Week 3: Gross Anatomy of the Skull and Orbit

Question 1

What is a bone?

Answer 1

• Hard connective tissue
• Consists mainly of the skeleton of most vertebrates
• Organic component: cell and matrix
• Inorganic: minerals (e.g. calcium phosphate, calcium carbonate)

Question 2

Function of bones?

Answer 2

• Support & protect the body
• Provide points of attachment & levers for muscles
• Reservoir for several minerals of the body
• Contains bone marrow

Question 3

What are the two bone structures and explain their characteristics?

Answer 3

1. Compact/Cortical (dense bone)
   - Outer shell & surrounds spongy bone
   - Softer in children
2. Spongy/Trabecular (cancellous)
   - Inner part
   - Consists of bone spicules and haemopoietic cells

Question 4

What are the types of marrow and what do they contain?

Answer 4

1. Red marrow
   Contains: RBCs, platelets and most WBCs
2. Yellow marrow
   Contains: some WBCs, fat cells, newborns do not contain these until 6-7 months

Question 5

List the types of bones

Answer 5

• Long bones
• Short bones
• Flat bones
• Irregular bones
• Sesamoid bones

Question 6

What is the shape of long bones and an example?

Answer 6

• Shape: tubular, have shaft between two heads

- E.g: femur (upper bone of leg)

Question 7

What is the shape of short bones and an example?

Answer 7

• Shape: cuboidal (similar width & length)

- E.g: bones of wrist

Question 8

What is the shape of flat bones and an example?

Answer 8

• Shape: flat & thin with two compact bone plates separated by spongy bone
• E.g: skull

Question 9

What is the shape of irregular bones and an example?

Answer 9

• Shape: bones of various shapes

- E.g: facial bones

Question 10

What is the shape of sesamoid bones and an example?

Answer 10

• Shape: round oval bones that develop within tendons

- E.g: patella (front of knee joint)

Question 11

What are the two surrounding bones and describe their characteristics

Answer 11

1. Periosteum
   - External surface of the bone is covered with periosteum
   - Outer layer consists of dense vascular connective tissue
2. Articular Cartilage
   - white, smooth tissue that covers the surfaces of bones in joints
   - allows joints to easily glide over each other

Question 12

What is the blood supply process to the bone and its innervation?

Answer 12

Blood supply process:

1. Adjacent arteries branches a nutrient artery that enters internal cavity of bone, suppling to marrow, spongy bone & inner layers of compact bone
2. Periosteum receives blood from vessels that supply outer layers of compact bone

Question 13

Name the cranium bones and how many there are

Answer 13

• Frontal x1
• Parietal x2
• Occipital x1
• Temporal x2
• Sphenoid x1
• Ethmoid x1

Question 14

What does the cranium contain? (hint: 4)

Answer 14

1. Brain
2. Meninges (dura mater, pia mater & arachnoid)
3. Blood vessels
4. Nerves
   - 12 cranial
   - Sympathetic & parasympathetic nerves
   - Vessels & nerves pass through foramina

Question 15

Define sutures?

Answer 15

• Immovable joints found between bones in people aged around > 14 months
• Narrow seams of fibrous connective tissue

Question 16

Name all the sutures

Answer 16

• Coronal suture
• Sagittal suture
• Lambdoid suture

Question 17

Name CNI, the location, type (sensory/motor nerve) and function

Answer 17

• Name: Olfactory
• Location: travels through cribriform plate of the ethmoid bone
• Type: sensory
• Function: sense of smell

Question 18

Name CNII, the location, type (sensory/motor nerve) and function

Answer 18

• Name: optic
• Location: travels through the optic foramen
• Type: sensory
• Function: sense of vision

Question 19

Name CNIII, the location, type (sensory/motor nerve) and function

Answer 19

• Name: oculomotor
• Location: travels through the superior orbital fissure
• Type: motor
• Function: eye movement

Question 20

Name CNIV, the location, type (sensory/motor nerve) and function

Answer 20

• Name: trochlear
• Location: travels through the superior orbital fissure
• Type: motor
• Function: eye movement - intorsion, depression & abduction

Question 21

Name CNV, the location, type (sensory/motor nerve) and function

Answer 21

• Name: trigeminal
• Location: travels through the superior orbital fissure - 3 branches: ophthalmic division (v1), maxillary (v2), mandibular (v3)
• Type: both
• Function: facial motor & sensory

Question 22

Name CNVI, the location, type (sensory/motor nerve) and function

Answer 22

• Name: abducens
• Location: travels through the superior orbital fissure
• Type: motor
• Function: eye movement

Question 23

Name CNVII, the location, type (sensory/motor nerve) and function

Answer 23

• Name: facial
• Location: travels through internal auditory canal
• Type: both
• Function: facial & motor sensory

Question 24

Name CNVIII, the location, type (sensory/motor nerve) and function

Answer 24

• Name: vestibulocochlear
• Location: travels through internal auditory canal
• Type: sensory
• Function: audiotory & balance

