ANAPHY FINALS DIGESTIVE SYSTEM

Tunica Mucosa

Absorptive, secretory, and protective

Epithelium, Lamina Propria, Muscularis Mucosa

Tunica Mucosa 3 layers

simple columnar except mouth, pharynx, esophagus, and lower anus which are lined by stratified squamous non-keratinized.

Tunica Mucosa type of epithelium

Lamina Propria

Loose areolar tissue

Muscularis Mucosa

Made up of smooth muscles

Submucosa

Connective tissue consisting of the following:

• Blood Vessels

• Lymphatics

• NMajor function is nutritive and protectiveerves

Submucosa

Major function is nutritive and protective

• Inner Circular

• Outer Longitudinal Muscle Layer

Tunica Muscularis layers of smooth muscles:

• Inner Oblique

• Middle Circular

• Outer Longitudinal Muscle Layer

Tunica Muscularis stomach layers

Tunica Serosa

Visceral Peritoneum

Tunica Serosa

It is a single layer of simple squamous epithelium which secretes a small amount of serous lubricating fluid which reduces friction among the GI tract organs and the body wall.

1. Gastrointestinal Tract

2. Accessory Digestive Organ

Two Subdivisions of the Digestive System

i. Mouth

ii. Pharynx

iii. Esophagus

iv. Stomach

v. Small intestines

vi. Large intestines

vii. Anus

Parts of GIT

a. Salivary glands

b. Liver and Gallbladder

c. Pancreas

Accessory Digestive Organs

Oral Vestibule

Space bounded anteriorly by lips and cheeks and posteriorly by teeth and gums

Oral Cavity Proper

➢ Space bounded by gums and teeth

➢ The floor is the tongue

➢ The roof is the hard and soft palate

Consists of 20 teeth, 5 in each quadrant:

• 2 Incisors

• 1 Canine

• 2 Molars

Decidous Teeth or Temporary (Milk) Teeth consists of:

Decidous Teeth or Temporary (Milk) Teeth

Erupt on the average between 6 and 24 months after birth and are usually shed between the ages of 6 and 12 years old

There are 32 permanent teeth in a full set, 8 in each quadrant:

• 2 Incisors

• 1 Canine

• 2 Premolars

• 3 Molars

Permanent Teeth consists of:

Permanent Teeth

Eruption of the third molars, or wisdom teeth is delayed until after the age of 18.

Tongue

Chief organ of taste, important in speech, mastication, and deglutition,

Vallate

Largest papillae

Foliate

Papillae that is sensitive, on the sides

Fungiform

Mushroom-shaped papillae

Filiform

Papillae that has no taste buds

Tastebuds

Sensory organs of taste especially numerous around vallate papillae

General Sensory

➢ Lingual (Branch of CN V) – Anterior 2/3 of tongue

➢ Glossopharyngeal (CN IX) – Posterior 1/3 of tongue

➢ Vagus (CN X) – Epiglottic Area

Special Sensory

➢ Anterior 2/3 – Chorda Tympani from CN VII

➢ Posterior 1/3 – Glossopharyngeal (CN IX)

Motor

➢ To intrinsic and extrinsic muscles of tongue

➢ Hypoglossal (CN XII)

Salivary Glands

Secretions (salivary amylase) poured in the oral cavity starts digestion of carbohydrates.

1. Parotid

2. Submandibular

3. Sublingual

3 Major Pairs of Salivary Glands

Parotid gland

Largest pair, lies on the posterior border of ramus of mandible

Parotid gland

Secretion is purely serous

Stensen’s duct

Parotid gland Duct

Stensen’s duct

opens into the vestibule of mouth opposite second molar tooth

mumps or parotitis

Parotid Viral inflammation

Facial Nerve

Parotid Important structure embedded:

Submandibular gland

Second Largest pair of salivary gland

Submandibular gland

Mixed serous and mucus gland, more of serous

Wharton’s duct

Submandibular gland duct

Wharton’s duct

opens at sublingual papillae

Sublingual Gland

Smallest of three salivary glands

Sublingual Gland

Mixed serous and mucous but more of mucous

Duct of Rivinus

Bartholin’s duct

Sublingual ducts

Duct of Rivinus

small; opens at summit of sublingual fold

Bartholin’s duct

large; opens into sublingual papillae

Pharynx

Common passage for food, fluid, and air

1. Nasopharynx or epipharynx

2. Oropharynx or mesopharynx

3. Laryngopharynx

3 Parts of the Pharynx

Nasopharynx or epipharynx

Located behind the nasal cavity

Oropharynx or mesopharynx

Located behind the oral cavity proper

Oropharynx or mesopharynx

Palatine tonsil bounded by palatoglossal and palatopharyngeal fold

Laryngopharynx

Located behind larynx

Laryngopharynx

Continuous with the esophagus

Esophagus

A muscular tube extending from the pharynx to the stomach for a distance of about 10 inches/25 cm long

Esophagus

It is posterior to the trachea and anterior to the vertebral column; it passes through the diaphragm in front of the aorta to enter the stomach.

