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Staging of intestinal development in the chick embryo.

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THE ANATOMICAL RECORD PART A 288A:909 –920 (2006)
Staging of Intestinal Development in
the Chick Embryo
BRIDGET R. SOUTHWELL1–3*
Gut Motility Laboratory, Murdoch Children’s Research Institute, Victoria, Australia
2
Department of Surgical Research, Royal Children’s Hospital, Melbourne, Australia
3
Department of Paediatrics, University of Melbourne, Melbourne, Australia
1
ABSTRACT
Comparisons between developmental studies rely on embryonic staging
systems. It is important for comparison of molecular, immunohistochemical, and physiological studies of the developing chick intestine that the
developmental stage of embryos is reliably determined. Good staging systems exist for the external features of the chick embryo but not for development of internal organs. To facilitate precise comparisons of chick embryo
intestine development, we prepared an intestinal staging system. Embryos
were fixed, other tissues dissected away, and the intestine and associated
organs were then drawn to scale using a camera lucida. This produced
black-and-white drawings with features of the gut clearly visible. The
detailed drawings of intestine from chick embryos aged 2.5 to 10 days were
correlated with age of embryos and developmental stages described in three
common staging systems, Hamilton and Hamburger, Thompson and
Fitzharris, and Allan and Newgreen. Descriptions of key changes in gut
morphology and position are given for each stage. This staging of chick gut
development will allow future studies to quote and compare development of
the gut rather than external features or incubation time. This will allow
much more precise reporting and comparisons in developmental studies of
cell migration and gene expression. Anat Rec Part A, 288A:909 –920, 2006.
©
2006 Wiley-Liss, Inc.
Key words: intestinal development; fowl; growth
There is considerable individual morphological variation when a daily chronology is used to stage embryonic
development. Hamburger and Hamilton’s almost universally used staging system for the fowl embryo (Hamburger
and Hamilton, 1951; Hamilton, 1952) describes external
features characteristic at periods of embryonic development. The development of internal organs at particular
stages of development has not been so well described.
Detailed descriptive accounts covering the embryonic
period have been reported for the changing morphology of
each region of the alimentary canal (Romanoff, 1960). The
primary concern of these accounts was identification of the
day when characteristic morphological features appear or
change. These accounts do not allow easy consideration of
morphological events occurring in a number of regions at
the same time and do not allow for individual variations in
time of development.
Romanoff (1960) provided a summary table of previously reported data on development and length of regions
of the intestine. During studies on the development of the
enteric nervous system, we needed a series providing sim©
2006 WILEY-LISS, INC.
ple descriptions of the key features of morphological development of the intestine to provide a basis for comparison of studies and allow the timing of cellular events to be
related to morphological development (Newgreen et al.,
1996). Having created this description, others have found
it useful and requested we publish (McBride et al., 2003).
This article provides descriptions and outline drawings
of the intestine and cloaca for each Hamburger and Hamilton (1951) stage from 16 to 36 (fowl embryos 2–10 days).
Also included is the morphological development of Remak’s nerve. Development of embryos is related to the two
*Correspondence to: Bridget R. Southwell, Gut motility Laboratory, Murdoch Children’s Research Institute, Parkville, Victoria, 3052, Australia. Fax: 61-3-9345-6240.
E-mail: bridget.southwell@mcri.edu.au
Received 16 December 2005; Accepted 3 February 2006
DOI 10.1002/ar.a.20349
Published online 11 July 2006 in Wiley InterScience
(www.interscience.wiley.com).
910
SOUTHWELL
commonly used descriptions of external features (Hamburger and Hamilton, 1951; Hamilton, 1952) and two
studies on development that quote developmental age and
temperatures of incubation (Thompson and Fitzharris,
1979; Allan and Newgreen, 1980).
MATERIALS AND METHODS
Black Australorp and White Leghorn/Black Australorp
cross-breed of domestic fowl embryo were used. Both fertile and partially incubated eggs were obtained from a
local research hatchery and maintained in a forced
draught incubator (Multiplo, Sydney, Australia) at 38 ⫾
1°C. Differences were not observed in rates of development between the two breeds, or for eggs received in a
fertile or partially incubated state. Prior to incubation,
unincubated eggs were stored at 10 –15°C. To compare to
Hamburger and Hamilton (1951) staging, some eggs were
incubated at 39.4°C.
Embryos were staged by external features according to
Hamburger and Hamilton (1951) and the precise duration
of incubation was recorded. At least two embryos at each
stage were examined using an Olympus dissecting microscope with continuous zoom magnification. Morphological
features of the gut and closely associated tissues were
traced using a camera lucida drawing tube. To limit shape
changes during dissection and orientation for illustration,
following careful removal from the egg, embryos were
placed in 10% formalin/PBS at room temperature. The gut
was drawn from both left and right aspects to illustrate
features of development at each stage. Where lack of bilateral symmetry was significant, a ventral aspect was
also drawn.
For stages 16 –24, the ventral and lateral body walls
were removed and the gut is shown in position relative to
other viscera and the dorsal body. In subsequent stages,
the body dorsal to the viscera was also removed. To reduce
lettering on other diagrams, features are labeled in Figure
1 only. The most common incubation times at which the
identified stages were found are included with the descriptions of intestinal development at each stage and compared with the incubation times reported by Hamburger
and Hamilton (1951), Hamilton (1952), Thompson and
Fitzharris (1979), and Allan and Newgreen (1980).
