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Further observations on the blood supply of the hypophysis cerebri of the rhesus monkey.

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Uepurtment of Anatomy, Harvurd Medical Scliool, Boston, Xassachusrfts
Two previous papers dealt with the blood supply of the
hypophysis of the rhesus monkey, as investigated in thick
serial sections of injected pituitaries (Wislocki and King,
'36 j PJislocki, '36). The present contribution, which concludes these studies, employs instead, a technique of actual
dissection of the hypophysis. By this method it has been
possible to confirm, correct, or amplify certain of tlie observations made with tlie previous technique.
The blood vessels of the head of an adult rhesus monkey
were injected with India ink through the heart. The
calvariurn was removed arid the head fixed in 10% formalin.
:% trichloracetic
The skull was decalcified by placing it in 4
acid. After decalcification, the specimen was washed and
carried over into 70% alcohol. With rongeurs and scissors
the base of the skull was then removed, exposing the liypophysis in situ in the meninges at the base of the brain.
The filial dissectioii of the pituitary, blocked o u t in situ,
was carried o a t in 70% alcohol under a binocular dissecting
microscope, utilizing iris scissors, fine jeweler's forceps and
a cataract knife as instruments. The specimen under the
microscope was illuminated by direct light from a Spencer
The results of the study of the rliesus monkey's pituitary by
the technique outlined above are presented in the form of six
drawings illustrating various phases of the dissection.
Prom examination of these figures many of the essential
characteristics of the topography of the pituitary circul at'ion
can be clearly visualized.
Figure 1 shows the initial step in the dissection of the
hypophysis. The bony sclla and the dura (clu) have been removed showing the base of the gland. I n the wall of the
dural cavernous sinuses (cs) the inferior hypophyseal arteries
(iha) can be seen skirting the posterior border of the neural
lobe, and giving off a nuniber of small branches which,
piercing the dura, penetrate the irifuridibular process.
I n addition to the inferior hypophyseal arteries, veins can
be seen in the dissection. On the surface of the gland and
emanating from its substance small venulcs arc visible. These
are derived both from the anterior lobe and from the neural
lobe. They pass laterally to enter the cavernous sinuses as a
series of minute lateral veins (lhv).
Figure 2 represents a continuation of the dissection, obtaincd by carefully plucking away the infundibular process
and pars intermedia, revealing a deeper set of venules (lhv)
arising from the anterior lobe and tlie irifundibuJum. These
also collect laterally into minute venous stems which enter
the cavernous sinuses. Besides the superficial veins shown in
the previous figure and tlie deeper veins seen here, a few
similar venules were encountered, but destroyed, while removing the neural lobe. These were also directed toward
the lateral border of the gland, excepting two o r three which
emerged independently from the posterior pole of the neural
lobe. These latter venulcs appeared to be derived exclusively
from the neural tissue and pars intermedia.
Further dissection of the hypophysis reveals the region of
the stalk as shown in figure 3. This drawing illustrates the
derivation of the superior hypophyseal arteries (sha) from
the carotid arteries a t their junction with the vessels forming
art, minute branching arteriole passing
f r o m pituitary stalk into hgpothal aiiius
b h ~ branch
of basilar Teiii
hv, basilar veins
c b , ear ernous sinus
ctu, edge of duru reflected froni hy-
emissary vein from hypothalamus
iha, inferior hypoph) scal iirterics
1115, 1atei:rl hypophyseal veins
me, iiiedian eminmce of tuher ciuereum
up, optic chiasma
p b , portal venules
IJ\ 11, para\ ciitricular nucleus
sha, superior hyophyseai :irteries
r, x esscl connecting pituitary stalk
and l ~ ~ p o t l i a l a m u s
Fig. 1 Dissection of the base of the pituitary g1:rnd showing the inferior
hgpophyseal arteiies ( i h e ) skirting the neural lobe and giving off penetrating
branchus. Lateral hvpophysral wnnlcs ( 1 h ) arc seen collecting on t h e surfare
of the gland and passiiig laterallg ab uiiriute rrswls which enter the caver~ious
sinuses (cs).
