Digestive system: Accessory organs lecture 25

Accessory organs

Accessory organs produce secretory products and deposit them into GI tract to assist with digestion and nutrient absorption

Accessory organs within the body

• Liver

• Gallbladder

• Pancreas

• Sublingual salivary glands

• Submandibular salivary glands

The products of accessory digestive organs are deposited into ducts to be carried to their destinations called

Exocrine glands

General function of accessory digestive organs

Aid in digestion and absorption of food and nutrients

Salivary glands: functions

• Three major clusters, but smaller glands are also distributed throughout oral cavity

• Product (saliva) deposited into the oral cavity

• Saliva functions: moisten and lubricate food, digestion of starches(amylase), protection (antimicrobial enzymes)

Structure of salivary glands

• Ducts branch out into glands

• 2 types of glands: acinar serous glands and tubular mucous glands

• Myoepithelial cells surround glands

3 major salivary glands

• Parotid

• Submandibular

• Sublingual

Salivary gland - Parotid:

only serous glands, producing abundant amylase for starch digestion

Salivary gland - Submandibular

a mix of serous and mucous glands, producing amylase, mucus, as well as lysozyme – which has antimicrobial properties

Salivary gland - Sublingual:

mostly mucous glands, but with some serous glands – produce mostly mucus, along with some amylase and lysozyme

The ducts of the salivary glands

Intercalated ducts leading from glands merge into larger striated ducts

• Intercalated: simple cubiodal epithelium

• Striated: simple columnar with basal striations (rich with mitochondria)

Most salivary glands contain a mixture of?

Mucous and serous glands

Mucous and serous glands DO produce?

Different secretions

Parotid glands only contain

Serous glands

Pancreas: general structure

• Thin outer capsule of CT, and some internal CT septa to divide interior into lobules

• Interior occupied by secretory glands and their ducts, supported by reticular fibers

• Note that internal ducts merge to eventually form one or two large ducts that deposit secretory products into the lumen of the small

Pancreas function

• Both an exocrine and an endocrine organ, although exocrine tissue is far more abundant than endocrine tissue

• Exocrine tissue produces multiple types of digestive enzymes, and ducts deposit the enzymes into the small intestine lumen to assist with chemical digestion

Pancreatic exocrine products

Products are deposited into lumen of small intestine:

Digestive enzymes:

• Acinar cells in glands secrete inactive forms (zymogens), which are later activated in intestinal lumen

• Include proteases, amylase, lipases, and nucleases

Bicarbonate ions:

• Produced by centroacinar cells in ducts

• Help to neutralize pH of chyme in small intestine lumen

Pancreatic exocrine glands

• Branching acinar glands with acinar cells organized around small lumens

– Acinar cells are polarized, with round, basal nuclei, basophilic basal cytoplasm (abundant RER), and acidophilic apical cytoplasm (secretory granules)

• Centroacinar cells found at junction of acinar cells and duct cells; pale cytoplasm