Physician's Notebooks: 6.1 Cardiovascular Respiratory System Physician's Notebooks 6

Note, the tracing of Heart indicated by outline (Not easy to see in the Figure; use a magnifier) over the lungs. Right-left pairs of ribs on each side should be numbered from above down and are 10. (Additionally, 2 pairs of “floating ribs” are attached behind to spine below 10th rib.) Note the left nipple surface marker is located between 4th and 5th rib, a little more than midway out from center of chest and slightly to left of heart outline. Lung shape is drawn in lavender color. The light blue parts below it are extensions of the lungs' cover (the pleura) and the potential space that the lungs can expand into when inhaling. The whole area of potential lung space (lavender above and light blue below) on left and right is enclosed in an elastic sort of inner tube which contains left and right pleural spaces and if punctured from the outside or over lung surface causes a left or right pneumothorax with collapsed left or right lung and needs to have lung re-expanded by insertion of under suction. Pneumothorax is frequent in young Japanese men who fly jet. In the rare case it is bilateral it will cause sudden respiratory failure death if not treated immediately by chest tube insertion in one side or the other.

Heart is superimposed on Lungs. Apex of heart is at lower left corner of its outline in the figure. (Borders also refer to an anterior-posterior chest x-ray.) The heart’s left border is mostly its left ventricle except near top it is left atrium. The bottom flat line of Heart is lower border of left and right ventricles sitting on the diaphragm muscle that separates chest above from abdomen below. Right border of heart from below is right ventricle and, above it, right atrium. Top part of Heart, behind breastbone, is called the base. (Confusing because "base" is usually bottom.) Reader interested in physical examination of Heart, now, click 6.15 Paul Dudley White Method to Study Heart .

Heart is set in the frontal niche within the lungs with the front edges of right and left lungs partly lying over the right and left front of Heart. Major portion of front surface of Heart is not covered by Lung. (And therefore vulnerable to trauma)

Heart is somewhat movable. When you lie on left side, the point of heartbeat (the apex) is felt more to left. When you lie face down, heart comes closer to front chest wall. A heart sac overfilled with fluid (either too much blood or excess body water fluid) appears enlarged on examination and on chest x-ray. Obstructions within the heart make for abnormal bulges seen best on frontal chest x-ray.

Breathing (Bronchial) Tube system from mouth to lungs

You can easily feel your Adam’s apple and at its top you should feel a small notch, and, below that, the cricoid cartilage.

Figure: Trachea & Bronchial System of Respiratory Tract

Below the cricoid cartilage you see the trachea. Surgeon may cut a hole in its uppermost front to assist breathing when an upper airway obstruction occurs. As part of advanced CardioPulmonary Resuscitation (CPR), an anesthetist may insert an endotracheal breathing tube, and then oxygenated air is passed into the tube as part of assisted ventilation.

Take a deep breath and hold it. When you begin it, you contract the muscles of chest wall and your diaphragm at lungs’ base, to pull the chest wall and its base away from underlying lung. In the seconds just after that, your lungs expand into this space, as a balloon that is opened to the air would expand if surrounded by vacuum. This expansion creates negative pressure within millions of tiny lung sacs (alveoli) that form the lungs and each one through its communicating tube sucks air into the lungs from mouth via trachea.

Now, let out your held breath. You can feel and almost hear the air go out of mouth and note that your chest wall pulls together. Exhalation can simply be the ceasing the act of inhalation, allowing the muscles to assume their former relaxed state. Exhalation is made possible by the elasticity of Lungs and chest wall. Like a balloon’s covering, once the pull on it ends, it collapses back into a smaller volume.

So we see breathing as an active inhalation and a passive exhalation. One addition! Though inhalation is done consciously, it also can be done while asleep or in coma by involuntary control at base of brain that takes over breathing when blood oxygen or carbon dioxidesignals the need.

The function of breathing is drawing oxygen O2 from air into the lungs and, from there, into the red blood cells and removing the carbon dioxide CO₂from the red blood cells and expelling it from the lungs. Rate and depth of breathing are important voluntary variables to control the O2 in the cells and the CO₂content of blood. Get a clock with seconds hand, and time the number of your consciously controlled breaths in 60 seconds: First, breathe 10 times in 60 seconds; then do 40 times. Finished? Note your breathing rate is under your control within the wide range. Also, take a shallow breath; then a very deep breath.

The faster you breathe and/or deeper you breathe the more oxygen gets into your blood, and the less CO₂ remains in your blood (within upper & lower limits). A contradiction exists between your breathing's rate and its depth since a deep breath takes more time than a shallow breath. However, within limits each of us can increase rate of deep breathing.
The respiratory rate and depth are important voluntary controls that can affect your blood & tissue oxygen, carbon dioxide and acid/base values.
End of Chapter 1, Physician's Notebooks 6. To read next, now click 6.(2-3) Healthy Heart/The Valves/Heart Failure/Tr...

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Thursday, September 23, 2010

6.1 Cardiovascular Respiratory System Physician's Notebooks 6 - , Chap 1

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