Week 3 - Dry Room

Question 1

What is the floor of the skull?

Answer 1

The part of the skull that you view when you remove the skull cap and look into the calvarium.

It is divided into 3 fossa.

In each fossa there are many foramina (or holes) through which nerves and blood vessels enter/leave the calvarium.

There are also grooves and depressions which indicate the position, in life, of blood vessels and other structures

Question 2

Which bone forms the posterior boundary of the anterior cranial fossa?

Answer 2

Sphenoid (limbus and lesser wing)

Question 3

Which bone forms the anterior boundary of the middle cranial fossa?

Answer 3

Sphenoid (limbus and lesser wings)

Question 4

Which bones form the floor of the middle cranial fossa?

Answer 4

Sphenoid (body and greater wings)
Temporal bone (squamous and petrous parts)

Question 5

Which bone forms the posterior border of the middle cranial fossa?

Answer 5

Temporal bone (petrous part)

Question 6

What 4 bones form the pterion of the skull?

Answer 6

Frontal
Parietal
Temporal
Sphenoid

Question 7

Which bone forms the anterior and which the posterior border of the posterior cranial fossa?

Answer 7

Anterior = Temporal
Posterior = Occipital

Question 8

Large and small foramina can be seen on the skull.

What are the larger foramina for and what are the smaller foramina for?

Answer 8

Larger = Nerves and blood vessels to enter/ leave the cranial cavity

Smaller = Emissary veins

Question 9

What structure(s) pass through the foramina of the cribriform plate?

Answer 9

Olfactory Nerve (I)

Question 10

What structure(s) pass through the optic foramen?

Answer 10

Optic nerve (II)
Ophthalmic arteries

Question 11

What structure(s) pass through the Superior Orbital Fissure?

Answer 11

Ophthalmic Veins
Ophthalmic Nerve (division of trigeminal)
Occulomotor (III) nerve
Trochlear nerve (IV)
Abducens nerve (VI)

Question 12

What structure(s) pass through the foramen rotundum?

Answer 12

Maxillary division of the trigeminal nerve

Question 13

What structure(s) pass through the Foramen ovale?

Answer 13

Mandibular division of the trigeminal nerve

Accessory meningeal artery

Question 14

What structure(s) pass through the foramen spinosum?

Answer 14

Middle meningeal artery
Middle meningeal vein
Meningeal branch of Mandibular nerve

Question 15

What structure(s) pass through the foramen lacerum?

Answer 15

only small blood vessels

Question 16

What structure(s) pass through the Carotid canal?

Answer 16

Internal Carotid artery

Question 17

What are the 4 parts of the temporal bone?

Answer 17

Zygomatic arch
Mastoid Process
Petrous part of Temporal bone
Squamous part of temporal bone

Question 18

What foramina are present in the anterior cranial fossa?

Answer 18

Foramina of the cribriform plate

Question 19

What foramina are present in the middle cranial fossa?

Answer 19

Optic foramen
Superior orbital fissure
Foramen rotundum
Foramen ovale
Foramen spinosum
Foramen lacerum
carotid canal

Question 20

What structure(s) pass through the Internal acoustic foramen?

Answer 20

Facial nerve (VII)
Vestibulocochlear nerve (VIII)
Labrynthine artery

Question 21

What structure(s) pass through the jugular foramen?

Answer 21

Glossopharyngeal nerve (IX)
Vagus nerve (X)
Accessory nerve (XI)
Internal Jugular vein

Question 22

What structure(s) pass through the hypoglossal foramen?

Answer 22

Hypoglossal nerve (XII)

Question 23

What structure(s) pass through the foramen magnum?

Answer 23

Medulla
Meninges
Vertebral arteries
Spinal accessory nerve
Dural veins
Anterior and Posterior spinal arteries

Question 24

Give an introduction to the grooves in the floor of the skull

Answer 24

Formed as the bone of the skull develops (and is maintained) around pre-existing blood vessels or nerves.
In the main, the grooves that are easily identified are those formed by arteries or by the intra-cranial venous blood sinuses.
The intra-cranial venous blood sinuses are found between the inner and outer layers of dura - the inner layer is the dura proper and the outer layer the periosteum of the inside face of the skull bone.

Question 25

What groove lies just lateral to the foramen spinosum? | Why is this of clinical importance?

