Paper - The early relation of the auditory vesicle to the ectoderm in human embryos: Difference between revisions

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==EXPLANATION OF FIGURES==
==Explanation of Figures==
 
===Plate 1===


PLATE 1
Auditory vesicle in human embryos
Auditory vesicle in human embryos
Figures 9 to 14. Models prepared from transverse series in the Harvard Em- bryological Collection. In figures 9, 10, and 11 an arbitrary patch of ectoderm, in the region of the auditory placode, is included in the model. The levels which represent the sections shown in the text figure are indicated by horizontal lines.
Figures 9 to 14. Models prepared from transverse series in the Harvard Embryological Collection. In figures 9, 10, and 11 an arbitrary patch of ectoderm, in the region of the auditory placode, is included in the model. The levels which represent the sections shown in the text figure are indicated by horizontal lines.
X 130.
X 130.
9 2.4-mm. embryo, H.E.C., 40. The cavity of the auditory pit is still in com-
9 2.4-mm. embryo, H.E.C., 40. The cavity of the auditory pit is still in com-
Line 112: Line 113:
of the now discontjnuous placodal stalk (see section 71,fig. 6).
of the now discontjnuous placodal stalk (see section 71,fig. 6).


PLATE 2
===Plate 2===


EXPLANATION OF FIGURES
Auditory vesicle and endolymphatic appendage in Iiunmu embryos
 
Auditory vesicle and endolymphatic appendage ilk Iiunmu enibryos
Figures 15 and 16, models prepared froiii a transverse series; figures 17, 18, and 19, from frontal series in the Harwrd Embryological Collection. Figurcs 15
Figures 15 and 16, models prepared froiii a transverse series; figures 17, 18, and 19, from frontal series in the Harwrd Embryological Collection. Figurcs 15
and 16, X 130; 17, 18, and 19, X 45.
and 16, X 130; 17, 18, and 19, X 45.
15 8 niiii., 2066. The cndolyniphatie alqwndage has lengtliened, and is now
 
pyramidal iii outliiie. It 110 longer bears any reniiiaiit of the stalk by which the otocyst arose.
15 8 niiii., 2066. The cndolyniphatie alqwndage has lengtliened, and is now pyramidal in outliiie. It 110 longer bears any reniiiaiit of the stalk by which the otocyst arose.
16 The 8amc nioilel viewed from the front. Note the dein:ircating erc:ise :it the arrow, and the atiscvice of a nodule on the endolymphatic appenrlage.
 
1 7 12 IIIIII., 816. Froiital series. Model, viewed froin behind; cut surface black. Compare the 8-mm. stage. At 12 iiiiii., the appendage is not only consitl(~ra1,lyleiigtlienetl, but tlic two primary portions, the en1:irgetl s:i(wis and ii:irro\ver ductus, are readily distiiiguisliablc from each other; tlicse together arc market1 off sliarl~lyfro111 tlic utricle by a crease (at the arroiv) which eoiistitutcs
16 The same model viewed from the front. Note the dein:ircating erc:ise :it the arrow, and the atiscvice of a nodule on the endolymphatic appenrlage.
 
17 12 IIIIII., 816. Frontal series. Model, viewed froin behind; cut surface black. Compare the 8-mm. stage. At 12 iiiiii., the appendage is not only consitl(~ra1,lyleiigtlienetl, but tlic two primary portions, the en1:irgetl s:i(wis and ii:irro\ver ductus, are readily distiiiguisliablc from each other; tlicse together arc market1 off sliarl~lyfro111 tlic utricle by a crease (at the arroiv) which eoiistitutcs
tlie utricular fold or ‘valve.’
tlie utricular fold or ‘valve.’
18and 19 Models from the 29-mm. and tlie 40-nnn. human enil)ryos (froiikil
 
series, 914 and 1917 rcqieetivcly). 111 thc niodcl of the 40-1nni. embryo the 1)roxiin:il two-thirds of tllc ciidolyinpliatic duct is omitted. Lateral vicvs. The 1iew distal projection of the ciidolyiny~11:iticsac is \yell drfiiicd; this alipcntlage is
18 and 19 Models from the 29-mm. and tlie 40-nnn. human embryos (froiikil series, 914 and 1917 rcqieetivcly). 111 thc niodcl of the 40-1nni. embryo the 1)roxiin:il two-thirds of tllc ciidolyinpliatic duct is omitted. Lateral vicvs. The 1iew distal projection of the ciidolyiny~11:iticsac is \yell drfiiicd; this alipcntlage is a separate growth, and not a derivative of the original stalk of COJlJl~~CtiOJl between the vesicle and the ectoderm.
a scprate growth, aiitl iiot a tlcrivative of the original stalk of COJlJl~~CtiOJl between the vesicle and tlic cctotlcrni.

