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Jun 14, 2024, 7 min read

for all questions, remember this is for a fetal pig, so there are multiple routes (even if one may be more preferred). the beginning of all four routes in this situation can be cross referenced with day 2. i’m kind of lazy, so i’d just point to the diagram i posted in the corresponding channel of the anterior blood system. remember also that the anterior and posterior vena cava connect to the right atrium, and blood that enters the right atrium can travel through the fetal circulatory system in either method; and, all of the routes below are dependent on this being a fetal pig due to specific adaptations.

in both 1 and 2, the first option below prefaces the route if the blood travels through the ductus arteriosus of the fetal pig. it is more likely to occur if the blood traveled downwards from the anterior vena cava. the second option prefaces the route if the blood travels through the foramen ovale and is more likely to occur if the blood traveled from the posterior vena cava and has an upwards trajectory. 1. anterior vena cava or posterior vena cava β†’ right atrium β†’ right ventricle β†’ pulmonary trunk β†’ ductus arteriosus β†’ descending aorta 2. anterior vena cava or posterior vena cava β†’ right atrium β†’ foramen ovale β†’ left atrium β†’ left ventricle β†’ aortic arch β†’ descending aorta

the following steps are all specific to anatomy from day 3. i’m working on other things right now and don’t have my tablet nearby, but i can try to connect the old diagram to day 3 later (i probably won’t with day 4… that’s a lot of effort)

  • start with the general path. use the whiteboard diagrams above; the descending aorta directly connects to the posterior arteries.
  • the next step is going to depend on what organ you’re looking at, or what question you’re answering. these routes should directly succeed the descending aorta.
    1. there are two possible routes:
      1. coeliac artery β†’ gastrohepatic artery β†’ duodenum β†’ jejunum β†’ ileum [all three sections of the intestine]. the gastrohepatic artery leads specifically to the duodenum, though note it can also lead to many other digestive organs
      2. anterior mesenteric artery β†’ duodenum β†’ jejunum β†’ ileum [all three sections of the intestine]. the anterior mesenteric artery just leads to both intestines.
    2. there is only one possible route, thank god. left external iliac artery β†’ left hindlimb. note that this was a vessel you may have been unable to see, but was noted to be one to know in terms of function regardless
    3. also only one possible route. left umbilical artery β†’ placenta. ignore the left iliac artery, it will not lead to the placenta.
    4. there are two possible routes:
      1. anterior mesenteric artery β†’ large intestine. the anterior mesenteric artery just leads to both intestines; see question 1.
      2. posterior mesenteric artery β†’ large intestine. the posterior mesenteric artery leads to the rectum and the large intestine.
  • use the second diagram above to return to the right atrium through the posterior veins into the posterior vena cava. again, this depends on what path you took.
    1. only one possible route. capillary bed of the small intestine β†’ hepatic portal vein β†’ liver β†’ liver capillaries β†’ hepatic veins β†’ posterior vena cava.
    2. only one possible route. left common iliac vein β†’ directly into the posterior vena cava.
    3. this one might have two routes. remember the importance of the ductus venosus and why it was adapted in mammals. both will start in the umbilical vein. the second route is definitely the important one for this question.
      1. umbilical vein β†’ liver capillaries β†’ hepatic veins β†’ posterior vena cava. this is the lossier method in which most blood which entered through this route would have gone towards the liver.
      2. umbilical vein β†’ ductus venosus β†’ directly into the posterior vena cava. in this route, basically all of the blood which entered the ductus venosus should have been redirected to the heart.
    4. only one possible route. capillary bed of the large intestine β†’ hepatic portal vein β†’ liver β†’ liver capillaries β†’ hepatic veins β†’ posterior vena cava. this is identical to question 1.
  • all of these routes will lead into the posterior vena cava. this means all of the routes end identically, connecting from the posterior v.c. to the right atrium; you can cross reference this with day 2 or prior information.

umm. tldr?

  1. starts with anterior vena cava β†’ somehow exits the heart β†’ descending aorta β†’ EITHER: 1. β†’ anterior mesenteric artery β†’ duodenum β†’ jejunum β†’ ileum (must start in duodenum) 2. β†’ coeliac artery β†’ gastrohepatic artery β†’ duodenum β†’ jejunum β†’ ileum
    • β†’ continues through capillary beds of the small intestine β†’ hepatic portal vein β†’ liver β†’ liver capillaries β†’ hepatic veins β†’ posterior vena cava β†’ right atrium
  2. starts with anterior vena cava β†’ somehow exits the heart β†’ descending aorta β†’ left external iliac artery β†’ left common iliac artery β†’ posterior vena cava β†’ right atrium
  3. posterior vena cava β†’ somehow exits the heart β†’ descending aorta β†’ left umbilical artery β†’ placenta β†’ umbilical vein β†’ EITHER: 1. liver capillaries β†’ hepatic veins 2. ductus venosus
    • β†’ continues through posterior vena cava β†’ right atrium
  4. posterior vena cava β†’ somehow exits the heart β†’ descending aorta β†’ EITHER anterior mesenteric artery or posterior mesenteric artery β†’ large intestine β†’ capillary bed of the large intestine β†’ hepatic portal vein β†’ liver β†’ liver capillaries β†’ hepatic veins β†’ posterior vena cava β†’ right atrium

okay so funnily enough i think all of these questions are just based on information from days 2 and 3, so if you can figure out how to follow a drop through specifically the anterior and posterior circulatory system, you’re good :FarThumbsUp: all of these are multistep questions which follow a drop of blood over the long term; i would break these down into sections and map out each one mentally to solve them.

  • 1 is actually question 3 into question 2 from the previous page. you need to connect those two routes together.
  • think of 2 as 3 sets of questions:
    • follow a drop of blood from the right side of the brain returning to the right atrium. do not follow the droplet from the heart out towards the right side of the brain.
    • follow a drop of blood from the [which vena cava (hint: or circulatory system) connects to the brain?] to the placenta, then back to the right atrium.
    • follow a drop of blood from the [which vena cava (hint: or circulatory system) connects to the placenta?] to the right side of the pelvis. do not return to the right atrium.
  • similarly, think of 2 as 3 sets of questions:
    • follow a drop of blood from the right forelimb back to the right atrium. do not follow the droplet from the heart out towards the right forelimb. (this was almost 1:1 answered from the previous page, but you need to redirect to the opposite forelimb.)
    • follow a drop of blood from the [which vena cava (hint: or circulatory system) connects to the forelimbs?] to the small intestine, including all three subregions, then back to the right atrium.
    • follow a drop of blood from the right atrium to the aorta. (this can be 1:1 answered using notes from general mammalian hearts, such as the sheep heart dissection.) since these are all multistep, they’re super long, but i wouldn’t mind breaking down one specific question or one question at a time if asked. i have the feeling i should try to connect the day 2 and day 3 diagrams bc of this though lmao

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