Digestive System

Mechanisms for Swallowing

1. Oral Preparatory Phase 2. Oral Transit Phase 3. Pharyngeal Phase 4. Esophageal Phase

Mechanisms of Defecation

Defecation, also called bowel movement, the act of eliminating solid or semisolid waste materials (feces) from the digestive tract. In human beings, wastes are usually removed once or twice daily, but the frequency can vary from several times daily to three times weekly and remain within normal limits. Muscular contractions (peristaltic waves) in the walls of the colon move fecal material through the digestive tract to the rectum.

Appendix

Normally, the appendix sits in the lower right abdomen. The function of the appendix is unknown. One theory is that the appendix acts as a storehouse for good bacteria, "rebooting" the digestive system after diarrheal illnesses. Other experts believe the appendix is just a useless remnant from our evolutionary past.

Structures of the Mouth

Parts of the mouth include the lips, vestibule, mouth cavity, gums, teeth, hard and soft palate, tongue and salivary glands. The mouth is also known as the oral cavity or the buccal cavity.

Alimentary Canal

The Alimentary Canal is made up of; The mouth, the pharynx, the esophagus, the stomach, the small intestine and the large intestine. The wall is made up of the serosa, muscularis, sub-mucosa, mucosa, and the lumen.

Anus

The anus is the last part of the digestive tract. It is a 2-inch long canal consisting of the pelvic floor muscles and the two anal sphincters (internal and external). The lining of the upper anus is specialized to detect rectal contents. It lets you know whether the contents are liquid, gas, or solid.

Describe how digestive secretions are regulators

The digestive system is controlled by both nerves, and hormones. All of the enzymes and secretions produced work in ways to balance each other out in order to protect the human body. Hormone Regulators are the cells in the lining of the stomach and small intestine produce and release hormones that control the functions of the digestive system. These hormones stimulate production of digestive juices and regulate appetite.

Esophagus

The esophagus seems to have only one important function in the body - to carry food, liquids, and saliva from the mouth to the stomach. The stomach then acts as a container to start digestion and pump food and liquids into the intestines in a controlled process.

Jejunum

The lining of the jejunum is specialized for the absorption, by enterocytes, of small nutrient particles which have been previously digested by enzymes in the duodenum.

Liver

The liver also detoxifies chemicals and metabolizes drugs. As it does so, the liver secretes bile that ends up back in the intestines. The liver also makes proteins important for blood clotting and other functions.

Stomach

The main function of the stomach is to break down and digest food in order to extract necessary nutrients from what you have eaten. In order for this to happen, it is necessary that the stomach, the digestive glands and the intestines must produce various enzymes, including pepsin, and acid.

Large Intestine

The major function of the large intestine is to absorb water from the remaining indigestible food matter and transmit the useless waste material from the body.

Mouth

The mouth is the beginning of the digestive tract; and, in fact, digestion starts here when taking the first bite of food. Chewing breaks the food into pieces that are more easily digested, while saliva mixes with food to begin the process of breaking it down into a form your body can absorb and use.

Pancreas

It is part of the digestive system and produces important enzymes and hormones that help break down foods. The pancreas has an endocrine function because it releases juices directly into the bloodstream, and it has an exocrine function because it releases juices into ducts.

Teeth

-Incisors. Incisors are the eight teeth in the front and center of your mouth (four on top and four on bottom). These are the teeth that you use to take bites of your food. Incisors are usually the first teeth to erupt, at around 6 months of age for your first set of teeth, and between 6 and 8 years of age for your adult set. -Canines. Your four canines are the next type of teeth to develop. These are your sharpest teeth and are used for ripping and tearing food apart. Primary canines generally appear between 16 and 20 months of age with the upper canines coming in just ahead of the lower canines. In permanent teeth, the order is reversed. Lower canines erupt around age 9 with the uppers arriving between 11 and 12 years of age. -Premolars. Premolars, or bicuspids, are used for chewing and grinding food. You have four premolars on each side of your mouth, two on the upper and two on the lower jaw. The first premolars appear around age 10 and the second premolars arrive about a year later. -Molars. Primary molars are also used for chewing and grinding food. These appear between 12 and 15 months of age. These molars, also known as decidious molars, are replaced by the first and second permanent premolars (four upper and four lower). The permanent molars do not replace, but come in behind the primary teeth. The first molars erupt around 6 years of age (before the primary molars fall out) while the second molars come in between 11 and 13 years of age. -Third molars. Third molars are commonly known as wisdom teeth. These are the last teeth to develop and do not typically erupt until age 18 to 20, and some people never develop third molars at all. For those who do, these molars may cause crowding and need to be removed.

Rectum

The rectum is the last straight section of the large intestine before reaching the anus. The anus is the opening at the lower end of the digestive tract that controls the expulsion of feces. Read on to learn more about the rectum and anus, and their role in digestion.

Salivary Glands

The salivary glands produce saliva, which keeps the mouth and other parts of the digestive system moist. It also helps break down carbohydrates (with salivary amylase, formerly known as ptyalin) and lubricates the passage of food down from the oro-pharynx to the esophagus to the stomach.

Small Intestine

The small intestine is the part of the intestines where 90% of the digestion and absorption of food occurs, the other 10% taking place in the stomach and large intestine. The main function of the small intestine is absorption of nutrients and minerals from food.

Gall Bladder

The gallbladder is a small storage organ located inferior and posterior to the liver. Though small in size, the gallbladder plays an important role in our digestion of food. The gallbladder holds bile produced in the liver until it is needed for digesting fatty foods in the duodenum of the small intestine.