Docstoc

Pig dissection.ppt

Document Sample
Pig dissection.ppt Powered By Docstoc
					Pig Dissection
• http://faculty.clintoncc.suny.edu/faculty/Mic
  hael.Gregory/files/Bio%20102/Bio%20102
  %20Laboratory/Fetal%20Pig/Fetal%20Pig.
  htm
     Directional and Anatomical
             Terminology
• Anatomists and morphologists rely on a
  set of terms to describe structural
  positions, These may not all be
  immediately obvious to you, so you should
  practice using them. The terms are
  generally presented to you in pairs, as
  terms are often used to indicate opposing
  directions.
          Planes of section.
• We can figuratively (or actually) section
  (=cut) our subject using planes. There are
  several particular planes of section that
  are useful for the purposes of discussing
  anatomy.
1.    Anterior - near or toward the head
2.    Posterior - near or toward the tail
3.    Dorsal - referring to the back
4.    Ventral - referring to the belly
5.    Lateral - referring to the side
6.    Median - referring to the midline
7.    Cranial - referring to the head
8.    Caudal - referring to the tail
9.    Proximal - toward the attached end of a structure
10.   Distal - toward the free end of a structure
11.   Longitudinal - in the axis from head to tail
12.   Transverse - across the longitudinal axis
13.   Pectoral - chest or shoulder area
14.   Pelvic - hip region
15.   Inferior- toward or closer to the tail (caudal region)
16.   Superior- toward or closer to the head region
Page Pig Book Use color on every page!                                  Points

1         Title Page Names of authors (max of 2)                      10
           Be creative, use color and make it fun!!!
2         Basic Anatomical terms                                      37
          Diagram showing 16 terms from the lab color 5pts
3         External anatomy: Diagram of head, neck, trunk, tail. 29 Label=Thorax, Abdomen, Sacral What is
          inside and out of these sections? How can you tell male from female?         color=5pts
4         Internal Anatomy Diagram with parts labeled and umbilical cord drawing
5         Circulatory System: Purpose, flow of blood, structures/functions, diagrams of arteries and veins X
          section, Heart diagram, path of blood flow,
          color coded Red = oxygenated Blue= deoxygenated
6         Respiratory System: Purpose, flow of air, structures and functions. Diagram of inspiration and
          expiration
7         Digestive System: Purpose, path of food, structures and functions
8         Excretory System: Purpose, organs of excretion. Diagram of a cross section of the
          kidney. Path of flow of nitrogen waste as it is formed and removed from the pig’s body
9         Reproductive System: Purpose, structures and functions Female: structures and how do they
          work. Male and how do they work
10        Nervous System: Purpose, How is it broken into parts?
Anterior - near or toward the head
Posterior - near or toward the tail
             or back
Dorsal - referring to the back
Ventral - referring to the belly
Lateral - referring to the side
Median - referring to the midline
Cranial - referring to the head
 Caudal - referring to the tail
Proximal -
toward the
attached end of
a structure
Distal - toward
the free end of a
structure
Longitudinal - in the axis from
        head to tail
       Transverse - across the
           longitudinal axis
• is an imaginary plane that divides the body
  into superior and inferior parts. It is
  perpendicular to the coronal and sagittal
  planes.
Pectoral - chest or shoulder area
Pelvic - hip region
Inferior- toward or closer to the tail
           (caudal region)
  Superior- toward or closer to the
             head region

• As with vertebrate directional terms, superior
  and inferior can be used in a relative sense in
  humans, but can not be uniformly applied to
  other organisms with varying normal anatomical
  positions. For example, the shoulders are
  superior to the navel, but inferior to the eyes in
  humans. In any tetrapod, the shoulders are
  cranial to the belly, but caudal to the eyes.
           sagittal section
• The sagittal section, or plane, divides the
  subject into left and right portions.
             Mid-sagittal
• The mid-sagittal section splits the subject
  exactly into left and right sides.
              transverse
• A transverse plane, also known as an
  axial plane or cross-section, divides the
  body into cranial and caudal (head and
  tail) portions.
         Directional Terms:
• Anatomists rely on a set of directional
  terms to explain the orientation of subject
  material. Although some of the terms are
  unfamiliar, with practice they will become
  easier to use, and you will see that
  “proximal to” is lesser cumbersome than
  “up the extremity and closer to the middle
  of the body.”
              left and right
• stated relative to the subject, not relative
  to the people viewing it
          anterior (cranial)
• towards the front (head) of the animal
         posterior (caudal)
• towards the back (tail) of the animal
                superior
• higher on the subject- typically used on
  bipeds such humans
                inferior
• lower on subject- also used on subjects
  such as humans
                dorsal
• towards the back
                 Ventral
• towards the belly
                 medial
• towards the mid-sagittal section
                 lateral
• away from the mid-sagittal section
                proximal
• towards the mid-sagittal section along a
  limb
                  distal
• away from the mid-sagittal section along a
  limb
          External Anatomy
• The body consists of the following regions:
  head, neck, trunk, and tail. The 2 pairs of
  appendages present on the trunk are the
  fore legs and hind legs. The cord
  projecting from the ventral surface is the
  umbilical cord. This cord connects the fetal
  pig to the placenta within the uterus of the
  mother pig.
Pig Book
1Title Page        Names of authors (max of 2) Be
  creative, use color and make it fun!!!
2Basic Anatomical terms Diagram showing 16 terms
  from the lab

