Anat Sci Int (2014) 89:140–150 DOI 10.1007/s12565-013-0209-7
ORIGINAL ARTICLE
Computed tomography and sectional anatomy of the head cavities in donkey (Equus asinus) S. A. A. El-Gendy • M. A. M. Alsafy A. A. El Sharaby
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Received: 19 April 2013 / Accepted: 1 October 2013 / Published online: 16 October 2013 Ó Japanese Association of Anatomists 2013
Abstract The purpose of this study was to describe the computed tomographic (CT) anatomy of normal donkey head cavities to be used as a basis for interpretation of CT images of donkey. Six adult donkeys’ heads of undetermined sex were used in this study. The donkey heads were divided into three regions—nasal, orbital, and cranial—to show the morphology of the following cavities: nasal cavity, paranasal sinuses, orbital cavity, oral cavity, pharyngeal cavity, especially the guttural pouch, cranial cavity and temporomandibular joint. The donkey head had six pairs of sinuses: three paranasal (the frontal, maxillary and sphenopalatine sinuses) and three nasal (dorsal, middle and ventral conchal) sinuses. The maxillary sinus was subdivided into rostral and caudal compartments by a thin incomplete bony septum that was identified and labeled according to cheek teeth landmarks. The topographic description and relationship between the nasal, oral, orbital, cranial, temporomandibular joint, pharyngeal cavities and paranasal sinuses were demonstrated. The articular disc, articular surface and joint capsule of the temporomandibular joint were indicated easily in our CT and cross sectional images. Keywords Computed tomography Sectional anatomy Head cavities Donkey Head Nasal cavity S. A. A. El-Gendy (&) M. A. M. Alsafy Department of Anatomy and Embryology, Faculty of Veterinary Medicine, Alexandria University, PO Box 22785, Edfina, Behera, Egypt e-mail: [email protected] A. A. El Sharaby Department of Anatomy and Embryology, Faculty of Veterinary Medicine, Damanhour University, Damanhour, Egypt
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Introduction Donkeys are used in a variety of activities with social and/ or economic benefits. Small holder farmers use donkeys to cultivate their land, coping with labour shortages and loss of other livestock due to drought. By using donkeys in agriculture and transport, farmers have increased their productive potential and expanded their marketing options. Donkeys have also provided employment for many people who hire out donkeys or use donkey carts on a commercial basis for a transport service (Marshall and Zahra 2000). Donkeys belong to the family Equidae and, as such, are similar to equines in many ways. However, there are several significant features specific to the donkey that practitioners should be aware of when trying to explore and treat respiratory disease. These include differences in anatomy, physiology, pharmacokinetics, disease incidence and morbidity with certain infectious diseases. Worldwide, there are an estimated 44 million donkeys, of which 96 % are found in developing countries contributing significantly to the rural economy. Thus, there is a need for equine practitioners to treat donkey patients in an informed and sensitive manner (Starkey 1997; Thiemann and Bell 2001). Computed tomography (CT) of the equine head is an imaging technique that is becoming more and more commonly performed (Solano and Brawer 2004). The major advantage of CT over conventional radiographs is the lack of superimposition and improved demonstration of individual parts of the skull. In addition, the regions of interest have high inherent radiographic contrast and CT provides clear, unobstructed images (Gibbs 1999). CT is best suited to anatomical studies of varied tissue density parts such as the head in large animals (Morrow et al. 2000; Alsafy et al. 2012). The main advantage of CT of the equine head is the ability to produce detailed cross-sectional images of the
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Fig. 1 a, b Computed tomography (CT) scans and c, d cross-sectional images of the rostral nasal region at the level interalveolar space and first premolar teeth. 1 Nasal bone, 2 nasal diverticulum (false nostrils), 3 straight fold of dorsal nasal concha, 4 alar fold of ventral nasal concha, 5 basal fold of ventral nasal concha, 6 dorsal nasal concha, 7 ventral nasal concha (contain venous plexus), 8 dorsal nasal meatus, 9 ventral nasal meatus, 10 middle nasal meatus, 11 nasal septum, 12 palatine process of maxillary bone, 13 buccal vestibule, 14 oral cavity proper, 15 vomeronasal organ, 16 hard palate, 17 buccinator muscle, 18 tongue apex, 19 rostral aspect of the ramus of the mandible, 20 rostral margin of the 1st pre molar teeth, 21 lingual frenulum, 22 interalveolar space
nasal cavity, paranasal sinuses, and brain case without superimposition of other anatomical structures (Solano and Brawer 2004; Probst et al. 2005). Thus, the aim of our study was to provide an atlas of normal cross-sectional anatomy of the structures of the donkey head using CT images and transverse gross anatomic sections and to familiarise the reader with the complex anatomical relationships of the area by providing an atlas of CT anatomy of equine head cavities.
Materials and methods Six heads of adult donkey’s undetermined sex were collected from the local dissecting hall in Faculty of Veterinary Medicine in Edfina, Behera Governate, Egypt. This
study followed the guidelines for the care and use of laboratory animals and the animal welfare and Ethics Committee of the Faculty of Veterinary Medicine, Alexandria University according the Egyptian’s laws, approved it. Computed tomography scans Two donkeys’ heads were used for CT scans after being bled. The heads were removed from the level of the third cervical vertebra and CT examination was performed on serially sectioned heads using a CT scanner (CT-W45010A, Hitachi, Tokyo, Japan). The scanned images were taken as 1.5-cm-thick images of the head from the external occipital protuberance caudally to the level of the canine teeth rostrally (scanning conditions: 130 kV, 100 MA).
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Fig. 2 a, b CT scans and c, d cross-sectional images of the middle nasal region at the level of the second and third premolar teeth. 1 Nasal bone, 2 maxillary bone, 3 dorsal nasal concha, 4 ventral nasal concha, 5 dorsal nasal meatus, 6 middle nasal meatus, 7 ventral nasal meatus, 8 nasal septum with vomer bone, 9 common nasal meatus, 10 infraorbital canal (foramen), 11 rostral maxillary sinus, 12 palatine process of maxillary bone, 13 buccal vestibule, 14 oral cavity proper, 15 buccinator muscle, 16 vomeronasal organ, 17 hard palate, 18 tongue, 19 lacrimal canal and nasolacrimal duct, 20 second premolar teeth, 21 third premolar teeth, 22 levator labii maxillaris muscle, 23 geniohyoideus muscle, 24 vomer bone, 25 lingual artery
Sectional anatomy Four frozen donkey’s heads (two fresh and two formalin fixed) were used to determine sectional anatomy. Three heads were serially cut into cross sections using a table band saw; the cross sections were approximately 1.5 cm apart, and extended from the external occipital protuberance caudally to the level of the interalveolar space rostrally. The slices were numbered and gently cleaned of debris with water and light brushing and were photographed immediately with the caudal surface of each slice facing the camera. One head was cut sagittally. We used the neck of the premolar and molar teeth and bony parts as
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landmarks to explore and describe the location and extension of the structures and cavities.
