Animal Anatomy Lecture 2

Digestive System Anatomy

Dr. Jehane Ibrahim

Digestive System Anatomy

Digestive System Anatomy

Digestive tract Alimentary

canal

Regions Mouth or oral

cavity Pharynx Esophagus Stomach Small intestine Large intestine Anus

Accessory organs Include glands

Digestive system The digestive system is a group of organs

working together to convert food into energy and basic nutrients to feed the entire body.

Food passes through a long tube inside the body known as the alimentary canal or the gastrointestinal tract (GI tract). The alimentary canal is made up of the: oral cavity, pharynx, esophagus, stomach, small intestines, and large intestines.

Digestive system In addition to the alimentary canal, there are

several important accessory organs that help your body to digest food but do not have food pass through them.

Accessory organs of the digestive system include the teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

Digestive system To achieve the goal of providing energy and

nutrients to the body, there are six major functions that take place in the digestive system:

Ingestion Secretion Mixing and movement Digestion Absorption Excretion

Head and Neck HEAD AND

NECK Mouth

Gingiva (Gums) Lips Teeth Tongue Parotid Gland Parotid Duct Sublingual Gland Sublingual Duct Submandibular

Gland Submandibular

Duct Palatine tonsil Epiglottis Pharynx

Teeth

Pharynx

Head and Neck HEAD AND NECK Mouth: Food begins its journey through the

digestive system in the mouth, also known as the oral cavity. Inside the mouth are many accessory organs that aid in the digestion of food—the tongue, teeth, and salivary glands.

Gingiva, or gum, is the soft tissue that covers and protects the root of the tooth. 

Lips: The lips are highly mobile structures that surround the mouth opening. They contain skeletal muscles and a variety of sensory nerves that are useful in judging the temperature and texture of foods. Their normal reddish color is due to an abundance of blood vessels near their surfaces.

Head and Neck HEAD AND NECK

Teeth: The teeth are a group of hard organs found in the oral cavity. We use teeth to masticate (or chew) food into tiny pieces.

Tongue: It is a strong muscle that is covered by the lingual membrane and has special areas that detect the flavor of food. The tongue is made up of muscles covered by mucous membranes. 

Parotid gland: The parotid gland is the largest of the three major pairs of salivary glands. It is located anteriorly and inferiorly to the ear between the skin and the muscle of chewing.

The parotid duct carries its contents and drains into the mouth.

Head and Neck HEAD AND NECK

The sublingual gland: lies under the floor of the mouth and on the side of the tongue. It is one of the three major pairs of salivary glands. Each sublingual gland possesses several small sublingual ducts that empty into the floor of the mouth.

The submandibular gland is one of the three major sets of salivary glands. It has a muscular covering and empties its contents by way of the submandibular duct into the floor of the mouth on both sides.

Head and Neck HEAD AND NECK

Palatine tonsil: The palatine tonsil are in the back of the mouth, on both sides of the tongue and closely associated with the palate. These masses composed of lymphatic tissue. These structures lie beneath the lining of the mouth and, like other lymphatic tissues, they help to protect the body against infections.

Epiglottis: The epiglottis is a flexible flap at the superior end of the larynx in the throat. It acts as a switch between the larynx and the esophagus to permit air to enter the airway to the lungs and food to pass into the gastrointestinal tract. 

Head and Neck HEAD AND NECK

Pharynx: is a funnel-shaped tube connected to the posterior end of the mouth. The pharynx is responsible for the passing of masses of chewed food from the mouth to the esophagus. The pharynx also plays an important role in the respiratory system, as air from the nasal cavity passes through the pharynx on its way to the larynx and eventually the lungs.

Because the pharynx serves two different functions, it contains a flap of tissue known as the epiglottis that acts as a switch to route food to the esophagus and air to the larynx.

Head and Neck HEAD AND

NECK Mouth

Gingiva (Gums) Lips Teeth Tongue Parotid Gland Parotid Duct Sublingual Gland Sublingual Duct Submandibular

Gland Submandibular

Duct Palatine Glands Epiglottis

Upper Gastrointestinal Tract

UPPER GI TRACT Esophagus Stomach Liver Gallbladder Pancreas

Upper Gastrointestinal Tract

Esophagus: The esophagus is a long, thin, and muscular tube that connects the pharynx (throat) to the stomach. It forms an important piece of the gastrointestinal tract and functions as the canal for food and liquids that have been swallowed into the pharynx to reach the stomach.

Upper Gastrointestinal Tract

Stomach: is the main food storage tank of the body.

The stomach is a rounded, hollow organ located just inferior to the diaphragm in the left part of the abdominal cavity. Located between the esophagus and the duodenum, the stomach is a roughly crescent-shaped enlargement of the gastrointestinal tract.

