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the summit of the papilla (fig. 210).

According 1 to the observations of Golgi, the Malpighian corpuscle of each uriniferous tube
is always intimately adherent to a part of the tube near the commencement of the second
convoluted tubule (fig. 212), and has retained this adhesion from its earliest appearance in the
embryo, when the tube is an S-shaped projection from the collecting tube. For of the three limbs
of the S, the lowermost embraces the glomerulus, and forms the Malpighian corpuscle : the
middle one develops into the first convoluted tube, and all the parts of the tube of Henle
(including the spiral and irregular tubes) while the upper part of the S forms the second con-
voluted and junctional tubes (figs. 212, 213).

Structure of the tubules. The tubules consist in every case of a basement
membrane and epithelium, but the character of the latter as well as the size of the
tubes varies considerably in the different parts.

The capsule (fig. 216, ) is lined by a layer of flattened cells, which is
reflected over the contained tuft of blood-vessels, dipping between the separate
bunches of which this-is composed. This layer is much more easily recognized in
the foetus and young subject than in the adult (fig. 215). At the commencement



198



THE URINARY ORGANS.



of the convoluted tubule and sometimes, as in the mouse, even in the part of the
Malpighian corpuscle nearest the tubule, the epithelium becomes cubical. It has
been stated by Hassall (various mammals), and by Klein (mouse) that the epithelium
here is provided with cilia, but the statement requires confirmation. In lower
vertebrates, as in the frog, the existence of cilia in this place has long been known.

The first convoluted tubule has an epithelium of a peculiar character (Heiden-
hain). The part of the cell which encloses the nucleus is composed of ordinary
granular-looking protoplasm, but the part next to the basement membrane is
chiefly made up of straight or nearly straight rods or fibrils placed vertically
to the basement membrane and extending a variable distance towards the

Fig. 214. PORTIONS OF KIDNEY TUBULES (ISOLATED). (Cadiat. )
a, large collecting tubule ; 6, loop of Henle.

lumen (figs. 216, 217), but usually occupying the greater
part of the cell, although there is always a stratum of
homogeneous or granular substance bounding the cell
towards the lumen. The nucleus is spherical. The cells
are with difficulty separated from one another, at least in
some animals (e.g., dog), owing to their possessing lateral
ridge-like processes (fig. 217, e ; fig. 218) which interlock
with one another (Schachowa).

The spiral tubule of Schachowa is the continuation of
the convoluted tubule into the medullary ray, and possesses
a similar epithelium (fig. 216, e). Towards its termination,
however, the cells become shorter and less distinctly fibril-
lated, but split up more completely at their borders into
ridges with intervening furrows, especially in the part of the
cell next to the basement membrane, so that the cells bear
somewhat the aspect of columns deeply fluted at their base.
Between these fluted cells, others of clearer aspect are found
fitting in, and having an expanded base which extends partly
underneath them. According to Schachowa they are present
also in the convoluted tubules proper.

In the narrow tube which forms the descending limb of
Henle's loop, the epithelium is quite low, and flattened
against the basement membrane. The protoplasm is clear
and the nucleus prominent. The ridge-like processes at
the base of the cells are said not to be altogether absent even here.

The loop of Henle has an epithelium similar in character to that of the descending
limb.

In the ascending limb of the looped tubule the epithelium again takes on the
character which is exhibited in the first convoluted and spiral tubes, but the cells
are rather smaller, the lumen of the tube relatively larger, and the intracellular
rods not so long as in those tubes. The cells of this segment are sometimes set
obliquely so as to overlap one another. In the human subject they contain brown
pigment-granules (Klein). This tubule is apt to exhibit a spiral character. It is
divisible into three parts, viz., a lowermost tapering part, a part in the boundary
zone (fig. 211, 7, 8) which is the largest, and a part in the cortical zone (9) which
is narrow and has strongly rodded epithelium, and may be looked upon as the
commencement of the next tubule.

In the irregular tubules the rod-like structure of the cells is very distinct
(fig. 216, b). The cells are very unequal in size, the irregularity of the tubules




THE KIDNEYS.



199



being thus compensated, and the lumen rendered nearly the same throughout.
The nucleus is oval. These tubules are said to lack a basement membrane.

