close

Вход

Забыли?

вход по аккаунту

?

Dissections of human seminiferous tubules.

код для вставкиСкачать
DISSECTIONS O F HUMAN SEMINIFEROUS TUBULES
FRANKLIN P. JOHNSON
Departments of A n a t o m y and Urology, University of Oregon Medical SchooT
ELEVEN FIGURES
Whether the tubules of the testis terminate blindly or in
the form of anastomosing loops has for many years been a
matter which has never been satisfactorily determined. This
is attested t o by the fact that in our numerous textbooks of
histology the authors a r e a t variance in regard to the form
of the seminiferous tubules, and, furthermore, by the fact
that none of the authors are able to represent the tubules
graphically in any but the most diagrammatic manner.
When one considers that such eminent anatomists a s
Sappey, Hyrtl, Eberth, Kolliker, Krause, Bremer, Huber and
Curtis, and others have studied this problem and have drawn
conclusions which a r e a t variance with one another, he may
correctly conclude that there are difficulties in its solution
which are not easily overcome. The chief difficulty lies in
the extreme length and tortuosity of the seminiferous tubules,
and in their closely packed condition. The attempts to solve
this problem have been chiefly by means of dissections of acid
macerated material made under the dissecting microscope.
However, Bremer’s study of the human fetal testis was made
from serial sections with the aid of wax models, and Curtis
made a study of the tubule of the rat’s testis by the same
method. The difficulties of the modeling method, its tediousness, and the high possibility of error, have discouraged and
prevented its successful application to the adult human testis.
Maceration and dissection, therefore, still remain the method
of choice for studying the morphology of the seminiferous
tubules, its success, in large part, depends upon proper
technique.
187
188
FRANIi1,IN
P. J O H S S O N
The method of maceration used in the present study is quite
siniilar to that which the authoiu used in 1916 in the separation of tlie lolmlcs of the pig’s liver. The testes are first
thoroughly hardeiiecl in foimalin in toto. Segments ahout
1 cm. iii thickness a r e tlieii iiiatlle, the cuts l x i i q l ) a i ~ ~ l ltoe ltlic.
direction of the scptala or lobules of the testis. The ring of
tunicit vaginalis si~r~~ouiicliiig
the seginent slioulcl not be removed but it should he cut through in oiic o r two places with
ii i-azoi*. Each segment or lnlock is then submersed in i,5 p e r
c w i t hydrochloric acid i i i ~ v h i ~itl i is allomed to remain for
1 (lay to 1 week. Tt is then placed in a suitable dish for clisseetioil, preferably a low Stendcr dish, compleiely covered by
the acid. Heat is then al>l)liedhy means of a Runsen burner
and the acid slowly raised to a temperature just short of hailing. A s the temperature rises one notes a niai*ked slirinkiiig
of the tunica albuginca, which, unless the ahove-described cuts
have been niade, greatly w i r p s the segment. With contiiiuecl
heating the parcnchyina it self shrinks, and a n y warping which
may have occurred corrects itself. The amount of shrinkage
is very great, at least 30 to 40 per cent by volume, but as the
shrinkage is uniform, neither the continuity of the tubules nor
their form is seriously disturbecl. A s the macerat ion progresses the s ~ e c i n i c nt~ iriisa dark brown color nil hecomes
quite soft. The heat is now tipplied very slowly so a s to eliminate ‘bumping,’ as a single ‘bump’ will completely ruin the
sljecimen if it occurs as the maceration nears completion.
The length of time required by the heating pi*ocess is froin
20 to 30 minutes, depending upon various factors. The
optimum degree of maceration is reached when the collagen
fibrils a r e completely dissolved, and appear about the specimen as a dark brown sediment. Thc dish is then removed
from the Ruriseri burner. care being taken to avoid rough
handling. A portion of the acid is removed with a pipette
and water is added, and this pi-occss repeated until practically
all of the acid has been iwnoved. T t is important that boiled
water be used f o r this purpose as hoiling clispcls the a i r
and prevents the formation of minute a i r bubbles which cling
DISSECTIONS OF H U M A N SEILIINIFEROUS TIIBUI,ES
189
to the tubules and greatly interfere with successful teasing.
