LAB: Vertebrates Survey Part A
OVERVIEW
In this laboratory exercise, the anatomy of vertebrates will be examined in some detail. All animals are vertebrates,
which means that many aspects of their structural organization are common with all other vertebrates, including
humans. The similarity of structures among related organisms shows evidence of common ancestry. In a way,
studying these animals is like studying a human. As the leading theme of this lab, ask yourself: for every structure
observed, there is an equivalent structure in your own body - what is the structure and where is it located. We will
concentrate on the organ systems. Pay particular attention to the relationships among organs and groups of organs.
Structural parts are not "just there" in random locations. Their specific layout within the body contributes to making
certain functions possible. Therefore, for every structure seen, you should determine the following:
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What organ system it belongs to
How it is connected with other components
Its general function
Its specific function (if applicable)
You will examine a pigeon, rat or cat and investigate the Circulatory System, Muscular System including
examining the Heart in close detail, the Digestive System, Urogenital System and Respiratory Systems. All
members of this group represent the Phylum Chordata, Subphylum Vertebrata and share certain features of body
form and organization. All members exhibit bilateral symmetry, with one side of the body being essentially a
mirror image of the other. The body is also divided longitudinally into successive regions. These regions are: 1)
the head, where all major sense organs, brain, mouth and associated structures are located; 2) the trunk, the main
body of the animal which terminates in the region of the anus; and 3) the tail, a post-anal extension of flesh and
skeleton which lacks any part of the gut. Tails can function for propulsion (e.g., fish, whales, crocodiles), for
balance (kangaroos, birds, lizards), or for thermoregulation and display. A few forms (e.g. frogs, apes, humans)
have lost their tails except for a few vestigial vertebrae. In addition vertebrates have limbs.
We will be comparing animals from two different classes, Class Mammalia and Class Aves. The bird is a
vertebrate whose body plan is adapted to its requirements for flight. For example, the skeletal system is
lightweight and very strong. The flight muscles of the chest may make up one fifth of the total mass of a
bird's body. Birds have enormous energy requirements because of their high metabolic rate. The unique
air sacs of their respiratory system provide them with a continuous supply of oxygen. In this
investigation, you will be exploring some of the unique structural features of the bird
The classification of the Cat
( Felis domesticus)
The classification of the Rat
( Rattus norvegicus)
The classification of the Pigeon
(Columbia livia)
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class Mammalia
Order
Family
Genus Felis
Species domesticus
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class Mammalia
Order Rodentia
Family Muridae
Genus Rattus
Species norvegicus
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class Aves
Order Columbiformes
Family Columbidae
Genus Columbia
Species livia
OBJECTIVES
Before doing this lab you should understand:
 What an organ is.
 How various organs in a system connect to one another
 The basic functions of the Circulatory, Respiratory and Digestive systems
 General Concepts of Muscle structure and function
 The three types of muscle tissue, their structure and role in physiology
After doing this lab you should be able to:
 Identify the ways in which the Organ Systems of the specimens are characteristic of the Subphylum
vertebrata
 Identify the ways in which the Organ Systems of the specimens are distinctly characteristic of the
environment in which they live.
 Relate the different tissue and organ structures to the functions they have in systems
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Identify and learn the anatomical structures of vertebrates.
Relate specimen anatomical structures to human anatomical structures.
Relate specimen and human anatomical structures to their functions.
Identify the ways in which the structures of the specimen’s Class are distinctly characteristic of the
environment in which they live.
Recognize adaptations of the specimen Class from the characteristic Mammalian Chordate human
anatomy
EXERCISE 1: External Anatomy --Examine the external anatomy and locate all the bold faced
vocabulary listed below.
Head, Trunk and Limbs
The principle body divisions are the head, trunk and limbs. The head bears three pairs of
prominent sense organs, namely, eyes, nose, and ears.
The vertebrate body is divided into six anatomical regions: Locate each of these regions in your specimen
cranial region - head
cervical region - neck
pectoral region - area where front legs/ wings attach
thoracic region - chest area
abdomen - belly
pelvic region - area where the back legs attach
Mammals-The cat/rat are good representatives of the class Mammalia. All members exhibit bilateral symmetry. The body is
also divided longitudinally into successive regions. Mammalian digits (toes) are usually tipped with claws, hooves
or nails. Mammals are animals with mammary glands. Both these specimens have two rows of about five
mammary glands each.
