The serous fluid also contains IgA, which suggests a defensive function. The rate of secretion increases in warm climate conditions and in dogs tempted with food, suggesting physiologic and psychologic cues and a role in evaporative cooling. The precise stimulus for and function of these secretions are not known. The moist appearance of the nasal planum in healthy dogs is primarily a function of secretions from the paired lateral nasal glands. This staccato inflow of air at high speeds is thought to cause turbulence in the nasal cavity that directs air into the dorsal meatus and creates a constant influx of new scent information. 58, 163 The caudodorsal portions of the nasal mucosa are primarily dedicated to olfaction, and dogs in particular can be observed to sniff rapidly rather than inhale normally when engaged in hunting. At extremes of exertion or temperature, dogs and, to a lesser extent, cats change to mouth breathing (panting) to exaggerate evaporative cooling even further by use of the larger surface area of oral mucosa. At exercise or with high ambient temperature, dilatation of blood vessels that comprise the rich vascular supply to the nasal mucosa enhances heat and moisture exchange. Inhaled air is warmed and humidified by the rostral portions of the nasal mucosa, and the mucosa itself is cooled by this interaction. ![]() 148, 160 The frontal sinuses are connected to the nasal fossa via the nasofrontal opening, through which an ethmoidal turbinate extends.Īt rest, dogs and cats breathe through their noses. The size and specific anatomy of the frontal and sphenoid sinuses can be variable, and these sinuses may be absent in some animals. The frontal sinuses are the most commonly encountered sinuses from a surgical perspective and are divided into rostral, medial, and lateral compartments. The sphenoid sinus lies within the presphenoid bone and houses a portion of the ethmoidal conchae. The maxillary recess is in the lateral aspect of the nasal fossa approximately at the level of the last premolar and first molar. ![]() There are three paranasal sinuses: the maxillary recess, sphenoidal sinus, and frontal sinus. (From Evans HE, de Lahunta A: Miller’s anatomy of the dog, ed 4, St Louis, 2013, Saunders/Elsevier.) The opening of the nasolacrimal duct is also located in the rostral aspect of the nasal cavity. In the caudal and ventral nasal cavity, the ethmoidal labyrinth is formed by scrolls of ethmoidal conchae, which are outgrowths of the ethmoid bone.įigure 99-4 The alar fold is a rostral extension of the ventral nasal conchae. Rostrally, the alar fold is a bulbous extension of the ventral nasal conchae that fuses with the wing of the nostril ( Figure 99-4). These air passages are named the dorsal, middle, ventral, and common nasal meatus based on their location (Figure 99-3). Within the nasal cavity, the dorsal and larger ventral conchae define the air passages. The above muscles are innervated by the facial nerve. Overlying the frontal bone, the thin, flat frontalis muscle pulls the scutiform cartilage of the ear rostrally and is divided transversely during the approach to the frontal bone and sinuses. Deep to the levator nasolabialis muscle, the levator labii maxillaries muscle and its labial part, the caninus muscle, also act to increase diameter of the nares, in addition to their actions on the lips. Another branch of this muscle increases the diameter of the nares. The orbicularis oris muscle is the primary muscle of the lips, but in addition to its other actions, it also pulls the external nose ventrally to enable downward sniffing. This is a flat, thin muscle that lies just below the skin and acts to increase the diameter of the nares and lift the upper lip. The levator nasolabialis muscle extends from the dorsal midline of the muzzle on the frontal and maxillary bones to insert on the upper lip and nose. Musculature associated with the lips, nose, and muzzle inserts on the cartilaginous framework and allows for a modicum of movement of the external nose. Lateral support is provided by paired lateral nasal ligaments. The dorsal nasal ligament connects the dorsal midline of the nasal bone at the bony nasal aperture to the dorsal lateral nasal cartilage. The cartilages of the external nose are supported by several ligaments. Figure 99-2 The cartilages and associated ligaments of the external nose viewed from the lateral aspect (A) and rostral aspect (B).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |