Digestive process

DIGESTIVE PROCESS

Aceves Olivas José RicardoDe la Cruz Espinoza José Eduardo

Hernández Vázquez GénesisSalazar Sánchez Estefany Carolina

II-7

Mouth• In the mouth we have the teeth, tongue and salivary glands.

• The denture compose 32 pieces in adults.• The teeth are formed by a hard, enamel substance and are housed in

the jaws.• Used to grind food with some movements called chewing, sometimes

when no food remains are removed, holes occur in the enamel called caries.

The tongue is a muscle that propels the food bolus into the pharynx.Also it lies onthe tongue taste, for her distinguish the flavors.

The salivary glands are glands located under the tongue and below the jaw just below the ears. Also produce saliva to moinsten the cud. Are substances that begin the transformatios of some foods.

Saliva is a watery substance located in the mouths of animals, secreted by the salivary glands. Human saliva is 99.5% water, while the other 0.5% consists of electrolytes, mucus, glycoproteins, enzymes (lysozyme), antibacterial, and bacteria compounds.

In the mouth the digestionof food begins.

Esophagus• Is a muscular tube, about 25 cm long and 2 cm in

diameter, that carries food from the pharynx to the stomach.

• The esophagus normally has three narrowings: -Cervical narrowing

-Thoracic narrowing-Phrenic narrowing

The esophagus:• Has an inner circular muscle layer and outer longitudinal.

• Finish entering the stomach by gastric cardia orifice at level of seventh costal cartilage left and thoracic vertebra number 11.

• The abdominal esophagus is separated from the fundus of the stomach through the notch of the cardia.

The back side of the abdominal esophagus is covered by peritoneum of the omental pouch, which covers the back of the stomach.

Fast food passes through the esophagus due to the peristaltic action of their muscles, with the aid of gravity without espender it.

• The stomach is a muscular organ located on the left side of the upper abdomen. The stomach receives food from the esophagus. the stomach is divided into four sections: cardia, fundus, body and pylorus.

Stomach

• In the stomachs starts the protein digestion, Parietal cells secrete HCl, chief cells of the gastric glands to secrete pepsinogen, Hydrochloric acid activates pepsinogen to pepsin.

The small intestine, which is about 20 feet long, is so named because its diameter is much smaller than that of the large intestine. The small intestine has three regions, called the duodenum, the jejunum, and the ileum

Small Intestine

• Takes about 4 – 8 hrs to complete its journey.• Mucosa (inner wall) – secretes several enzymes that acts

on the food.• Where the pancreatic enzymes are emptied into.• Digested nutrients are absorbed through intestinal walls.• Absorbed materials cross the mucosa into the blood then

other parts of the body for storage or further chemical change.

The small intestine extends from the pyloric sphincter to the ileocecal valve, where it empties into the large intestine. The small intestine finishes the process of digestion, absorbs the nutrients, and passes the residue on to the large intestine. The liver, gallbladder, and pancreas are accessory organs of the digestive system that are closely associated with the small intestine.

The most important factor for regulating secretions in the small intestine is the presence of chyme. This is largely a local reflex action in response to chemical and mechanical irritation from the chyme and in response to distention of the intestinal wall. This is a direct reflex action, thus the greater the amount of chyme, the greater the secretion.

Duodenum• The duodenum is the first and shortest segment of the

small intestine. It receives partially digested food (known as chyme) from the stomach and plays a vital role in the chemical digestion of chyme in preparation for absorption in the small intestine. Many chemical secretions from the pancreas, liver and gallbladder mix with the chyme in the duodenum to facilitate chemical digestion.