1. Note the hairy coat that covers the cat/rat and the sensory hairs (whiskers) located on the cat/rat's face, called
vibrissae.
2. Note the eyes with the large pupil and the nictitating membrane found at the anterior corner of the eye. This
membrane can be drawn across the eye for protection. The eyelids are similar to those found in humans.
3. The ears are composed of the external part, called the pinnae, and the auditory meatus, the ear canal.
4. Locate the teats on the ventral surface. Check a rat of another sex and determine whether both sexes have
teats. If working with cat compare the differences between the two specimens. Does the difference make sense?
5. Examine the tail, note the presence or absence of hair.
6. Locate the anus, which is ventral to the base of the tale.
7. On female, just posterior to the last pair of teats, you will find the urinary aperture and behind that the vaginal
orifice which is in a small depression called the vulva.
8. On males, you will find a large pair of scrotal sacs which contain testes. Just anterior to the scrotal sacs is the
prepuce, which is a bulge of skin surrounding the penis. The end of the penis has a urogenital orifice, where both
urine and sperm exit.
Aves—The features that best distinguishes birds from all other vertebrates are the presented feathers,
wings and beaks.
1. Note the upper beak is the Maxillary and the lower beak is the Mandible. Both are covered by a horny sheath
that grows continuously and is worn down with use.
2. Note the eyes with the large pupil and the nictitating membrane found at the anterior corner of the eye. This
membrane can be drawn across the eye for protection and is used by diving birds as a “contact lens”, providing
clarity of vision while under water.
**Record the distinguishing difference between Birds and humans regarding the eye in your notebook
3. The ears are located posterior to the eyes. Brush the feathers away from the ear coverts forward to find the
external ear openings.
4. Locate the Uropygial gland. The external duct of the oil gland is located by brushing the feathers of the rump
forward. When preening, a bird will use oil squeezed from this duct by its beak, to weatherproof its feathers.
Water-birds tend to have large uropygial glands. Birds from drier habitats tend to have reduced or absent glands.
5. Examine the tail, the tails the presence or absence of hair.
6. Locate the Cloaca, which is ventral to the base of the tale. This is the common opening for the voiding of waste
materials and release of gametes (sperm and eggs). The external most portion of the cloaca is called the vent.
7. Examine the lower limbs, notice that the bulk of the muscle mass is in the first two segments. This is an
adaptation favoring aerodynamic contouring. The unfeathered portion of the lower leg is an elongated and fused
anklebone. Along this anklebone (tarsometatarsus) run the tendons that extend and flex the toes.
8. Examine the wings, notice the different types of feathers and their locations and characteristics.
Questions:
a. List five characteristics that are distinctively different from humans. Briefly describe why
these characteristics are needed by the Cat/Rat/Pigeon and not humans.
b. For mammals determine the sex of your specimen. For aves recored the distinguishing
difference between humans and birds discovered when examining the eyes (note this is not
one of your 5 characteristics in a. above.
Upon completion of the external examination you can begin skinning in preparation for dissection.
EXERCISE 2:
Skeletal System
1. Examine the Skeleton Diagrams provided. Locate and identify the following bones:
Mammals –
sternum
Cranium
Forelimb (humerus, radius, ulna,
digits/metacarples)
Aves – the above and Additional bones
Furcula
Coracoid
Mandible
clavicle and scapula Vertebral column
and ribs
hind limb (femur, fibula, tibia, digits)
Keel
Ischium
The avian skeleton has become dramatically modified to facilitate flight. In most bird species, bones have become
pneumatic, that is, they have cavities filled with air. Bones of the limbs have become elongate, and those of the tail
shortened. Pelvic bones, as well as finger bones, are fused to provide rigidity and strength needed for flight. The
sternum is keeled to anchor large flight muscles. A keel is a crest of bone that arises from the sternum. Some
flightless have no keel or a reduced one. To prevent collapse of the thoracic cavity during flight, a tripod of paired
bones, capula, coracoid, and furcula are required.
2. Examine the human skeleton in the class and provided diagrams. Locate and identify the same bones
Questions:
c. Mammals – How do the relative sizes and positions differ between human bones and the cat/rat’s?
Select a particular bone of interest in both species and make a sketch of the human and cat/rat bone.
Write a description of the differences and the advantages the differences have for each species.
Aves – How do the relative sizes and positions differ between human bones and the pigeon? Select a
particular bone of interest in both species and make a sketch of the human and pigeon bone. Write a
description of the differences and the advantages the differences have for each species.