RESULTS
Diagnostic Features Used for Staging
The widely used Hamburger and Hamilton (1951) staging for the fowl embryo identifies changes in external
structural features (e.g., somites, limbs, visceral arches)
or their positions (e.g., flexures and rotation). A similar
initial diagnostic categorization is employed here, with
the displacement of the gut with respect to the embryonic
axis being diagnostically useful at all stages. The structural features, which include intestinal regions and other
closely associated structures, are of diagnostic significance
for shorter times.
The dorsal mesentery is diagnostic early (stages 17–25)
and replaced later by Remak’s nerve (stages 25–36). Three
structural features, the umbilicus (stages 16 –25), the cloacal area (stages 26 –35), and bursa of Fabricius (stages
33–36), are diagnostic for periods. Other structures appear over one or more stages and are used as descriptive
characteristics (e.g., the angle of the omphalomesenteric
artery passing toward the umbilicus or the phallus extending as a cap to the vent in the cloaca area).
Fig. 1. Key to structures in all diagrams. A, allantois; Ca, caecum;
CR, colorectum; D, duodenum; G, gizzard; H, heart; K, kidney; L, liver;
Lu, lung bud; M, dorsal mesentery; OA, omphalomesenteric artery; Oe,
esophagus; OV, omphalomesenteric vein; P, pancreatic bud; Ph, phallus; Po, postumbilical small intestine; PoI, postumbilical intestine; Pr,
preumbilical small intestine; PrI, preumbilical intestine; RN, Remak’s
nerve; S, somite; St, stomach. Scale bar ⫽ 1 mm (each division). Stage
aspects ⫽ L, left; R, right; V, ventral. Chronologies included in stage
descriptions: H&H, Hamburger and Hamilton (1951); H, Hamilton (1952);
T&F, Thompson and Fitzharris (1979); A&N, Allan and Newgreen (1980).
The gut is staged differently with respect to the pre- and
postumbilical regions. This arose from the clear separation by the open umbilical region of the caudal and cranial
tubular primordia. At stage 16, the postumbilical gut
gives rise to all regions of the cloaca, the large intestine,
and the caudal part of the small intestine. As each constituent regional segment becomes an independently identifiable diagnostic feature, it is described under the appropriate broad gut region. In the preumbilical intestine,
most of its early development was staged by flexing and
displacement of the gut tube, rather than according to
distinct regional features. From stage 25, the whole intestine can be treated under its definitive regional segments
(duodenum, preumbilical and postumbilical small intestine, caeca, colorectum). Then displacement of the gut as a
INTESTINE DEVELOPMENT IN CHICK EMBRYO
911
whole is described, with flexures and displacements of a
particular definitive region used to characterize that region.
Terminology
As the primary concern of this report is a stage-by-stage
characterization of the external morphology of the intestine, simple descriptive terms were used. “Preumbilical
gut” refers to all tubular regions (both ectoderm-associated and endoderm-associated) lying cranial to the umbilical area, and “postumbilical gut” refers to all tubular
regions caudal to this. When definitive regional primordia
became clearly identifiable, terminology appropriate for
the mid- to late-term embryo is used.
There is disagreement on the appropriate regional terminology for the intestine of the bird (Hodges, 1974;
McLelland, 1975; Allan and Newgreen, 1980). The mammalian distinction between jejunum and ileum is difficult
to identify in the avian adult and indistinguishable in the
avian embryo, thus the clearly identifiable regions of the
small intestine were referred to as duodenum, preumbilical small intestine, and postumbilical small intestine. The
large intestine has two identifiable regions, the caeca and
a combined colorectum (McLeod, 1939). The colorectum
passes directly into the coprodeal compartment of the
cloaca (King, 1975), the boundary being marked by an
abrupt increase in the diameter of the most caudal gut. In
the embryo, this boundary only becomes clearly identifiable at the cranial extent of the bursa of Fabricius, which
is not observable until stages 33–36. The three compartments of the cloaca (coprodeum, urodeum, proctodeum)
were identified according to conventional practice (Romanoff, 1960; King, 1975). The external opening from the
cloaca is often identified in the avian literature as the
anus (Hamilton, 1952; Romanoff, 1960). As the term
“anus” has a well-established but different meaning in the
mammalian literature (Romer and Parsons, 1977), the
external opening from the cloaca is referred to as the
“vent” (King, 1975). The term “cloaca” was applied to
structures in the immediate vicinity of the vent or its
primordia (e.g., cloacal area, cloacal papillae).
Description of Gut at Different Stages
1
d;
2
Stage 16 [2
Hamburger and Hamilton
(H&H), 51–56 hr; Hamilton (H), 51–56 hr; Thomp3
son and Fitzharris (T&F), 2 4 d; Fig. 2].
Displacement: the gut lies in the midline.
Umbilicus: unformed. The gut is open from the anterior
intestinal portal, immediately caudal to the sinus venosus, to the tail bud.
