By –

Mr ASHOK BISHNOI

Lecturer

2 groups of organs composed of digestive system

It is continuous tube that extends from the mouth to anus through the thoracic, abdominal & pelvic cavities.

1.Gastrointestinal tract/ Alimentary canal

◦ Mouth

◦ Pharynx

◦ Esophagus

◦ Stomach

◦ Small intestine

◦ Large intestine

◦ Rectum

◦ Anal canal

◦ Anus

The length of GI tract is about 5-7 meters (16.5-23 ft) in a living person.

It is long in Cadaver about 7-9 meters (23-29.5 ft)

Supply secretions contributing to the breakdown of food

2. Accessory digestive organs

◦ Teeth

◦ Lips

◦ Cheeks

◦ Tongue

◦ Salivary glands (3 pair)

◦ Gallbladder

◦ Liver

◦ Pancreas

Teeth aid in the physical breakdown of food & tongue assist in chewing & swallowing.

The other accessory digestive organs never come in to direct contact with food.

They produce secretion in the chemical breakdown of food

1. Ingestion-Taking food in to mouth

2. Secretion- Relies of H2o,acid & enzymes in to lumen of GI tract.

3. Mixing & propulsion

4. Digestion- Mechanical breakdown of food by Mastication

Chemical digestion by Enzymes

5. Absorption- Passage of digested product from the GI tract in to blood.

6. Defecation- The elimination of faeces from the GI tract

Function of DS;-

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Structure of alimentary canal:-

The wall of GI tract from the lower oesophagus to the anal canal.

It has the “4” layers of tissue

◦ Mucosal layer◦ Submucosal layer◦ Muscularis layer◦ Serosa layer

1.Gastrointestinal tract/ Alimentary canal

It consist of Epithelium Tissue

◦ Stratified squamous (in mouth,

esophagus & anus)

◦ Simple columnar in the rest

Function:-

◦ Protection

◦ Secretion

◦ Absorbtion

Loose connective tissue

◦ containing ,glands and lymphatic tissue

Meissner’s plexus

The secrete:-◦ Saliva from salivary gland

◦ Gastric juice from gastric gland

◦ Intestinal juice from intestinal gland

◦ Pancreatic juice from pancreas

◦ Bile from liver

Skeletal muscle = voluntary control

◦ in mouth, pharynx , upper esophagus and

anus

◦ control over swallowing and defecation

Smooth muscle = involuntary control

◦ inner circular fibers & outer longitudinal

fibers

◦ mixes, crushes & propels food along by

peristalsis

4.Serosa:-• It is outer layer

• Covers all organs and walls of cavities

• Secretes a serous fluid

• Consists of connective tissue .

Peritoneum

◦ Cavity within the abdomen

Formed by a

◦ Parietal layer- Which line the abdominal wall

◦ Visceral layer covers organs with in the abdomen & pelvic

cavity

Peritoneal cavity

◦ potential space containing a bit of serous fluid

The path of food:oral cavity/teeth/salivary glands

oropharynx/epiglottis

oesophagus

stomach

small intestine: duodenum

small intestine: ileum

small intestine: jejunum

large intestine: ascending colon

large intestine: transverse colon

large intestine: descending colon

sigmoid colon rectum anus

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It is the main window of G.I.tract

From mouth to pharynx is called oral cavity

Mouth or oral cavity is bounded by muscle & bone.

Lips- Orbicularis orismuscle

Cheeks – Buccinatormuscle

Mouth/Oral cavity:-

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The vestibule :-is the space between gums & checks.

The oral cavity:- It is the space contained within the upper and lower dental arches.

Uvula:- Is a carved fold of muscle covered with mucus membrane hanging down from middle palate.

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Teeth:-

Called “dentition” (like dentist)

Teeth live in sockets (alveoli) in the gum-covered margins of the mandible and maxilla

Chewing: raising and lowering the mandible and moving it from side to side while tongue positions food between teeth

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Two sets1. Temporary/Milk/Primary

/deciduous teeth1. “Baby” teeth

2. Start at 6 months

3. 20 are out by about 2 years

4. Fall out between 2-6 years

2. Permanent: 32 total1. All but 3rd set of molars by

end of adolescence

2. 3rd set = “wisdom teeth”1. Variable

3. Some can be “impacted” (imbedded in bone)

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Incisors: chisel-shaped for chopping off pieces

Canines: cone shaped to tear and pierce

Premolars (bicuspids) and Molars - broad crowns with

4-5 rounded cusps for grinding

incisor

canine

premolar

molar

Cusps are surface bumps

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Two main regionsA. Crown (exposed)B. Root (in socket)C. Meet at neck

Enamel ◦ 99% calcium crystals◦ Hardest substance in

body Dentin – bulk of the

tooth (bone-like but harder than bone, with collagen and mineral)

Pulp cavity with vessels and nerves◦ Root canal: the part of

the pulp in the root

A

B

C

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Cementum – bone layer of tooth root◦ Attaches tooth to

periodontal ligament

Periodontal ligament◦ Anchors tooth in boney

socket of the jaw◦ Continuous with

gingiva (gums)

Cavities or caries -rot

Plaque – film of sugar, bacteria and debris

A

B

C

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Intrinsic salivary glands – within mucosa◦ Secrete saliva all the

time to keep mouth moist

Extrinsic salivary glands◦ Paired (2 each)

Parotid

Submandibular

Sublingual

◦ External to mouth◦ Ducts to mouth◦ Secrete saliva only right

before or during eating

Saliva: mixture of water, ions, mucus, enzymeskeep mouth moistdissolves food so can be tastedmoistens foodstarts enzymatic digestionbuffers acidantibacterial and antiviral

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Parotids* - largest (think mumps)◦ Facial nerve branch at risk during surgery here

Submandibular # - medial surface mandible

Sublingual + - under tongue; floor of mouth

Compound = duct branchesTubo = tubesAlveolar = sacs

*

#

+

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Oropharynx and laryngopharynx◦ Stratified squamous

epithelium

Three constrictor muscles*◦ Sequentially squeeze

bolus of food into esophagus

◦ Are skeletal muscles Voluntary action

Vagus nerve (X)

___oropharynx

___laryngopharynx

*

*

*