Human Physiology, 14th edition (2016)

642 Chapter 18

Figure 18.25

Pancreatic juice and

bile are secreted into

the duodenum. The

pancreatic duct joins

the common bile duct

to empty its secretions

through the duodenal

papilla into the

duodenum. The release

of bile and pancreatic

juice into the duodenum

is controlled by the

sphincter of ampulla

(sphincter of Oddi).

Pancreatic acinus

Pancreatic islet

(of Langerhans)

Pancreatic duct

Pancreatic

juice

Pancreas

Duodenum

Duodenal
papilla

Gallbladder

Common bile
duct

Cystic duct

Hepatic ducts

CLINICAL APPLICATION

Gallstones are hard mineral deposits that form in the gall-

bladder and generally have cholesterol as their major com-

ponent (indeed, cholesterol was discovered in 1789 when it

was isolated from gallstones). Cholesterol is present in bile

at 2 million times its water solubility because the cholesterol

molecules cluster with bile salts and lecithin in the hydropho-

bic centers of aggregates called micelles. Gallstones are pro-

duced when the liver secretes enough cholesterol to create

a supersaturated solution, and cholesterol crystals, together

with mucus secreted by the gallbladder, can form a sludge

that may be visible in an ultrasound. Sometimes more siz-

able gallstones are produced ( fig.  18.26 ) that can block the

hepatic, cystic, or common bile ducts and evoke the pain

and nausea of biliary colic. Gallstones are usually detected

by abdominal ultrasound, and the symptoms they produce

are usually ended with surgical removal of the gallbladder

by laparoscopic cholecystectomy, which may or may not be

robot-assisted.

Clinical Investigation CLUES

George was obese and lost weight rapidly as a result

of his bariatric surgery, making him more susceptible to

developing gallstones.

• What are gallstones, and how are they produced?


• How do gallstones account for George’s
  symptoms?

Figure 18.26 Gallstones. ( a ) A radiograph of a

gallbladder that contains gallstones (biliary calculi). ( b ) A

posterior view of a gallbladder that has been surgically removed

(cholecystectomy) and cut open to reveal its gallstones.

(a)

(b)