Download bones associated with the skull

Mr. Shevalier
Human Anatomy & Physiology
Name __________________________________
Date_____________
SKULL LAB
This lab is a study of the human skull. You will be using skull specimens both plastic
and real bone. Please handle them with care. Be sure not to touch them with pencils or pens; use
only the pointers provided. Compare the specimens with the diagrams and notice if any
differences occur. The skull is composed of 22 bones divided into two major portions: the
bones of the cranium (8) and the bones of the face (14). In addition, there are bones
associated with the skull (7). The associated bones are the hyoid and the auditory ossicles.
Try and locate all of the structures mentioned. In addition, you must answer the followup questions and correctly label the two diagrams at the end of this document.
THE CRANIUM
The portion of the skull that surrounds the brain is called the cranium. This is made up of
the following bones: a frontal, a left and right parietal, a left and right temporal, a single
occipital, a single ethmoid, and a single sphenoid. This makes a total of eight cranial bones.
I. Frontal -- The anterior portion of the skull consists of the frontal bone. It forms the ridges
above the eyebrows and nose. The most inferior ridge of this bone extends well into the orbit
(eye socket). On the superior ridges of the orbits you will observe the supraorbital foramina.
Like many bones that neighbor the nasal cavity, this bone contains paranasal sinuses.
II. Parietal -- The parietals are located directly posterior to the frontal bone. They form the
supeiror and lateral aspects of the cranium. A lateral view of the skull presents only one of these
bones, the other obviously being on the other side. There are no significant markings on these
bones. The two parietals meet on the midline of the skull, forming the sagittal suture. Between
the parietals and the frontal bone you will find another suture called the coronal suture.
III. Temporal -- Inferior to the parietals, you will find the temporal bones. Between the
parietal and temporal bones, you will find the squamosal suture. Please locate the following
points of interest on the temporal bone: the mandibular fossa (where the condyle of the
mandible articulates), the external acoustic meatus which leads to the eardrum. Observe the
zygomatic process whhich helps to form the zygomatic arch (the prominence of the cheek), the
mastoid process, an attachment point for several neck muscles. Note the sharp styloid process
which serves as an attachment point for the hyoid bone and several neck muscles.
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The cranial floor has five foramina associated with the temporal bone:
1. foramen lacerum -- characterized by having a jagged margin, hence the name.
Look for it at the junction of the occipital, sphenoid, and temporal bone.
2. carotid canal -- To locate this opening, carefully place a bent paper clip into
the foramen lacerum and push it laterally into this foramen. It is through
this canal that the internal carotid artery enters the brain.
3. jugular foramen -- Located just posterior to the carotid canal. This foramen is
not located in the temporal bone. It is actually located between the
temporal and the occipital bone. This foramen allows for the drainage of
blood out of the brain. The jugular fossa is adjacent to it.
4. stylomastoid foramen -- A small opening at the posterior base of the styloid
process.
5. mastoid foramen -- Located posterior to the mastoid process.
This foramen is sometimes absent.
IV. Occipital -- This bone occupies the posterior portion of the skull. Where it joins with the
parietals, note the lambdoidal suture. The large foramen magnum allows for the passage of the
brain stem. On either side of the foramen magnum, note the occipital condyles. These condyles
articulate with the fossa of the first cervical vertebra. Near the base of each condyle are two
openings. The hypoglossal canals are seen by passing a piece of paper clip wire transversely
through the base of the condyle. Another canal, the condyloid canal may be visible in the
condyloid fossa posterior to the occipital condyle.
V. Sphenoid -- This bone is often described as being in the shape of a bat (not of the baseball
variety!). The portion of this bone that is visible on the lateral aspect of the skull is called the
greater wing (the greater wing composes the wing of the bat). Now find the lesser wings (they
are the ears of the bat). Locate the portion of the sphenoid that is called the orbital surface.
