Physiology and Hygiene for Secondary Schools

arrangement. Most of them consist either of tubes or cavities and these are so connected, one with

On account of its length it lies for the most part in coils, the two largest ones being known as the small intestine and the large intestine. Connected with the alimentary canal are t

al, except at the mouth, are distinct from the surrounding tissues and

xillary gland. 7. Esophagus. 8. Stomach. 9. Pancreas. 10. Vermiform appendix. 11. C?cum. 12. Ascending colon. 13. Transverse c

comparative length o

e body that connect with the external surface. It derives its name from the substance which it secretes, called mucus. In structure it resembles the skin, being continuous with the skin where cavities open to the surface. I

tication which are separate and distinct from each other.) As a[pg 140] rule the muscles of this coat are involuntary. They surround the canal as thin sheets and at mo

that occupy the abdominal cavity. This coat is not found above the diaphra

. 1. Transverse colon. 2. Duodenu

l and other abdominal organs and supplies the inner lining of the cavity itself. It is also the means of holding these organs in place, some of them bei

at convenient places outside of the[pg 141] canal and pass their liquids into it by means of small tubes, called ducts. In the canal the food and the digestive fluids come in direct

are necessary and they occur in such an order that those preceding are preparatory to those that follow. These processes are known as mastication, insalivation, deglutition, stomach digestion, and intestinal digestion.

es of the lower jaw below. The mucous membrane lining the mouth is, soft and smooth, being covered with flat epithelial cells. The external opening of the mouth is guarded by the lips, and the soft palate forms a movable p

By the first process the solid food is reduced, by the cutting[pg 142] and grinding action of the teeth, to

th in position in lower jaw. 1. Incisors. 2. Canine. 3. Biscuspids. 4. Molars. C. Upper and lower teeth on one side

n and insalivation is accomplished through organs sit

, while the food is held by the tongue and cheeks between the grinding surfaces. The front teeth are thin and chisel-shaped. They do not meet so squarely as do the back ones, but their edges glide over each othe

is set in a depression in the jaw where it is held firmly in place by a bony substance, known as cement. The part of the tooth exposed above the gum is the crown, the part surroun

ppear about the sixth month, and they disappear from the mouth at intervals from the sixth to the thirteenth year. As they leave, teeth of

ed and double pointed teeth, the bicuspids, and back of the bicuspids are three heavy teeth with irregular grinding surfaces, called the molars (B and C, Fig. 65). Since the molar farthest back in each jaw is us

ng directions of musc

ation the tongue transfers the food from one part of the mouth to another, and, with the aid of the cheeks, holds the food between the rows of teeth. (By an outward pressure

r muscles, which are the heavy muscles in the cheeks, and the temporal muscles, located in the region of the temples, raise the

and the ducts connecti

e, in front of and below the ears. A duct from each gland passes forward along the cheek until it opens in the interior of the mouth, opposite the second molar tooth in the upper jaw. Next in size to the parotids are the submaxillary glands. These are located, one on either side, just below and in

the starch. The ptyalin changes starch into a form of sugar (maltose), while the water in the saliva dissolves the soluble portions of the food. In addition to this the saliva moistens and lubricates the food which it does not dissolve, and prepares it in this way for its pas

heless, necessary for the further digestion of the food. Mastication and insalivation, which are largely mechanical, prepare the food for certain chemical processes by which it is dissolved

able for its openings, seven in number, by means of which it communicates with other cavities and tubes of the body. One of these openings is into the mouth, one into

carefully guarded. This is accomplished through the soft palate and epiglottis, which are operated somewhat as valves. The muscular coat of the pharynx is made up of a series of overlapping muscles whi

part in the thoracic cavity and consists chiefly of a thick mucous lining surrounded by a heavy coat of muscle. The muscula

llows: 1. By the contraction of the muscles of the cheeks, the food ball, or bolus, is pressed into the center of the mouth and upon the up

e opening into the upper pharynx, while the epiglottis is made to close the opening into the larynx. By this means all communication between the food c

successive contractions of muscles, starting at the

7]That it is independent of this force, however, is shown by the fact that o

cells and the duct where the gland opens on to the surface. B. Inner surf

th the esophagus is known as the cardiac orifice and its opening into the small intestine is called the pyloric orifice. It varies greatly in size in different individuals, being on the average from ten to twelve

