Biology 241 – Lab
(10th/21 Lab Sessions for Fall Quarter, 2008)
LAB #10
TOPICS TO BE COVERED:
»Demonstration of boney landmarks of the 22 bones of the Skull
(with emphasis on the two functional divisions of the skull: Neurocranium and Faciocranium)
»Demonstration of boney landmarks of the 2 bones of the Pelvic Girdle
DESIRED OUTCOMES:
After completing the activities described for this lab session, students should:
»Be able to identify the bones of the skull, divided into neurocranium and faciocranium, and their
principal boney landmarks.
»Be able to identify paranasal sinuses, bones of the nasal septum, hard palate, and orbit of the eye
»Be able to describe the fontanels in the fetal skull
»Be able to identify the bones of the pelvic girdle and their principal boney landmarks; including
gender-specific differences
MATERIALS NEEDED:
»Articulated Skeletons
»Articulated Skulls
»Pipe Cleaners (for pointers)
»Disarticulated Skeletons
»Tortora textbook
»Special Preparation: Disarticulated Skull
»Photographic Atlas, Ch. 5/6/7
**SPECIAL NOTE: BE ACCOUNTABLE FOR THE CARE OF SKULLS SPECIFICALLY AND ALL
BONES GENERALLY. Please be careful NOT to use pencils, pens, or other hard implements while studying the skull
and other bones. Thin bones can be broken and other bones can be permanently marked or harmed. You will be provided
with colorful pipe cleaners to use as pointers. These soft pipe cleaners can be introduced into foramen or used to point out
certain landmarks without damaging the specimens.
Activity #1: Boney Landmarks of the Bones of the Skull
In order to facilitate the study of the bones of the skull, it is divided into two functional divisions:
(1) the neurocranium harbors and protects the brain and houses organs of hearing and equilibrium; and
(2) the faciocranium provides the shape of the face, houses the teeth, provides attachments for all the muscles of
facial expression, and protects soft tissue structures housed within. Other major features of the skull include:
sutures, cerebral and cerebellar fossae, orbits of the eyes, paranasal sinuses, nasal septum, hard palate, and
fontanels in the fetal skull.
There are a total of 8 bones in the neurocranium; four are single bones, and two are paired bones:
frontal (1), occipital (1), ethmoid (1), sphenoid (1), parietal (2), and temporal (2). Together, these 8 bones form
what is known as the calvaria (skullcap) and the base of the cranial cavity. The base of the cranial cavity contains four indentations known as the anterior, middle and posterior cerebral fossae and the cerebellar fossa.
Sutures are immovable joints between cranial and facial bones; but the four main sutures in the skull
(and the ones you are responsible for knowing) are:
1. Coronal suture– joins the one frontal and two parietal bones across the midline. (corona (Latin) = crown)
2. Sagittal suture – joins the right and left parietal bones in the exact midline. (sagitta (Latin) = arrow)
3. Lambdoidal suture – joins the two parietal bones with the one occipital bone across the midline. (Has the
shape of the Greek letter lambda
λ)
4. Squamosal suture – joins one temporal bone and one parietal bone on the same side. (squam (Latin) =
fishscale, flat)
(All other sutures have names that reflect the two bones they unite: e.g., frontozygomatic, sphenoccipital, or zygomaticomaxillary.)
Biology 241 – LAB #10 – continued
Page Two
There are a total of 14 bones in the faciocranium; six are paired bones and only two are single bones:
maxilla (2), palatine (2), zygoma (2), lacrimal (2), nasal (2), inferior nasal concha (2), mandible (1), and
vomer (1). (Note: the plural of maxilla is maxillae; the plural of concha is conchae. If one wants to refer to the two
maxillary bones or to the two inferior nasal concha bones, one says: “the two maxillae or the two inf. nasal conchae.)
The orbit of the eye is a mosaic of six different bones; three neurocranial bones (frontal, sphenoid, and
ethmoid) and three faciocranial bones (maxilla, zygoma, and lacrimal).
Paranasal sinuses are cavities lined with mucous membranes that are located near (and have openings
into) the nasal cavities. The four paranasal sinuses, the ethmoidal (known also as ethmoidal air cells), frontal,
maxillary, and sphenoidal, are named for their locations in bones of the same name.
The nasal septum is comprised of bone and cartilage. The inferior bone is the vomer, and the
perpendicular plate of the ethmoid bone is superior. The septal cartilage is anterior to the two bones.
The hard palate, or roof of the mouth, is formed by the fusion of parts of four bones: the palatine
processes of the R and L maxillae and the horizontal plates of the R and L palatine bones. Approximately threefourths of the hard palate is composed of the palatine processes of the two maxillae; and only one-fourth is contributed by the horizontal plates of the palatine bones. The suture that goes down the midline of the hard palate
is called the median palatine suture; and the suture that is perpendicular to the median suture, formed at the
junction of the palatine bones with the maxillae, is the transverse palatine suture.
To go about learning the bones of both the neurocranium and faciocranium and their individual boney
landmarks, you will again engage in a cooperative learning exercise, working with your lab partners to teach
each other. This time there is a slight variation in the instructions. Here is the procedure:
1. The class is assembled into groups of four to five students, for a minimum of 5 groups.
2. Each group takes a skull and is assigned one of the following five sets of bones and boney landmarks:
Set I: Calvaria, base (and 4 fossae), and structures of the frontal bone and parietal bones.