Results The donkey heads under study were divided into three regions—nasal, orbital and cranial—to demonstrate the morphology of following structures: nasal cavity; paranasal sinuses; orbital cavity; oral cavity; pharyngeal cavity, especially the guttural pouch; cranial cavity; and temporomandibular joint. The current study was performed using CT scanning and sectional anatomy.
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Fig. 3 a, b CT scans and c, d cross-sectional images of the caudal nasal region at the level of the first and second molar teeth. 1 Nasal bone, 2 frontal bone, 3 maxillary bone, 4 dorsal nasal concha, 5 ventral nasal conchal sinus, 6 dorsal nasal conchal sinus, 7 frontal sinus, 8 conchofrontal sinus, 9 frontal septum between right and left frontal sinuses, 10 dorsal nasal meatus, 11 middle nasal meatus, 12 ventral nasal meatus, 13 nasal septum, 14 common nasal meatus, 15 infraorbital canal, 16 rostral maxillary sinus, 17 trabeculae in maxillary sinus, 18 caudal maxillary sinus, 19 maxillary septum, 20 conchomaxillary opening, 21 nasomaxillary opening, 22 lacrimal canal and nasolacrimal duct, 23 palatine canal, 24 facial crest, 25 vomer bone, 26 hard palate, 27 soft palate, 28 bulla of the ventral nasal conchal sinus, 29 buccinator muscle, 30 masseter muscle, 31 tongue, 32 first molar teeth, 33 second molar teeth
The nasal cavity CT and cross sectional images of the nasal cavity accurately described the nasal concha, conchal sinuses, nasal meatuses, paranasal sinuses, vomeronasal organ and nasal septum. The donkeys’ heads had six pairs of sinuses: three nasal; dorsal, middle, and ventral conchal sinuses and three paranasal; and frontal, maxillary, and sphenopalatine sinuses. The relationship between various air cavities was easily visualized. Dorsal nasal concha and sinus The dorsal nasal concha was continued rostrally by the straight fold [Fig. 1(3)]. Scrolls were present in the rostral
portion of the dorsal nasal concha, surrounding recesses of the nasal cavity and having medium-density thick walls and a spiral form [Figs. 2(3), 3(4)]. The caudal half of the dorsal nasal concha contained the dorsal conchal sinus with its low density thin wall. It extended from the level of the caudal third of the first molar to third molar teeth (Fig. 3(6)]. Middle nasal concha and sinus The middle nasal concha was situated among the ethmoidal labyrinth and dorsal nasal sinus and appeared oval in CT [Fig. 4(11)]. It contained the middle conchal sinus, which connected with the caudal maxillary sinus by a small oval opening measuring 0.4 cm in length and 0.2 cm in width.
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Fig. 4 a, b CT scans and c, d cross-sectional images of the rostral orbital region at the level of the third molar teeth. 1 Frontal bone, 2 zygomatic process of frontal bone, 3 temporal process of zygomatic bone, 4 eye (choroid and retina), 5 lens, 6 dorsal conchal sinus, 7 ethmoid labyrinth, 8 conchofrontal sinus, 9 periorbital fat and ocular muscles, 10 frontomaxillary opening, 11 middle conchal sinus, 12 vomer bone, 13 frontal septum between right and left frontal sinus, 14 olfactory bulb, 15 palatine bone, 16 masseter muscle, 17 medial pterygoid muscle, 18 soft palate, 19 caudal maxillary sinus, 20 stylohyoid bone, 21 oropharynx, 22 basihyoid bone, 23 omohyoid and sternohyoid muscles, 24 nasopharynx, 25 dorsal nasal meatus, 26 infraorbital canal, 27 sphenopalatine vessels, 28 sphenopalatine opening, 29 sphenopalatine sinus, 30 root of the tongue, 31 third maxillary molar teeth, 32 optic nerve, 33 mandibular foramen, 34 lacrimal gland
Ventral nasal concha and sinus
Nasal meatuses
The ventral nasal concha continued rostrally by the alar and basal folds [Fig. 1(4), (5)]. The rostral portion of the ventral nasal concha formed scrolls surrounding recesses. The caudal portion of the ventral nasal concha contained the ventral conchal sinus [Fig. 3(5)], which extended from the level of the first molar to the rostral part of third molar teeth. The ventral conchal sinuses drained into the rostral aspect of the rostral maxillary sinus via a narrow conchomaxillary opening [Fig. 3(20)]. The caudal portion of the ventral conchal sinus formed the bulla of the ventral nasal concha [Fig. 3(28)].
The dorsal and middle nasal meatuses appeared narrow [Fig. 1(8)–(10)]. The middle meatus contained a slit-like nasomaxillary opening [Fig. 3(21)], which was the narrowest communicating opening; it located at the level from the middle of the first molar tooth to the rostral of the third molar tooth. The opening measured 3.5–4 cm in length and 0.1–0.2 cm in width. The nasolacrimal duct was situated in the lateral aspect of the middle nasal meatus and covered by mucous membrane [Fig. 3(22)]. The ventral nasal meatus was the largest one.
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Fig. 5 a CT scan and b crosssectional image at the level of the caudal orbital region. 1 Retro-orbital fat, 2 frontal sinus, 3 sphenoid bone, 4 frontal bone, 5 zygomatic process of temporal bone, 6 coronoid process of the mandible, 7 frontal lobe of brain, 8 sphenopalatine sinus, 9 lateral pterygoid muscle, 10 medial pterygoid muscle, 11 pharyngeal recess, 12 nasopharynx, 13 auditory tube, 14 transverse facial artery and vein, 15 maxillary vein, 16 optic tract, 17 soft palate, 18 masseter muscle, 19 stylohyoid bone, 20 thyrohyoid bone, 21 facial vein, 22 mandibular salivary gland, 23 omohyoid and sternohyoid muscles, 24 ramus of the mandible
Paranasal sinuses
second molar tooth. It measured about 4.4–5 cm in length and 0.3–0.4 cm in width.
