Download BestPigeon_dissection.2013doc

NAME ____Class Copy__________
CLASS: Aves “bird”
ORDER: COLUMBIFORMES (pigeons & doves)
External Anatomy
INTEGUMENTARY/BODY
Modification for flight: FEATHERS provide lift; streamlined for decreased air resistance; insulation against
heat loss; SKIN thin so weighs less
Birds are the only animals with FEATHERS. Feathers are modified scales made of
KERATIN. Their function is to PROVIDE LIFT in flying and PRESERVE BODY
HEAT. Feathers also provide coloration to attract a mate and hide from predators.
Examine your feather carefully: The structure of a feather combines MAXIMUM
STRENGTH with MINIMUM WEIGHT.
Feathers grow from tiny pits
in the skin called FOLLICLES. Two VANES
develop on opposite sides of a center shaft called
the RACHIS. Each vane has many branches called
BARBS. The barbs are zipped together “like Velcro”
by microscopic hooks called BARBULES.
1. Remove a few feathers from a wing. Closely examine a
and identify the rachis, 2 vanes, and barbs.
feather
Birds straighten and care for their feathers by rubbing them with their
beak with oil secreted by a PREEN GLAND (uropygial gland) at the base
of their tail. This action, called preening, weatherproofs feathers.
Birds periodically MOLT or shed their feathers and grow new ones.
2. Locate the preen gland by brushing the feathers of the rump forward.
The fleshy bit of skin that lies over the BEAK is called the CERE.
It covers the EXTERNAL NARES or nostrils. EYES are
protected by upper and lower EYELIDS. The NICTITATING
MEMBRANE is in the anterior corner of the eye and acts as a
third eyelid. External EAR OPENINGS are located posterior to the eyes.
3. Locate the external features listed above. Brush the feathers of the ear coverts (posterior to eyes) forward
to locate external ear openings.
Birds see in COLOR and have keen vision which is important in taking off, landing, spotting
landmarks,
hunting, and feeding. Having eyes on the sides of its head gives a bird a WIDE RANGE OF VISION.
This arrangement is most often seen in birds which may be prey of other animals so they can
watch for predators more easily.
Birds with both eyes on the front of their head
have better BINOCULAR vision (DEPTH PERCEPTION) a necessity for
hunting. This arrangement is most often seen in birds that are predators such
as owls, hawks, and falcons.
Hearing is important to songbirds and in nocturnal birds
that must hunt for prey in the dark. Birds lack external
ears and have their TYMPANIC MEMBRANE inside.
4.
The CLOACA is the common opening for the voiding of waste materials and release of gametes (sperm
and egg). The external most portion of the cloaca is called the VENT. Locate the VENT on the
posterior end of the bird.
5. Observe the lower limbs (legs) and feet. The lower limbs and feet vary greatly in birds depending upon
the environment of the bird (webbed feet of ducks, talons of eagles, etc.)
Internal Anatomy
6.
Place the pigeon ventral side up in your dissecting tray. It may be easier to pluck the feathers from the
entire chest area from the crop to the cloaca / vent so it will be easier to make incisions and remove
the skin. However, plucking takes a while and is a pain so it may just be easier to make incisions and skin
the bird with feathers still on. If you decide to pluck, all feathers must be picked up and discarded
properly.
7. Time to skin your bird. Feel in the center of the
chest area for the KEEL or bony ridge. The keel is
the crest of bone that arises from the STERNUM.
It runs the entire midline of the chest. Make an
incision through the skin running along the keel
from the anterior portion of the keel just superior
to the vent. Only cut through the skin and not the
muscle. You may have to use forceps to pull the
skin from the muscle (connective tissue holds the
skin to muscle).
8. Make transverse or perpendicular incisions across
the anterior most portion of the chest and just
superior to the vent. Again, be careful to only cut
through the skin and not the muscle. Pull the skin
from the muscle tissue so the entire pectoralis major can be seen. See the image to the side.
9. Also make incisions to partially skin one upper leg and one wing. Remove the skin from these to see the
major muscles of these limbs. Do not skin the entire leg or wing, just the “fleshy” or muscular areas.