Postumbilical gut: a wide open pocket in the tail bud.
Stage 17 (2 43 d; H&H, 52– 64 hr; H, 52– 64 hr; T&F,
3 d; Fig. 2).
Displacement: the preumbilical gut has moved very
slightly to the left of the midline, while the postumbilical
gut remains in the midline.
Umbilicus: closure beginning. The gut is open from just
behind the emerging liver buds to the tail bud. The anterior intestinal portal and posterior intestinal portal are
present at each extremity of the open gut. Over subsequent stages, they maintain this location drawing together in the mid-umbilical intestine.
Fig. 2.
Intestine and embryo outline from stage 16 –18.
Postumbilical gut: a short tube extending caudally into
the now ventrally bending tail bud. A swelling on the
ventral side of this short tube in older embryos from this
stage demarcates the first appearance of the allantoic bud.
Dorsal mesentery: it is observable only cranially, extended to just caudal from the liver bud.
Stage 18 (3 d; H&H, 65– 69 hr; H, 3 d; T&F, 3 41 d;
Fig. 2).
Displacement: little change.
Umbilicus: further closure. Extends from two somites’
length caudal to the pancreatic bud to the short postumbilical gut.
Postumbilical gut: a funnel-shaped tube up to four
somites’ length cranial to the prominent thick walled sac
of the allantois. As in the previous and subsequent stages,
this tube extends into the ventral curvature of the tail.
Dorsal mesentery: observable more caudally, approaching the level of the omphalomesenteric artery, which
passes at right angles from the dorsal aorta to the yolk sac
at the midpoint of the open gut.
912
SOUTHWELL
Fig. 3.
Intestine and embryo outline from stage 19 –20.
Stage 19 (3
3 d; Fig. 3).
1
2
1
4
d; H&H, 68 –72 hr; H, 3–3
1
2
d; T&F,
Displacement: the swollen stomach is now lying left of
the midline. It constricts caudally and bends back to the
midline where the intestine becomes a narrow tube passing slightly ventral, arriving at the open gut after two or
three somite lengths.
Umbilicus: the closed preumbilical intestine and
postumbilical gut together are about equal in length to the
open intestine. A ratio of open:closed intestine of about
1:1.
Postumbilical gut: continued closure cranially while retaining funnel shape. Extends up to six somites’ width
from the allantois, which is now a small vesicular sac.
Dorsal mesentery: observable caudal to the omphalomesenteric artery but is not apparent yet at the caudal
extent of the open gut.
Stage 20 (3
3 d; Fig. 3).
3
4
1
3
d; H&H, 70 –72 hr; H, 3–3
1
2
d; T&F,
Displacement: the intestine curves dorsally immediately after leaving the constricted caudal stomach. It then
curves ventrally past the hepaticopancreatic ducts and
Fig. 4.
Intestine and embryo outline from stage 21–22.
curves right returning to the midline. Caudal to this, the
gut remains in the midline. The narrow tube for the cranial intestine extends up to four somites’ length beyond
the hepaticopancreatic ducts.
Umbilicus: the closed preumbilical intestine and postumbilical gut are each about equal in length to the open
gut. A ratio of open:closed intestine approaching 1:2.
Postumbilical gut: continues to close as a funnel-shaped
tube. Now extends up to eight somites’ width from the
allantois.
Dorsal mesentery: now observable into the region of the
closed postumbilical gut.
Stage 21 (3
Fig. 4).
1
2
d; H&H, 3
1
2
d; H, 3
1
2
d; T&F, 4 d;
Displacement: further development of the flexures begun at stage 20. The closed tube of the intestine now
INTESTINE DEVELOPMENT IN CHICK EMBRYO
913
extends up to five somites’ length from the beginning of
the hepaticopancreatic ducts.
Umbilicus: little change.
Postumbilical gut: the allantois is attached to the cloaca
by a stalk somewhat thicker than the gut. Immediately
cranial to the allantoic stalk, the gut narrows for one to
two somites’ length, indicating the primordia of the colorectum. Cranial to this, the postumbilical gut widens for a
short distance, demarcating the point from which the caecal buds will originate. The caudal postumbilical small
intestine is apparent as a result of a slight narrowing of
the postumbilical gut cranial to the caecal primordia.
Dorsal mesentery: observable to the level of the caecal
primordia.
3
1
1
1
Stage 22 (3 4 d; H&H, 3 2 d; H, 3 2– 4 d; T&F, 4 2 d;
Fig. 4).
Displacement: caudal to the stomach, the intestine
passes from the left to just right of the midline before
returning to the midline. Caudal to this, the gut remains
in the midline. The first indication is present of the ventral curvature in the umbilical intestine, where the
omphalomesenteric artery passes to the open umbilicus.
Umbilicus: closed to within one or two somites’ length
on either side of the omphalomesenteric artery, which
passes cranial to the midpoint of the open umbilicus after
leaving the aorta at an obtuse angle.
Postumbilical gut: further development of stage 21, particularly an increased lengthening of the postumbilical
small intestine.
Dorsal mesentery: observable beyond the caecal swelling as a narrow strip attached to the dorsal colorectum.
Stage 23 (4 d; H&H, 3 21– 4 d; H, 4 d; T&F, 4
Fig. 5).