3External anatomy: Diagram of head, neck, trunk,
  tail. Thorax (what is inside?) Abdomen (what is
  inside?) Sacral (what is here?) How can you tell
  male from female?
4Internal Anatomy Diagram with parts labeled and umbilical cord
  drawing
5Circulatory System: Purpose, flow of blood, structures/functions,
  diagrams of arteries and veins X section, Heart diagram, path of
  blood flow, color coded Red = oxygenated Blue=
  deoxygenated
6Respiratory System: Purpose, flow of air, structures and functions.
  Diagram of inspiration and expiration
7Digestive System: Purpose, path of food, structures and functions
8Excretory System: Purpose, organs of excretion. Diagram of a
  cross section of the kidney. Path of follow of nitrogen waste as it
  is formed and removed from the pig’s body.
9Reproductive System: Purpose, structures and functions
  Female: structures and how do they work.
  Male and how do they work
10Nervous System: Purpose, How is it broken into parts?
       Fetal Pig Dissection
• Objectives: Upon completion of this lab
  students should
• Be able to identify, and know the names
  and functions major structures of the fetal
  pig's external anatomy.
• Be able to identify, and know the names
  and functions of the major structures of the
  fetal pig's internal gross anatomy.
• The fetal pigs that we will use in lab
  were purchased from a Biological
  supply company. They obtain fetal pigs
  from processing plants - the unborn pigs
  are removed from the uteri of
  slaughtered sows.
• The period of pregnancy (gestation) in pigs
  is about 17 weeks (compared to 40 weeks
  in humans).
• The fetal pigs we will use in class are 3-4
  weeks from birth. You will work in groups on
  the fetal pigs. Each group of students will
  be given a fetal pig to be used for the labs
  on pig dissection.
• Attach a tag with your names (in pencil) to
  one of the hind legs for future identification.
• Note the slit in the skin in the neck region of
  the pig. (ours were not injected)

• This is the area where the circulatory
  system of the pig was injected with latex
  (red latex in the arterial system, blue latex
  in the venous system) to make it easier to
  see and trace the blood vessels.
                                 Page 2
1.    Anterior - near or toward the head
2.    Posterior - near or toward the tail
3.    Dorsal - referring to the back
4.    Ventral - referring to the belly
5.    Lateral - referring to the side
6.    Median - referring to the midline
7.    Cranial - referring to the head
8.    Caudal - referring to the tail
9.    Proximal - toward the attached end of a structure
10.   Distal - toward the free end of a structure
11.   Longitudinal - in the axis from head to tail
12.   Transverse - across the longitudinal axis
13.   Pectoral - chest or shoulder area
14.   Pelvic - hip region
15.   Inferior- toward or closer to the tail (caudal region)
16.   Superior- toward or closer to the head region
   External Anatomy
• Page 3 draw a diagram of the main parts

• Place the pig on its side in the pan and note
  that the body consists of the following regions:
• head, neck, trunk, and tail.
• The 2 pairs of appendages present on the trunk
  are the fore legs and hind legs. The cord
  projecting from the ventral surface is the
  umbilical cord.
• This cord connects the fetal pig to the placenta
  within the uterus of the mother pig.
• The head bears the mouth and jaws, the
  snout (nose), the external nostrils (nares),
  the eyes, and the external ears. Feel the
  relatively thick neck in the fetal pig. This
  thickness is due to the presence of well-
  developed neck muscles that will
  eventually be used for rooting.
• The cranial portion of the trunk is called the
  thorax (chest) and is encased by the ribs. Feel
  the ribs under the skin and determine the
  posterior border of the thorax. The thorax
  contains the lungs, heart, and major blood
  vessels.
• The fore legs are found in the thoracic region.
  The parts of each of these appendages as well
  as those of the hind legs (in the sacral region) are
  the upper leg, lower leg, wrist, foot, and toes
  (digits).
• Examine the digits present on the legs and note
  that only 2 of the 5 digits found in most terrestrial
  vertebrates are present. The first toe
  (corresponding to our thumb) has been lost; the
  second and fifth toes are reduced, with only the
  third and fourth toes being fully developed.
• The caudal portion of the trunk is called the
  abdomen.
• In contrast to the thorax, the ventral portion
  of the abdomen is soft. The umbilical cord
  is located near the posterior end of the
  abdomen. There are 2 rows of teats
  (mammary papillae), one on either side of
  the umbilical cord. The stomach, intestine,
  kidneys, and other viscera (soft internal
  organs) are found within the abdominal
  cavity.
• The sacral region includes the hind legs,
  pelvic bones, and their attachment to that
  area of the vertebral column.
• The anus (posterior opening of the digestive
  tract) is located under the tail.
• In female pigs, the vulva (openings of the
  reproductive and urinary tracts) is found just
  below the anus.
• In male pigs, the external opening of the
  penis is located posterior to the umbilical
  cord. The scrotum (scrotal sacs) are found
  on either side of the midline of the anus.
Page 3
   Internal Anatomy                     Page 4
• For the dissection of the fetal pig you will need
  string, a scissors, a sharp scalpel, a blunt probe, a
  forceps, and dissecting pins.
• The definition of dissecting is to separate the body
  into parts for the purpose of study. This means
  that your scissors and scalpel should be used
  sparingly and with care. The most useful
  dissecting instrument is a blunt probe, which can
  be used to separate organs from membranes.
1.   Place the pig on its dorsal surface in the dissecting pan.
     Tie a string around one fore leg and passing the string
     under the pan tie the other end to the other fore leg. The
     string should be tied tight enough to spread the forelegs
     apart.
2.   Tie a string in the same fashion to the hind legs. Do not
     remove the string from the appendages at the end of the
     lab; simply slip the strings out from under the pan at the
     end of each lab period.
3.   Mark a line on the skin with a permanent marker from the
     tip of the lower jaw to a point 12 millimeters (mm), (about
     2 inch), in front of the umbilical cord. Divide the line
     around the umbilical cord and mark a pair of parallel lines
     about 12 mm apart back to the posterior boundary of the
     abdominal wall. Make sure that you understand where to
     draw these lines - if you are not sure ask the lab
     instructor.
4.   Examination of the Skin: Use your scalpel to cut
     through the skin and into the underlying connective
     tissue along the line extending from in front of the
     umbilical cord to the tip of the jaw. Recall that the
     dermis of the skin is a dense connective tissue, while
     the subcutaneous layer is a loose connective tissue.
     Use your probe to separate the thick layer of skin
     (epidermis and dermis) from the underlying loose
     connective tissue for about 25 mm (1 inch) on one side
     of the incision in the region posterior to the fore legs.
     Use your scissors to cut out a piece of skin about an
     inch square from that area.
5.   Examine the skin and note its leathery texture. The skin
     of pigs contains a large number of hair follicles, which
     will only appear as whitish lines in the skin of your fetal
     pig. Examine the slide of skin when you are finished
     with the gross dissection of the fetal pig in this lab.
       ABDOMINAL REGION
1. In order to open the body cavity, use your
   scissors to cut completely through the body
   wall beginning just in front of the umbilical
   cord (follow the line cut previously). As you cut
   anteriorly you will cut through the sternum
   (breastbone) - keep the tip of your scissors up
   so that you do not damage the underlying
   structures.
2. Next, use your scissors to make the parallel
   posterior cuts through the body wall.
3.   Umbilical Structures: A cord will be seen in the abdominal
     cavity extending anteriorly from the umbilical cord. This cord
     is the umbilical vein, which carries fetal blood from the
     placenta to the liver. Cut this vein about half way between
     the liver and the umbilical cord. Keep the position of this
     vein in mind as it will be traced later. Pull the flap of the
     body wall containing the umbilical cord posteriorly to expose
     the underside of the flap. On the underside note the 3 cords
     entering the body cavity by way of the umbilical cord. The
     lateral pair are the umbilical arteries which carry fetal
     blood to the placenta. The large sac in the center is the
     urinary bladder. The duct extending from the urinary
     bladder into the umbilical cord is the allantoic duct. This
     duct carries nitrogenous wastes from the bladder to the
     placenta. The fetus receives oxygen and food from the
     mother by way of the placental circulation and gives up
     carbon dioxide and nitrogenous wastes.
4. Cut off about 12 mm of the umbilical cord in
   order to observe in cross-section the 3 blood
   vessels and the allantoic duct. The blood
   vessels in the umbilical cord consist of 2
   umbilical arteries (may show red latex) with
   relatively thick walls and an umbilical vein
   with a thinner wall. A fourth small vessel, the
   allantoic duct, is from the urinary bladder.

