Salivary glands make saliva, which aids in digestion, keeps your mouth moist and supports healthy teeth. You have three pairs of major salivary glands under and behind your jaw — parotid, sublingual and submandibular.

Many other tiny salivary glands are in your lips, inside your cheeks, and throughout your mouth and throat.

There are two types of salivary glands:
the major salivary glands
the minor salivary glands

MAJOR SALIVARY GLANDS

The major salivary glands are the largest and most important salivary glands. They produce most of the saliva in your mouth.

There are three pairs of major salivary glands: the parotid glands, the submandibular glands, and the sublingual glands.

Parotid Glands
The parotid glands are the largest salivary glands. They are located just in front of the ears. The saliva produced in these glands is secreted into the mouth from a duct near your upper second molar.

Submandibular Glands
About the size of a walnut, the submandibular glands are located below the jaw. The saliva produced in these glands is secreted into the mouth from under the tongue.

Sublingual Glands
The sublingual glands are the smallest of the major salivary glands. These almond-shaped structures are located under the floor of the mouth and below either side of the tongue.

MINOR SALIVARY GLANDS

There are hundreds of minor salivary glands throughout the mouth and the aerodigestive tract. Unlike the major salivary glands, these glands are too small to be seen without a microscope. Most are found in the lining of the lips, the tongue, and the roof of the mouth, as well as inside the cheeks, nose, sinuses, and larynx (voice box).

The gallbladder is a small pouch that sits just under the liver. The gallbladder stores bile produced by the liver. After meals, the gallbladder is empty and flat, like a deflated balloon. Before a meal, the gallbladder may be full of bile and about the size of a small pear.

In response to signals, the gallbladder squeezes stored bile into the small intestine through a series of tubes called ducts. Bile helps digest fats, but the gallbladder itself is not essential. Removing the gallbladder in an otherwise healthy individual typically causes no observable problems with health or digestion yet there may be a small risk of diarrhea and fat malabsorption.

The liver is an organ about the size of a football. It sits just under your rib cage on the right side of your abdomen. The liver is essential for digesting food and ridding your body of toxic substances.

The liver has two large sections, called the right and the left lobes. The gallbladder sits under the liver, along with parts of the pancreas and intestines. The liver and these organs work together to digest, absorb, and process food.

The liver is located in the upper right-hand portion of the abdominal cavity, beneath the diaphragm, and on top of the stomach, right kidney, and intestines

The wall of the stomach is made up of the mucosa (innermost layer), submucosa, muscle layer, subserosa, and serosa (outermost layer). The stomach is an organ in the upper abdomen

The muscular wall of stomach plays a major role in the process of digestion. They contain secretary glands that release digestive juice. The lining of stomach has ridges called rugae.

The inner surface of the stomach is lined by a mucous membrane known as the gastric mucosa. The mucosa is always covered by a layer of thick mucus that is secreted by tall columnar epithelial cells.

Intestinal villi are tiny, finger-like projections made up of cells that line the entire length of your small intestine. Your villi absorb nutrients from the food you eat and then shuttle those nutrients into your bloodstream so they can travel where they’re needed.

Villi are specialized for absorption in the small intestine as they have a thin wall, one cell thick, which enables a shorter diffusion path. They have a large surface area so there will be more efficient absorption of fatty acids and glycerol into the blood stream.

Millions of tiny finger-like structures called villi project inwards from the lining of the small intestine. The large surface area they present allows for rapid absorption of digestion products.