10. Use a scalpel to cut through one half of the chest muscle. Locate the keel. Just to one side of the
keel, make an incision mid-ventrally from the anterior portion of the keel towards the vent. You are
cutting through two major muscles. Note their thickness. The pectoralis lies above the
supracoracoideus. The pectoralis controls the downward stroke of the wing while the supracoracoideus
controls the upward stroke. On the same half of the bird, cut around the chest moving laterally from
the midline. Carefully carve the chest muscle away from the sternum.
11. To view the internal anatomy, we must remove the sternum. Make an incision from the posterior end of
the sternum or keel towards the vent cutting only through the thin layer of skin and muscle. From this
incision make incisions left and right laterally just anterior to the vent. Make incisions completely
around the remaining chest muscle and sternum. Be careful not to cut through and damage internal
organs.
12. The easiest way to remove the sternum is to insert 2 fingers underneath its most posterior end, holding
the thumb firmly on the top surface and bending it backwards up toward the head of the bird until you
hear the ribs break (it sounds disgusting, but it works). You may have to use scissors to cut through
some ribs to eventually remove the entire sternum.
13. Broken rib bones may be sharp. Be careful. Cut away any rib bones that may be sticking up or out. Pin
back any other skin or muscle to view the internal anatomy.
DIGESTIVE
The large amount of energy needed to fly and regulate body
heat (ENDOTHERMIC) is obtained by a quick and efficient
digestive system.
Birds have NO TEETH to chew their food before it passes
down the ESOPHAGUS into the CROP which stores food
waiting to be digested. Birds have a TWO PART STOMACH
to speed digestion. In the first chamber, the
PROVENTRICULUS, acid and digestive enzymes begin
breaking down the food. The second muscular portion called
the GIZZARD contains small rocks the bird has swallowed
which help in GRINDING the food.
Food is then passed into the very long SMALL INTESTINE
where digestion is completed and nutrients are absorbed.
The short LARGE INTESTINE absorbs water from and
concentrates digestive waste.
The COLIC CAECA are found at the junction of the small
and large intestine. These small pouches contain bacteria
that AID IN DIGESTING PLANTS. Digestive waste is
mixed with urine containing URIC ACID in the CLOACA
before exiting through the VENT. The LIVER and
PANCREAS still provide digestive enzymes
14. From anterior to posterior, locate the following organs.
 The esophagus lies dorsal to the trachea (tube that carries gases to and from lungs)
 The crop (sac structure that may hold food)—go ahead and cut open the crop to see if it is
storing any food.
 Liver—two large lobes; largest organ in a bird. Gall bladder is in between two lobes. Remove
liver and gall bladder once it has been correctly identified.
 Proventriculus
 Gizzard—this can also be opened (see teacher for instructions) to see contents
 Intestines
 The pancreas is an elongate organ found in close proximity to the intestine and liver.
 Colic caeca
15. After all digestive organs have been identified, you may have to remove some to study other internal
organs. Make sure to remove only digestive organs if need be. There are numerous air sacs that part of
the respiratory system. Be careful and try not to remove these. Remember the esophagus is
underneath the trachea.
Modification for flight:
2 part stomach to speed food through system;
Crop for storage allows birds to eat when stomach is full so food is always moving
through digestive system;
Food fuels high metabolism (ENDOTHERMIC) so more energy for extended activity
Excess food stored as FAT for energy during long flights (migration)
Long SMALL INTESTINE to absorb lots of nutrients
Short LARGE INTESTINE to get rid of digestive waste faster
such as flying
RESPIRATORY
Birds have the MOST EFFICIENT respiratory system of any terrestrial
vertebrate. Rapid metabolism requires an abundant supply of oxygen. Yet
some birds migrate thousands of miles at high altitudes (up to 23,000 ft)
where oxygen levels are very low.
Air enters through EXTERNAL NARES at the base of the beak and
moves into the TRACHEA through the GLOTTIS opening in the back of
the mouth cavity.
