Lecture 3 - SQ

Question 1

1. Why are there no functional valves guarding the openings of vena cava into the right atrium?

Answer 1

1. There are no functional valves guarding the openings of the superior and inferior venae cavae
   because the negative pressure in the chest will help to suck the blood from these veins into
   the right atrium of the heart.

Question 2

2. Why is the foramen ovale present during fetal life? When does it close?

Answer 2

2. The presence of the foramen ovale during fetal life is to shunt the blood from the right atrium
   to the left atrium because the lungs are not functioning. As the baby is born, the lung will
   function and as a result the blood will go from the right atrium to the right ventricle and then
   by the pulmonary arteries go to the lungs for oxygenation by the action of respiration and
   then back to the left atrium by 4 pulmonary veins and from the left atrium to the left
   ventricle of the heart and then to the aorta; and for that reason the foramen ovale has no more
   function and so it will close nearly in few weeks after birth. The same process will happen to
   the ductus arteriosus to be converted into the ligamentum arteriosum.

Question 3

3. What would be the effect if this remained patent in a baby?

Answer 3

3. If the foramen ovale remains patent (open) in a baby it will lead to a mixture of venous blood
   with arterial blood and so the baby looks more or less blue or cyanotic in colour (i.e., blue
   baby appearance.)

Question 4

4. What are the functions of the chordae tendineae?

Answer 4

4. The function of the chordae tendinae is to regulate the action of opening and closing of the
   cusps of the tricuspid and mitral (or bicuspid) valves.

Question 5

5. Why is the thickness of the left ventricle wall so much greater than that of the right ventricle?

Answer 5

5. The left ventricle wall muscles are thicker than that of the right ventricle because it has to
   pump the blood to the aorta and then to the whole body, i.e., systemic circulation while that
   of the right ventricle has to pump the blood to the lungs only, i.e., pulmonary circulation.
   (There is a ratio of 1 to atrium, 3 to the right ventricle and 9 to the left ventricle, this ratio is
   for the thickness of the walls of the heart.)

Question 6

6. Into which structure does the coronary sinus drain?

Answer 6

6. The coronary sinus of the heart drains into the cavity of the right atrium of the heart by an
   opening lying between the inferior vena caval opening and the right atrioventricular (or
   tricuspid valve) opening.

Question 7

7. A student was ready to write the final exam of gross anatomy when she got the feeling that she
   didn’t remember anything. Her heart rate increased, she could almost hear her thumping heart.
   After reading the exam paper she felt relieved and remembered everything. Her heart rate
   started slowing down. Can you explain the nerves which caused the increase in her heart rate
   as well as helped to slow it down?

Answer 7

7. There are two nervous systems that control the rate of the heartbeat. These are the sympathetic
   nervous system that accelerates the heart beat and the parasympathetic nervous system, or
   vagus nerve, that slows the heart beat (or the heart rate); both systems are parts of the
   autonomic nervous system.

Question 8

8. What chamber of the heart lies anterior to the esophagus?

Answer 8

8. The left atrium lies anterior to the esophagus.

Question 9

9. Which pulmonary artery crosses anterior to the esophagus?

Answer 9

9. The right pulmonary artery crosses anterior to the esophagus.

Question 10

10. What regions of the body are not drained by the thoracic duct?

Answer 10

10. The right half of the head and neck, the right upper limb, the right side of the chest and upper
right part (or quadrant) of the abdomen to the level of the umbilicus. These areas drain their
lymph into the right lymphatic duct in the root of the neck.

Question 11

11. Why should the cartilaginous rings of the trachea be incomplete?

Answer 11

11. To help dilation of the esophagus during swallowing of the bolus of food because posterior to
    the esophagus lie the bodies of the vertebrae which are uncompressible; the only structure
    that can be compressed is the trachea that lies in front of the esophagus.

Question 12

12. What surface landmark on the chest wall denotes the division of the trachea into left and right
    bronchi?

Answer 12

12. The sternal angle (of Louis) is the surface landmark on the anterior chest wall which lies
    opposite the intervertebral disc between T4 and T5 vertebra posteriorly, and correspond to
    the level of the 2nd rib and its costal cartilage anteriorly.

Question 13

13. What structures are supplied by the phrenic nerve in the thoracic cavity?

Answer 13

13. The phrenic nerve (C3, 4, 5) supplies the following structures in the thoracic cavity:
    a) diaphragm (motor)
    b) pericardium (sensory)
    c) mediastinal pleura (sensory)
    d) diaphragmatic pleura (sensory)

Question 14

14. Where does the thoracic duct drain?

Answer 14

14. Thoracic duct drains lymph from most parts of the body, and ends at the point of junction of
    the left internal jugular vein with the left subclavian vein, at the root of the neck on the left
    side. It is formed from the cisterna chyli in the abdomen and it traverses the thorax until it
    reaches the root of the neck on the left side.