Glands and the Work of Excretion : Part 3

Physiology and Hygiene for Secondary Schools
by Francis M. Walters

(Page 15 of 26)

The Perspiratory Glands. - The perspiratory, or sweat, glands are located in the skin. They belong to the type of simple tubular glands and are very numerous over the entire surface of the body. A typical sweat gland consists of a tube which, starting at the surface of the cuticle, penetrates to the under portion of the true skin and there forms a ball-shaped coil. The coiled extremity, which forms the secreting portion, is lined with secreting cells and surrounded by a network of capillaries. The portion of the tube passing from the coil to the surface serves as a duct.

The sweat glands secrete a thin, colorless fluid, called perspiration, or sweat. This consists chiefly of water, but contains a small percent of salts and of urea. The excretory work of these glands seems not to be so great as was formerly supposed, but they supplement in a practical way the work of the kidneys and, during diseases of these organs, show an increase in excretory function to a marked degree. The perspiration also aids in the regulation of the temperature of the body.

Excretory Work of the Lungs. - While the lungs cannot be regarded as glands, they do a work in the removal of waste from the body which must be considered in the general process of excretion. They are especially adapted to the removal of gaseous substances from the blood, and it is through them that most of the carbon dioxide leaves the body. The lungs remove also a considerable quantity of water. This is of course in the gaseous form, being known as water vapor.

Ductless Glands and Internal Secretion. - Midway in function between the glands that secrete useful liquids and those that remove waste materials from the blood is a class of bodies, found at various places, known as the ductless glands. They are so named from their having the general form of glands and from the fact that they have no external openings or ducts. They prepare special materials which are passed into the blood and which are supposed to exert some beneficial effect either upon the blood or upon the tissues through which the blood circulates. The most important of the ductless glands are the thyroid gland, located in the neck; the suprarenal bodies, situated one just over each kidney; and the thymus gland, a temporary gland in the upper part of the chest. The spleen and the lymphatic glands are also classed with the ductless glands. The liver, the pancreas, and (according to some authorities) the kidneys, in addition to their external secretions, produce materials that pass into the blood. They perform in this way a function like that of the ductless glands. The work of glands in preparing substances that enter the blood is known as internal secretion.

Quantity of Excretory Products. - If the weight of the normal body be taken at intervals, after growth has been attained, there will be found to be practically no gain or loss from time to time. This shows that materials are leaving the body as fast as they enter and that the tissues are being torn down as fast as they are built up. It also shows that substances do not remain in the body permanently, but only so long perhaps as is necessary for them to give up their energy, or serve some additional purpose in the ever changing protoplasm. The excretory organs then remove from the body a quantity of material that is equal in weight to the materials absorbed by the organs of digestion and respiration. This is estimated for the average individual to be about five pounds daily. The passage of waste from the body is summarized in Table III.

Table Iii. The Passage Of Waste Materials From The Body Materials State How Formed Condition in How Removed in the Body the Blood from the Blood Carbon Gas By the Dissolved in Separated dioxide oxidation of the Plasma from the carbon and in loose blood at the of proteins, combination alveoli of carbohydrates, with salts the lungs and fats. in the and then blood. forced through the air passages into the atmosphere. Urea Solid By the Dissolved in Removed by oxidation in the Plasma. the liver of uriniferous nitrogenous tubules of compounds. the kidneys and to a small extent by the respiratory glands. Water Liquid By the As water. Removed by oxidation of all the hydrogen organs of proteins, excretion, carbohydrates, but in the and fats. largest Amount formed quantities in the body is by the small. kidneys and the skin. Salts Solid Dissolved in By the Plasma. kidneys, liver, and skin.

Hygiene

The separation of wastes from the body has such a close relation to the health that all conditions affecting it should receive the most careful attention. Their retention beyond the time when they should be discharged undoubtedly does harm and is the cause of many bodily disorders.

Value of Water. - As a rule the work of excretion is aided by drinking freely of pure water. As water is the natural dissolver and transporter of materials in the body, it is generally conceded by hygienists and physicians that the taking of plenty of water is a healthful practice. People do not as a rule drink a sufficient amount of water, about three pints per day being required by the average adult, in addition to that contained in the food. Most of the water should, of course, be taken between meals, although the sipping of a small amount during meals does not interfere with digestion. As stated elsewhere, the taking of a cup of water on retiring at night and again on rising in the morning is very generally recommended.

Protection of Kidneys and Liver. - The kidneys and liver are closely related in their work and in many instances are injured or benefited by the same causes. Both, as already stated, are liable to injury from an excess of protein food, especially meats, and also by a condition of inactivity of the bowels. The free use of alcohol also has an injurious effect on both of these organs. On the other hand, increasing the activity of the skin has a beneficial effect upon them, especially the kidneys. Exercise and bathing, which tend to make the skin more active, are valuable aids both in ridding the body of impurities and in lessening the work of the other excretory organs. One having a disease of the kidneys, however, needs to exercise great care in bathing on account of the bad results which follow getting chilled.

Special Care after Certain Diseases. - Certain diseases, as measles, diphtheria, scarlet fever, and typhoid fever, sometimes have the effect of weakening the kidneys (and other vital organs) and of starting disease in them. When this occurs it is usually the result of exposure or of over-exertion while the body is in a weakened condition. Severe chilling at such a time, by driving blood from the surface to the parts within, often causes inflammation of the kidneys. On recovering from any wasting disease one should exercise great caution both in resuming his regular work and in exposing his body to wet or cold.

D.C. Heath and Co. - Publishers
Original copyright 1909