Fetal Pig Dissection Lab – Quia

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Fetal Pig Dissection Labs
                                       Dr. J. Lim


Objective: In this exercise you will examine the organization of the many body systems
studied this semester in the context of a single specimen, the fetal pig. Be sure to identify
the major organs as you explore the extent of each system.

As you encounter each structure, discuss its function and interactions with
             surrounding structures with your lab partners

Recommendations:
    Carefully follow the directions
    Read the description of each incision and understand it prior to beginning
    Each group should have a directions reader and a dissector
    The rest of the group should follow along referring to the textbook or lecture
     notes with details on the structures being studied
    Use the scissors for most incisions
    All students handling the specimen must wear gloves

                     Use the scalpel only when absolutely necessary

Clean-up at the end of each dissection:
    Dispose of lab discards in the provided receptacles
    Place your pig into the plastic bag provided
          o Expel excess air from the bag and tie it shut
          o Write your group name and class time on the tag provided and attach it to
              the bag
          o Place the bags in the storage bin for your class
    Return dissection instruments to their proper places in the set-up tray
    Clean table tops with red bottled sanitizer
    Wash hands before leaving class




                                             1
FETAL PIG LAB ONE: Respiratory 1, Mouth, Pharynx & Thorax




External Anatomy
    Examine the fetal pig and locate the external features shown above.
    Two rows of nipples of mammary glands are present on the ventral abdominal
      surface of both males and females. Mammary glands later develop only in
      maturing females.
    Umbilical cord: Make a transverse cut through the umbilical cord and examine
      the cut end. Locate the two umbilical arteries that carry blood from the fetal pig
      to the placenta, and the single umbilical vein that delivers nutrient-rich blood back
      to the fetal pig.
    Determine the sex of your specimen
          o Female: The urogenital opening in the female is immediately ventral to
              the anus and has a small genital papilla marking its location.
          o Male: The scrotal sac is ventral to the anus and a urogenital opening is
              just posterior to the umbilical cord.




Positioning the pig for dissection
Place the fetal pig on a dissecting tray ventral (belly) side up. Use two or three rubber
bands to tie the right hind leg around the ankle. Run the rubber bands around the
underside of the tray and tie the left hind leg. Repeat for the forelegs.


                                             2
Dissection Procedure
HEAD AND NECK
To expose the structures of the mouth and pharynx, start by inserting a pair of scissors in
the angle of the lips on one side of the head and cut posteriorly through the cheek. Open
the mouth as you make your cut and follow the curvature of the tongue to avoid cutting
the roof of the mouth. Hold down the epiglottis and surrounding tissue and continue
your incision dorsal to it and on into the opening of the esophagus. Now, repeat the
procedure on the other side so that the lower jaw can be pulled down to expose the
structures of the mouth and pharynx as shown.
                                                                     Teeth: Only a few
                                                                        deciduous canine
                                                                        and/or incisor teeth
                                                                        will have erupted.
                                                                        Other teeth are still
                                                                        being formed and
                                                                        may present as
                                                                        bulges of the gums.
                                                                        Make an incision in
                                                                        one of these bulges
                                                                        to observe the
                                                                        developing tooth.
                                                                     Tongue: The
                                                                        tongue is attached
                                                                        posteriorly and free
                                                                        anteriorly. Locate
                                                                        the papillae on its
                                                                        surface, especially
                                                                        near the base of the
                                                                        tongue and along its
                                                                        anterior margins.
        You will recall that papillae are the home of many microscopic taste buds.
     Hard & Soft palate: roof of the mouth
            o formed anteriorly by the hard palate supported by bone and cartilage
            o formed posteriorly by soft palate
            o paired nasal cavities lie dorsal to the roof of the mouth

                                                        Nasopharnyx: space posterior
                                                         to the nasal cavities and soft
                                                         palate
                                                             o contiguous with the
                                                                 oropharynx or throat
                                                      Oropharynx (throat): space
                                                         posterior to the mouth
                                                             o Posterior extension of
                                                                 nasopharynx
           o may be difficult to visualize because incision cuts through it on each side.


                                              3
When you have completed your observations, close the lower jaw by wrapping a single
rubber band around the snout.

GENERAL INTERNAL ANATOMY
        Using a sharp scalpel, make a small incision through the abdominal skin and
muscle about -inch above the umbilical cord. IMPORTANT: Do not use the scalpel for
further dissection work today. Use scissors to continue cutting along the midsagittal line
on the ventral surface (INCISION 1), first cutting upward toward the neck (it will be
necessary to cut through the ribs as well).

                     Be careful not to cut any underlying organs
         Always cut away from yourself when using scissors for better control
               Rotate the dissecting pan as necessary for better access

                                                   Turn the tray around and cut down to
                                           the caudal (tail) end of the pelvic region,
                                           leaving - inch border around the umbilical
                                           cord. This step is important to prevent cutting
                                           of the umbilical vein and arteries in the
                                           abdominal cavity.
                                                   Continue the midsagittal cut down into
                                           the pelvic region. Cut around the other side of
                                           the umbilical cord (INCISION 2), again
                                           leaving about a -inch border. Stop your cut
                                           about one inch short of the anus.
                                                   Make the two lateral incisions just in
                                           front of the hind legs (INCISION 3).
                                           If you have a male pig, cutting off-center
                                           ensures that you do not cut the penis, which is
                                           incompletely formed in the fetal pig and
                                           appears as a thickened tube within the skin of
the lower abdominopelvic area.
       You may omit INCISION 4.
       Make two lateral incisions (INCISION 5) through muscle and ribs out from the
midline incision.
       Lifting the lateral flaps of ribs, skin and muscle on each side, cut the diaphragm,
which is attached to the inside body wall. You should now be able to peel open the left
and right flaps of the ventral body wall like a book.
       Wash out the cavities of the pig in a sink if needed to remove any brownish
material (mainly bile and clotted blood) while being careful to keep the organs in place.
       You may loop the rubber bands around the legs as necessary to get a better view
into your specimen. When you are finished with your pig, do not cut the rubber bands!
Simply slide the rubber band from under the pan so that next time you need not retie the
pig.




                                            4
THORACIC ORGANS




      Lungs: The thoracic cavity is divided into left and right pleural cavities
       containing the lungs. At the midline, the inner thoracic wall forms a partition
       between the pleural cavities called the mediastinum.
      Heart: The heart can be found enclosed in the pericardial sac located within the
       mediastinum and attached to the diaphragm. Remove this sac to expose the heart.


FETAL PIG LAB TWO: Respiratory 2, Neck & Cardiovascular
NECK
    In the neck region, locate the larynx (voice box) which is composed of cartilage and
contains the vocal cords. The trachea (windpipe) extends posteriorly from the larynx
and splits dorsal to the heart to form the bronchi that enter the lungs. These structures
are more clearly visible after the heart has been removed.
     Thymus gland: whitish gland that lies near the anterior margin of the heart and
        extends into the neck on each side of the trachea
     Thyroid gland: on anterior surface of the trachea at the base of the neck
Remove the thymus and thyroid glands as necessary to get a better view of the trachea
and larynx, but do not cut major blood vessels
     Esophagus: carefully remove the connective tissue supporting the trachea so that
        you can move the trachea to one side to expose the esophagus located dorsal to it
            o you will get a better view of the esophagus later on




                                            5
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