Download 2-thoracic part

Alimentary canal
Is a tube which extends from pharynx to the anus, consist of following segments:
A-esophagus. B-stomach.
C-small intestine. D-large intestine.
The esophagus:
It is a musculo-membrance tube extending from the pharynx to the stomach. It is divided
according their location into:
1-cervical part: is the long part it is about six inches longer then the thoracic part.
2-thoracic part.
3-abdominal part: is short part, it is about one inch.
In horse the lumen of esophagus is closed by deep longitudinal folds when it is empty and the long
about 125-150cm.with 2.25 in diameter.
In ox it is shorter about 90-105 cm. with large diameter about 5.7.
In sheep: long about 40-50cm. with 3cm. in diameter.
Structure of esophagus: consist of:
1-mucous membrane lining the esophagus is stratified squamous epithelial tissue.
2-sub mucosa consists of connective tissue formed from fibers and containing mucous gland to
lubrication.
3-muscular layer: in horse only the striated muscle formed about 2/3 cranially in born along
esophagus while smooth muscle mainly last about ½.
4-adventitia.
Course of esophagus
1-cervical part: it is being dorsal to larynx (brachia) and at the level of 4 th cervical; it is become
lateral to it. It is in near to entrance of thoracic, it is passes left side of trachea because of the
esophagus near to skin in this area, so you can see the passage of food (boluses) or water or bubbles
of air and can be seen the stomach tube pipated, here as it passed through the esophagus. In region
more suitable to reach the esophagus for surgery.
Relations of esophagus in the cervical part:
1-cartilage of larynx. 2-common carotid artery 3-jugular vein
4-tracheal duct and cervical lymph nodes
5-vagosympathetic trunk.
6-caudal laryngeal nerve
7-in small animals (thymus gland)
2-thoracic part: begin at the thoracic inlet and through left side of trachea and its run caudally in
dorsal medistinum and passed upper of trachea bifurcation that cross the right side of aortic arch
caudal to the base of heart, the esophagus lie between the lung ventral to the thoracic aorta and dorsal
to the vagus nerve, finally it passes through the esophageal hiatus of the diaphragm.
3-abdominal part: is short and attached with stomach by the cardiostium.
Comparative
1- In the carnivores began at caudal border of the cricoids cartilage opposite the axis in dog, but in
cat opposite the 3cervical vertebrae.
2-cranial part esophagus in ox lies between longus coli muscle and trachea in caudal half of the neck
deviates to the left and lies against the lateral surface of trachea.
Blood supply of esophagus
1-cervical part: supply by branches of right and left common carotid artery.
2-esophageal artery: branches of esophageal trunk.
3-left gastric artery
Nerve supply is derived from vagus and sympathetic trunk, intramuscular ganglia of mesenteric
plexus are found between internal and external muscle layers.
In cattle: the esophagus obstructed in cattle and need the knowledge of three flexures of the
esophagus.
1-at junction of the head and neck: it is convex dorsally.
2-at the thoracic inlet, concave dorsally.
3-in the middle of the thoracic cavity where the esophagus passes over the tracheal bifurcation and
the base of the heart (it is permanent bend and is convex dorsally).
The stomach (gaster)
The stomach (gaster): is the large dilation of the alimentary canal caudal to the diaphragm which
located between the esophagus and the small intestine. It stores food temporarily and digests it
chemically.
Classification of the stomach:
1-According to the number of cavities:
A-monolocular stomach: it is contains one cavity like in dog, horse, pig and all animals except
ruminants.
B-multilocular stomach: it is contain many cavities like in ruminants (ox, goats and sheep).
2-according to the mucous membrane lining (inner lining):
A-simple stomach: it lines by one kind of mucous membrane (glandular mucosa), covered by simple
columnar epithelium like dog, cat and man.
B-compound stomach: it lines by glandular and non glandular mucosa like in ruminants, pig and
horse.
♣ The part which lines by non glandular mucous membrane called forstomach or proventriculus
which differ in size from small zone around cardia in the pig to large part in horse or three large
cavities in ruminants called the rumen, reticulum and omasum
The glandular part in the ruminants is a separate cavity the abomasums.
Stomach of horse:
1-it is monolocular compound stomach.
2-it is sharply curved, J-shaped sac, the right
part being very much shorter than the left.
The convexity is directed ventrally. It has two
surface, two curvature and two extremities.
1-the parietal surface: it is convex and
directed cranial, dorsal and to wards the left.
It lies against the diaphragm and liver.
2-the visceral surface: also convex, it is
related to the terminal part of the large colon,
pancreas, small intestine and the greater
omentum.
♣ The border between two surfaces are
termed the curvature.
♣ The lesser curvature is very short extending
from the termination of esophagus to the
junction with small intestine.
♣ The greater curvature is very thick,
extending from the cardiac; its first directed
dorsally and curves over the left extremity.
It is then descends, passes to the right crosses the median plane and curves dorsal to end at the
pylorus.
♣ The left extremity: has the form of round cul-de-sac termed the saccus caecus ventriculi. It lies
ventral to the left crus of the diaphragm and it is related to the pancreas and the termination of the
great colon caudally and the base of spleen laterally.
♣ The mucous coat is clearly divided into two parts:
1-non glandular part: lines the greater parts of the left sac resemble to esophagus mucous
membrane and it is termed the proventicular part (esophageal region). It is white in color.
2-glandular part: it contains the gastric glands and sub divided into three zones according to the
types of glands which it contains:
A-cardiac gland region: narrow a zone along the greater curvature has yellowish gray color and
contains cardiac gland.
B-fundus gland region: next to cardiac gland region is a large area which has a mottled, a reddish
brown color and contains fundus gland.
C-pyloric gland region: is much smaller and has a reddish gray or yellowish gray color and contains
pyloric glands. It is continuous with the duodenum, the junction between it and duodenum indicated
by a marked constriction.
♣ There are two orifices:
A-cardiac orifice between the stomach and esophagus, in this opening there are numerous folds
which occlude the opening. It is terminated by abruptly, forming an irregular sinus raised edge
termed margoplicatus which separate the cardiac region from the non glandular region.
B-pyloric orifice: called pylorus, is the opening into the intestine, is indicated externally by distinct
constriction, internally it presents a circular ridge caused by a ring of muscular tissue (pyloric