5. Make a drawing of a cross-section of the
   umbilical cord showing the 4 vessels -
   label your drawing.
6. Make a pair of lateral incisions through the body
   wall on each side in front of the hind legs (see
   figure one) to expose the abdominal cavity.
   Wash out the abdominal cavity with tap water to
   remove the coagulated blood present. When
   examining the viscera (soft internal organs) with
   your fingers be careful not to tear any of the
   structures. The body cavity (coelom) in which
   the thoracic and abdominal organs are located is
   completely lined with an epithelial layer called
   the peritoneum.
Organs are also covered with a layer of peritoneum.
   This layer of epithelium is derived from the
   mesoderm germ layer. A double layer of
   peritoneum is called a mesentery. Mesenteries
   serve to suspend and hold structures together in
   the coelom.
•   Once you have opened the abdomen and washed
    out the cavity and locate the organs listed in the
    paragraphs below.
•   The most obvious structure in the abdominal cavity
    is the liver. The liver is composed of 5 lobes which
    are attached only at the dorsal and anterior
    margins. Posterior to the liver are the small
    intestine and the thicker coiled large intestine
    (colon). The small and large intestines are
    suspended from the mid-dorsal body wall by a
    mesentery. Blood vessels and nerves are found
    between the two layers of peritoneum making up
    the mesentery. Carefully lift and push the small
    intestine forward and find where the posterior part
    of the small intestine enters the large intestine.
mesentery
• Put the intestines back in their normal positions and
  lift the liver forward to see the soft, white-walled
  stomach anterior to the intestines. The dark-colored
  spleen is located along its left posterior border and
  attached to the stomach by peritonium.
• A light-colored granular structure, the pancreas, is
  found in the mesentery between the stomach and
  the first portion of the small intestine. The gall
  bladder may be seen by lifting up the extreme right
  lobe of the liver. It appears as a small upside down
  sac under the lobe. The duct from the gall bladder,
  the bile duct, opens into the duodenum (first
  portion of the small intestine). The pancreatic duct
  also opens into the duodenum at about the same
  location as the bile duct. Is it possible to find and
  trace the path of these ducts in your fetal pig?
• Behind the peritoneal lining of the dorsal
  part of the abdominal cavity are the
  relatively large kidneys. Cut the
  peritoneum along the lateral border of the
  left kidney and pull it off toward the midline.
• Locate the muscular diaphragm, which
  separates the abdominal and thoracic
  cavities. The diaphragm is thin in the
  center but thicker at the periphery.
Pancreas
         THORACIC REGION

