Teeth, rigid structures rich in calcium, attached to the jaws, have as their main function mastication, but also help in speech and protection of the mouth.

The first dentition, in which the teeth are called “milk teeth”, corresponds to 20 teeth whose birth will cease until approximately 2 years of age. As the child grows, their jaws also grow, making room for new teeth. At approximately 6 years of age, the child begins his permanent dentition, which consists of replacing his milk teeth with permanent teeth and the emergence of other permanent ones. Between 15 and 25 years of age, wisdom teeth may appear, making up 32 teeth: 4 incisors, 2 canines, 4 premolars and 6 molars in the upper portion of the jaws and the same amount in the lower portion.

The incisor, canine, premolar, and molar teeth are the four tooth kinds seen in humans. The incisors are located at the front of the mouth and the shape of their crown makes it easier to cut food. The canine teeth are pointed and allow the food to be "teared". The premolars and molars are located at the back of the mouth and have a food-crushing function.

Enamel is the most external and compact region of the tooth. Under it is the dentin and the pulp chamber. Cementum separates the root from the ligament that holds the root and connects the tooth to the jaw. The apex is the region where the tooth ends and is where the blood vessels, connective tissue and nerves are inserted.

Function of each tooth in Digestion

The dental arch is divided into four groups and each tooth in our mouth has a specific function. Know its functions and nomenclatures!

Each tooth in our mouth has a specific function. The anatomy of the oral cavity is perfect not only for chewing, but also for our speech and food swallowing. The mouth, as the “gateway” for food, plays an important role in the entire functioning of the organism.

Humans have, in their first dentition, 20 milk teeth (10 on the top and 10 on the bottom). After the age of 6, baby teeth start to fall out and permanent teeth appear. This is formed by 32 teeth (16 upper and 16 lower). In this way, the human being has 4 incisors, 2 canines, 4 premolars and 6 molars in the upper part and the same amount in the lower part.

Each group of teeth serves something different, having its own characteristics for chewing.

Around the age of six months, the first milk teeth come in - by the age of three, all 20 have already developed. The fall of milk teeth, being replaced by permanent ones, occurs from the age of six. Counting the wisdom teeth, an adult has a total of 32 teeth in the mouth.

Understand now what the function of teeth is. They are divided into groups defined by their anatomical and functional characteristics:

Incisors: They are divided between the central and lateral incisors, and are located in the front part of the mouth, four in the upper arch and four in the lower. The main function of the incisor teeth is to cut food, both because of their location in the oral cavity and because of their shape.

Canines: These are the pointed teeth, located next to the incisors. There are two canine teeth in the upper arch and two in the lower arch, and their main function is to tear food.

Premolars: Located right after the canine teeth, there are a total of eight premolars, four in each arch. Children do not have premolars, which are only permanent. The function of the premolar teeth is to grind food.

Molars: At the bottom of the mouth are located the molar teeth, also four in the upper arch and four in the lower arch. They are used to grind and chew food, corresponding to the last process that food goes through before being swallowed.

Wisdom or third molars: There are four wisdom teeth in all, but many people do not have them, or only have a few of them. Because they are the last to be born (when the person is about 20 years old), and because they have no relevant function, it is common for them to be extracted so as not to harm the alignment of the other teeth. However, the need for extraction depends a lot on the position in which the wisdom teeth are born, and there are people who keep them without problems.

Because of their shape, which can make cleaning difficult, premolar and molar teeth are the ones most subject to cavities. Therefore, they need special attention when brushing.

Supernumerary or supernumerary teeth

Sometimes teeth develop outside of their normal process, and an example of this is supernumerary or supernumerary teeth. The usual number of teeth in an adult's mouth is 32, but some extra teeth may appear. The Department of Dentistry at the University of Missouri-Kansas City suggests that the most common type of supernumerary tooth is an extra incisor located between the two central incisors. The name of teeth of this type is mesiodens. The second most common type of supernumerary tooth is an extra molar, called a paramolar. It is also possible to develop supernumerary canine teeth.

An Introduction 

The appendix is a tube-shaped pouch located in the lower right area of the belly. It also receives other names such as: cecal appendix, vermiform appendix and vermicular appendix.

It is not considered essential for the body, but its inflammation can cause health problems.

What is the Appendix?

The appendix is a small tubular extension that ends in a blind end. Shaped like a small bag, it is about 10 cm long and connects with the first part of the large intestine.

It is located in the lower right region of the abdomen, in the cecum, which in turn is connected to the first portion of the large intestine.

