جهاز الهضم .. في جسم الانسان .. كتاب في سبيل موسوعة علمية .. الدكتور أحمد ذكي

Digestive system...in the human body

It is a long tube that sometimes narrows and sometimes bulges. The mouth, the throat, the esophagus, the stomach, the small intestine, the large intestine, and the colon. The food passes through it, and it digests it with effective chemical substances, known as enzymes, that change the chemistry of this food, regardless of its types, and transform it into substances that enable the digestive system to absorb them and then enter the body to benefit from them.

As for what secretes enzymes, they are glands that supply this digestive system or are cells in it specialized for that. The digestive system also absorbs the digested food. As for the food that is not digested or absorbed, it comes out as feces.

Here we talk briefly about the glands and cells and the enzymes they secrete, and about the types of food that enzymes digest, noting that the three major types of food are: proteins (red meat, eggs, etc.), and carbohydrates (starches and sugars together, such as: starch, cane sugar, and milk sugar). , barley sugar), and fats (meat fat, buttermilk, olive oil, and cottonseed oil).

- the mouth :

In the mouth, food is prepared for digestion by grinding and softening with saliva.

The teeth grind, and the tongue and cheeks participate in the kneading.

As for saliva, it is secreted into the mouth by the salivary glands, which are of three types. The first type: the parotid gland. There is one on each side of the face. Its location is in front of and below the ear. It is the gland that, if inflamed, causes the disease known as mumps. The second is a gland under the lower jaw, of which there is one on each side of the face, below the edge of the jaw backwards. The third is the sublingual gland, and their name is:
Indicates their locations.

In addition to these original glands, there are many glands in the walls of the mouth: in the lip, cheeks, gums, and roof of the throat.

The mouth secretes between 1,000 and 1,500 cubic centimeters of saliva per twenty-four hours, and it is a constant secretion to moisturize the mouth, lubricate its parts, and facilitate tongue movements and speech.

Saliva is 99 percent water, and one percent is enzyme, mucin, and salt.

As for the mucus in the saliva, it lubricates the bite while it is ground to make it easier to swallow.

As for the enzyme, which is called oral amylase, it is the one that breaks down starch chemically, simplifying its structure.
It turns it into barley sugar.

The chewed morsel does not remain in the mouth for long and is digested
The starch in it does not last long and is not complete, of course, and if it goes down into the stomach and it contains acid, this acid stops the interaction of this enzyme with the starch, so the starch is not completely dissolved, i.e. digested. However, it may prolapse into the upper arch of the stomach for a while.

In conclusion, most of the work of the mouth in digestion is mechanical, not chemical, which is grinding, kneading, and lubrication to facilitate swallowing.

-Esophagus:

If the vagina is prepared for puberty, it passes through the throat and into the esophagus. During swallowing, the path to the trachea is blocked so that food does not enter it. If something enters it, the person begins coughing violently to expel what has entered it.

The esophagus is a muscular tube that connects from the throat to the stomach. Its length is about a quarter of a meter, and its location is behind the trachea and heart, and in front of the vertebrae of the dorsal chain. The esophagus penetrates the diaphragm, to the left of the vertical line, which is the middle of the body, to reach the stomach.

Swallowing begins as a voluntary action carried out by the tongue and buccal passages. If food enters the throat, the esophagus becomes involuntary, and then a movement described as peristalsis occurs in the esophagus: the muscle of the esophagus contracts behind the morsel and relaxes in front of it, and this is how it continues to do so, advancing it to the stomach. This peristaltic movement includes almost all the tubes of the digestive system. It takes about 10 seconds for the morsel to reach the stomach from the throat. As for
Liquids take between two and four seconds.

The esophagus does not have glands that drain digestive fluids into it. They are nothing but mucous glands scattered in the mucous membrane of the esophagus that secrete mucus for lubrication and protection.