The water turiis the tubules a yellowish-white color and the
specimen is now ready for the dissecting microscope. If the
tubules cannot be lifted away from one another with great
ease, the maceration has iiot been sufficientlr complete; on
the other hand if the tubules b m i k when an attempt is made
to tease them, the niaccratioii has been carried too far. In
Fig. 1 IIuman seminiferous tubule of the blindly ending type. The small
straight tubule is a t the lower end of the figure. Tlie blind end is located about
half-way between the rete and the periphery of the testis. F o u r blindly ending
diverticula are s w n a t I). A n uncommon type.
Fig. 2 Siniplc loop type of seminiferous tubule, there being no anastomotic
branches present. This is also a n uncommon type of tubule.
Fig. 3 The two anastomotic branches at the lower end of the figure form
a complete ring of convoluted seiriiniferous tubule (see also fig. 9). Such rings
are likewise rare; another is sliown on tubule 13, figure 11.
Fig. 4 A single loop bc+vccn two near-adjacent seminiferous tubules. I n this
and subsequent figures; I), diverticulum; B, branching, X tubule broken or not
followed f o r other reasons.
190
F R A N K L I N P. J O H N S O N
either event it is wise t o discard the specimen and begin over
again, as the best dissections cannot be obtained from such
material. Success with this method depends upon the proper
degree of maceration, and the determination of this requires
experience.
In the present study observations were recorded by means
of a series of drawings which were made as the dissections
Fig. 3 Three seminifcrous tubules with anastomosing branches forming two
complete loops and a complete ring.
Fig. 6 Four tubules forming three eompletcly dissected loops.
progressed. Each branching of a tubule was scrutinized most
carefully by rolling it over and over to exclude the possibility
of a broken tubule being adherent to the tubule which m7as
being followed. Likewise each tubule ending was examined
carefully from different angles to determine whether it was
a rounded blind end o r the end of a cut or broken tubule. It
DISSECTIONS O F H U M A N SEMINIPE1:OVS ‘IY!BUIXS
191
was found impossible to record all the convolutions of the
tubules as they exist in their three dimensions, a s certain portions of the tubules overlie one another and the branchings
and other features of the tubules cannot be properly shown.
They were, therefore, drawn a s though they existed in one
plane and the frequent crossings, overlappings and change of
Fig. 7 The small loop towird the center of the figure does not reach half-way
t o the periphery of the testis. The nuiiierous divertienla give the impression of
blind ends of tubules with anastomoses between them.
plane were largely eliminated to make plain what the dissection revealed. The direction and approximate length of the
tubules and the number of branches and diverticula were
represented a s accurately a s possible.
Photography was found of little value in the recording of
observations. I n order to photograph a tubule it is neces-
192
FRANKLIN P. J O H N S O R
sary to remove it from the underlying tubules to a black
background and fix it in mounting gelatin. Sniall portions of
a tubule can be so handled, but the larger loops and series
of loops present difficulties so great that it did not seem worth
the eEort. Moreover it was found that because of their
elasticity, the tubules refused to lie in a position which would
Fig. 8 Another group of four tubules forming three coiiipletc loops.
permit the clear demonstration of branching, diverticula,
anastomoses, etc. When the elastic tissue surrouiiding the
tubules was softened or dissolved by digestion in artificial
pancreatic juice, the tubules became so fragile that they could
no longer be handled.
Dissections should be begun at the straight tubules. The
uppermost lobules should be carefully lifted up and discarded
as these will contain iiumerous cut ends of the tubules. Such
DISSECTIONS OF HUMAN SEMINIFEROUS TUBULFS
193
dissectioii of whole lobules is easy towaid the mediastiiiuni
where the lobules a r e me11 marked, but becomes increasingly
more difficult toward the periphery of the testis, as in this
region the lobules are frequently ill-defined and a r e held
together by those tubules wkicli pass from oiie lobule to
another.