The air moves down the TRACHEA and branches into two BRONCHI (sing. BRONCHUS). From there
SOME OF THE AIR ENTERS THE LUNGS. However, about 75% of the air bypasses the lungs and flows
directly into the POSTERIOR AIR SACS that extend from the lungs and occupy a large portion of the
bird’s chest and abdominal cavity (COELOM). These sacs also extend into some of the LONG BONES, so
they function in RESPIRATION and also REDUCE THE DENSITY of the bird.
GAS EXCHANGE DOES NOT OCCUR IN THE AIR SACS. Their function is to STORE AIR. When the
bird exhales the LOW OXYGEN AIR from its lungs moves into the ANTERIOR AIR SACS and the HIGH
OXYGEN AIR from the posterior air sacs moves into the lungs. This way, the bird has high oxygen air in
its lungs at all times… both on the INHALE and on the EXHALE! ALVEOLI in the lungs increase surface
area for greater gas exchange.
The SYRINX (voice box), which produces sound, is a diamond shaped organ located where the trachea
splits into the 2 bronchi. By regulating the flow of air birds can produce songs of great range and
complexity. Male birds sing to warn away other males and to attract females.
16. Identify the trachea, bronchi, and two lungs. Also identify various airsacs. If need be, remove any of
the respiratory structures to identify and locate other internal organs.
Modification for flight:
SUPER EFFICIENT respiratory system to meet HIGH OXYGEN DEMAND
AIR SACS allow oxygenated air in lungs during both INHALE and EXHALE
to provide more oxygen during high activity (flight)
AIR SACS from lungs extend into bones to decrease density
ALVEOLI in lungs increase surface area for more gas exchange
CIRCULATORY
Birds have a CLOSED CIRCULATORY SYSTEM with 2 LOOPS (Pulmonary and Systemic) just like
amphibians & reptiles. The difference in birds is the COMPLETE SEPARATION of the ventricle by a
SEPTUM into a 4 CHAMBER HEART (2 atria and 2 ventricles). The SINUS VENOSUS and CONUS
ARTERIOSUS have disappeared.
The LARGEST VEIN returning to the heart is the VENA CAVA. The largest arteries carrying blood away
from the heart are the PULMONARY (to LUNGS) and the AORTA (to BODY).
Compared to reptiles and most other vertebrates, birds have a RAPID HEARTBEAT.
Like amphibians and reptiles the SPLEEN still makes, stores, and recycles red blood cells. Like reptiles
and amphibians, bird red blood cells HAVE NUCLEI. Human RBC’s don’t.
17. Identify the heart. Try to identify the aorta extending superior of the left atrium. The pulmonary
veins enter the left atrium. Identify the inferior and superior vena cava, veins entering the right
atrium. Identify the pulmonary arteries extending from the right ventricle heading to the lungs.
18. Remove the heart and cut open the heart identifying the two atria and two ventricles.
Modification for flight:
Heart large for size of body
4 chamber heart (SEPTUM totally separates ventricle into 2)= most efficient/faster
2 loop system faster/gives extra push to blood going to body
RAPID HEART RATE moves oxygen/nutrients to body faster
REPRODUCTIVE
In males sperm is produced in the TESTES near the kidneys. Sperm passes through a small tube called
VAS DEFERENS (plural: VASA DEFERENTIA) into the CLOACA.
During mating the male presses his cloaca against the female’s cloaca and releases sperm. Most females
have a SINGLE OVARY ON THE LEFT SIDE of the body.
19. Locate the gonads (testes or ovary). They are ventral and anterior to the kidneys. You may have to
remove digestive organs to locate these remaining organs. Attempt to locate the vas deferens (male) or
oviduct (female).
Eggs are heavy! Having a single ovary lightens the load for flying! Birds lay AMNIOTIC EGGS. The
OVARY produces the eggs and the albumen and shell are added in the OVIDUCT, just like in a turtle.
Eggs pass through the CLOACA and VENT and are laid outside the body. CALCIUM CARBONATE makes
the shell hard so birds can sit on the eggs to keep them warm.
Most birds lay eggs in nests. Nests hold eggs, conceal
young birds from predators, provide shelter from the
weather, and sometimes attract a mate. One or both
parents incubate,(WARM) the eggs by sitting on them. A
thickened,featherless patch of skin on the abdomen called a
BROOD PATCH, allows skin to egg contact for more warmth.