Maxillary sinus Frontal sinus The maxillary sinus appeared with low density and has high density structures; infraorbital canal, maxillary septum and bony spicules [Fig. 3(15), (17), (19)]. These were divided into rostral and caudal compartments by a thin incomplete bony septum [Figs. 3(19), 9(7)]; the dorsal part of the septum was formed by the bulla of the ventral conchal sinus [Fig. 3(28)]. This septum angled obliquely caudally and its rostral aspect was varied in position; it usually crossed the roots of the second and third molar teeth, approximately 4–5 cm caudal to the rostral end of the facial crest. In the present study, most specimens had a low septum of about 1.5 cm high. The depth of the sinus was about 4–5.5 cm and contained bony spicules [Fig. 3(17)]. The caudal maxillary sinus was partially divided into medial and lateral compartments by the infraorbital canal [Fig. 3(15), (18)]. Those two parts communicated freely over the canal. Only the root of the third maxillary molar tooth was embedded in the caudal maxillary sinus. Both rostral and caudal maxillary sinuses were connected with the middle nasal meatus via a slit-like nasomaxillary opening [Fig. 3(21)]. The rostral maxillary sinus appeared smaller than the capacious caudal maxillary sinus. It communicated with the ventral conchal sinus via the wide conchomaxillary opening [Fig. 3(20)] dorsal to the infraorbital canal [Fig. 3(15)]. The opening located at the level of the rostral part of the first molar tooth until the caudal part of the
The frontal sinus appeared as air-filled spaces formed by the evagination of the frontal bones into the nasal cavity [Figs. 3(7), 5(2)]. The sinus continued rostrally with the dorsal conchal sinus forming the conchofrontal sinus [Fig. 3(8)], which communicated directly with the caudal maxillary sinus by a large, oval or bean-shaped frontomaxillary opening. This opening was about 4–5 cm in length and 2.5–3.5 cm in width [Fig. 4(10)] and located in a dorsal plane slightly caudal to medial canthus of the eye. The frontomaxillary opening was at the level of the caudal third of the second molar tooth and extended 2–3 cm caudal to the last molar tooth on the lateral floor of the conchofrontal sinus. The left and right frontal sinuses were completely separated by a thick midline bony septum [Fig. 3(9)]. Sphenopalatine sinuses The sphenopalatine sinuses were excavated in the palatine and sphenoid bones ventromedial to the orbit and ventral to the brain [Figs. 4(29); 5(8)]. The septum dividing the left and right sphenoidal sinuses was found in all cases; however, it was not frequently in the midline [Fig. 6(15)]. The sphenoidal and palatine sinuses communicated with each other. The dorsal and lateral walls of the sphenopalatine sinus were thin, and communication with the caudal maxillary sinus was via the sphenopalatinal opening, which
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Fig. 6 a, b CT scans and c, d cross-sectional images of the rostral cranial region at the level of the temporomandibular joint. 1 Parietal bone, 2 zygomatic process of temporal bone, 3 body of basisphenoid bone, 4 temporal muscle, 5 mandibular fossa, 6 coronoid process of the mandible, 7 temporomandibular joint with articular disc, 8 condyloid process of mandible, 9 temporal lobe of brain, 10 parietal lobe of brain, 11 dorsal sagittal sinus of dura mater, 12 ventral cavernous sinus of dura mater and maxillary, 13 sphenopalatine sinus, 14 alar canal, 15 sphenopalatine septum, 16 pharyngeal recess, 17 auditory tube, 18 optic nerve, 19 masseter muscle, 20 medial pterygoid muscle, 21 stylohyoid bone, 22 lateral pterygoid muscle, 23 left guttural pouch, 24 right guttural pouch, 25 septum of guttural pouch, 26 thyrohyoid bone, 27 larynx, 28 transverse facial artery and vein, 29 maxillary vein, 30 lateral ventricle, 31 corpus callosum, 32 third ventricle, 33 thalamus, 34 hypothalamus, 35 hippocampus, 36 mandibular salivary gland, 37 omohyoid and sternohyoid muscle
was the most caudal opening of the maxillary sinus; the opening appeared sagittally oblique and was located between the caudal origin of the infraorbital canal and the pterygopalatine fossa caudal to the roots of the last molar tooth. It measured 1.5–2 cm in length and 0.8–1 cm in width [Fig. 4(28)]. Both sphenopalatine sinuses appeared as rectangular.
Nasal septum Most of the nasal septum was cartilage, the dorsal border of which was T-shaped and connected with nasal and frontal bones. Its ventral border connected with the channel formed by the vomer [Fig. 4(8), (24)]. Orbital cavity
Vomeronasal organ The vomeronasal organ appeared as a pair of long ducts on each side of the nasal septum at the ventral meatus, supported by a thin cartilage extending from the incisive duct to the level of the second upper molar tooth [Figs. 2(16), 4(15)].
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CT and cross sectional images recognized most structures of the eye orbit. The lens appeared with moderate density, i.e., it had a homogenous density in CT higher than that of the surrounding eye ball tissue [Fig. 4(5)]. The vitreous body of the eye, anterior chamber of eye, choroid and
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Fig. 7 a CT scan and b crosssectional image at the level of the middle cranial region. 1 Parietal bone, 2 petrosal part of temporal bone, 3 temporal muscle, 4 masseter muscle, 5 stylohyoid bone, 6 thyrohyoid bone, 7 larynx, 8 left guttural pouch, 9 medial compartment of the right guttural pouch, 10 lateral compartment of the right guttural pouch, 11 pharynx, 12 cerebral crura, 13 mesocephalic duct, 14 cerebral cortex (occipital lobe of brain), 15 ventral rectus and longus capitis muscles, 16 parotid salivary gland, 17 mandibular salivary gland
retina, periorbital fat, muscles of the eye, lacrimal gland and optic nerve were identified [Fig. 4(4), (9), (32), (34)]. Differences between density of eye ball layers and surrounding periorbit were recognized [Fig. 4(4), (9)]. Oral cavity The rostral aspect of the oral cavity elucidated the apex of tongue [Fig. 1(18)], lingual frenulum [Fig. 1(20)], hard palate [Fig. 1(16)], interalveolar space [Fig. 1(21)], buccal vestibule [Fig. 1(13)] and oral cavity proper [Fig. 1(14)] in CT and cross section anatomy. In the middle part of the oral cavity, the body of the tongue occupied the plurality of the oral cavity proper, and geniohyoideus muscle, lingual artery and hard palate were identified. The caudal part of the oral cavity illuminated clearly the root of the tongue [Fig. 4(30)], basihyoid bone [Fig. 4(22)], soft palate, [Figs. 3(27), 4(18)] palatine canal [Fig. 3(22)] in CT and cross sectional anatomy. Pharyngeal cavity In serial CT sections and anatomical cross sections of the pharyngeal cavity of the donkey head, the oropharynx [Fig. 4(21)] pharyngeal recess, nasopharynx, auditory tube [Fig. 5(11), (12), (13)], hyoid apparatus and guttural pouches (Figs. 5–9) were clearly recognized. The right and left guttural pouches started to appear as extensions of the auditory tube on both sides of the pharyngeal recess [Fig. 6(17), (23), (24)]. In the more caudal direction, each pouch spreads in basal and lateral directions and was separated at the median part by a thin septum [Fig. 6(25)]. Moreover, at the level of the head of the mandible in this
