right side of the heart compare to the left side?
Thinner muscular wall
What are the two atrioventricular valves?
- Tricuspid: right atrium and right ventricle
- Bicuspid (mitral): left atrium and left ventricle
What are the cordae tendinae?
Long fibers of connective tissue that attach the atrioventricular valves to the papillary muscles of the heart
What occurs to the atrioventricular valves during diastole and systole?
- Diastole: valves are open
- Systole: valves are closed
Differentiate systole and diastole.
- Diastole: period when the heart is relaxed
- Systole: period when the heart begins to contract
What is the septum?
The thick muscular wall that separates the right and left pumping ventricles from each other
What is the trabeculae carneae?
Network of irregular muscular cords on the inner wall of the right and left ventricles
What is the function of the pulmonary semilunar valve?
Controls blood flow away from the right ventricle to the pulmonary artery
What is the function of the aortic semilunar valve?
Controls blood flow away from the left ventricle to the aorta
Where do the two holes in the aorta lead into?
Into the coronary artery, which carries blood to and nourishes the heart muscle itself
What is the difference between a pig heart and a human heart?
- Size (pig is larger)
- There are two branches on the aortic arch for the pig
- There are three branches on the aortic arch for the human
Differentiate the epicardium, myocardium, and endocardium.
- Epicardium: outer layer of heart wall (visceral layer)
- Myocardium: muscle tissue of heart
- Endocardium: inner layer of heart wall
What are auricles?
Earlike appendage of each atrium of the heart
Which muscle is lining the auricles?
Pectinate muscle
What is trebeculae septomarginalis? Where is it found? What is its function?
- Inside the right ventricle
- Extending from the septal wall to the opposite wall
- Part of the conduction system of the heart
- Extension of the right bundle of His, necessary for the conduction of the right ventricle
Which two components exhibit reverse blood flow?
- Pulmonary artery: deoxygenated blood flowing through an artery
- Pulmonary vein: oxygenated blood flowing through avein
How do veins and arteries differ in terms of their location?
Most of the time, the veins are on top and the arteries are underneath
When does the coronary artery fill from the aorta? Why is that particular?
- When the ventricle relaxes
- They are the only vessels in the body that fill when the heart is in diastole
Where do both coronary arteries originate?
Aortic sinus
Where is the aortic sinus located?
Right above the aortic semilunar valves
What is the function of the right coronary artery?
- Leaves right sinus
- Supplies blood to right atrium and right ventricle
What is the function of the left coronary artery?
- Leaves left sinus
- Short branch splits into two arteries: circumflex and paraconal
What are the two arteries that split from the left coronary artery?
- Circumflex artery
- Paraconal artery (animal anatomy)
Where does the circumflex artery lead to?
- Coronary groove
- Base of the heart
- Feeds the left side of the heart
Where does the paraconal artery lead to?
Along paraconal interventricular groove (located down the septal wall)
What is the function of the great cardiac vein?
- Blood is returned to the right atrium
- Via the coronary sinus
Differentiate the aortic and coronary sinus.
- Aortic: oxygenated blood
- Coronary: deoxygenated
What is the human anatomy version of a paraconal artery?
Anterior interventricular branch of the left coronary artery
What is the function of the sinoatrial node? Where is it located?
- Autorhythmic pacemaker cells
- Located in the right atrial wall near the superior vena cava
What is the function of the atrioventricular node? Where is it located?
- Slows down the conduction speed
- Right atrium along the lower part of the interatrial septum
What do the atrioventricular bundle and Purkinje fibers originate from?
The AV node
What is the function of the atrioventricular bundle and Purkinje fibers?
- Extend down the septum
- Become Purkinje fibers at lateral walls of ventricles and papillary muscles
What is the function of the AV node delay?
The atria needs to contract fully before the ventricles commence contraction
Is the heart regulated by the nervous system?
- The heart is innervated/regulated by the automatic nervous system, but ONLY to increase or decrease heart rate
- The heart possesses self-excitable cells in the SA node that do not require input from the nervous system to contract
Where do the sympathetic fibers arise from?
Segments T2, T3, T4 of the spinal cord
Where are the sympathetic fibers distributed through?
- Through the middle cervical and cervico-thoracic (or stellate) ganglia
- And the first four ganglia of the thoracic sympathetic chain
What provides the parasympathetic control to the heart?
The vagus (cranial nerve X)
What is the function of the parasympathetic and sympathetic nervous system on the heart?
- Parasympathetic: lowers heart rate
- Sympathetic: increases heart rate
What is an electrocardiogram?
Graphic record of the heart’s electrical activity (conduction impulse)
Does an ECG record the heart’s contractions?
No, it records the electrical events that precede them
What occurs when the ECG remains constant?
The heart wall is completely relaxed, with no change in electrical activity
What occurs at the P wave?
