1. Head structures II

2. Lacrimal Apparatus

3. Lacrimal Apparatus
the group of structures that manufacture and drain away tears
Lacrimal gland:
the pink gland lying on the dorsolateral aspect of the eyeball
Gland associated with 3rd eyelid

4. Lacrimal puncta: the openings of the lacrimal canaliculi on the upper and lower eyelids near the medial angle (canthus).
Lacrimal canaliculi: the small canals from the lacrimal puncta he lacrimal sac.
Lacrimal sac: located in a fossa in the lacrimal bone's orbital face, it marks the beginning of the nasolacrimal duct.

5. Nasolacrimal duct:
the duct extending from the lacrimal sac to the rostral part of the nasal cavity, first traveling in a bony canal in the lacrimal and maxillary bones and then deep to the nasal mucosa before opening into the rostral nasal cavity

6. Paranasal Sinuses
The paranasal sinuses are diverticula of the nasal cavity that excavate the skull bones largely after birth.
The separation of the inner and outer tables of the bones alters the conformation of the head.
It is specially striking in pigs and cattle, in which certain sinuses eventually extend dorsal and even caudal to the cranial cavity.

7. Paranasal Sinuses
The sinuses retain their connections with the nasal cavity
these openings are generally narrow a relatively slow exchange of air occurs
The narrowness and locations of the openings make them prone to blockage when the mucosa is thickened by inflammation or congestion.
Not all the sinuses are of equal importance.

8. The function The function of the sinuses is obscure Offer some thermal
Mechanical protection to the orbit and nasal and cranial cavities
Enlarge the skull areas available for muscular attachment without unduly increasing weight
Affect the resonance of the voice.

9. All species have frontal and maxillary systems
neither communicating with its contralateral counterpart.
The frontal system consists of one or more spaces within the bones at the border between the nasal and cranial cavities.
In most species the various frontal compartments open separately into ethmoidal meatus in the nasal cavity
in the horse the frontal sinus communicates with the nasal cavity indirectly via the caudal maxillary sinus.

10. The maxillary sinus system occupies the caudolateral part of the upper jaw, above the caudal cheek teeth
In some species it sends extensions, variously described as separate sinuses or as diverticula
into the hard palate
the sphenoid bones
the medial aspect of the orbit
the ventral concha.

11. In the horse the maxillary sinus is divided into caudal and rostral parts, both connected to the middle nasal meatus
In the dog the cavity communicates freely with that of the nose and is known as the maxillary recess.

12. EQUINE
On each side there are frontal, caudal maxillary, and rostral maxillary sinuses of importance
sphenopalatine and ethmoidal spaces of less account.
the frontal sinus communicates with the nasal cavity indirectly via the caudal maxillary sinus.
The two maxillary sinuses together occupy a large part of the upper jaw, where they have a critically important relationship to the embedded portions of the caudal cheek teeth.
They share a slit like communication (nasomaxillary opening) with the middle meatus of the nasal cavity
The frontal sinus occupies the dorsal part of the skull medial to the orbit.
It overlaps both cranial and nasal cavities.
Since it also occupies the closed part of the dorsal concha, it is more correctly known as the conchofrontal sinus

13. BOVINE, OVINE, CAPRINE
The paranasal sinus system is very poorly developed in the young calf, Even in the mature animal, the maxillary compartment continues to adjust to extrusion of the cheek teeth.
The complete set of sinuses is very complicated.
It comprises:
Frontal compartments within the bones of the cranial roof and side walls
Platomaxillary complex within the caudal part of the hard palate and the face, both before and below the orbit
Lacrimal sinus within the medial orbital wall;
Sphenoidal sinuses that extend past the orbit into the rostral part of the cranial floor
Conchal sinuses within the nasal conchae.

14. Project medially from each lateral wall of the nasal cavity.
Nasal Conchae
Project medially from each lateral wall of the nasal cavity.
Dorsal conchae
Ethmoid conchae
Ventral conchae
Creates turbulence which increases the amount of contact between nasal mucosa and inhaled air
Function: to filter, heat and moisten air

16. The superficial muscles move skin and ears, eyelids, nose, and lips to produce facial expression. The platysma m. (1) runs from the neck to the commissure of the lips. It retracts the lips to expose teeth; parts of the muscle are missing (asterisks). Superficial muscles that move the ear may be grouped into rostral (2), lateral (3), and caudal auricular muscles. An orbicularis oculi m. (4) closes the palpebral fissure.
A levator nasolabialis m. (5) retracts the nose and upper lip. An orbicularis oris m. is situated within the lips (6).

17. Muscles of the lips and cheek. The orbicularis oris m
Muscles of the lips and cheek. The orbicularis oris m. (1) is located within the wall of the upper lip and the lower lip. The buccinator m. (2) is located within the wall of the cheek. The levator nasolabialis m. (3) retracts the nose and upper lip. The orbicularis oculi m. (4) closes the palpebral fissure.

18. The palpebral fissure (opening) is situated between superior (1) and inferior (2) palpebrae.
The eyelids meet at medial (3) and lateral (4) palpebral commissures. The lateral commissure (forceps) has been incised.
Third eyelid (5), has a pigmented edge.

19. The parotid salivary gland (1) surrounds the external ear canal (2) and sends a parotid duct (3) toward the vestibule. It empties beside the upper fourth premolar.
The mandibular salivary gland (4) is located where the maxillary v. (5) and linguofacial v. (6) join to form the external jugular v. (7).
The monostomatic sublingual salivary gland (8) is located just cranial to the mandibular salivary gland. Notice the mandibular lymph nodes (9) flanking the facial v.

20. Deep dissection. The temporal m
Deep dissection. The temporal m. has been reflected to expose the temporal fossa (1). The top of the ramus (2) of the mandible has been remove and the ramus has been reflected laterally to expose vessels and nerves on the surface of the medial pterygoid m. (3). The zygomatic salivary gland (4) is located ventral to the orbit which has been incised to expose the eye (5) and extrinsic eye muscles (6).

21. Muscle of Mastication:
(2) the temporal m; arise from temporal fossa and insert in cronoid p. of mandible
(3) the masseter m. arise from zygomatic arch and insert in masseteric fossa.
(4) the digastricus m. Arise from paracondylar process of occipital bone and insert in the body (mandible)

22. Temporal m. (2), the partially reflected masseter m
Temporal m. (2), the partially reflected masseter m. (3), the mandible (4), and the digastricus m. (5). Notice the fourth upper premolar and first lower molar teeth (asterisks).

23. The zygomatic arch has been removed and the masseter m
The zygomatic arch has been removed and the masseter m. (1) has been reflected. Notice the ramus of the mandible (2) and the temporomandibular joint (3). Also find the temporal m. (4) and the digastricus m. (5).