Large intestine of Ox
The large intestine of Ox is extends from the termination of the ileum to the anus and measures 10 to 11.4 m. It is situated between right and left layers of the mesentery in the right dorsal part of the abdominal cavity related on its left to the rumen. Large intestine of Ox is divided into 3 parts – caecum, colon and rectum.
Caecum of Ox
- The caecum is a great cul-de-sac intercalated between the small intestine and colon
- It measures about 75 cm in length and the diameter is about 12 cm
- It is directly continuous in front with the colon, the conventional line of demarcation being the junction of the ileum with the large intestine
- From this junction on the medial face of the caecum at the ventral end of the last rib, the caecum extends backwards and upwards along the right flank and its rounded blind end commonly lies at the pelvic inlet.
Colon of Ox
- The colon is about 10 m. in length
- It has at first a diameter of about 4 inches but later on gradually becomes smaller to about 5 cm
- The greater part of it is arranged in double elliptical coils between the layers of the mesentery
- It begins as direct continuation of the caecum, runs forwards for a short distance, and then turns upwards and backwards in relation to the right flank laterally and caecum ventrally to the caudal part of the sublumbar region
- Here it again turns forwards and runs parallel to the second part of the duodenum as far as second lumbar, turn backward and are continued by the coiled spiral part
- The coils are alternatively centripetal and centrifugal
- It gradually diminishes in its diameter and the terminal part leaves the spiral mass, passes forward to the root of the cranial mesenteric artery and runs backwards dorsal to the third part of the duodenum forming a loop round the artery as it’s axis
- It inclines to the right, related to the ventral face of the right kidney and form an S-shaped curve near the pelvic inlet and joins the ectum
- This part is attached by a short mesocolon to the sublumbar region.
Rectum of Ox
- The rectum is the terminal part of the bowel
- It extends from the pelvic inlet to the anus
- It measures about one foot
- The rectum runs almost straight or slightly oblique course through the pelvic cavity
- It is related dorsally to the roof of the pelvic cavity, ventrally to the bladder, vesiculae seminalis, vas deferentia, ureters, Cowper’s glands and urethra in the male or uterus and vagina in the female.
- The cranial part of rectum, till about the level of the first coccygeal vertebra is covered by peritoneum and is attached by the mesorectum to the roof of the pelvis
- The caudal part is not covered by peritoneum and presents a dilatation, ampulla recti
ANUS
- The anus is the terminal part of the alimentary canal placed below the root of the tail forming a rounded projection with a central depression when contracted
- It is covered externally by thin skin devoid of hair but provided with numerous sweat and sebaceous glands
- It’s lumen, the anal canal is about 5 cm long and is always closed by the contraction of the sphincter muscles and folds of the mucous membrane except during defecation
- The mucous membrane is pale, glandless and covered with thick squamous stratified epithelium
- The muscles of the anus are,
- The sphincter ani internus is the terminal thickening of the circular coat of the bowel and the sphincter ani externus is a broad ring of striped muscle outside the preceding
- The action of both is to close the anus
- The retractor ani is flat striped muscle, which lies between the rectum and the sacro sciatic ligament ending below the preceding
- It reduces the partial prolapse, which the anus undergoes during defecation
- The suspensory ligament of the anus is a band of plain muscle arising from the first coccygeal vertebra, passing down under the retractor, unites with its fellow below the anus
- In the male it is continued as retractor penis muscle. In the female it blends with the constrictor vulvae
- Mucous membrane presents intestinal gland but no villi: solitary glands are numerous.