Revision as of 10:14, 23 July 2015

Anson, B. J., and Black, W. T. 1934. The early relation of the auditory vesicle to the ectoderm in human embryos. Anat. Rec, 58, 127-137.


The Early Relation Of The Auditory Vesicle To The Ectoderm In Human Embryos

Contribution no. 191 from the Anatomical Laboratory of Northwestern University Medical School. This study constitutes a subsidiary phase of an investi- gation conducted under the auspiccs of the American Otological Society. Paper read at the New York City meetings of the American Association of Anatomists, February, 1932; abstract, Anatomical Record, vol. 52, no. 1,pp. 2-3, February 25, 1932.


Barry J. Anson And William T. Black, Jr. Department Of Anatomy, Northwestern University Medical School, Chicago

Eiqht Text Figures And Two Plates (Eleven Figures)

Perhaps no single feature of mammalian organogenesis is better known or more frequently observed in laboratory courses in embryology than the early development of the membranous labyrinth ; detailed accounts are available de- scriptive of the stages through which the organ passes to assume the form, successively, of placodal thickening, invagi- nated pit, detached sac, and bilobed vesicle with diverticular processes. The exact manner, however, in which the auditory vesicle first becomes a separate structure is not well understood. It is with this phase in the development of the human ear that the present study is specially concerned.


Material And Methods

This investigation was carried out principally upon the series of early human embryos in the Harvard Embryological Collection ; additional observations were made upon compara- ble stagesinthe Department of Embryology of the Carnegie Institution.[1] We were particularly concerned with the stages between 2.4mm. and 12mm., and with only two representative advanced stages, the 29- and the 40-mm. Of the stages from 2.4 to 12 mm., twenty-seven series in the Harvard Collection were studied; of those between 3.0 and 6.6 mm., forty-four series in the Carnegie Collection. The series in the Harvard Collection which best displayed the changing relation of the otocyst to the ectoderm were selected for modeling by the Born wax-plate method; these models, shown in plates 1 and 2, were prepared from the following embryological series: 2.4, 4, 6.3, 8, 12, 29, and 40 mm.


Observations And Discussion

In our models of favorable series in the Harvard Collection it is possible to follow the stages in the disappearance in the original stalk of connection between the auditory vesicle and the outer ectoderm.


In the embryo of 2.4mm. (figs.1and 9) the thickened area of ectoderm, the auditory placode, has become invaginated to produce a pit widely open to the exterior. In an embryo of 3.75 mm. (fig. 2) the auditor sac is still patent.[2] At 4 mm. (figs. 4 and lo), although the orifice has become closed by the the growing together of its margins,[3] the solid stalk remains and holds the vesicle in temporary union with the outer ectoderm; in the two 4-mm. embryos of Keibel and Elze ( '08, figs. 9c and llc-d) the connection is likewise still unruptured. Growth of the vesicle has principally affected its length, so that the stalk is now near the dorsal limit of the lateral aspect. In another series of the 4-mm. stage (fig. 3) the stalk of communication has brokenCite error: Invalid <ref> tag; refs with no name must have content but the outer ectoderm and the adjacent wall of the vesicle are still in intimate contact (compare figs.4and 3); in the embryos 5.3 mm. and 5 to 6 mm. in length described by Keibel and Elze (table, p. 100; figs. 13 a-b)</ref>, the vesicle is detached, but its relation to the ectoderm


Abbreviations For All Figures

a.p., auditory pit a.v., auditory vesicle (otocyst) c.d., cochlear duct coch., cochlear part of vesicle e.ap., endolymphatic appendage e.d., endolymphatic duct e.pr., eiidolymphatic projeetion e.s., endolymphatic sac ep., epidermis l.s.d., lateral semicircular duct m.t., medullary tube plac., placodal stalk sacc., saccule s.s.d., superior semicircular duct utr., utricle vest., vesibular part of vesicle