1
2
d;
Displacement: further development of stage 22 with the
preumbilical small intestine returning to the midline at
the cranial edge of the open gut. The postumbilical gut
remains in the midline. A ventral U-shaped curve in the
small intestine opposite the omphalomesenteric artery is
now clearly apparent. Viewed from the left side, the umbilical vein passes along the cranial boarders of this ventral curvature. The region of contact between the two
identifies the primordia of the preumbilical small intestine from the duodenum.
Umbilicus: the gut remains open in the ventral part of
the U-shaped curve in the intestine.
Large intestine: a short and narrow colorectal region is
now clearly apparent cranial to the allantois. Viewed ventrally, the bulges of the caecal buds can be seen. While
thinner than the region of the caecal pouches, the postumbilical small intestine remains thicker than the colorectum.
Dorsal mesentery: observable to the caudal end of the
colorectum, where it is a narrow sheet attached to the
dorsal wall.
Stage 24 [4 21 d; H&H, 4 d; H, 4 21 d; T&F, 4 5/8 d;
Allan and Newgreen (A&N), 4 1/8 d; Fig. 5].
Displacement: caudal to the stomach, the intestine
turns slightly ventrally and then dorsal, maintaining a
straight line along the left side to just beyond the pancreas, where it makes a sharp bend to the right side while
continuing dorsally. It then gently bends to the left and
passes ventral, crossing the midline at the umbilicus. This
Fig. 5.
Intestine and embryo outline from stage 23–24.
results in the postumbilical small intestine shifting from
the midline at the caecal buds to the left side at the
umbilicus. The preumbilical intestine is now clearly identifiable as duodenum (cranial to the completion of the
sharp bend from left to right) and preumbilical small
intestine (caudal to this).
Umbilicus: the gut is still open at the extremity of the
umbilical loop in the small intestine. This extends a little
further into the postumbilical small intestine, which is a
shorter, thicker tube than that of the preumbilical small
intestine. The omphalomesenteric artery passes through
the mesentery of the pre- and postumbilical small intestine almost parallel to the former, having arisen form the
dorsal aorta at a large caudally directed obtuse angle.
Large intestine: the caecal bulges have extended laterally, making a sharp demarcation from the lengthened
colorectum, which is now up to three somites in length.
Dorsal mesentery: widened throughout the intestine
other than just cranial to the allantois, where the gut is
closely attached to the dorsal body wall.
Stage 25 (4 43 d; H&H, 4 21 d; H, 4 21–5 d; T&F, 4 43 d;
5
A&N, 4 8 d; Fig. 6).
Displacement: the duodenal and umbilical flexures of
the intestine are more developed. The ventral loop of the
914
SOUTHWELL
Fig. 7.
Fig. 6.
Outline of intestine from stage 27–28.
Outline of intestine from stage 25–26.
umbilical small intestine has now clearly twisted right to
the left, resulting in the preumbilical region lying on the
right side and the postumbilical on the left side. This shift
has brought the omphalomesenteric artery into close association with the preumbilical small intestine.
Umbilicus: entirely closed except for a small opening to
the stalk of the yolk sac. There is little change in the
subsequent stages.
Small intestine: the postumbilical region is shorter and
thicker than the preumbilical region.
Large intestine: from the ventral aspect the caecal buds
make a sharp lateral angle caudally but narrow gently
cranially. The colorectum narrows in the caudal to middle
half, but gently widens toward the caecal buds.
Dorsal mesentery: widened slightly. Remak’s nerve
present in the mesentery at its attachment to the dorsal
wall of the colorectum.
Stage 26 (5 d; H&H, 4
A&N, 5 d; Fig. 6).
1
2
–5 d; H, 5 d; T&F, 5 d;
Displacement: the thickened loop of the duodenum
crosses transversely from the left side of the body to the
right, where the emerging ascending limb is directed dorsally. The preumbilical small intestine passes caudally on
the right side and the postumbilical small intestine passes
cranially on the left side, resulting in a sharp S-bend in
the small intestine. The umbilicus arises in the midline
from the apex of the ventrally looped small intestine.
Small intestine: the umbilical loop is elongated ventrally with the pre- and postumbilical segments of similar
length and thickness.
Large intestine: the caecal buds extend laterally and
slightly ventrally and are approximately symmetrical at
cranial and caudal borders when viewed from the ventral
aspect. The narrow segment in the middle of the colorectum is lengthened. A gradual expansion both cranially to
the caecum and caudally to the allantoic stalk can be seen.
Remak’s nerve: extends to the caecum.
Cloacal area: on the ventral side of the tail curvature,
immediately caudal to the allantois, a cranially directed,
crescent-shaped depression lays transverse to the longitudinal axis of the body.
Stage 27 (5 21 d; H&H, 5 d; H, 5–5
1
A&N, 5 2 d; Fig. 7).
1
2
d; T&F, 5
1
2
d;
Displacement: the umbilical loop has twisted almost at
right angles to the midline with the pre- and postumbilical
segment of the small intestine almost parallel. The apex of
the umbilical loop is displaced cranially. The omphalomesenteric artery has shifted toward the middle of the mesentery between the pre- and postumbilical segments.