section, each guttural pouch started to be divided into medial and lateral compartments by the stylohyoid bone. In the more nuchal section, the stylohyoid bone more clearly divided the pouch into two compartments [Fig. 7(9), (10)]. Furthermore, in this section, the thin septum could not be seen because each medial compartment was distant from the center line of the head due to the presence of the ventral rectus and longus capitis muscles [Fig. 7(15)]. In the same section, the lateral compartment of the pouch was completely separated from the medial compartment by the stylohyoid bone [Fig. 7(5)]. As the CT sections approached the occipital condyle, the lateral compartments disappeared and the medial compartments gradually became smaller toward the base of the skull [Fig. 8(10)]. Temporomandibular joint The squamous part of the temporal bone, mandibular fossa, coronoid process of the mandible, temporomandibular joint with articular disc and condyloid process of mandible were easily identifiable because of the high CT density in cortical bone and the intermediate CT density in their medullary cavities. The articular disc, articular surface and joint capsule produced low to intermediate attenuation [Fig. 6(5)–(8)]. It was not possible to identify the ligaments, blood vessels, and nerves in CT images. Cranial cavity From the collection of CT, sagittal and cross section images of the cranial cavity, the brain parts and sinuses surrounding were accurately described. The brain had a similar homogenous appearance that was slightly less
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Fig. 8 a, b CT scans and c, d cross-sectional image of the caudal cranial region at the level of the occipital condyle. 1 Lateral part of occipital bone paracondylar process, 2 parietal bone, 3 basilar part of occipital bone, 4 temporal muscle, 5 transverse sinus, 6 cerebellar vermis, 7 cerebellar hemisphere, 8 fourth ventricle, 9 pons, 10 guttural pouch (caudal part), 11 medulla oblongata, 12 auricular cavity, 13 atlantooccipital joint, 14 occipital condyle, 15 atlantoaxial joint, 16 pena, 17 spinal cord
opaque than the surrounding musculature and bones of the head. In the rostral aspect of the cranial cavity the olfactory bulbs were separated by a bony septum just caudal to the cribriform area [Fig. 4(14)]. The lateral ventricles appeared as regions of low opacity [Fig. 6(30)]. The frontal, parietal, temporal and occipital lobes of the cerebral hemisphere were clearly identified [Figs. 5(7), 6(9), (10)]. The thalamus was clear [Fig. 6(33)] and the pituitary gland was detected ventral to the thalamus [Figs. 6(34), 9(18)]. The optic tract, optic chiasm, and optic nerve were identified under the thalamus [Figs. 5(16), 6(18)]. The dorsal sagittal sinus and ventral cavernous sinus of dura mater were detected [Fig. 6(11), (12)]. The pons, medulla oblongata [Fig. 8(9), (11)], cerebellar vermis and cerebellar hemispheres were identified [Fig. 8(6), (7)]. The cerebrospinal fluid appeared black on CT images and could be visualized
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in the ventricular system and the subarachnoid spaces. Differentiation between the white and gray matter of the brain was not evident. The features of the cerebrum and cerebellum were not well visualized.
Discussion In the present study, CT, sagittal and cross sectional images revealed the bone and soft tissue of the head, nasal cavity, paranasal sinuses, orbital cavity, oral cavity, pharyngeal cavity, the guttural pouch, cranial cavity and temporomandibular joint of the donkey head cavity. We used the cheek teeth neck, surrounding bones and muscles as landmarks. The nasal cavity and paranasal sinuses were distinguished by good image contrast in CT because of the
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Fig. 9 a Lateral CT scan and b sagittal section of cadaver head. 1 Dorsal conchal sinus, 2 ventral conchal sinus, 3 middle conchal sinus, 4 ethmoidal sinus, 5 rostral maxillary sinus, 6 caudal maxillary sinus, 7 maxillary septum, 8 frontal bone, 9 frontal sinus, 10 nasal bone, 11 parietal bone, 12 straight fold, 13 alar fold, 14 basal fold, 15 sphenopalatine sinus, 16 frontal lobe, 17 parietal lobe, 18 thalamus, 19 pituitary gland, 20 cerebellum, 21 pons, 22 medulla oblongata, 23 pharynx, 24 oral cavity, 25 tongue, 26 hard palate, 27 guttural pouch, 28 soft palate, 29 larynx
adjacent air and bone (Probst et al. 2005). CT is an excellent imaging modality for the dense bone structures of the petrous temporal bones and temporomandibular joint, and proved quite useful for determining cranioencephalic topography, mainly from the ventricular system (Morrow et al. 2000; Arencibia et al. 2005). All structures of the nasal cavity and sinuses were clearly identified. We found three conchal sinuses: the dorsal conchal sinus occupying the dorsal nasal concha and the middle conchal sinus occupied the middle concha, while the ventral conchal sinus was occupying the ventral nasal concha. This is agreement with Probst et al. (2005). However, the ventral conchal sinus was absent because of the presence of spiral lamellae within the dorsal and ventral parts of ventral nasal concha, as mentioned by Alsafy et al. (2012) in buffalo. Our study recorded that the nasal septum reaches the floor of nasal cavity and connects with the channel formed by the vomer with the presence of vomeronasal organ on each
side of the nasal septum. This seems a peculiar feature in buffalo as compared to cattle where the septum fails caudally to reach the floor of nasal cavity, forming a single median channel that continues the paired nasal passages into the nasopharynx (Alsafy et al. 2012). The paranasal sinuses recorded in studied donkey heads were the frontal, maxillary and sphenopalatine sinuses, i.e. different than that recorded in cattle and buffalo, which have frontal, maxillary, sphenoidal, ethmoidal, lacrimal and palatine sinuses (Nickel et al. 1986; Budras et al. 2003; Alsafy et al. 2012). The frontal sinus was triangular in shape and united rostrally with the dorsal conchal sinus forming the conchofrontal sinus, similar to the case described by Nickel et al. (1986) in horse. While subdivided into compartments as reported in cattle and buffalo, these also have nuchal and cornual diverticulum extends into the frontal sinus (Nickel et al. 1986; Budras et al. 2003; Alsafy et al. 2012). In our study, the maxillary sinus had an incomplete bony septum
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that varied in height. Omar et al. (1985) reported its absence in the same animal species (donkey). On the contrary, the septum is complete in horse (Budras et al. 2001; Probst et al. 2005). The anatomical structures of the oral cavity determined by CT and cross sectional images are very similar to those denoted by Solano and Brawer (2004), especially the normal and abnormal structures of teeth. All the anatomical structures related to the guttural pouches resemble those in the horse. One of the most obvious differences is in the shape and extent of the pharyngeal recess, which in the donkey is remarkable for its large size and has a caudal elongation between the left and right guttural pouches. The pharyngeal recess was deeper and larger in donkey. This finding agrees with that of Alsafy et al. (2008). Our CT and cross sectional images recognized the eye parts and surrounding periorbital (Hathcock et al. 1995). The articular disc, articular surface and joint capsule of temporomandibular joint that appeared in our CT and cross sectional images were very similar to those described by Arencibia et al. (2012). CT, sagittal and cross sectional images of the cranial cavity were described accurately in brain parts. Detailed anatomy of the central nervous system of the head were easily distinguishable by their highly radioopaque image compared to adjacent or surrounding structures such as the paranasal sinuses, guttural pouch, and muscles of the head (Hathcock et al. 1995; Arencibia et al. 2000, 2005). Conflict of interest
None.
