Chapter Summary

I. MAJOR SALIVARY GLANDS

Three major salivary glands are associated with the oral cavity. These are the parotid, submandibular, and sublingual glands.

A. Parotid Gland

The parotid gland is a purely serous compound tubuloalveolar gland whose capsule sends septa (frequently containing adipose cells) into the substance of the gland, dividing it into lobes and lobules. Serous acini, surrounded by myoepithelial cells, deliver their secretions into intercalated ducts.

B. Submandibular Gland

This compound tubuloalveolar gland is mostly serous, although it contains enough mucous units, capped by serous demilunes, to manufacture a mixed secretion. Acini are surrounded by myoepithelial (basket) cells. The capsule sends septa into the substance of the gland, subdividing it into lobes and lobules. The duct system is extensive.

C. Sublingual Gland

The sublingual gland is a compound tubuloalveolar gland whose capsule is not very definite. The gland produces a mixed secretion, possessing mostly mucous acini capped by serous demilunes and surrounded by myoepithelial (basket) cells. The intralobular duct system is not very extensive.

II. PANCREAS

The exocrine pancreas is a compound tubuloalveolar serous gland whose connective tissue capsule sends septa to divide the parenchyma into lobules. Acini present centroacinar cells, the beginning of the ducts that empty into intercalated ducts, which lead to intralobular, then interlobular ducts.The main duct receives secretory products from the interlobular ducts. The endocrine pancreas with its islets of Langerhans (composed of A, B, G, and D cells) are scattered among the serous acini.

III. LIVER

A. Capsule

Glisson’s capsule invests the liver and sends septa into the substance of the liver at the porta hepatis to subdivide the parenchyma into lobules.

B. Lobules

1. Classical Lobule

Classical lobules are hexagonal with portal areas (triads) at the periphery and a central vein in the center.Trabeculae (plates) of liver cells anastomose. Sinusoids are lined by sinusoidal lining cells and Kupffer cells (macrophages). Within the space of Disse, fat-accumulating cells may be noted. Portal areas housing bile ducts, lymph vessels, and branches of the hepatic artery and the portal vein are surrounded by terminal plates composed of hepatocytes. Bile passes peripherally within bile canaliculi, intercellular spaces between liver cells, to enter bile ductules, then canals of Hering (and cholangioles), to be delivered to bile ducts at the portal areas.

2. Portal Lobule

The apices of triangular cross sections of portal lobules are central veins. Thus, portal areas form the centers of these lobules. The portal lobule is based on bile flow.

3. Acinus of Rappaport (Liver Acinus)

The acinus of Rappaport in section is a diamond-shaped area of the liver whose long axis is the straight line between neighboring central veins and whose short axis is the intersecting line between neighboring portal areas. The liver acinus is based on blood flow.

IV. GALLBLADDER

The gallbladder is connected to the liver via its cystic duct, which joins the common hepatic duct.

A. Epithelium

The gallbladder is lined by a simple columnar epithelium.

B. Lamina Propria

The lamina propria is thrown into intricate folds that disappear in the distended gallbladder. Rokitansky-Aschoff sinuses (epithelial diverticula) may be present.

C. Muscularis Externa

The muscularis externa is composed of an obliquely oriented smooth muscle layer.

D. Serosa

Adventitia attaches the gallbladder to the capsule of the liver, whereas serosa covers the remaining surface.

CHAPTER OUTLINE

Graphics

Graphic 16-1 Uriniferous Tubules p. 390

Graphic 16-2 Renal Corpuscle p. 391

Tables

Plates