Set II: Temporal bone and occipital bone and boney landmarks of each.
Set III: Ethmoid bone and sphenoid bone and boney landmarks of each.
Set IV: Mandible and maxillae and boney landmarks of each
Set V: Remainder of the facial bones, orbit, nasal septum, hard palate, sutural (Wormian) bones, and
anterior / posterior fontanels (in a fetal skull).
3. Each member of each group spends approximately 3 – 5 minutes learning the assigned structures on his/her
own.
4. Now, each student spends approximately 2 – 3 minutes demonstrating the assigned structures to the group.
(Lots of repetition is good!)
5. The assigned structures are rotated clockwise so each group has a new set of structures to learn (ie: the group
that was originally assigned Set I will take Set II, and so on). Within the group, be sure to rotate the skull from
student to student as well; those not holding the actual boney skull will use the Photographic Atlas for ID of
his/her assigned structures.
6. Each student spends approximately 3 – 5 minutes learning the structures in the assigned Group.
7. Now, each student spends approximately 2 – 3 minutes teaching the group his or her assigned structures.
8. The process is repeated (it begins to speed up significantly) until each student has demonstrated each Set of
structures once. By the end of this exercise, the students will have learned each Set of structures and each Set
will have been presented four (or more) times.
Biology 241 – LAB #10 – continued
Page Three
Please use the list of bones and boney landmarks on the next several pages. This list covers which landmarks
are required learning.
Your Instructor will demonstrate the foramina (plural of foramen) that are included on the list. These are best
learned by having been shown one or more times exactly which foramen is which!
Activity #2: Boney Landmarks of the Pelvic Bones (aka Os Coxa; aka Hip Bone)
The pelvic girdle is composed of two hip bones called the os coxae that attach the lower limb to the
axial skeleton. Each os coxa is formed by the fusion of three separate bones: the ilium, ischium, and pubis
bones. These three bones are identifiable as separate bones in children, but are fused into one in the adult.
On each os coxa, locate the:
1. Ilium (from ilia = flank) – largest and most superior of the three components of the os coxa
*iliac crest – superior border of the ilium
*anterior superior iliac spine – anterior end of the iliac crest
*anterior inferior iliac spine – below the anterior superior iliac spine
*posterior superior iliac spine – posterior end of the iliac crest
*posterior inferior iliac spine – below the posterior superior iliac spine
*greater sciatic notch – large, arched notch on posterior side
*iliac fossa – depression on the anterior surface
2. Ischium (from ischion = hip joint) – inferior, posterior portion of the os coxa
*ischial tuberosity – large, roughened projection on the posterior and inferior edge; we “sit on” these
when we sit upright in a chair. If the chair is hard (and there is not much body
cushioning, aka “fat”), it can get very uncomfortable!
*ischial spine – posterior projection between the greater and lesser sciatic notches
*lesser sciatic notch – smaller indentation between the iscial spine and the ischial tuberosity
3. Pubis (from pub = grown up, or adult) – anterior, inferior portion of the os cosa
*pubic symphysis – joint where the two pubic bones join anteriorly
Boney landmarks formed by the fusion of all three: the ilium, ischium, and pubis:
*acetabulum – deep indentation, or cup, for articulation with the head of the femur
*obturator foramen – largest foramen in the skeleton
Pelvis terms:
*pelvic brim – divides the false pelvis from the true pelvis; begins at the sacral promontory and extends
laterally and inferiorly to end at the pubic symphysis
*false pelvis – portion of the pelvis superior to the pelvic brim; wide area extending to top of iliac crest
*true pelvis – portion of the pelvis inferior to the pelvic brim; surrounds the pelvic cavity
*pelvic inlet – superior opening of the true pelvis; bordered by the pelvic brim
*pelvic outlet – inferior opening of the true pelvis; bordered by the coccyx, ischial spines, and ischial
tuberosities.
Additional information: The hip or coxal joint is formed by the acetabulum articulating with the head of the
femur to form a diarthrodial, ball-and-socket joint. There is a strong ligament that connects these two structures
deep inside the joint itself. When articulated os coxae are united posteriorly with the sacrum at the sacroiliac
joints, they form the boney pelvis and the connection of the lower extremities with the axial skeleton.
Biology 241 – LAB #10 – continued
Page Four
There are definite anatomical differences between the male and female pelves. The bones of the male are
typically heavier and rougher, with larger boney landmarks than the female. The male pelvis is more narrower
and more vertical, has a pelvic inlet that is heart-shaped, and has a 90º or less (acute) subpubic angle. The
female pelvis generally has more space in the true pelvis (for child bearing: carrying and birthing) and is tilted
backward and flared. The pelvic inlet is round or oval, and the subpubic angle is generally great than 90º
(obtuse). These features are summarized in the table below:
Female Pelvis
Male Pelvis
Pelvic inlet shape
Wider and oval-shaped
Narrower and heart-shaped
Subpubic angle
90º or greater (obtuse)
Less than 90º (acute)
Acetabulae
Further apart
Closer together
Ischial tuberosities
Everted
Inverted
Coccyx
Straighter, more
movable
Curved anteriorly,
Less movable
Feature