Answer 25

Groove for the middle meningeal artery - The skull over part of the course of this artery is very thin - A branch of this artery crosses the preteen on its inner surface. Due to these 2 factors, this artery is commonly damages in injuries such as blow to the head following a fall from a bike. This results in a bleed collecting between the periosteum of the skull and the dura mater (an extradural haemorrhage). Such haemorrhages are classically biconvex, lens-shaped. Usually the spread is limited to this shape by cranial sutures

Question 26

Whats the significance of the internal occipital protuberance?

Answer 26

Grooves run laterally on both sides starting from the internal occipital protuberance. These groves are for the intracranial venous sinus called the transverse sinus. These flow laterally until that continue as the S-shaped groove for the sigmoid sinus. The sigmoid sinus leads to the jugular foramen where the internal jugular vein emerges from

Question 27

What is the sella turcica? | What are its parts?

Answer 27

``` Sella turcica (turkish saddle) is a deep depression in the midline in the middle cranial fossa which houses the pituitary gland. It is located in the body of the sphenoid bone. ``` On either side of the sella turcica is the anterior and posterior cloned processes which give attachment to a fold of dura mater, the tantrum cerebelli

Question 28

On either side of the sella turcica lies what?

Answer 28

A groove for the cavernous venous (intracranial sinus). | Anterior to this is the superior orbital fissure

Question 29

What bone are the pterygoid plates part of? | What muscles attach to them?

Answer 29

Sphenoid bone Medial pterygoid plate = Tensor Veli Palatini Lateral pterygoid plate = Medial and Lateral pterygoid muscles

Question 30

How does the neonatal skull differ from the adult?

Answer 30

A neonatal skull is not fully ossified, making it less rigid and more flexible. Fontanelles are present which are almost membranous coverings linking the unfused bones of the skull

Question 31

What are the advantages for a neonate of having a comparatively flexible skull?

Answer 31

During childbirth it allows for the head to pass through the birth canal more easily. During infancy it allows the brain to grow faster than bones In the event of accidents such as falls it reduced the likelihood of fracture

Question 32

What type of ossification occurs in: - flat bones of the vault of the skull and - irregular bones of the base of the skull?

Answer 32

Membranous ossification in flat bones | Endochondral ossification in irregular bones

Question 33

What is the difference between foetus, child and adult skulls with respect to fontanelles?

Answer 33

Foetus: Present Children: The bones fuse Adults: Absent

Question 34

What is the difference between foetus, child and adult skulls with respect to dentition?

Answer 34

Foetus: No teeth present in mouth (2 "back up") Child: 1 set of teeth present (1 "back up") Adult: 1 set of teeth present (No "back up")

Question 35

What is the difference between foetus, child and adult skulls with respect to the tympanic membrane?

Answer 35

In foetus it is more superficial, almost the surface of skull. As skull rapidly grows the tympanic membrane ends up deeper. Skull moves as it grows and tympanic membrane almost sort of stays put

Question 36

What is the difference between foetus, child and adult skulls with respect to the styloid and mastoid process of the temporal bone?

Answer 36

Much smaller or absent in the young. | Grows as we age

Question 37

At what age do the anterior and posterior fontanelles fuse respectively?

Answer 37

9-18 months | First few months (2-3)

Question 38

What kind of epithelium lines the dorsal surface of the tongue?

Answer 38

Keratinised squamous epithelium

Question 39

What type of muscle fibres underlies the epithelium of the tongue?

Answer 39

Skeletal muscle

Question 40

How do the salivary glands basically differ?

Answer 40

3 main paired salivary glands. Each responsible for a slightly different type of secretion (i.e. predominantly serous, predominantly mucous or mixed). This difference is reflected histologically in the presence and amount of serous or mucous acini (secretory component)

Question 41

Describe the acini of the serous glands and how their H+E staining differs

Answer 41

The acinus is the rounded secretory component of a gland. Serous acini secrete proteins, which mean that they stain strongly with H+E stain. Mucous acini secrete the glycoprotein mucous which poorly stains with H+E ``` Parotid = serous Sublingual = mucous Submandibular = mixed ```

Question 42

What are myoepithelial cells?

Answer 42

Contract around acini to expel contents | Needed more for mucous acini (sublingual)