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orders or predetermille e the sequence and form o f the oesophageal re sponse is not known . There exists an orderliness o f oesophageal re sponse without the extrinsic nervous system and it might be suggested that the central nervous system cause s a facilitation or inhibition o f thie intri.nsic oesophageal orderline ss .

8o

Separation o f the oe sophageal re sponse from the buccopharyngeal

movement o f swallowing , and the observation that the oesophageal

contraction wave of swallowing may not troverse the whole oe sophagus

(Hwang ,

1 954 ) , indicates that the sequential contraction o f the

oesophagus in swallowing re quires t he pre sence o f a stimulating

" bolus" in the oe sophagus . Creamer and Schlegel

( 1957)

and Siegel

and Hendrix ( 1 961 ) concluded from t he similarit ie s of the oesophage_al

re sponse following buccopharyngaal �ovements o f swallowing and those

evoked by d istension of the oe sophagus that a central me chanism �hich

ordered the form of oesophageal re sponse existed and was stimulated

by e i ther o f t hese stimuli . The presence o f one mechanism for ordering a se quent ial c ontrac tion may preclude the need for duplication ;

however , for adequate func tioning there should surely be a me ans o f adjusting the degree of response according to conditione or require­ meats . The presence of a central aechaai• which aa7 adjust the degree but not the fora of oeeophageal response

in

ewallowtn.s would explain the recor41Ag of sreatl7 different ratee

of

paeaase

of the

contractioa •• .,. without eh Yari.atioa 1a the form of

the

ooatractioa waft .

(Iap1fillpr,

1 958 ,

_haa reportecl the wide raap

of YelocitJ

o f

oeeophapal

coatractioa

obael"ftcl

in

...U.cnrills eYeD 1a the .­

r ·: ' •

" •'"'' \..n. . -·

'

' ._

Fig .

5 . 1 .

_Dee rebrate ca t . S t imulation o f an oe

eoetrsc tion wave _{1D a cranial} direc tion b7

applie tion o t

2

ml

N/10

HCl to the terminal regions

o f the oesophagus. The _cerrtcal oe sophageal contraction

ie aaaociated

�ith,

or attm.lated b7 , a buccopbaryaseal

aoYeMnt

aillil

r to t ob _l'ftd during ewal.lowing .

Recorda from bove do

ward

: u

terior

cerYlcal

oeeop p_a , aaterior thoracic oesopha e ,

10

MO U.��e­ aarker , terainal

oeaoplaagua,

si al , reapiratJ.oa .

81

an d other part of t he alillentary tract affect the degree o f central facilitation o f the o aophageal ae�ueatial response to a distension

and c ould thus lead to changes in the speed of the contraction wave .

This interpretation is c ontrary to the contention that the oesophageal component in swallowing is not dependent on an affe rent discharge o f oesophageal receptora. The use o f preparations with a de-afferentated oe sophagus rdght provide an indication of the validity of t hi s

contention .

For a contraction wave to pass over the oesophagus in a craniad direction , the fac ilita tion of the oesophagus which occurs as a local re sponse ( in ter-oesophageal ) above the point of contrac tion or

distension must be inhibited. I f thi s facilitatory di scharge e ither

ceased or changed to an inhibitory discharge , a disten:;ion or

st imulation by othe r moans of the caudal regions of the oesophagus

could be expected to lead to eithe r a contraction which progre ssed c ranially over the oe sophagus or to an overall inhibition o f the oesophagus. Contraction wnves moving c ranially have been recorded in the decerebrate cat ( fig s .

2.18

and

5. 1 )

and occur in ruminants during regurgitation . In in eructation , there

aa7

be sillp l.y a passive ent o f gas up t he oesophagus, although this point

requires more iDve attcation .

Buccophar'J'Ilgeal. •ov...ata of swallowing have also been ob .. rTe4

followins th �ease of a wan of contraction cranially fi'OII the

teninal to the

cervical

repODa o f the oeaopbasua ( fi. •

5 . 1 ) .

fhi.a "•allow" could

ariM

troll atiaul.ation of the cerrical oeeopbapa 1a

. .

· - - - · ···

Fig . 5 . 2 . Decere brate cat . luid distension o r t he c rvical oe sophagus caused a c on trac t ion o f this region of the oesophagus. This appeared to

stimulat a buc cophQrynge 1 movement similar to

tha t obse ned during swallowing. contrac tion wave o f t he oe sophagus follo ed tb bucco­

pharyngeal Records above

downward : termi.nal oesophagus , sign 1 marking fluid diateasioll of cervical oesophagus , mid­ thoracic oesophagus ,

1 0

MC tiae-aarker ,

cervical oe ai al aarking bucco­

t he course o f the passage o r the contrac tion . Hwang

( 1 954 )

repo

r

ted

t ha t swallowing

cou

ld b stimulated by distension o f the cervical oe sophagus. This type o f re sponse has also bee n obtained in

the

present studies

( a

e fig.

5 . 2 ) .

The reflex modi fication of the basic contrac tile ac tivity o f the

terminal oe sophagus described might indicate the way in which this region will func t ion in c_{ontrolling the passage o f stomach contents}

in to the oesophagus. Rather than presenting a barrier o f resting high tone, as su ggested by many workers , it would pr

o

vide a

r

egion whi c h would be stimulated by refluxing material . The e ase

with which

this region o r t he oe sophagus would be stimulated might depend not

only on the nature of t he tilll te rial but also on the conditi ons existing

else�here in t he aliment�ry trac t . Mate rial passing from thes_e

terminal regions , as far craniad as the anterior thoracic oesophagus ,

would encounte r a similar me c hanism _{stimulated in essentially the same}

manner. Greate r stimulation , or the stimulation of cranial

r

e

gi

on

s

,

would then 1

ad to a more

c

omplete oesophageal cl

e

aring mechanism being brought into

pla7 .

The

oesophagus appears to be c

a

pabl

e

, in

i

ta more caudal

regiona ,

o f

i.Dtriaaic responae

s to

ap

p

li

e

d

et� :

t

h

oee that c an be aodi.tied

b7 conditioas which exist elsewhere

la

the

oe80phape and 1a aore

cU.stant

are

aa. particularl7 of the aliaentar7 tract .

The aodificati.oa

���q be &D

illtriaudc reaction ,

aa iater-oeaopha.p 1

reac tiona , or

•diated

b7

enrilld.c

pathwqa •• re

tl.ex effecta. Refiex

centre•

appear to ezlat

ei

t

he

r

ia

the

IMCI\ll.la

or poatiae repone of

the

central nervous system . Higher regions of the central nervous s,Jstea may also affect the e fficacy o f the re flex modification o f oesophageal ac tivity i f an analogy can be made with the dullary control o f

ALNOR , R . and _{OHN=:�ORGE ,} F . K .

( 1958 ) .

The

influence o f the

vege ta tive

In document Ensayos de Política Económica, Año XII, Vol II, Nº 6, 2018 (número completo) (página 55-59)