The Human Skull Lecture

Question 1

Skeleton can be divided into 2 principle parts:

Answer 1

A. Axial Skeleton - bones of head and trunk:
Skull, Hyoid, Auditory Ossicles, Vertebral Column, Thorax

B. Appendicular Skeleton - bones of appendages:
Shoulder girdles, upper extremities, pelvic girdle, and lower extremities

Question 2

Skull (How many bones)

Answer 2

• consists of 22 bones
• 8 cranial bones - protect the brain
• 14 facial bones - nasal and oral cavities and facial features

Question 3

Bones of Cranium: Frontal Bone (Where, 4 Details)

Answer 3

• anterior part - forehead
  1. forms superior portion of orbits
  2. frontal squama or vertical plate - most of bone
  3. supraorbital margin = thickening above orbits
  4. frontal sinus

Question 4

Bones of Cranium: Parietal Bones (1 Detail)

Answer 4

• form most of sides and roof of cranium

Question 5

Bones of Cranium: Temporal Bones (11 Details)

Answer 5

• inferior sides of cranium and part of cranial floor.
  1. squamous portion - flat part
  2. zygomatic process - articulates with zygomatic bone
  3. zygomatic arch
  4. petrous portion - floor of cranium between sphenoid and occipital bones - contains internal ear
  5. carotid foramen - (canal) - internal carotid artery
  6. jugular foramen - internal jugular vein and 3 important nerves
  7. mandibular fossa - socket for mandible
  8. mastoid portion - contains mastoid air cells - air spaces that communicate directly with middle ear cavity and are separated only by very thin boney partitions from the brain.
• mastoiditis - infection of these boney air spaces that may spread to brain or its coverings.
  9. mastoid process
  10. external auditory meatus
  11. styloid process - point of attachment for some small muscles and a ligament.

Question 6

Bones of Cranium: Occipital Bone (4 Details)

Answer 6

• posterior part and base of cranium
• foramen magnum
• occipital condyles - articulate with 1st cervical vertebra
• external occipital protuberance

Question 7

Bones of Cranium: Sphenoid Bone (What it means, 8 Details)

Answer 7

(spheno - means wedge - thought of keystone of skull)

• body of sphenoid - cubelike central portion
• sphenoid sinus
• sella turcica
• greater wings - forms part of floor and part of lateral wall of cranium
• lesser wings - anterior and superior of greater wings
• optic foramen - (optic nerve and ophthalmic artery)
• superior orbital fissure (4 important nerves)
• pterygoid processes - form part of lateral walls of nasal cavity - origins of some muscles of mastication.

Question 8

Bones of Cranium: Ethmoid Bone (6 Details)

Answer 8

• principle supporting structure of the nasal cavity - forms part of anterior cranial floor; medial wall of orbits, superior nasal septum, most of nasal cavity’s walls and roof.
• lateral masses or labyrinths - form ethmoid sinuses
• perpendicular plate of ethmoid
• cribiform plate
• crista galli (means roosters comb)
• superior and middle nasal concha - create turbulent flow of air inhaled for efficient filtration and temperature control.

Question 9

Bones of Face: Nasal Bones (How many, 1 detail)

Answer 9

(paired) (2)

- form the bridge of the nose

Question 10

Bones of Face: Maxillae (How many, form, 4 details)

Answer 10

(2) - unite to form upper jaw
form: part of floor of orbits, parts of mouth, part of lateral walls and floor of nasal cavity.
- palatine processes - note: if these do not unite properly before birth - condition known as cleft palate - may also involve cleft lip.
- maxillary sinus
- alveolar process (alveolus = pit or hollow) - boney socket into which teeth inserted
- inferior orbital fissure

Question 11

Bones of Face: Zygomatic Bones (How many, where, 2 details)

Answer 11

2) - cheek bones
- temporal process - articulates with temporal bone
- forms zygomatic arch

