_1_, Cœliac artery; _2_, gastric artery; _3_, hepatic artery; _4_,
splenic artery; _5_, posterior gastric artery; _6_, anterior gastric
artery; _7_, œsophageal branch; _8_, gastro-duodenal artery; _9_,
pancreatico-duodenal artery; _10_, right gastro-epiploic artery;
_11_, pyloric artery; _12_, left gastro-epiploic artery; _13_, short
gastric branches of splenic.
]
I. The =cœliac artery= or =axis= (A. cœliaca) is an unpaired vessel,
usually half an inch or less (ca. 1 cm.) in length, which arises from
the ventral aspect of the aorta at its emergence from the hiatus
aorticus. It divides on the dorsal surface of the pancreas into three
branches—the gastric, hepatic, and splenic.
1. The =gastric artery= (A. gastrica sinistra) passes downward and
forward in the gastro-phrenic ligament, gives off œsophageal and
pancreatic branches, and divides above and behind the cardia into
anterior and posterior branches.
(_a_) The =anterior branch= (Ramus cranialis) crosses the lesser
curvature just to the right of the cardia and ramifies on the parietal
surface of the stomach. The branches pursue a flexuous course toward the
greater curvature and anastomose with the short gastric arteries and the
gastric branch of the hepatic artery.
(_b_) The =posterior branch= (Ramus caudalis) is distributed in a
similar fashion on the visceral surface.
(_c_) The =œsophageal branch= (Ramus œsophageus) passes through the
hiatus œsophageus into the thoracic cavity above the œsophagus and
anastomoses with the œsophageal branch of the broncho-œsophageal artery.
[Illustration:
FIG. 449.—PLAN OF CHIEF BRANCHES OF ANTERIOR MESENTERIC ARTERY OF
HORSE.
_1_, Stump of anterior mesenteric artery; _2_, stumps of arteries of
small intestine; _3_, external cæcal artery, _4_, internal cæcal
artery; _5_, ileal artery; _6_, ventral colic artery; _7_, dorsal
colic artery; _8_, middle colic or first artery of small colon.
]
The gastric artery often arises by a common trunk with the splenic.
The two terminal branches may arise separately, or the anterior from
the splenic and the posterior from the hepatic. The œsophageal branch
often arises from the splenic or the posterior gastric.
[Illustration:
FIG. 450.—DISSECTION OF SUBLUMBAR REGION, PELVIC INLET, AND INNER
SURFACE OF THIGH OF HORSE.
_Blood-vessels_: _1_, Aorta; _2_, posterior vena cava; _3_, hepatic;
_4_, gastric; _5_, splenic; _6_, _7_, renal; _8_, anterior
mesenteric; _9_, arteries of small intestine; _10_, ileo-cæco-colic;
_11_, dorsal colic; _12_, artery of small colon; _13_, posterior
mesenteric; _14_, external iliac; _15_, internal iliac; _16_,
circumflex iliac; _17_, _19_, anterior and posterior branches of
_16_; _18_, anastomosis with intercostals; 20, spermatic; _21_,
cremasteric; _22_, lateral sacral; _23_, internal pudic; _24_,
umbilical; _25_, femoral; _26_, deep femoral; _27_, anterior
femoral; _28_, branch to gracilis; _29_, saphenous.
_Lymph vessels and glands_: _a_, Lymph vessels; _b_, lumbar glands;
_c_, internal iliac glands; _d_, external iliac glands; _e_,
precrural glands; _f_, deep inguinal glands (position indicated by
dotted line).
_Nerves and ganglia_: _1_, _2_, Left and right cœliaco-mesenteric
ganglia; _3_, posterior mesenteric ganglion; _4_, connection between
_1_ and _2_; _5_, connection between hepatic and splenic nerves;
_6_, _7_, connections between anterior and posterior mesenteric
ganglia; _8_, splanchnic nerve; _9_, lumbar trunk of sympathetic;
_10_, pelvic branches of posterior mesenteric ganglion; _11_,
internal spermatic nerve; _12_, last thoracic nerve; _13_,
ilio-hypogastric nerve; _14_, anastomosis between _13_ and _15_,
ilio-inguinal nerve; _16_, _17_, cutaneous and muscular branches of
_15_; _18_, _19_, muscular and scrotal branches of external
spermatic nerve; _20_, external cutaneous nerve of thigh; _21_,
femoral nerve; _22_, saphenous nerve; _23_, branch of _22_ to
sartorius.
