Wilderness Medicine, First Aid, and Outdoor Skills
Understanding Vital Body Functions

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US Army First Aid Manual
Fundamental Criteria for First Aid
Basic Measures for First Aid
First Aid for Special Wounds
First Aid for Fractures
First Aid for Climatic Injuries
First Aid for Bites and Stings
First Aid in Toxic Environments
First Aid for Psychological Reactions
Appendix A: First Aid Case and Kits, Dressings, and Bandages
Appendix B: Rescue and Transportation Procedures
Appendix C: Common Problems/Conditions
Appendix D: Digital Pressure
Appendix E: Decontamination Procedures
Appendix F: Glossary



Understanding Vital Body Functions

1-3. Respiration and Blood Circulation

Respiration (inhalation and exhalation) and blood circulation are vital body functions. Interruption of either of these two functions need not be fatal IF appropriate first aid measures are correctly applied.

a. Respiration. When a person inhales, oxygen is taken into the body and when he exhales, carbon dioxide is expelled from the body--this is respiration. Respiration involves the--

  • Airway (nose, mouth, throat, voice box, windpipe, and bronchial tree). The canal through which air passes to and from the lungs.

  • Lungs (two elastic organs made up of thousands of tiny air spaces and covered by an airtight membrane).

  • Chest cage (formed by the muscle-connected ribs which join the spine in back and the breastbone in front). The top part of the chest cage is closed by the structure of the neck, and the bottom part is separated from the abdominal cavity by a large dome-shaped muscle called the diaphragm (Figure 1-1). The diaphragm and rib muscles, which are under the control of the respiratory center in the brain, automatically contract and relax. Contraction increases and relaxation decreases the size of the chest cage.

When the chest cage increases and then decreases, the air pressure in the lungs is first less and then more than the atmospheric pressure, thus causing the air to rush in and out of the lungs to equalize the pressure. This cycle of inhaling and exhaling is repeated about 12 to 18 times per minute.

b. Blood Circulation. The heart and the blood vessels (arteries, veins, and capillaries) circulate blood through the body tissues. The heart is divided into two separate halves, each acting as a pump. The left side pumps oxygenated blood (bright red) through the arteries into the capillaries; nutrients and oxygen pass from the blood through the walls of the capillaries into the cells. At the same time waste products and carbon dioxide enter the capillaries. From the capillaries the oxygen poor blood is carried through the veins to the right side of the heart and then into the lungs where it expels carbon dioxide and picks up oxygen. Blood in the veins is dark red because of its low oxygen content. Blood does not flow through the veins in spurts as it does through the arteries.

    (1) Heartbeat. The heart functions as a pump to circulate the blood continuously through the blood vessels to all parts of the body. It contracts, forcing the blood from its chambers; then it relaxes, permitting its chambers to refill with blood. The rhythmical cycle of contraction and relaxation is called the heartbeat. The normal heartbeat is from 60 to 80 beats per minute.

    (2) Pulse. The heartbeat causes a rhythmical expansion and contraction of the arteries as it forces blood through them. This cycle of expansion and contraction can be felt (monitored) at various body points and is called the pulse. The common points for checking the pulse are at the side of the neck (carotid), the groin (femoral), the wrist (radial), and the ankle (posterial tibial).

      (a) Neck (carotid) pulse. To check the neck (carotid) pulse, feel for a pulse on the side of the casualty's neck closest to you by placing the tips of your first two fingers beside his Adam's apple (Figure 1-2).

      (b) Groin (femoral) pulse. To check the groin (femoral) pulse, press the tips of two fingers into the middle of the groin (Figure 1-3).

      (c) Wrist (radial) pulse. To check the wrist (radial) pulse, place your first two fingers on the thumb side of the casualty's wrist (Figure 1-4).

      (d) Ankle (posterial tibial) pulse. To check the ankle (posterial tibial) pulse, place your first two fingers on the inside of the ankle ().

      NOTE

      DO NOT use your thumb to check a casualty's pulse because you may
      confuse your pulse beat with that of the casualty.

1-4. Adverse Conditions

a. Lack of Oxygen. Human life cannot exist without a continuous intake of oxygen. Lack of oxygen rapidly leads to death. First aid involves knowing how to OPEN THE AIRWAY AND RESTORE BREATHING AND HEARTBEAT (Chapter 2, Section I).

b. Bleeding. Human life cannot continue without an adequate volume of blood to carry oxygen to the tissues. An important first aid measure is to STOP THE BLEEDING to prevent loss of blood (Chapter 2, Section II).

c. Shock. Shock means there is inadequate blood flow to the vital tissues and organs. Shock that remains uncorrected may result in death even though the injury or condition causing the shock would not otherwise be fatal. Shock can result from many causes, such as loss of blood, loss of fluid from deep burns, pain, and reaction to the sight of a wound or blood. First aid includes PREVENTING SHOCK, since the casualty's chances of survival are much greater if he does not develop shock (Chapter 2, Section III).

d. Infection. Recovery from a severe injury or a wound depends largely upon how well the injury or wound was initially protected. Infections result from the multiplication and growth (spread) of germs (bacteria: harmful microscopic organisms). Since harmful bacteria are in the air and on the skin and clothing, some of these organisms will immediately invade (contaminate) a break in the skin or an open wound. The objective is to KEEP ADDITIONAL GERMS OUT OF THE WOUND. A good working knowledge of basic first aid measures also includes knowing how to dress the wound to avoid infection or additional contamination (Chapters 2 and 3).

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