(Fig. 68). These are of two general kinds and secrete large quantities of a liquid called the gastric juice. When the stomach is empty, the mucous mem

the fibers, the circular layer, the longitudinal layer, and the oblique layer (Fig. 69). The circul

om Morris' Human Anatomy). The lay

rous coat, is a continuation of the peritone

mical action in which the insoluble are changed into soluble substances, and this is followed immediately by the dissolving action of water. The chief substances digested in the sto

e water and include, besides several salts, three active chemical agents-hydrochloric acid, pepsin, and rennin. Pepsin is the enzyme which acts upon proteids, but it is abl

on to digesting proteids, the gastric juice b

gun in the mouth by the saliva.58 This is due to the presence of the

se the fat particles are dissolved away (Fig. 79), and the fat is set free. By this mean

omach. This action is due to the rennin. The curded mass is then acted upon

in of the insoluble mineral salts found in the

e sugar and maltose (double sugars) are converted by the hy

duced to a rather uniform and pulpy mass which is called chyme. Po

. By alternately contracting and relaxing, the different layers of muscle keep the form of the stomach changing-a result which agitates and mixes its

ar band at the pyloric orifice is contracted. At intervals, however, this band relaxes, permitting a part of the contents of the stomach to be fo

ase of poisoning, or if the food for some reason fails to digest, is a necessary though unpleasant operation. It is accomplished by the[pg 151] contraction of all the muscles of the stomach

ine. Illustration also shows arrangement of mu

end it joins the large intestine. It averages a little over an inch in diameter, and gradually diminishes in size from the stomach to the large intestine. The first eight or ten inches form a short curve, known as the duodenum. The upper two fifths of the remainder is called the jejunum, and

rse, or circular, folds which increase its surface and also prevent materials from passing too rapidly through the intestine. One important respect in which the small intestine differs from all other portions of

ers and the outer of longitudinal fibers. These muscles keep the food materials mixed with the juices of the small in

the intestine lies in a fold of the peritoneum, somewhat as an arm in a sling, while the peritoneum, by connecting with the back wall of the abdominal cavity, holds

intestine is supplied by two large glands, the li

vity with organs of

s-the portal vein[pg 154] and the hepatic artery. The portal vein collects the blood from the stomach, intestines, and spleen, and passes it to the liver. This blood is loaded with food materials, but contains little or no oxygen. The hepatic artery, which branches from the aorta, carries to the liver blood rich in oxygen. In the liver

howing the connection of the liver with t

erside of the liver. The bile passes from the gall bladder, and from the right and left lobes of the liver, by three separate ducts. These unite to form a common tube which, uniting

f about 97 per cent of water and 3 per cent of solids.60 The solids include bile pigments, bile salts, a substance called cholesterine,

and absorption of fats. It is claimed also that the bile aids the digestive processes in some general ways-counteracting the acid of the gastric juice, pr

lender portion extends across the abdominal cavity nearly parallel to and behind the lower part of the stomach. It has a length of six or eight inches and weighs fro

mineral salts (the chief of which is sodium carbonate) and four different chemical agents, or enzymes,-trypsin, amylopsin, steapsin, and a milk-curding enzyme. These active constit

ork begun by the saliva. This action is due to the amylo

the work begun by the gastric juice. This is accomplished by th

this work the active

e, somewhat similar to the rennin of

apsin, absorbs water and splits into two substances, recognized as glycerine and fatty acid. This finishes the process so far as the glycerine is concerned, as this is soluble in water; but the fatty acid, which (from certain fats) is insoluble in water,62 requires further treatment. The fatty ac

d in water, but not changed chemically, the mixture being known as an emulsion. While this is believed by some to be an actual process of digesti

ut an alkaline condition in the small intestine and aids in the reduction of cane sugar and maltose to the simple sugars, dextrose and levulose. Since it is difficult to obtain this

ptacle for holding the food while it is being acted upon; it secretes the intestinal juice and mixes the food with the diges

ced food is here absorbed. There is always present, however, a variable amount of materia

meter. It begins at the lower right side of the abdominal cavity, forms a coil which almost completely surrounds the coil of small intestine,

testine. At the ileo-c?cal valve is the

tending from one side a short, slender, and blind tube, called the vermiform appendix. This structure serves no purpose in digestion, but appears to be the rudiment of an organ wh

and the sigmoid flexure, or sigmoid colon. The first three divisions are named from the direction of the movemen