_A_, Cut surface of obliquus abdominis externus; _B_, cut surface of
obliquus abdominis internus; _C_, depression due to disappearance of
fat in interval between outer border of psoas major and iliacus;
_D_, thick part of iliac fascia which extends from tendon of psoas
minor to external angle of ilium; _E_, superficial fascia of flank;
_F_, internal inguinal ring; _G_, external inguinal ring; _H_,
patella; _I_, femoral canal; _J_, semimembranosus; _K_, suspensory
ligaments of penis; _L_, cross-section of penis; _M_, stump of
spermatic cord; _N_, ilio-psoas; _O_, tensor fasciæ latæ; _P_, _P_,
extremities of external angle of ilium; _Q_, remains of iliac
fascia; _R_, ilio-lumbar ligament or deep layer of lumbo-dorsal
fascia; _S_, line of attachment of gastro-pancreatic fold; _T_,
tendon of right crus of diaphragm; _U_, right crus; _V_, aorta at
hiatus aorticus; _W_, left crus of diaphragm. The position of the
kidneys is indicated by dotted lines. (After Schmaltz, Atlas d.
Anat. d. Pferdes)
]
2. The =hepatic artery= (A. hepatica) is larger than the gastric. It
passes forward to the right and ventrally on the dorsal surface of the
pancreas, covered by the gastro-pancreatic fold, crossing obliquely
under the vena cava, and reaches the inner border of the portal vein. It
divides into three or four branches which enter the portal fissure of
the liver and ramify within the gland with the portal vein and the
hepatic duct. It gives off the following collateral branches:
(_a_) =Pancreatic branches= (Aa. pancreaticæ) are given off as the
artery crosses the pancreas, in which it is partly embedded.
(_b_) The =pyloric artery= (A. gastrica dextra) arises above the first
curve of the duodenum. It descends to the pylorus, sending branches to
the first part of the duodenum and the pylorus, and anastomoses with the
gastric and right gastro-epiploic arteries. It may arise from the
gastro-duodenal.
(_c_) The =gastro-duodenal artery= (A. gastroduodenalis) passes to the
second curve of the duodenum and divides into the right gastro-epiploic
and the pancreatico-duodenal. The =right gastro-epiploic artery= (A.
gastroepiploica dextra) crosses over the posterior surface of the
duodenum and enters the great omentum, in which it runs to the left,
parallel with the greater curvature of the stomach. It gives branches to
the latter and to the omentum and forms an anastomotic arch with the
left gastro-epiploic artery. The =pancreatico-duodenal artery= (A.
pancreaticoduodenalis) divides into pancreatic and duodenal branches.
The former (Ramus pancreaticus) supplies the middle part of the pancreas
and is often replaced by a number of variable twigs. The duodenal branch
(Ramus duodenalis) passes to the right along the lesser curvature of the
duodenum and anastomoses with the first branch of the anterior
mesenteric artery.
3. The =splenic artery= (A. lienalis) is the largest branch of the
cœliac. It passes to the left (with the large satellite vein) on the
left extremity of the pancreas and across the saccus cæcus of the
stomach. Entering the suspensory ligament of the spleen, it runs in the
hilus of the spleen to the apex, beyond which it is continued as the
left gastro-epiploic. It gives off the following branches:
(_a_) =Pancreatic branches= (Rami pancreatici) to the left extremity of
the pancreas.
(_b_) =Splenic branches= (Rami lienales), which plunge into the
substance of the spleen.
(_c_) =Gastric branches= (Aa. gastricæ breves), which pass in the
gastro-splenic omentum to the greater curvature of the stomach, where
they bifurcate and anastomose with the gastric arteries.
(_d_) The =left gastro-epiploic artery= (A. gastroepiploica sinistra) is
the continuation of the splenic artery. It passes to the right in the
great omentum, parallel with the greater curvature of the stomach, and
anastomoses with the right gastro-epiploic. It gives off branches to the
greater curvature of the stomach, and twigs to the omentum.