Question 12

Bones of Face: Mandible (7 Details)

Answer 12

• lower jawbone - only movable bone of the skull
• body - curved horizontal portion
• ramus (2) - 2 perpendicular portions
• angle
• condylar process - articulates with mandibular fossa of temporal bone
• coronoid process - muscular attachment
• alveolar process - contains sockets for teeth

Question 13

Bones of Face: Lacrimal Bones (4 details)

Answer 13

• very thin - posterior and lateral to nasal bones
• smallest bones of face
• thinnest bones of the body
• form part of orbit medial wall

Question 14

Bones of Face: Palatine Bones (2 details)

Answer 14

• “L” shaped - form posterior portion of hard palate - part of floor and lateral walls of nasal cavity
• horizontal plates - form posterior hard plate

Question 15

Bones of Face: Inferior Nasal Conchae (1 detail)

Answer 15

• same function as Superior and Middle Conchae of ethmoid

Question 16

Bones of Face: Vomer (Meaning, 2 details)

Answer 16

Vomer (means “plow”)

• forms inferior and posterior part of nasal septum
• deviated septum - when vomer is displaced to right or left.

Question 17

Bones of Face: Hyoid Bone (Meaning, 5 details)

Answer 17

(means “U-shaped”)

• also - although not technically a facial bone
• does not articulate with any bone (unique)
• body
• lesser cornu
• greater cornu

Question 18

Fontanels (What are they?) 3 Details

Answer 18

• “soft spots”
• cranial bones form through intramembranous bone formation - however at birth not all the bones of the cranium have totally fused and are separated only by membrane
• six fontenals

Question 19

anterior fontanel (frontal fontanel)

Answer 19

• between 2 parietal and 2 halves of frontal bone

- closes at about 18-24 months

Question 20

posterior fontanel (occipital fontanel)

Answer 20

• at the union of the two parietal and one occipital bones

- closes at about 6-8 weeks

Question 21

anterolateral fontanel (sphenoidal fontanel)

Answer 21

• one on each side at the junction of the frontal, parietal, temporal, and sphenoidal bones.
• closes at about 3 months

Question 22

posterolateral fontanels (mastoid fontanels)

Answer 22

• one on each side of junction of parietal, occipital, and temporal bones
• closes at 1-2 years

Question 23

Teeth (Sets and names)

Answer 23

• 2 sets - appear at different times in life
  1st set = Deciduous Teeth
  2nd set = Permanent Teeth

Question 24

Deciduous (Teeth)

Answer 24

20 Deciduous teeth
4 incisors
2 canines= 10 – 10 on top and 10 on bottom
4 molars
- begin to erupt during 6th month and usually have all erupted by end of 2nd year.
note: teeth of lower jaw usually appear before those on upper jaw.

Question 25

Permanent Teeth

Answer 25

32 Permanent Teeth
4 incisors
2 canines
4 premolars
6 molars

Question 26

Basic Teeth Anatomy (7 Parts to Know)

Answer 26

1. Crown - portion above the gum - covered by enamel
2. Root - portion below gums surface covered by yellowish bone-like tissue - cementum
3. Dentin (or dentine) - composes bulk of tooth - similar to ivory
4. Pulp Cavity - located centrally within the dentin
5. Pulp - within pulp cavity - connective tissue which carries the vascular nutritive supply and sensory nerves to the dentine
6. Peridontal Ligament - surrounds the root of the tooth and attaches to the cementum of the tooth.
7. Gingiva – gums

Question 27

Overview of the Paranasal Sinuses (4)

Answer 27

A. Frontal
B. Maxillary
C. Ethmoid
D. Sphenoid

Question 28

Skull Sutures (What are they?)

Answer 28

Sutures - immovable joints between cranial bones (means seam or stitch) - jagged and irregular

4 important ones:

1. Coronal suture
2. Sagittal suture
3. Lambdoidal suture
4. Squamosal suture