Locate the sella turcica which protects the pituitary gland. Find the anterior and posterior
clinoid processes which surround the sella turcica. Now locate the lateral and medial pterygoid
processes. Muscles that move the jaw and palate are attached to these pterygoid processes. The
sphenoid contains several important foramina which you should now locate.
1. optic foramen - located just beneath the lesser wings.
2. superior orbital fissure - elongated opening between the greater & lesser wings.
3. foramen rotundum - located just inferior to the medial portion of the fissure.
4. foramen ovale - located on the inferior surface, it is somewhat oval in shape.
5. foramen spinosum - a small foramen just lateral to the foramen ovale.
6. pterygoid canal - located just medial to the foramen rotundum.
VI. Ethmoid -- Locate the orbital surface on the medial aspect of the orbit. You should also
locate its perpendicular plate which makes up the superior portion of the nasal septum. The
superior and middle nasal conchae are processes of this bone. Try to locate them by looking
into the nasal passage. One other feature of interest that this bone has is the cribiform plate.
This plate is characterized by tiny foramina which allow for the passage of olfactory neurons.
Also locate the crista galli which extends upwards like the comb of a rooster serving as an
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attachment place for membranes of the brain. (Since the Egyptians removed the brain through
the nose, mummification destroyed this bone)

THE FACE
The face is made up of 13 or 14 bones (depending on the book being used). If 13 facial
bones are being studied, six bones are paired and one, the vomer is unpaired. The unpaired
mandible would be the 14th bone in some references.
I. Vomer -- This bone is visible in the inferior aspect of the nasal cavity where it makes up
the inferior part of the nasal septum. The foot of this bone is visible on the base of the central
floor where it articulates with the sphenoid bone.
II. Maxillae -- The upper set of teeth are set into alveoli of this bone. The alveolar processes
are distinct on its surface. The palatine process makes up a majority of the hard palate. A
portion of this bone is located on the orbital floor. Foramina of note that are associated with this
bone are the infraorbital foramen and the anterior palatine foramen (a.k.a. incisive foramen).
III. Palatines -- The base of this bone makes up the posterior portion of the hard palate. A
small portion of it is visible in the orbit. The greater palatine foramen and two lesser palatine
foramina (sometimes absent) are found in this bone.
IV. Zygomatics -- Also known as the malar bones, these form the prominence of each cheek.
They make up the lateral part of the lateral surface and part of the inferior surface of the orbits.
A small zygomatic foramen may be visible. They combine with the temporal bones to form the
zygomatic arch, a prominent cheek feature.
V. Lacrimals -- These are located in the orbit between the maxillary and ethmoid bones.
Each has a groove which allows the tear ducts to pass down the
into the nasal cavity via the
nasolacrimal canal.
IV. Nasals -- These two small bones form the bridge of the nose.
VII. Inferior Nasal Conchae -- Curved bones attached to the lateral walls of the nasal cavity.
Like the other conchae, the function is to create turbulence for the inspired air.
VIII. Mandible -- (Some books do not count this bone as a face bone) Important features of
the mandible include: The coronoid process, the mandibular condyle, the mental foramen on
the external surface and the mandibular foramen on the medial aspect, the mandibular notch,
and the mental protuberance.
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BONES ASSOCIATED WITH THE SKULL
I.
II.
Auditory ossicles- Within the temporal bones are located the auditory ossicles. You will
not be able to see these on the skull models but be sure to see the individual ossicles
(malleus, incus, and stapes) on display.
Hyoid- This bone is shaped like a horseshoe. It lies behind the mandible and is
positioned just superior to the larynx. It serves as an attachment point for several muscles
that move the tongue and larynx.
Review Questions
Be sure to label the four figures that follow and answer the following questions.
1. What purpose do the foramina of the skull serve?
2. Name all of the bones of the cranium.
3. Name all of the bones of the face.
4. List all of the bones that make up the orbit.
5. What is the function of the auditory ossicles?
6. Explain why the terms skull and cranium are not synonymous.
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