Figs. 1 to 8 Auditory region. Transverse sections of embryos in the Harvard Embryological Collection. Dorsal aspect downward (except in 3 ) . X 80. 1, 2.4 mm. (CR), H.E.C. (loan) sectioii 28. Auditory pit (see level in model, fig- ure 9. 2, 3.75 mm., H.E.C. 2085, section 159. Auditory pit. 3, 4 mm., 714, section 11. Auditory vesicle in contact with the epidermis. 4, 4 mm., 2302, section 12. Auditory vesicle eoiiiiected with the ectoderm by a solid placodal stalk (see level in model, fig. 10). 5, G.3 mm., 2300, section 67. Placodal stalk now ruptured (see level on fig. 11). 6, 7, 8, 6.7 mm., 2285, sections 71, 72, 73, respectively. Remnants of placodal stalk of attachment persist 011 both the endolymphatic appendage and the epidermis (see level, section 72, in models, figs. 13 and 14). is also one of contiguity. The shape of the vesicle itself in our model is very similar to that in the 4.3-mm. stage modeled by Streeter ('06-'07, fig. a, pl. 1). In our 6.3-mm. embryo (figs.5 and Il),the placodal stalk remains, although not as a continuous structure, but merely as a limited thickening opposite the dorsal sixth of the now piriform vesicle. The latter, now freed, shows the first indication (fig. 12, at arrow) of the constriction which will delimit the endolymphatic ap- pendage. The otocyst, considerably enlarged over the 4-mm. stage, continues to undergo general expansion, and, particu- larly to lengthen ventralward (fig. 14); concurrently, the shallow depressed area, just apparent in the 6.3-mm. stage (fig. 12), becomes a pronounced crease at 6.7 mm. (fig. 13, at arrow) ; it definitely marks off the endolymphatic appendage from the vestibular portion of the vesicle. The development of this crease is due to inpushing of the vesicle's wall, as is proved by the observation that the vesicle, at the root of the growing appendage, is narrower in the 6.7-mm. and 8-mm. embryos than it is in the one of 6.3 mm. (compare figs. 13 and 16 with fig. 12).


On the lateral aspect of the appendage, at the junction of its distal and middle thirds, a nodular projection persists, which is the remnant of the original stalk of connection. This low protuberance extends through eight sections (of 81-1 each), while the corresponding thickening on the adjacent ectoderm is limited in its extent to 1 section (fig. 6)-aiid does not appear above or below (figs. 7 and 8) this level. A corresponding remnant persists on the ectoderm, just oppo- site the nodule on the appendage; at this stage, then, the two vestiges of the stalk of origin have not yet moved away from each other. The nodular vestige on the appendage neither appears in comparable stages pictured by Streeter6 ('06-'07, fig.b, pl.l),and His, Jr. (1889,Taf. I,fig.3),nor is mentioned in the tables of Keibel and Else ( '08) descriptive of compar- 'Since the completion of this paper, the writer has kindly been permitted by Dr. G. L. Streeter to examine the lantern slides of serial sections shown in connection with the latter's paper ('31) read at the Chicago meetings of the American Association of Anatomists; in these series, as Doctor Streeter then pointed out, the vesicle has become detached in 4-mm. embryos, at which stage the stalk may remain as a projection of the epidermis only, or of the vesicle as well. With these observations our own are in agreement (footnote 5).


able stages in which the endolymphatic duct is clearly distin- guishable; it is pictured by Perovic and Aust ( ’15, figs. 1, 2, Taf.44)as holding a more distal position. The fortunate per- sistence, in the series studied, of the two definite, though transitory, remnants of the placodal stalk permits one to ren- der more precise the statement by Keibel (Keibel and Mall, ’12, p. 266) to the effect that the recessus labyrinthi (later, ductus and saccus endolymphaticus) “arises in man in imme- diate relation with the point of closure of the auditory vesicle . . . .”; it may be said, rather, that the point of closure is represented (in the 6.7-mm. embryo) by a nodule-like rem- nant situated on the lateral aspect of the endolymphatic appendage at the junction of its distal and middle thirds; moreover it may be said that the preponderant growth of the vesicle is ventralward while the two remnants of the primitive stalk of origin-of vesicle and of epidermis-still remain apposed.