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ORIGINAL ARTICLE
Computed tomography and sectional anatomy of the head cavities in donkey (Equus asinus) S. A. A. El-Gendy • M. A. M. Alsafy A. A. El Sharaby
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Received: 19 April 2013 / Accepted: 1 October 2013 / Published online: 16 October 2013 Ó Japanese Association of Anatomists 2013
Abstract The purpose of this study was to describe the computed tomographic (CT) anatomy of normal donkey head cavities to be used as a basis for interpretation of CT images of donkey. Six adult donkeys’ heads of undetermined sex were used in this study. The donkey heads were divided into three regions—nasal, orbital, and cranial—to show the morphology of the following cavities: nasal cavity, paranasal sinuses, orbital cavity, oral cavity, pharyngeal cavity, especially the guttural pouch, cranial cavity and temporomandibular joint. The donkey head had six pairs of sinuses: three paranasal (the frontal, maxillary and sphenopalatine sinuses) and three nasal (dorsal, middle and ventral conchal) sinuses. The maxillary sinus was subdivided into rostral and caudal compartments by a thin incomplete bony septum that was identified and labeled according to cheek teeth landmarks. The topographic description and relationship between the nasal, oral, orbital, cranial, temporomandibular joint, pharyngeal cavities and paranasal sinuses were demonstrated. The articular disc, articular surface and joint capsule of the temporomandibular joint were indicated easily in our CT and cross sectional images. Keywords Computed tomography Sectional anatomy Head cavities Donkey Head Nasal cavity S. A. A. El-Gendy (&) M. A. M. Alsafy Department of Anatomy and Embryology, Faculty of Veterinary Medicine, Alexandria University, PO Box 22785, Edfina, Behera, Egypt e-mail: [email protected] A. A. El Sharaby Department of Anatomy and Embryology, Faculty of Veterinary Medicine, Damanhour University, Damanhour, Egypt
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Introduction Donkeys are used in a variety of activities with social and/ or economic benefits. Small holder farmers use donkeys to cultivate their land, coping with labour shortages and loss of other livestock due to drought. By using donkeys in agriculture and transport, farmers have increased their productive potential and expanded their marketing options. Donkeys have also provided employment for many people who hire out donkeys or use donkey carts on a commercial basis for a transport service (Marshall and Zahra 2000). Donkeys belong to the family Equidae and, as such, are similar to equines in many ways. However, there are several significant features specific to the donkey that practitioners should be aware of when trying to explore and treat respiratory disease. These include differences in anatomy, physiology, pharmacokinetics, disease incidence and morbidity with certain infectious diseases. Worldwide, there are an estimated 44 million donkeys, of which 96 % are found in developing countries contributing significantly to the rural economy. Thus, there is a need for equine practitioners to treat donkey patients in an informed and sensitive manner (Starkey 1997; Thiemann and Bell 2001). Computed tomography (CT) of the equine head is an imaging technique that is becoming more and more commonly performed (Solano and Brawer 2004). The major advantage of CT over conventional radiographs is the lack of superimposition and improved demonstration of individual parts of the skull. In addition, the regions of interest have high inherent radiographic contrast and CT provides clear, unobstructed images (Gibbs 1999). CT is best suited to anatomical studies of varied tissue density parts such as the head in large animals (Morrow et al. 2000; Alsafy et al. 2012). The main advantage of CT of the equine head is the ability to produce detailed cross-sectional images of the
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Fig. 1 a, b Computed tomography (CT) scans and c, d cross-sectional images of the rostral nasal region at the level interalveolar space and first premolar teeth. 1 Nasal bone, 2 nasal diverticulum (false nostrils), 3 straight fold of dorsal nasal concha, 4 alar fold of ventral nasal concha, 5 basal fold of ventral nasal concha, 6 dorsal nasal concha, 7 ventral nasal concha (contain venous plexus), 8 dorsal nasal meatus, 9 ventral nasal meatus, 10 middle nasal meatus, 11 nasal septum, 12 palatine process of maxillary bone, 13 buccal vestibule, 14 oral cavity proper, 15 vomeronasal organ, 16 hard palate, 17 buccinator muscle, 18 tongue apex, 19 rostral aspect of the ramus of the mandible, 20 rostral margin of the 1st pre molar teeth, 21 lingual frenulum, 22 interalveolar space
nasal cavity, paranasal sinuses, and brain case without superimposition of other anatomical structures (Solano and Brawer 2004; Probst et al. 2005). Thus, the aim of our study was to provide an atlas of normal cross-sectional anatomy of the structures of the donkey head using CT images and transverse gross anatomic sections and to familiarise the reader with the complex anatomical relationships of the area by providing an atlas of CT anatomy of equine head cavities.
Materials and methods Six heads of adult donkey’s undetermined sex were collected from the local dissecting hall in Faculty of Veterinary Medicine in Edfina, Behera Governate, Egypt. This
study followed the guidelines for the care and use of laboratory animals and the animal welfare and Ethics Committee of the Faculty of Veterinary Medicine, Alexandria University according the Egyptian’s laws, approved it. Computed tomography scans Two donkeys’ heads were used for CT scans after being bled. The heads were removed from the level of the third cervical vertebra and CT examination was performed on serially sectioned heads using a CT scanner (CT-W45010A, Hitachi, Tokyo, Japan). The scanned images were taken as 1.5-cm-thick images of the head from the external occipital protuberance caudally to the level of the canine teeth rostrally (scanning conditions: 130 kV, 100 MA).
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Fig. 2 a, b CT scans and c, d cross-sectional images of the middle nasal region at the level of the second and third premolar teeth. 1 Nasal bone, 2 maxillary bone, 3 dorsal nasal concha, 4 ventral nasal concha, 5 dorsal nasal meatus, 6 middle nasal meatus, 7 ventral nasal meatus, 8 nasal septum with vomer bone, 9 common nasal meatus, 10 infraorbital canal (foramen), 11 rostral maxillary sinus, 12 palatine process of maxillary bone, 13 buccal vestibule, 14 oral cavity proper, 15 buccinator muscle, 16 vomeronasal organ, 17 hard palate, 18 tongue, 19 lacrimal canal and nasolacrimal duct, 20 second premolar teeth, 21 third premolar teeth, 22 levator labii maxillaris muscle, 23 geniohyoideus muscle, 24 vomer bone, 25 lingual artery
Sectional anatomy Four frozen donkey’s heads (two fresh and two formalin fixed) were used to determine sectional anatomy. Three heads were serially cut into cross sections using a table band saw; the cross sections were approximately 1.5 cm apart, and extended from the external occipital protuberance caudally to the level of the interalveolar space rostrally. The slices were numbered and gently cleaned of debris with water and light brushing and were photographed immediately with the caudal surface of each slice facing the camera. One head was cut sagittally. We used the neck of the premolar and molar teeth and bony parts as
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landmarks to explore and describe the location and extension of the structures and cavities.