II. The =anterior= or =great mesenteric artery= (A. mesenterica
cranialis) arises from the ventral face of the aorta at the first lumbar
vertebra. It is a large unpaired trunk, about an inch (ca. 2 to 3 cm.)
in length, which passes ventrally between the vena cava and the left
adrenal into the root of the great mesentery, when it divides into three
branches—left, right, and anterior.[165]
1. The =left branch= gives off at once about fifteen to twenty =arteries
of the small intestine= (Aa. intestinales).[166] These come off close
together and pass in divergent fashion between the layers of the great
mesentery, each dividing into two branches which anastomose with
adjacent branches to form a series of arches. In the anterior part of
the series secondary arches are formed by the union of branches given
off from the primary set of arches. From the convex side of these arches
terminal branches pass to the wall of the small intestine, in which they
ramify and form a vascular network. They are accompanied by satellite
veins and by nerves and lymph vessels. The first artery anastomoses with
the pancreatico-duodenal, and the last with the ileal branch of the
great mesenteric artery. Branches are supplied to the mesenteric lymph
glands.
2. The =right branch= (A. ileo-cæco-colica) might be regarded as the
continuation of the trunk. It runs downward and a little forward and to
the right and gives off the ileal, the two cæcal, and the ventral colic
arteries.
(1) The =ileal= or =ileo-cæcal artery= (A. ilea) passes in retrograde
fashion along the terminal part of the ileum and unites with the last
branch of the left division.
(2) The =external= or =inferior cæcal artery= (Ramus cæcalis lateralis)
passes between the cæcum and the origin of the colon and runs on the
external muscular band of the cæcum to the apex, where it anastomoses
with the internal artery. Besides numerous collaterals to the cæcum, it
gives off the artery of the arch, which passes along the lesser
curvature of the base of the cæcum and runs on the outer face of the
origin of the great colon.
(3) The =internal= or =superior cæcal artery= (Ramus cæcalis medialis)
passes along the inner band to the apex of the cæcum, where it
anastomoses with the external cæcal artery.
(4) The =ventral=, =right=, or =direct colic artery= (A. colica
ventralis) runs along the opposed surfaces of the ventral (first and
second) parts of the great colon to the pelvic flexure, where it unites
with the dorsal colic artery. It supplies the ventral parts of the great
colon and sends a branch to the base of the cæcum.
3. The =anterior branch= divides after a very short course into the
dorsal and middle colic arteries.
(1) The =dorsal=, =left=, or =retrograde colic artery= (A. colica
dorsalis) is a large vessel which passes along the dorsal (fourth and
third) parts of the great colon to the pelvic flexure, where it joins
the ventral colic artery.
(2) The =middle colic artery= or =first artery of the small colon= (A.
colica media) is a much smaller vessel which passes to the origin of the
small colon, enters the colic mesentery, and forms an arch by joining
the first branch of the posterior mesenteric artery close to the lesser
curvature of the bowel. It sends an anastomotic branch to the dorsal
colic artery.
III. The =renal arteries= (Aa. renales), right and left, are relatively
large vessels which arise from the aorta near the anterior mesenteric.
The =right artery= is the longer of the two. It crosses over the dorsal
surface of the vena cava to the right and somewhat forward. At the hilus
it divides into several (five to eight) branches; some of these enter
the gland at the hilus, while others pass to the ventral surface and
enter there. The =left artery= is short and usually arises a little
further back; it passes directly outward to the kidney and is then
disposed like the right one. Small collateral branches are supplied to
the ureters and the adrenals. The latter also receive small vessels
directly from the aorta. The distribution within the kidney has been
described.
Variations in the renal arteries are frequent. Two or more arteries
may occur on one or both sides. Accessory arteries are more common on
the left side and usually enter the posterior pole of the gland. They
may arise from the aorta, the external iliac, or the circumflex iliac
artery.
IV. The =posterior= or =small mesenteric artery= (A. mesenterica
caudalis) is an unpaired vessel which arises from the ventral face of
the aorta at the fourth lumbar vertebra, _i. e._, about five or six
inches (ca. 12 to 15 cm.) behind the origin of the anterior mesenteric
artery. It is much smaller than the latter and supplies the greater part
of the small colon and rectum. It descends in the colic mesentery and
divides into two branches. The anterior branch (A. colica sinistra)
gives off three or four arteries which divide and form anastomotic
arches close to the bowel. The first arch is formed by union with the
middle colic branch of the anterior mesenteric. The posterior branch or
anterior hæmorrhoidal artery (A. hæmorrhoidalis cranialis) passes
backward in the upper part of the mesentery and the mesorectum and
terminates near the anus by anastomosing with the internal pudic artery.