73, N O . 2
the circle of Willis. Xotrworthy is that the superior hypopliyseal arterics anastornose abundantly to form an arterial
plexus arouiid thc stalk, a iiiniiber of arterioles filially penetrating the substance of the stalk. Clear also is the rich
plexiform layer of capillaries lying in the mantle of pars
tuberalis covering the stalk. Tliis plexus is coextensive wilh
Fig. '7 Further divsection of t h e body of the pituitary gland, obtained h 1 rcIrioval of the neural lobe, showing lateral hypopllpseal vcnules (lhv) clraming
the interior of the h ~ p o p h p s i s .
the pars tuheralis and does not exteiid onto or into the surrouiidirig tuber cinerenm adjoining the attachment of the
stalk to the base of the brain. Inrleed tlie liorder of this
plexus is conspicuously sharp. From the plesus small vessels
( p v ) , apparently venulcs, arise which pass along the surface
of the stalk toward the bod? of the hypophpsis. These vessels
are intcrpwted as being portal vciiules, arising from a plexus
in the pars tubcralis and appearing t o low themselves in the
sinusoidal capillaries of the anterior lobe o r in the dreper
cupil la r y p lexu s sur r ouriclirig the i nf undihula r y r oce 8::.
Fig. 3 Dissection f tlic hypophgseal stalk showing supcrior hypophysenl
arteries (slrx) deiivcd from tlic carotid arterics, anastoniosing aiict srnding twigs
t o the h ~ p o l ~ h ~ s stalk.
On t h e surface of tlic stalk lodgcd in the mantle of
pars tuhertilis a, rich iietnork o f ~ e s s e l s can t)r secii ill n h i c h crrinll portal
r(nules ( p v ) are rccognizablc.
Figure 4 i-cpreseiits a solliewhat further. claboration of
the dissection showing the complete set of super.ior hypophyseal arteries (shv) and their numerous anastomoses. The
truiilcs of the carotid arterics and of the circle of Willis haye
been in the main cut away. The termiiial twigs of the arborizing hypophyseal arttliaies penetrate the siallr of the glanld, or
the neck betwecn the stalk and the body of the gland. The
body of the hypophysis has actually been cut away in the
dissection, excepting a stump of 1)ars anterior surrounding
the oval infundibnlum. On tlie cut suri'acc of the pars anterior numerous minute vessels are seen, tlie larger consisting
of tiny arterioles or rennles, the smaller represelltirig
Pig. 4 The hypirph)-seal s h l k disxrcted sn as t,o s h o w a11 of tlie supcrjor
hypopliyscal arteries ( sh x ) fornriiig anastomoses a n d giving off IiI1mPI'ous twigs
t o the stalk from all sidcs.
sinusoids. Bctwem tlie anterior lohe a n d the oval outliiie
of the infuiidihulum the cut links of a delicate plexus of
capillaries a r e visiblc. The interior of the iiifuiidibnlurn is
relatively a\Tascular in this zoiie 1)etwccn stalk and infnndihular 1)rocess. At irregular intervals short delicate tufts of
capillaries j m c t r a t e the infuntlibnlum as indicated in figures
4 a i d 5. These tufts coniicct >i-itli tlie plexus of capillaries
surrounding the iiifundihulnm ; they pierce the inf uridibiilum
anteriorly arid are frcquciitly bilaterally situated as at the
two levels shown in figures 4 and 5.
Figure 5 is a co~npanioripiece to the prececling (1ir;sectioii.
It is similar to figure 4,excepting that the arteries Iiavcl heen
almost completely rcmoved, rwealing the dirtribation, course,
Fig. 5 A further tlissectioii of s t d k ohtairicvl by rernoring thc superior
Ii;ypopli>-swI arteries. Beneath t h e arterics i s now rcvcnled the s~ stem of haailsr
wins (bv) arising f r o m vcnules emerging f r o m t,he h s u of the braiii, h u t rceeiving no tributary vcnules or capillaries from th e surface of the hppop1iysiu.
