The sinuses all communicate with the nasal cavity to allow drainage. The rostral and caudal maxillary sinuses communicate directly with the nasal cavity. The conchal sinuses lie within the fine, scroll-shaped bones known as conchae or turbinates. These conchae are attached to the lateral wall of the nasal passages. The paranasal sinuses are lined with respiratory epithelium pseudostratified ciliated columnar and goblet cells.
The frontal sinus occupies the skull from a point midway between the infraorbital foramen and the medial canthus of the eye to a point midway between the caudal edges of the orbit.
The frontal sinus is divided into right and left compartments by a midline septum. The conchofrontal sinus is formed by a communication between the rostromedial frontal sinus and the dorsal conchal sinus. The frontomaxillary aperture is a large area of communication between the frontal sinus and the caudal maxillary sinus, this is important to allow drainage. Blood supply to the frontal sinus is provided by the ethmoidal artery. The main blood supply is provided by the arterial ethmoid rete , which is an anastamosis between the internal and external ethmoid arteries.
A minor suply is provided by the caudal nasal branch of the sphenopalatine artery. The conchal sinuses include the dorsal, ventral and middle.
Each conchus is divided into two compartments, rostral and caudal, by a complete septum. The blood supply is provided by branches of the sphenopalatine artery. This is the largest sinus and is divided into rostral and caudal compartments by a bony septum. The position of this septum is variable, but it usually lies obliquely across the roots of the 4th and 5th cheeck teeth Tridan , , , In horses less than 5 years of age, the reserve crown of the 3rd-6th cheek teeth Tridan , , , almost fills the maxillary sinus.
The rostral maxillary sinus opens via the nasomaxillary opening into the middle nasal meatus. There is also a communication between the rostral maxillary sinus and the ventral conchal sinus, via the conchomaxillary opening ; located just medial to the infraorbital canal. Between the rostral margin of the frontomaxillary opening and the conchal bulla, there is a passageway which connects the rostral and caudal compartments.
This allows the caudal maxillary sinus to drain via the rostral maxillary sinus via the nasomaxillary opening into the middle nasal meatus. In the horse, the sphenoid and palatine sinus compartments communicate and are hence known as the sphenopalatine sinus. The sphenopalatine sinus drains via the caudal maxillary sinus, with which is communicates freely over the infraorbital canal.
This sinus lies under the ethmoidal labrynth. The guttural pouches are paired ventral diverticulae of the eustachian auditory tubes, formed by escape of mucosal lining of the tube through a relatively long ventral slit in the supporting cartilages. The auditory tube connect the nasal cavity and middle ear and the diverticulum dilates to form pouches which can have a capacity of ml in the domestic horse.
The pouches are normally air filled. It is covered laterally by the Pterygoid muscles, parotid and mandibular glands. The floor lies mainly on the pharynx and beginning of the Oesophagus. The medial retropharyngeal lymph node lies between the pharynx and ventral wall of the pouches.
Right and left pouches are separated dorsomedially by rectus capitis ventralis and longus capitis muscles. Below this, by fused walls of the two pouches, the median septum is formed. Each pouch is moulded to the stylohyoid muscle which divides the medial and lateral compartments, the medial compartment being approximately double the size of the lateral one and extends further caudally and ventrally.
The guttural pouch has close association with many major structures including several cranial nerves glossopharyngeal, vagus, accessory, hypoglossal , the sympathetic trunk and the external and internal carotid arteries. The pouch directly covers the temporohyoid joint. The pouch has an extremely thin wall which is lined by respiratory epithelium which secretes mucus. This normally drains into the pharynx when the horse is grazing. Several cranial nerves and arteries lie directly against the pouch as they pass to and from foramina in the caudal part of the skull vessels within mucosal folds that indent the pouches :.
Natural drainage of the pouch is throught the slit-like pharyngeal openings of the eustachian tube in the lateral wall of the nasopharynx. The connection opens when the horse swallows and grazing normally provides drainage. However, most of the pouch is ventral to his slit, and therefore drainage may be rather ineffective. If a horse doubles its speed, it will need to double the amount of air moved in and out of the lungs.
At the level of the smallest airways, after perhaps 25 divisions, the airways are fractions of a millimeter in size. The oxygen transfers from the alveoli across this thin membrane and into the blood by diffusion. The PCM that the oxygen must transfer across are so thin that they can rupture under the stress of exercise. When this happens, red blood cells spill from the capillaries into the alveoli. This is known as lung bleeding or exercise induced pulmonary hemorrhage EIPH.
Several independent clinical studies show that by reducing airflow resistance at the nasal passages, specifically at the nasal valve with the use of FLAIR Strips , these PCM ruptures — and thus bleeding — are reduced. Once in the bloodstream, the oxygen is bound to hemoglobin the molecule inside red blood cells that makes blood red and the oxygen-rich blood is pumped around the body by the heart. This oxygen-rich blood must then reach the muscles to provide energy.
At the muscle, the reverse process takes place with oxygen leaving the red blood cells and crossing into the muscle cells, again by diffusion. Efficient oxygen transfer from the airways to the red blood cells is very important in maximizing energy and a horse's ability to exercise. FLAIR Strips help horses with even the biggest hearts and greatest capacity use the oxygen that they bring in as efficiently as possible. For example, even the smallest smells can scare the horse.
At the same time, however, it can also sense predators long in advance and get to safety. There are many olfactory nerves in the large nostrils, which enable horses to filter what they want to eat in the pasture and what not.
With their nostrils, they roam over grasses and herbs and then use all this information to decide which ones they want to eat. Horses breathe, smell and feel their way forward with their nostrils. But they also use them to communicate with other horses or their riders. For example, to greet other horses, they blow into their nostrils.
Flared nostrils can mean it may smell something unfamiliar or even be excited. It may also be that it is straining hard at that moment and trying to get more air. It could also develop secondary to strangles, which would probably already be evident to the owner.
Mazan says profound nasal discharge like this could result from an esophageal obstruction, also called choke. The chunky bits dripping from the nostrils could be food coming back up. In horses with choke, food typically blocks the esophagus, although it can less commonly block the windpipe. Affected horses might cough and drool, as well. For more on choke, visit TheHorse. Rarely, in severe colics horse owners might see a foamy discharge with chunks of food as reflux.
However, this is usually accompanied by abdominal discomfort and distention. These scenarios illustrate the wide range of causes and types of snotty noses. Favorite Share:. Causes of Nasal Discharge The most common causes of snotty noses are noninfectious, says Mazan.
Scenario 1: The horse has a watery or white nasal discharge and shows no other clinical signs. Scenario 2: The horse has a lot of thick, yellow discharge coming out of both nostrils and seems less active than normal.
Viruses A viral infection often starts with a serous discharge that quickly changes to a thicker yellow or yellow-green. Scenario 3: The horse has a flowing bloody nasal discharge. Scenario 4: The horse has unilateral bloody discharge, but it is dark rust in color and mixed with lots of mucus.
Scenario 5: The horse has a creamlike discharge from one nostril. Scenario 6: The horse has lots of foamy and chunky nasal discharge from both nostrils. Take-Home Message These scenarios illustrate the wide range of causes and types of snotty noses. About The Author. Related Posts. Dead space. Search Search for:. Weekly Poll:.
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