In birds in the ORDER Columbiformes (pigeons & doves) the
crop in both males and females secretes a nutritious milklike fluid called CROP MILK to feed the young.
Birds that lay eggs in nests on or near the ground where
they are more vulnerable to predators have PRECOCIAL
YOUNG (babies that can walk, swim, and feed themselves shortly after birth). This allows the baby birds
to be mobile sooner and increases chances for survival by better escaping predators. Birds that lay eggs
in nests higher up in trees or places where predators can’t reach as easily have ALTRICIAL YOUNG
(babies that are featherless, blind, and helpless which must be fed and cared for by the parents). This
kind of baby would quickly be eaten if it was laid in a nest on the ground! Hatching these kind of babies
up high protects them until they are more mature.
Modification for flight:
Females have OVARY and OVIDUCT on only 1 side (less weight)
Ovary enlarges during breeding season; shrinks in size rest of year
OVIPARITY = Lay eggs outside (less weight if egg NOT kept in body)
EXCRETORY
The avian excretory system is lightweight and
efficient. The excretory organs in birds are the
KIDNEYS. These elongated brownish organs are
located along the back body wall under the
reproductive organs on either side of the spinal
cord. The kidneys REGULATE ION/WATER
BALANCE of blood and tissues and REMOVE
NITROGEN WASTE. Unlike other vertebrates,
birds DO NOT STORE URINE… there is NO
URINARY BLADDER! The kidneys filter nitrogen
waste from the blood in the form of URIC ACID.
This form is the LEAST TOXIC and
REQUIRES THE LEAST AMOUNT OF WATER
TO
DILUTE. Concentrated uric acid waste moves through ducts called URETERS to the CLOACA, where it mixes
with digestive waste and is eliminated through the VENT. Bird droppings are a mixture of feces and uric acid
(the white colored material you see in “bird poop”).
20. Locate the paired tri-lobed kidneys that are located dorsal to the lungs. Attempt to locate the ureters
that extend from the kidneys to the cloaca.
Modification for flight:
No Urinary bladder = less weight
Nitrogen waste eliminated as URIC ACID (needs the least water to dilute);
Waste eliminated as made/ No urine storage
NERVOUS
21. To examine the brain, place the pigeon on its ventral side. Make a sagittal incision through the skin, from
the cere to a pint just posterior to the base of the skull. Make lateral (perpendicular) incisions at the base of
the skull. Pull away the skin revealing the skull of the bird. Carefully, with scissors and scalpel, remove the skull
revealing the brain.
Modification for flight:
Large BRAIN for body size = “smarter”
Bigger CEREBRUM allows more complex behavior
(problem solving; learning; navigation; nesting; nest building; caring for young)
Bigger CEREBELLUM for muscle coordination during flight
Bigger OPTIC LOBES for better vision; color vision
Concentration of IRON in brain of migrating birds to detect magnetic fields
(acts like a compass)
SKELETAL
Modification for flight:
Bones = thin & HOLLOW; Many bones are FUSED for strength;
AIR SACS from lungs extend into some bones making them less dense
PYGOSTYLE (fused lower vertebrae) support tail for lift & braking during flight;
FURCULA (fused collarbones) stabilize shoulders during flight;
STERNUM (large breastbone) to attach flight muscles
Bird bones are hollow to make them less dense than
bones of non-flying animals.
Some bones (FURCULA, PYGOSYTLE) are fused
to make them stronger.
MUSCULAR
Modification for flight:
Large PECTORAL muscles attach to
sternum and power wings
ENDOCRINE
Modification for flight:
THYROID maintains HIGH METABOLISM (burns glucose) to provide energy for flight
PANCREAS (makes INSULIN & GLUCAGON) regulates blood sugar levels so fuel is
available for flight
ENDOTHERMIC metabolism provides energy for extended activity (flight)
NAME ________________________
BIRD LAB OBSERVATION SECTION
KINGDOM: _______________________
PHYLUM: ________________________
SUBPHYLUM: _____________________
CLASS: ______________________
ORDER: ______________________
COMPARE THE CIRCULATORY SYSTEMS IN BIRDS, REPTILES, AND FISH
BIRD
Reptile
Fish
# LOOPS ?
# of heart chambers ?
Number of
Atria ? Ventricles?
