Section 1: Review - FNH 350

List the participating and accessory organs involved in digestion and absorption

Accessory organs

• Salivary glands + tongue

  • Parotid

  • Sublingual

  • Submandibular/submacillary

• Liver

• Gallbladder

• Pancreas

Organs of GI tract

• Oral cavity

• Pharynx

• Esophagus

• Stomach

• Small intestine

• Large intestine

Fill in the blanks

Structure and function of the esophagus

Structure

• 25 cm

Function

• Moves bolus oral cavity → stomach

  • Swallowing: voluntary, pharyngeal, esophageal

  • Peristalsis: moving bolus with wavelike motions

Structure and function of the stomach

• Structure

  • Flexible - rugae can let stomach expand (50 mL → 1-1.5 L)

  • 4 regions

    • 1. Cardia

    • 2. Fundus

    • 3. Body

      • Function: Passive breakdown

        • Gastric juices

        • Mix bolus with circular, longitudinal and diagonal smooth muscles

    • 4. Antrum

      • Function: Active breakdown

        • Grinds food and mix with gastric juices → chyme

          • Strong peristalsis for emptying

Label the stomach

What are the types of cells in the stomach and what do they secrete?

• Neck cells - mucus

• Chief cells - enzymes

• Parietal cells - HCl; IF

  • Denature proteins

  • Activates pepsinogen to pepsin

  • Release nutrients from organic complexes

  • Antibacterial

• G-cells - gastrin

• Somatostatin released to signal to empty

Structure and function of the small intestine

• Structure:

  • 300 m^2

  • Duodenum

    • Secrete products

  • Jejunum

  • Ileum

• Function:

  • Primary site for nutrient digestion and absorption

  • High surface area to increase contact with chyme

  • Mixing

    • Church chyme to expose chyme to enzymes

  • Propelling

What are the secretory products in the duodenum?

• Secretory products:

  • Alkaline and viscous mucus - protect mucosa from damage + neutralize acidic chyme

  • Secretin (hormone) - inhibit gastric secretions + stimulate pancreas and gallbladder secretions

  • Somatostatin (hormone) - released by D-cells, pancreas and antrum of the stomach + diminish secretion by stomach cells

What are the two movements of the small intestine?

Mixing

Propelling

Where does nutrient absorption occur in the small intestine?

• in the brush border

• some in the cytoplasm of enterocytes

What are the two types of active cells in the pancreas? What are they stimulated by?

• Duct cells + Acinar cells

• Secretin

What is the function of the gallbladder?

• concentrates

• stores

• secretes bile

What is bile? what is it for? where is it made and stored?

• green-yellow fluid

• bile acids and salts

• emulsify lipids

• made in the liver, stored in the gallbladder

What is the function of the large intestine?

absorb water

What are the nutrient absorption mechanisms?

• diffusion

• facilitated diffusion

• active transport

• pinocytosis

What is the order of food from the oral cavity to the large intestine?

oral cavity → esophagus → gastroesophageal sphincter → stomach → pyloric sphincter → duodenum → jejunum → ileum → large intestine