I BACK I RETURN I NEXT I SUMMARY I Any Questions? I

Urogenital system 泌尿生殖器系

 1. Kidney 腎臟

     --- Always a paired organ

           --- Long and thin organ

     --- One of most important organs of excretion

           --- Other excretory organs

                 ---> Skin\ Intestine\ Liver

                       Gills in fish

           --- Serving primarily to excrete excess water, esp., in fresh water species

                 --- Gills

                       ---> a. Excretion of harmful metabolic products such as nitrogen-containing excretes

                             b. Excretion of excess mineral salts in marine species

    1) Location

        --- Beneath the vertebrae between anterior and posterior borders

              --- Retroperitoneal location

                    --- Exterior to the dorsal wall of the coelom

        --- Between the dorsal wall of the body cavity and axial skeleton

              --- Anterior portions of the right and left kidneys

                    ---> Separated

                   Posterior portion of the both kidneys

                    ---> Generally fused

    2) Shape

        --- Considerable variation

              --- The shape of the body, the body cavity and the swimbladder

                     --- Considerable influence on the form of kidney

    3) Composition

        --- Reddish-brown color

              <--- High degree of vascularization

                    Abundance of pigment in the tissues surrounding the blood vessels there

       (1) Head kidney

            --- Dorsal and bilateral region of esophagus

                  --- A rudimentary organ

                         --- Pronephros + Cranial portion of mesonephros

                                --- Regression or loss of pronephric kidney tubules

                                     Transformation into pseudolymphoid tissue

            --- Penetrated by posterior cardinal vein

                 Wall of cardinal vein and its branches

                    --- a. Chromaffin cells

                         b. Interrenal gland

                 Thyroid follicles

       (2) Body kidney

            --- Well-developed renal tubules in freshwater fish

                  --- Cranial(sexual) part of opisthonephros

                          --- Mesonephros

                                 <=== Body kidney

                                               = Trunk or abdominal kidney

            --- Tail kidney

                  --- Caudal(renal)part of opisthonephros

                        --- Loss or poorly developed in teleostei

 2. Gonads 生殖腺

    [Embryological consideration for reproductive organs]

       --- Originated from the genital ridge (or swelling)
 

       --- Primordial germ cells + Surrounding connective tissue

             --- (Differentiation)

                    ---> Female structure (Ovary) or male structure (Testis)

    [Types of sexuality in fish]

    --- Testicles and ovaries

          --- Germ glands

                 --- Developed very close to the kidneys

                       --- Gonads and kidneys not at all connected to one-another in the acrania\ agnatha\

                            most of the Teleostei

                 --- Mesodermal tissue of the dorsal wall of the coelom

   1) Testes

       --- Generally long and oval to triangular in cross-section

             --- In general right and left testes

                   ---> A bilateral organ

                         Usual difference between the lengths and the weights of both members of the pair

             --- Coming into contact with one-another at the caudal end of the abdominal cavity

       --- Mesorchia

             --- Suspended from the dorsal wall of the body-cavity

           Tunica albuginea

             --- The peritoneal tissue surrounding the testes

                    --- Tunica serosa of the intestine

             --- A large number of pigment cells

   2) Ovaries

      [Types of ovary in fish]

        a. Cystovarian type in most teleosts

              --- Ovarian cavity

                    --- Oviduct

                          --- Genital pore

        b. Semicystovarian type in certain fish such as salmon or trout

             --- A pocket-like structure that opens to the body lumen
 

             --- No oviducts

                   --- Instead, a 'Funnel-shaped transporting groove'

                           --- Genital pore

        c. Gymnovarian type

            --- The most simple ovary seen in the eel
 

            --- Release of ovulated eggs into body cavity

                  ---> Discharge from the body

       --- Generallay a pair of sac-shaped organ

             --- a. An ovarian wall
 

                  b. An ovarian cavity
 

                      Numeraous ovarian lamellae

                        --- Oogenesis

       --- Originated as paired structures on both sides of the mesentry

             --- Suspended from mesovaria

                   --- The shorter mesovarium in the right ovary

       --- Oviducts

             --- Caudal continuation

                    ---> Genital pore

I BACK I RETURN I NEXT I SUMMARY I Any Questions? I