• In order to see the organs in the thoracic
  cavity, it is necessary to cut the
  attachment of the diaphragm to the body
  wall on both sides.
1.   Cut the diaphragm away from the body wall on both sides of the pig.
2.   Force the thoracic cavity open with your fingers to expose the lungs and
     heart. The lungs appear as solid bodies since they do not contain air in
     the fetus. The lobes of the left and right lungs, and the heart are
     surrounded by peritoneum - note the peritoneum as you force the thoracic
     cavity open. This means that each organ is enclosed in a separate sac.
     The sac enclosing the hearts is called the pericardial sac, and the sac
     enclosing each lung is called a pleural sac.
3.   Force the thoracic cavity open further to examine the lungs more closely.
     Note that the left lung is divided into 3 lobes and the right lung into 3 lobes
     plus a fourth lobe that passes ventral to a large vein and is directly
     posterior to the heart.
4.   The 2 large lobes of whitish granular tissue concealing part of the heart
     and the anterior blood vessels is the thymus gland. The thymus extends
     anteriorly for a short distance into the neck region. This gland is relatively
     large in young animals but degenerates after sexual maturity.
5.   The thyroid gland is a small gland located against the trachea just in front
     of the thorax. This gland is brownish in color in preserved fetal pigs.
              Slide of Human Skin
• The skin is composed of 2 layers; an outer, thin epidermis and
  an inner, thick dermis. Examine the slide under scanning and
  low power, and identify these 2 layers. Refer to the handout.
• The dermis consists of a dense connective tissue. Identify the
  nuclei of the fibroblasts and the fibers in your section. Blood
  vessels are present in the dermis but not in the epidermis. Can
  you identify a blood vessel in your section? It is sometimes
  possible to see the red blood cells within the small blood
  vessels of the dermis.
• Sweat glands and hair follicles are present in the dermis and
  extend up through the epidermis. Find a section through a hair
  follicle and the associated sebaceous (oil) glands.
• The sebaceous glands and follicles are derived from the
  epidermis. The subcutaneous layer is under the dermis.
  This is a loose connective tissue containing many fat cells.
  Identify the fat cells in your section.
Circulatory System                    Page 5
• The flow of blood in the circulatory system
  is as follows:
• heart-->arteries-->arterioles-->capillaries--
  >venules-->veins--> heart
• Arteries and arterioles are thick-walled
  vessels that carry blood away from the heart,
  whereas veins and venules are relatively
  thin-walled vessels that carry blood toward
  the heart. Arterioles subdivide in the various
  tissues of the body to ultimately form
  capillaries. Capillaries eventually come
  together to form venules. The small, thin-
  walled capillaries are the functional units
  of the circulatory system. The exchange of
  materials between blood and the cells takes
  place at the capillaries.
• Blood transports oxygen from the lungs to the
  body tissues and returns carbon dioxide to
  the lungs. The right auricle and the right
  ventricle are involved in transporting blood to
  the lungs (pulmonary circulation) and the left
  auricle and left ventricle are involved in
  transporting blood to the body tissues
  (systemic circulation). In other words, the
  right side of the heart pumps deoxygenated
  blood to the lungs and the left side of the
  heart receives oxygenated blood from the
  lungs and pumps it to the body tissues.
• Examine the demonstration slide of an artery
  and vein sometime during the lab period.
      A. Examination of the Heart
• Locate a pair of thickened white strands, which are
  present on either side of the pericardial sac. These
  are the phrenic nerves. Tease these nerves away
  from the pericardium and observe their distribution to
  the diaphragm.
• Remove the pericardial sac from around the heart -
  be careful to not cut blood vessels or nerves in the
  process. Note that the pericardial membrane is
  strongly attached where the blood vessels enter and
  leave the heart. Identify the 4 chambers of the heart:
  the thin-walled right atrium (auricle), the thin-walled
  left atrium (auricle), the thick-walled right ventricle
  and the thick-walled left ventricle. Note the coronary
  artery and the coronary vein which are present in the
  diagonal groove between the 2 ventricles.
    1. Major Arteries and Veins -
                Heart
• Veins
• Several veins from the head, neck, shoulders and fore
  legs join to form the superior vena cava (anterior vena
  cava, precava), which enters the anterior portion of the
  right atrium. These veins are located ventral to the
  arteries supplying the same regions, but the veins are
  thin-walled and more difficult to trace. Pressing on the
  auricle with your fingers will force fluid into the veins and
  may help in tracing them. The muscles extending from
  the sternum to the larynx and head may have to be
  removed in order to expose the veins.
• The inferior vena cava (posterior vena
  cava, postcava) enters the posterior portion
  of the right atrium. Find where this vein
  penetrates the center of the diaphragm,
  passes through a groove in the small
  median lobe of the lung, and into the right
  atrium (it may be necessary to lift up the
  posterior portion of the heart). This vein
  returns all the blood from the posterior part
  of the body to the heart.
• Hidden partially
  behind the
  pulmonary artery,
  the aorta is a large
  vessel that
  branches into the
  brachiocephalic(3)
  and the left
  subclavian artery
  (7)
1. Pulmonary Artery
                    Arteries

• Two large arterial trunks leave the ventricles
  anteriorly. The most ventral trunk is the
  pulmonary trunk, which transport blood directly
  to the lungs. This artery will be traced later. The
  other trunk, the aortic arch, gives off 2 main
  arteries, which send branches to the fore legs,
  shoulder, neck, and head regions. Lift the left
  lung to trace the aortic arch dorsally. It turns
  posteriorly and runs along the dorsal midline as
  the dorsal aorta and eventually delivers blood to
  the entire posterior part of the body.
      Other Closely Associated
             Structures