When the AV node and atrial walls depolarize
When does contraction occur in response to depolarization?
Cardiac muscle contraction occurs AFTER depolarization begins
What occurs between the P wave and the QRS complex?
Atrial walls are completely depolarized (no change recorded in ECG)
What occurs in the QRS complex?
- Atrial walls repolarize
- Ventricular walls depolarize
- Ventricular walls depolarizing MASKS the atrial repolarization
What occurs between the QRS complex and the T wave?
- The atrial walls are completely repolarized
- The ventricular walls are completely depolarized
- No change is seen in the ECG
What is the T wave?
The ventricular walls repolarize
What does the PR interval represent?
Delay of AV node to allow filling of ventricles
What is necessary to allow the opening of valves?
The pressure of the starting point must be larger than the pressure of the ending point
What does the “lub” sound signify?
Closing of AV valves
What does the “dub” sound signify?
Closing of SL valves
At which step of the ECG does the “lub” sound occur?
During the QRS complex
At which step of the ECG does the “dub” sound occur?
During the T wave
What is blood pressure?
The pressure exerted by circulating blood on the walls of blood vessels
What is systolic pressure?
Pressure as your heart beats and pushes blood through the blood vessels
What is diastolic pressure?
Pressure when the vessels relax between heartbeats
What is the optimal blood pressure?
- 120 (systolic) over 80 (diastolic)
- Measured in mmHg
How many times does the heart beat or contract per minute?
70 times
How is the sphygmomanometer cuff calibrated?
- Blood pressure cuff is inflated up to 100 mmHg
- The cuff is deflated to 40 mmHg
Why is the blood pressure cuff placed on the subject’s right arm?
So that the “artery” label is over the brachial artery
To obtain accurate measurements, it is important that the cuff pressure is released at a rate of __-__ mmHg per second.
2-3
How is a measurement of the blood pressure and ECG obtained?
1) Cuff is pumped until 160mmHg
2) Valve is slowly released to begin releasing cuff pressure
3) Pressure is released constantly until systole and diastole have been registered
Where are electrodes connected to the leads?
- Right forearm (above wrist)
- Inside right leg (above ankle bone)
- Inside left leg (above ankle bone)
Lack of blood supply to the brain results in what?
Cerebral ischemia
What is the occlusion of a coronary artery caused by?
Atherosclerotic plaque detachment
What does an occlusion of a coronary artery lead to? What may that lead to if untreated over time?
- Ischemia (restriction in blood supply)
- Oxygen shortage to heart tissue (death of myocytes)
- Myocardial infarction
Explain the development of atherosclerosis and hypertension.
- Increase in calcification (rough and rigid arteries)
- Collection of lipids and macrophages in the wall of arteries
Where does the death of myocardial cells first occur?
- In the area of the myocardium that is the most distal to the arterial blood supply
- Endocardium
As the duration of the occlusion causing ischemia increases, where does the area of myocardial cell death enlarge to? What is the disadvantage?
- Endocardium to myocardium to epicardium
- Inside to outside
- They will not be diagnosed readily because cell death occurs inside first (undetected)
What occurs in terms of the histopathology of a myocardial infarction?
- Loss of branching pattern
- Necrosis of myocytes
- Infiltration of neutrophils
- Loss of nuclei
- Degradation of Na+/K+ membrane gated channels
What is the consequence of the degradation of Na+/K+ membrane gated channels during a myocardial infarction?
Edema
What are methods of prevention for myocardial infarctions?
- Regular medical checkups
- Control BP
- Check cholesterol
- Don’t smoke
- Exercise regularly
- Maintain healthy weight
- Manage stress
What are risk factors for myocardial infarction?
- Obesity
- Unhealthy lifestyle
- Smoking
- Diabetes
What is the progression of ischemia within the cardiac muscle tissue?
Restriction of blood flow to the heart occurs from the inside (endo, myo, epi)
Are cardiac muscle cells dependent or independent on one another?
- They depend on one another, as 99% are composed of contractile cells, which may not stimulate an action potential on their own
- The heart contracts as a unit
How does the tar in tobacco affect heart function?
- Tar (in tobacco) blocks small alveoli within the lungs
- Decreases O2 transport efficiency
How does smoking affect heart function?
- Makes the heart beat faster because of an increase in blood pressure, which causes arteries to constrict
- Over time, it exerts more pressure on the wall, which may cause an atherosclerotic plaque to appear
Anatomy insert
doajosfi
Where does deoxygenated blood come from to fill the right atrium?
- Superior and inferior vena cava
- Aortic sinus
Which valves are open during the P wave?
- AV valves are open
- SL valves are closed
Which valves are open during the QRS complex?
- AV valves close (close during the R)
- SL valves are open
Which valves are open during the T wave?
- AV valves are closed (initially, opens later)
- SL valves close at the end of the T wave