A tributary vrnule ( ~ J ~ J vi )s a h o n n emerging froin t h e h ~ p o t h a l n m u s ;t h e origin
of t,his venulr can be seeu in thc ricxt fipurc.
and character of the basilar veins (bv) on the surface of the
lippothalamus. 111 the preceding figure the basilar veins
(fig. 4, bv) c a n be seen only faintly uiiclerneatIi the artericls
at a deeper level. Soteworthy regarding thcse veins is that
they do not arise from the h ~ p o p h y s e a lstalk. They a r e
formed b y veins emerging from the substance of the brain
aild rcachiiig the surface some distance from the stalk. These
emissary veiiules bend at right angles 011 reaching the surface
of the tubcr cinereurn and proceed, by uniting, t o form the
basilar veins. These circumstances account for the blunt,
sudden way in whicli the basilar veins malie their appearance,
well removed f r o m the hy yophysis. Chnsequently there appears to be little, if any, possihle venous drainage from the
pituitary directly into the nearby basilar veins on the surface
of the Iiypothalamus. The iiidcpeiidcnce of tlie pituitary complcx, as far a s surface connections wit11 these reins are coilcerned, is cleui=lyseen i n the figure.
The final dissection of the pituitary is slionn i n figure 6.
The dissection is derived from tlie specimen p o r t r a y d in
figure 5 by splitting it open in thc mid-sagittal plane. Each
of the resulting halves of the hypophysis reveals the interior
of the third ventricle and the adjacent wall of tlip hypothalamus arid pituitary stalk. The wall of tlie ventricle has
been pai*tially ilisscctcvl away by removal of its most snpcrficial substance. This brings the hloocl vessels in tlie subjacent tissue and their relationship to the 1)lood vessels in the
pituitary stalk m o i prominently
into view. By delicate dissection the junction of the pituitary stalk and the tuhcr
cinercum was suhseqneiitly completely dissected, iii both
halves, so that a survey could be made of all of the vascular
connections existing hetiwen t l ~ epituitary and the hypothalamus.
Figure G reveals a number of interesting features regarcliiig
the vascular relationsliips of the pituitary and hypothalamus.
First of all the characteristic plexiform tufts of siausoidal
capillaries call be seen penetrating the substance o€ the jnfundiliular stalk and the niedian eminence ( i i ~ ) of thc tubcr
Fig. 6 The dissrc,ted hppuphyseal stalk and h~-pot.halai~ius
split in the iuidsagittal plane, revealing the vascuhr plcsuses within the 111-popliyseal stalk.
The transitional vessels lietween t h e median eininenw (nip) of the Iiypophyseal
stalk arid the hypothalamus arc shown. T h e largest, of these (1:) is B vessel
of undeterrniiied character. d Iiiinut,e arteriole ( a r t ) traversing t h e boundary
of the st,alk and hypothalamus is also visible. Ba hypothalamic rein ( e v ) is seen;
i t passes t o the surfape and drains int,o a branrh (i)lw) of one of the lrasilar
veins. This branch is the same vessel seen from the surfact? in figure 5 ( h h v ) .
It is clear from study of thc blood vessels in the transition zone hrtwwn hppophyseal stalk and brain proper, shown in this figure, that there are no significant
vascular links bctweeri t,he pituitary and the more important nuclear centers of
the hypothalamus, f o r example, t h e paraventricular nucleus ( p n ) .
cinereurn from the mantle of blood vessels and capillaries
located in the pars tuberalis which encloses the hypophyseal
stalk. The larger of tliese tufts a r c supplied with afferent
arterioles. Secondly, i t can be seen that at the border of
the rriecliaii eminence many of the siniisoidztl tufts connect by
mini1t e ve s sel s mi t 11 char a c:t e ri stic sl end cia capillaries of the
brain. These anastomoses, although fairly nuincrons, appear in the main to bc of the calibcr of capillaries, only a very
€ew of them appearing t o be of tlie magnitude of small
arterioles or vcnulcs. The second largest of all such coiiricctioiis hetmeen the pituitary stalk aiicl the hypotlialamus, discovered in the present spccimcii, is shown in figure 6 ( a r t ) .