• Ventral to the dorsal aorta is a thick, white tube,
  the esophagus, which leads from the pharynx
  through the diaphragm and into the stomach.
  Along the esophagus run 2 main branches of the
  vagus nerve. The vagus nerves innervate the
  thoracic and abdominal viscera. Another pair of
  nerve cords, bearing a series of small swelling
  along their course, may be seen behind the
  peritoneum dorsal and lateral to the aorta on
  either side. These are the main trunks of the
  sympathetic nervous system.
     B. Systemic Circulation
• You will identify the main branches of the
  systemic arteries and veins, including the
  hepatic portal system. This will be done in
  order to understand where the major
  organs obtain their blood supply and
  where the blood goes after leaving them
      Systemic Arteries -Diagram
• The brachiocephalic artery (innominate) is the
  first major artery branching off the aortic arch.
  Find this artery, which branches to give rise first to
  the right subclavian artery and then to the right
  and left common carotid arteries. The carotids
  carry all blood going to the head region. In the
  head they branch into the external carotids, which
  supply the face, and the internal carotids, which
  supply the skull cavity and brain (we will not trace
  these arteries). The second major artery to arise
  from the aortic arch is the left subclavian artery -
  note that the left subclavian artery arises directly
  from the aortic arch.
• Separate one of the nerve cords which run
  parallel to the common carotids in a
  common sheath. The nerves are the main
  trunks of the vagus nerve and sympathetic
  nervous system. These were seen before
  as separate nerves in the thoracic region.
  Trace the nerves on one side to the point
  where they separate.
• The dorsal aorta gives off a series of small
  segmental arteries dorsally between the ribs,
  and one or more small arteries ventrally to the
  esophagus. In order to trace the aorta into the
  abdominal cavity, cut directly through the
  diaphragm to the aorta. At the point where the
  aorta penetrates the diaphragm, the celiac artery
  arises from the aorta sending branches to the
  spleen, pancreas, stomach, and liver. The
  anterior mesenteric artery branches from the
  aorta and is found posterior to the celiac artery.
  The anterior mesenteric artery sends branches to
  the small intestine and the coiled portion of the
  large intestine.
• Dissect the left kidney free from the dorsal
  body wall and turn it to the right to expose
  more of the dorsal aorta. Locate the renal
  artery. Put the kidney back in its original
  position and continue to explore the aorta
  posteriorly. If your fetal pig is a female, be
  careful not to damage the ovaries, oviduct,
  and uterus during the upcoming exercises.
  These structures are suspended by
  mesenteries within the posterior region of
  the abdominal cavity.
• The posterior mesenteric artery (inferior
  mesenteric) runs ventrally from the aorta to the
  colon. A pair of genital arteries arise laterally to
  supply the reproductive organs. A pair of
  relatively large iliac arteries arise next and
  extend laterally to the hind legs. Slightly posterior
  to these, locate the umbilical arteries which
  supply blood to the bladder and placenta. After
  birth the umbilical arteries degenerate into a pair
  of small vessels supplying only the urinary
  bladder. The most posterior extension of the
  aorta, the tiny caudal artery, will be seen when
  the reproductive system is examined.
          Systemic Veins -

• Dorsal to the iliac arteries are the iliac
  veins which unite to form the postcava.
  As the postcava runs anteriorly it receives
  the segmental veins from the body,
  genital veins from the reproductive
  structures, and renal veins from the
  kidneys. Note that the postcava turns to
  the right around the dorsal aorta and
  comes to lie almost ventral to it at the level
  of the renal veins.
• From this point on the postcava is not easily
  followed since it is embedded dorsally in the
  extreme right lobe of the liver. Turn the intestines
  and liver to the left, and scrape the liver tissue
  away from the point where the postcava enters
  the liver to the point where it penetrates the
  diaphragm. In the anterior part of the liver, it
  receives several hepatic veins - at least one from
  each lobe - and also a small connection from the
  umbilical vein. This connection, which is difficult
  to find in the liver tissue, is lost after birth. The
  umbilical vein distributes itself to the lobes of the
  liver, where it is continuous with parts of the
  hepatic portal vein.
• The hepatic portal vein begins in capillaries in
  the small and large intestines, and ends in
  capillaries in the liver. The liver capillaries collect
  into the hepatic vein already mentioned. Find the
  hepatic portal vein as it leaves the center coil of
  the large intestine dorsally. It soon receives a
  large branch from the small intestine, and later a
  smaller one from the spleen, pancreas, and
  stomach. Shortly thereafter, the hepatic portal is
  joined by the umbilical vein and branches into the
  lobes of the liver. The entrance of the postcava
  and precava into the right atrium has already
  been observed.
            C. Heart and Pulmonary
                  Circulation
• Removal of the Heart
• If removal and dissection of the heart is done properly, the
  heart will retain its normal shape and the observations given
  below can be repeated. Keep the heart in the plastic bag with
  your fetal pig for review.
• Determine where the precava enters the right atrium and
  cut this vein. Lift the heart forward to find the postcava and
  cut this vein about 12 mm from the atrium. Find the
  pulmonary veins from the left lung and trace their entry into
  the left atrium. Cut the pulmonary veins, which will expose
  the left pulmonary artery. Cut the left pulmonary artery at
  the surface of the lung. The aorta and its branches are now
  the only remaining vessels attached to the heart. Cut the
  brachiocephalic (innominate) and left subclavian arteries
  between the aorta and their first branches. Cut the aortic arch
  about 25 mm beyond the left subclavian artery, and remove
  the heart from the body.
Flow of Blood through the Heart