What is the appendix for?

For a long time, efforts were made to understand the function of the appendix in the body, in which it was believed that the appendix would be a vestigial organ, that is, that with evolution they became out of use due to adaptation to new lifestyles, different of the most primitive ancestors.

Theories that explain the function of the human appendix Despite contrary evidence, based on studies of comparative anatomy in primates, the appendix was considered for a long time as a vestigial structure, that is, a structure that, over the course of evolution, lost its original function . Nowadays there are some theories that explain the function of the human appendix. One argues that the human appendix supports the immune system. When microscopically examining the appendix, the researchers found a significant amount of lymphoid tissue, a tissue that has an abundant amount of lymphocytes .

It is now understood that intestinal bacteria that support digestion and ward off illnesses reside in the appendix. Following investigations into the possibility that the appendix had a role in the digestion of vegetables, this result was reached.

Additionally, according to researchers, the appendix contains a significant number of lymphocytes, which are defense cells that are associated with the immune system.

However, if the appendix is removed, its absence does not cause any damage, anomaly or deficiency to the organism, this being one of the organs of the human body without which you can survive.

Appendix in Digestion

Considered a vestige without function, which only manifests itself to cause appendicitis, this small organ would in fact serve as a shelter for a bacterial flora helping us to digest food. But, in industrialized countries, indeed, this accommodation would be more harmful than useful.

In human anatomy textbooks, the vermiform appendix, or appendix, is described as a diverticulum of the cecum, at the entrance to the large intestine, from 5 to 12 centimeters, without further precision. It is then immediately associated with its inflammation, called appendicitis. In short, the only function of this appendix would be to pose a mortal risk to the individual. From an evolutionary point of view, this would be a curiosity. The understanding of its role is not facilitated by its rarity in mammals. The anatomy of the cecum varies greatly from species to species and this part of the intestine is mostly developed in herbivores.

We know that the appendix manufactures immunoglobulins, and must therefore intervene, in one way or another, in the immune system. But other parts of the body also manufacture immunoglobulins and the removal of the appendix, common in many countries, does not seem to generate complications. The cause is understood: the appendix would be a vestigial organ, a qualifier given to an atrophied anatomical structure which is only the memory of an organ present in distant ancestors.

The role of the appendix in restocking the intestinal flora

Diseases such as dysentery or cholera contaminate the intestine. The only way out is to get rid of the bad microbes. That's where diarrhea occurs. In cases of severe diarrhea, not only are the bad microbes lost, but everything inside the gut, including what is known as the biofilm (a thin, delicate layer made up of microbes, mucus, and immune system molecules) . When leakage of intestinal contents occurs, the beneficial bacteria hidden in the appendix emerge and repopulate the biofilm layer of the intestine before harmful bacteria take hold.

Should you avoid removing the appendix?

 Despite the important role proposed by the team of scientists at Duke University, one should not forget that the appendix has its villainous side. When suffering from inflammation, it can lead to obstruction of the intestines, causing acute appendicitis, which can lead to death.

Therefore, in that case, it should, yes, be removed. But don't worry, severe infections, such as cholera or dysentery, are rare in industrialized nations or regions. People who inhabit these places can live normally without the appendix.

Bacterial flora

Charles Darwin himself looked disdainfully at this outgrowth of the caecum (the first part of the colon), considering that its size and structure prevented it from participating in digestion. Error, say today researchers from Midwestern University, led by Heather Smith say the opposite: the appendix in fact plays a key role in the immune system, which confirms the hypothesis put forward in 2007, by William Parker. The ileocaecal appendix, as its full name implies, is where the bacterial flora of the body resides, claims this Duke University researcher from North Carolina. The bacterial biofilm is removed in cases of diarrhea. The reserve of the appendix then serves, in a way, to replenish the stocks.

Heather Smith's team has, this time, studied the appearance and disappearance of the appendix for 553 mammalian species that lived eleven million years ago and until today. According to her, the appendix would have evolved at least 29 times. This would prove its adaptability; this would not be linked to diets or caused by social factors. And pan on Darwin's beak!

Better still: the statistical study carried out by researchers from Midwestern University highlighted "a correlation between the presence of the appendix and the concentration of lymphoid tissue in the cecum", which "confirms the hypothesis that the appendix has an immunological function”.

