GATROINTESTINAL SYSTEM

ANATOMY AND PHYSIOLOGY OF THE GASTROINTESTINAL SYSTEM

The primary function of the gastrointestinal system is to break down the largfe molecules of food into simple absorbable nuitrients

This system is composed of many organs wgich intergrate to form a single system.
Organs of the gastrointestinal system can be catagorised into two groups,the alimentary canal and accessoey digestive organs.

ALIMENTARY CANAL :The alimentary canal also called the digestive tract is the hollow pathway in which the food is introduced to the body and expelled as waste.The alimentary canal includes mouth,pharynx,oesophogus,stomach,small and large intestines and anus.

The accessory digestive organs include liver,gall bladder and pancreas

These organs secrete chemical digestives
These secretions help in the breaking down of food whilst it reaches the stomach

ORAL CAVITY :Oral cavity or mouth is responsible for food intake.It consists of the tongue,teeth and salivary glands wjich play vital role in food digestion

The anterior teeth are responsible for cutting food
The posterior teeth are responsible for grinding
Toungue,a strong muscular organs is responsible for manipulation of food into a bolus and mixing it with saliva through a process called insalivation

SALIVARY GLANDS ;The three pairs of glands,parotids,submandibular and sublingual communicate with the oral cavity.

salivation occurs in response to the taste,smell and even appearance of the food
This occurs due to nerve signal thattells the salivary glands to secrete saliva in order to moisten food
Salivation makes food easier top swallow

OESOPHOGUS :Oesophogus is a muscular tube of approximately 25cm of length and 2cm of diameter

It extends from the pharynx to the stomach after passsing through the diaphragm
The oesophogus functions as the transport route through compartments

STOMACH ;Stomach is a j-shaped like bag located in the midline of the oesophogus and small intestines

It is divided into four regions and has two borders called greater and lesser curvatures
The first region is Cardia which surround the cardiac orifice where the oesophogus enters the stomach
Fundus is the superior part of the stomach that is in touch with the diaphragm
The body is the larges region between the fundus and the curved portion of the J
Finally the pylorus which is the curved base of the stomach
FUNCTIONS OF THE STOMACH INCLUDE:
The short term storage of ingested food
Mechanical digestion through food mixing
Chemical digestion of proteins
Absorption of substances

SMALL INTESTINE :>small intestines include duodenum,jejunum and ileum.Its average length is 6m.

Small intestines occupy large portion of the abdominal cavity
Duodenum is the c-shaped section that curves around the head of the pancreas.It mixes digestive secretions from liver and pancreas with the contnt expelled from the stomach
The sharp bend is the begining of the jejunum and it serves as the digestion and absorption site
Ileum is the longest segment and it empties into the caecum

LARGE INTESTINE :>Large intestines is a horse shoe shaped organ and it is composed of the appendix,caecum,asc ending,transverse,descending and sigmoid colon and the rectum

Its length is approximately 1.5m and width of 7.5cm
Caecum compessess food into a faecal content
Rectum is the final 15 cm of the large intestine
It holds faecal matter before it passess through the anorectal canal to the anus

LIVER :>Liver is the large reddish organ situated in the upper quadrant of the abdomen

Liver has mNY functions but its primary function during digestion is to produce bile which is latyer stored in the gall bladder
It is also responsible for metabolism of the nutrients

GALL BLADDER ;>Gall bladder is a hollow pear shaped organ that sits above the liver lobe

It consists of a fundus,body and neck
Its main function is to stotre bile
Bile is a thick fluid that contains enzymes which dissolves fats in the intestine

PANCREAS :>Pancreas is a lobular,pinkish organ that lies behind the stomach.

It has both the exocrine and endocrine functions
Pancreas secretes fluids rich in carbohydrates and inactive enzymes
These fluids are released only after a trigger by duodenum to prevent pancreas from digesting itself

FUNCTIONS OF THE GASTROINTESTINAL SYSTEM

REGULATION OF THE CHEMICAL DIGESTIVES

NEURAL REGULATION :walls of the alimentary canal contains sensors that help regulate digestive functions

These includes mechanoreceptors,chemoreceptors and osmoreceptors.
They are responsible for detecting mechanmical,chemical and osmotic stimuli respectively.
They can detect what type of food has caused the stomach to expand,has the food been properly grinded and how much water is required for digestive process to continue.

HORMONAL REGULATION : many hormones are involved in the digestive process

The main hormone is gastrin which is secreted in the response of resence of food
Gastrin stimulates the secretion of gastric acids.
.Duodenum secretes secretin which stimulates watery secretion of biocarbonate
Cholecykotinin which stimulates secretion of pancreatic enzymes
Other hormones are secreted by epuithelium cells called endocrinocytes.

INGESTION:this kis the introduction of food into the mouth

PROPULSION:this is the movement of food through the digestive tract.

SECRETION:this system also secretes enzymes and other substances tha liquifies,adjust pH and chemically breaks down food

DIGESTION:this function is achieved through chemical and mechanical digestions where food is being broken down into smaller pieces.

ABSORPTION:this is the movement of nutrients from digestive tract to the blood system either by passive diffusion or active transport

DEFECATION:this is the process of eliminating undigested materials through the anus

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