comparative Anatomy of the domestic animals intestines

1. Veterinary Anatomy Of The Intestine
By
Prof. Dr. Abdelmohaimen Mostafa Saleh
Professor of Anatomy & Embryology
Assiut University

2.  It extends from stomach
to anus.
It consists of small and
large intestine.
The small intestine includes
duodenum, jejunum and
ileum, It can be divided into
fixed part (duodenum) and
mesenteric part (jejunum
and ileum).
The large intestine consists
of the cecum, colon, rectum
and anal canal.
 Canines have shortest
intestine followed by
equines, pig and ruminants.

3. THE DUODENUM
 It extends from pylorus to
duodenojejunal flexure. It
consists of three parts, three
flexures and three ligaments.
Parts and course:
-Three parts are: cranial part,
descending duodenum and
ascending duodenum.
-Three flexures are :cranial,
caudal, and duodenojejunal.
= Cranial part: passes to the
right on the viseral surface of
the liver forming cranial flexure,
which continues as descending

4.  The cranial part is attached to the liver by the hepatoduodenal
ligament. It presents the major & minor duodenal papillae at
which the major pancreatic duct with the bile duct & the
accessory pancreatic duct open. In horse, the major duodenal
papilla lies inside the ampulla hepatopancreatica.
 The cranial part of duodenum forms a sigmoid loop in horse &
ruminants

5. =Des. Duodenum: runs caudally on
right side in relation to
ascending colon. It forms caudal
flexure behind right kidney and
base of cecum, then it turns to
left and cranially to continue as
ascending duodenum.
=Asc.Duodenoum: runs cranially on
left side in relation to
descending colon, then it turns
ventrally to to join jejunum at
duodenojejunal flexure.
** Cranial part forms sigmoid loop
in horse, ruminants and pig. It
presents major and minor
duodenal papillae at which
pancreatic ducts with bile duct
open.

6. Fixation of duodenum:
1- Mesoduodenum : short fold except dog has relatively
wide one.
2-Hepatoduodenal ligament: attaches cranial part of
duodenum to liver.
3-Duodenocolic ligament: attaches Asc. duodenum to
colon

7. The jejunum
It is the longest part
of small intestine,
extends from
duodenojejunal flexure
to ileum.
Mesentery:
- It is a wide fan-
shaped peritoneal fold.
- it is long and allows
jejunum great range,
especially in dog and

8. Position :
It varies according to species:
 In ruminants and pig: long jejunum,
 found mainly on right half of
 abdominal cavity, surrounding
 coiled ascending colon.
 In dog: jejunal loops occupy
abdominal floor and is covered by
greater omentum.
 In horse: because of great length of
the mesentery, jejunal loops have
great motility and are not confined
to particular area but found mostly
left dorsal quadrate.
 As a result of mobility of jejunal coils
in equines, intestinal colic may
develop.

9. THE ILEUM
• It is the short terminal part of
the small intestine,
• It is suspended by the
mesoileum and is attached to
the cecum by the ileocecal
ligament. It terminates at the
cecocolic junction through the
ileal orifice.
• In horse, the ileal orifice lies in
the cecum on the ileal papilla
which is encircled by a venous
plexus working as ileal
sphincter.3

10. THE CECUM
Definition:
- It initial blind part
of large intestine.
- It varies in size,
shape and position
in different species.
- Vermiform
appendix of cecum
of man is absent in
domestic animals
but presents in
rabbit.

11. Size: depends on species; it is shortest in cat and increasingly
longer in dog, pig, ruminants and horse .
Position: it lies on the right side of abdominal cavity in all animals
except in pig on the left side.
Communcation: in all animals ileum joins cecum at ileocecal
orifice. In addition only in horse cecum joins colon at cecocolic
orifice, but in other animals it continues with colon without
definite line of demarcation.
Shape: Is mostly cylindrical in shape.

12. Muscular bands: present only in pig and horse.
Fixation:
1-Mesocecum: between cecum and dorsal abd.wall.
2-Ileocecal ligament: between cecum and ileum.
3- Cecocolic ligament: between cecum and ascending colon (in horse).

13. Cecum in horse:-
 It has remarkable size and position.
 It occupies large part of right half of abdominal
cavity, from pelvic inlet to intrathoracic part of
abd. cavity.
 It consists of base, body and apex.
 The base: most dorsal part lies in right flank
region. It has dorsal greater and ventral lesser
curvatures. Both ileocecal and cecocolic orifices
open on lesser curvature.
 The body: extends cranioventrally to lie between
right and left ventral colon on abdominal floor.
 The apex: narrowest cranial end, lies in xiphoid
region of abdominal cavity.
 The body has four bands; dorsal, ventral, lateral
and medial. The dorsal band is attached to
ileocecal ligament and lateral one to cecocolic
ligament. The bands make four rows of

14. Cecum of Dog :
 It is irregularly twisted (screw-like),
 directed caudally but its blind end points cranially.
 The cecum of dog lies in the right flank, related
dorsally to the right kidney, ventrally to the jejunum
and ileum, laterally to the descending duodenum and
right lobe of pancreas, caudally it is surrounded by
the caudal flexure of duodenum.
Cecum of Pig :
 The cecum of pig is cylinderical in form,
 it lies against the dorsal and cranial parts of the left
flank extending caudally with its apex on the
abdominal floor reaching the inguinal region, It
 has 3 bands (taeniae) in addition to 3 series of

15. Cecum of Ruminants :
 The cecum of ruminants is cylindrical and
is marked off from the colon only by the
point of termination of ileum,
 It lies against the right flank separated from it
by the grater omentum,
 It extends in a caudo-dorsal direction toward
the pelvic inlet. Its caudal blind end projects
freely from the opening of the supraomental
recess.