• This next part should be done with a
  sheep heart, if available. If no sheep
  hearts are available, make sure you
  know the main structures that reside in
  the heart as well as the flow of blood
  through the heart.
• Find the roots of the precava and postcava. Cut
  through a line connecting them to open the right
  atrium. You can now look directly into the right
  ventricle through the tricuspid valve, which is
  usually open. Make a straight cut through the wall
  of the atrium, the tricuspid valve, and the outer
  muscular wall of the right ventricle. Examine the
  cavity of the ventricle and the remaining flaps of
  the tricuspid valve. Make another cut through the
  ventral wall of the right ventricle and into the
  pulmonary artery in one continuous line.
  Examine the tricuspid valve from behind, and the 3
  semi-lunar valves at the base of the pulmonary
  artery.
• Probe into the right and left pulmonary arteries from the
  pulmonary trunk. The blood passes from the arteries into the lung
  capillaries which unite eventually into the pulmonary veins. Find the
  entrances of the pulmonary veins into the left atrium (on either
  side of the cut ends of the pulmonary arteries). Cut on a line
  between the pulmonary veins, and on through the left atrium, the
  same as you did through the right. Look first at the bicuspid valve,
  usually closed, guarding the entrance to the left ventricle.
• Cut through the bicuspid valve and the outer wall of the left
  ventricle to the tip of the heart. You must look behind the remaining
  wall of the bicuspid valve to see the entrance to the aortic arch. Cut
  through this valve and on out through the wall of the aorta. Note in
  the base of the aorta, the 3 semi-lunar valves. Just above 2 of
  these valves will be found the openings of right and left
  coronary arteries, which supply blood to the tissues of the heart.
Respiratory System                        Page 6
• The mammalian respiratory system takes in air
  rich in oxygen (inhalation, inspiration) and
  releases air rich in carbon dioxide (exhalation,
  expiration). The exchange of O2 and CO2 in the
  lungs is at the level of the blood capillaries and
  the alveoli (air sacs). Air entering the mouth or
  nostrils passes into the pharynx. The pharynx is
  located at the back of the oral cavity and is the
  region where the food and air passageways
  cross. Air passes ventrally into the larynx and
  food passes dorsally into the esophagus.
                                Procedure
1. To expose the pharynx insert your scalpel into the corner of the mouth and cut back
   to the jaw bone on each side. This cuts the muscles that hold the jaws closed.
2. Separate the jaws by pushing down on the tongue and inspect the oral cavity and
   tongue. The tongue is attached at the back of the oral cavity. Note the small,
   undeveloped teeth in the upper and lower jaws. The ridged roof of the mouth is the
   hard palate, which separates the oral cavity from the nasal cavities. Posterior to the
   hard palate, the roof of the mouth becomes smooth and is called the soft palate.
3. Use your scissors to cut completely through the midline of the lower jaw and tongue.
   This will separate the lower jaw into 2 equal halves. Separate the halves of the jaw
   and examine the posterior region of the pharynx. Find the flap of tissue attached to
   the ventral side of the pharynx. This is the epiglottis and serves to cover the glottis
   (opening of the pharynx into the larynx) during swallowing.
4. Use your scissors to continue the mid-ventral cut into the larynx and trachea.
   Determine the relationship of the larynx to the esophagus. Expose the trachea
   back into the thorax as far as the right lung. Cut the trachea open for a short distance
   in order to see the rings of cartilage in the tracheal wall. These rings serve to hold
   the trachea open.
5. Cut the bronchial tubes (which connect the trachea to the lungs) close to the lung
   and remove the right lung from the chest cavity by cutting any remaining
   mesenteries. Identify at the root of the lung the cut ends of the pulmonary veins and
   arteries and the bronchial tubes. Note the thickness of the wall and the diameter of
   the vessels and tubes. Also, note that the median lobe of the lung, which partially
   surrounds the postcava, is actually a part of the right lung.
               VENTILATION
• Bronchial tubes in the lungs contain smooth
  muscle, but no skeletal muscle, therefore, the
  expansion and contraction of lungs during
  breathing results from movement of the ribs,
  diaphragm, and other muscles.
• During inspiration the thoracic cavity is expanded
  by:
• Contraction of the intercostal muscles between the
  ribs. Contraction of these muscles enlarges the thoracic
  cavity by lifting the ribs upward and outward.
• Contraction of the muscles of the diaphragm.
  Contraction of these muscles lowers the diaphragm to
  enlarge the thoracic cavity. The enlargement of the
  thoracic cavity results in decreased air pressure in the
  lungs. Air enters the lungs from the outside to equalize
  the pressure.
• During expiration the thoracic cavity returns
  to normal by:
• Gravity, which pulls the ribs down when the
  intercostal and diaphragm muscles relax.
