accessory digestive organs

Accessory Digestive Organs

Salivary glandsPancreasLiverGallbladder

Salivary Glands

• Function: produce saliva– Wets and lubricates the oral mucosa and the

ingested food (→ bolus)– Initiates digestion of carbohydrates and lipids

(amylase and lingual lipase)

Salivary Glands

• Minor salivary glands – 10% of total volume of saliva, 70% mucus

• Major salivary glands– Parotid– Submandibular (submaxillary)– Sublingual

Ductal System

• Lobes and lobules separated by connective tissue septa

• Secretory alveoli + ducts• Secretory alveoli: round, sac-like structures,

simple cuboidal epithelium resting on a basal lamina

• Ducts: intralobular, interlobular, lobar, main excretory ducts

Ductal System

• Intralobular ducts – located within the lobule– 2 segments:1.Intercalated duct – directly drains an

acinus/secretory lobule2.Striated (secretory) duct – union of intercalated

ducts

Ductal System

1. Intercalated duct• Simple squamous or simple cuboidal epithelium• Contain myoepithelial cells2. Striated duct • Simple cuboidal or simple columnar

epithelium• Exhibit basal striations• Contain myoepithelial cells

Ductal System

• Interlobular ducts – union of striated ducts, located in the connective tissue septa (between lobules)– Stratified cuboidal → stratified columnar

• Lobar ducts – drain an entire lobe– Stratified columnar epithelium

• Main excretory duct – opens into the oral cavity– Stratified squamous epithelium

Salivary Glands

Parotid Submandibular Sublingual

Location Below and anterior to the pinna of the ear, at the region of the angle of the mandible

Submandibular fossa of inner aspect of mandible, below the floor of the oral cavity

Floor of mouth, underneath the tongue (between the mandible and genioglossus muscle)

Type of Gland

Paired

Compound alveolar

Serous gland

Paired

Compound tubuloalveolar

Mixed gland

Paired

Compound tubuloalveolar

Mainly mucous gland

Salivary Glands

Parotid Gland Submandibular Sublingual

Description Connective tissue septa divide the gland into lobes

Contain adipose cells in lobes

Smaller than parotidCT septa thinner than parotid, divide the gland into lobes and lobules

Very few adipose cellsHave serous demilunes

Smallest salivary glandDuct system not as extensive as parotid and submandibular

Have some serous demilunes

Main duct Stensen’s duct Wharton’s duct Ducts of RivinusDuct of Bartholin

Serous vs Mucous Cells

Serous Cells Mucous Cells

•Pyramidal•Broad base resting on the basal lamina •Narrow apical surface•Short microvilli facing the small lumen in the center•“Grape attached to its stem”

(stem corresponds to the duct system)

•Cuboidal to columnar•Oval nuclei, pressed toward the bases•Most often organized as tubules, consisting of cylindrical arrays of secretory cells surrounding a lumen

Parotid Gland

Submandibular Gland

Sublingual Gland

Pancreas

• Pinkish, soft organ • 12-15 cm • Stretched transversely

across the posterior abdominal wall from the duodenum to the spleen

• Posterior to stomach• Mostly retroperitoneal

Pancreas

• Head• Tail• Body• Main pancreatic duct

(duct of Wirsung)• Accessory pancreatic

duct (duct of Santorini)

Pancreas

• Main functions: – Exocrine: produces digestive enzymes that act in

the small intestine (cells arranged in acini)– Endocrine: synthesizes and secretes hormones

(insulin and glucagon) into the bloodstream (islets of Langerhans)

Exocrine Pancreas

• Thin connective tissue septa divide the pancreas into lobules

• Acini surrounded by a basal lamina that is supported by a delicate sheath of reticular fibers

• Has rich capillary network (essential for the secretory process)

Pancreatic Acini

• 40-50 closely packed low columnar or pyramidal cells

• Narrow lumen, rest on basal lamina• Nucleus: round with 1 or more nucleoli• Cytoplasm:– Supranuclear – eosinophilic granules (zymogen

granules)– Infranuclear (basal) – abundant rough ER

Pancreas vs. Parotid

• Pancreas: – Absence of striated ducts– Presence of the islets of Langerhans – Initial portions of intercalated ducts penetrate the

lumens of the acini (centroacinar cells – constitute the intra-acinar portion of the intercalated duct

Pancreas

Pancreas