The second convoluted tubule (intercalary tube, Schweigger-Seidel) is like the first
in size, but has a different kind of epithelium. The cells, which are rather long,

Fig. 215. SECTION OF] CORTICAL SUBSTANCE OF

KIDNEY : HUMAN FCETUS. HlGHLY MAG-
NIFIED. (Klein.)

a, glomerulus with blood-vessels not fully
developed ; ft, connective tissue between the
blood-vessels; c, epithelium covering it continuous
with d, nattened epithelium lining Bowman's
capsule ; /, /, convoluted tubes.

with a relatively large nucleus, present
a peculiar highly refractive appearance,
and where they rest on the membrana
propria, the protoplasm exhibits pro-
jections which fit between those of
neighbouring cells.

The junctional tubule, which unites
the last-named to the collecting tubes,
is narrow, but its lumen is relatively
large. It is lined by clear flattened
or cubical cells ; but between them some cells are found which are similar in
appearance to the cells which line the segment just described.





Fig. 216. TUBULES FROM A SECTION OF THE DOG'S KIDNEY. (Klein and Noble Smith.)

a, Capsule, enclosing the glomerulus ; n, neck of the capsule ; c, c, convoluted tubules ; b,
irregular tubules ; d, collecting tube ; e, e, spiral tubes ; /, part of the ascending limb of Henle's loops
here (in the medullary ray) narrow.

The collecting tubes, which are characterised by their straight course and
very distinct lumen (fig. 21(5, d\ are lined by a clear cubical epithelium, the cells
of which are at first somewhat irregular, but become longer and more regular as
the tubes approach the papilla.



200



THE UJEUNARY .'ORGANS.



: In ; the larger collecting or excretory tubes (ducts of . Bellini) the form of the
cells is typically columnar, modified only by the form of the surface which they
cover. ; In these largest tubes the basement membrane is said to be absent, the
epithelium cells resting directly upon the connective tissue.

9





Fig. 217. TO ILLUSTRATE THE STRUCTURE OF THE EPITHELIUM OF THE CONVOLUTED TUBULES

. . (from Heidenhain).

d, section of a convolated tubule from the rat, showing the unaltered protoplasm occupying a
circular area around the nucleus of each cell ; a, b, c, isolated cells from the convoluted tubules of the
rat ; e, isolated cells from the dog's kidney, viewed from the inner surface, and showing the irregular
contour of the protoplasm ; /, isolated cells from the newt, showing the rods and the homogeneous
cuticular layer ; g, longitudinal optical section of part of a convoluted tubule from the dog's kidney.

The characters of the epithelium in the several parts of a uriniferous tube may
be thus concisely stated, viz., clear flattened cells in the capsule, the descending
part of Henle's loop and the loop itself ; granular -look ing rodded epithelium with




Fig. 218. PORTION OF A CONVOLUTED TUBE FROM THE KIDNEY, SHOWING THE IRREGULARLY FLUTED
OUTLINES OF THE CELLS. (Landauer. )

fluted interlocking borders in the convoluted tubules, the spiral tubules, the
ascending limb of Henle's tubule, and in the irregular tubule ; clear cubical or
columnar cells in the junctional tubule, the collecting tubules, and the ducts of
Bellini.

Klein describes a very delicate nucleated membrane lining the tubules within the epithe-
lium, in all the tubes except the descending limb of Henle's loop, and in the loop itself.



THE KIDNEYS.



201



Elood-vessels. The kidneys are highly vascular, and receive their blood from
.the renal arteries, which are very large in proportion to the size of the organs they
supply. Each renal artery divides into four or five branches, whicTT, passing in at
the hilum, between the vein and ureter, may be traced into the sinus of the kidney,
where they lie amongst the infundibula, together with
which they are usually embedded in a quantity of fat.
Penetrating the substance of the organ between the
papillae, the arterial branches enter the cortical sub-
stance which intervenes between the pyramids of
Malpighi, and proceed in this, accompanied by a
sheathing of areolar tissue, and dividing and sub-
dividing, to reach the bases of the pyramids, where
they form arterial arches between the cortical and
medullary parts, which however are not complete, and
in this respect differ from the freely anastomosing
venous arches which accompany them. From the






Fig. 219. MALPIGHIAN CORPUSCLE FROM THE RABBIT'S KIDNEY : NITRATK OF SILVER PREPARATION.

HIGHLY MAGNIFIED. (Ludwig. )

v, vas afferens, showing its epithelial lining : at v', the transverse muscular fibres are also seen ; e,
vas efferens ; a, a', basement membrane of capsule with epithelioid markings, passing at h into that of
the commencing uriniferous tubule.

