The Skull

Question 1

What is in the neurocranium and its divisions ?

Answer 1

Encloses cranial cavity
Contains - PEST OF 6
- parietal
- temporal
- frontal
- occipital
- sphenoid
- ethmoid

2 divisions - calvarium and cranial base

Question 2

What are the sutures in the neurocranium ?

Answer 2

Coronal & Sagittal sutures = Bregma
Squamosal & Coronal sutres = Pterion
Lamboidal & Sagittal sutures = Lambda

Question 3

What are the contents of the viscerocranium ?

Answer 3

They are the facial bones
Contains
Maxilla
* Zygomatic
* Nasal
* Palatine
* Lacrimal
* Inferior concha
* Vomer
* Mandible

Question 4

Describe the parietal bone:

Answer 4

2 parietal bones, 1 on each side
Temporal lines - superior border
Temporalis fossa - temporalis muscle attaches
Joins Sphenoid, Frontal & Temporal bones at the Pterion - weak part of the skull overlying middle meningeal artery
Fracture can cause an epidural hematoma

Question 5

Describe the frontal bone:

Answer 5

Forms part of anterior cranial fossa & roof of orbit
Supraorbital ridge above orbits, marked with a supraorbital notch/foramen - for the supraorbital nerves
Contains the frontal sinus

Question 6

Describe the occipital bone:

Answer 6

Forms part of posterior cranial fossa
Contains foramen magnum for the brainstem
External occipital protuberance for attachment of trapezius & nuchal ligament
Hypoglossal canal for the cranial nerve XII
Occipital condyles - articulate with C1 vertebrae at the occipital joint, permitting flexion/extension of the neck

Question 7

Describe the temporal bone:

Answer 7

Squamous part - includes the zygomatic process, a bony projection that extends forward to connect with the zygomatic (cheek) bone, forming the zygomatic arch

Styloid process -

Mastoid process - rounded region, regulates ear pressure

Petrous part - houses ear cavities, internal and external acoustic meatus (opening that transmits the facial and vestibulocochlear nerves, which are responsible for facial movement)

Stylomastoid foramen - between styloid + mastoid, contains facial nerve

Temporomandibular (jaw) joint socket

Forms part of middle & posterior cranial fossae

Question 8

Describe the sphenoid bone:

Answer 8

Positioned just in front of the temporal bones and the basilar part of the occipital bone
Lesser wing forms anterior cranial fossa and greater wing forms middle cranial fossa
4 crinoid processes - attachment for meninges
2 Medial & 2 Lateral Pterygoid plates - for muscle attachment

Sella Turcica - houses pituitary gland

Openings;
Optic canal
Superior orbital fissure
Foramen rotundum
Foramen ovale

Question 9

What are the cranial nerves in the sphenoid ?

Answer 9

Optic canal - cranial nerve I/ optic
Superior orbital fissure; supplies eye muscles
- Cranial nerve III/ Oculomotor
- Cranial nerve IV/ Trochlear
- Cranial nerve VI/ Abducens

Question 10

Describe the ethmoid bone:

Answer 10

Part of anterior cranial fossa
Cribiform plate with holes opening into nasal cavity
Crista gali - attachment point for meninges
Medial wall of orbit
Roof, medial & lateral walls of nasal septum
Ethmoid air sinuses

Question 11

Describe the zygomatic bone:

Answer 11

Cheek bone
Articulates with: Maxilla, Sphenoid, Frontal & Temporal bones
Zygomatic bone + part of temporal bone form the Zygomatic arch
Temporalis muscle - runs under the arch to attach to the Mandible

Question 12

Describe the palatine bone:

Answer 12

Forms parts of the nasal cavity, hard palate, and the floor of the orbits
Horizontal plate - forms the posterior portion of the hard palate
Vertical plate - supports the structure of the nasal cavity
Palatine foramina - for palatine nerves & vessels supplying palate

supporting the separation of the nasal and oral cavities

Question 13

Describe the lacrimal bone:

Answer 13

Thin bone located in the medial wall of each eye socket
Medial wall of orbit
Lateral wall of nasal cavity
Tears produced by Lacrimal gland which drains to lacrimal sac & then nasolacrimal duct
Duct runs in lacrimal bone to Nasal cavity

Question 14

What is a hydrocephalus ?

Answer 14

Increased pressure of fluid in the skull due to cerebrospinal fluid
Compresses the brain

Question 15

What are the cavities in the head ?

Answer 15

Cranial - upper and back of head, houses the brain and protects it

Orbital - protects the eyes and structures needed for vision, located on either side of the upper face

Nasal cavity - between the orbits, lined with mucous membranes and cilia, it houses nasal conchae and the olfactory receptors for smell, divided into left and right by nasal septum

Ear - within the temporal bones, middle ear cavity is air-filled, while the inner ear is fluid-filled, Responsible for transmitting sound waves, processing hearing

The Palate separates the Nasal & Oral cavities

Question 16

Describe cranial nerve I:

Answer 16

Cranial nerve I/Olfactory nerves innervate nasal mucosa
Passes superiorly through cribriform plate
Enter olfactory bulb & run posteriorly back to brain
Head impact can fracture cribriform causing CSF leaking from nose and Anosmia

Question 17

Describe the maxilla:

Answer 17

Pair of fused bones that form the upper jaw
Central body - hollow and contains the maxillary sinus, which reduces skull weight and forms the facial framework.

Lower part forms the upper dental arch

Frontal process extends upward to meet the frontal bone, contributing to the nose and eye socket

The palatine process forms the anterior hard palate, providing a barrier between nasal and oral cavities

Upper teeth are embedded in the alveolar ridge
Infraorbital foramen - for infraorbital nerves & vessels supplying skin inferior to eye

Question 18

Describe the inferior conchae/ turbinate:

Answer 18

Part of Lateral wall of Nasal Cavity
3 Conchae project into the cavity on each side
Nasal septum divides nasal cavity in midline creating 4 passages for warming & humidification ( covered in a specialiSed mucous membrane)
Increases the surface area within the nasal cavity

Question 19

Describe the nasal bone:

Answer 19

2 small, rectangular bones that form the bridge of the nose
Articulates with frontal, maxilla and ethmoid
Supports the softer cartilage of the nose that extends outward
Vertical groove for branches of nasociliary nerve & vessels supplying tip of nose

Question 20

Describe the vomer:

Answer 20

Part of nasal septum
Articulates with Maxilla, Palatine, Sphenoid & Ethmoid
Nasal septum = Ethmoid, Vomer & Cartilage
Vomeronasal organ: area where vomer meets palate containing receptors for pheromones
In some mammals, this opens into the mouth via the Nasopalatine/ incisive canal