CHURCH TEACHERS’ COLLEGE
LAB REPORT ON THE ANATOMY OF A GUINEA PIG
Name: Chevance V. Henry
Date: October 16, 2014
Course: Animal Diversity
Course Code: SC203SEB
Course Lecturer: Tillack Hardeen
TITLE: The dissection of a Guinea Pig
ABSTRACT: This investigation was intended to study the external and internal anatomies of the
Guinea pig. Due to their class Mammalia, which is the same as humans, a comparative study was
necessary to examine the structures and behavioral patterns of the Guinea pig for a greater
understanding of the body systems of mammals. Guinea pigs are very popular pets because of
their availability, docile temperaments, tendency not to bite or scratch when handled and
relatively clean habits. There are lots of different breeds of Guinea Pig and they come in lots of
colors and fur textures. This study has provided useful information on the general characteristics
of mammals. The examination of the external and internal anatomies of the Guinea pig started by
firstly by using chloroform to subdue the organism to allow for an undisturbed observation. The
Guinea pig was then placed on its dorsal and ventral side on a dissecting tray to observe and
identify its external features. A dissection of the Guinea was necessary to fully examine its
internal anatomy. Pictures, measurements and drawings were made of the external and internal
body parts which were identified and labeled. The reasons why these animals are a part of the
class Mammalia were easily identified when the Guinea pig was examined. Their body systems
were quite similar to that of humans and further conclusive study has revealed that their
physiological process occur in the same way.
This investigation serves as a tool to analyze the physiological mechanisms in animals to
understand the dynamics of life and to establish a basic knowledge about the anatomy and
morphology of guinea pig.
Guinea Pigs are rodents related to chinchillas and porcupines that originated from the Andes
Mountains region of South America. Their scientific name is 'Cavia Porcellus' and so they are
called 'Cavies' for short. Guinea pigs belong to the Phylum Chordata, Class Mammalia and Order
A Guinea Pig is a small and measure 20 to 40 cm from head to rump. It is a burrowing rodent
that has a compact body. Guinea pigs have small ears and eyes, a small snout with sensory
whiskers each side and no tail. Like most rodents, they have two gnawing teeth at the front
which continue to grow throughout their life. Because these teeth are continuously growing, it is
very important that Guinea Pigs have something to gnaw on to help keep the teeth trim. Guinea
Pigs have short legs and little feet with claws on. Their front feet have four toes or claws;
however, their back feet have only three.
Se ns e s
Adult guinea pigs seem to be able to discern brightness, but not hue. Young are born with their
eyes open, but studies suggest that their vision is poorly developed at birth. Scent plays a role in
guinea pig communication, and mother guinea pigs use it to identify their young. Guinea pigs
can hear sounds of up to 40,000 to 50,000 Hz, and some guinea pig vocalizations have ultrasonic
components above 20,000 Hz.
The wild relatives of guinea pigs have ticked grey coats similar to that of Shadow. Breeding
guinea pigs for research and show has produced many combinations of coat colour, length, and
quality. Common colours include white, brown, black and combinations thereof. Guinea pig fur
may be long or short, straight, frizzy or curly, soft and silky or rough and harsh, and it may lie
smoothly or in rosettes.
Guinea pigs are most active at dawn and dusk, but they are active throughout the day. Under
conditions of constant light and cool temperature, they do not appear to have fixed sleeping or
Social Be havior
As social animals, guinea pigs will seek contact with one another and tend to associate in groups
of several to several dozen if given the opportunity to do so. They investigate unfamiliar guinea
pigs by nose-to-nose contact and anogenital nuzzling. Guinea pigs interact and socialize with
their caregivers when kept as pets. For example, they may chirp at their caregiver to ask for food.
In groups of guinea pigs, males have a linear hierarchy. The alpha male has exclusive rights to
mating with the females in his group, and will not tolerate other males attempting to mate with
his females. Females are subordinate to their male, and they may have a loose social hierarchy
Guinea pigs are quadrupedal. They walk and run on the soles of their feet . Young guinea pigs
play by "popcorning", that is, by jumping, bucking, and throwing up their heads. In response to
danger or fright, guinea pigs will either freeze or run away. Groups of guinea pigs may respond
by suddenly scattering in all directions.
Communi catio n
Guinea pigs communicate with one another by making sounds. They produce a variety of
vocalizations that go along with certain activities. For example, a guinea pig will "chutt" when
exploring, "whistle" when fed by a caregiver or when separated from a companion, and "purr"
when seeking contact. Guinea pigs also use scent to communicate. Scent from adanal glands may
be used to mark territory. In courtship, an unreceptive female will sometimes squirt a jet of urine
at the persistent male, who then sniffs it. While the male investigates, the female escapes.
Alternatively, the persistent male may squirt urine at the female, possibly in an attempt to mark
her as part of his group.
Fe e ding
Guinea pigs are herbivores. They feed in groups with little competition for food. Unlike other
rodents, guinea pigs cannot manufacture vitamin C; they must consume it in their diet. Sources
of dietary vitamin C include fresh vegetable matter and supplements that caregivers add to food
or water. To extract as much nutrition as possible from their cellulose-rich diet, guinea pigs use
coprophagy. They cannot digest cellulose themselves, but bacteria in their cecum can. However,
once food has reached the cecum, guinea pigs cannot absorb nutrients from it. So, they pass and
eat special, soft fecal pellets containing bacteria-digested cellulose.
