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The large glands of the digestive tract

   1. Intestinal glands

         --- A part of enzymes for digestion

   2. Glands attached to the intestine

         --- Most of enzymes for digestion
 

         --- Liver\ Pancreas

               --- Derivatives of the digestive tract with the swimbladder

1. Digestive glands 消化腺

  1) Liver 肝臟

     --- The largest accumulation of entodermal tissue in the body

                --- Primarily of entodermal tissue
 

                    Added by the mesodermal component

                     --- a. Capsule (Mesothelium) with reticular connective tissue

                          b. Blood vessels

            # Blood of intestine and spleen enters into liver

     (1) Location

           --- The largest gland located anteriorly within the pleuroperitoneal cavity
 

           --- Contacting with stomach

                 --- Associated with peritoneum, intestine, spleen, swimbladder and pancreas

     (2) Lobulation of liver

          a. Unilobe or no lobulation
 

               --- Cyclostomi

                    Ayu\ Rainbow trout\ Eel\ Pike (Esox)\Mackerel\ Swellfish

          b. 2 or 3 lobes
 

               --- Chondrichthyes and many teleosts(2)

                    Tuna, codfish and flounder(3)

          
          c. Polylobes
               --- Polylobes in Mebaru, Urumeiwashi

               --- Irregular lobes in Cyprinus carpio

          d. Number of hepatic lobes of farmed teleosts

     (3) Color of liver

           --- Generally, reddish brown
                 --- Wild fish
 

           --- Variation in color

                 --- Individual and species differences
 

                 --- From yellow to dark brown to gray

                       --- Diseased state

                            --- Dark reddish

                       --- High-fat foods

                            --- Tinge of yellow
                            --- Barometer of nutrition and health

     (4) Size of liver

           --- Associated with species, foods, season or sex
 

           --- Hepatosomatic index

                 --- Weight of liver/ Body weight X 100

                       --- Chondrichthyes 10 - 20%
                              --- 33% in Yumejame (a deepsea species)
 

                            Osteichthyes    1 - 2%
                              --- Exception
                                     --- 4 - 11% in Crucian carp, Samma, Umazurahagi, Kusahugu
                                     --- ? in Cod
 

                            Man 2%/ Dog 3%

                       --- Male < Female (x1.5 - x2.0) in fish

                ---  Indices in farmed species
                       --- Below 1% or above 2%
                       --- How different between sex ?

     (5)  Blood supply and distribution within the organ
         
                --- Dual supply

                --- Several parts of digestive tube
                       --- Portal vein
                              <--- Spleen                            

                    Dorsal artery
                       --- Hepatic artery
                                              ============> Interlobular vein and artery
                                                                            --- Sinusoidal capillary within lobule
                                                                                  --- Central vein in lobular center
                                                                                         --- Intercalated vein
                                                                                                --- Hepatic vein
                                                                                                       ---> Heart    

     --- Liver in the carp

            --- 2 main lobes
                   --- Longitudinally  separated by sagittal septum(Septum sagittale)

                           --- Sagitall septum
                                  --- A part of dorsal mesentry

                                  --- Passing-through of vessels entering into liver
 

                   --- Between 2 lobes
                           --- The intestine originates

                   --- Middle furrow or Sulcus medianus hepatis

                          --- Considered as boundary line separating of 2 main lobes
 

                          --- Terminated in the liver center usually

                                --- Occasionally passing through the liver center

                                      ---> 2 separate livers with paired structure

                   --- Intestinal furrow or sulci intestinales
 

         (1) Right lobe (lobus principalis dexter)

              --- Gall bladder lobe
                    --- Surrounding the gall bladder

                          --- Fovea vesicae biliaris on lobe surface

                               --- A space in which the gall-bladder is located

              --- Gall bladder lobe

                    --- a. Ventrolateral lobe(Lobus ventrolateralis)
 

                         b. Caudal lobe(Lobus caudalis)

                             --- Rudimentary

         (2) Left lobe (lobus principalis sinister)

              --- Spleen lobe
                    --- Surrounding the spleen

                          --- Impressio lienalis on lobe surface

              --- Tied-off from the rest of that organ by intestinal loops

                    --- Formation of secondary lobe

                           a. Angular part (Pars angularis)

                                --- Between the 5th and 8th loops and ventral wall
 

                                --- The appearance of a 7

                                      --- Cauda partis angularis

                            b. Islet part (Pars insularis)