___ atria
___ ventricles
____ atria
____ ventricles
____ atria
____ ventricles
Blood returning from lungs
enters ?
Blood returning from body
enters ?
Tell 2 ways the respiratory system in birds is different than in other animals with lungs?
1. Birds have ______________________ in addition to lungs.
2. Birds move oxygenated air into their lungs both when they __________________ & when they
__________________
Birds excrete their nitrogen waste as:
AMMONIA
UREA
URIC ACID
Which part does it?
Stores and moistens food waiting to be digested
First chamber of “stomach” where acid &
digestive enzymes begin to break down food
2nd part of the “stomach” that contains small
rocks to grind and mash the food
__________________________
____________________________
___________________________
Small gland near tail that makes oil used to keep
the bird’s feathers in good condition
____________________________
Small pouches which contain micro-organisms
that help to digest plant material
___________________________
Multipurpose exit cavity that receives digestive waste,
urine, and sperm/eggs before leaving the body
_______________________
Fleshy patch of skin above the beak in a bird
______________________
Dividing wall that separates the ventricle into two
______________________
Tubes that carry sperm from testes to cloaca
________________________
Tubes that carry urine from kidneys to cloaca
________________________
Tubes that carry eggs from ovary to cloaca
________________________
Gland that regulates heart rate and metabolism
________________________
Largest vein returning to heart
_______________________
Largest artery leaving heart
_______________________
Featherless patch of skin on the abdomen that helps to keep eggs warm________________________
Small sacs inside the lung that increase surface area
for more gas exchange
_______________________
Large extensions off the lungs that store air but don’t exchange gases _________________________
Removes uric acid from blood and dilutes it to make urine
_____________________________
“Eardrum”
_____________________________
3rd eyelid that acts as goggles
_____________________________
Osmoregulation
__________________________________
Make bile, store vitamins & glycogen, process toxins
Make trypsin, insulin, & glucagon
________________________
______________________________
CIRCLE ALL THAT APPLY TO BIRDS:
VENTRAL nerve cord/DORSAL heart
ACOELOMATES
DORSAL nerve cord/VENTRAL heart
PSEUDOCOELOMATES
2 chambered heart
Ammonia (nitrogen waste)
3 chambered heart
4 chambered heart
Urea (nitrogen waste)
Ectothermic
Indirect development
Uric acid (nitrogen waste)
Endothermic
Direct development
External fertilization
Gills
EUCOELOMATES
Internal fertilization
Lungs
Eggs with shells (amniotic egg)
Oviparous
Eggs without shells
Ovoviviparous
Viviparous
ADAPTATIONS FOR FLIGHT—Fill in the missing adaptation or system
System
1.
Feathers provide lift and increase surface area
2.
Respiratory
3.
Reproductive
Large pectoralis
4.
No urinary bladder to decrease weight
5.
6.
Adaptation
Skeletal system
7.
Long small intestine; Short large intestine
8.
Large, 4 chambered heart
Pigeon Dissection
1) Draw the external anatomy of a pigeon on observation section provided below. Label the following structures below. In
addition to drawing the external anatomy, label and tell me the function of the terms below. These will be typed in your formal
lab write up.
1. Preen gland
2. Beak
3. Cere and external nostrils
4. Vent
5. External openings of ears leading to internal tympanic membrane
6. Nictitating membrane
7. Wings
8. Feet
2) Now draw the internal anatomy of a pigeon in the observation paper. Label and tell me the function of the following
structures below. Feel free to use your colored pencils to color the various structures and organs different colors for easy
identification.
1. Liver
11) Brain
2. Crop
12) Gonads
3. Proventriculus
4. Gizzard
5. Colic Caeca
6. Small intestine
7. Large intestine
8. Lungs
9. Kidneys
10. Heart
External Anatomy
Internal Anatomy