Fig. 220. DIAGRAM OF THE DISTRIBUTION OF THE BLOOD-VESSELS IN THE KIDNEY (from Ludwig).
at, ai, interlobular arteries : vi, m, interlobular veins ; fj, a glomerulus ; vs, stellate vein ; ar, vr,
arteriae et vcnce rectse forming pencil-like bundles, ab, vb ; vp, venous plexus in the papilla?.

arches peripheral branches (artericc. interlolulares (fig. 220, ai}} are given off, which
pass outwards between the medullary rays and amongst the convoluted tubules,
pursuing a nearly straight course towards the surface of the organ. As they proceed



202



THE UEINAEY OBGANS.



they give off at intervals short and usually curved branches (arterm glomerulorum)
which proceed without further division to the dilated ends of the uriniferous tubules.
Within the capsule the small artery (vas adferens) breaks up into a larger number
of capillary vessels which have a convoluted arrangement, and are closely held
together by connective tissue to form a spheroidal vascular tuft, the glomerulus of
Malpighi. A vein (vas efferens) smaller than the artery, emerges from the glome-
rulus close to the point where the artery enters ; but, instead of joining with other
small veins to form larger venous trunks, as is the case in other organs, the efferent
vessel divides into branches after the manner of an artery, and from these arises a
dense network of capillaries which everywhere ramify over the walls of the urin-
iferous tubules (fig. 221), the meshes of the network being polygonal amongst the
convoluted tubules and elongated amongst the tubules of the medullary rays. But
the efferent vessels from the lowermost glomeruli break up wholly into pencils of
straight vessels (pseud-arterice rectcz (fig. 220, vr : fig. 223, ef} ) which pass directly





Fig. 221. DIAGRAM SHOWING THK RELATION OF THE URINIFKROUS TUBULES TO THE BLOOD-VESSELS (after

Bowman).

a, one of the interlobular ai'teries ; a', afferent artery passing into the glomerulus ; c, capsule of the
glomerulus ; t, convoluted tube ; e', e', efferent vessels which subdivide in the plexus p, surrounding
the tube, and finally terminate in the interlobular vein, e.

Fig. 222. LOBULES OF GLOMKRULUS OP TIG'S KIDNEY. (Ludwig. )

into the boundary layer of the medulla, and there supply the continuation down-
wards of the medullary rays into the pyramid.

The renal arteries give branches likewise to the capsule of the kidney which anastomose
with branches of the lumbar arteries, and that so freely that Ludwig was able partially to
inject the kidneys of a dog from the aorta after the renal arteries had been tied.

The blood is conveyed from the cortex of the kidney by veins (renfe interlobulares)
which accompany the interlobular arteries, and join the convex side of the venous
arches which lie between the medulla and cortex, and also by veins which lie close
beneath the capsule of the organ, and take origin by the convergence of minute
venous radicles, so as to present a stellate appearance (vence stelhihc). These vessels,
which receive blood from the capsule of the kidney, pass inwards through the
cortex and also join the venous arches.

With the exception of the blood brought by the false arteriae rectas the blood
supply of the medulla is to a great extent independent of that of the cortex,
although of course the capillary network is continuous throughout. The pyramids
are chiefly provided with blood by branches which come off directly from the
concave side of the arterial arches, and passing down into the boundary layer of
the medulla there divide to form bunches or pencils of parallel or slightly diverging
minute vessels (arterm recta, fig. 220, ar\ which by alternating with the bundles of
uriniferous tubules which are passing up to the cortex to form the medullary rays,
produce the characteristic streaked appearance of this part of the pyramid (see
fig. 209).



THE KIDNEYS.



203



The long meshed capillary network which is supplied by the arteriae rectse
is continued down to the apex of the papilla. Here the veins_of_the pyramid
commence in a close plexus of small venous radicles surrounding the excretory
ducts near their orifices (fig. 220, vp). Passing outwards towards the base of the
pyramid, and receiving lateral branches at acute angles from its capillary network,
the same veins become collected together into pencils, the vessels of which (vence
recke) are intermixed with the arterise rectae, and unite into vessels which open into
the concave side of the venous arch.

The venous trunks thence proceed, in company with the arteries, through the
cortical septula between the pyramids, to the sinus of the kidney. Joining




Fig. 223. INJECTED GLOMERULUS FROM THE INNER PAHT OF THE CORTICAL SUBSTANCE OF THE HORSE'S

KIDNEY. 70 DIAMETERS (from Kolliker after Bowman).

a, interlobular artery ; of, afferent vessel ; m, m, convoluted vessels of the glonierulus ; ef, efferent
vessel ; b, its subdivision in the medullary substance.