The inner layer of the stomach is full of wrinkles known as gastric folds. This folds both allow the stomach to stretch in order to accommodate large meals and help to grip and move food during digestion.

Upper Gastrointestinal Tract The stomach can be divided into four regions

based on shape and function:  The esophagus connects to the stomach at a

small region called the cardia. The cardia is a narrow, tube-like region that opens up into the wider regions of the stomach.

The cardia empties into the body of the stomach, which forms the central and largest region of the stomach.

Superior to the body is a dome shaped region known as the fundus.

Inferior to the body is a funnel shaped region known as the pylorus. The pylorus connects the stomach to the duodenum and contains the pyloric sphincter. The pyloric sphincter controls the flow of partially digested food (known as chyme) out of the stomach and into the duodenum.

Upper Gastrointestinal Tract Upper Gastrointestinal Tract

The stomach :

Upper Gastrointestinal Tract Liver: the liver is the body’s second largest

organ. The liver consists of 4 distinct lobes – the left, right, caudate, and quadrate lobes.

The left and right lobes are the largest lobes and are separated by the falciform ligament. The right lobe is about 5 to 6 times larger than the tapered left lobe.

The small caudate lobe extends from the posterior side of the right lobe and wraps around the inferior vena cava.

The small quadrate lobe is inferior to the caudate lobe and extends from the posterior side of the right lobe and wraps around the gallbladder.

Upper Gastrointestinal Tract Liver:

Upper Gastrointestinal Tract 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.

The pancreas is a glandular organ in the upper abdomen, but really it serves as two glands in one: a digestive exocrine gland and a hormone-producing endocrine gland. Functioning as an exocrine gland, the pancreas excretes enzymes to break down the proteins, lipids, carbohydrates, and nucleic acids in food. The pancreatic duct carries the digestive enzymes produced by endocrine cells to the duodenum

Upper Gastrointestinal Tract

The pancreas:

Lower Gastrointestinal Tract

LOWER GI TRACT Small Intestine

Duodenum Jejunum Ileum

Large Intestine Cecum Appendix Ascending Colon Transverse Colon Descending

Colon Sigmoid Colon Rectum Anus

Lower Gastrointestinal Tract The small intestine: is a long, highly convoluted

tube in the digestive system that absorbs about 90% of the nutrients from the food we eat.

The small intestine can be divided into 3 major regions:

The duodenum is the first section of intestine that connects to the pyloric sphincter of the stomach. It is the shortest region of the small intestine, measuring only about 10 inches in length. Partially digested food, or chyme, from the stomach is mixed with bile from the liver and pancreatic juice from the pancreas to complete its digestion in the duodenum.

The jejunum is the middle section of the small intestine that serves as the primary site of nutrient absorption. It measures around 3 feet in length.

The ileum is the final section of the small intestine that empties into the large intestine via the ileocecal sphincter. The ileum is about 6 feet long and completes the absorption of nutrients that were missed in the jejunum.

Lower Gastrointestinal Tract The small intestine:

Lower Gastrointestinal Tract The Large intestine: The large intestine is the

final section of the gastrointestinal tract that performs the vital task of absorbing water and vitamins while converting digested food into feces. Although shorter than the small intestine in length, the large intestine is considerably thicker in diameter, thus giving it its name. 

Lower Gastrointestinal Tract The inferior region of the large intestine forms a

short dead-end segment known as the cecum that terminates in the vermiform appendix.

The superior region forms a hollow tube known as the ascending colon that climbs along the right side of the abdomen. Just inferior to the diaphragm, the ascending colon turns about 90 degrees toward the middle of the body at the hepatic flexure and continues across the abdomen as the transverse colon. At the left side of the abdomen, the transverse colon turns about 90 degrees at the splenic flexure and runs down the left side of the abdomen as the descending colon. At the end of the descending colon, the large intestine bends slightly medially at the sigmoid flexure to form the S-shaped sigmoid colon before straightening into the rectum. The rectum is the enlarged final segment of the large intestine that terminates at the anus.

Lower Gastrointestinal Tract Lower Gastrointestinal Tract

The inferior region of the large intestine forms a short dead-end segment known as the cecum that terminates in the vermiform appendix. The superior region forms a hollow tube known as the ascending colon that climbs along the right side of the abdomen. Just inferior to the diaphragm, the ascending colon turns about 90 degrees toward the middle of the body at the hepatic flexure and continues across the abdomen as the transverse colon. At the left side of the abdomen, the transverse colon turns about 90 degrees at the splenic flexure and runs down the left side of the abdomen as the descending colon. At the end of the descending colon, the large intestine bends slightly medially at the sigmoid flexure to form the S-shaped sigmoid colon before straightening into the rectum. The rectum is the enlarged final segment of the large intestine that terminates at the anus.

Lower Gastrointestinal Tract Lower Gastrointestinal Tract