Step 1- Introduction

The digestive system of the human play a very important role in growth and development. Digestion is a catabolic process in which food is broken down into small molecules to derive energy from it to perform the various metabolic processes.

The gastrointestinal tract is the organ responsible for transporting and digesting food, absorbing digested products, and expelling waste.

Step 2- Answer

The gastrointestinal tract is a portion that starts from the mouth ends at the anus. The GI tract is a series of organs of the digestive system that includes the mouth, esophagus, stomach, small intestine, large intestine, cecum, and anus.

Mouth: The mouth also called the buccal cavity is formed by cheeks, palates, lips, and tongue. Teeth cut or tear the food into smaller particles, it helps to swallow the food. The chewing of food also mixes the saliva into the food which helps digestion. The tongue act as a floor of the oral cavity, the movement of the tongue is important to guiding food within the mouth during chewing and swallowing. Apart from this, major test buds reside on the tongue. The tongue also secretes mucus and water serous fluids that contain the enzyme lingual lipase which acts on triglycerides.

Pharynx: Pharynx (throat) is a funnel-shaped tube that acts as a common passageway for both the respiratory system and digestive system. The food is passed into the pharynx for the further process of digestion.

Esophagus: Esophagus is a food pipe or gullet that connects the pharynx to the stomach. The esophagus contains submucosal and mucosal glands that secrete mucus for lubrication of the esophageal epithelial lining. The esophagus plays no role in chemical digestion as such, its major role is to pass the bolus (chewed food) from the mouth to the stomach.

Stomach: The stomach is the major part of the GI tract, which is located between the esophagus and small intestine. the major function of the stomach is to store, dissolve and partially digest the food particles. The stomach also regulates the rate at which the stomach's content is released into the small intestine. The wall of the stomach has deep folds that churn and mix the food with gastric juice. When the bolus is mixed with gastric juice it becomes a semi-liquid substance called, Chyme.

Small intestine: Small intestine is the part of the digestive tract where most of the digestion and absorption takes place. The small intestine is divided into three regions, namely the duodenum, jejunum, and ileum. The walls of the small intestine secrete the various types of enzyme and digestive juices that work together with the enzymes that secreted from the liver and pancreas that help indigestion. The wall of the small intestine contains finger-like projections called villi, the apical portion of the villi called microvilli contains many fine projections on their surface, this combination of villi and microvilli increases the surface area of the small intestine.

Large intestine: The large intestine has a wide diameter than the small intestine but it is shorter in length. The large intestine is divided into three regions; cecum, colon, and rectum. The mucosal epithelium of the large intestine contains mostly absorptive and goblet cells. It does not produce digestive enzymes, it does absorb water, salts, and some vitamins. It also stores indigestible material until it is eliminated from the anus. The cecum is the blind end of the large intestine which has a small projection called, vermiform appendix. The anus is the terminal part of the rectum through which the faces are eliminated from the body.

Accessory organs of the gastrointestinal tract:

The accessory organs that help to aid the process of digestion are salivary glands, liver, gallbladder, and pancreases.

Salivary glands: A salivary gland is a gland that secretes saliva in the oral cavity. Saliva softens, moisten, and dissolves food, it also cleanses the mouth and teeth and initiates the digestion of starch.

Liver: The liver is one of the important accessory organs that produces bile, which is needed for the emulsification and absorption of lipids in the small intestine.

Gallbladder: The liver continues secrets bile, the sphincter of oddi prevents bile from entering the duodenum except during digestion. when this sphincter is closed, bile secreted from the liver is diverted back into the gallbladder. the gallbladder is a pear-shaped, muscular sac attached to the surface of the liver that store and concentrate the extra bile and releases it into the duodenum.

Pancreas: The pancreas is an elongated gland that lies behind and below the stomach. It has both endocrine and exocrine functions, as an endocrine gland, it secretes two major hormones, insulin and glucagon. The exocrine gland of the pancreas secretes pancreatic juices. The enzymes present in the pancreatic juices help to break down sugar, starch, and fats.

List the parts of the digestive tract, describe the functions of each part. List the accessory organs to the digestive system and list secretions for each. on fetal pig. Don't copy from Google

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