Fig. 9 l’liotograpli (retonclicd) of :I complete ring of convoluted tubule.
This ring is also shown in figure 3 ;uld is oriented the same \ray. The t w o
straight tubules and the
sliort low(^ anastomotic tuhulr s l l o ~ n at the
bottom of the figure :ire coiled togctlicr in a nmss t h t rcquired dissection to
dc~iioiistrntc tlicir form.
The actual teasing of p r o l m l y l)repared speciiiiens is not a
difficult procedure. The acid dissolves the collageii fibrils and
leaves oiily a frail reticulum wl~icllbinds the tubules together.
The elastic fibrils, however, a r e riot destroyed and retain the
greater part of their elasticity. These fibrils, as sliowii by
Hill form a close network around each tubule but they do not
hind the tubules together. T i 1 teasing, therefore, it is only
necessary t o lift the tubule from its bed by breakiiig the
194
F I i A N R L I N P. J O H N S O N
reticulum, while the elastic network
about it gives it great tensile
strength. I t is necessary in following a tubule to pull it out sufficiently
straight with the dissecting needles
to definitely establish its continuity,
and to scan it for diverticula and
branches. Upon being released,
however, it largely assumes its
fownier shape.
As described by numerous investigators, tlie straight portion of
the sciniiiiferous tubule is about
one-half the diameter of the contorted portion, is thin-walled and
quite straight. It attaches at one
erid to that plexus of epithelial
sinuses known as the rete testis and
at the other to the contorted tubule,
where the deniarcation is verS
abrupt. A t times one sees a caecumlike ending of the contorted tubule,
the straight tubule joining its side.
Such caecum-like terminations may
be eloiigaled to form direrticula as
shown in figure 11, tubule 12. F o r
tlie most part the straight tubules
al*e short a i d of approximately
equal length, so that oiie finds the
majority of the terminations of the
contorted tubules equidistant from
the rcte testis. Occasionally, however, one finds a contorted tubule
which falls short of reaching this
position, and its straight tubule, two
or three times the ordinary length,
will be found coursing alongside the
DISSECTIONS O F HUMAN SEMINIFEBOUS TUBULES
195
terminal portions of other contorted tubules. Straight tubules
usually reach the rete singly, although occasionally two may
unite to form a comiiion trunk (fig. 11, tubule 8).
If a single contorted tubule is followed from the straight
tubule peripherally, it is noted that the first convolutions a r e
quite sharp, the tubule keeping within the confines of the
narrow portion of the lobule. The conrolutions, however,
gradually increase in breadth, until at approximately one-
Fig. 11 Composite drawing of several dissections to sliow the general arrangenicnt of anasto~nosingloops. The author has taken tlic liberty t o connect u p t h e
broken or iiiifollowed ends of one dissection with those of another. R, branelling
or f o r k ; 11, divcrticulunl; X, broken or unfollowed ends.
third of the radial distance to the periphery they attain their
maximum width. This inner portion of the contorted tubule,
is directed straight toward the periphery, except for the
sniall above-mentioned convolutions. Branchings a r e not frequent in this portion of the tubule but may occur at any
point ; diverticula a r e relatively common.
The outer portion of the contorted tubule shows a decreased
tendency to reach the periphery a t once and frequently turns
196
FRANKLIN P. J O H S S O N
baclrward upon itself in S-shaped loops. In this portion i t
is not infrequent for a tubule t o leave i t s parent lobule aiid
to enter a n adjacent lohule, occasioiially to return later. Once
reachiiig the periphery the tubule ma>* r u n a short course
along it aiid then clip toward tlie mediastiiiuin and after
numerous convolutions, reach the surface again. Frequently
N tubule will maltc several such contacts with the surface
hcforc it fiiiallp contiiiucs its return course toward the rete
testis t o join a straight tubule and complete a loop.