INTESTINE DEVELOPMENT IN CHICK EMBRYO
915
Small intestine: the duodenum retains its position well
ventral to the stomach. The ascending limb is parallel
with the preumbilical small intestine, both of which lie in
a dorsoventral plane at right angles to the body wall. Both
regions of the small intestine have increased in length.
Large intestine: the cranial and caudal boarders of the
caeca are not symmetrical, as the caeca extends cranially
on either side of the caudal 1/3 of the postumbilical gut.
The narrow segment of the colorectum has lengthened,
occupying more than half the length between the caecal
junction and the allantoic entry.
Remak’s nerve: extends beyond the caeca to the postumbilical small intestine.
Cloacal area: the crescent-shaped depression is now
flanked cranially and laterally by small flattened papillae.
Stage 28 (6 d; H&H, 5 21 d; H, 5 21 – 6 d; T&F, 5 43 d;
A&N, 6 d; Fig. 7).
Displacement: little change other than increased length,
resulting in a larger angle between the small and large
intestine. The caeca and caudal small intestine make an
angle of up to 45° with the dorsal body wall and curve into
the colorectum that lies parallel to the dorsal body wall.
Small intestine: duodenum is similar to the previous
stage, although the gizzard had moved slightly caudally
and a little ventral. The descending limb is still much
shorter than the ascending limb. Both pre- and postumbilical limbs have lengthened.
Large intestine: due to an overall increase in length, the
caeca continue to occupy the caudal 1/3 of the postumbilical small intestine. While the caeca are still connected to
the postumbilical small intestine, a mesentery appears,
connecting the outer thickened tubes with the inner
postumbilical intestine. Further growth of the colorectum
maintains the previous size relations. The enlarged cranial and caudal colorectum angle ventrally from the narrower mid-colorectum, which is against the dorsal body
wall.
Remak’s nerve: difficult to see in the umbilical loop due
to a narrow mesentery occupied almost entirely by the
omphalomesenteric artery.
Cloacal area: the depression evident in previous stages
has deepened and the papillae are closer together, forming
a cranially directed crescent shaped slit that lays transverse to the longitudinal axis of the body.
Fig. 8.
Outline of intestine at stage 29.
the colorectum. Half or more of their ventral extent occupies the umbilicus.
Large intestine: the caeca are still shorter than the
colorectum and are now clearly tubular connected to the
postumbilical small intestine by a thin mesentery. Together, the caeca and caudal small intestine make a sharp
angle (approaching 90°) at the caecal junction with the
colorectum, the mid-region of which had lengthened and
descends at a 45° angle to the dorsal body wall, where the
caudal enlarged region follows the ventral curve of the
body.
Remak’s nerve: little change.
Cloacal area: the lateral papillae are raised ventrally,
forming a lateral ridge. The caudal edges of the lateral
papillae remain separate in the midline. The cranial papilla (the phallus) arises in the midline and is directed
caudally.
d; T&F, 6 d;
Stage 30 (7 d; H&H, 6 21 d; H, 6 21–7 d; T&F, 6 21–7 d;
A&N, 7 d; Fig. 9).
Displacement: the gizzard has enlarged and extends
causally to the umbilical loop. Ventrally, it extends to or
beyond the duodenum. The pre- and postumbilical small
intestine occupy the same level on the right and left side of
the midline, respectively. Both approach a 90° angle to the
dorsal body wall for two-thirds of their ventral extend
before bending slightly cranial. In the apex of the umbilical loop, the postumbilical small intestine is a little caudal to the preumbilical small intestine.
Small intestine: the duodenum continues to lie on the
right side. The descending limb has increased in length,
curving sharply caudally, and passes from left to right
while the ascending limb runs ventrodorsal and slightly
cranial, forming the beginning of the duodenal loop. The
pancreas is present in the apex of the loop. Each limb of
the pre- and postumbilical small intestine is larger than
Displacement: the gizzard is enlarged and moved both
caudally and ventrally. It extends to or beyond the umbilical intestine and when viewed from the left side totally
obscures the duodenum and the flexure between its ascending limb and the preumbilical small intestine. The
caudal half of the postumbilical small intestine including
the caeca begins to bend a little cranial to the preumbilical
small intestine.
Small intestine: the duodenal loop has formed, with the
descending and ascending limbs being of equal length.
The descending limb continues to pass caudally and from
left to right. A midline through the apex of the loop and
passing parallel to the two limbs forms an angle of about
30° with the preumbilical small intestine, which continues
to pass at right angles to the body wall in a ventrodorsal
plane. Each limb of the small intestine is clearly longer
than the colorectum but less than twice as long.
Stage 29 (6 21 d; H&H, 6 d; H, 6 – 6
1
A&N, 6 2 d; Fig. 8).
1
2
916
SOUTHWELL
Fig. 10.
Fig. 9.
Outline of intestine at stage 30 –31.
Large intestine: the caeca remain shorter than the colorectum and extend only a little over 1/3 of the caudal
postumbilical small intestine. The caeca begin to shift to
the caudal side of the postumbilical small intestine, almost coming together at their tips but still well separated
toward the caecal junction. The cranial colorectum now
descends to the dorsal body wall at an angle less than 45°.