It is seen to be EL delicate bi.aiiclliug vessel which emerges
from the limits of the stalk ancl passes for a short distance
into ilie liypothalarnus hefore it breaks up into capillaries.
It is regarded a s being an arteriole for two reasons. It
appears t o arise from thc central arteriole of a vascular tuft
in the hypopliyseal stalk arid it breaks up into capillaries
which can he traced quite definitely t o the nearby li>-pothalaiiiic: veiiules ( e r ) shown in the figurc. Only o m vessel
of any considerahle size and extent was discoverahle upon
complete dissection of thc entire zone of traiisi tion hetween
the pituitary stalk and the hypothalamus proper. This
vessel, \\liicli arises near the anterior border of the hypopliyseal stalk, is slio~viiin tlie figiire (v). It emerges from
a typical plexiis in the median eiiiinencc of tlie tiilner cinereurn
and follows a course skirting the optic chiasma. Whethei. it
is to be regartlecl a s a r t w i a l or renous in character rcmains
uriclctcrmincd f o r the iiature of its origin is ohscurecl by the
complexity of the tuft from ~ h i c hit arises, arid its ultimate
dcstinatioii caiinot be accurate17 traced. T t is the oiily cxtcnsive connection between the stalk region iilld the hypothalamus
encountered i n the Course of the snrvey of all possible transitional vessels. Consequently it must be coilsidered as being
of exceptional occurrence.
Another noteworthy feature of the dissection shown in
figure 6 is thc demonstratioii of the complete course of an
emissary vein (cv) in the wall 01 the third ventricle. This
veiri can be traced from the interior of the brain through the
wall of the tuber cinereum, adjacent to the median eminence,
to its connection with a branch of one of the basilar (bbv)
veins on the brain surface. This same branch can be identified in the previous dissection (fig. 5, bbv). Thus we are
able to trace a branch of oiie of the basilar veins from its
entire source in the substance of the hypotlialamus. Of
interest regarding this typical vein is that, although it skirts
the pituitary, it receives no vessels of the caliber of venules
from the hy-pophyseal territory. Its connections with the
pituitary, insofar as they exist, appear t o be of capillary
size only.
Regarding the possibility of sizable vascular connections
between the hypophyseal stalk and the hypothalamusespecially the existence of vessels of the nature of portal
veins-the present dissection of the monkey affords no convincing evidence. The anastomoses between the vessels of
the two regions appear to be relatively small and quite local
in character, certainly not involving any important vascular
linkage between the pituitary stalk and such distantly situated hypothalamic structures as the paraventricular and
supraoptic nuclei. I n figure 6 part of the paraventricular
nucleus (pvn) can be seen in the upper right hand corner of
the field, identifiable by its pronounced capillarity. The unlikelihood of this nuclear mass receiving vessels of any size directly from the region of the pituitary stalk is apparent at a
glance. And indeed this impression has been checked by
careful and complete dissection of the intervening territory
with the failure to locate any possible significant vascular
connections whatsoever. The same negative results were obtained upon searching for possible portal venules or other
direct vascular coriricciions between the pituitary stalk and the
supraoptic nuclei which lie some distance laterally to the
median eminence and are not shown in the figure.
72, X O . 2
The results of dissection of the pituitary complex by the
technique adopted confirm in the main the conclusions reached
in the previous studies of the pituitary of the rhesus monkey
based on examination of cleared, thick, serial sections.