Fig. 224. SECTION ACROSS A PAPILLA OF THE KIDNEY. (Cadiat. )
a, ducts of Bellini ; b, c, d, tubes of Henle, ascending and descending ; c,f, blood-capillaries.

together, they escape from the hilum, and ultimately form a single vein, which lies
in front of the artery, and ends in the inferior vena cava.

Lymphatics. The lymphatics of the kidney are numerous, consisting of a
superficial set forming a plexus in the fibrous capsule, and of deep lymphatics which
issue from the hilurn with the blood-vessels. Ludwig and Zawarykin showed
that there exists a network of freely intercommunicating lymphatic spaces between
the tubules, in communication both with the lymphatics of the surface and those
which issue with the blood-vessels at the hilum. They are most abundant in the
cortical substance.

Nerves. The nerves which have been traced into the kidneys are small. They
come immediately from the renal plexus and the lesser splanchnic nerves, and contain
filaments derived from both the sympathetic and cerebro-spinal systems. They may



204 THE URINARY ORGANS.

be traced accompanying the arteries as far as their finer branches, and some fibrils
ramify over and amongst the uriniferous tubules, but it is uncertain how they end.

Intel-tubular stroma. Between the tubules and vessels of the kidney,
although they are disposed closely together, a small amount of interstitial connective
tissue is found. It has a more fibrous character in the vicinity of the chief
ramifications of the blood-vessels, and also around the Malpighian corpuscles, and
the tubes of the medullary substance. It is more abundant in the neighbourhood
of the papillas than in other parts of the kidney substance (fig. 224).

THE URETERS.

The ureters are the two tubes which conduct the urine from the kidneys into
the bladder. The dilated commencement of each called the pelvis, which is partly
situated in the sinus 6f the kidney, and into which the calices pour their contents,
has already been described. Towards the lower end of the hilum of the kidney
the pelvis becomes gradually contracted, and opposite the lower end of the gland
assuming the cylindrical form receives the name of ureter.

The ureters measure from fourteen to sixteen inches in length; their ordinary
width is that of a goose-quill. They are frequently, however, dilated at intervals,
especially near the lower end. The narrowest part of the tube, excepting its orifice,
is that contained in the walls of the bladder.

Each ureter passes at first obliquely downwards and inwards to enter the cavity
of the true pelvis, andthen turns forwards and inwards to reach the base of the bladder.
In its whole course it lies close behind the peritoneum, and is connected to neighbour-
ing parts by loose areolar tissue. Superiorly it rests upon the psoas muscle and is
crossed very obliquely from within outwards by the spermatic vessels which descend
in front of it. The right ureter passes close to the outer side of the inferior vena
cava, and often gets in front of this vessel. Lower down the ureter passes either
over the common iliac or the external iliac vessels, behind the termination of the
ileum on the right side, and behind the sigmoid colon on the left. Descend-
ing into the pelvis it lies beneath the layer of peritoneum forming the corre-
sponding posterior false ligament of the bladder, and reaching the side of the
bladder near the base (fig. 227, u), runs downwards and forwards in contact
with it, below the obliterated hypogastric artery, and is crossed upon its inner
side in the male by the vas deferens (i) which passes down between the ureter
and the bladder. In the female the ureter runs along the side of the cervix uteri
and upper part of the vagina. According to Holl at the level of the origin of the
obturator, vesical, and uterine arteries it begins to describe a bow-shaped curve
three and three-fifths of an inch long, which extends to the bladder. This curved
portion is crossed at the level of the external os uteri by the uterine artery which is
separated from the nreter by a venous plexus. Here it lies three-fifths of an inch
external to the cervix. It then passes on to the side wall of the vagina and near
where it pierces the bladder lies between this organ and the anterior vaginal wall.

Having arrived at the base of the bladder about two inches apart from one
another the ureters enter its coats, and running obliquely through them for about
three-quarters of an inch, open at length upon the inner surface by two narrow
and oblique slit-like openings. When the bladder is distended these openings are
situated about an inch-and-a-half from the urethral orifice, and about the same
distance from one another. This oblique passage of the ureter through the vesical
walls, while allowing the urine to flow into the bladder, has the effect of preventing
its reflux.

Varieties. Sometimes there is no funnel-shaped expansion of the ureter at its upper end
into a pelvis, but the calices unite into two or more narrow tubes, which afterwards coalesce



THE URETERS.



205



to form the ureter. Occasionally the separation, of these two tubes continues lower down
than usual, and even reaches as low as the bladder, in which case tie ureter is double. In
rare cases a triple ureter has been met with. Several instances are- recorded in which a
supernumerary ureter, proceeding from the upper part of the kidney, opened directly into the
urethra.

