Objectives:
-
To compare the cranial skeletons of a variety of
vertebrates, noting differences in size, location, and occurrence of the bones
-
To
relate these anatomical differences to differences in behavior and function
-
To begin your formal study
of the cat's cranial skeleton
Goals:
Your
general observations of vertebrate skulls will help you develop an understanding
of the trends and changes in the cranial skeleton that accompanied the evolution
of the various vertebrate groups. Careful observation will also help you
understand how skull anatomy relates to the particular lifestyles of individual
species. Your final goal is to learn to identify all the cat bones and cranial
features listed at the end of this handout.
Materials:
We have a variety of crania and
whole mounted skeletons (including the crania) from each type of vertebrate:
fish, amphibians, reptiles, birds, and mammals. Some
specimens are accessible, others are encased in a plastic display.
We have particularly good collections of skeletal material from two species:
cats and humans. We have three articulated human skeletons (one partial of
real bone, two plastic, one of which has muscle origins and insertions painted
on). We also have several disarticulated human skeletons and a variety of
human skulls. For cats we have a complete mounted skeleton, a complete
disarticulated skeleton (except the cranium is articulated), and a bisected
skull for each lab table (five sets of each). We also have two display
cases that show individual disarticulated bones for the cat skull.
All these
materials are on the shelves or in the cabinets located around the lab.
You can take them out for study anytime the lab is available. Please put
them back when you are done. You cannot remove specimens from the lab
without the permission of the instructor.
Pre Lab:
Read the introduction to your lab manual, pages
1-3, and the introduction to the skeletal system on pages 5-6. Pages 5-22
in the lab manual cover the cranial bones we will study. As you will see,
these pages are designed to be read during lab when you have actual specimens in
front of you. However, before lab you can skim through these pages to
become familiar with the organization of the text and figures. This will
help you prepare for lab, since you will work through the cat skull bones in the
same order as they are covered in the manual.
What to do in lab:
During the first hour or so of lab, spend time
observing the skulls from each of the vertebrate groups.
Observe
and take notes regarding the differences in size, location, and occurrence of
the cranial bones among the different vertebrates. Also make note of any specializations evident in the structure of the
cranial skeleton. Since skull anatomy determines how an animal feeds, you should be
able to find important differences among the teeth, jaw sizes, and jaw
attachments that are related to different types of feeding.
As you will learn, however, the skull provides a wide range of functional
features in addition to feeding. Discuss your observations with lab
partners and the instructor, write down your thoughts in your lab notebook, and
try to develop a general picture of how the skull contributes to being a fish,
amphibian, reptile, bird, or mammal. For reference, there are anatomical
guides to many vertebrates available in the bookcase in the lab.
During
your remaining lab time you will study the cranial skeleton of the cat.
Work carefully, in order, through your lab manual, and use BOTH text and
pictures to help you identify every bone and every feature on the bones.
Draw diagrams and take notes in your lab notebook to help you identify each bone
and feature.
Post
Lab:
Your main
post lab assignment is to learn how to identify the bones and other structures
of the cat cranial skeleton for the lab practical. A complete list of the
bones and structures you are responsible for appears below.
For each structure on this
list, you’ll need to be able to locate it within the cranial skeleton, identify it on a diagram or on a specimen
(articulated or disarticulate, and if it is a bone know its evolutionary and
embryonic origin (this will become clearer as we discuss the cranial skeleton in
lecture).
When
learning bones (or any other category of anatomical structures), it is vital to
organize your study. One approach, with
help from your text, is to
categorize
each cranial bone as part of the dermatocranium, the chondrocranium, or the
splanchnocranium. Within each
of these three components, the bones form “series.” For
example, the bones of the dermatocranium can be organized as:
the bones of the face, the vault of the head, around the eyes, around the
cheeks, and the upper jaw. This
organization helps you remember the bones, and also helps you locate them.
Your lab notes and diagrams will help as well.
In
addition to identifying cat bones, for the lab practical you should be prepared
to answer some general questions about how skulls and jaws work, and how
different sizes and shapes of the skull can lead to different functions.
You won't need to identify bones from other species, but you should know some of
the cranial differences between the main groups of vertebrates, and be able to
interpret a skull as belonging to a carnivore or herbivore.
The
cranial skeleton is a complicated, but interesting, structure that will teach
you a great deal about the evolution and functionality of vertebrates.
Good luck, and have fun!
Cranial bones you need to know:
(cat only)
| BONE: |
FEATURE(S): |
|
premaxilla |
palatine process; anterior palatine foramen
|
|
maxilla |
palatine,
frontal, and zygomatic processes; infraorbital formamen, alveolar foramina |
|
nasal |
|
|
ethmoid |
perpendicular plate,
cribiform plate |
|
vomer |
|
|
palatine |
pterygoid process; posterior palatine
foramen, sphenopalatine foramen |
|
lacrimal |
nasolacrimal canal |
|
frontal
|
|
|
zygomatic |
orbital and zygomatic processes |
|
parietal
|
tentorium |
|
interparietal
|
|
|
occipital |
hypoglossal canals; occipital condoyles;
jugular processes; jugular foramen, foramen magnum |
|
sphenoid |
pterygoid process, hamulus, alisphenoiod,
basisphenoid; foramen ovale, foramen rotundum, orbital fissure; sella
turcica |
| presphenoid |
optic foramen |
| temporal |
squamous, petrous, and
tympanic portions; zygomatic process; mandibular fossa; mastoid process;
internal/external auditory meatus; stylomastoid foramen |
| dentary |
coronoid, condyloid,
angular processes; masseteric fossa; ramus, body; mandibular foramen,
mental foramina |
| teeth |
not really bones!
identify: incisors, canine, premolars, molars |
| |
|
| |
olfactory fossa, cerebral
fossa, cerebellar fossa |