Upon completion of the external examination and skeletal comparisons you can begin skinning your
specimen in preparation for dissection.
EXERCISE 3:
Integumentary System – Skin
During this Exercise pay close attention to the changes in thickness and structure of the skin.
Pigeon skin removal – For birds the skin and feathers may be removed together but be very careful that
the small dermal muscles in the region of the wing are not destroyed. The large contour feathers of the
wing and tail should be clipped short and the bases left attached to the wing and tail.
Place the bird on your dissection tray ventral side up. Par the feathers mid-ventrally to expose the bare
skin. By running your finger from anterior to posterior between the now parted feathers you should be
able to feel the bonny ridge. This is the keel that anchors the large flight muscles.
Carefully with your scalpel make a very shallow incision along the keel. You only want to cut through
the skin, not the muscle. The incision (#1) should extend mid-ventrally from the anterior of the keel
posterior to an area just superior to the vent. By alternately using a blunt end probe and forceps,
connective tissue holding the skin to the body can be loosened. Transverse incisions can be make across
the anterior most portion of the pectoral region (#2) and the lower abdomen (#3) Fig 2: Incisions for
skinning. Be careful to cut only through the skin. By continuing the transverse incision along the fleshy
portion of the left wing distally (#4), the ventral area of that limb can be skinned.
The left leg can be skinned by cutting the skin proximally and peeling it away,, as you would remove a
sock. Removing the connective tissue is slow and tedious but necessary to adequately expose intact
muscle
Mammal skin removal - To examine the interior structures of the cat/rat you must first remove the skin,
connective tissue and fat (do this to one side of the body only). Scissors, blunt probe and hands are the
best tools to use. Place the cat/rat ventral side up in the tray. Use your fingers to locate the breast plate
and ribs. Using forceps lift the skin and make a small incision being careful not to cut muscle. Always
work by putting pressure against the skin (proximal pressure) so that you do not tear or cut any of the
muscle tissue. Make a longitudinal cut from the incision point and move caudally along the midline.
Extend this slit anterior into the lower jaw and posterior to the end of the trunk. The white, fibrous tissue
(superficial fascia) connects the skin to the underlying tan colored muscles. Remove skin from one side
of the body including limbs. Removing the connective tissue is slow and tedious but necessary to
adequately expose intact muscle.
Questions:
d. Mammals – Write observations of the differences between skin texture in the different regions of the
body [ dorsal vs ventral, thoracic vs abdominal, truck vs appendages].
Aves – Note the differences in the type and characteristic of the feathers. Write observations of the
differences between skin texture in the different regions based on feather characteristic.
EXERCISE 4:
Muscle System A
To examine the muscle system of the cat/rat you must first remove the skin, connective tissue and fat.
Scissors, blunt probe and hands are the best tools to use. Place the cat/rat on its back. Always work by
putting pressure against the skin so that you do not tear or cut any of the muscle tissue. The white,
fibrous tissue (superficial fascia) connects the skin to the underlying tan colored muscles. Removing the
connective tissue is slow and tedious but necessary to adequately expose intact muscle.
In General for all muscle dissection activity:
1. Always begin at the belly of the muscle to be dissected
2. Transect (isolate) and reflect (fold back) superficial muscles to expose deeper muscles by cutting
the belly of the superficial muscle and reflecting its cut halves towards the muscle’s origin and
insertion respectively.
3. Once the muscles are well exposed, trace their origins and insertions.
4. Identify the ‘Action” of the muscle (use reference tables)
5. Identify (as best you can) the origin bone of the muscles
MAMMALS -Muscle System A --Chest Muscles:
The chest muscles are large and easy to dissect, making the chest a good place to start. In exposing
the deep chest muscles, you will find nerves and blood vessels coming out of the lateral chest wall
and going into the arm. Try to leave all blood vessels and nerves intact unless specifically told to
remove them.
 Transect and reflect the following to expose the deep chest muscles: pectoantibrachialis,
pectoralis major superficial and deep (the superficial is covered by the pectoantibrachialis, to
which it is similar in size and orientation), pectoralis minor, xiphihumeralis, clavobrachialis.
