I. Pituitary Gland c.

Pars Intermedia
a. Lies below the brain in a small cavity on i. Narrow zone lying between the
the sphenoid bone, the sella turcica. pars distalis and the pars
II. Adenohypophysis (Anterior Pituitary) nervosa.
a. Pars Distalis ii. Contains basophils
i. 75% of adenohypophysis (corticotrophs), Chromophobes,
ii. Has a thin fibrous capsule and small colloid-filled cysts.
iii. Cords of well stained endocrine iii. POMC produce melanocyte-
cells interspersed with stimulating hormone (MSH), y-
fenestrated capillaries. LPH, and B-endorphin.
iv. Has a supporting reticular tissue III. Neurohypophysis (Posterior Pituitary)
v. Acidophils a. Consists of Pars Nervosa & Infundibular
1. Somatotrophs = Growth Stalk
Hormone b. Does not contain the cells that
2. Lactotrophs = Prolactin synthesize its two hormones.
vi. Basophils c. Pituicytes
1. Corticotrophs = i. Highly branched glial cells that
Adrenocorticotropic resemble astrocytes and are the
Hormone most abundant cell type.
2. Gonadotrophs = Follicle d. Neurosecretory bodies
Stimulating Hormone & i. Axonal Dilations
Luteinizing Hormone ii. Also called Herring bodies
3. Thyrotrophs = Thyroid iii. Visible in the light microscope
Stimulating Hormone as faintly eosinophilic
vii. Chromophobes structures.
1. Stain weakly, with few iv. Contain Antidiuretic Hormone
or no secretory (ADH) and Oxytocin.
granules. IV. Adrenal Glands
b. Pars Tuberalis a. Also called Suprarenal Glands
i. Smaller funnel-shaped region b. Paired organs lying near the superior
surrounding the infundibulum poles of the kidneys, emedded in the
of the neurohypophysis. pararenal adipose tissue and fascia.
ii. Most of the cells here are c. Flattened structures with a half-moon
gonadotrophs. shape.
 d. Covered by a dense connective tissue d. Zona Reticularis
capsule that sends thin trabeculae in i. 10% of the cortex
the gland’s parenchyma. ii. Consists of smaller cells in a
e. Two concentric regions: a yellowish network of irregular cords
adrenal cortex and a reddish-brown interspersed with wide
central adrenal medulla. capillaries.
V. Adrenal Cortex iii. Cells are usually more heavily
a. Cells of the adrenal cortex have stained than those of the other
characteristic features of steroid- zones because they contain
secreting cells: acidophilic cytoplasm fewer lipid droplets and more
rich in lipid droplets, with central nuclei. lipofuscin pigment.
b. Zona Glomerulosa iv. Also produce cortisol but
i. 15% of the cortex primarily secrete the weak
ii. Consists of closely packed, androgens, including
rounded, or arched cords of dehydroepiandrosterone
columnar or pyramidal cells (DHEA) that is converted to
with many capillaries. testosterone in both men and
iii. Secrete Mineralocorticoids women.
1. Principal product is VI. Adrenal Medulla
aldosterone. a. Composed of large, pale-staining
c. Zona Fasciculata polyhedral cells arranged in cords or
i. 65%-80% of the cortex clumps and supported by a reticular
ii. Consists of long cords or large fiber network.
polyhedral cells, one or two b. Chromaffin Cells
cells thick, separated by i. Medullary Parenchymal Cells
fenestrated sinusoidal ii. Arise from neural crest cells, as
capillaries. do the postganglionic neurons
iii. Cells are filled with lipid of sympathetic and
droplets and appear vacuolated parasympathetic ganglia.
in routine histologic iii. Can be considered Modified
preparations. sympathetic postganglionic
iv. Secrete glucocorticoids, neurons, lacking axons and
especially cortisol. dendrites and specialized as
secretory cells.
iv. Contain many electon dense
granules.
 v. Storage and secretion of
catecholamines, either
IX. Thyroid Gland
epinephrine or norepinephrine.
a. Located anterior and inferior to the
vi. Chromogranins
larynx, consists of two lobes united by
1. Granular storage
an isthmus.
complexes with 49-kDa
b. Composed of millions of rounded
proteins
epithelial thyroid follicles of variable
VII. Pancreatic Islets (Islets of Langerhans)
diameter, each with simple epithelium
a. Compact spherical or ovoid masses of
and a central lumen densely filled with
endocrine cells embedded within the
gelatinous acidophilic colloid.
acinar exocrine tissue of the pancreas.
c. Thyroglobulin
b. α or A cells
i. Large glycoprotein that is in a
i. Secrete primarily glucagon.
thyroid colloid.
ii. Abundant and scattered
d. Follicular Cells (Thyrocytes)
through most islets.
i. Range in shape from squamous
c. β or B cells
to low columnar.
i. Produce Insulin
ii. Their size and other features
ii. Twice as abundant as α cells
vary with their activity.
and also usually scattered.
iii. Have apical junctional
d. δ or D cells
complexes and rest on a basal
i. Secrete Somatostatin
lamina.
ii. Much less abundant than the
iv. Synthesize the thyroid
other major cell types
hormones thyroxine and tri-
e. PP cells
iodothyronine (T3)
i. Secrete Pancreatic Polypeptide
e. Parafollicular Cell (C cell)
VIII. Diffuse Neuroendocrine System
i. Found inside the basal lamina
a. Enterochromaffin cells
of the follicular epithelium or as
i. Scattered in both the islets and
isolated clusters between
small ducts of the pancreas.
follicles.
ii. Stained by solutions of
ii. Larger than follicular cells and
chromium salts.
stain intensely.
b. Argentaffin Cells
iii. Secrete Calcitonin
i. Staining with silver nitrate
c. APUD cells
i. Secrete Serotonin
X. Parathyroid Gland
a. Four small ovoid masses.
b. Located on the back of the thyroid
gland.
c. Principal (Chief) Cells
i. Small polygonal cells with
round nuclei and pale-staining,
slightly acidophilic cytoplasm.
ii. Secrete Parathyroid Hormone
(PTH)
d. Oxyphil Cells
i. Much larger than the principal
cells and are characterized by
very acidophilic cytoplasm filled
with abnormally shaped
mitochondria.
XI. Pineal Gland
a. Also known as epiphysis cerebri
b. Small pine-cone shaped organ.
c. Pinealocytes
i. Have slightly basophilic
cytoplasm and irregular
euchromatic nuclei.
ii. Produce melatonin
d. Modified Astrocytes
i. Interstitial glial cells that are
staining positively for glial
fibrillary acidic protein, which
represent about 5% of the cells.
e. Corpora Arenacea (Brain Sand)
i. Formed by mineralization of
extracellular protein deposits.
ii. Concretions of calcium and
magnesium salts.