• Located inferior to the stomach, the duodenum is a 10-12 inch (25-30 cm) long C-shaped, hollow tube. The duodenum is a part of the gastrointestinal tract, attached to the pyloric sphincter of the stomach on its superior end and to the jejunum of the small intestine on its inferior end

After being stored and mixed with hydrochloric acid in the stomach for about 30 to 60 minutes, chyme slowly enters the duodenum through the pyloric sphincter. Next, Brunner’s glands in the mucosa of the duodenum secrete alkaline mucus containing a high concentration of bicarbonate ions to neutralize the hydrochloric acid present in the chyme. This alkaline mucus both protects the walls of the duodenum and helps the chyme to reach a pH conducive to chemical digestion in the small intestine.

Upon reaching the ampulla of Vater in the middle of the duodenum, chyme is mixed with bile from the liver and gallbladder, as well as pancreatic juice produced by the pancreas. These secretions complete the process of chemical digestion that began in the mouth and stomach by breaking complex macromolecules into their basic units. Bile produced in the liver and stored in the gallbladder acts as an emulsifier, breaking lipids into smaller globules to increase their surface area. Pancreatic juice contains many enzymes to break carbohydrates, lipids, proteins and nucleic acids into their monomer subunits. 

It secretes bile which is stored in the gall bladder.Bile breaks down fats into tiny droplets through emulsification.

Roles:• Regulates sugar/glucose• Storage of blood• Detoxification• Generation of heat

Liver

• The gallbladder is a pear-shaped sac that is attached to the visceral surface of the liver by the cystic duct. The principal function of the gallbladder is to serve as a storage reservoir for bile.

Gallbladder

Pancreas

Is a spongy, tube-shaped organ about 6 inches long. It is located in the back of the abdomen, behind the stomach. The pancreas produces a juice containing several enzymes that break down carbohydrates, fats, and proteins in food. including trypsinogen, chymotrypsinogen, elastase, carboxypeptidase, pancreatic lipase, nucleases and amylase.The pancreas delivers digestive juice to the small intestine through small tubes called ducts.

Pancreatic juice is alkaline in nature due to the high concentration of bicarbonate ions. Bicarbonate is useful in neutralizing the acidic gastric acid, allowing for effective enzymic action.Pancreatic juice secretion is regulated by the hormones secretin and cholecystokinin, which is produced by the walls of the duodenum

JejunumThe jejunum is the second part of the small intestine. After food is broken down in the duodenum, it moves to the jejunum, where the inside walls absorb the food's nutrients. The inside walls of the jejunum have many circular folds, which make its surface area large enough to absorb all of the nutrients that the body needs.

Absorption

• It occurs within in finger-like projection known as Villi.

• Amino acids and simple sugars like glucose and fructose diffuse through thin Epithelial cells into the blood capillaries.

Villi

•Fatty acids and glycerol enter the Lacteal into the lymphatic system then finally into the blood system through the Innominate vein.

IleumThe ileum is the third part of the small intestine. It absorbs bile acids, which are returned to the liver to be made into more bile, then stored in the gallbladder for future use in the duodenum. The ileum also absorbs vitamin B12, which the body uses to make nerve cells and red blood cells.

The large intestine The large intestine takes about 16 hours to finish the digestion of the food. It removes water and any remaining absorbable nutrients from the food before sending the indigestible matter to the rectum. The colon absorbs vitamins that are created by the colonic bacteria, such as vitamin K,  vitamin B12, thiamine and riboflavin. It also compacts feces, and stores fecal matter in the rectum until it can be discharged via the anus in defecation.

The large intestine also secretes K+ and Cl-.Chloride secretion increases in cystic fibrosis. Recycling of various nutrients takes place in colon. 

• By the time the chyme has reached this tube, most nutrients and 90% of the water have been absorbed by the body. At this point some electrolytes like sodium, magnesium, and chloride are left as well as indigestible parts of ingested food.

• As the chyme moves through the large intestine, most of the remaining water is removed, while the chyme is mixed with mucus and bacteria (known as gut flora), and becomes feces. 

• The ascending colon receives fecal material as a liquid. The muscles of the colon then move the watery waste material forward and slowly absorb all the excess water. The stools gradually solidify as they move along into the descending colon.