Respiratory System Lecture Notes

Air-filled spaces within the nasal cavity lined with respiratory epithelium.

Three conchal sinuses located within the nasal cavity, contributing to the turbinate structure. They are lined with respiratory epithelium and help to increase surface area within the nasal cavity.

Irregular air-filled spaces that excavate certain bones of the skull, situated between the external and internal laminae of the bone. Lined with respiratory mucous membrane, they are connected to the nasal cavity and vary in size and form across species.

The development of paranasal sinuses occurs during embryonic life, at birth, and continues postnatally. The extent of sinus development varies between species.

Protect the orbits, nasal, and cranial cavities by acting as a buffer against head trauma; enlarge the skull area for muscle attachment without increasing weight; contribute to skull lightness; humidify and warm inhaled air; affect voice resonance; produce mucus to trap dust, pathogens, and particles; and contribute to immune function.

A paranasal sinus present in all domestic animals. It is separated by a median septum and typically opens into the ethmoidal meatuses, with some exceptions.

In dogs, small ruminants, and horses, the frontal sinus occupies the frontal bone, located dorsally in the skull between the nasal cavity, cranial cavity, and orbits. In pigs and cattle, the frontal sinus extends into the parietal, interparietal, occipital, and temporal bones.

The horn process of horned ruminants is excavated by the frontal sinus. This means the horn itself contains a part of the frontal sinus.

A paranasal sinus present in all domestic animals. It opens into the middle nasal meatus through the nasomaxillary aperture.

In carnivores, the maxillary sinus is not considered a true sinus due to its position within the bone. However, it is important to remember that maxillary sinus is not a true sinus in carnivores, and is referred to as a maxillary recess.

In pigs, the maxillary sinus is divided into rostral and caudal parts and opens into the middle nasal meatus through the nasomaxillary opening.

In ruminants, the maxillary sinus communicates with the palatine sinus through the infraorbital canal. It shares a common nasomaxillary opening that leads to the middle nasal meatus. The maxillary sinus is not divided into rostral and caudal parts in ruminants.

In horses, the maxillary sinus is divided into rostral and caudal parts by a bony septum. The caudal part is further subdivided by the 'boy crest'. The rostral and caudal parts communicate with the middle nasal meatus.

Absent in dogs and small ruminants, the sphenoid sinus is also sometimes absent in cattle and horses. It is relatively small, but larger in pigs, and excavates the sphenoid bone.

In pigs and cattle, the sphenoid sinus opens into the ethmoidal meatuses.

In horses, the sphenoid sinus communicates with the palatine sinus to form the sphenopalatine sinus, which then communicates with the caudal maxillary sinus.

The portion of the sphenoid sinus within the presphenoid bone is closely related to the optic nerve and optic chiasma, meaning inflammation can affect vision.

Absent in carnivores and pigs, the palatine sinus is present in ruminants and horses. It excavates the palatine process of the maxilla and the horizontal part of the palatine bone.

In ruminants, the palatine sinus has an incomplete bony roof, so it is separated from the nasal cavity by two layers of mucosa. This is important for understanding potential infections.

In ruminants, the palatine and maxillary sinuses communicate through the infraorbital canal and share a common nasomaxillary opening.

In horses, the palatine sinus excavates the perpendicular part of the palatine bone and opens rostrally into the caudal maxillary sinus. It continues caudally with the sphenoid sinus, forming the sphenopalatine sinus.

Absent in carnivores and horses, the lacrimal sinus is present in pigs, small ruminants, and cattle. It excavates the lacrimal and zygomatic bones.

In pigs and small ruminants, the lacrimal sinus opens into the ethmoidal meatuses. It can be connected to the frontal sinus (pigs) or be a lateral recess of the lateral frontal sinus (small ruminants).

In cattle, the lacrimal sinus opens into the middle nasal meatus through the maxillary sinus.

The sinuses that share a connection through the nasomaxillary opening collectively communicate with the middle nasal meatus. This connection can be direct or indirect.

Some sinuses communicate independently with the ethmoidal meatuses, rather than through the middle nasal meatus.

In horses, all paranasal sinuses open into the middle nasal meatus.

The maxillary and palatine sinuses open into the middle nasal meatus either directly or indirectly.

The frontal, sphenoid, and lacrimal sinuses open into the ethmoidal meatuses except for the lacrimal sinus in cattle, which opens into the middle nasal meatus through the maxillary sinus.

In the dog, the frontal sinus opens into the ethmoidal meatuses while the maxillary sinus opens into the middle nasal meatus.

In pigs, the frontal, sphenoid, and lacrimal sinuses open into the ethmoidal meatuses. The maxillary and palatine sinuses open into the middle nasal meatus.

In small ruminants, the frontal, sphenoid, and lacrimal sinuses open into the ethmoidal meatuses. The maxillary and palatine sinuses open into the middle nasal meatus.

In large ruminants the frontal, sphenoid, and lacrimal sinuses open into the ethmoidal meatuses except for the lacrimal sinus which opens into the middle nasal meatus indirectly via maxillary sinus. The maxillary and palatine sinuses open into the middle nasal meatus.