In the 8-mm. embryo (figs. 15 and 16) the prominences on the vesicle and the epidermis are no longer present, both epithelial surfaces being quite smooth. The endolymphatic appendage has concurrently increased in length and in width by one-half, and has become lance-shaped. The vestibular portion of the vesicle gradually undergoes enlargement and bulges prominently lateralward ; the protrusion removes the endolymphatic appendage from a dorsal to a medial position (Keibel and Mall, ’12, p. 266; Perovic and Aust, ’15); the removal of the appendage from a situation just subjacent to the epidermis to a deeper position, together with the disap- pearance of the placodal stalk, render it impossible to trace any further relation between the freed vesicle and the site of original ectodermal attachment. The delimiting crease seen in the several early stages (figs. 12, 13, and 16, at the arrows) becomes in the otocyst of the 12-mm. embryo (fig. 17) a marked invagination which now further sets off the elongated endolymphatic appendage from the vestibular part of the otocyst. The later now consists of utricle and saccule; from the utricle are given off the diverticular semicircular ducts, from the saccule arises the cochlea. The ledge of tissue which forms the crease (fig. 17, a t arrow; also fig. 13) between the endolymphatic duct and the common point of origin of the superior and lateral semicircular ducts, is the utriculo-endolymphatic fold or 'valve' described by Bast ( '28), Wilson and Anson ( '29), and others.' The endolymphatic appendage in the embryo of 12 mm. is divided into the proximally placed ductus and the distal ex- pansion or saccus. In older embryos (figs. 18 and 19) the sac becomes expanded and flattened medio-laterally ; its free extremity is no longer merely pointed, but is prolonged dor- salward as a thread-like projection (figs. 18 and 19), the occurrence of which has been recorded by Tandler (in Keibel and Elze, '08, tables 55 and 65) and by Macklin ('21)' and its development in man described by Anson ('33). This distal projection does not arise at the point of closure of the vesicle, and therefore cannot be homologous with the elongate patent extremity of the sac in the shark (Scammon, '11, figs. 12, 13, 15,16, of embryos 11.5,15,18, and 20.6 mm. in length; Quiring, '30, fig. 21, pl. 3).

Literature Cited

ANSON,B. J. 1933 The distal projection of the endolymphatic sac in human embryos. Anat. Rec., 701. 57, 110. 1, pp. 55~58.

BAST,T. H. 1928 The utriculo-endolympliatic valve. Anat. Rec., vol. 40, 110. 1, pp. 61-64.

HIS, WM., JR. 1889 Zur Entwicklungsgeschichte des Acustieo-Facialisgebietes beim Menschen. Arch. f. Anat. u. Physiol. Anat. Abth. Suppl., S. 1-28.

KEIBEL,F., AND C. ELZE 1908 Nornientafel zur Entwickluiigegeschichte des Menschen. Jena. (Achtes Heft, of Keibel's Normentafeln zur Ent- wicklungsgesehichte der Wirbeltiere.)

KEIBEL,F., AND F. P. MALL 1912 Maiiual of human embryology, vol. 2, Phila- delphia.

MACXLIN,C. C. 1921 The skull of a human fetus of 43 mm. greatest length. Contrib. to Embr., no. 48, extracted from Publ. 273, Carnegie Instit. Wash., pp. 57-103.

PEROVIDC.,, AND 0. AUST 1915 Zur Entwickelungsgeschichte des Ductus endo- lymphaticus beim Menschen. Anat. Hefte, Bd. 52, S. 699-716. QUIRING,D. P. 1930 The development of the ear of Acanthias vulgaris. J. Morph. and Physiol., vol. 50, 110. 1, pp. 259-293. 'An account of the development of the fold in vertebrate embryos is in prepa- ration bv the senior author.

SCAMMORN. ,E. 1911 Xormal plates of the development of Squalus acanthias. Jeiia. (Zwolftes Heft of Keibel’s Normentafeln.)

