Cardiovascular System

LABORATORY INSTRUCTION: THE CARDIOVASCULAR SYSTEM

I. HISTOLOGY: Use the microscope to observe the following prepared slides.

A. Cardiac muscle: notice striations, branched fibers, intercalated disks, central nuclei.

B. Artery/vein cross-section: Walls of an artery typically contain elastic and/or smooth muscle to the extent that the wall appears thick, compact, and very rounded or oval in cross-section. Walls of a vein are thinner, contain little smooth muscle, and tend to collapse during slide preparation into various folded shapes in cross-section. Identify the lumen of each vessel, the tunica externa (adventitia), composed of connective tissue; the tunica media, composed of smooth muscle and elastin; and the tunica interna or intima (endothelium), composed of simple squamous epithelium.

II. GROSS ANATOMY OF THE HEART AND GREAT VESSELS: Use all available plastic models, torsos, charts, and preserved specimen to find the structures named below. Refer to the labeled diagrams and photographs in your text and lab atlas. The keys which go to the numbered models are not helpful as they contain more information than is required.

great vessels

apex

atria

auricles

left ventricle

right ventricle

pulmonary trunk

systemic aorta

tricuspid valve

bicuspid (mitral) valve

pulmonary semilunar valve

aortic semilunar valve

base

apex

B. Layers of heart walls
     1. epicardium (visceral pericardium)
     2. myocardium
     3. endocardium

C. Chambers
     1. atria (right and left with interatrial septum)
     2. ventricles (right and left with interventricular septum)
     3. trabeculae carneae evident in walls, especially in ventricles
     4. auricles (external flaps associated with atria)

D. Valves
     1. atrio-ventricular valves (cusps, chordae tendineae, and papillary muscles)
         a. bicuspid (between left atrium and left ventricle)
         b. tricuspid (between right atrium and right ventricle)
     2. semilunar valves (3 flaps)
         a. pulmonary (at base of pulmonary trunk)
         b. aortic (at base of systemic aorta)

E. Great vessels
       1. pulmonary trunk exits right ventricle
       2. systemic aorta exits left ventricle
       3. superior vena cava enters right atrium from above
       4. inferior vena cava enters right atrium from below

F. Coronary circulation:
      1. coronary sinus, drains myocardium into right atrium
      2. left coronary artery
           a. anterior interventricular (anterior descending) artery
           b. circumflex artery
      3. right coronary artery
            a. marginal artery
            b. posterior interventricular artery

III. GROSS ANATOMY OF THE MAJOR BLOOD VESSELS: Use the available torsos and dissected preserved cats to find examples of the following blood vessels. Use the labeled sketches and photographs of the text or lab atlas to guide your study.

          A. Great vessels
                1. superior vena cava
                2. inferior vena cava
                3. pulmonary veins
                4. pulmonary trunk
                5. systemic aorta

B. Branches of descending aorta
        1. from ascending aorta, right and left coronary artery
        2. from aortic arch, brachiocephalic artery
            a. right subclavian artery
              -axillary artery
              -brachial artery
                 -ulnar artery
                 -radial artery
              -circumflex artery
              -palmar arch
              -digitals
            b. right common carotid artery
              -right superficial temporal artery
            c. (cat, not human ) left common carotid artery
        3. left common carotid artery
            -left superficial temporal artery
        4. left subclavian artery (cat and human)
              -axillary artery
              -brachial artery
                 -ulnar artery
                 -radial artery
              -circumflex artery
              -palmar arch
              -digitals
        5. from descending thoracic aorta
           -paired intercostal arteries
        6. from abdominal aorta
           a. celiac trunk
              (1) splenic artery
              (2) l. gastric artery
              (3) hepatic artery
           b. superior mesenteric artery
           c. paired renal arteries
           d. paired gonadal arteries
           e. paired lumbar arteries
           f. inferior mesenteric artery
           g. right and left common iliac arteries
              -internal iliac arteries
              -external iliac arteries
              -femoral arteries
              -popliteal arteries>anterior & posterior tibial arteries>dorsalis pedis arteries>arcuate
               arteries>metatarsal arteries

     C. Major veins
         1. coronary circulation: coronary sinus
         2. pulmonary circulation: pulmonary veins
         3. hepatic portal circulation: hepatic portal vein
         4. systemic circulation:
             a. superior vena cava
                  -azygos system (only visible on cat)
                  -right and left brachiocephalic veins
                  -jugular veins
                  -superficial temporal veins
                  -subclavian vein then axillary vein
                  -brachial vein
                  -cephalic vein (superficial)
                  -basilic vein
             b. inferior vena cava
                 -phrenic veins
                 -hepatic vein
                 -paired renal veins
                 -paired gonadal veins
                 -paired common iliac veins
                 -paired internal iliac veins
                 -paired external iliac veins
                 -femoral veins
                 -popliteal vein
               -dorsalis pedis vein
                 -dorsal venous arch
                 -great saphenous veins

D. Lymphatic System: Observe the green lymph vessels and associated lymph nodes on available models.

FOR THE LAB PRACTICAL, BE ABLE TO RECOGNIZE AND NAME THE VESSELS ABOVE ON APPROPRIATE CHARTS, MODELS, AND PRESERVED CATS.