Little doubt remains concerning the nature and distribution
of the arteries which reach the pituitary as two groups: one
the inferior hypophyseal arteries ; and two, the superior
hypophyseal arteries. The former are distributed in the infundibular process ; the latter enter the hypophyseal stalk,
from which branches pass to the anterior lobe.
Further evidence is gained regarding the existence of
venules passing between the hypophyseal stalk and the body
of the gland. Conriected at either end with capillaries, these
are probably correctly interpreted as constituting a system
of portal vessels.
Regarding the systemic veins, draining the hypophyseal
complex, the present study reveals a series of small venules
emanating from the body of the gland which enter the
cavernous sinuses. These arise more especially, but nevertheless not exclusively, from the neural lobe. The stalk region
appeam to possess no venous connections of importance, excepting the system of portal venules connecting the stalk with
the body of the gland. Direct systemic veins appear to be
totally lacking. First, there is no evidence of capillaries or
venules draining from the surface of the stalk into the nearby
basilar veins. Secondly, direct systemic venous coniiections
with the veins of the hypothalamus proper do not appear
to exist. With the exception of one larger vessel of undetermined nature, encountered in the present specimen, and a
few minute channels which are probably arterial, the vascular
connections between the stalk and the hypothalamus arc of
capilliform size. It is apparent, moreover, that the relatively
minute anastomoses between the vessels of the brain and
those of the hypophyseal stalk are restricted to quite local
territory, involving only the immediate border zone hetween
stalk and brain. No significant vascular pathways exist between the pituitary and such structures, lying at a distance,
as the paraventricular and snpraoptic nuclei. These possess
quite independent vascular supplies.
Thus it follows that in the rhesus monkey the main efferent
vascular channels are those extending from the body of the
gland to empty into the cavernous sinuses. Drainage by
capillaries o r venules connecting the stalk and the brain, if
it occurs at all, must be quite subsidiary. Eflerents represented by either venules or capillaries leading directly from
the surface of the stalk into the adjacent basilar veins on1 the
brain surface are completely lacking. The monkey differs
in this respect from the cat in which it has recently been
shown (Wislocki, '37) that a certain number of capillaries
pass from the circumference of the hypophyseal stalk to the
surface o i the hypothalamus to become small venules tributary to the basilar veins. I n spite of these efferents, the
venules leading from the body of the gland into the cavernous
sinuses are regarded in the cat also as being the most sizable
and important pathways for venous drainage.
An account is given of the dissection, under a binocular
microscope, of a pituitary gland of a rhesus monkey in which
the blood vessels have been completely injected with India
ink. Superior and inferior hypophyseal arteries are traced
into the gland. Small venules of portal character are observed on the pituitary stall;, connecting the stalk with the
body of the gland. Systemic venules are described passing
from the body of the gland into the cavernous sinuses. Systemic venules running from the hypophyseal stalk to the
nearby basilar veins on the surface of the tuber cinereum are
lacking. Connections greater than capillary caliber between
the stalk and the hypothalamus are relatively few in nnmber
and slight in extent. The largest such connections, whether
they be interpreted as venules or arterioles, are too restricted
in caliber, extent, o r number t o be regarded as playing any
significant role in conveying blood from the pituitary complex to the hypothalamic centers.
WIsLorxI, G. B. 1936 The vascular supply o f the hypop1i~sis cerebri of the
rhesus monkey and man. Proc. Assn. f o r &search in Nervous and
Mcntal Disease, vol. 17, pp. 48-68.
- 1937 The vascular supply of the hypopohysis cerebri of the eat.
Anat. Rrc., vol. 69, pp. 361-387.
WISLOCKI,G. B., AND L. S. KINQ 1936 The permeability of the hypophysis
and hypothalamus to vital dyes, with a study of the hypophyseal
vascular supply. Am. J. Anat., vol. 58, pp. 4 2 1 4 7 2 .
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hypophysial, cerebro, monkey, rhesus, observations, supply, blood
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