16. THE COLON
The colon is divided into
ascending, transverse and
descending colon.
 The ascending colon lies
mainly the in right side, the
transverse colon in the left
side, and descending colon
crosses the median plane
from right to left side.

17. Ascending colon of dog:
The simplest arrangement of colon presents in dog as in man.
 It passes cranially on right side, crosses median plane infront to cranial
mesenteric artery as transverse colon; it then passes caudally on left side
descending colon.

18. ASCENDING COLON OF PIG:
 The ascending colon of pig
consists of only a spiral loop
(ansa spiralis) which consists of
3 close double spiral coils in the
form of a cone.
 These coils are formed of
centripetal coils & centrifugal
coils which are continuous with
each other at the central loop
 The centripetal coils has 2
taeniae which are absent on the
centrifugal ones.

19. ASCENDING COLON OF RUMINANTS:
 It consists of three loops, proximal,
spiral and distal.
 Proximal loop: “S” shape, consists of
three parts; ventral, middle and
dorsal. The ventral one is directed
cranially , the middle part caudally
and the dorsal part continues
cranially by spiral loop.
 Spiral loop: consists of two coils;
centripetal and centrifugal, which
form intestinal disc. Both coils unite at
central flexure.
 Distal loop: consists of two parts;
dorsal and ventral. The dorsal one is
directed caudally and the ventral one
cranially and continued with

20. ASCENDING (GREAT) COLON OF HORSE:
The ascending colon of horse
consists of double U-shaped
loops, one dorsal to the other
with the convex parts toward
the diaphragm. It consists of the
right ventral colon, ventral
diaphragmatic flexure, left
ventral colon, pelvic flexure,
left dorsal colon, dorsal
diaphragmatic flexure and right
dorsal colon.

21.  The right ventral part is attached to the cecum by the cecocolic ligament, passes
cranioventrally.
 It reaches the diaphragm forming the ventral diaphragmatic flexure which is
situated dorsal to the xiphoid cartilage.
 It continues on the left side as the left ventral colon. This part passes on the
abdominal floor till the pelvic inlet where it curves dorsally forming the pelvic
flexure and continues cranialward as the left dorsal colon.
 When the left dorsal colon reaches the diaphragm it forms the dorsal
diaphragmatic flexure from which, the right dorsal colon passes caudally, it
increases in size and is known as the Ampulla coli.
 It then crosses the median plane as the transverse colon. The dorsal colon is
attached to the ventral colon by a very short intercolic ligament which become
wide at the pelvic flexure

22. The ventral parts of ascending colon have 4 bands.
The left dorsal colon and pelvic flexure have 1 band, while right
dorsal colon and dorsal diaphragmatic flexure have 3 bands.
The diameter varies at different parts. The widest part is right
dorsal colon , followed by right and left ventral colon. The pelvic
flexure and the beginning of left dorsal colon have the narrowest
diameter.
Fixation of ascending colon by:
1-Mesocolon. 2-Intercolic lig. 3-Cecocolic lig.

23. Transverse colon
- It begins from ascending colon at right side, then passes to left side
to cranial mesenteric artery to continue as descending colon.
- It has no bands or sacculations.
Descending (small) colon
 It lies in the left dorsal quadrant of body cavity. It passes caudally under
the dorsal abdominal wall with which it is attached by mesocolon and
attached to ascending duodenum by duodenocolic ligament. It enters
pelvic cavity to continue as rectum.
- In ruminants, it presents sigmoid colon.
- In horse, it is long, has two bands. Its coils in horse are easily
from jejunal coils by their diameter, bands and sacculations.

24. RECTUM
The rectum is continuation of descending colon as it enters the
pelvis. It has peritoneal and retroperitoneal parts, and has no
bands or sacculations.
Before ending at short anal canal, the rectum enlarged forming
ampulla recti which is very prominent in horse, but absent in
sheep and goat.
The relation of rectum varies in both sexes. In males, it is related
ventrally to urinary bladder and accessory genital glands, while
in females it is related to uterus and vagina.

25. ANAL CANAL
- It is the short terminal portion of digestive tract. The anus is the
terminal orifice.
- The external and internal sphincter muscles surround anus and keep
opening closed.
- Striated external sphinter M. arises from caudal vertebrae, but internal
sphinter M.is the thickened continuation of circular smooth muscle coat
of rectum.

26. In Dog : It present 3 zones : cutaneous, intermediate &columnar.
The cutaneous zone is continuous with the skin of the anus and
present on each side a small opening for the paraanal sinus (which
contains smelly secretion).
. The intermediate zone is a narrow indistinct area.
. The columnar zone which presents several longitudinal folds or
columns.

27. - There are 3 groups of glands in the anal canal :
circumanal, anal & anal sac glands.
- The circumanal glands are found in the submucosa.
- The anal glands open in the intermediate zone.
- The anal sac glands lie in the wall of the anal sac.
In pig : The anal canal resembles that of dog.
In ruminants : The anal canal has no intermediate zone.
In horse : The anal canal presents an anorectal line at its junction
with the rectum & an anocutaneous line at its junction with the
anus.

28. References: -
- Nickel , Schummer (1995): The Viscera of Domestic Mammals (The Anatomy of the Domestic Animals) .
- Dyce, Sack, andWensing's (2015):Textbook of Veterinary Anatomy
- Klaus Dieter Budras (2011): Bovine Anatomy.
- https://www.google.com.eg/imghp?hl=ar&tab=wi&ogbl