Results The donkey heads under study were divided into three regions—nasal, orbital and cranial—to demonstrate the morphology of following structures: nasal cavity; paranasal sinuses; orbital cavity; oral cavity; pharyngeal cavity, especially the guttural pouch; cranial cavity; and temporomandibular joint. The current study was performed using CT scanning and sectional anatomy.
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Fig. 3 a, b CT scans and c, d cross-sectional images of the caudal nasal region at the level of the first and second molar teeth. 1 Nasal bone, 2 frontal bone, 3 maxillary bone, 4 dorsal nasal concha, 5 ventral nasal conchal sinus, 6 dorsal nasal conchal sinus, 7 frontal sinus, 8 conchofrontal sinus, 9 frontal septum between right and left frontal sinuses, 10 dorsal nasal meatus, 11 middle nasal meatus, 12 ventral nasal meatus, 13 nasal septum, 14 common nasal meatus, 15 infraorbital canal, 16 rostral maxillary sinus, 17 trabeculae in maxillary sinus, 18 caudal maxillary sinus, 19 maxillary septum, 20 conchomaxillary opening, 21 nasomaxillary opening, 22 lacrimal canal and nasolacrimal duct, 23 palatine canal, 24 facial crest, 25 vomer bone, 26 hard palate, 27 soft palate, 28 bulla of the ventral nasal conchal sinus, 29 buccinator muscle, 30 masseter muscle, 31 tongue, 32 first molar teeth, 33 second molar teeth
The nasal cavity CT and cross sectional images of the nasal cavity accurately described the nasal concha, conchal sinuses, nasal meatuses, paranasal sinuses, vomeronasal organ and nasal septum. The donkeys’ heads had six pairs of sinuses: three nasal; dorsal, middle, and ventral conchal sinuses and three paranasal; and frontal, maxillary, and sphenopalatine sinuses. The relationship between various air cavities was easily visualized. Dorsal nasal concha and sinus The dorsal nasal concha was continued rostrally by the straight fold [Fig. 1(3)]. Scrolls were present in the rostral
portion of the dorsal nasal concha, surrounding recesses of the nasal cavity and having medium-density thick walls and a spiral form [Figs. 2(3), 3(4)]. The caudal half of the dorsal nasal concha contained the dorsal conchal sinus with its low density thin wall. It extended from the level of the caudal third of the first molar to third molar teeth (Fig. 3(6)]. Middle nasal concha and sinus The middle nasal concha was situated among the ethmoidal labyrinth and dorsal nasal sinus and appeared oval in CT [Fig. 4(11)]. It contained the middle conchal sinus, which connected with the caudal maxillary sinus by a small oval opening measuring 0.4 cm in length and 0.2 cm in width.
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Fig. 4 a, b CT scans and c, d cross-sectional images of the rostral orbital region at the level of the third molar teeth. 1 Frontal bone, 2 zygomatic process of frontal bone, 3 temporal process of zygomatic bone, 4 eye (choroid and retina), 5 lens, 6 dorsal conchal sinus, 7 ethmoid labyrinth, 8 conchofrontal sinus, 9 periorbital fat and ocular muscles, 10 frontomaxillary opening, 11 middle conchal sinus, 12 vomer bone, 13 frontal septum between right and left frontal sinus, 14 olfactory bulb, 15 palatine bone, 16 masseter muscle, 17 medial pterygoid muscle, 18 soft palate, 19 caudal maxillary sinus, 20 stylohyoid bone, 21 oropharynx, 22 basihyoid bone, 23 omohyoid and sternohyoid muscles, 24 nasopharynx, 25 dorsal nasal meatus, 26 infraorbital canal, 27 sphenopalatine vessels, 28 sphenopalatine opening, 29 sphenopalatine sinus, 30 root of the tongue, 31 third maxillary molar teeth, 32 optic nerve, 33 mandibular foramen, 34 lacrimal gland
Ventral nasal concha and sinus
Nasal meatuses
The ventral nasal concha continued rostrally by the alar and basal folds [Fig. 1(4), (5)]. The rostral portion of the ventral nasal concha formed scrolls surrounding recesses. The caudal portion of the ventral nasal concha contained the ventral conchal sinus [Fig. 3(5)], which extended from the level of the first molar to the rostral part of third molar teeth. The ventral conchal sinuses drained into the rostral aspect of the rostral maxillary sinus via a narrow conchomaxillary opening [Fig. 3(20)]. The caudal portion of the ventral conchal sinus formed the bulla of the ventral nasal concha [Fig. 3(28)].
The dorsal and middle nasal meatuses appeared narrow [Fig. 1(8)–(10)]. The middle meatus contained a slit-like nasomaxillary opening [Fig. 3(21)], which was the narrowest communicating opening; it located at the level from the middle of the first molar tooth to the rostral of the third molar tooth. The opening measured 3.5–4 cm in length and 0.1–0.2 cm in width. The nasolacrimal duct was situated in the lateral aspect of the middle nasal meatus and covered by mucous membrane [Fig. 3(22)]. The ventral nasal meatus was the largest one.
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Fig. 5 a CT scan and b crosssectional image at the level of the caudal orbital region. 1 Retro-orbital fat, 2 frontal sinus, 3 sphenoid bone, 4 frontal bone, 5 zygomatic process of temporal bone, 6 coronoid process of the mandible, 7 frontal lobe of brain, 8 sphenopalatine sinus, 9 lateral pterygoid muscle, 10 medial pterygoid muscle, 11 pharyngeal recess, 12 nasopharynx, 13 auditory tube, 14 transverse facial artery and vein, 15 maxillary vein, 16 optic tract, 17 soft palate, 18 masseter muscle, 19 stylohyoid bone, 20 thyrohyoid bone, 21 facial vein, 22 mandibular salivary gland, 23 omohyoid and sternohyoid muscles, 24 ramus of the mandible
Paranasal sinuses
second molar tooth. It measured about 4.4–5 cm in length and 0.3–0.4 cm in width.