STREETER,G. L. 1906-1907 On the development of the membraiious labyrinth and the acoustic and facial nerves in the human embryo. Am. J. Anat., vol. 6,pp. 139-165. 1931 Early stages in the development of the ear vesicle in the human embryo. Abstract, Anat. Rec., vol. 48,suppl., p. 35.

WILSON, J. G., AND B. J. ANSON 1929 The utriculo-endolymphatic valve (Bast) in a two-year-old child. Anat. Rec., vol. 53, no. 2, pp. 145-153. 


Explanation of Figures

Plate 1

Auditory vesicle in human embryos Figures 9 to 14. Models prepared from transverse series in the Harvard Embryological Collection. In figures 9, 10, and 11 an arbitrary patch of ectoderm, in the region of the auditory placode, is included in the model. The levels which represent the sections shown in the text figure are indicated by horizontal lines. X 130. 9 2.4-mm. embryo, H.E.C., 40. The cavity of the auditory pit is still in com- munication with the exterior through the hollow placodal stalk. See section 28, figure 1. 10 4 mm., 2302. The auditory vesicle has lengthened; the stalk of communi- cation between the epidermis and the vesicle, although still persistent, no longer contains a lumen. See section 12, figure 4. 11 6.3 mm., 2300. The initial indication of the constriction which is destined to separate the endolymphatic appendage from the vestibular portion of the vesicle is now apparent. The epidermis overlying the endolymphatic appendage is still thickened, but no remnant of the original placodal stalk of continuity remains. See section 67, figure 5. 12 The same model, viewed from behind. The arrow points to the constricting crease between the developing endolymphatic appendage and the more pro- tuberant vestibule. 13 6.7 mm., 2285 (viewed from the front). The arrow indicates the deepen- ing crease which limits the endolymphatic appendage and marks the site of the future ‘valve.’ 14 The same model (viewed from the side). The endolymphatic appendage at this stage is readily distinguishable from the vestibular part of the auditory vesicle. The epidermis and the appendage carry tubercles which represent parts of the now discontjnuous placodal stalk (see section 71,fig. 6).

Plate 2

Auditory vesicle and endolymphatic appendage in Iiunmu embryos Figures 15 and 16, models prepared froiii a transverse series; figures 17, 18, and 19, from frontal series in the Harwrd Embryological Collection. Figurcs 15 and 16, X 130; 17, 18, and 19, X 45.

15 8 niiii., 2066. The cndolyniphatie alqwndage has lengtliened, and is now pyramidal in outliiie. It 110 longer bears any reniiiaiit of the stalk by which the otocyst arose.

16 The same model viewed from the front. Note the dein:ircating erc:ise :it the arrow, and the atiscvice of a nodule on the endolymphatic appenrlage.

17 12 IIIIII., 816. Frontal series. Model, viewed froin behind; cut surface black. Compare the 8-mm. stage. At 12 iiiiii., the appendage is not only consitl(~ra1,lyleiigtlienetl, but tlic two primary portions, the en1:irgetl s:i(wis and ii:irro\ver ductus, are readily distiiiguisliablc from each other; tlicse together arc market1 off sliarl~lyfro111 tlic utricle by a crease (at the arroiv) which eoiistitutcs tlie utricular fold or ‘valve.’

18 and 19 Models from the 29-mm. and tlie 40-nnn. human embryos (froiikil series, 914 and 1917 rcqieetivcly). 111 thc niodcl of the 40-1nni. embryo the 1)roxiin:il two-thirds of tllc ciidolyinpliatic duct is omitted. Lateral vicvs. The 1iew distal projection of the ciidolyiny~11:iticsac is \yell drfiiicd; this alipcntlage is a separate growth, and not a derivative of the original stalk of COJlJl~~CtiOJl between the vesicle and the ectoderm.

  1. The tracings were made, at the two institutions, by the senior author; the junior author prepared the wax models.
  2. In the Cariiegie series, the structure is still a pit in four 3-mm. embryos (1182b, 4497, 6050, aud 239) and in two 3.4-mm. embryos (5056 and 6097).
  3. In the Carnegie series of a 3.9-mm. embryo (463) it is also closed but free from the ectoderm, as it also is in all the older stages examined, except one of 4mm. (486) and one of 4.5 mm. (1062) in which the lips are in virtual contact.