CHAPTER 29
Transport & Metabolic Functions of the Liver 487CHAPTER SUMMARY
■
The liver conducts a huge number of metabolic reactions and
serves to detoxify and dispose of many exogenous substances, as
well as metabolites endogenous to the body that would be harm-
ful if allowed to accumulate.
■
The structure of the liver is such that it can filter large volumes
of blood and remove even hydrophobic substances that are
protein-bound. This function is provided for by a fenestrated
endothelium. The liver also receives essentially all venous blood
from the intestine prior to its delivery to the remainder of the
body.
■
The liver serves to buffer blood glucose, synthesize the majority
of plasma proteins, contribute to lipid metabolism, and preserve
cholesterol homeostasis.
■
Bilirubin is an end product of heme metabolism that is glucu-
ronidated by the hepatocyte to permit its excretion in bile. Bili-
rubin and its metabolites impart color to the bile and stools.
■
The liver removes ammonia from the blood and converts it to
urea for excretion by the kidneys. An accumulation of ammonia
as well as other toxins causes hepatic encephalopathy in the
setting of liver failure.
■
Bile contains substances actively secreted across the canalicular
membrane by hepatocytes, and notably bile acids, phosphatidyl-
choline, and cholesterol. The composition of bile is modified as
it passes through the bile ducts and is stored in the gallbladder.
Gallbladder contraction is regulated to coordinate bile availabil-
ity with the timing of meals.MULTIPLE-CHOICE QUESTIONS
For all questions, select the single best answer unless otherwise directed.
- Removal of the entire colon would be expected to cause
A) death.
B) megaloblastic anemia.
C) severe malnutrition.
D) a decrease in the blood level of ammonia in patients with
cirrhosis of the liver.
E) decreased urinary urobilinogen.
2. After complete hepatectomy, a rise would be expected in the
blood level of
A) glucose.
B) fibrinogen.
C) 25-hydroxycholecalciferol.
D) conjugated bilirubin.
E) estrogens.
3. Which of the following cell types protects against sepsis secon-
dary to translocation of intestinal bacteria?
A) hepatic stellate cell
B) cholangiocyte
C) Kupffer cell
D) hepatocyte
E) gallbladder epithelial cell
4. P450s (CYPs) are found in many parts of the body. In which of
the following do they
not
play an important role?
A) bile acid formation
B) carcinogenesis
C) steroid hormone formation
D) detoxification of drugs
E) glycogen synthesis
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