Oversized Reaction

In industrialized societies, with a healthy diet and constant hygiene, this kind of indigestion is extremely rare. This is why the removal of the appendix has no effects on health. On the other hand, this role of the appendix could explain the frequency of appendicitis. The reasoning appeals to what is sometimes called the hygienist thesis. Because our modern societies expose us little to pathogenic bacteria, our bodies are ill-prepared to fight against them when we cross their path. The encounter can then more easily lead to a disproportionate reaction, causing allergies in mild cases, or inflammation against more severe attacks. This is what would happen after the intrusion of an enemy bacterium into this protected reserve that would be the appendix, causing a violent reaction and appendicitis.

Appendicitis

Appendicitis is inflammation of the appendix and is common in children, teenagers and young adults.

Its causes are still not well understood. However, obstruction of the intestine with feces or fat is believed to result in the development of inflammation and swelling of the appendix.

With untreated appendix inflammation, it is possible for it to rupture, which can lead to a serious and life-threatening infection.

Salivary Glands  

Salivary glands are structures attached to the human digestive system. They are located in the oral cavity and are responsible for the production of saliva.

They are classified as exocrine glands, with the function of secreting saliva.

Saliva is important for starting the digestion process. It softens food so that it can enter the digestive tract, lubricates food particles, acts as an antibiotic and eliminates some germs.

Saliva in Digestion 

You may have heard that digestion of food begins in the mouth. This statement is made because saliva plays a key role in food processing. The salivary glands are responsible for the production and release of salivary flow in the oral cavity.

Humans, like other animals, have organs called salivary glands, which are located at the beginning of the digestive tract. Three main pairs of salivary glands are present:

- Parotid glands: they are the largest, located in front of the ear pinna, being responsible for producing a large part of the saliva we need. It has lymph nodes inside and is closely related to the facial nerve, responsible for moving the muscles of the face;

- Submandibular glands: they are found below the mandible, with a superficial portion and a deep portion to the mylohyoid muscle, presenting a single channel for saliva drainage to the mouth (as it happens in the parotid gland);

- Sublingual glands: located just under the tongue, also found in pairs (as well as parotid and submandibular glands, composing with these the group of major salivary glands). It produces saliva in smaller quantities than the others, but it has an important role in the beginning of the digestive process. It differs from the previous ones in that it has multiple salivary ducts that drain saliva to the floor of the mouth;

- Minor salivary glands: distributed below the mucosa of the mouth and pharynx, mainly on the palate, inner region of the cheek, floor and pharynx, they complement the saliva production function, being important in the lubrication of the food bolus, helping in chewing and swallowing.

Functions of the Salivary Glands in Digestion 

Salivary glands are structures responsible for producing and secreting saliva. They do this all the time, keeping the oral cavity moist. They also release this flow when there are stimuli (visual, auditory, memory) and while we are eating, to start the digestive process.

Saliva has more than one function in the human body. It keeps the mucous membranes of the upper aerodigestive tract hydrated, ensuring its vitality and protection. It has a direct action on the continuous process of mineralization and demineralization of teeth, so it also influences their health.

When we maintain a good salivary flow, we also guarantee a natural hygiene of the mouth. And we cannot forget that when it is properly balanced, it has the function of maintaining the stability of the oral pH, preventing problems such as cavities and dental erosion.

In addition to all this, we explain that saliva contributes to the process of food digestion. It presents a series of enzymes that start, still in the mouth, the chemical process of digestion. The main one is ptyalin or salivary amylase, responsible for the digestion of starch. There are other enzymes in saliva, as well as a large amount of mineral salts, the most abundant being calcium.

Histology

Salivary glands are made up of clustered grains called acini. From them, branched ducts depart that release saliva to the various points spread throughout the oral cavity.

The salivary gland consists of acini, tubular system and excretory ducts.

There are also two types of secretory cells: serous cells and mucous cells.

Serous cells are pyramidal in shape. They produce proteins and glycoproteins, in general, with enzymatic and antimicrobial activities. In addition, they also secrete water, ions, enzymes and glycoproteins.

The parotid glands are predominantly composed of serous cells.

Mucous cells generally have a tubular shape and are characteristic for accumulating large amounts of mucus. This condition even compresses the cell's organelles and nucleus. The main product of mucous cells is mucins.

Both serous and mucous cells can be found in the sublingual and submaxillary glands.

What problems can affect the salivary glands?

All salivary glands can develop diseases. One of the most common problems is calculus, small stones that form in these structures due to the accumulation of minerals. This problem is called sialolithiasis.

When there is an imbalance in the composition of saliva, or its flow is impaired by dehydration, for example, mineral particles aggregate, giving rise to small stones, which can obstruct the salivary duct and prevent saliva from being secreted into the mouth.