Remak’s nerve: under suitable lighting, a thin strand
can be seen on the postumbilical side of the bifurcation in
the omphalomesenteric artery and close to the preumbilical small intestine.
Cloacal area: the phallus and lateral papillae are raised
further. The caudal edges of the lateral papillae are still
separated in the midline.
1
2
Outline of intestine at stage 32.
1
2
1
2
caeca have a similar ventral extent. Each limb of the small
intestine is at least twice the length of the colorectum.
Large intestine: the caeca maintain a similar relative
extent as for previous stages. They have shifted caudolateral to the postumbilical small intestine throughout all
but their most caudal extent. The colorectum is thicker
than other regions of the intestine and descends from the
caecal junction to the back body wall at an angle of 30° or
less.
Remak’s nerve: little change.
Cloacal area: the papillae are raised further, forming a
right angle to the body wall that is curved ventrally,
resulting in the papillae being directed cranially. The
caudal edges have come together in the midline, giving the
papillae a short cylindrical appearance. The phallus extends caudally as a ventral cap to the vent.
d;
Stage 32 (7 43 d; H&H, 7 21 d; H 7 21 d; A&N, 8 d; Fig.
10).
Displacement: the gizzard is now clearly ventral to all
but the umbilical half of the small intestine. The postumbilical small intestine has continued to shift gradually
cranial to the preumbilical small intestine. This continues
over subsequent stages.
Small intestine: the duodenal loop is bent ventrally with
the base of each limb being approximately parallel to the
preumbilical small intestine. The apex of the loop and the
Displacement: little change other than increased length
of all features.
Small intestine: the duodenal loop has lengthened in the
dorsoventral plane but is now directed a little caudally.
Each limb is approximately parallel with the preumbilical
small intestine and shorter than the caeca. The apex of the
loop approaches or contacts the postumbilical small intestine, which continues to lie cranial to the preumbilical
Stage 31 (7
Fig. 9).
d; H&H, 7 d; H, 7–7
d; A&N, 7
INTESTINE DEVELOPMENT IN CHICK EMBRYO
917
intestine. Each limb of the small intestine is between two
to three times longer than the caeca or colorectum.
Large intestine: the caeca continue to occupy the caudal
third of the postumbilical small intestine to which they
are joined caudolaterally by a thin mesentery. They are
now of similar length as the colorectum but are a little
thinner than the small intestine. The tips of the caeca
begin to separate from the intestine and recurve caudally.
The colorectum is clearly thicker than the rest of the
intestine, particularly the caudal quarter leading to the
allantoic entry. This region will be occupied by the bursa
of Fabricus in subsequent stages. The colorectum forms an
open U-shape, the caudal half following the ventral curvature of the body wall and the cranial half curving at
about 30° to the body wall before meeting the caecal junction.
Remak’s nerve: can be seen in the ventral third of the
umbilical loop as a thin ganglionated chain separating
from the small intestine with which it remains in close
association in the dorsal two-thirds. The chain can be seen
to pass between the bifurcation of the omphalomesenteric
artery. Caudally it is still a continuous, increasingly thick
chord, closely applied to the colorectum.
Cloacal area: the cloacal papillae have formed a cylinder
(proctodeum), which has lengthened and is directed
slightly caudal of a right angle to the back body wall.
Caudal to the papillae, a dorsally directed depression appears. At this and subsequent stages, the phallus extends
from a ventrocranial position, as a cap to the vent.
Stage 33 (8 d; H&H, 7 21– 8 d; H, 7 21– 8 d; A&N, 8
d; Fig. 11).
1
3
Displacement: as for previous stages. The postumbilical
small intestine is now clearly cranial to the preumbilical
small intestine from the caecal junction up to 2/3 of the
umbilical loop. At the most ventral 1/3 of the umbilical
loop, this is reversed.
Small intestine: further ventrocaudal lengthening of the
duodenal loop so that the apex now overlays the postumbilical small intestine when viewed from the right side.
The arms of the loop are still parallel with the preumbilical small intestine. The loop is now of a similar extent as
the caeca. Each limb of the umbilical small intestine is
about three times longer than the duodenal loop, the
caeca, or the colorectum.
Large intestine: lengthens further, maintaining the relative relationships between features identified in the previous stage.
Remak’s nerve: as for the previous stage. Now fine connections between the nerve and the omphalomesenteric
artery can be seen.
Bursa of Fabricius: can be seen as a small spherical ball
both dorsal and caudal to the allantoic entry following
removal of all tissue dorsal to the urogenital ducts in the
cloacal area.
Cloacal area: little change in the length and direction of
the proctodeum. The caudal midline groove at the fused
edges of the cloacal papillae descends into the deepening
depression immediately caudal to the proctodeum.
Stage 34 (8 21 d; H&H, 8 d; H, 8 d; A&N, 8 ⅔
d; Fig. 12).
Displacement: the gizzard has shifted further caudally,
now obscuring the duodenum, the caeca, and the caudal
Fig. 11.
Outline of intestine at stage 33.
half of the postumbilical small intestine when viewed from
the left side. It approaches or slightly overlays the preumbilical small intestine, which continues to lie well caudal
of the postumbilical intestine.