9] It is a nearly straight tube, from six to eight inches in

ucous membrane and in the arrangement of the muscular coat. The mucous membrane presents a smooth appearance and has no villi, while the longitudinal layer of the muscular coat is limited to three narrow bands that extend

coat. 2. Circular layer of muscle. 3. Submucous coat. 4. Mucous m

heir action here, and the dissolved materials also continue to be absorbed. In these respects the work of the large intestine is similar to that of the small intestine. It

, may be here summarized: They supply the necessary force for masticating the food. They propel the food through the canal. They mix the food with the different juices. At certain places they partly or completely close the passag

fail, in the digestive processes, to be reduced to a liquid state. A considerable amount of waste material is also separated from the blood by the glands of digestion (especially the liver), and this is passed from the body with the undigested portions of food.

E OF D

process and children should, for this reason, be taught early to eat properly. Since the majority of the digestive processes are involuntary and the food, after being s

erly masticated, the digestive[pg 161] fluids in the stomach and intestines cannot act upon it to the best advantage. When the food is ca

wed in lumps, but reduced to a finely divided and pulpy mass. This requires time. The one who hurries through the meal is n

nds are excited by the sight, smell, and thought of food and, through taste, by the presence of food in the mouth, has been fully demonstrated. Food that is thoroughly masticated and relished wil

process of digestion seems to justify. The heavy foods (proteids for the most part) are eaten first; after which are taken starchy

igesting without delay. Since these are the main substances acted on in the st

d and satisfies the relish for food. The result of taking sugar first may be to

f the stomach and around the material to be digested. This prevents the ju

e in contact with the gastric juice. This enables the ptyalin of the saliva

as the glands can supply the necessary saliva, the liquid is used to wash the food down. Water or other drinks should be taken after the completion of the meal or when the mouth is completely free from food. Even then it shou

he cultivation of cheerfulness is important for its general hygienic effects, it is of especial value in relation to digestion. Intense emotions, either during or following the[pg 163] meal, should if possible be avoided. T

ervation of the teeth, even when naturally poor, as long as one has need of them. To preserve the teeth they must be kept clean. They should be washed at least once a day with a soft-bristled brush, and small particles of food, lodg

t such places before they become large. On account of the expense, pain, and inconvenience there is a tendency to put off dental work which one knows ought to be done. Perhaps in no other

. It is[pg 164] nature's means of indicating the needs of the body. The natural appetite may be spoiled, however, by overeating and by the use of highly seasoned foods, or by indulging in stimulants during th

diminishing the likelihood of introducing disease germs into the body; and it makes the food more palatable, thereby supplying a necessary stimulus to the digestive glands. While the methods employed in the

etion. It may also lead to the accumulation of burdensome fat and of harmful wastes. On the other hand, the taking of too little food impoverishes the blood and weakens the entire body. As a rule, however, more people eat too muc

heavy meal and two light ones. Either plan gives the organs of digestion more time to rest and diminishes the liability of overeating. On the other hand, those doing heavy muscular work can hardly derive the energy which they need from less than three good meals a day. Though no definite rule can be laid down, there is involved a hygienic principle which all

disease germs, as stated above, is thorough cooking. Too much care cannot be exercised with reference to the water for drinking purposes. Water which is not perfectly clear, which smells of decaying material, or which forms a sediment on standing is usually not fit to drink.

