Liver, pancreas, spleen

• Terms to know


  • hilus/porta
  • Fossa
  • falciform ligament
  • diaphragmatic surface
  • visceral surface
  • esophageal notch
  • round ligament
  • quadrate lobe
  • caudate lobe
  • papillary process
  • papillary process
  • hepatoduodenal ligament
  • portal vein
  • functional blood supply
  • nutritional blood supply
  • hepatic duct
  • gall bladder
  • reticuloendothelial system
  • gastrosplenic ligament
• Liver


  • Largest gland
  • Secretion of bile (esp. for fat digestion)
  • Hemopoietic centers - embryonic life
  • Storage of glycogen, fat and small amount of protein
  • Converts end products of protein catabolism to urea and uric acid
  • Removed waste products
  • Detoxify harmful substances from blood
• Liver


  • Color: reddish brown, brown when bled out, yellowish brown in suckling and pregnant animals, and those on fattening diet, dark reddish brown in emaciated or starving animals
  • Serosa (serosal membrane/peritoneum) gives smooth and glossy appearance
  • Great number of small lobules (visible in pig)
• Liver of Pig


  • Firm, elastic and friable
  • Lies in intrathoracic portion of abdominal cavity, behind diaphragm
  • Diaphragmatic surface -convex
  • Visceral surface -caudally
  • In ruminant – entirely in right abdomen
  • In horses – placed obliquely

  
• Lobes of the liver


  • Left lobe (subdivided into left medial & left lateral lobes)
  • Right lobe (subdivided into right medial & right lateral lobes)
  • Caudate lobe (dorsal to the porta, has caudate and papillary processes)
  • Dog = 6 lobes
  • Pig = 5 lobes
  • Ruminant = 4 lobes
  • Horse = 5 lobes
  • Carnivores - 6 lobes
• Carnivore liver lobes


  • left lateral lobe
  • left medial lobe
  • right lateral lobe
  • right medial lobe
  • quadrate lobe
  • caudate lobe - caudate process (right) & papillary process (left)

  
• Pig liver


  • 6 lobes (like carnivores, but no papillary process)
  • Quadrate lobe -small and short
• Ruminant liver


  • Compact organ, not divided by interlobar notches
  • Right lobe (undivided)
  • Left lobe (undivided)
  • Quadrate lobe
  • Caudate lobe -small papillary & large caudate process

  
• Horse liver


  • 5 lobes
  • Left lateral lobe
  • Left medial lobe
  • Right lobe (undivided)
  • Quadrate lobe
  • Caudate lobe (no papillary process)

  
• All animals have gall bladder (exc. horse, deer & some birds)
• Horse liver


  • No gall bladder & cystic duct
  • Wider, terminal portion of the common hepatic duct (usually called bile duct)

  
• Blood supply to liver

  • Functional blood supply: portal vein
  • Nutritional blood supply: hepatic artery, a branch of celiac artery
  • Hepatic veins open directly into caudal vena cava
  • Innervation -branches of the vagus & sympathetic nerves
• Bile passages


  • Left hepatic duct
  • Right hepatic duct
  • Common hepatic duct
  • Cyctic duct (gall bladder)
  • Bile duct
  • Major duodenal papilla (duodenum)
• Gall bladder


  • Pear-shape, lies in a fossa on visceral surface
  • Stores bile temporarily
  • Discharges into duodenum when food enters it
  • Protrudes from the border of liver in ruminants
  • Bile enters and leaves gall bladder through cystic duct
  • Lies between quadrate and right medial lobes
  • Partly attached, partly free
  • In some dogs (& pigs) -deeply embedded
• Pancreas


  • An extension of glandular mucosa of duodenum, remain connected by secretory ducts
  • Yellowish and soft
  • Body – lies against cranial part of duodenum
  • Left lobe – continues from body to the left
  • Right lobe - continues from body to the right
  • In carnivores -form U-shape loop
  • Function - produces enzymes to assist in food digestion and hormones such as insulin, which regulates blood sugar or glucose metabolism
  • Pancreatic duct opens into duodenum on the duodenal papilla
  • Horse, small ruminant and cats - pancreatic duct opens with bile duct on major duodenal papilla
  • Accessory pancreatic duct opens on minor duodenal medulla
  • In pig and ox -only accessory pancreatic duct
• Pancreas


  • Consists of lobules loosely united by small amounts of interlobular connective tissue
  • Pale red (fresh)
  • Rapidly decomposes (death)
  • Exocrine and endocrine gland
• Blood supply to pancreas

  • Cranial (from celiac a.) & caudal (from cranial mesentery a.) pancreaticoduodenal arteries
  • Veins drain to the portal vein
• Spleen


  • During embryonic life - production of erythrocyte
  • In adult - production of lymphocyte, later, destruction of erythrocytes, storage of ion, store blood, defense mechanism of the body
• Spleen


  • Lies against the left abdominal wall, and usually covered by ribs
  • Dog, pig and horse - depend on the fullness of the stomach (eg, in dog, it is displaced caudally to the flank when the stomach is greatly distended)
  • Laterally flattened, elongated organ
  • Parietal and visceral surfaces
  • Cranial and caudal borders
  • Dorsal and ventral extremities
  • Carnivores - ventral extremity wider than dorsal one
  • Pig – uniform width, triangular in cross section
  • Ox – long oval
  • Small ruminants – compact, triangular in sheep, rectangular in goat
  • Horse – comma shape (wide dorsally & pointed ventrally)
• Blood supply to spleen

  • From splenic artery, a branch of celiac artery
  • Splenic vein – carries blood from spleen to liver
• Omenta and mesenteries

  • Greater omentum
  • Lesser omentum
  • Mesenteries
• Greater omentum

  • Serosal fold of superficial and deep wall
  • Netlike appearance due to many blood vessels and lymphatics embedded in strands fat
  • Carnivores – lies between intestines and ventral abdominal wall, free edge lies just cranial to pelvic inlet
  • Pig = carnivores, but does not extend as far caudally
  • Horse – the superficial and deep walls adhere to each other, may reach inguinal area, and may be visible during castration
• Functions of omenta and mesenteries

  • Carry blood vessels (celiac artery and branches of portal vein), lymphatics and nerves to organs
  • Capable to produce and absorb abdominal fluids
  • Can store large amount of fat (except in horse)
  • Regulating blood pressure in abdominal cavity
  • Capable of closing the breaks in abdominal wall
• Lesser omentum

  A serosal sheet passing from lesser curvature of stomach and cranial part of duodenum to visceral surface of liver
• Mesenteries

  • Serosal folds that suspend intestinal tract from roof of abdominal cavity
  • Fat is embedded in some parts of mesenteries along blood and lymphatic vessels
• Cecum of horse

  • Occupies large part of right half of abdominal cavity
  • About 1 m long, has capacity of 16-68 liters
  • Base - most dorsal part
  • Greater curvature – dorsally
  • Lesser curvature - ventrally
  • Longitudinal bands (teniae) on dorsal, ventral, lateral and medial surfaces
  • Ileocecal fold - along dorsal band
  • Cecocolic fold - along lateral band
  • Cecal vessels and lymph nodes - along medial and lateral bands
  • Ileal opening – at base of cecum
  • Cecocolic opening - connect base of cecum with ascending colon