F o r the most part the tubules of the testis form loops of
this type, the two iiinci- ends lviiig in adjacent, o r nearadjaccnt lobules, a i d occasionally i n tlie same. Each such
loop usuallp, though not invariably, possesses one o r more
hixiiclics wliicli form adjacent loops, all united and in series
with one another. To what cstent the loops are joined together in this maiinei- I am unable to state. Hubcr shows
a sci*ics of scveii coniiectcd loops which he isolated from the
rabloit 's testis. T feel confident that oiic coultl find iiincli
larger series of loops in the human testis, inasmuch as loops
without ii side branch (which when traced invariably formed
iiiiother loop) are infrequent.
Llii:istoniosing Im-aiiches mhicli comlilet e a continuous ring
of contorted seminiferous tubule have actually been found
aiitl vcrif id, hut i n my experience they arc infrequent, much
iiiore 'io Ilian the original figure of S a p p y woulcl lead one to
expect. Such rings map be present in either the inner or
onter poi.tioiis of the tuhule a s sho~ v niii figure 1 3 , tuhulcs 10,
11 and 13.
T n in:- dissections T liave f onnd lint two tubules \T-ith unqnestioiiablc 1)liiid c n d i i i g ~ . Tliese m i ' e both simple unbranched
luhnles aiid in ncitlicr case reaclietl the loeripliei*p of the testis
(figs.I and 10). One tubule showed in addition to its blind
tcrmination four, and the other, fire blincllp ending diverticula.
T n lmth cases the 1)lintl tcrmiiiations werc neatly coiled and
hidden from view until uncovered hy careful dissection. S o
hlintl terminatioiis havc heen found in the peripheral portion
of the lobules. Should they esist, they are certainly not
DISSECTIONS
OF HUMAN SEMINIFEROUS
TUBULES
197
numerous. Likewise, simple loops (without branches) have
been found but they, too, a r e infrequent.
Blindly terminating diverticula may be present in any portion of the contorted tubule but are seemingly more numerous
and closer together in the inner portions. They are usually
quite short, seldom exceeding a few millimeters in length.
Their occurrence and distribution is variable, some tubules
may be traced for great distances without encountering any,
while in others they arc relativelv frequent. A definite variation has also been noted i n testes from different individuals.
The longer diverticula at*efound in the outer portion of the
tubules and it is undoubtedly these which Sappey has figured
and described as blind ends of the tubules. It might at first
appear to one that it is a matter of interpretation only whether
such endings are to be regarded a s diverticula or a s the
terminal ends of the tubules, in which interpretation the continuing portion of the tubule is to be regarded a s an wnastoniosing branch. Should the latter he the case we should find
only one ending for each tubule instead of the numerous
‘diverticula’ scattered along its course. It seems a significant fact that these diverticula a r e of relatively late development as no mention is made of them by Bremer in his worl;
on human fetal material and Huber failed to find them in the
rabbit’s testis. Furthermore, Bremer shows that the loops
develop as such from the early network of the medullary
cords and it seems probable that all anastornosing branches
and loops are derived from the network laid down before the
tubules become patent.
Ampulla-like swellings of the seminiferous tubules, such a s
shown by Eberth, have been conspicuous by their absence in
my preparations. The examination of a very large number of
tubules taken from over a dozen different testes, resulted in
the finding of only one. Frequently sharp kinks in the tubules
give the appearance of ampulla-like swellings but when these
a r e studied carefully from different angles they show no real
enlargement of the tubule itself.
198
FRANKLIN P. J O H N S O N
Very occasionally one finds a portion of a tuhulc ~ + i c h
SIIOWS a nitirked d u c t ion in size. This nari*owing in thc
clianicter of the tubule takes place very abruptly, the ~ ~ a r r o r n c d
poi.tioii being approximately one-half the original cliameter or‘
the tubule. Such narrowed portions extend f o r distances of
1 to 10 em. (estimated) when they just as abrupt17 change
to the usnnl dil-inicter of the tubule. Seemingly their convolutions are not a s great a s the larger tubulcs. That they
are not clue to shrinkage causcd by the acid is suhstaiitiatecl
by the fact that they i i i ~occasioiially seen in microscopic
see t ions.
