Page 93 - Anatomy and Physiology of Farm Animals, 8th Edition

78 / Anatomy and Physiology of Farm Animals

used to denote the entire skull, but more incisive, and palatine bones. Right and
left nasal passages are separated longitu-
commonly refers only to the braincase and
VetBooks.ir not the facial bones. Most of the observa- dinally by the vomer bone and a carti-
laginous and boney septum. Scroll‐like
ble species differences, as far as the head is
concerned, depend on variations in the conchae (turbinate bones) arise from
facial part of the skull. the lateral walls of the nasal cavity and
The caudal and dorsal walls of the cra- project into the nasal passages. The con-
nium are formed by the occipital, parietal, chae are covered with highly vascular
interparietal, and frontal bones. The mucous membrane that helps warm and
interparietal bones, narrow bones lying humidify the inspired air. Conchae in the
close to the median plane, typically fuse caudal parts of the nasal cavity are part
with each other and the adjacent two pari- of the ethmoid bone and are sometimes
etal and single occipital bones, although this referred to as ethmoturbinates; these
occurs at different times in the various feature the olfactory epithelium, which
species. In domestic animals that possess contains the nerve cells specialized to
them, the horns arise from boney projec- detect odors.
tions of the frontal bones. These projections The maxilla and zygomatic bone of the
are the cornual processes. horse feature a sharp ridge, the facial
Laterally and ventrally, the walls of the crest, which is readily seen and felt on the
cranium are formed by the temporal lateral aspect of the horse’s head, ventral
bones, which contain the middle and and rostral to the eye.
inner ears, and the sphenoid bone, which Air‐filled diverticuli from the nasal
supports the brain and pituitary gland. cavity, known as paranasal sinuses, exist
Rostrally, the unpaired ethmoid bone within some of the bones of the face and
cannot be seen from the outside of an braincase. The bones that may contain
intact skull. Lying at the boundary these sinuses include the frontal, maxillary,
between nasal cavity and braincase, it ethmoid, sphenoid, and palatine bones.
presents numerous openings for passage Because it features a diverticulum that
of the olfactory nerves associated with the extends into the cornual process, the fron-
sense of smell. tal sinus in cattle may be exposed by
The facial portion of the skull can be dehorning mature animals (Fig. 14‐8).
divided into orbital, nasal, and oral regions. The oral (mouth) portion of the skull is
The orbit, which means circle, denotes roofed by the maxilla, incisive, and pala-
the bony socket that protects the eye. The tine bones. The maxillae and incisive bones
orbit is surrounded by portions of the contain the teeth of the upper dental
frontal, lacrimal, and zygomatic bones. arcade (although the incisive bones lack
Frontal, zygomatic, and temporal bones all teeth in ruminants). Ventrolaterally, the
participate in the formation of the promi- mandible completes the oral portion. The
nent zygomatic arch that borders the ven- mandible pivots on a fossa of the temporal
tral and caudal parts of the orbit. Ruminants bone just rostral to the opening of the ear.
and horses have a complete orbit, with The mandible contains all of the lower
margins of bone that surround the eye. teeth and gives attachment to the muscles
Swine have an incomplete orbit (Fig. 4‐4), associated with chewing (“masticatory
with the caudal margin being finished with muscles”).
a stout orbital ligament rather than by The hyoid apparatus is a bony frame-
bone. work (Fig. 4‐7) that gives support to the
The air passages through the nasal pharynx (throat) and provides attachment
part of the skull are bounded dorsally by to some pharyngeal, laryngeal, and lingual
the nasal bones, laterally by the maxil- muscles. It lies between the right and left
lae and incisive bones, and ventrally by portions of the mandible and is attached to
the palatine processes of the maxillae, the styloid process of each temporal bone.