Maxillary sinus Frontal sinus The maxillary sinus appeared with low density and has high density structures; infraorbital canal, maxillary septum and bony spicules [Fig. 3(15), (17), (19)]. These were divided into rostral and caudal compartments by a thin incomplete bony septum [Figs. 3(19), 9(7)]; the dorsal part of the septum was formed by the bulla of the ventral conchal sinus [Fig. 3(28)]. This septum angled obliquely caudally and its rostral aspect was varied in position; it usually crossed the roots of the second and third molar teeth, approximately 4–5 cm caudal to the rostral end of the facial crest. In the present study, most specimens had a low septum of about 1.5 cm high. The depth of the sinus was about 4–5.5 cm and contained bony spicules [Fig. 3(17)]. The caudal maxillary sinus was partially divided into medial and lateral compartments by the infraorbital canal [Fig. 3(15), (18)]. Those two parts communicated freely over the canal. Only the root of the third maxillary molar tooth was embedded in the caudal maxillary sinus. Both rostral and caudal maxillary sinuses were connected with the middle nasal meatus via a slit-like nasomaxillary opening [Fig. 3(21)]. The rostral maxillary sinus appeared smaller than the capacious caudal maxillary sinus. It communicated with the ventral conchal sinus via the wide conchomaxillary opening [Fig. 3(20)] dorsal to the infraorbital canal [Fig. 3(15)]. The opening located at the level of the rostral part of the first molar tooth until the caudal part of the
The frontal sinus appeared as air-filled spaces formed by the evagination of the frontal bones into the nasal cavity [Figs. 3(7), 5(2)]. The sinus continued rostrally with the dorsal conchal sinus forming the conchofrontal sinus [Fig. 3(8)], which communicated directly with the caudal maxillary sinus by a large, oval or bean-shaped frontomaxillary opening. This opening was about 4–5 cm in length and 2.5–3.5 cm in width [Fig. 4(10)] and located in a dorsal plane slightly caudal to medial canthus of the eye. The frontomaxillary opening was at the level of the caudal third of the second molar tooth and extended 2–3 cm caudal to the last molar tooth on the lateral floor of the conchofrontal sinus. The left and right frontal sinuses were completely separated by a thick midline bony septum [Fig. 3(9)]. Sphenopalatine sinuses The sphenopalatine sinuses were excavated in the palatine and sphenoid bones ventromedial to the orbit and ventral to the brain [Figs. 4(29); 5(8)]. The septum dividing the left and right sphenoidal sinuses was found in all cases; however, it was not frequently in the midline [Fig. 6(15)]. The sphenoidal and palatine sinuses communicated with each other. The dorsal and lateral walls of the sphenopalatine sinus were thin, and communication with the caudal maxillary sinus was via the sphenopalatinal opening, which
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Fig. 6 a, b CT scans and c, d cross-sectional images of the rostral cranial region at the level of the temporomandibular joint. 1 Parietal bone, 2 zygomatic process of temporal bone, 3 body of basisphenoid bone, 4 temporal muscle, 5 mandibular fossa, 6 coronoid process of the mandible, 7 temporomandibular joint with articular disc, 8 condyloid process of mandible, 9 temporal lobe of brain, 10 parietal lobe of brain, 11 dorsal sagittal sinus of dura mater, 12 ventral cavernous sinus of dura mater and maxillary, 13 sphenopalatine sinus, 14 alar canal, 15 sphenopalatine septum, 16 pharyngeal recess, 17 auditory tube, 18 optic nerve, 19 masseter muscle, 20 medial pterygoid muscle, 21 stylohyoid bone, 22 lateral pterygoid muscle, 23 left guttural pouch, 24 right guttural pouch, 25 septum of guttural pouch, 26 thyrohyoid bone, 27 larynx, 28 transverse facial artery and vein, 29 maxillary vein, 30 lateral ventricle, 31 corpus callosum, 32 third ventricle, 33 thalamus, 34 hypothalamus, 35 hippocampus, 36 mandibular salivary gland, 37 omohyoid and sternohyoid muscle
was the most caudal opening of the maxillary sinus; the opening appeared sagittally oblique and was located between the caudal origin of the infraorbital canal and the pterygopalatine fossa caudal to the roots of the last molar tooth. It measured 1.5–2 cm in length and 0.8–1 cm in width [Fig. 4(28)]. Both sphenopalatine sinuses appeared as rectangular.
Nasal septum Most of the nasal septum was cartilage, the dorsal border of which was T-shaped and connected with nasal and frontal bones. Its ventral border connected with the channel formed by the vomer [Fig. 4(8), (24)]. Orbital cavity
Vomeronasal organ The vomeronasal organ appeared as a pair of long ducts on each side of the nasal septum at the ventral meatus, supported by a thin cartilage extending from the incisive duct to the level of the second upper molar tooth [Figs. 2(16), 4(15)].
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CT and cross sectional images recognized most structures of the eye orbit. The lens appeared with moderate density, i.e., it had a homogenous density in CT higher than that of the surrounding eye ball tissue [Fig. 4(5)]. The vitreous body of the eye, anterior chamber of eye, choroid and
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Fig. 7 a CT scan and b crosssectional image at the level of the middle cranial region. 1 Parietal bone, 2 petrosal part of temporal bone, 3 temporal muscle, 4 masseter muscle, 5 stylohyoid bone, 6 thyrohyoid bone, 7 larynx, 8 left guttural pouch, 9 medial compartment of the right guttural pouch, 10 lateral compartment of the right guttural pouch, 11 pharynx, 12 cerebral crura, 13 mesocephalic duct, 14 cerebral cortex (occipital lobe of brain), 15 ventral rectus and longus capitis muscles, 16 parotid salivary gland, 17 mandibular salivary gland
retina, periorbital fat, muscles of the eye, lacrimal gland and optic nerve were identified [Fig. 4(4), (9), (32), (34)]. Differences between density of eye ball layers and surrounding periorbit were recognized [Fig. 4(4), (9)]. Oral cavity The rostral aspect of the oral cavity elucidated the apex of tongue [Fig. 1(18)], lingual frenulum [Fig. 1(20)], hard palate [Fig. 1(16)], interalveolar space [Fig. 1(21)], buccal vestibule [Fig. 1(13)] and oral cavity proper [Fig. 1(14)] in CT and cross section anatomy. In the middle part of the oral cavity, the body of the tongue occupied the plurality of the oral cavity proper, and geniohyoideus muscle, lingual artery and hard palate were identified. The caudal part of the oral cavity illuminated clearly the root of the tongue [Fig. 4(30)], basihyoid bone [Fig. 4(22)], soft palate, [Figs. 3(27), 4(18)] palatine canal [Fig. 3(22)] in CT and cross sectional anatomy. Pharyngeal cavity In serial CT sections and anatomical cross sections of the pharyngeal cavity of the donkey head, the oropharynx [Fig. 4(21)] pharyngeal recess, nasopharynx, auditory tube [Fig. 5(11), (12), (13)], hyoid apparatus and guttural pouches (Figs. 5–9) were clearly recognized. The right and left guttural pouches started to appear as extensions of the auditory tube on both sides of the pharyngeal recess [Fig. 6(17), (23), (24)]. In the more caudal direction, each pouch spreads in basal and lateral directions and was separated at the median part by a thin septum [Fig. 6(25)]. Moreover, at the level of the head of the mandible in this
