Biology 242 – Lab
TOPICS TO BE COVERED:
LAB #4
(4th/19 Lab Sessions for Winter Quarter, 2008)
THE HEART
DESIRED OUTCOMES:
After completing the activities described for this lab session, students should:
MATERIALS NEEDED:
Structures of the Heart to view (or be aware of) during dissection of the Sheep’s Heart:
I. Six groups of four structures:
A. Layers of the Heart
1. Fibrous pericardium (aka parietal pericardium)
2. Epicardium (aka visceral pericardium)
3. Myocardium (composed of cardiac muscle tissue – thickest in the LV; thinnest in RA + LA)
4. Endocardium (composed of simple squamous epithelium; it is the lining of the heart)
B. Great Vessels entering or exiting the Heart
1. Vena Cavae (these both deliver deoxygenated blood to the Right Atrium)
a. Superior Vena Cava – delivers blood returning from structures above the diaphragm)
b. Inferior Vena Cava – delivers blood returning from structures below the diaphragm)
c. Note: Altho’ NOT a great vessel, the Coronoary Sinus also empties into the RA)
2. Pulmonary Veins (these deliver oxygenated blood to the Left Atrium)
a. Veins from three Right Lung Lobes merge into 2 Right Pulmonary Veins
b. Veins from two Left Lung lobes each enter directly, therefore 2 Left Pulmonary Veins
3. Pulmonary Trunk (routes deoxygenated blood from the Right Ventricle to the Lungs
(This Great Vessel bifurcates to give rise to the R + L Pulmonary Arteries)
4. Aorta (routes oxygenated blood from LV to systemic circulation)
a. There are three main parts of this largest of all arteries: Ascending Aorta, Arch of the
Aorta, and the Descending Aorta (Thoracic portion, Abdominal portion)
C. Chambers of the Heart
1. Right Atrium – RA (with attached right auricle) (Greek: atrion = hall or “receiving room”)
2. Left Atrium – LA (with attached left auricle)
3. Right Ventricle – RV
4. Left Ventricle – LV
D. Septae (partitions between chambers)
1. Interatrial septum (partitions RA from LA)
2. Interventricular septum (partitions RV from LV)
3. Right Atrioventricular septum (partitions the RA from RV)
4. Left Atrioventricular septum (partitions the LA from LV)
E. Valves (based on shape of valve leaflets, there are two “cuspid” valves and two “semilunar” valves)
1. Tricuspid Valve (aka Right AV Valve) (between RA and RV) – has three cuspate leaflets
2. Bicuspid Valve (aka Left AV Valve or Mitral Valve) (between LA and LV)- has two cuspate flaps
3. Pulmonary Semilunar Valve (between RV and beginning of the Pulmonary Trunk)
4. Aortic Semilunar Valve (between LV and beginning of the Aorta)
F. Parts of the Conduction System
1. Sinoatrial Node (SA Node) aka “the Pacemaker”
2. Atrioventricular Node (AV Node)
3. Atrioventricular Bundle (AV Bundle) aka Bundle of His
a. Runs as one bundle for a short distance in the interventricular septum, then bifurcates into
b. Right Bundle Branch (serving the Right Ventricle)
c. Left Bundle Branch (serving the Left Vetnricle)
4. Conduction myofibers aka: Purkinje fibers
II. Other Structures to note:
A. To tell anterior from posterior aspects of the heart:
1. Of the two auricles, the “free apex” portion of each points medio-anteriorly
2. Apex of the heart (all of which is contributed to by LV) lies inferior and to the left of midline
3. Pulmonary Trunk is anterior-most of the great vessels
4. Vena cavae, Pulmonary veins and Coronary Sinus are posterior
B. Sulci (singular: sulcus) and Associated Anatomy
1. Superficial grooves marking the boundaries between adjacent chambers
2. Sulci contain branches of coronary blood vessels and variable amounts of fat (adipose C.T.)
3. Right Coronary Artery – runs in RAV sulcus to R border of the heart where it bifurcates to
become the Marginal (Branch) A. and the Posterior Interventricular A.
4. Left Coronary Artery – runs only a short distance before it bifurcates into the Anterior Interventricular A. (running in the anterior interventricular sulcus) and the Circumflex A. (running
in the LAV sulcus)
C. Three distinct configurations of myocardial muscle tissue:
1. Trabeculae carnae = “fascicles” that give a “woven appearance” of ridge-like bands attached
at both ends and all along the underside of the ridges.
2. Pectinate muscle = bands of muscle that are attached at both ends, but free underneath; like a
“bridge of muscle. There is almost always one pectinate muscle in the
RV, sometimes two. Sometimes there is one in the LV.
3. Papillary muscle= large “papilla” of muscle tissue, attached at one end, but free at the other
end. Chordae tendinae associated with the AV valves insert into the
free end of these papillary muscles. Found only in the ventricles – 3 in
the RV and 2 (groups) in the LV.
D. Arteries arising from the Aorta:
1. The Right and Left Coronary Arteries are the first two branches off the Aorta, and the only
two off the Ascending Aorta. The heart gets “first dibs” at the freshly oxygenated blood
2. Off of the Arch of the Aorta come three (branches) arteries that are unequal in size:
a. Brachiocephalic Trunk, which fairly quickly bifurcates into
1. Right Common Carotid Artery
2. Right Subclavian Artery
b. Left Common Carotid Artery
c. Left Subclavian Artery
3. Off the Thoracic Descending Aorta come all the intercostals arteries (aka Segmental A.),
the bronchiolar arteries, the Superior Phrenic A, etc.
4. Off the Abdominal Descending Aorta – that list is yet to come
III. On the Heart Models:
A. Remnants of fetal structures: Foramen ovale → Fossa ovalis
Ductus Arteriosus → Ligamentum arteriosum
B. Parts of the Conduction System of the Heart: SA Node, AV Node, AV Bundle, Purkinje fibers
C. Identify representations of the Right Coronary Artery (and its branches) and the Left Coronary
Artery (and its branches)
D. Observe valves, chordae tendinae, cardiac muscle tissue configurations, coronary sinus, etc.