As a result of the obstruction, the salivary gland can become inflamed, a condition that is also triggered by infection with viruses or bacteria (called sialadenitis). In addition to sialolithiasis, this structure can be impaired by autoimmune diseases, such as Sjögren's Syndrome, an immune system disorder that causes dry mouth and swelling of the salivary glands.

We can also notice the appearance of nodules in the salivary glands, which need to be properly evaluated to determine their nature and the need for specific treatment.

To ensure that they always remain healthy, the ideal is to adopt good habits, maintaining a balanced diet, avoiding tobacco, taking care of oral hygiene and ingesting plenty of water. After all, this is the main ingredient used by them to produce saliva.

The salivary glands are responsible for producing saliva, ensuring the health of the oral cavity and, indirectly, a good digestion of food. Therefore, if you notice any change in these structures or any discomfort, look for a Head and Neck Surgeon to be evaluated by a specialist.

Illnesses

Some diseases may be associated with the salivary glands.

The most common symptoms are: swelling of the gland, local pain, reddened skin and changes in saliva composition.

Bacteria and viruses can infect the salivary glands. Some associated diseases are:

Mumps: viral infection that affects the parotid glands.

Sialadenitis: inflammation of the salivary gland resulting from the presence of bacteria or viruses.

Parotitis: inflammation of the parotid glands due to the presence of a virus.

Tumors: Some tumors can form in the salivary glands and lead to cancer.

An Introduction 

Digestive system has specialized organs in the breakdown of food into smaller particles and in the use of nutrients present in them. This system is also responsible for eliminating material that has not been digested. 

The human digestive system is formed by a kind of alimentary canal, which communicates with several accessory glands that release essential substances for the digestion process. Below we will learn more about this important process.

Digestive System Organs 

The human digestive system is formed by the gastrointestinal tract, which is composed of the mouth, pharynx, esophagus, stomach, small intestine and large intestine. Associated with these organs, we have the accessory glands, also called associated glands, which are the salivary glands, the liver and the pancreas.

Parts & Description 

• Upper digestive tube: Mouth, pharynx and esophagus. 

• Middle digestive tract: the duodenum, jejunum, and ileum of the small intestine. 

• Lower digestive tube: Large intestine (cecum, ascending, transverse, descending colon, the sigmoid curve and the rectum). 

• Attached Organs: Salivary glands, teeth, tongue, pancreas, liver and gallbladder.

Mouth 

The digestion process starts in the mouth. In this cavity, the food will undergo the action of the teeth, which act to ensure that the food is cut, crushed and crushed. This stage of digestion is called mechanical digestion, as it does not involve chemical substances that act on the food. In the mechanical digestion carried out by the teeth, the food will only become smaller, ensuring a better action of the enzymes and also aiding in swallowing.

One of the auxiliary glands of this crucial system, the salivary glands, also function in the mouth. These glands are responsible for the secretion of saliva, which acts in chemical digestion. Saliva contains salivary amylase or ptyalin, an enzyme that breaks down carbohydrates. The food, crushed and mixed with saliva, forms an agglomerate called food bolus. 

The tongue is also an important structure present in the mouth, being responsible for helping food to mix with saliva and also for moving the food bolus to the bottom of the oral cavity for swallowing. After leaving the oral cavity, the food goes to the pharynx.

Pharynx 

The pharynx is a membranous muscular tube that communicates with the mouth, through the isthmus of the throat and at the other end with the esophagus. 

To reach the esophagus, food, after being chewed, travels through the entire pharynx, which is a common channel for the digestive system and the respiratory system. 

In the process of swallowing, the soft palate is retracted upwards and the tongue pushes the food into the pharynx, which contracts voluntarily and takes the food to the esophagus. 

The penetration of food into the airways is prevented by the action of the epiglottis, which closes the orifice of communication with the larynx.

Esophagus 

The autonomic nervous system regulates the esophagus, which is a muscular  conduit.

It is through waves of contractions, known as peristalsis or peristaltic movements, the muscular conduit squeezes the food and takes it towards the stomach.

Stomach 

The stomach is a large bag located in the abdomen, responsible for the digestion of proteins. 

The entrance of the organ receives the name of cardia, because it is very close to the heart, separated from it only by the diaphragm. 

It has a small upper curvature and a large lower curvature. The most dilated part is called the "fundic region", while the final part, a narrow region, is called the "pylorus". 

The simple movement of chewing food already activates the production of hydrochloric acid in the stomach. However, it is only with the presence of food, of a protein nature, that the production of gastric juice begins. This juice is an aqueous solution, composed of water, salts, enzymes and hydrochloric acid.

