Saffanah Khuder Mahmood, BVMS, MSc, PhD Scientific degree (Dr. Lecturer), Department of Anatomy College of Veterinary Medicine, University of Mosul, Mosul, Iraq https://orcid.org/0000-0003-0687-7762?lang=en https://www.researchgate.net/profile/ Saffanah_Mahmood3 Anatomy | Part 2 | 2nd year 2019 Respiratory System 2=The nasal cavity: Consist of three main parts: a- Nasal vestibule: the first part of the nasal cavity, present inside the nostrils, lined with stratified squamous epithelium. b- Proper nasal cavity: the middle large part of the nasal cavity, filled with nasal conchae. *Nasal conchae: thin scrolls of bone covered with mucous membrane. The dorsal & ventral nasal conchae filled the nasal cavity, which present in all animals, while the middle nasal concha present caudally between the dorsal & ventral nasal conchae (present in ruminants & dog). Anatomy | Respiratory system| Dr. Saffanah Khuder Mahmood Page | 1 *The ethmoidal conchae: present in the caudal part of nasal cavity, contain numerous ethmoturbinate bony scrolls that covered by mucous membrane. *The nasal septum: septum divides the nasal cavity into 2 similar halves. It consist of bony and cartilaginous parts covered with mucous membrane. *The nasal conchae and the nasal septum divides each half of nasal cavity into pathways called the nasal meatuses: 1-Dorsal nasal meatus: between the roof of nasal cavity & dorsal nasal concha. 2-Middle nasal meatus: between the dorsal and the ventral nasal conchae. 3-Ventral nasal meatus: between the ventral nasal concha and the floor of the nasal cavity. Its large meatus lead to the nasopharynx. 4-Common nasal meatus: narrow vertical space between the nasal septum and the nasal conchae from the roof to the floor of the nasal cavity. *Nasopharyngeal meatus: short passage connect ventral nasal meatus with the nasal conchae on each side of nasal cavity. *Choanae (caudal nares): the two openings of the nasopharyngeal meatus into the nasopharynx, separated by vomer bone. *Vomeronasal organ: paired ducts lie in the floor of the nasal cavity on each side of the nasal septum. These ducts supported by thin walled cartilaginous sleeve and vomer bone. These ducts extend caudally from their openings at the incisive duct at the level of canine teeth, till the level of the 3rd or 4th molar teeth (about 15-20 cm length in Anatomy | Respiratory system| Dr. Saffanah Khuder Mahmood Page | 2 horse and ox, and about 2-7 cm length in small species). It has special olfactory and sexual functions. 1 Dorsal nasal concha, 2 Ethmoidal conchae, 3 Ventral nasal concha, 4 Ethmoid bone, 5 Pterygoid bone, 6 Frontal sinus, 7 sphenopalatine sinus Anatomy | Respiratory system| Dr. Saffanah Khuder Mahmood Page | 3 3=The fundus region: lined with olfactory epithelium distinguishing the odors. *Olfactory organ: consist of large area of olfactory mucosa that covering lateral nasal wall and ethmoidal conchae in caudal part of nasal cavity. Olfactory cells are bipolar neurons, their dendrites reach the epithelial surface that have cilia. While their axons combine to form the fascicle of the olfactory nerve (first cranial nerve) which pass through the cribriform plate of ethmoid bone to cranial cavity, where they fuse to form olfactory bulb. The serous olfactory glands moisten the surface to wash away the previously perceived odors. *The wall of the nasal cavity consist of skin externally and bones (maxillary bone, nasal bone, incisive bone, lacrimal bone, zygomatic bone and frontal bone). Anatomy | Respiratory system| Dr. Saffanah Khuder Mahmood Page | 4 *The paranasal sinuses: air filled spaces lined with mucosa that communicate with the nasal cavity. The function of paranasal sinuses are: 1-They offer some thermal and mechanical protection to the orbit, nasal cavity and cranial cavity. 2-Increase the surface area of the skull for the muscular attachments without increasing the weight. 3-Affect the resonant of the voice. *Paranasal sinuses are: In addition to conchal sinuses which are three pairs, the following paranasal sinuses are present: In horse: There are: 1-Frontal sinus. 2-Maxillary sinus (rostral and caudal parts). 3-Sphenopalatine sinus. Anatomy | Respiratory system| Dr. Saffanah Khuder Mahmood Page | 5 In dog: There are: 1-Frontal sinus. 2-Maxillary recess (communicate with nasal cavity). In sheep & goat: 1-Frontal sinus. 2-Maxillary sinus (medial & lateral parts) 3-Sphenoid sinus (small) 4-Palatine sinus. 5-Lacrimal sinus. In ox & buffalo: 1-Frontal sinus: divide into 2 parts: a/ small rostral part . b/ Large caudal part which consist of : 1=Postorbital diverticulum. 2=Nuchal diverticulum. 3=Cornual diverticulum. Anatomy | Respiratory system| Dr. Saffanah Khuder Mahmood Page | 6 2-Maxillary sinus. 3-Sphenoid sinus. 4-Palatine sinus. 5-Lacrimal sinus. Anatomy | Respiratory system| Dr. Saffanah Khuder Mahmood Page | 7 .