1. External anatomy of the amphioxus (the lancelet)
    • Slender body and is aquatic
    • Somewhat compressed laterally
    • Degenerate head with oral hood surrounding it that has buccal cirri
  2. Image Upload 1
    Dorsal fin



    Atriofin that goes from atriopore to anus

    Caudal fin
  3. External anatomy again

    -- midgut?
    External anatomy

    There is an outpocketing under the mid gut (in yellow) called the hepatic diverticulum or mid gut cecum; forerunner of the liver but does not function at all like a liver

    From the mid gut, there is a constriction of the neural tube; and, the narrow region is the ???
  4. buccal cirri
    tentacle like projections on the head end
  5. Explain the mouth region.
    • Once the food enters the mouth, it goes to the pharynx, which has a bunch of slits in it as demonstrated above
    • Those slits are protected by gill bars, protecting the slits
    • There are also horizontal structures that go across one slit to the next and they keep the gills from closing; these are synapticula, which help prevent the collapse of the slits
  6. Digestive system
    • Filter feeder
    • Hood with buccal cirri play role in digestive system because it helps bring food back into oral hood
  7. What is a filter feeder?
    (animals filter water and microorganisms that are coming in; they need a mechanism to draw that water into their oral hood; the mouth is at the back of the vestibule, not at the entrance of the oral hood)
  8. Vestibule is __
    opening under oral hood
  9. On inside of oral hood are __

    The whole structure is __ located in the __ and __ of __; made of __; help __; called the __
    • patches of cirrated epitelium
    • horse-shoe shaped
    • side and roof of oral hood
    • ciliated epithelium
    • project water and food toward the mouth
    • wheel organ
  10. - To assist in movement, the highlighted area has a place called __, which does what?
    ___ extend out of the oral hood; they are __ that help create currents to bring the food back into the structure, which is the __.
    • Hatscher’s pit
    • secretes mucus
    • fingerlike projections
    • ciliated epithelial patches
    • wheel organ
  11. At the back of the vestibule is a structure called the __, which has __ as a a part of that membrane. Those tentacles, when closed, will not __because __; and, when the tentacles are open, then the mouth is available; tentacles __

    thin tentacles

    • allow passage outside of vestibule
    • the slit in the vellum is the mouth

    guard the mouth
  12. Two grooves in the pharynx: one in the roof and one in the floor

    Explain the floor one.
    In the floor of the pharynx is the endostyle (in green), a structure that secretes mucus
  13. Two grooves in the pharynx: one in the roof and one in the floor

    Explain the roof one.
    • In the roof of the pharynx is the epipharyngeal groove (blue)
    • The whole groove is ciliated so that the food can get caught and be pushed through the pharynx into the midgut
  14. After midgut, the __ is next, where solid wastes come out

    In terms of the __, the __(4) , as well as __,are in the atrium, the last of which are in the floor
    The gametes exit through the __as well
    • hind gut
    • atrium
    • pharynx, stomach, diverticulum, and some of the hind gut
    • gonads
    • atriopore
  15. Circulatory System
    - skin
    - function of skin
    - function of circ system
    - system type
    - components
    - speed
    • Unlike most, this circulatory system does not function in respiration
    • Amphioxis uses skin as respiratory organ
    • The function is to transport the digestive materials
    • It has an open system; it has arteries and veins but no capillaries; pretty sluggish (open systems are very sluggish)
    • It does not have a heart and it lacks RBCs; no capillaries
    • Very slow
Card Set
Test One