Page 661 - Textbook of Pathology, 6th Edition

exocrine and endocrine parts. The endocrine part of the gland viscidosis) and associated with increased concentrations of 645
is dealt with in Chapter 27 while the exocrine gland is electrolytes in the eccrine glands. The terms ‘cystic fibrosis’
considered here. The whole of pancreas, exocrine and and ‘fibrocystic disease’ are preferable over ‘mucoviscidosis’
endocrine, is embryologically derived from the foregut in view of the main pathologic change of fibrosis produced
endoderm. as a result of obstruction of the passages by viscid mucous
ANATOMY. The pancreas lies obliquely in the concavity of secretions.
the duodenum as an elongated structure about 15 cm in The disease is transmitted as an autosomal recessive trait
length and 100 gm in weight (see Fig. 21.1). It is subdivided with apparent clinical features in homozygotes only. The
into 3 topographic zones: defect is a genetic mutation in CFTR gene, acronym for
1. The head lying in the concavity of the duodenum and the coding protein for cystic fibrosis transmembrane conductance
uncinate process projecting from the head. regulator located on chromosome 7. It is quite common in
2. The body comprises the main part of the gland. the whites (1 per 2000 livebirths). The clinical manifestations
3. The tail is the thin, tapering part of the gland towards may appear at birth or later in adolescence and pertain to
the hilum of the spleen. multiple organs and systems such as pancreatic insufficiency,
intestinal obstruction, steatorrhoea, malnutrition, hepatic
HISTOLOGY. The exocrine pancreas constitutes 80 to 85% cirrhosis and respiratory complications.
of the total gland, while the endocrine pancreas comprises
the remaining part. MORPHOLOGIC FEATURES. Depending upon the
The exocrine part is divided into rhomboid lobules severity of involvement and the organs affected, the
separated by thin fibrous tissue septa containing blood pathologic changes are variable. Most of the changes are
vessels, lymphatics, nerves and ducts. Each lobule is produced as a result of obstruction by viscid mucous.
composed of numerous acini. The acini are lined by pyramid- 1. Pancreas. The pancreas is almost invariably involved
shaped columnar epithelial cells. These secretory epithelial in cystic fibrosis.
cells have microvilli projecting into the lumen from their
surface. The apical portions of these cells contain zymogen Grossly, pancreatic lobules are ovoid rather than
granules in their cytoplasm, while the basal region is deeply rhomboid. Fatty replacement of the pancreas and grossly CHAPTER 21
basophilic and free of zymogen granules. The zymogen visible cysts may be seen.
granules are membrane-bound sacs which fuse with the Microscopically, the lobular architecture of pancreatic
plasma membrane and are then released into the lumina of parenchyma is maintained. There is increased interlobular
the acini. The secretions are carried from the acini by fine fibrosis. The acini are atrophic and many of the acinar
ductal branches into the small ducts in the lobules and ducts contain laminated, eosinophilic concretions. Rarely,
eventually into the main pancreatic duct. The main inflammation, fat necrosis and cyst formation may be seen.
pancreatic duct is formed by fusion of the ventral duct with The islet tissue (endocrine pancreas) generally remains
the dorsal duct; the latter also called the duct of Wirsung, intact. Atrophy of the exocrine pancreas may cause
provides the main drainage for pancreatic secretions into the impaired fat absorption, steatorrhoea, intestinal
duodenum. The pancreatic secretions are delivered into the obstruction and avitaminosis A.
second part of the duodenum either by a combined opening 2. Liver. The bile canaliculi are plugged by viscid
of the pancreatic and bile ducts in the ampulla of Vater, or mucous which may cause diffuse fatty change, portal
less often both open separately into the duodenum. fibrosis and ductular proliferation. More severe involve-
Occasionally, the proximal part of the dorsal duct persists ment may cause biliary cirrhosis (page 625).
as the duct of Santorini.
3. Respiratory tract. Changes in the respiratory passages The Liver, Biliary Tract and Exocrine Pancreas
FUNCTIONS. The main functions of the exocrine pancreas are seen in almost all typical cases of cystic fibrosis. The
is the alkaline secretion of digestive enzymes prominent viscid mucous secretions of the submucosal glands of the
among which are trypsin, chymotrypsin, elastase, amylase, respiratory tract cause obstruction, dilatation and infection
lipase and phospholipase. of the airways. The changes include chronic bronchitis,
bronchiectasis, bronchiolitis, bronchiolectasis,
DEVELOPMENTAL ANOMALIES peribronchiolar pneumonia and inflammatory nasal
polyps.
The significant developmental anomalies of the pancreas are
ectopic or aberrant pancreatic tissue in Meckel’s diverticulum 4. Salivary glands. Pathologic changes in the salivary
(page 561), anomalies of the ducts, and cystic fibrosis. Only glands are similar to those in pancreas and include
the last named requires elaboration here. obstruction of the ducts, dilatation, fibrosis and glandular
atrophy.
Cystic Fibrosis 5. Sweat glands. Hypersecretion of sodium and chloride
in the sweat observed in these patients may be reflected
Cystic fibrosis of the pancreas or fibrocystic disease is a pathologically by diminished vacuolation of the cells of
hereditary disorder characterised by viscid mucous eccrine glands.
secretions in all the exocrine glands of the body (muco-