collagen and are responsible for the fibrotic changes observed in cirrhosis. The
Kupffer cellsare the antigen-presenting cellsof the liver and are derived
from monocytes. Hepatocytes are arranged in interlocking cords and plates so
there are several ways of analyzing the histological organization of the liver.
Theclassic lobuleemphasizes the endocrinefunction of the liver; the portal
lobuleemphasizes the exocrinefunction of the liver, and the liver acinus
focuses on actual blood supplyand regeneration.
ENDOCRINE GLANDSThepituitary (hypophysis)is formed from two embryonic sources. The
adenohypophysisis derived from the oral ectodermof Rathke’s pouch and
is regulated through a hypophyseal portal systemcarrying factors that
stimulate or inhibit secretion. The anterior pituitarycontainsacidophils,
which produce prolactinandgrowth hormone (GH),andbasophilsthat
produce luteinizing hormone (LH), follicle-stimulating hormone (FSH),
thyroid-stimulating hormone (TSH), adrenocorticotropic hormone
(ACTH),andmelanocyte-stimulating hormone (MSH).Theneurohy-
pophysisis derived from the floor of the diencephalon and consists of
astrocyte-like glial cells (pituicytes)and expanded terminals of nerve fibers
originating in the hypothalamus. The neurohypophysis contains the hor-
monesvasopressinandoxytocin, which are synthesized primarily in the
supraopticandparaventricularnuclei respectively.
Theadrenal glandconsists of two parts. The adrenal cortex,derived
from intermediate mesoderm,and covered by a connective tissue cap-
sule, consists of three zones: the zona glomerulosaproduces aldosterone(a
mineralocorticoid) and is regulated primarily by angiotensin II;thezona
fasciculataandzona reticularisproduce glucocorticoids (e.g., cortisol) and
weak androgens and are regulated primarily by ACTH.The adrenal
medulla,derived from the neural crest,synthesizesepinephrineandnor-
epinephrine(see figure on the following page). Most of the blood that
reaches the adrenal medulla has passed through the adrenal cortex and
contains glucocorticoids that regulate the norepinephrine/epinephrine bal-
ance in the adrenal medulla through regulation of phenylethanolamine-N-
methyl-transferase. The fetal adrenal cortex functions to produce
dehydroepiadrosterone,an androgen that is transported to the placenta
where it serves as a precursor of estrogen.
High-Yield Facts 31