The digestive system plays a critical role in ingestion, digestion, motility, ab

Question

The digestive system plays a critical role in ingestion, digestion, motility, absorption, and illumination. Explain the difference between each process and identify the Organ/structures of the digestive tract involved in this process. The digestive system plays a critical role in ingestion, digestion, motility, absorption, and illumination. Explain the difference between each process and identify the Organ/structures of the digestive tract involved in this process. The digestive system plays a critical role in ingestion, digestion, motility, absorption, and illumination. Explain the difference between each process and identify the Organ/structures of the digestive tract involved in this process.

Explanation / Answer

The Digestive System starts from the mouth and ends in the rectum.

The digestive system contains several organs including the mouth, oral cavity, oesophagus, stomach, small intestine, large intestine which makes the alimentary canal.

The major functions of digestive system are

1. Ingestion

2. Digestion

3. Breakdown

4. Excretion

Mouth

The opening through which food is ingested. The oral cavity formed by the tongue, Palate & Teeth facilitates the breaking the food into smaller pieces and mix with Saliva which aide in the digestion process. Making food as the bolus.

Oesophagus

The Oesophagus is a muscular tube through which the ground bolus passes from the mouth to the stomach. The oesophagus sharply bent at the point at which it meets the stomach, to prevents the reversal of food. Food is pushed downward into the stomach by an involuntary & alternate contraction and relaxation of muscles called peristalsis.

Stomach

The oesophagus opens into a muscular bag-like structure known stomach. The junction where oesophagus opens into stomach has a sphincter muscle which keeps the stomach intact & prevents backward movement of food. When food reaches the end of the oesophagus , the sphincter muscles open up & dumps the food into the stomach.

The cells in the stomach wall, secrete different acids which increase acidity to a pH of 2. This strong acidic environment helps to kill the bacteria and chemically break the food substances. The peristaltic movement of food helps in mixing and churn the food into a paste-like substance known as chyme.

Small Intestine

The pasty chime is ready to pass through the pyloric sphincter into the duodenum of the small intestine which is the longest part of the alimentary canal.The small intestine comprises three parts-

Duodenum,

Jejunum and

Ileum.

Duodenum is the C shaped organ where the food is mixed with bile & pancreatic juice produced in liver & pancreas respectively and passed through the hepatopancreatic duct.This helps break down of fats & digestion of the food  
Jejunum: forms middle part of small intestine which thick walled which more blood vessels, Wheres the

Ileum which succeeds jejunum is thin with lesser vascularised.

Most of the nutrients are absorbed from the small intestine and passed into the bloodstream via a finger-like, highly vascularised structure called vili.

Large Intestine

The small intestine opens into the caecum of the large intestine, which shorter in length.

The Large intestine has 3 parts: Caecum, Colon and Rectum.
Colon is the longest part of the large intestine , which is divided into 4 rgeions viz.
Ascending colon,
Transverse colon,
Descending colon and
Sigmoid colon.
The large intestine is the site where the extra water from the digested material is reabsorbed, before it is finally excreted.

Rectum opens into the final opening where the food exits (excreted) the body.

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