Accessory organs :
1- Liver
2- Pancreas
3- Gall bladder
Liver
Is the largest gland of the body, which lies in the intrathoracic portion of the abdominal cavity.
Functions :-
1- Metabolism of protein, carbohydrate and fats.
2- Detoxification of drugs and toxins.
3- Plasma protein production.
4- Formation and secretion of bile.
5- Hemopoiesis in the embryo.
Color of liver in different species :
In the ox, sheep and horse:
Is reddish brown, but becomes brown when bled out.
In the dog and cat:
The liver is reddish brown.
Suckling and pregnant animals:
They have a yellowish brown liver, because of the presence of fats.
In starving animals:
They have a dark reddish brown liver.
Shape of the liver :
1- Diaphragmatic surface :
The convex surface that lies against the diaphragm.
2- Visceral surface :
It faces caudally and is related to the stomach, duodenum, colon, jejunum, an to the right kidney.
3- Rounded (dorsal) borders :
Thick border that lies between the esophageal notch (impression) and the renal impression, it is crossed by the esophagus and caudal vena cava.
4- Sharp border :
Thin border that is divided in to left ventral and right ventral borders.
5- Impression :
Some of organs produce impressions such as esophageal, gastric, duodenal,….etc.
Position of liver varies with species:
In dog :
The liver located equally on each side of the median plane.
In the ruminants :
Is displaced entirely to the right of the abdominal cavity, the round border lies in the median plane and the sharp border is directed to the right.
In horse :
The liver is placed obliquely, its rounded border crosses the median plane and faces dorsolaterally and to the left, while its sharp border is directed ventrolaterally and to the right.
Lobation of the liver
The liver can divided to its lobes according to the following base:
1- Imaginary line on the visceral surface from the esophageal notch to the notch for the round ligaments separates the left lobe from the rest of the liver. The left lobe may be subdivided in to left medial and left lateral lobes.
2- Another line from the caudal vena cava to the fossa for the gall bladder, separate the right lobe from the rest of the liver. The right lobe may be subdivided in to right medial and right lateral lobes.
The region between these lines divided the liver in to:
A- Quadrate lobe :
It lies ventral to the hepatic porta.
B- Caudate lobe :
It lies dorsal to the porta and has caudate and papillary processes.
.
Note:
Hepatic porta :
Is the depression on the visceral surface of the liver through which the portal vein, hepatic artery and hepatic ducts are passes.
Species differences of liver lobulations:
In carnivores:
liver consist of left lobe (lateral and medial), right lobe (medial and lateral), quadrate lobe and caudate lobe with a caudate process on the right and papillary process on the left.
In ruminant:
The liver consists of un divided left and right lobes, quadrate lobe, caudate lobe with a small papillary process and large caudate process.
Liver of a sheep: (1) right lobe, (2) left lobe, (3) caudate lobe, (4) quadrate lobe, (5) hepatic artery and portal vein, (6) hepatic lymph nodes, (7) gall bladder
In horse:
The left lobe is subdivided in to (lateral and medial), while right lobe is undivided, the quadrate lobe have several notches and is separated from the right lobe by a deep interlobar notch, the caudate lobe has caudate process but no papillary process.
Left lateral lobe
Right lobe
Quadrate lobe
Left medial lobe
Caudal vena cava
Hepatic veins
Coronary ligament
Falciform ligament
R. Triangular ligament
Caudate lobe (caudate process)
Blood supply of the liver:
1- Functional blood :
It comes to the liver via the portal system (portal vein), caring nutrient absorbed from the intestine.
Portal vein:
the large vein caring all the blood from the abdominal viscera to the liver.
2- Nutrient blood (oxygenated) :
It comes to the liver via hepatic artery to keep the hepatocytes alive.
Blood supply of the liver:
Note:
Sinusoids:
are small, irregular, vascular spaces which are closely surrounded by the parenchyma of the organ. They replace capillaries in certain organs, like liver, spleen, bone marrow, suprarenal glands, parathyroid glands, carotid body, etc.
Bile passages :
1- Bile ductules:
They unite to form hepatic ducts.
2- Hepatic duct:
Three to five duct that leave the porta and form common hepatic duct.
3- Cystic duct:
It connects the gall bladder with the common hepatic duct.
4- Bile duct:
The duct formed by the junction between the common hepatic duct and cystic duct.
Species differences:
In ruminants:
The common hepatic duct unit with the cystic duct to form the bile duct.
In horse:
The gall bladder and its cystic duct are absent, therefore the wider terminal portion of the common hepatic duct is called the bile duct.
In dog:
Three to five common hepatic ducts empty separately in to the cystic duct, which becomes the bile duct.
Gall bladder
1_The sac storing and concentrating bile.
2_ It lies in the fossa on the visceral surface of the liver between the quadrate and right medial lobes.
3_ The bile aids in digestion and lubrication of food.
Ligaments of the liver
1- Coronary ligament :
The reflection of the peritoneum from the diaphragmatic surface of the liver on to the diaphragm. It forms circular area of reflection around the caudal vena cava.
2- Right triangular ligament :
It connects the dorsal part of the right lateral lobe to the curs of the diaphragm.
3- Left triangular ligament :
It connect the dorsal part of the left lateral lobe to the left curs of the diaphragm.
4- Falciform ligament :
It connects the ventral part of the liver to the sternal part of the diaphragm.
5- Round ligament :
It occurs in the free border of the falciform ligament, it is a remnant of the umbilical vein of the fetus.
Pancreas
Is the gland composed of two lobes (right and left) joined by a body, that located entirely in the right of the median plane on the visceral surface of the liver.
Species differences :
In carnivores :
It forms U- shaped, consisting of centrally place of body and right and left lobes.
In ruminants :
The body is small with wide left lobe and long right lobe, the body of the pancreas in carnivores and ruminants is notched.
Right lobe
Left lobe
Body
Sheep pancreas
In horse :
The body is large with long left lobe and short right lobe, the body is perforated by the portal vein.
A- left lobe.
B- right lobe.
G- body.
F- portal vein.
Horse pancreas
Ducts of the pancreas :
1- Pancreatic duct :
The tube opening with the bile duct on the major duodenal papillae.
2- Accessory pancreatic duct :
The tube opening in to the duodenum on the minor duodenal papillae.
(Accessory pancreatic duct)
Species differences :
Sheep and goat | Ox | Horse | Dog | |
+ | - | + | + | Pancreatic duct |
- | + | + | + | Accessory pancreatic duct |
+ present
- Absent
Note :
Abdominal cavity:
Peritoneum:
Is the serosa membrane moist by the peritoneal fluid, that lined the abdominal cavity and part of pelvic cavity, it is composed of two layer (parietal and visceral layers).
Connecting peritoneum (folds) are :
1- Mesentry :
Is the fold of peritoneum formed two layers which is suspended organs. Examples: colon (mesocolon), ovary (mesoovary). The mesentry contain blood vessels and nerve fibers.
2- Omentum :
Is a fold of peritoneum formed from two layers attached the stomach these are (lesser and greater omentum).
3- Ligaments :
Is a fold of peritoneum formed from two layers pass between viscera or between viscera and the abdominal wall.