The rig'ht ureter has been seen passing behind the inferior vena cava, and then turning
forwards between that vessel and the aorta (Hochstetter, Morph. Jahrb.. xxi, 636).

In instances of long-continued obstruction to the passage of the urine, the ureters may
become enormously dilated.

Structure. The walls of the ureter are pinkish or bluish white in colour.
They consist of an external fibrous coat, a middle coat of plain muscular tissue, and
a mucous lining. The muscular coat possesses two layers of longitudinal fibres and a
middle circular layer.

The mucous membrane, thin and smooth, presents a few longitudinal folds when
the ureter is laid open. It is composed of areolar tissue which becomes gradually
loose towards the muscular coat, but there is no marked distinction into mucous and
submucous layers. It is prolonged above to the papillae of the kidney, and below
becomes continuous with the lining membrane of the bladder. The epithelium
(fig. 225) is of a peculiar character, like that of the bladder. It is stratified, con-





Fig. 225. EPITHELIUM FROM THE PELVIS OF THE HUMAN KIDNEY. (Kolliker.) 350 DIAMETERS.
A, different kinds of epithelial cells separated ; B, the same in situ.

sisting of four layers (fig. 225, B, in section), in the uppermost of which the cells
are somewhat cubical, with depressions on their under surface, which fit upon the
rounded ends of a second layer of pear-shaped cells ; then follow two layers of
rounded or ovai cells, with processes extending down to the mucous membrane. This
description of the shape of the epithelium cells applies to them as they occur in the
empty condition of the duct, but in the distended state the superficial cells are
flattened out, and the pear-shaped and oval cells are much shorter. All the cells are
connected by " cell-bridges " with one another as in a stratified epithelium. The
superficial cells usually have two nuclei, and are believed to divide by " amitosis."
The deeper cells multiply on the other hand by karyokinesis.

A few small mucous glands have occasionally been described at the upper end of
the ureter and in the renal pelvis, but they appear not to be present in man.
Epithelial downgrowths are occasionally found both here and in the urinary bladder,
and these may occasionally have been taken for glands (v. Brunn). Mucus is
however secreted by the lining epithelium. Lymphoid nodules have been met with
in the mucous membrane of the pelvis of the kidney.

Vessels and Nerves. The ureter is supplied with blood from small branches of
the renal, the spermatic, the internal iliac, and the inferior vesical arteries. The
veins end in various neighbouring vessels. The nerves come from the inferior
mesenteric, spermatic, and hypogastric plexuses. They form plexuses in the outer
and muscular coats containing a few ganglion-cells.



206



THE URINARY ORGANS.



THE URINARY BLADDER.

The urinary bladder (vesica urinaria) is a hollow receptacle for the urine, having
an average capacity of about a pint when moderately filled, but capable of being-
distended to a considerably greater degree.

The average capacity of the bladder is often stated to be greater in the female than
in the male ; and, no doubt, instances of very large female bladders are not unfrequent ;
but these have probably been the result of unusual distension : in the natural condition,
according to Luschkaand Henle. the female bladder is decidedly smaller than that of the male.

The size, shape, and position of the bladder and its relations to neighbouring
parts vary according to the degree of distension of its cavity, and also, when empty,

Fig. 226. DIAGRAM OF MEDIAN SECTION OP EMPTY DTASTOLIC

BLADDER AND ADJACENT PART OP URETHRA. (J. S. )

A, anterior limb of bladder ; P, its posterior limb ; IT, urethra.
The clotted lines show the changes hi the shape of the bladder
during its distension.

according to the condition of its muscular coat,
whether contracted or relaxed. When empty and
relaxed (in diastole) it lies deeply in the pelvis, and
in a vertical median section its cavity, with that of
the adjacent portion of the urethra, is Y-shaped, the
stem of the Y being formed by the urethra, and its
two limbs by the bladder. Of the two limbs the
anterior is the longer, and is directed upwards

forwards, while the shorter posterior limb passes backwards and upwards.

empty diastolic bladder has three surfaces a superior, with its concave




and
The




Fig. 227. LATERAL VIEW OF THE VISCERA OF THE MALE PELVIS. (R. Quain.) \

The left hip-bone has been disarticulated from the sacrum, the spinous process of the ischium cut
through, and the pubis divided to the left of the symphysis ; , bladder ; b b', rectum ; c, mem-



Online LibraryJones QuainQuain's Elements of anatomy (Volume 3:4) → online text (page 25 of 44)