                                --- Surrounded by the 5th loop 

 2. Gall bladder 膽囊

     --- No gall bladder in dolphins
          No gall bladder in Syumokuzame, Nokogiriei and one species of Houbou

    (1) Location

          --- a. Many of chondrichthyes

                   --- Embedded within liver

               b. Most of osteichthyes

                   --- Between liver and intestine

          --- Opening at the beginning of intestine

     (2) Shape and color of the bladder

          --- Spherical

                --- Flounder\ Swellfish\ Kiankou

               Ovoid

                --- Mackerel\ Tuna\ Japanese horse mackerel

               Slender cord-shaped
                --- Mackerel\ Katsuo\ Azi\ Mutsu

          --- Yellowish brown or greenish
                --- Greenish color suggesting the presence of biliverdin
                      --- Associated with green liver disease in mullet, parrot fish and red seabream

                --- Importance of bile color among species ?

     (3) Function

           --- a. Emulsification of fat
 

               b. Digestion of proteins

                    --- Precipitation of certain proteins
 

 3. Pancreas 膵臟

     --- The same origin as the liver
 

     --- a. Compact pancreas(Pancreas compactum)

             --- Compact only in the elasmobranchii\ dipnoi\ some siluroidei

         b. Diffuse pancreas or disseminated pancreas(Pancreas difussum or disseminatum)

             --- Diffusely distributed organ

                  Generally along the portal veins(vv. portae)

             --- Appearance at the beginning of portal vein from the intestinal serosa

                   ---> Sometimes penetrated into the liver

                          --- Hepatopancreas

     --- Sufficiently well-developed mesentry between the intestine and liver

           ---> Concentrated between the epithelial layers of the mesentry

                  --- Then, appearing a number of thickenings of the intestinal wall

                             <--- Primary anlagen

                                      <--- Entodermal origin

                       |

                       +-- Unite

                             ---> 3 secondary anlagens

                                    --- Fusion

                                          ---> Sac-shaped\ externally prominent structures

                                                 Located between the stomach and midgut

     --- 3 secondary anlagens

           --- a. 2 ventral small ones

                    --- Near the liver anlage

                          ---> Contact with the duct of the liver

                    --- Left\ right sides of the intestine

                          ---> Exocrine pancreatic tissue

               b. A dorsal large one

                   --- Placed on median plane
 

                   --- 3 clusters of primary anlagen

                         a. A single median cluster

                              ---> Endocrine portion

                         b. One on each side of the body (2 lateral clusters)

                              ---> Exocrine portion

    (1) Location

 
          --- As follicles between esophagus and blind sac-like projection in end of midgut in cyclostomi

          --- Separated tubular compact organ with 1 or 2 lobes attached around border between
               stomach and intestine

          --- Compact organ on dorsal wall of digestive tibue in dipnoi and on dorsal side of spiral intestine
               in Siragansu

          --- Diffuse organ in many of teleosts which is dificult to discern with naked eyes.
                
         a. Individual organ

              --- Anguilla\ Silurodei(Sheatfish)\ Pike(Esox)

              --- Easily discernible pancreas

         b. Around liver

              --- Crucian carp\ Japanese horse mackerel

         c. Hepatopancreas

              --- Carp\ Flatfish\ Tilapia\ Sea bass\ Red sea bream

         d. On the pyloric ceca

              --- Salmon\ Trout

              --- Within the connective tissue

         e. Around digestive tube

              --- Mugill

              --- May be surrounded by fat tissue within the mesentry

         f. Splenopancreas or around spleen

              --- Loach\ Angel fish

         g. Around Islet of Langerhans

              --- Mackerel

    (2) Shape of compact pancreas

          --- Chondrichthyes
                --- Variation with species

                ---  2 lobes with small one around intestine and with large one on dorsal
                      side of stomach    
 

    (3) Openings of pancreatic duct

          --- A duct system separated from bile duct system even in the liver having
               hepatopancreas
 

          --- The begining of intestine
 

               Hepatopancreas

                --- Pouring independently from that of common bile duct

    (3) Islet of Langerhans (Insula pancreatica)

          --- Covered by thin exocrine layer
 

          --- Location of endocrine islets in teleostei

                --- a. Within the isolated pancreatic tissue/ Around liver
 

                     b. Discrete near gall bladder (around Ductus choledochus)

                         --- As small bodies surrounded by connective tissue

                     c. Within the spleen

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