330
UNIT 3
Organ Systems
Acidophils
Acidophils
Acidophils
Chromophobes
Chromophobes
Chromophobes
Basophils
Basophils
Basophils
Blood
Blood
vessel
vessel
Blood
vessel
A
Figure 17-4A.
Pars distalis, adenohypophysis (anterior pitu-
itary gland).
Mallory trichrome and H&E,
3
281
The
pars distalis
, the largest part of the
adenohypophysis
, contains
two major types of cells:
chromophobes
and
chromophils
.
Chro-
mophobes
are so named because the cytoplasm does not absorb
chromium salt stains, whereas the cytoplasm of
chromophils
does
absorb chromium salts. In a Mallory trichrome–stained specimen,
the chromophils can be divided into
acidophils
and
basophils
accord-
ing to the staining (red or blue, respectively) of the granules in the
cytoplasm. Overall cell composition is about 50% chromophobes,
15% basophils, and 35% acidophils. Acidophilic granules are char-
acteristic of cells that secrete polypeptide hormones, such as growth
hormone (
somatotrophs
) or prolactin (
mammotrophs
), and baso-
philic granules are characteristic of cells that secrete glycoprotein
hormones such as TSH (
thyrotrophs
), LH, and FSH
(gonadotrophs)
.
Corticotrophs
, which secrete molecules of the proopiomelanocortin
family, also have basophilic granules. In this photomicrograph, chro-
mophobes have pale cytoplasm, basophils have blue-staining gran-
ules in their cytoplasm, and acidophils have red-staining granules.
Chromophobes
Basophil
Acidophil
Golgi complex
Chromophobe
Chromophil (possible mammotroph)
Chromophil (possible corticotroph)
Chromophil (possible somatotroph)
B
Figure 17-4B.
Cells in the pars distalis, anterior pituitary gland.
EM,
×
7,700; inset (
color
) Mallory trichrome and H&E,
3
423
The ± ve types of hormone-secreting (
chromophil
) cells in the anterior pituitary are most reliably identi± ed by immunocytochemistry
using antibodies against the speci± c hormone or hormones that each cell type secretes. However, an expert can also identify cell types
on the basis of the size, density, and distribution of secretory granules in transmission electron micrographs. This image has an appar-
ent
chromophobe
and at least three different types of
chromophils
. Note the differences in the features of the granules in the three
chromophils that have been labeled. Note also that the nuclei of the chromophils have
nucleoli
and substantial
euchromatin
, features
of cells that are actively synthesizing
polypeptides
. A moderate amount of
rough endoplasmic reticulum
(
RER
)
and prominent
Golgi
complexes
can also be seen in the chromophils. The rich capillary bed in the adenohypophysis consists of capillaries that are fenes-
trated, a feature that allows ready movement of both releasing factors and hormones between the blood plasma and the endocrine
cells. The relative proportions of the speci± c cell types vary signi±
cantly according to speci±
c location within the anterior lobe.
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