section, each guttural pouch started to be divided into medial and lateral compartments by the stylohyoid bone. In the more nuchal section, the stylohyoid bone more clearly divided the pouch into two compartments [Fig. 7(9), (10)]. Furthermore, in this section, the thin septum could not be seen because each medial compartment was distant from the center line of the head due to the presence of the ventral rectus and longus capitis muscles [Fig. 7(15)]. In the same section, the lateral compartment of the pouch was completely separated from the medial compartment by the stylohyoid bone [Fig. 7(5)]. As the CT sections approached the occipital condyle, the lateral compartments disappeared and the medial compartments gradually became smaller toward the base of the skull [Fig. 8(10)]. Temporomandibular joint The squamous part of the temporal bone, mandibular fossa, coronoid process of the mandible, temporomandibular joint with articular disc and condyloid process of mandible were easily identifiable because of the high CT density in cortical bone and the intermediate CT density in their medullary cavities. The articular disc, articular surface and joint capsule produced low to intermediate attenuation [Fig. 6(5)–(8)]. It was not possible to identify the ligaments, blood vessels, and nerves in CT images. Cranial cavity From the collection of CT, sagittal and cross section images of the cranial cavity, the brain parts and sinuses surrounding were accurately described. The brain had a similar homogenous appearance that was slightly less
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Fig. 8 a, b CT scans and c, d cross-sectional image of the caudal cranial region at the level of the occipital condyle. 1 Lateral part of occipital bone paracondylar process, 2 parietal bone, 3 basilar part of occipital bone, 4 temporal muscle, 5 transverse sinus, 6 cerebellar vermis, 7 cerebellar hemisphere, 8 fourth ventricle, 9 pons, 10 guttural pouch (caudal part), 11 medulla oblongata, 12 auricular cavity, 13 atlantooccipital joint, 14 occipital condyle, 15 atlantoaxial joint, 16 pena, 17 spinal cord
opaque than the surrounding musculature and bones of the head. In the rostral aspect of the cranial cavity the olfactory bulbs were separated by a bony septum just caudal to the cribriform area [Fig. 4(14)]. The lateral ventricles appeared as regions of low opacity [Fig. 6(30)]. The frontal, parietal, temporal and occipital lobes of the cerebral hemisphere were clearly identified [Figs. 5(7), 6(9), (10)]. The thalamus was clear [Fig. 6(33)] and the pituitary gland was detected ventral to the thalamus [Figs. 6(34), 9(18)]. The optic tract, optic chiasm, and optic nerve were identified under the thalamus [Figs. 5(16), 6(18)]. The dorsal sagittal sinus and ventral cavernous sinus of dura mater were detected [Fig. 6(11), (12)]. The pons, medulla oblongata [Fig. 8(9), (11)], cerebellar vermis and cerebellar hemispheres were identified [Fig. 8(6), (7)]. The cerebrospinal fluid appeared black on CT images and could be visualized
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in the ventricular system and the subarachnoid spaces. Differentiation between the white and gray matter of the brain was not evident. The features of the cerebrum and cerebellum were not well visualized.
Discussion In the present study, CT, sagittal and cross sectional images revealed the bone and soft tissue of the head, nasal cavity, paranasal sinuses, orbital cavity, oral cavity, pharyngeal cavity, the guttural pouch, cranial cavity and temporomandibular joint of the donkey head cavity. We used the cheek teeth neck, surrounding bones and muscles as landmarks. The nasal cavity and paranasal sinuses were distinguished by good image contrast in CT because of the
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Fig. 9 a Lateral CT scan and b sagittal section of cadaver head. 1 Dorsal conchal sinus, 2 ventral conchal sinus, 3 middle conchal sinus, 4 ethmoidal sinus, 5 rostral maxillary sinus, 6 caudal maxillary sinus, 7 maxillary septum, 8 frontal bone, 9 frontal sinus, 10 nasal bone, 11 parietal bone, 12 straight fold, 13 alar fold, 14 basal fold, 15 sphenopalatine sinus, 16 frontal lobe, 17 parietal lobe, 18 thalamus, 19 pituitary gland, 20 cerebellum, 21 pons, 22 medulla oblongata, 23 pharynx, 24 oral cavity, 25 tongue, 26 hard palate, 27 guttural pouch, 28 soft palate, 29 larynx
adjacent air and bone (Probst et al. 2005). CT is an excellent imaging modality for the dense bone structures of the petrous temporal bones and temporomandibular joint, and proved quite useful for determining cranioencephalic topography, mainly from the ventricular system (Morrow et al. 2000; Arencibia et al. 2005). All structures of the nasal cavity and sinuses were clearly identified. We found three conchal sinuses: the dorsal conchal sinus occupying the dorsal nasal concha and the middle conchal sinus occupied the middle concha, while the ventral conchal sinus was occupying the ventral nasal concha. This is agreement with Probst et al. (2005). However, the ventral conchal sinus was absent because of the presence of spiral lamellae within the dorsal and ventral parts of ventral nasal concha, as mentioned by Alsafy et al. (2012) in buffalo. Our study recorded that the nasal septum reaches the floor of nasal cavity and connects with the channel formed by the vomer with the presence of vomeronasal organ on each
side of the nasal septum. This seems a peculiar feature in buffalo as compared to cattle where the septum fails caudally to reach the floor of nasal cavity, forming a single median channel that continues the paired nasal passages into the nasopharynx (Alsafy et al. 2012). The paranasal sinuses recorded in studied donkey heads were the frontal, maxillary and sphenopalatine sinuses, i.e. different than that recorded in cattle and buffalo, which have frontal, maxillary, sphenoidal, ethmoidal, lacrimal and palatine sinuses (Nickel et al. 1986; Budras et al. 2003; Alsafy et al. 2012). The frontal sinus was triangular in shape and united rostrally with the dorsal conchal sinus forming the conchofrontal sinus, similar to the case described by Nickel et al. (1986) in horse. While subdivided into compartments as reported in cattle and buffalo, these also have nuchal and cornual diverticulum extends into the frontal sinus (Nickel et al. 1986; Budras et al. 2003; Alsafy et al. 2012). In our study, the maxillary sinus had an incomplete bony septum
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that varied in height. Omar et al. (1985) reported its absence in the same animal species (donkey). On the contrary, the septum is complete in horse (Budras et al. 2001; Probst et al. 2005). The anatomical structures of the oral cavity determined by CT and cross sectional images are very similar to those denoted by Solano and Brawer (2004), especially the normal and abnormal structures of teeth. All the anatomical structures related to the guttural pouches resemble those in the horse. One of the most obvious differences is in the shape and extent of the pharyngeal recess, which in the donkey is remarkable for its large size and has a caudal elongation between the left and right guttural pouches. The pharyngeal recess was deeper and larger in donkey. This finding agrees with that of Alsafy et al. (2008). Our CT and cross sectional images recognized the eye parts and surrounding periorbital (Hathcock et al. 1995). The articular disc, articular surface and joint capsule of temporomandibular joint that appeared in our CT and cross sectional images were very similar to those described by Arencibia et al. (2012). CT, sagittal and cross sectional images of the cranial cavity were described accurately in brain parts. Detailed anatomy of the central nervous system of the head were easily distinguishable by their highly radioopaque image compared to adjacent or surrounding structures such as the paranasal sinuses, guttural pouch, and muscles of the head (Hathcock et al. 1995; Arencibia et al. 2000, 2005). Conflict of interest
None.
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