APPARATUS/MATERIALS: The following equipment and materials were used in the
dissection: 1 live Guinea pig, 1 ruler, 1 dissecting kit including (1 scissors, 1 scapula, 1 forceps
and1 probe, 8 pins), 1 dissecting tray, paper towel, 4 cm3 chloroform, 1 small carton box, 100 ml
of bleach, 50 ml of liquid detergent, 1 pair of latex gloves, 1 lab coat, 1 digital camera, 2 blank
papers, 2 sheets of newspaper, a sheet of cardboard and 1 pencil.
Part A: Observing the Guinea Pig’s External Anatomy
A Lab Coat and a pair of latex gloves were put on before the start of the practical. To allow for
an undisturbed observation, the Guinea pig had to be subdued. The Guinea pig was placed in a
small carton box, 4 cm3 of chloroform was soaked in a sheet of paper towel and placed over the
nose of the mammal. The carton box was closed tightly to reduce the air in the box and to allow
for the chloroform to be inhaled by the Guinea pig. After three minutes, no movement was
detected by the Guinea pig. The guinea pig was then placed on its ventral side then on its dorsal
side and observed on a piece of cardboard on the dissecting tray. Pins were pierced in the feet
and hands of the Guinea pig to fix it onto the dissecting tray; this allowed for the easy
observation of the external anatomy of the frog. Pictures and measurements were taken and a
drawing made and labeled to represent its external anatomy.
Part B: Observing the Guinea Pig’s Internal Anatomy
The forceps was used to lift the skin while the scissors were used to make a vertical incision in
the middle of the trunk, starting from above the cloaca to the neck. Horizontal incisions were
made at the top and bottom of the vertical incision and the forceps were used to pull away the
skin to expose the chest cavity region of the Guinea pig. Having the chest cavity exposed, a
scapula and scissors were used interchangeable to carefully repeat a vertical incision from above
the anus to the neck of the Guinea pig. Horizontal incisions were made with the scapula at the
top and bottom of the vertical incision. The forceps was used to pull the cavity apart and pin it to
the cardboard to expose the internal organs. A probe was then you used to explore the internal
organs exposing some structures that were located beneath. A picture was then taken and a
drawing made with the structures labeled.
Part C: Clean Up and Disposal
Once the observing and identifying the structures of the Guinea pig were made, the pins were
removed and it was disposed of safely. Excess fluids on the dissecting tray were cleaned off with
plenty of water, bleach and liquid detergent. All of the mammal’s tissues were placed directly
into the garbage bag provided by the lecturer. The dissecting instruments were washed off with
bleach and liquid detergent and dried with a paper towel to prevent rusting. The dissecting
instruments were placed back into the kit only when there were fully dried. The gloves were
disposed of and hands were washed thoroughly.
OBSERVATION AND RESULTS:
The pictures below show the external and internal structures of the Guinea Pig
Like other mammals the Guinea pigs have characteristics which show evolutionary development
that has placed them on top of the class of animals. They have numerous adaptations that enable
them to survive in a wide range of environments. Guinea pigs have hair which grows from skin
cells called follicles. Hair can take on several different forms including thick fur and long
whiskers. Hair serves a variety of functions for guinea pigs; it provides insulation, protects the
skin, serves as camouflage and provides sensory feedback.
Mammals such as guinea pigs differ from other vertebrates such as reptiles, birds and
amphibians in that they have a single lower jaw bone that attaches directly to the skull. This bone
is referred to as the dentary, due to the fact that it holds the teeth of the lower jaw. In other
vertebrates, the dentary is one of several bones in the lower jaw and does not attach directly to
the skull. The structure of the lower jaw and the muscles that control it provides mammals with a
powerful bite and enables them to use their teeth to cut and chew their prey. Mammal species
have specialized teeth adapted to their particular diet. Cats, for example, have sharp teeth that
enable them to tear meat while herbivores such as bison have broad teeth, well-suited for
grinding plant material.
Mammals have a unique arrangement of three bones in the middle ear. These bones—the incus,
malleus and stapes, commonly referred to as the hammer, anvil and stirrup—are unique to
mammals, no other animal group has them. The middle ear bones transmit sound vibrations from
the tympanic membrane or eardrum to the inner ear and transforms them into neural impulses.
The malleus and incus are derived bones that were once part of the lower jaw in mammal
ancestors. Mammals are endothermic which means they are capable of regulating their own body
temperature so that it remains at a relatively constant temperature regardless of the temperature
of the surrounding environment. Like all vertebrates, mammals have a muscular heart that
contracts repeatedly to pump blood throughout the body's blood vessels. The heart serves to
deliver oxygen and nutrients throughout the body and remove waste products. In general, the
heart consists of multiple chambers (the number of chambers differs for the various animal
groups). Two to four chambers may be present and there are two types of chambers, the atrium
and ventricle (the atrium receives the blood returning to the heart while the ventricle pumps
blood from the heart to the rest of the body).
CONCLUSION: Guinea pigs serve as a useful tool in understanding the anatomy of mammals
as its body systems were easily identified and related to structures of humans normally viewed in
books and on pictures or diagrams. Their behavioral patterns, anatomy and morphology showed
evolutionary development of the class which has helped them to adapt to their surrounding
maintaining their dominance among the life forms. Due to their similarity not only in their body
system arrangement but also in their physiological processes, they can be used by scientist to test
for cure or treatment of different illnesses. This investigation has proved worthwhile as due to
the close examination of the anatomy of the guinea pig and a study of its behavioral patterns it
has been proven that mammals are among the most intelligent creatures and have a more
complex body system to sustain life.
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