1. ANATOMY AND PHYSIOLOGY
CHAPTER 5: THE SKELETON (SKULL)
ANATOMY AND PHYSIOLOGY

2. ETHMOID BONE
An anterior cranial bone found between the eyes. It contributes to the medial wall of the orbit, the roof and walls of the nasal cavity, and the nasal septum. Very porous, delicate bone. Contains 3 major portions.

4. Parts of the Ethmoid PERPENDICULAR PLATE:
Vertical, thin plate of bone that forms the superior 2/3s of nasal septum. (lower part formed by vomer bone). The septum divides the nasal cavity into right and left air spaces called the NASAL FOSSAE. The septum is often curved (deviated) toward one nasal fossa or the other.
2.CRIBRIFORM PLATE:
Horizontal, forms roof of nasal cavity. It contains a crest called the CRISTA GALLI, an attachment point for the meninges that enclose the brain. The CRIBRIFORM FORAMINA is on either side of crista. A pair of olfactory bulbs of the brain, concerned with smell, rest in these depressions, and the foramina allow passage for olfactory nerves from the nasal cavity to the bulbs.

5. 3. LABYRINTH:
Large mass on each side of perpendicular plate. It is named this due to the internal maze of air spaces called the ETHMOIDAL CELLS. Collectively, these constitute the ETHMOID SINUS. The lateral surface of the labyrinth is a smooth, slightly concave ORBITAL PLATE seen on the medial wall of the orbit. The medial surface of the labyrinth gives rise to 2 curled, scroll-like plates of bone called the SUPERIOR AND MIDDLE NASAL CONCHAE. The inferior nasal conchae is a facial bone. These project into the nasal fossa from its lateral wall toward the septum.

6. These nasal conchae together occupy most of the space in the nasal cavity. By filling space and creating turbulence in the flow of inhaled air, they ensure that the air contacts the mucous membranes that cover these bones, which cleanse, humidify, and warm the inhaled air before it reaches the lungs. The superior concha and adjacent part of the nasal septum also bear the sensory cells of smell. In studying an intact skull, all that can be seen of the ethmoid is the perpendicular plate, by looking into the nasal cavity; the orbital plate, by looking at the medial wall of the orbit; and the crista galli and cribriform plate, viewed from within the cranial cavity.

7. Injury to the ethmoid bone: it is very delicate and easy to injure by a sharp upward blow to the nose, such as a person might suffer by striking an automobile dashboard in a collision. The blow can drive bone fragments through the cribriform plate into the meninges or brain tissue. Detection is by seeing leakage of cerebral fluid into the nasal cavity, followed by the spread of infection from the nasal cavity to the brain. Blows to the head can also shear off the olfactory nerves that pass through the ethmoid bone and cause anosmia, an irreversible loss of the sense of smell and a great reduction in the sense of taste (most of which depends on smell).

8. FACIAL BONES (14 FACIAL BONES)
All are paired up except for the MANDIBLE and VOMER bones. The MAXILLAE, ZYGOMATICS, NASALS, LACRIMALS, PALATINES, and INFERIOR NASAL CONCHAE are paired bones.

9. As a rule, men’s facial bones are more elongated than that of women; therefore, women’s faces are rounder and less angular.
Facial bones have no direct contact with the brain or meninges. They provide attachment for the muscles of facial expression.

10. 1. MANDIBLE (single)
V-shaped, lower jaw, largest, strongest bone of the face.
The “body” of the mandible forms the chin; the 2 rami (“Y” shaped at top) are upright meeting the body at the MANDIBULAR ANGLE.
2 processes at top of ramus are separated by the MANDIBULAR NOTCH.
CORONOID PROCESS – attachment point for jaw muscles to move jaw up and down

11. ALVEOLAR MARGIN is the area where teeth are located.
MANDIBULAR FORAMEN is located on each ramus, permit nerves responsible for tooth sensation to pass to teeth in lower jaw. This is where dentist inject Novocain to work on lower teeth with no pain.
MENTAL FORAMINA – found on mandibular body – allows blood vessels and nerves to pass to chin and lower lip
MANDIBULAR SYMPHYSIS(Protuberance) – as fetus, your mandible is 2 bones. As you develop they fuse to form this joint.

12. 2. MAXILLAE or maxillary bones (pair)
Upper jaw, central portion of face
All facial bones (except mandible) articulate with maxillae – KEYSTONE BONE OF THE FACIAL SKELETON.
As a fetus, the maxillae is actually 2 bones and fuses to form one bone at the INTERMAXILLARY SUTURE.

13. These bones fuse at 12 weeks gestation but failure of this will result in a “CLEFT PALATE” / “CLEFT LIP”.
This will cause nursing to be difficult until corrected surgically. Our palate allows us to breath as we chew our food. The PALATINE BONES form the rest of the hard palate.

14. 3. PALATINE BONES (pair)
Form the rest of hard palate, part of nasal cavity wall, part of floor of orbit.
PALATINE PROCESSES form roof of mouth and floor of nasal cavity. ALVEOLAR MARGINS hold upper teeth in place.
ALVEOLI (sockets) contain the roots of the teeth.

15. 4. ZYGOMATIC BONES (pair)
Irregularly shaped.
Also known as “malar bones”.
Give us our cheek bones along with the zygomatic processes of the temporal bones and the zygomatic processes of the maxillae.

16. 5. NASAL BONES (pair)
Thin, rectangular shape
Fused medially to form bridge of nose.
Inferiorly, they attach to the cartilage plates that form the lower skeleton of nose.

17. 6. LACRIMAL BONES (pair)
Form part of medial wall of each orbit.
Fingernail shaped
LACRIMAL FOSSA – a depression that houses the lacrimal sac which collect tears from the eye and drain into the nasal cavity.

18. 7. VOMER BONE (single)
Slender, plow-shaped; Name means “plowshare”
Located within nasal cavity forming part of nasal septum.

19. 8. INFERIOR NASAL CONCHAE (pair)
Three of these in nasal cavity (superior and middle conchae are part of the ethmoid bone). The INFERIOR NASAL CONCHAE is the largest of the three. Thin, curved bones projecting from the lateral walls of the nasal cavity. Form part of the lateral walls of the nasal cavity.

20. THE EYE ORBITS ON SKULL: 7 bones make up each orbit
FRONTAL
SPHENOID
ZYGOMATIC
MAXILLA
PALATINE
LACRIMAL
ETHMOID

21. BONES ASSOCIATED WITH SKULL
Some bones closely associated with skull but not considered part of it:
AUDITORY OSSICLES – found in middle ear cavity; deal with hearing
malleus (hammer)
incus (anvil)
stapes (stirrup)

22. HYOID BONE
Slender bone between chin and larynx. Doesn’t articulate with ANY other. Suspended from styloid process in the mid-neck region like a hammock. Serves as attachment of several muscles that control the mandible, tongue, larynx. Helps with swallowing and speech. Forensic pathologists look for a fractured hyoid as evidence of strangulation.

23. PARANASAL SINUSES
5 skull bones contain mucosa-lined, air-filled sinuses that cause these bones to look rather moth-eaten in an X-ray.
Frontal
Sphenoid
Ethmoid
Paired maxillary bones
Help with resonance of voice. Small openings connect sinuses to nasal cavity. Air enters the sinuses from the nasal cavity and mucus formed by the sinus mucosae drains into the nasal cavity. The mucosa of the sinus also helps to warm and humidify inspired air.