t be overlooked. Frequently, through lack of exercise, negligence in evacuating the bowels, or other causes, a weakened condition of the canal is induced whic

ecuring the necessary movements. 2. Drink a cup of cold water on rising in the morning and on retiring at night. 3. Eat generously of fruits and other coarse foods, such as corn bread, oatmeal, hominy, cabb

work of digestion. Large doses retard the action of enzymes, inflame the mucous lining of the stomach,65 and[pg 167] bring about a diseased condition of the liver. It may be noted

little of the tannin. (They should be made without continued boiling or steeping.) The caffeine may do harm through its stimulating effect upon the nervous system (page 56) and through the introduction of a special waste into the body. In chemical composition caffeine closely resembles a waste, called uric acid, and in the body is converted in

s. The general plan of digestion is that of passing the food through the canal, beginning with the mouth, and of acting on it at various places, with the final result of reducing most of it to the liquid state. The digestive fluids[pg 168] supply water which acts as a solvent and carries th

pose of digestion. How does digeste

alimentary canal in the order in

s digestion is carried on

f the food? Why should mastication pre

work of the ton

poses served by

small intestine as the most impo

ction of what liquids, are fats

the pancreatic juice? What is

e muscles of the stomach, the mouth,

are derived from the

vantages of drin

meal can be thoroughly masticated in fifteen minutes,

rlapping of meals? What bad

TICA

ans. Find the connection of the esophagus with the stomach, of the stomach with the small intestine, and of the small inte

ection of the abdomen of some small animal is necessary. On account of unpleasant features likely

monstrating the abdo

-grown cat is perhaps the best available material. It should be killed with chloroform,

ollowing materials will be needed during the dissection, and should be kept near at hand: a sharp knife with a good point, a pair of heavy scissors, a vessel of water, some cotton or a damp sponge, and some fine cord

portion of the abdomen, and sideward as far as convenient. Tack the loosened abdominal walls to the board, and proceed to study the expose

en, and intestines, and then, by pushing the intest

er, from which a small tube leads to the small intestine. Observe the portal vein as it passes into [pg 170] the

and joins the stomach. Find next the union of the stomach with the small intestine. Then, by ca

ves the stomach, find the pancreas. Note its color, size,

of the abdomen. Observe whether it extends back of or in front of the kidneys, the aorta, and the inferior vena cava. Find where it leaves the wall as a

gland. This is the beginning of the thoracic duct and is called the receptacle of the chyle. From th

on removed. Split it open for a part of its length, and wash out its contents. Observe its coats. Place it in a shallow vessel c

the large. Split them open at the place of union, wa

on of each kidney with the aorta and the inferior vena cava by the renal artery and the renal vein. Find a slender tube, the ureter, running from each kidney to the bl

from the dentist a collection of differe

th, noting general shape, cutting or grinding surfaces,

wise, and another in two crosswise, and smooth the cut surfaces with fine emery or sand paper. Exami

tooth appears to decay most readily? Why is it neces

ne part hydrochloric acid to four parts water, and by leaving a second tooth for a couple o

water. Into one put a lump of rock salt. Into the other place an equal am

soda. Taste each liquid, noting the sour taste of the acid, and the alkaline taste of the soda. Hold a piece of red litmus paper in the soda solution, noting that it is turned blue. Then hold a piece of blu

change in the color of the paper. Repeat, using blue litmus paper. What effect, if any,

f water and heating the mixture to boiling. Place some of this in a test tube and thin it by adding more water. Then add a small d

to small amounts of fresh starch solution in two test tubes. Let the tubes stand for five or ten minutes s

few drops of a very dilute solution of copper sulphate. Then add sodium (or potassium) hydroxide, a few drops at a time, until the precipitate which first forms dissolves and turns a deep bl

tely dissolves and observe that it gradually acquires a s

h hydrochloric acid to give a slightly sour taste. Place in the artificial gastric juice thus prepared some boiled white of egg which has been finely divided by pressing it through a piece of wire gauze. Also dr

e of the tubes add alcohol from a burette as follows: (1) .5 c.c., (2) 1 c.c., (3) 1.5 c.c., (4) 2 c.c., and (5) 3 c.c., leaving one tube without alcohol. Now add to each tube about 1/4 gram of finely divided white of egg from the

g