An estimate of the total length of scniiniferous lubules,
based upon a volume of 10 cc. of 13ai.eiichyna aiid a n average
tubular diametcr of 0.2 imni. gives approxiiiiately 800 feet for
cach testis. This figure is slig1itl;v lower tliiin niost other
estimates which h a w been made. S o me;tsni*enients or estimates have been made upon the length of incliviclnal tubules
or loops a s these vary so n i a i k d ~ ~ .
~ONCIlTTSIONS
TT’hile the i*esnlts of the present investigalioii a r e in accord
with those authors who state that the li~imanseminiferous
tubule exists hotli in the form of complete 1001)s aiid blinc1l~oncling tubules, it is iiccessary to modifv this stntcmeut cis
follosvs :
By f a r the niost common tubules a r e the anastomosing
loops, ~ d i i c l ai r c connectecl in a series of nndeterniined estent.
Single, uiianastomosing loops have been found but a r e rare.
Single unb~xncliiiigtubules a r e likewise pi-(.sent but a r c also
rare; neither of the two found iii the course of this study
reached the periphery of the testis. Complete rinqs of
seminiferous tubules likewise were fouiid to be infrequent.
Small divcrticula a r e frequently fonnd irregularly disti*ibutcd
d o n g the course of the human seminiferous tubules.
F r o m the standpoint of comparative anatomy it is of interest to note the following observations: I n certain marsupials the form of the tubules exist only in the form of
DISSECTIONS O F H U M A N SEMINIFEROUS TUBULES
199
simple, unbranched and unanastomosing loops (DeBurlet and
DeRuiter). I n the mouse simple loops are the most frequent
f o r m ; doubled loops are occasionally found, and rarely it
blindly ending tubule is ohserved (DeBurlet and DeRuiter).
I n the rabbit Huber records only anastomosiiig loops; no
blindly ending tubules. I n birds Huber describes a vast and
complex network of tubules which resisted inr rave ling. I n
the human fetus Brenier shows the presence of both loops
and blind endings. I n the human adult simple loops are r a r e
compound loops are numerous, while simple blind endinq
tubules are very infrequent. Diverticula, so f a r as I am
aware have been recorded only in the human seminiferous
tubule.
L I T E R A T U R E CITED
DEBURLET,H. M. 1921 Zur Entmicklung und Morphologie des Saugerhodens.
11. Marsupialier. Zeitsclir. fur Anat. u. Entw., erste Abt., Bd. 61,
S. 19-31.
DEBURLET,
H. M., AND H. J. DERUITER 1920 Zur Entwicklung und Morphologie
des Saugcrhodens. I. Der IIodrn von blus musculus. Anat. Hcfte,
Rd. 178, S. 32.5-383.
BREMER,J. L. 1911 Morphology of the tubules of the human testis and
epididymis. Am. J. Anat., vol. 17, pp. 393417.
HURER,G. CARL 1916 A note on the morphology of the seminiferous tubules
of birds. Anat. Rec., vol. 11, pp. 177-180.
HUBER,G. CARL, AND G. It. CURl'IS 1918 Thc morphology of the SeminiferOUS
tubules of niaminalia. Anat. Bee., vol. 7, pp. 207-220.
RAPPEY, PH. C. 1874 Trait6 d'anatomie descriptive. Paris.
ERERTH,
I(. 1904 Die mannlichen Gesclilechtsorgane, i n Rardeleben 's IIandbuch
der Anatomic des Menschen. Jena.
Документ
Категория
Без категории
Просмотров
3
Размер файла
644 Кб
Теги
dissection, seminiferous, tubules, human
1/--страниц
Пожаловаться на содержимое документа