_Oes._, Œsophagus; _Ret._, reticulum; _b.s._, anterior blind sac;
_b.s.′_, _b.s.″_, posterior blind sacs of rumen; _O_, ovary. The
left kidney, concealed by the dorsal sac of the rumen, is indicated
by dotted line. The median line of the diaphragm is dotted.
]
The =rumen= occupies almost all of the left half of the abdominal
cavity, and extends considerably over the median plane ventrally and in
its middle. It is somewhat compressed laterally, and may be described as
having two surfaces, two curvatures or borders, and two extremities. The
=parietal= (or left) =surface= (Facies parietalis) is convex and is
related to the diaphragm, spleen, and the left wall of the abdomen. It
extends from the lower part of the seventh intercostal space almost to
the pelvis. The =visceral= (or right) =surface= (Facies visceralis) is
somewhat irregular, and is related chiefly to the omasum and abomasum,
the intestine, the liver, pancreas, kidneys, the uterus in the female,
and the posterior aorta and vena cava. The =dorsal curvature= (Curvatura
dorsalis) is convex, following the curve formed by the diaphragm and
sublumbar muscles. It is firmly attached to the left portion of the
crura of the diaphragm and the sublumbar muscles by peritoneum and
connective tissue. The =ventral curvature= is also convex and lies on
the floor of the abdomen. The surfaces are marked by the right and left
=longitudinal furrows= (Sulci longitudinales), which indicate externally
the division of the rumen into dorsal and ventral sacs.[108] The
=reticular= (or anterior) =extremity= (Extremitas reticularis) is
divided ventrally by a transverse groove (Sulcus ruminis cranialis) into
two sacs. The dorsal sac is the longer of the two, and curves ventrally
over the round, blind end of the ventral sac. The former only is
continuous with the reticulum, a ventral groove (Sulcus
rumino-reticularis) being the only external line of demarcation.
Dorsally no natural separation exists, the rumen and reticulum together
forming a dome-like vestibule (Atrium ventriculi) on which the œsophagus
terminates. The =pelvic= (or posterior) =extremity= (Extremitas pelvina)
extends nearly to the pubis, and is related to the intestine and
bladder, and the uterus in the cow. It is divided into =dorsal= and
=ventral blind sacs= (Saccus cæcus caudalis dorsalis, ventralis) by a
deep transverse groove (Sulcus ruminis caudalis) in which the
longitudinal furrows terminate. The blind sacs are marked off from the
remainder of the rumen by the =dorsal= and =ventral coronary grooves=
(Sulcus coronarius dorsalis, ventralis).
The left longitudinal groove (Sulcus longitudinalis sinister) begins
at the anterior transverse groove, passes somewhat dorsally and
backward and divides into two grooves. The ventral one is the chief
groove and passes backward to terminate in the angle of union of the
posterior blind sacs. The dorsal (accessory) groove curves dorsally
and then backward to terminate in the dorsal coronary sulcus. On the
right surface there are two longitudinal grooves. The dorsal one is
the chief sulcus (Sulcus longitudinalis dexter). It extends in a
curved direction (the convexity being dorsal) and is continuous with
the left longitudinal groove by means of the grooves between the
dorsal and ventral blind sacs at each end. The ventral groove (Sulcus
accessorius) curves somewhat ventrally and backward to rejoin the
chief sulcus between the posterior blind sacs.
The =reticulum= is the smallest of the four divisions in the ox. It is
also the most anterior, and lies on the concave surface of the
diaphragm, so that the median plane divides it into two nearly equal
portions. It is somewhat pyriform, but much compressed from before
backward. The =parietal= or =phrenic surface= (Facies diaphragmatica) is
convex and lies against the diaphragm and liver.[109] The =ruminal= (or
posterior) =surface= (Facies ruminalis) is flattened by the pressure of
the other three compartments; it ends dorsally by joining the wall of
the rumen, the concave line of junction forming, in the interior of the
stomach, the lower margin of the large rumino-reticular orifice. The
=omasal= (or right) =surface= is narrow and concave, and is connected
with the omasum. The =dorsal curvature= by its left portion joins the
rumen to form the atrium, and by its right portion touches the liver.
The =ventral curvature= lies on the sternal portion of the diaphragm,
opposite the sixth and seventh ribs. The =right extremity= forms a
rounded cul-de-sac, which is in contact with the liver, omasum, and
abomasum.
The =omasum= (Fig. 294) is ellipsoidal in form and somewhat compressed
laterally. It is very clearly marked off from the other divisions. It is
situated almost entirely to the right of the median plane, opposite the
seventh to the eleventh ribs. The =parietal= (right) =surface= (Facies
dextra) lies against the diaphragm, liver, and lateral wall of the
abdomen. The contact with the latter extends over a small area only
(ventral part of seventh to ninth intercostal spaces). The =visceral=
(left) =surface= (Facies sinistra) is in contact with the rumen and
reticulum. The =dorsal= (greater) =curvature= is convex, and is related
to the diaphragm, liver, and vena cava. The =ventral= (lesser)
=curvature= is concave, and rests on the abomasum chiefly, the junction
with the latter appearing as a constriction near the middle of the
curvature; at its anterior part there is a =neck= (Collum omasi) which
is the connection with the reticulum.
The =abomasum= (Fig. 294) is an elongated pyriform or flask-shaped sac,
which lies for the most part on the abdominal floor, to the right of the
ventral sac of the rumen. Its narrow posterior part is strongly curved,
the concavity being dorsal. The =parietal= (right) =surface= lies
against the abdominal wall from the seventh to the twelfth intercostal
space. The =visceral= (left) =surface= is related chiefly to the ventral
sac of the rumen. The =dorsal= (lesser) =curvature= is concave, and is
in contact with the omasum; the junction of the two sacs is indicated by
a constriction about four or five inches (ca. 10 to 12 cm.) from the
anterior extremity of the abomasum. The =ventral= (greater) =curvature=
is convex, and rests on the abdominal wall from the xiphoid cartilage to
the ventral part of the last (right) intercostal space. The =anterior
extremity= forms a rounded blind sac which lies against the reticulum.
The =posterior= (or pyloric) =extremity= is much smaller and bends
upward and forward to join the duodenum. About six to eight inches (ca.
15 to 20 cm.) from the pylorus is a constriction which marks off the
pyloric portion from the fundus.
The rumen is attached by peritoneum and connective tissue to the crura
of the diaphragm and left psoas muscles, from the hiatus œsophageus
backward to about the third or fourth lumbar vertebra.
The lesser omentum attaches the right face of the omasum and the pyloric
portion of the abomasum to the visceral surface of the liver.
A small area of the anterior part of the right face of the rumen is
adherent to the adjacent surface of the abomasum. The greater part of
the ventral curvature of the omasum is attached by connective tissue to
the dorsal face of the abomasum.
(Adhesion of the reticulum to the diaphragm is frequently present, but
is pathological; the same is true in regard to adhesion to the liver.)