Digestive system

                

The digestive system describe the alimentary canal . it's accessory organ and a variety  of digestive processes that prepare food eaten in the diet for absorption. the aliminentary canal begins at the mouth passes through the thorax 

abdomen and pelvis end the anus .

         Process of digestion

There are five type of process in the

Digestive-------

1. Ingestion-- This is the taking of food in to the alimentary tract it means drinking and eating .

2. Propulsion-- This mixes and move the contents (food) along the alimentary tract .

3. Digestion -- This consist of -----------

(I) Mechanical breakdown of food by 

    mastication ( chewing ).

(ii) Chemical digestion of food in to small          molecules by enzymes present in                  secretion produced by glands an                    accessory organ the digestive system.

4. Absorption -- 

This is the process by which digestive food substanc   pass through the wall of some organ of the alimentary canal in  the  blood and lymph capillaries for circulation and used by body cell .

5. Elimination--Food substance the every eaten but cannot be digested and absorbed are excreted from the alimentary canal as the faecs by the process of defaecation .

        

 Structure of the alimentary canal

The wall of alimentary canal are formed by four layer of tissue -----

1. Adventitia or serosa -- This is the outer most layer in the thorax is consist of loose fibrous tissue and in the abdomen organ are covered by serous membrane cold peritoneum.

2.Muscle layer -- The muscle fibrous of the outer layer are arranged longitudinally and those the inner layer encircle the wall of the tube .bitween these two muscle layer are blood vessels , lymph vessel and a plexus (network) of sympathetic and Parasympathetic nerves .

Contraction and relaxation of these muscle layer occurs in waves ,which push the contents tract onwards .the onwards movement of the contents of tract is controlled at various points by sphinter , this type Of contraction of smooth muscle is called peristalsis . the sphincters are 
act as valve that prevents the back flow of the food particles in to the alimentary tract . this control allow time of digestion and absorption to take rays .

3. Submucosa -- This layer consist of
loose connective tissue collagen and 
some elastic fibre . which binds the muscle layer of the mucosa .

4. Mucosa -- This consist of three layer of tissue --------

*Epithelium -- It is formed by columnar epithelium is the inner most layer , it has function protection, secretion of absorption .

*Lamina propria -- It consist of loose 
connective tissue which suports the blood vessels that nourish the inner 
epithelial layer .

*Muscularis mucosa -- It is the thin outer layer of smooth muscle .it provide involution of the mucosal layer .
eg-- Gastric glands , villi .

      *Organ of digestive system*

  1.    Mouth
  2.    Pharynx
  3.    Oesophagus
  4.    Stomach
  5.    Small intestine
  6.    Large intestine
  7.    Rectum and anal canal

1. Mouth -- mouth is the first digestive organs , the process the digestion start from the mouth it is also called oral cavity. 

It consist of -------

(I) Vestibular -- The space between the gumbs is called vestibular .

(ii) Cavity -- The space between the bungs and teath is called cavity .

    Structure Of The Mouth 

It consist the following parts ------

    Teeeth

    Tongue 

    Salivary gland

1. Teeth -- Teeth are of the mouth it is fix in 

the jaw . The first set of teeth called temporary teeth or dentition teeth and llnd

set is called permanent deciduous teeth .

The temporary teeth are 20 is number and each half of each jow consist of two incisor ,

One canine and two molars.

The permanent teeth are 32 in number and consist of two incisor or one canine and two

Premolar and three molar .

             *Structure of tooth*

The tooth consist of tree part ---------

1. Crown -- The parts that produced front the gumbs .
2. Root-- The parts embedded in the bone .
3. Neck -- Which is sarounding by the gumb. The crown is covered by thin layer of very heart substance called enamel .

                  *Function of teeth*

1. The safe of incisor in canine is like a blade so these are used for cutting .
2. The safe of molar and premolar are flats surface so these are use for granding chewing .

                    *Tongue*

The tongue the voluntary muscles . Structure that Red occurred the flore of the 

mouth. it is attached by its base to hyoid bone . the superior surface consist of stratified squamous epithelium tissue . the 

little progectiop the contain sensory 

receptors (specialisse nerve ended) for the 

Sense of the teste in the teste words .

               *Function of tongue*

 1. Speech

 2. Taste 

 3. Mastigation

 4. Swelling

 *Blood supply to the tongue *

The lingual branch of the external carotid 

artery supply the blood to the tongue and lingual vein drain the blood from the tongue .

  *Nerve supply to the tongue*

 1.  Lingual branch of the nerve is                          mandibular nerve.

 2.  The facial and glossopharyngeal nerve

      (7 - 9 cranial nerve) the nerve of teste .

               *Salivary gland*

Salivary gland release their secretion in to
duct that lead to the mouth . There are tree
main pairs -----------

1. Parotid gland -- These gland locatid in blow the external acoustic meatus . Each
glan has the parotid duct opening in to the mouth at the level of the 2nd upper molar
tooth .

