Introduction of gastrointestinal system

for BDS 2nd yearDr Laxman Khanal

Introduction

1. Composed of GI tract and accessory organs2. Breaks down ingested food for use by the

body3. Digestion occurs by mechanical and chemical

mechanisms4. Excretes waste products or feces through

process of defecation

1. Ingestion2. Secretion3. Mixing and

propulsion• Motility

4. Digestion• Mechanical• chemical

5. Absorption6. Defecation

Topographic Divisions

• four-quadrant topographical pattern

• horizontal– transumbilical plane – between intervertebral

disc LIII and LIV

• vertical median plane

Nine quadrant pattern

Horizontal planes• Subcostal plane or

transplyloric plane• intertubercular planeVertical planes• two Midclavicular

plane

• Epigastric region• R/L hypochondrium

region• Umbilical region• R/L lumbar region• Pelvic region• R/L inguinal region

Wall of abdominal cavityAnteriolateral

abdominal wall• Three flat muscle– external oblique– Internal oblique– Transversus abdominus

• Two vertical muscle– Rectus abdominus– Pyramidalis

• Fascia transversalis• Parietal peritoneum

Posterior abdominal wall

• diaphragm• Rib 11/12• Lumbar vertebra• Sacrum• Ilium• Psoas major/minor• Qaudratus lumborum• iliacus

Components

Gastrointestinal tube• Oropharynx• Laryngopharynx• Esophagus• Stomach• Small intestine • Large intestine

Accessory organs• Teeth• Tongue• Salivary glands• Liver• Gallbladder• Pancreas

Layers of GIT

Same in all areas of GI tract• From deep to superficial:• Mucosa• Submucosa• Muscular layer• Serosa layer

Layers of GIT

• Mucosa– Epithelium

• Type varies – Lamina propria – areolar connective tissue

• MALT – mucus-associated lymphatic tissue– Muscularis mucosae – smooth muscle

• Submucosa– Areolar connective tissue– Blood and lymphatic vessels– Neurons – submucosal plexus

Layers of GIT

• Muscular layer– Skeletal and smooth muscle– Outer longitudinal and inner circular– Neurons – myenteric plexus

• Serosa– Areolar and simple squamous epithelium– Visceral peritoneum

Peritoneum

• Developed from the splitting of the lateral plate mesoderm.

• Mesothelium• Parietal peritoneum• Visceral peritoneum• Peritoneal cavity• Retroperitoneal

Peritoneal folds

• Greater omentum– Adipose tissue

• Falciform ligament– Liver to anterior abdominal wall

• Lesser omentum• Mesentery– Small intestine to posterior abdominal wall

• Mesocolon

Accessory organs

• Fauces• Hard and soft palate• Uvula• Palatoglossal arch• palatopharyngeal arch

MOUTH

• Cheeks• Lips / labia• Labial frenulum• Orbicularis oris• Vestibule• Oral cavity proper

Accessory organs

TONGUE

• Skeletal muscle • mucous membrane• form floor of oral cavity• Extrinsic muscles• Intrinsic muscles• Lingual frenulum

• Papillae– Fungiform– Filiform– Circumvallate– Foliate

• Lingual glands– Lingual lipase

Accessory organs SALIVARY GLAND Release saliva to oral

cavity3 pairs of salivary glands• Parotid• Submandibular• SublingualSalivation controlled by

autonomic nervous system

PH- 6.8 to 7Composition

• 99.5 % water• 0.5% other solutes– Ions– Mucus– Immunoglobulin A– Enzymes

Vessels , Nerves and Ductscomponents Parotid Submandibular sublingual

Artery ECA Facial (submental branch)

Facial and lingual

Vein EJV Facial and lingual Facial and lingual

Nerve (parasympathetic)

IX( otic ganglion) VII(submandibular ganglion)

VII(submandibular ganglion)

Nerve(sympathetic)

Sup cervical ganglion

Sup cervical ganglion

Sup cervical ganglion

Duct Stenson’s duct Wharton’s duct Bartholin’s ducts

Accessory organs

TEETH• Carry out mechanical

digestion by mastication

• External regions1. Crown2. Root3. Neck

• Internal components1. Enamel2. Dentin3. Cementum4. Pulp cavity• Root canals• Apical foramen

PANCREAS

• Produces secretions to aid digestion • Head• Body• Tail• Pancreatic duct /duct of Wirsung– Hepatopancreatic ampulla– Sphincter of the heatopancreatic ampulla (sphincter of

(Oddi)• Regulates passage of pancreatic juice and bile

• Accessory duct (duct of Santorini)

Pancreas

99% is exocrine that secrets pancreatic juice

1% is endocrine ( islets of Langerhans)

• Insulin• Glucagon• somatostanin

Pancreatic Juice• 1200-1500 mL/day• pH 7.1-8.2• Sodium bicarbonate• Enzymes– Pancreatic amylase– Trypsin• Entereokinase

– Chymotrypsin– Carboxypeptidase– Elastase– Pancreatic lipase– Ribonuclease and

deoxyribonuclease

Liver and Gallbladder

• Liver is the largest gland of the body• Bile is secreted by liver and carried to the gall

bladder for temporary storage.• Right and left lobe separated by falciform

ligament.• Coronary ligaments• Round ligament (ligamentum teres)– Remnant of umbilical vein

Blood supply to the liver

Liver functions• Metabolism of:– Carbohydrates– Lipids– Proteins

• Process drugs and hormones• Excrete bilirubin• Synthesize bile salts• Storage– Glycogen– Vtamins– Minerals

• Phagocytosis• Activate Vitamin D

• End of which causes formation of endodermal lined gut tube.

• Open in both ends.• GI tube is formed during

the folding of embryo.

Esophagus

• Narrowest part of GIT after Vermiform appendix.

• Extend from the pharynx( lower border of cricoid cartilage @ C6) to stomach ( @ T11).

• Consists of 3 parts. Cervical, thoracic (longest) and abdominal ( shortest ).

• Total length – 25cm• Pierce the diaphragm at the level of T10 and

open into the cardiac end of stomach at T11.

Stomach

Small intestine

• Adapted for digestion and absorption• About 6m in length• Duodenum• Jejunum• Ileum

• Ileocecal sphincter– Connection to large intestine

Vessels of GIT

Some clinical correlation

GI bleeding:• Hematemesis ,Melena – Upper GI bleeding• Hematochezia- lower GI bleeding• Mallory-Weiss tear- Upper GI hemorrhage

may result from a tear at the gastro-esophageal junction. These tears are most common in alcoholic patients, following an episode of vomiting or retching

• Peptic Ulcer Disease Peptic ulcer disease (PUD) causes over 50% of

GI bleeding, with the most common site being the duodenum. The use of NSAIDs is the most important risk factor for the development of bleeding from PUD, although the risk can be increased Further by the use of anticoagulants, by H. pylori, and by Increased acid in such conditions as Zollinger-Ellison syndrome.