IV. CARDIOVASCULAR PHYSIOLOGY

A. Blood Pressure: The typical device used clinically for measurement of blood pressure is the sphygmomanometer which consists of an inflatable cuff attached to a pressure measuring device (gauge). The artery most typically selected for use in measuring blood pressure is the brachial artery. On occasion, the femoral artery may be preferred

systolic

diastolic

Another instrument required to obtain a measurement of blood pressure is a stethoscope. This device is useful for several clinical observations: listening to breathing sounds for evaluation of airway obstruction, listening to heart sounds for evaluation of valvular function, and listening for resumption of blood flow in response to external pressure changes induced by the sphygmomanometer.

1. In preparation for measuring the blood pressure, wipe the earpieces of a stethoscope with disinfectant swabs and air dry. Place the earpieces of the stethoscope at the opening of your outer ear canal. (The supports for the earpieces curve forward for best results).

2. In order to measure blood pressure in the brachial artery, the cuff is wrapped around the upper arm and secured with hooks or Velcro depending upon the design of the particular cuff.

3. Place the diaphragm (flat part) of the stethoscope over the brachial artery as it crosses anterior and slightly superior to the elbow joint.

4. A bulb is attached by a rubber tube to the cuff. Upon squeezing the bulb, the cuff inflates, (If inflation does not occur, try tightening the screw-valve or rotating between the thumb and forefinger as you continue to squeeze the bulb.) It should take 4 or 5 squeezes to inflate the cuff to the appropriate level.

5. While inflating, watch the pressure measuring device attached. This may be a mercury column that rises within a calibrated scale, or it may be a needle moving around a dial. The pressure should read above 200 but less than 250 mm Hg when inflation is completed. DO NOT GO HIGHER. Immediately turn the screw-valve to release pressure slowly as you watch the mercury column or the needle drop to lower pressures. YOU HAVE COMPLETELY BLOCKED BLOOD FLOW AT THIS POINT. NEVER LEAVE THE PRESSURE THIS HIGH, IMMEDIATELY ALLOW RELEASE OF THE VALVE.

6. As the pressure drops, listen for a rhythmic tapping sound (Korotkoff Sounds) which is a result of blood being forced through the brachial artery. Make a notation of the pressure reading when the first sound is heard. This value corresponds to the level of blood pressure which is able to overcome the external pressure of the cuff and force blood through the artery. Known as the "systolic" pressure, this pressure is the maximum pressure of the blood against the walls of the brachial artery and corresponds to the surge of blood sent through the system with ventricular systole.

7. Continue slowly releasing air from the cuff and listening to the "tapping" sounds. If you hear the sounds become suddenly muffled, or if the sounds stop altogether, note the pressure reading immediately, as this corresponds to the pressure at which blood can flow through the artery without impedance; that is, the minimum pressure of blood in the brachial artery, the "diastolic" pressure which is the pressure maintained even when the ventricles are in diastole.

8. The two values are written as a fraction: systolic/diastolic

9. CAUTION: Immediately begin to lower the pressure in the cuff after exceeding 200 mm Hg. DO NOT leave the cuff inflated--you have cut off the blood supply to your friend's lower arm and hand--have mercy! Do not re-inflate the cuff until it has been completely deflated and normal circulation restored in the arm for a few minutes. ALLOW YOUR PARTNER TO REST AND RECOVER BETWEEN MEASUREMENTS. AFTER THREE TRIES, CHANGE ROLES. (ALLOW AT LEAST TWO MINUTES BETWEEN ATTEMPTS.)

10. After you have practiced taking your lab partner's blood pressure, getting similar readings two times, then try various conditions: lying down, sitting, standing, after stepping in place for 3 minutes, after a rest period of five minutes after stepping. Compare results with other classmates.

B. Pulse Rate: Pulse rate can easily be measured by lightly pressing the radial artery across the styloid process of the radius and counting the pulsations while watching a second hand. If you count for 15 seconds, multiply by four to get pulse/min. If you count for 30 seconds, multiply by two. Another place pulsations can be counted easily is at the bifurcation of the common carotid artery, inferior and medial to the angle of the mandible. Care should be taken not to press too hard in this location since pressure receptors are located within the artery wall at this point, and blood pressure will change in response to the external pressure.

Lying down: __________ rt. arm _____________
lt. arm _____________

(now choose either rt. or lt. and stay consistent)

Sitting ___________ _____________

Standing ___________ _____________

After short ___________ _____________
exercise

After rest ___________ _____________
five min.

C. Heart Sounds: Use the stethoscope to listen to heart sounds. Try several positions on the anterior chest wall. Choose a location which gives you the clearest sound (usually nearest the apex). Listen to the heart sounds of several classmates and try to compare the "lubb-dupp" patterns.