o Source of melanocytestimulating hormone (MSH)
(regulates skin pigmentation)
o In cattle, pigs, and rats, ACTH
produces is cleaved into a-MSH
and corticotropin-like
intermediate lobe peptide or
CLIP
o In dog and horse significant
source of ACTH
o Tumors cab lead to spontaneous
hyperadrenocorticism
THE PITUITARY GLAND
-
Ptuo – spit
Pituita – mucus
Master gland of the body
Controlled by chemical and
electrochemical messengers
Only the adrenal cortex can match
the plethora of hormones produced
by the pituitary gland
MORPHOLOGY
Anatomy
-
-
-
-
Also called hypophysis
o Hypo – under
o Physis – growth
Ventral to the brain in dorsal
concavity of sphenoid bone called
the sella turcica or hypophyseal
fossa
Covered by dura mater
Pituitary stalk or infundibulum rises
dorsally from the pituitary to
connect with the hypothalamus
Subdivided into adenohypophysis
and neurohypophysis
Adenohypophysis
Three parts:
Pars distalis
o Five population of cells
 Thyrotropes
 Gonadotropes
 Lactotropes
 Corticotropes (tropic
hormones)
 somatotropes
- Pars tuberalis
o Upward extension of the
adenohypophysis, attached to
infundibulum
- Pars intermedia
o Forms the junction between the
pars distalis and pars nervosa
Tropic hormones
-
Thyrotropin or TSH
LH
FSH
Prolactin
Adrenocorticotropin
Growth hormone
Somatotropin
Neurohypophysis
2 parts:
-
Infundibulum or pituitary stalk
-
the pars nervors (posterior or
neural lobe)
-
Nonapeptides
-
o Intramolecular disulfide bond

2 cysteine residues

Oxytocin

Arginine vasopressin

Lysine vasopressin

Arginine vasotocin
Blood circulation
-
Receives both arterial and venous
blood
- Internal carotid arteries
o Superior and inferior
hypophyseal arteries
o Venous blood enters the
adenohypophysis from 2
capillary beds
 Median eminence of
hypothalamus
 Lower infundibulum and
neurohypophysis
(READ THE BOOK)
EMBRYOLOGY
-
Adenohypophysis arises from an
evagination of the ectodermal roof
of the oropharynx