Note: levator scapulae ventralis, pectoantibrachialis, transverse costarum and xiphihumeralis have
no human homologes. Clavobrachialis along with acromiodeltoid and spinodeltoid are
homologous to the human deltoid muscle.
e. Make a sketch of the Cat/rat chest muscles area and label the muscles: pectoralis major
superficial, pectoralis minor and clavobrachialis
Examine the Human Muscle Poster/handouts and locate the corresponding muscles. Try to
determine how these muscles work in your own body.
Questions:
f.
Make a data table of the muscles you sketched. In that table identify the muscle, describe the action
it performs for both cat/rats and for humans?
Muscle System B
Choose one of the following Muscle areas to investigate:
Left fore limb
Left hind limb
Right fore limb
Right hind limb
Remember to:
1. Always begin at the belly of the muscle to be dissected
2. Transect (isolate) and reflect (fold back) superficial muscles to expose deeper muscles by cutting
the belly of the superficial muscle and reflecting its cut halves towards the muscle’s origin and
insertion respectively.
3. Once the muscles are well exposed, trace their origins and insertions.
4. Identify the ‘Action” of the muscle (use reference tables)
5. Identify (as best you can) the origin bone of the muscles
Forelimb muscles –
The dissection of the forelimb muscles requires extra care because they are small and tightly
packed. A tough sleeve of connective tissue tightly covers the forearm muscles and must be removed.
Become fully familiar with the superficial muscles (Cat Fig 21 and 22) before trying the deep muscles
Transect and reflect the following to expose the deep muscles of the medial forelimb (cat fig 23):
triceps (lateral head), brachioradialis, extensor digitorum communis, extensor digitorum lateralis, flexor
carpi ulnaris.
The following must be transected and reflected for the deep muscles of the lateral forelimb (cat
Fig. 24) to be seen: epitrochlearis, palmaris longus, flexor carpi ulnaris, flexor carpi radialis.
The anconeus and epitrochlearis have no human homologues. The extensor carpi radialis brevis,
extensor digitorum lateralis, and palmaris longus are relatively smaller in humans, and the palmaris
longus is missing in about 10% of the human population.
Hind limb muscles –
Dissecting the hind limb muscles presents few problems other than identifying some muscles of
the lower leg. Once the superficial muscles (cat Figs. 25 and 26) are known, transect and reflect the
biceps femoris to expose the deep muscles of the lateral hind limb (cat Fig 27). The delicate tenuissimus
will be torn by this procedure. Do not try to trace the origin or insertion of the tenuissimus as this is
difficult. Transect and reflect the sartorius and gracilis to expose the deep medial hind limb muscles (cat
Fig. 28)
The caudofemoralis and tenuissimus are without human homologues, and the gluteus maximus is
relatively larger in humans.
AVES -The musculature of birds is unusual and highly confusing do to modifications of the bird’s body for flight,
many muscles have changed in their function from that of a typical tetrapod, for example, M.* extensor
metacarpi ulnaris is a flexor of the metacarpals on the radial side (name changed here to M. flexor
metacarpi radialis), and the primary function of m. extensor digitorum communis is to flex the hand. In
addition, many muscles are unique in birds such as M. expansor secundariorium, a skin muscle which is
smooth rather than striated.
Muscle System A --Chest Muscles:
Use great care in your dissectin and do not be misled by unsual attachments or positions of muscles.
Separate the superficial muscles from the deeper structures and cut these muscles halfway between
their origin and insertion. For M. pectoralis, carefully scrape this muscle loose from its surface of
origin on the keel of the sternum. Be careful not to remove M. supracoracoideus which is completely
covered by M. pectoralis.
e. Make a sketch of the Pigeon chest muscles area and label the muscles: M. pectoralis, and M.
supracoracoideus
Examine the Human Muscle Poster/handouts and locate the corresponding muscles. Try to
determine how these muscles work in your own body. In humans these are pectoralis major
superficial, pectoralis minor. Does the bird have a muscle similar to clavobrachialis?
Muscle System B Wing musculature
Remember to:
1. Always begin at the belly of the muscle to be dissected
2. Transect (isolate) and reflect (fold back) superficial muscles to expose deeper muscles by cutting
the belly of the superficial muscle and reflecting its cut halves towards the muscle’s origin and
insertion respectively.
3. Once the muscles are well exposed, trace their origins and insertions.
4. Identify the ‘Action” of the muscle (use reference tables)
5. Identify (as best you can) the origin bone of the muscles
Examine the Pectoralis muscle in more detail
f. Identify the Origen, insertion and action of the Pectoralis muscle