At the pharyngo-esophageal junction

Known as the Upper Esophageal Sphincter (UES)

When it enters the diaphragm

Known as the Lower Esophageal Sphincter (LES)

Lower Esophageal Sphincter (LES)

is a physiologic sphincter

1. At the pharyngo-esophageal junction

2. When left main bronchus crosses esophagus

3. When it enters the diaphragm

3 Anatomical Constrictions of Esophagus

Swallowing

➢ Tongue moves upward and backward

➢ Soft palate closes the nasopharynx

➢ Epiglottis closes the laryngeal inlet

➢ Pharynx contracts

➢ Bolus enters the esophagus

1. Voluntary Phase

2. Pharyngeal Phase

3. Esophageal Phase

3 Phases of Swallowing

Voluntary Phase

Bolus is formed in the mouth

Voluntary Phase

Bolus is pushed by the tongue against the hard and the soft palate and posteriorly towards the oropharynx

Pharyngeal Phase

Controlled by reflex

Pharyngeal Phase

Initiated when the bolus of food stimulates the receptors in oropharynx

Esophageal Phase

Responsible for moving for food from pharynx to the stomach

1. Nasopharynx closes, at the same time breathing is inhibited

2. Laryngeal muscles contract to close the epiglottis and elevate the larynx

3. Peristalsis sweeps in the pharynx to propel food with simultaneous opening of the esophageal sphincter.

Events during Swallowing

medulla

The Swallowing reflex is coordinated in the

Stomach

Located within peritoneal cavity in the left superior part of the abdomen

Stomach

With greater and lesser curvatures

Cardiac Region

Area surrounding the point of entry of food in the stomach

Fundus

Expanded portion found on the left border, lateral to the cardiac region

Lesser Curvature

Concave medial border of the stomach

Greater Curvature

Convex lateral border of the stomach

Pylorus

Tubular portion

Pylorus

Terminal part, continuous with the small intestine through the pyloric sphincter

Pylorus

part of the stomach that is the most dilated portion of the digestive tract, lies under the diaphragm just below the costal margin in the upper abdomen.

Pylorus

It serves mainly as a storage and mixing chamber for food prior to passage into the duodenum (the first part of the small intestine), but some digestion takes place and the mixed, partially digested food is reduced to a semifluid mass.

Parietal Cell

Secretes HCl and intrinsic factor

Chief Cell

Secretes Pepsin

Mucus Neck Cell

Secretes Mucus

G Cell (Endocrine Cells)

Secretes Gastrin

Small Intestines

➢ Longest

➢ 20ft (about 6 meters)

Duodenum

C-shaped part of the small intestine

Duodenum

Where the Common Bile Duct (CBD) and main and accessory pancreatic ducts enter

a. Superior (1st part)

b. Descending (2nd part)

c. Transverse/Horizontal (3rd part)

d. Ascending (4th part)

4 Subdivisions of the Duodenum

Superior (1st part of the Duodenum)

“Duodenal Bulb”

Descending (2nd part of the Duodenum)

Contains the greater and lesser duodenal papilla

Ascending (4th part of the Duodenum)

Ends in the duodeno-jejunal function

• Major Duodenal Papilla (Ampulla of Vater

• With sphincter of Oddi around common duct and main pancreatic duct of Wirsung

• Minor Duodenal of Accessory Pancreatic duct of Santorini

Gross Structural Characteristics of the small intestines

Jejunum

➢ Located at the left upper quadrant

➢ Upper 2/5 (8ft)

➢ More vascular wider and thicker than ileum

Ileum

➢ Longest, found at the right lower quadrant

➢ Lower 3/5 (12ft)

➢ Provided with Peyer’s patches or aggregated lymph nodules

Microvilli

Minute projections of the surface plasma membrane in the lining epithelium

Villi

Fingerlike projections of the mucosa

Plicae Circulates/Valves of Kerkring

Deep folds of mucosa and submucosa

Ligament of Treitz

Bond of fibrous muscular tissue which extends from the duodenojejunal angle into the right crus of the diaphragm

Ligament of Treitz

Connects the duodenojejunal flexure to the right crus of the diaphragm

Cecum

Widest part of the large intestine

Vermiform Appendix

Located posteromedial to cecum

Sigmoid Colon

S-shaped part of the large intestine