Small intestine: the duodenum has continued its ventrocaudal growth. The apex of the loop extends to the
ventral quarter of the gizzard and after passing over the
postumbilical small intestine, it approaches the preumbilical small intestine when viewed from the right side.
Each limb of the umbilical small intestine continues to be
approximately three times longer than the duodenal loop,
the caeca, and the colorectum.
Large intestine: lengthening and relative relationships
of the caeca are maintained as in previous stages. As a
result of the caudal shift of the gizzard, the cranial arm of
the U-shaped bend in the colorectum is displaced dorsally.
Hence the colorectum bends sharply ventral within the
first caudal quarter of its length, the remainder of which
follows the curve of the body wall.
Remak’s nerve: it has now separated some distance
from the ventral umbilical intestine. Nerve trunks connect
918
SOUTHWELL
Fig. 12.
Outline of intestine at stage 34.
to both the omphalmesenteric artery and the umbilical
intestine. It is clearly ganglionated and observable along
an increasing extent of the umbilical intestine. Little
change in the region of the colorectum.
Bursa of Fabricius: it has now extended cranial to the
allantoic connection with urodeum.
Cloacal area: the proctodeum is directed caudally following the curve of the back body wall in continuity with
the colorectum. The groove in the midline of the caudal
wall descends into the caudal depression, which had deepened further and is now directed cranially.
Stage 35 (9 d; H&H, 8 –9 d; H, 8 –9 d; T&F, 9 d;
A&N, 9 d; Fig. 13).
Displacement: the gizzard extends further caudally.
When viewed from the left side, it lays over the dorsal part
of both limbs of the umbilical intestine and approaches the
caudal colorectum. The apex of the duodenum can now be
seen caudoventral to the gizzard. The relative position of
the umbilical intestine had not changed.
Fig. 13.
Outline of intestine at stage 35.
Small intestine: the duodenum runs from the midline in
a ventrocaudal direction to the right body wall, where it
bends caudally, reaching the postumbilical small intestine. At the caudal bend, the descending limb lays ventral
to the gizzard. The relative relationships of the umbilical
small intestine, identified at previous stages, are maintained.
Large intestine: little relative change in the caeca. The
further caudal shift of the gizzard displaces the whole of
the colorectum against the dorsal body wall. The caeca
and postumbilical small intestine bend sharply ventral
just caudal to the caecal junction.
Remak’s nerve: it is becoming ganglionated in the colorectal region with which it is still closely associated. As a
result, nerve trunks to the colorectum cannot be seen.
Bursa of Fabricius: extends cranially almost to the level
of the clearly increased diameter of the caudal gut (coprodeum), becoming oval- rather than spherical-shaped.
Cloacal area: little change other than a narrowing of the
depression immediately caudal to the proctodeum.
INTESTINE DEVELOPMENT IN CHICK EMBRYO
919
DISCUSSION
Variations in Stage of Development With
Temperature
Fig. 14.
Outline of intestine at stage 36.
Temperature and humidity affect the development of
avian embryos. A range of up to 18 hr in the times that
stages appear is consistent with previously reported variability and differences in incubation temperature. A later
appearance of stages 16 –36 was found also in a previous
study (Allan and Newgreen, 1980) with the optimum of
38 ⫾ 1°C at 60 –70% relatively humidity for fowl embryos.
Hamburger and Hamilton (1951) compiled stages 14 –35
of the commonly used fowl embryo staging from eggs incubated at higher than optimum temperature and humidity requirements (39.4°C without draft).
To standardize the estimated chronology for incubation
at 38°C, Hamilton (1952) made some adjustments for
stages 18 –31 to the times reported by Hamburger and
Hamilton (1951). Thompson and Fitzharris (1979), who
incubated their eggs at 37.7 ⫾ 0.5°C at 80 –90% relative
humidity, noted consistently slower developmental times
than the standard times provided by Hamburger and
Hamilton (1951). In this study with incubation at 38°C,
stages 18 –24 were found at the times reported by Hamilton (1952). However, the common times for stages 16 and
17 were later than the slower extreme of the range given
by Hamilton (1952), who did not adjust the times for these
stages from those given by Hamburger and Hamilton
(1951). Thompson and Fitzharris (1979) report the slower
development of these stages at lower temperature
(37.7°C). The times for stages ⬎ 25 occurred more often at
the slower extreme of each range given by Hamilton
(1952) and 12 hr slower than by Hamburger and Hamilton
(1951). The times to reach stages 32–34 are slightly
shorter than those in Allan and Newgreen (1980). For
stages 32–34, Hamilton (1952) made no adjustments to
the times originally provided by Hamburger and Hamilton
(1951). In the diagrams, the time of appearance of each
stage in all four studies is listed.
To confirm that the differences in timing were due to
temperature, eggs were incubated at 39.4°C as reported
by Hamburger and Hamilton (1951). Stages were reached
at or before times reported by Hamburger and Hamilton
(1951) (data not shown).
Growth and Migration in Gut
Stage 36 (9 21–10 d; H&H, 10 d; H, 10 d; Fig. 14).
