First aid manual.

  • Great Britain. Civil Defence Department.
Date:
1950
Catalogue details

Licence: Public Domain Mark

Credit: First aid manual. Source: Wellcome Collection.

    13/212 (page 3)
    muscles.” Similarly, many of the vital movements of the body con- tinue, waking or sleeping, independent of our will and this movement is performed by what is known as “ involuntary muscle.” This involuntary muscle is found in the substance or walls of all the tissues and organs in which action is automatic, e.g., in the intestines, and in the arteries, or it may itself form a complete structure or organ such as the heart. (c) The Circulatory (Blood) System The circulatory system is the body’s transport organisation in which the carrying is done by the blood. The heart which is a strong muscular bag acts as a pump and drives the blood round and round the body. The blood travels from the heart in thick-walled tubes known as “arteries.” These divide and subdivide until their terminal branches are nothing more than minute thin-walled twigs called “* capillaries.” Through the thin walls of these capillaries the blood is able to pass the substances it has brought to build up the tissues, and to collect unwanted material or waste products from the tissue cells. The blood having effected this exchange of materials continues its course into minute thin-walled tubes which join together to form larger and larger tubes known as “ veins.” Through these veins the blood is carried back to the heart. It will thus be understood that capillaries form a network of small blood vessels which joins the terminations of the arteries to the commencement of the veins. The substances which the blood carries to the tissue cells are necessary for their life, growth and health. They comprise oxygen which the blood has collected in its passage through the lungs, food substances from the stomach and intestines, and various body juices from other organs known as “ glands” (See the Glandular System, page 5(/),. As it passes through the lungs the blood gets rid of an excess of unwanted gas (carbon dioxide) which is breathed out from the lungs ‘into the air. Other impurities are filtered off from it as it passes through the kidneys, skin and bowels and are passed out of the body as water (urine), sweat, and motions (faeces). The blood has many other functions but these are dealt with in detail in the appropriate chapters (See Chapter VI). (d) The (Breathing) Respiratory System Respiration consists of the alternate drawing in of air and of breathing it out again. When a person takes a breath (inspiration), air enters through the nose and mouth and passes down the windpipe (trachea) into the lungs. Inspiration is a muscular act and the size of the cavity of the chest is increased by the amount of air taken in. When a person breathes out (expiration), the chest and lungs return to their previous size by their own elasticity and the air is expelled from the lungs through the air passages. A more detailed description of this system will be found in Chapter XIV. (e) The Digestive or Alimentary System This system deals with the use and disposal of food, from the time it is taken into the mouth until it has been converted into substances which can be absorbed into the blood for tissue nourishment, or if unsuitable are passed along the bowel and got rid of by defaecation.