Three or four of its anterior collateral branches form arches.
V. The =spermatic arteries= (Aa. spermaticæ internæ), right and left,
are long slender arteries which arise from the aorta near the posterior
mesenteric and supply the testicle and epididymis. Each passes backward
in a narrow fold of peritoneum (Plica vasculosa) to the internal
inguinal ring and descends through the inguinal canal to the scrotum. In
the canal and scrotum it pursues a very flexuous course in the anterior
border of the spermatic cord, surrounded by the pampiniform plexus of
veins, and associated closely with the spermatic nerves and lymphatics
and unstriped muscle-fibers. It passes between the epididymis and
testicle, runs in flexuous fashion along the attached border of the
latter, turns around the posterior pole, and runs forward on the free
border to the anterior pole. The largest branches arise from its ventral
part, pass tortuously up either side of the gland embedded in the tunica
albuginea, and give off fine branches to the gland substance. Small
collateral branches are detached to the ureter and the spermatic cord.
The =utero-ovarian arteries= in the female correspond to the preceding
vessels, but are much shorter. Each is placed in the anterior part of
the broad ligament of the uterus and divides into ovarian and uterine
branches. The =ovarian branch= (A. ovarica) pursues a flexuous course to
the ovary, which it supplies. The =uterine branch= (A. uterina
cranialis) passes to the concave border of the cornu of the uterus,
which it supplies, anastomosing with the uterine artery.
VI. The =lumbar arteries= (Aa. lumbales) are in series with the
intercostal arteries and have a similar origin and distribution. There
are usually six pairs of lumbar arteries, of which five arise from the
aorta and the sixth from the internal iliac or the lateral sacral at the
junction of the last lumbar vertebra and the sacrum. Each passes across
the body of a lumbar vertebra to the intertransverse space, gives
branches to the sublumbar muscles, and divides into dorsal and ventral
branches. The =dorsal branch= (Ramus dorsalis), the larger of the two,
passes upward to ramify in the extensor muscles of the spine and the
skin of the loins; it gives off a =spinal branch= (Ramus spinalis) which
comports itself like the corresponding branch of an aortic intercostal
artery. The =ventral branch= (Ramus ventralis) runs outward in the
intertransverse space, passes between the transversus and obliquus
internus abdominis, gives branches to these muscles, and ends in the
obliquus externus, the panniculus, and the skin of the flank.
[Illustration:
FIG. 451.—DISSECTION OF PELVIS, THIGH, AND UPPER PART OF LEG OF HORSE,
INTERNAL VIEW.
_L_, Lumbar vessels; _V.c._, posterior vena cava; _A_, aorta
(termination); _C_, sympathetic trunk; _1_, internal iliac artery,
_2_, lateral sacral artery; _3_, middle coccygeal artery; _4_,
lateral coccygeal artery; _5_, umbilical artery (cut off); _6_,
internal pudic artery; _6′_, vesico-prostatic artery; _7_, obturator
artery; _8_, a. profunda penis (from left obturator); _9_, posterior
gluteal (or ischiatic) vessels; _10_, external iliac artery; _11_,
_11′_, deep femoral artery; _12_, prepubic artery; _13_, branch of
deep femoral artery; _14_, great sciatic nerve; _15_, posterior
gluteal nerve; _16_ (above), internal pudic nerve; _16_ (below near
pelvic outlet), suburethral venous plexus; _17_, sacro-coccygeus
inferior; _18_, coccygeus; _19_, recto-coccygeus; _20_, retractor
ani; _21_, _21′_, two heads of obturator internus; _22_, symphysis
pelvis; _23_, prepubic tendon; _24_, suspensory ligament of penis;
_25_, retractor penis muscle; _26_, bulbo-cavernosus muscle; _27_,
urethra (cross-section); _28_, crus penis (cross-section); _29_,
suspensory ligaments of anus (= upper part of retractor penis
muscle); _30_, anal lymph glands; _31_, tibial nerve. (After
Schmaltz, Atlas d. Anat. d. Pferdes.)
]