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the bile-ducts within the liver. Adjacent trabeculæ become arranged into the lobule, each with a vascular channel in its interior, which communicates with ar network in the surface of the lobule by capillary intervals between adjacent
ntral vein becomes a tributary of a hepatic vein, and the capillary network the terminal
Ventral mesentery en of branches Esophagus
Liver tal vein.
Ventral mesentery roximal portion Stomach
Stomach Eiginal hollow
Spleen im becomes
Spleen luct, and the
Line crosses er and cystic Liver
mesogastrium Pancreas formed by an
Superior mesen. -n from it. Small intestine
teric artery liver increases Superior mesen
Duodenum teric artery begins to pro
Colon from the inSmall
Inferior mesen. c of the septum intestine
teric artery am into the
Vitelline mesentery, SO
duct *, instead of
Cacum ated within the Inferior mesenteric artery
Rectum - looks like an
The mesentery of its inferior
Aorta In other words,
Fig. 977.-Two DIAGRAMS TO ILLUSTRATE THE DEVELOPMENT OF THE im begins to
INTESTINAL CANAL. te into two
The figure to the right shows the rotation of the intestinal loop around the inferior, the
superior mesenteric artery. In both figures the parts are supposed to be a superior, viewed from the left side. onstitutes the ortion of the diaphragm, both of these having been at first one continuous mass. irse of development the separation of the two becomes more marked, and finally te everywhere except at the coronary and lateral ligaments behind, and at the ligament in front, where they are still connected. eliver separates off from the future diaphragm, and descends into the abdomen, cween the layers of the ventral mesentery—a fold which connects the stomach
and duodenum with the anterior abdominal wall. This is divided by the liver into two parts — a lower, stretching from the front (lesser curvature)
of the stomach to the liver, which becomes the Stomach lesser omentum; and an upper, stretching from
the liver to the diaphragm and anterior wall of the abdomen, which forms the falciform ligament.
2. Pancreas.—The pancreas is developed at
a very early period in man (being present in Pancreas
embryos of 5 mm.) from two outgrowths from the alimentary canal, a dorsal and a ventral.
The dorsal rudiment is an outgrowth from "-Duodenum the dorsal aspect of the intestine, anterior to the
origin of the hepatic outgrowth. The ventral rudiment grows at a later stage from the root of the hepatic bud in the form of two ventral
offshoots, one on either side. That on the left -DIAGRAM OF THE ORIGIN OF THE
side, however, soon disappears. LIVER AND PANCREAS.
Through the rotation of the duodenum around
its long axis, the dorsal and ventral rudiments one another and become fused, and their ducts open on the left side of the m. The connecting stalk between the ventral rudiment and the hepatic bud
the main duct of the pancreas, while the connexion of the dorsal outgrowth - duodenum remains as the accessory pancreatic duct. In embryos of the fifth large dorsal pancreatic rudiment is present, and also a smaller ventral rudiment, pens into the duodenum in common with the bile-duct, and lies on the right of
the vena porta. In the sixth week, these two rudiments meet and unite with one another, forming a long slender glandular mass which passes backwards within the dorsal mesogastrium (meso-duodenum), between the vertebral column and the greater curvature of the stomach. The pancreas, so formed, follows the changes which occur in the position of the stomach and of the dorsal mesogastrium. Consequently its free dorsal extremity comes to be directed to the left, while the right extremity or head is included within the hollow of the curve formed by the duodenum. At first, it possesses a dorsal mesentery, a part of the dorsal mesogastrium, but from the fifth month this disappears, coincidently with the rotation of the gland into the transverse axis of the body.
The lower part of the head, the body, and tail of the gland arise from the ventral element, and the upper part of the head arises from the dorsal bud.
The primary diverticula give off buds, lined with cylindrical epithelium, and these in turn give off other buds, and the process goes on until the mass of the gland is formed.
The islets of Langerhans are formed at a very early stage, from the entodermal lining cells of the branching diverticula which form the gland acini.
By A. FRANCIS Dixon.
THE URINARY ORGANS.
s, or glands which secrete the urine, are a pair of almost symmetricorgans, situated in the posterior part of the abdominal cavity, one e of the lower movable portion of the vertebral column. The fluid, reted by the kidneys is received into the upper expanded portions of ng tubes, the ureters, and by them it is conducted to the bladder, iced within the pelvic cavity. From the bladder the urine is passed, curition, along a passage called the urethra to the exterior. În the ethra is a relatively long passage, and traverses the prostate gland and ength of the penis; in the female it is a short tube, and opens on the above the vaginal orifice.
