Digestive system

Digestive system - Gastrointestinal System

Definition.

The system responsible for converting larger food particales into smaller particles and the do their absorption is calles 'GI-system' or 'Digestive system' and this process is nkown as 'digestion'

Introduction.

The Digestive system is a series of hollow organs joined a long, twisting tube from the mouth to the anus. Inside this tube is a lining called the mucosa. In the mucosa contain tiny glands that produce juices to help digest food.
There are also two solid digestive organa, the liver and the pancreas, which produce juices that reach the intestine though small tubes. In addition parts of other organ system (for instance, nerves and blood) play a major role in the digestive system.

GI Tract.

GI tract is 30ft long extends from mouth to anus. The followings are
primary organs of Digestive system

1. Mouth

     It is also called oral cavity in biology terminology. It is the start of digestion. When we eat food our salivary glands mixes saliva in food to help the digestion and pull it into the pharynx.
   

2. Pharynx

It connects oral cavity with esophagus. It is a common pass way for food and air. It has three parts, 1.nasopharynx, 2.oropharynx, 3.laryngopharynx.


3. Esophagus

It is a muscular, membranous tube, ~25cm long. It acts as transport organ from pharynx to stomach. Lubrication due to mucus. microscopically comprises of three layers. Upper, middle and lower each having different type of muscle tissue. Microspically comprises of three layers: Upper, Middle & Lower. Each having different type of muscles tissues.

1. Stomach

   The stomach is a muscular organ located on the left side of the upper abdomen. It starts from the end of esophagus and ends on duedenum. The food enters the stomach through a muscular valve called lower esophagus sphincter.
        The stomach secrets acid and enzymes that digest the food. Ridges of muscle tissue called rugger line the stomach. The stomach muscles contract periodically, churning food to help digestion. The food exits through another muscular valve known as pyloric sphincter. It is a flexible muscular sac. Capacity is 1.5 L .
   Functions:
   stores food.
   Mixes gastric juice.
   Secretes HCl, enzymes and substances.
    

Parts of Stomach: 
Followings are the part os stomach

• Cardia
• Fundus
• Body
• Antrum

1. Small intestine

The small intestine is the where most of the chemical and mechanical digestion is carried out. Tiny projections called villi line the small intestine have three parts.
1.The Duodenum 2.The Jejunum 3.The Ileum.


2. Large intestine

The large intestine extends from the end of ileum to the anus. It is about 5 feet long, being one-fifth of the whole extent of the intestinel canal. It can be divided into four main section 1.Ascending colon, 2.Transverse colon 3.Descending colon, 4.Sigmoid colon.


3. Rectum

It is the final straight portion of large intestine. It is about 12cm long. It is a storage organ for feces and connects to anus.


4. Anus

It is an opening at the opposite of mouth to GI-tract.

Accessory organs.

1. Pancreas

It is located in abdominal cavuty behind the stomach.It is an endocrine gland producing several important hormones, including insulin, glucagon, somatostatin and pancreatic polypeptide which circulate in the blood.


2. Liver

It is located in upper right quadrant of the abdomen, below the diaphragm. The liver has wide range of functions, including detoxification of various metabolites, proien synthesis and the production of biochemicals for digestion.


3. Gall bladder

It is storage organ of bile and before secreting in small intestine.Human can live without Gallbladder.The surgical removal of gallbladder is called cholecystectomy.

Fuctions of GI-Tract.

• Motility

                 Movement of food though GI-tract.

• Secretion

                 Exocrine & Endocrine secretions.

• Digestion

                  Breakdown of food particles into absorable form.

• Absorption

                  passage of absorbable food into blood.

• Storage and elimination

                 GI-tract stores food in stomach and feces in rectum and then eliminate it throw anus.