• Contraction of the abdominal muscles (and
  certain chest muscles other than the
  intercostals), which force the diaphragm up and
  the thoracic cavity down. Rapidly exhale some
  air in order to feel the chest constrict and the
  abdominal muscles tighten.
Digestive System                    Page 7
• The mammalian digestive system is
  concerned with processing and absorbing
  food and water for the body. The system
  begins with the mouth and ends with the
  anus. Ingested food is digested and the
  products are absorbed in the digestive
  tract; undigested material is expelled from
  the anus.
                         Procedure
1. Examine the region of the pharynx - locate the origin of the
   esophagus and follow it posteriorly. Cut through the diaphragm
   to find the point where the esophagus joins the stomach. The
   sac-like stomach is a somewhat J-shaped organ. It is divided
   into 2 regions; a larger cardiac region into which the
   esophagus opens and a smaller pyloric region which opens
   into the small intestine.
2. Note the greater curvature of the stomach and open the
   stomach by cutting along this curvature. Examine the stomach
   internally and note that a gross difference between the cardiac
   and pyloric regions is not evident.
3. Cut through the pyloric valve and into the anterior portion of
   the small intestine, the duodenum. Note the heavy muscle in
   the wall of the pyloric valve; this is called the pyloric sphincter.
   This sphincter controls the amount of partially digested food
   passing into the small intestine from the stomach.
4. The first 50-75 mm of the small intestine is
  called the duodenum. Recall that the
  pancreatic duct and the bile duct empty into
  the duodenum. Begin the removal of the
  small intestine by carefully cutting the
  mesentery holding the coils together. This
  will allow a gradual unwinding of the
  intestine. Estimate the length of the small
  intestine in your fetal pig. The small
  intestine in man is approximately 20 feet
  long. The portion of the small intestine
  following the duodenum is the jejunum,
  which is about 2 of the length of the
  intestine. The remainder of the intestine is
  called the ileum.
5. Cut open a short length of the ileum and
  examine the lining. Note that the lining is
  folded to form macroscopic folds. The folds
  are covered with numerous small finger-like
  projections, which are barely visible to the
  naked eye. These projection are called villi.
  The folds and villi serve to greatly increase
  the surface area of the intestine.
6. Locate where the small intestine unites
  with the large intestine. Extending to the left
  of this junction is a blindly ending pouch
  (12-25 mm long), the cecum. Unravel the
  large intestine and estimate the length of
  this portion of the digestive tract.
  Excretory System                    Page 8
• Nitrogenous waste products produced by cell
  metabolism are removed from the blood stream
  by the kidneys. The kidneys, urinary bladder,
  and associated ducts make up the excretory
  system. The process of removing nitrogenous
  wastes from the blood is called excretion.
  Recall that blood is supplied to each kidney by a
  renal artery. The blood leaves each kidney by a
  renal vein.
                             Procedure
1. Remove the left kidney and cut it lengthwise into 2 equal halves. The kidney
   will appear in gross section to be composed of 3 regions: an outer
   granulated region, the cortex; a radially striated layer, the medulla; and an
   inner cavity, the renal pelvis. Each kidney contains over 1 million functional
   units called nephrons (renal tubules). The blind end of each nephron is
   located in the cortex where it forms a cup-like structure called a Bowman's
   capsule. The capsule encloses a ball of capillaries, the glomerulus. A renal
   corpuscle is a glomerulus surrounded by a Bowman's capsule. The
   nephrons extend through the medulla to the renal pelvis where the urine is
   collected.
2. The renal pelvis empties into the urinary bladder through the ureter. The
   ureter runs posteriorly to the urinary bladder. Expose this duct without
   damaging the structures crossing over it. These include the umbilical
   arteries and the reproductive ducts in both sexes, and the ovaries just
   posterior to the kidneys in females. The bladder empties to the outside
   through another duct, the urethra. This duct will be observed when the
   reproductive system is dissected. In the case of the fetus, wastes are
   transported via the allantoic duct to the placenta, where they are removed by
   the mother's blood.
Reproductive Systems                   Page 9
• The reproductive and excretory systems of
  vertebrates have a close connection with one
  another. In the males, the same duct transports
  the sperm and urine. The male and female
  reproductive organs of vertebrates have the
  same embryonic origin; it is during development
  that they become different in structure and
  function. The male and female reproductive
  systems are composed of the sex glands
  (gonads) and their associated ducts and
  glands.
• Each student will be responsible for
  knowing both the male and female
  reproductive systems.
Female Reproductive System

