Head

Question 1

Segment 1 (cranial nerves)

Answer 1

No pharyngeal arch

Ventral root nerve: III Oculomotor

Somite (SE): most orbital muscles, [AE: ciliary muscle, SVE: Lev. Palp. super.]

Dorsal root nerve: V trigeminal (opthalmic)

Ectoderm (SA): skin on top of head

Endoderm (AA): NONE

Glands (AE): NONE

Lateral plate mesoderm (SVE): NONE

Pouches: NONE

Question 2

Describe the frontal sinus in the ox

Answer 2

• Diverticulum of the nasal cavity retains connection with nasal cavity
• Lies within the frontal, parietal and occipital bones and is very extensive in the ox - covers most of dorsal surface of the cranium
• Lies between the inner and outer tables of the frontal, parietal and occipital bones
• Filled with air
• Subdivided into several separate cavities, each with its own separate opening into the nasal cavity
• One subdivision - the corneal process extends up into the horn
• Lined with respiratory epithelium
• Innervated by ophthalmic and maxillary divisions of the nasal cavity
• Opens into caudal part of nasal cavity via small slits between the ethmoturbinate bones. these slits are small and may easily become blocked
• Septum between L+R frontal sinuses is very thick - needs to be considered when killing with a captive bolt/bullet