dney (ren), when removed from a fresh subject, presents a bean-shaped t is of a dark brown-red colour, and is surrounded by a thin glistening e tunica fibrosa, which gives to the whole organ a uniformly smooth "he kidney is not a solid body, but contains a cavity called the sinus opening into which, termed the hilum renale, is situated on the medial or part of the organ. Each kidney measures about 44 inches in length, n width, and about 14 inches in thickness, and is placed so that its
is nearly vertical. The weight of the adult kidney is about 41 In the freshly removed kidney the superior and inferior ,ends are rounded, and the extremitas superior or superior end is usually a little y than the extremitas inferior or inferior end. The margo lateralis or rder, which is opposite the hilum, is rounded and convex, while the ialis or medial border, on which the hilum is placed, is concave from above
These two borders separate the facies anterior or anterior surface acies posterior or posterior surface of the kidney. apsule, which envelops the whole organ, divides in the region of the to two layers, one of which is continued over the lips of the hilum interior of the kidney, and lines the walls of the renal sinus. layer is prolonged to form a tubular sheath for the vessels and nerves idney before they pass through the hilum to enter the sinus, within ey break up into branches. These branches, piercing the wall of the ter the substance of the kidney. The upper expanded portion of the ves the sinus, through the hilum, in company with the blood vessels and
ion of the Kidneys.—The precise level of the kidney in the abdominal subject to a considerable amount of variation, and, further, it is usual to ifference in the level of the right and left kidney in the same individual. quently the left kidney is on a somewhat higher level than the right, nany cases the kidneys are found to occupy the same level, or, the more ndition being reversed, the right kidney is a little higher than the left.
as a whole,
If a line is drawn round the body at the level of the lowest part of the thoracic wall, the whole, or almost the whole, of the left kidney will be found to lie above the level of the subcostal plane so determined. It is, therefore, situated in the subcostal zone of the abdominal cavity. The right kidney, however, although it lies for the most part in the subcostal zone, usually projects at its inferior part somewhat below the subcostal plane, and hence lies to some extent in the umbilical
It is often stated that the kidneys are placed on a somewhat lower level in the female than in the male subject.
By far the greater part, usually two-thirds or more, of the kidney lies to the medial side of a line drawn vertically upwards through the middle point of the inguinal ligament.
The posterior aspect of the kidney is closely applied against the muscles attached to the bodies of the last thoracic and upper three lumbar vertebræ, and is placed in front of the last rib and of the transverse processes of the upper three
a & more under on Karoels vis ained fr
The kic Cart of the izsue, ofte in greater front of an bey enter arough th the vess
Inferior vena cava
Inferior Left ureter
mesenteric vein FIG. 979.—DISSECTION TO SHOW THE RELATIONSHIPS OF THE KIDNEYS. The greater part of the stomach
has been removed by an incision made close to the pylorus. The transverse colon has been taken away and the small intestine has been cut across close to the duodeno-jejunal flexure.
A model prepared by the late Professor Birmingham has been made use of in this drawing. lumbar vertebræ. In some cases, more frequently on the left side of the body, the eleventh rib also lies behind the upper part of the kidney. The relationship of the kidney to the lower two ribs is, however, very inconstant, owing partly to the great variability in size and inclination of these bones.
The inferior end of the kidney is usually situated from 14 to 2 inches above the highest part of the crest of the ilium; the interval between the kidney and the ilium being usually greater on the left side of the body.
Sometimes the inferior end of the kidney lies on the same level as, or only a short distance above, the iliac crest; this condition is sometimes due to the crest rising to a higher level than usual, the kidney occupying its normal position in relation to the vertebral column. It is important to remember that during life the kidney moves upwards and downwards, following the respiratory movements of the part of the diaphragm against which it rests.
The long axis of each kidney is somewhat oblique, its superior end approaching nearer to the median plane than the inferior. The surface of the kidney which is applied against the muscles forming the posterior wall of the abdomen looks,
the media ing layer strering ty of the barate, a be kidne
"tunica a tiene enc beterin“ Sheath.
whole, backwards ånd medially, and that which projects into the abdominal
often loaded with fat; the fatty tissue, or capsula adiposa, being present
Head of Pancreas
Transverse colon just below right flexure
Ascending colon just below right flexure
Liver (right lobe) Descending - part of duodenum
1th rib -nephric fat”
Intervertebral fibro-cartilage “Perinephric fat
Crus of diaphragm
which the term fascia renalis is applied. This fascia surrounds the d a considerable amount of its fatty capsule in the form of a loose which may be distinguished anterior and posterior walls. The sheath feriorly and medially, but closed above and to the lateral side of the
the apposition of its walls. Laterally, the anterior and posterior e sheath come into contact and are connected with the retro-peritoneal edially they remain distinct, and the anterior wall is continued across
plane, in front of the renal vessels and the aorta, to join the correspondof the opposite side, while the posterior wall fuses with the fascia e psoas and quadratus lumborum muscles. Inferiorly, below the level Aney, the anterior and posterior layers of the renal fascia remain d can be traced downwards into the iliac fossa. Above the level of and the suprarenal gland the layers of the renal fascia unite and scia covering the diaphragm. It has been suggested that the terms posa” and “
and “perinephric fat” should be restricted to the loose fatty sed along with the kidney within the sheath of renal fascia, and that ranephric body,” or“ fat,” should be used to denote the tissue outside the e fibrous capsule of the kidney is joined to the loose sheath formed by