• The female gonads are the 2 ovaries, which are located
  posterior to the kidneys. Each ovary is suspended in the
  abdominal cavity by a mesentery. A small convoluted
  tube, the oviduct, is located lateral to each ovary. This
  tube is also called the Fallopian tube. The oviduct
  continues on each side as a slightly larger tube forming
  one of the 2 horns of the uterus. Pig embryos develop
  in the uterine horns, which become greatly enlarged at
  maturity and during pregnancy. The 2 horns of the uterus
  unite to form the body of the uterus, which lies dorsal to
  the urethra. In humans the fetus develops in the body of
  the uterus and there are no uterine horns.
                           Procedure
1. In order to separate the hind legs, use your scalpel to cut through from
   the ventral midline between the legs,. The cut will pass through muscles
   and through the pelvic bones. Be careful when you are cutting the
   pelvic bone it is easy to cut structures you need to identify. One
   way to do this is to cut half way through the pelvic bone and spread the
   legs apart to break the bone the rest of the way. Then use your blunt
   probe to push away the muscles and other tissue. If you have any
   trouble doing this ask for help from your lab instructor.
2. Three tubes will be exposed which are from ventral to dorsal - the
   urethra, part of the reproductive tract, and the rectum. The urethra
   and the reproductive tract unite about 12 mm before the vulva and form
   a common passage, the vestibule (urogenital canal). The tube
   connecting the vestibule and the body of the uterus is called the vagina.
3. Open the vestibule and vagina along one side and locate the opening of
   the urethra and the constriction of the vagina at the base of the uterus.
4. Expose the rectum and open it by cutting anteriorly starting with the
   anal opening. Locate the anal sphincter muscle, which is located at the
   distal end of the large intestine. Find the caudal artery which is against
   the spinal column and dorsal to the rectum.
       Operation of the Female
        Reproductive System:
• Ova develop in follicles within the ovaries. When
  fully developed, the ova are released from the
  follicles and enter the oviduct, where fertilization
  may take place. After fertilization, cleavage of the
  zygote begins and eventually the embryo
  becomes implanted in the uterine horn (or uterus
  in humans). The placenta is formed from uterine
  tissue and from 2 extraembryonic membranes
  (chorion and allantois) formed by the embryo.
  Fetal development continues in the uterine horn
  (uterus in humans), until birth. During birth, the
  offspring pass through the uterine horn to the
  body of the uterus, to the vagina, and to the
  vestibule on their way out of the body.
   Male Reproductive System
• The location of the male gonads, the testes, depends on
  the age of the fetus. The testes begin their development
  in the same location as the ovaries, but prior to birth start
  to descend into the scrotal sacs (scrotum). They will be
  found somewhere along this path in your fetal pig. The
  sperm ducts (vas deferens) will be seen looping over
  the umbilical arteries and the ureters, and then joining
  together dorsal to the urinary bladder. Posteriorly, the
  sperm duct pass through the abdominal wall on either
  side of the midline via the inguinal canals. Identify
  these structures before you complete the following
  procedure.
                                Procedure
1. Cut through the skin of one of the scrotal sacs and extend the cut to the point find
   where the sperm duct leaves the abdominal cavity. This will open the inguinal
   canal and the testis will be exposed.
2. Open the sac that surrounds the testis. The convoluted tubule looping around the
   testis is the epididymis, which empties into the single sperm duct.
3. Cut through the skin slightly to one side of the ventral midline to expose the slender
   penis extending from the anal region to the urinary orifice. The central tube of the
   penis is the urethra. This tube arises from the urinary bladder.
4. To expose the remaining structures of the reproductive system, it will be necessary
   to cut through the tissues in the midline between the legs and break the pelvic bone
   (refer to step 1 for the female reproductive system). The legs can be spread
   apart as the cut is deepened to the level of the urethra. The urethra appears
   somewhat thicker in males than in females due to the presence of accessory
   glands that are closely associated with the urethra. The Bulbourethral glands,
   which are about 12 mm long, are lateral to the urethra. The seminal vesicles are
   located where the ductus deferans and the urethra unite.
5. Dissect the urethra and the accessory glands away from the rectum to determine
   where the sperm ducts enter the urethra. The urethra transports both sperm and
   urine in the male reproductive system.
6. Expose the rectum (which is located just dorsal to the urethra) and open it by
   cutting anteriorly starting at the anal opening. Locate the anal sphincter muscle
   which is located at the distal end of the large intestine. Is it possible to find the small
   caudal artery which is located against the spinal column and dorsal to the rectum?
        Operation of the Male
        Reproductive System
• In the male reproductive system, sperm
  (spermatozoa) are formed in the seminiferous
  tubules of the testes. Sperm produced in these
  tubules are stored in a connecting tubule, the
  epididymis. The sperm, together with secretions
  from the accessory glands (Bulbourethral
  glands, seminal vesicles), form the semen.
  Semen is released via the urethra in a process
  called ejaculation. After the semen is deposited
  in the vagina of the female, some of the sperm
  eventually reach the distal end of the Fallopian
  tube where fertilization of the ova may take
  place.
Female reproductive organs
   Nervous System                          Page 10
• The nervous system is made up of the central nervous
  system (brain and spinal cord) and the peripheral
  nervous system (cranial, spinal, and autonomic nerves).
  The nervous system can be subdivided into 2 distinct parts
  based on function. One part of this system is the somatic
  (voluntary) nervous system. It is under conscious control
  and is composed of nerve cells of the brain, nerve cells
  receiving stimuli from major sense organs, and nerve
  cells that stimulate striated muscles. The other part of
  the nervous system is the autonomic nervous system,
  which is not under voluntary control. The autonomic
  system controls activities such as digestion, excretion,
  secretion, and circulation. The organs that are controlled
  by this system are the heart, smooth muscles, and
  glands. Activities of these organs are also influenced by
  hormones.
• The autonomic nervous system is subdivided
  into the sympathetic and parasympathetic
  nerve systems. Both of these systems innervate
  the internal organs, and the actions of these 2
  systems oppose one another. In general, the
  sympathetic nervous system stimulates the heart
  and decreases the activity of the digestive
  system and associated organs. On the other
  hand, the parasympathetic system tends to
  decrease heart activity and stimulate activity of
  the digestive system and associated organs.
• Procedure
• First remove the remaining skin from the head and
  neck of your pig and cut off the ears. Remove what
  remains of the upper and lower lips.
• Turn the pig on its side with the left side up.
• Dissect away the membrane of the dorsal surface
  of the lower jaw in order to see the teeth still
  present in the jaw. Remove one of the teeth and
  note that the cavity of the tooth is filled with a jelly-
  like substance.
• The top and side of the skull must be
  removed to see the brain. Start at the top of
  the skull and carefully remove the bone, a
  small piece at a time. In order to keep the
  brain from being damaged, free the tough
  covering of the brain from the skull bone
  before it is completely broken away. The
  coverings of the brain are called the
  meninges. The tough outer layer is the
  dura mater. The finer inner layer, which
  closely follows the contours of the brain, is
  the pia mater.
• Several bones of the skull will be identified at this
  time. A pair of frontal bones are located
  immediately between the orbits (a single bone in
  man). Posterior to the frontal bones are the
  parietals. The cerebrum of the brain is
  underneath the frontal and parietal bones. The
  cerebrum is composed of 2 cerebral
  hemispheres. The nasal bones are anterior to
  the frontal bones and cover the olfactory organs.
  Parts of the sphenoid bone will be removed in
  the region of the orbits as well as the temporal
  bone, which is posterior to the orbits. The
  occipital bones make up the posterior region of
  the skull. It will be necessary to remove the neck
  muscles to expose and remove the occipital
  bones. The cerebellum and medulla regions of
  the brain are located underneath the occipital
  bones.
• Identify the skull bones listed above on the human
  skeleton located in the room. Refer to the figure of a
  human skull provided.
• Make a vertical cut in the olfactory organ after the nasal
  bones have been removed. The numerous folds of
  olfactory organ are covered with sensory epithelium. Cut
  into one of the nasal cavities from above and follow the
  cavity posteriorly to the olfactory organ and then to the
  pharynx.
• Following exposure of the cerebrum, cerebellum and
  medulla, cut the brain into 2 equal halves and remove
  the left half. It is now possible to observe the relationship
  of the brain stem (including the medulla) to the cerebrum
  and cerebellum. The pituitary gland, which is located in
  a small pit in the floor of the skull, may be observed
  immediately in back of the optic nerves.

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:181
posted:11/9/2011
language:English
pages:126