2. SubmendibuSub gland -- These lie one on each side of the face under the angle of
the jaw . The two submendisubma duct open from the flor of the mouth one on each side of the frenulum of the tongue .

3. Sublingual gland -- These gland lie under mucous membrane of the floor of the mouth in front of the submandibular gland.
They have numerous small duct that open in the floor of the mouth .

     *Composition of saliva*

Saliva is excreted by salivary gland . These
gland are present in to the oral cavity .
It consist of -------------

   Water
   Minaral salt
  Salivary amylase ,Enzyme
  Mucus
  Immunoglobulins
  Blood clotting factor

     2--   *Pharynx*

Pharynx is the 2nd digestive organ muscular tube switched behind the nose and mouth . It is devided in to three parts----
1. Nasopharynx
2. Oropharynx
3. Laryngopharynx

Nasopharynx is important in respiration oropharynx and laryngopharyngeal are
passeges commen to both the respiration
and digestive system . The nasopharynx is
behind the nose and oropharynx behind the oral cavity .
Food passege from the oral cavity to the pharynx , then to the oesopharynx below the wall of the pharynx consist of tree layer
------------
   Muscular
   Submucosa
   Mucosa

       *Blood Supply*

The branch of external caroted artery and 

facial artery supply the pharynx vein drainage is in to the facial vein and the 

internal jugular vein .

         Nerve supply

Nerve supply by pharyngeal plexus is consist of parasympathetic and sympathetic.

  3.    *Oesophagus*

It is the narrow muscular tube forming the 

Passes of the food from the pharynx to the 

stomach it is start from the lower part of 

The pharynx. The lengtg if the oesophagus

is about 25cm and the diameter is 2cm .

It consist of layer -----------

Adventitia of serosa 

Muscle layer 

Submucosa

Mucosa

         4 .  Stomach

Stomach is the J shape and the most importent organ of the digestive system.

It lies in the epigastric region in the abdominal cavity stomach is devided three

parts ----------

1. Fundus-- it is the upper parts of the 

stomach.

2. Body -- It is store the food and secreted

HCL acid which hold the digestive the food.

3. Pylorus -- It is end parts of the stomach and the distal and of the pylorus. 

The pyloric sphicter guarding the opening 

blue the duodenum.It is a consist of four layer ------------
1. Peritoneum
2. Muscle layer
3. Submucosa
4  Mucosa

                     *Blood Supply*
Stomach by the left gastric artery is the branch of coeliac artery and right gastric artery is the branch of gastroepiploic
artery . Vein drainage is through vein of
corresponding name in the portal vein .

         *Function of the stomach*

1. It is secrete gastric of juice which contain
    HCL that help in the digestion .
2. It protein the body by destroying the
    pathogenic bacteria .

                      *Gastric juice*

About two letar of gastric gastric juice are
Secreted daily by specialised secreted the gland in the mucosa .
It consist of -----------
1. Water
2. Minaral salt
3. Hydrochloric acid
4. Mucus by stomach surface

               5. Small intestine 

The small intestine is continuous with 

Stomach and the pyloric sphincter . The 

Small intestine is about 25cm is diameter .

It is over 5 meter long and leads in to the 

large intestine at the ileocecal valve .

Small intestine is decided tree parts ---------

1. Duodenum

2. Jejunum

3. Ileum

1. Duodinum -- It is a about 25 cm long and 

    corve around the head of the pancreas .

    It is a 'C' shapes type letter .

2. Jejunum -- It is a 2nd part of the small 

    intestine . It is about 2 meter long .

3. Ileum -- It is about 3 meter long and at          the ileocaecal valve , which control the 

    flow of the material from ileum of the 

    Caecum . The first part of the large                  intestine and prevent and back flow .

    *Function of the Small intestine*

1.  It secrete intestine juice .
2. It help in chemical digestion of prote and fat .
3. It help in the absorption of 90% nutrients.
4. Protection against infection actions HCL  in the stomach .

       

           6. Large intestine 

   The large intestine is about 1.5m long .

   beginning at the caecum in the right ileac 

   fossa and terminating at the rectum and 

   anal canal deep within the pelvis . It's             lumen is about 6.5cm in diameter large         then small intestine .

   The large intestine is devided in to -----------

   Caecum 

   Colon 

   Rectum 

   Anal canal 

1.Caecum -- It is the first part of the large         intestine . It is about 5.8cm length . It is 

   situated in the lower right part in the 

   abdomin .

2. Colon -- It is 2nd part of the large                   intestine . It is devided in to four parts ----
   (a) Ascending colon
   (b) Transverse colon
   (c) Descending colon
   (d) Sigmoid colon

3. Rectum -- It is about 2cm in length . It lies
    anterior to the sacrum and coccyx . It is
    start from sigmoid colon and end to the
    anal canal .

4. Anal canal -- It is the terminal part               which is about 2-3m in length . It contain
   network of artery or veins it provide
   important role in the excretion of coaste .

       *Function of the large intestine*

(a) Absorption
(b) Microbial activity
(c) Mass movement
(d) defecation