Question 25

Name CNIX, the location, type (sensory/motor nerve) and function

Answer 25

- Name: glossopharyngeal - Location: travels through jugular foramen - Type: both - Function: oral sensation & taste

Question 26

Name CNX, the location, type (sensory/motor nerve) and function

Answer 26

- Name: vagus - Location: travels through jugular foramen - Type: both - Function: sensory, motor & parasympathetic

Question 27

Name CNXI, the location, type (sensory/motor nerve) and function

Answer 27

- Name: accessory - Location: travels through jugular foramen - Type: motor - Function: neck & head turning

Question 28

Name CNXII, the location, type (sensory/motor nerve) and function

Answer 28

- Name: hypoglossal - Location: travels through hypoglossal canal - Type: motor - Function: moving tongue

Question 29

Name the floors of the cranium

Answer 29

1. Anterior cranial fossa 2. Middle cranial fossa 3. Posterior cranial fossa

Question 30

What are the borders and important landmarks for anterior cranial fossa?

Answer 30

- Borders: frontal bone, lesser & greater wing of sphenoid, ethmoid bone - Important landmarks: contains frontal lobes of cerebral hemispheres

Question 31

What are the borders and important landmarks for middle cranial fossa?

Answer 31

- Border: lesser & greater sphenoid, temporal bones, parietal bones - Important landmarks: pre-chiasmatic sulcus, sella turcica: pituitary gland located in it, cavernous sinus

Question 32

What are the borders, contents and important landmarks for posterior cranial fossa?

Answer 32

- Borders: dorsum sellae of sphenoid, occipital bone, temporal bone - Important landmarks: foramina magnum, jugular foramen, hypoglossal canal, internal audiotory canal - Contents: cerebellum, pons, medulla oblongata

Question 33

Name the fourteen facial bones and how many

Answer 33

- Zygomatic x2 - Maxilla x2 - Nasal x2 - Lacrimal x2 - Vomer x1 - Palatine x2 - Inferior conchae x2 - Mandible x1

Question 34

Name the orbital margins and what they are formed by

Answer 34

- Supra-orbital margin: frontal bone - Infra-orbital margin: zygomatic bone (laterally), maxilla (medially) - Lateral margin: frontal process of zygomatic, zygomatic process of frontal - Medial margin: maxillary process of frontal bone, lacrimal process of frontal bone

Question 35

Name the bones consisting of the roof of orbit and its strength

Answer 35

- Consisting of: lesser wing of sphenoid & frontal bone | - Strength: thin & fragile

Question 36

Name the bones consisting of the floor of orbit and its strength

Answer 36

- Consisting of: zygomatic bone, maxilla, palatine bone | - Strength: weakest wall

Question 37

Name the bones consisting of the medial wall of orbit and its strength

Answer 37

- Consisting of: lesser wing of sphenoid, ethmoid bone, maxilla - Strength: very thin

Question 38

Name the bones consisting of the lateral wall of orbit and its strength

Answer 38

- Consisting of: greater wing of sphenoid, frontal bone, zygomatic bone - Strength: thickest wall

Question 39

List what paranasal sinuses is lined with, filled with and its functions

Answer 39

- Lined with mucoperiosteum - Filled with air: lightens the skull - Functions: crumple zone to protect vital structures & increases speech resonance

Question 40

What are the three opening into the orbital cavity and describe what it transmits and supplies

Answer 40

1. Infraorbital groove - Contains infraorbital nerve - Becomes infraorbital canal as it passes through maxilla - Infraorbital nerve emerges from infraorbital foramen 2. Anterior ethmoidal foramen - Transmits: anterior ethmoidal nerve, vein & artery - Supplies: anterior & middle ethmoidal sinuses, frontal sinuses, lateral nasal wall & nasal septum 3. Posterior ethmoidal foramen - Transmits: posterior ethmoidal nerve, vein & artery - Supplies: posterior ethmoidal & sphenoid sinuses

Question 41

What causes blow out fracture of the orbit, its symptoms and results

Answer 41

- Cause: blunt trauma to or around the eye, coughing or sneezing (rare) - Symptoms: diplopia, gaze restrictions - Result: can lead to extraocular muscle entrapment resulting in restriction on upgaze or downgaze

Question 42

What are the structures surrounding the orbit?

Answer 42

- Superior: frontal sinus, anterior cranial fossa - Medial: ethmoidal sinus - Inferior: maxillary sinus

Question 43

Describe periorbital and its function?

Answer 43

- Layer of thick connective tissue lining the orbit - Loosely attached to the underlying bone except at the orbital margin, edges of fissures and foramina - Functions: serves as attachment sites for muscles, tendons and ligaments to the orbital bone support structure for blood supply

Question 44

Describe orbital septum and its function?

Answer 44

- Continuous at orbital margin with periorbita - Circular sheet from rim of orbit to tarsal plate - Functions: prevent facial infection from entering the orbit keeps orbital fat tissue in place