INTRODUCTION

The importance of the digestive system of humans cannot be overstated. It’s basically the powerhouse that provides the nutrients the body needs. A lot goes on in the digestive system before we actually get the crucial nutrients. People are often in the habit of eating indiscriminately without minding how it affects the body. Hence, it is important to fully understand what the digestive system is all about and its impact on our body.

WHAT IS THE DIGESTIVE SYSTEM?

The digestive system is the system in the human body that works primarily for digestion. Digestion is the process of breaking down large molecules of food into smaller molecules that can be absorbed into the bloodstream. The nutrients then circulate to other parts of the body as required. The digestive system embodies the alimentary canal, some accessory organs, and other systems to break down foods till the nutrients are absorbed.

STAGES OF DIGESTION

The entire digestive process in the human body is divided mainly into three stages. These stages are the Cephalic Phase, Gastric Phase, and the Intestinal Phase.

  • The Cephalic Phase: This is the first stage of digestion. At the sight or smell of food, signals are sent by the taste buds and smell stimuli to the hypothalamus. The body then begins to secrete gastric juices in response to the stimuli.

  • The Gastric Phase: The Gastric phase is the second stage and it takes about 4 hours from the period of digestion. This stage involves the breaking down of food by chewing in the mouth before it moves into the stomach through the esophagus. The digestive enzymes present in the saliva start acting on the food from the mouth before the gastric juices secreted in the stomach at the cephalic phase and other digestive enzymes continue the digestion process.

  • The Intestinal Phase: This is the last stage and it is divided into two parts; excitatory and inhibitory. At this stage, partially digested food goes into the small intestine where they’re finally broken down completely and taken into the bloodstream. The process excites the duodenum and triggers it to activate sympathetic fibers that would tighten the sphincter and stop any more food from entering into the rectum.

STRUCTURES OF THE DIGESTIVE SYSTEM OF HUMAN AND THEIR FUNCTIONS.

There are two major components that make up the human digestive system. These structures all have their own role in the process of digestion. The two components include the accessory organs and the alimentary canal.

THE ALIMENTARY CANAL

The alimentary canal is the largest component of the digestive system and some refer to it as the digestive tract or alimentary tract. It’s a network that connects from the mouth to the rectum. There are seven important parts in this structure and they include stomach, mouth, small intestine, pharynx, large intestine, esophagus, and rectum.

  • The Mouth: The mouth is the first part of the digestive tract and it employs a number of structures like the tongue, teeth, etc to aid digestion processes. The mouth is bounded by muscles and bones. Important parts in the mouth that helps digestion are:

  1. The Tongue: It’s a muscular structure at the lower region of the mouth and it is responsible for the sense of taste. The tongue helps in the tasting, chewing, and swallowing of food.

  2. The Teeth: They are connected to the mouth through gums that are ingrained into the mouth socket. There are four different sets of teeth in the mouth; incisors, canines, premolars, and molars. Incisors are the biggest teeth that stand in the middle and they’re used for cutting food. The canines are directly after the incisors and are used to bite foods. While the premolars and molars are smaller in sizes and are used for chewing and grinding of food substances.

  3. Saliva: Saliva is secreted from the salivary glands which are also a part of the endocrine glands. Saliva helps soften the food in the mouth for easier chewing and swallowing. It also has some digestive enzymes (amylase and lipase) that starts breaking down carbohydrate and fats substrates before it moves down into the esophagus.

  • The Pharynx: The Pharynx connects the digestive system and the respiratory system. It also connects the back cavity of the mouth with the esophagus. The muscular walls drag the food swallowed from the mouth and push it into the esophagus for the continuous digestion process.

  • The Esophagus: The esophagus through the pharynx connects the mouth and the stomach. It’s about 25cm long and 2cm in diameter wide. It has muscles at both ends that enclose it. They’re called the upper and lower esophageal sphincters. The major function of the esophagus is to pass down food from the mouth into the stomach through the process of peristalsis.

Peristalsis is a periodical contraction and expansion of the muscles in the esophagus that gives rise to the pressure that helps push food down. The esophageal sphincters also help separate the foods into small portions known as a bolus before it moves into the stomach.

  • The Stomach: The stomach is a J-shaped organ and it’s one of the most important structures in the digestive tract. The stomach performs quite a number of tasks in the digestion process. It acts as temporary storage for the food passed down and during this period, the digestive enzymes like pepsin are able to act upon the substrates.

The muscles present in the stomach also continue to grind the food and allow the gastric juices to react with it. It also absorbs part of the content that can be absorbed especially water. The stomach further regulates the acid contents passed back into the body when the food is being taken down into the small intestine through the pyloric sphincter.

  • The Small Intestine: The small intestine is directly connected with the stomach and consists of ileum, jejunum, and duodenum. The absorption of nutrients often takes place in the small intestine.

The duodenum is the first part of the small intestine and it’s responsible for the continuous breaking down of the food from the stomach. The enzymes secreted from the gallbladder and the pancreas act upon the food in the duodenum.

The jejunum is the middle part and it transports the broken food molecules into the ileum. The ileum is the last part and is directly connected with the large intestine. It has a large surface area with microvilli that allows the absorption of the nutrients into the bloodstream. The leftovers are then passed down into the large intestine.

  • The Large Intestine: The large intestine also known as the colon consists of: the descending colon, the transverse colon, the cecum, the sigmoid colon, and the ascending colon.

The five parts are all connected with the cecum as the first part which is connected with the small intestine while the sigmoid colon is the last part and is connected with the rectum. The digestion leftovers are passed through the colon as a liquid form until they become solid. The solid is then stored in the sigmoid colon until there’s enough to be transported into the rectum.

  • The Rectum And The Anus: The rectum links the large intestine and the anus. It is where the leftovers or stool will be finally removed from the body. It acts as a chamber that holds stool and sends a signal to the brain. If the brain responds to the stimuli that it is safe to remove the contents in the rectum. The rectal sphincters will relax and allow passed into the Anus.

When the content gets into the anus, it has linings on the wall that signals the body about the presence of the waste contents. It can also determine whether the content is solid, liquid, or gas. It has another sphincter that controls the release of the content.

THE ACCESSORY ORGANS

The accessory organs of the human digestive system are basically organs that help secrete contents like saliva, gastric juices, etc, that aid proper digestion. The three major ones include the salivary glands, pancreas, and liver.

  • Salivary Glands: Sublingual glands, parotid glands, and the submandibular gland make up the salivary gland. They are all situated in different positions in the mouth and produce the necessary saliva for digestion.

  • Pancreas: A pancreas is a form of an endocrine gland located in the stomach. It produces enzymes that work with the juices from the gall -bladder to aid digestion in the small intestine.

  • Liver: The liver is the biggest gland in the body. It secretes bile that helps digestion in the small intestine. It also helps regulate the absorption of nutrients already broken down in the small intestine and detoxify the body against harmful substances.

WHY SHOULD YOU CARE ABOUT THE DIGESTIVE SYSTEM OF HUMAN?

There are a number of reasons why you should care about the digestive system; some of which are highlighted below.

  1. Healthy Living: Proper digestion in the body means your body gets all the necessary nutrients for growth and it stays healthy.

  1. Energy: Our body constantly needs energy and the primary source of getting that energy is from the carbohydrates broken down into glucose through digestion processes.

  2. Cell & Tissue Repairs: The amino acids gotten from digested protein are responsible for aiding the repair of worn out or damaged tissues and cells in the body.

  3. Digestive Disorders: When we don’t care for the digestive system, we’re susceptible to improper digestion. This can make us develop different kinds of digestive disorders like constipation, acid reflux, etc.

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