Displacement: a further caudal shift of the gizzard to
overlay part of the caudal colorectum when viewed from
the left side. The gizzard also crosses well to the right side,
displacing the small intestine closer to the right body wall.
Small intestine: duodenum is similar to the previous
stage with a sharper caudal bend in the distal third of the
loop. Little change in the relative relationships of the
umbilical small intestine. Bends in the pre- and postumbilical small intestine that will form into subsidiary loops
in these regions in subsequent stages can be seen.
Large intestine: overall growth. Little relative change.
Remak’s nerve: ganglionated throughout its length.
Separation from the colorectum is beginning.
Bursa of Fabricius: has reached its definitive cranial
extent dorsal to the coprodeum. Clearly oval-shaped.
Cloacal area: little change.
The different growth rates of two closely associated
primordia are important when considering how one shifts
relative to the other. Thus, the displacement of one primordia relative to another may be achieved simply
through differential growth. Conversely, the relationship
between two apparently separate regions can be maintained by similar growth rates from earlier, more closely
associated primordia. This latter point is illustrated by
the growth of the caeca and caudal postumbilical small
intestine. Following their early appearance as a mere
swelling in the postumbilical gut (stage 21), each caecal
bud extends laterally and ventrally (stage 26). In doing so,
they come to lie parallel to the caudal third of the postumbilical small intestine, with which they maintain continuity (stage 27). The connection between the caeca and the
caudal small intestine is maintained only by a thin mesentery during the following stages, but both regions undergo parallel growth phases.
920
SOUTHWELL
Neural crest cells migrate from the neural tube into the
proximal intestine and along the forming gut tube and
differentiate into enteric neurons (Yntema and Hammond, 1954; Andrew, 1971; Le Douarin and Teillet, 1973;
Teillet, 1978; Newgreen et al., 1980). The roles of growth
(relative proliferation rate) and migration (the movement
of one primordium relative to others) need to be considered carefully when dealing with such lengthy migratory
pathways (Newgreen et al., 1996). In the current study,
illustrations accompanying each stage description have
been drawn to scale, permitting accurate estimates of
length and volume measurements. In association with
other data, we have used these parameters to obtain estimates of migration and proliferation rates of enteric
neuron precursors (Newgreen et al., 1996). This staging
system should also facilitate molecular studies (McBride
et al., 2003) and comparisons between studies.
ACKNOWLEDGMENTS
This staging was originally prepared with Iain J. Allan,
who is deceased. The author thanks Jessica Thomas for
preparing the manuscript. Parts of the diagrams were
used in a detailed report of the growth of gut regions
(Newgreen et al., 1996). The staging was also used by
McBride et al. (2003) prior to publication.
LITERATURE CITED
Allan I, Newgreen D. 1980. The origin and differentiation of enteric
neurons of the intestine of the fowl embryo. Am J Anat 157:137–
154.
Andrew A. 1971. The origin of intramural ganglia: IV, the origin of
enteric ganglia—a critical review and discussion of the present
state of the problem. J Anat 108:169 –184.
Hamburger V, Hamilton H. 1951. A series of normal stages in the
development of the chick embryo. J Morph 188:49 –92.
Hamilton H. 1952. Lillie’s development in the chick, 3rd ed. New
York: Holt, Rinehart and Winston.
Hodges R. 1974. The histology of the fowl. New York: Academic Press.
King A. 1975. Aves urogenital system: cloaca. Philadelphia, PA: Saunders.
Le Douarin N, Teillet M. 1973. The migration of neural crest cells to
the wall of the digestive tract in avian embryo. J Embryol Exp
Morphol 30:31– 48.
McBride H, Fatke B, Fraser S. 2003. Wnt signalling components in
the chicken intestinal tract. Dev Biol 256:18 –33.
McLelland J. 1975. Aves digestive system. In: Getty R, editor. Sisson
and Grossman’s the anatomy of domestic animals. Philadelphia,
PA: Saunders. p 1872–1876.
McLeod W. 1939. Anatomy of the digestive system of the domestic
fowl. Vet med 34:722–729.
Newgreen D, Jahnke I, Allan I, Gibbins I. 1980. Differentiation of
sympathetic and enteric neurons of the fowl embryo in grafts to the
chorio-allantoic membrane. Cell Tissue Res 208:1–19.
Newgreen D, Southwell B, Hartley L, Allan I. 1996. Migration of
enteric neural crest cells in relation to growth of the gut in avian
embryos. Acta Anat 157:105–115.
Romanoff A. 1960. The avian embryo. New York: Macmillan.
Romer A, Parsons T. 1977. The vertebrate body, 5th ed. Philadelphia,
PA: Saunders.
Teillet M. 1978. Evolution of the lumbo-sacral neural crest in the
avian embryo: origin and differentiation of the ganglionated nerve
of Remak studied in interspecific quail-chick chimaerae. Wilhelm
Roux’s Arch 184:251–268.
Thompson R, Fitzharris T. 1979. Morphogenesis of the truncus arteriosus of the chick embryo heart: tissue reorganization during septation. Am J Anat 156:251–264.
Yntema C, Hammond W. 1954. The origin of intrinsic ganglia of trunk
viscera from vagal neural crest in the chick embryo. J Comp Neurol
101:515–541.
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