6.1-DIGESTIVE_SYSTEM

SPLANCHNOLOGY

Study of visceral organs of the digestive, respiratory and urogenital system.

DIGESTIVE SYSTEM (three essential components)

1. Digestive tract

2. Digestive glands

3. Accessory Digestive Structures

Parts of the Digestive Tract/ Alimentary Canal

1. Mouth

2. Pharynx

3. Esophagus

4. Stomach

5. Small Intestine

6. Colon (Part of large intestine)

7. Large Intestine

8. Rectum

9. Terminal Segment (Anus)

Parts of Digestive Glands

1. Salivary Glands

2. Liver (temporarily stores bile in the

   gallbladder)

3. Pancreas (secretes hormones, and

   pancreatic juices)
   

Parts of Accessory Digestive Structures

1. Teeth

2. Tongue

3. Cheeks

4. Lips

5. Palate

MOUTH (bounded by)

• Dorsally: soft and hard palate

• Ventrally: Lower set of teeth & floor of mouth

• Laterally: Cheeks

• Rostrally: Upper & lower lip

• Caudally: Oropharynx

PHARYNX

Serves as a common passageway for food, water, and air

Pharynx apperatures

1. Nasopharynx

2. Oropharynx

3. Laryngopharynx

Pharyngeal Proper

Common passageway for digestive and respiratory tract

ESOPHAGUS

A long muscular tube that serves as a passageway for bolus.

Portions/Segments of Esophagus

1. Cervical

2. Thoracic

3. Abdominal

Concentric layers of Esophagus (inner to outer)

• Tunica mucosa

• Tunica submucosa

• Tunica muscularis

• Tunica adventitita

STOMACH

A muscular bag which temporarily stores chyle.

Chyle

ingesta inside the stomach upon mixing of bolus with gastric juice. It is strongly acidic due to the presence of HCl

chief cells

produce pepsinogens (active pepsin)

parietal cells

HCl

4 parts of the stomach

1. Cardia

2. Fundus

3. Body

4. Pylorus

2 Sphincters of the stomach

• Cardiac sphincter

• Pyloric sphincter

4 Layers of the stomach (inner to outer)

1. Tunica mucosa

2. Tunica submucosa

3. Tunica muscularis

4. Tunica serosa

Surfaces of the stomach

• Parietal

• Visceral

Curvatures of the stomach

• Greater- left extremity

• Lesser- right extremity

Segments of SMALL INTESTINE

• Duodenum

• Jejunum

• Ileum

Duodenum

First and most fixed segment of intestine where the bile duct and pancreatic duct empty the biliary secretion and pancreatic juices.

Jejunum

Longest and the most movable. Also the most absorptive segment of the small intestine.

Ileum

The terminal or last segment of the intestine. (peyer’s patches)

Peyer’s patches

It has a certain role in defenses of the intestine against microorganisms.

Segments of the LARGE INTESTINE

1. Cecum

2. Colon

3. Rectum

Cecum

counterpart of appendix in humans. It is a vestigial or rudimentary structure in humans. But may serve as a site of fermentation in some animals

Colon

the longest segment of the large intestine. It is the main site for water and electrolyte reabsorption.

Rectum

the last segment of the intestine and the temporary storage site of feces prior to defecation.

ANUS

Terminal segment of the alimentary canal

Sphincter muscles of the anus

Ani externi et interni

SALIVARY GLANDS

The three pairs of large glands situated on the sides of the face and the adjacent part of the neck.

SALIVARY GLANDS (large glands)

1. Parotid

2. Sublingual

3. Submandibular

4. Zygomatic/Orbital

Classifications of salivary glands

• Serous

• Mucous

• Mixed

LIVER

The nutritional guardian of the body

Lobes of the liver

• left hepatic

• right hepatic

• median/quadrate

• caudate lobe

Lobes of liver in dogs

• 7-8

PANCREAS

A gland situated between duodenal loops.

TEETH

It is essential for cutting, grinding, or chewing the food.

Types of teeth

1. Incisor

2. Canine

3. Premolar

4. Molar

3 Surfaces of the teeth

1. Occlusal

2. Labial

3. Lingual

Layers of teeth

• Cementum

• Enamel

• Dentine

• Pulp cavity

Regions of teeth

• Crown

• Neck

• Body

TONGUE

It is supported in a muscular sling formed by the mylohyoid muscles

Parts of the tongue

• Root

• Body

• Apex

SOFT PALATE

Has a base, free border

surfaces of soft palate

• Oral

• Aboral

HARD PALATE

is bounded in front and on either side by the alveolar arches. It is continuous with the soft palate behind.

The bony basis of the hard palate

• Premaxillae

• Maxillae

• Horizontal part of palatine bone