The gastric mucosa is covered by a layer of mucus that protects it from gastric juice aggression, since it is quite corrosive. Therefore, when there is an imbalance in protection, the result is inflammation of the mucosa (gastritis) or the appearance of wounds (gastric ulcer). 

Pepsin is the most potent enzyme in gastric juice and is regulated by the action of a hormone, gastrin. 

When meal protein molecules come into touch with the organ wall in the stomach, gastrin is created. Thus, pepsin breaks down large protein molecules and transforms them into smaller molecules. These are proteoses and peptones. 

Finally, gastric digestion lasts, on average, from two to four hours. In this process, the stomach suffers contractions that force the food against the pylorus, which opens and closes, allowing, in small portions, the chyme (white and foamy mass), to reach the small intestine.

Small Intestine 

The small intestine is a long compartment that can be over six meters long. This is where most of the digestion process takes place. The duodenum, jejunum, and ileum are the three sections that make up the small intestine. 

The duodenum, the first portion of the small intestine, measures about 25 cm and is where the chyme joins with secretions from the pancreas, liver and small intestine itself. These secretions are:

• Pancreatic juice: The pancreas is an attached gland and is responsible for producing an alkaline solution rich in bicarbonate and also in enzymes, such as trypsin and chymotrypsin, which impact nucleic acids, pancreatic nucleases that impact proteins, and pancreatic lipase that impacts lipids. 

• Bile: Produced by the liver, bile is unique from other gastrointestinal tract secretions in that it is devoid of enzymes. This secretion contains salts that serve as emulsifiers or detergents. Bile is stored in the gallbladder despite being produced in the liver. 

• Intestinal or enteric juice: The lining of the small intestine is also responsible for secreting substances. Among the enzymes found in intestinal or enteric juice, maltase, which acts on maltose, sucrase, which acts on sucrose, and lactase, which acts on lactose, stand out.

The villi present in the intestine ensure greater absorption. 

In the duodenum most of the digestion takes place, with the other parts of the small intestine concerned mainly with the absorption of nutrients. After leaving the duodenum, the product of the digestive process goes to the jejunum, which is about 2.5 meters long and goes to the ileum, which is about 3.5 meters long. 

As mentioned, the small intestine also has the function of absorbing nutrients. In this organ, the presence of folds called villi is observed. In the cells of the villi, several microscopic folds, called microvilli, are also observed. These folds ensure an increase in the contact surface, thus providing an increase in the absorption rate.

Large Intestine

The large intestine measures about 1.5 m in length and 6 cm in diameter. It is the site of water absorption (both ingested and digestive secretions), storage and elimination of digestive waste. 

It is divided into three parts: the cecum, the colon (which is subdivided into the ascending, transverse, descending, and sigmoid curve) and rectum. 

In the cecum, the first portion of the large intestine, food residues, already constituting the “fecal cake”, pass to the ascending colon, then to the transverse and then to the descending colon. In this portion, the fecal bolus remains stagnant for many hours, filling the portions of the sigmoid curve and the rectum. 

The rectum is the final part of the large intestine, which ends with the anal canal and the anus, through which feces are eliminated. 

To facilitate the passage of the fecal cake, the glands of the mucosa of the large intestine secrete mucus in order to lubricate the fecal cake, facilitating its transit and elimination. 

Note that plant fibers are neither digested nor absorbed by the digestive system, pass through the entire digestive tract and form a significant percentage of fecal mass. Therefore, it is important to include fiber in the diet to help the formation of feces.

Summary of the Digestive System  

The digestive system is responsible for ensuring the breakdown of food into smaller particles and the absorption of nutrients that are needed by the body. 

The mouth, pharynx, esophagus, stomach, small intestine, and large intestine make up the gastrointestinal tract, which is also where the pancreas, liver, and salivary glands are located. 

In the mouth, food is torn and crushed by the teeth and, with the help of the tongue, is mixed with saliva. 

The food bolus goes from the mouth to the pharynx and from the pharynx to the esophagus, being taken through peristaltic movements to the stomach. 

In the stomach, the food bolus undergoes the action of gastric juice and is called chyme.

From the stomach, the chyme goes to the small intestine, where it will suffer the action of the pancreatic juice, the bile and the secretions produced by the small intestine itself. 

Along with a large portion of the digesting process, nutrient absorption also takes place in the small intestine. 

Feces are created in the large intestine and sent out through the anus.