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Respiratory Structures of the Head
Nares
Nares
The nares are orifices which allow the passage of air into the body. They are situated on the nasolabial planum.
https://www.istockphoto.com/photos/bull-nostrils
Nasal Cavity
Nasal Cavity
Within the nasal cavity of cattle are the dorsal, ventral, and ethmoid conchae. These conchae warm and humidify inspired air.
https://open.lib.umn.edu/largeanimalsurgery/chapter/nasal-discharge/
Pharynx
Pharynx
Warms and humidifies air similar to conchae. Split into 4) nasopharynx, 6) oropharynx, and 8) laryngopharynx
https://www.sciencedirect.com/science/article/pii/S0021997522000871
Laryngeal Cartilage
Source: University of Nottingham
From cranial to caudal:
The Hyoid Apparatus is a point of attachment for the tongue, larynx, and other surrounding organs and cartilages. Part of it can be seen articulating with the thyroid cartilage
The Epiglottis is a pliable structure which covers the trachea during deglutition
The Thyroid Cartilage is a protective cartilage named for its proximity to the thyroid gland
The Arytenoid Cartilage is the dorsal counterpart to the thyroid cartilage. It is primarily responsible for phonation in cattle. It contains the Vestibule, the space immediately cranial to the Glottis, or the space between the vocal ligaments.
The Cricoid Cartilage forms the base of the laryngeal cartilage.
Conduction of Air
https://www.redbubble.com/i/art-print/Cross-section-of-trachea-by-daisykelly1/129739600.1G4ZT
Trachea
Trachea
The trachea consists of many cartilaginous Tracheal Rings, which are held together with fibrous tissue running cranially to caudally, called Annular Ligaments. The tracheal rings are horseshoe-shaped, and can be constricted in order to expel air forcefully, such as for phonation, coughing, or sneezing. The smooth muscle responsible for this is called the Trachealis Muscle.
https://veteriankey.com/trachea-and-bronchi/
Conducting Zones
Conducting Zones
The caudal trachea splits when it reaches the thoracic cavity. This first junction is called the Carina. The result of this split is the Principal Bronchi, with one such bronchus for each lung. Further separations of the bronchi are what distinguish the lung lobes from one another, as the lobes are determined by the presence of secondary bronchi. These continue to split into tertiary bronchi, bronchioles, and alveolar ducts and sacs.
Anatomy of the Lungs
Anatomy and Physiology of Farm Animals, 8th edition. Fails, Magee
Lobe Organization
Lobe Organization
The two lungs of cattle are divided into 6 lobes in total, two on the left side of the body and two on the right:
Left Cranial Lobe
Left Caudal/Diaphragmatic Lobe
Right Cranial Lobe
Right Middle Lobe
Right Accessory Lobe
Right Caudal Lobe
Pleura
Pleura
The lungs are surrounded by two fluid-filled sacs called the pleura. These sacs prevent any damage to the lungs due to friction with the thoracic cavity. The side of the sac closest to the lung is called the Visceral Pleura and the outside membrane closer to the ribcage is called the Parietal Pleura.
Musculature of Respiration
https://veteriankey.com/thoracic-wall/
Intercostal Muscles
Intercostal Muscles
This image shows the external and internal intercostal muscles between the third and fourth rib.
Internal Intercostal run ventral and cranial to dorsal and caudal. Aid in expiration of air.
External Intercostal run dorsal and cranial to ventral and caudal. Aid in inspiration of air.
https://www.ncbi.nlm.nih.gov/books/NBK470191/figure/article-20465.image.f1/?report=objectonly
Diaphragm
Diaphragm
The Diaphragm is the muscle primarily responsible for respiration. Its structure resembles a dome which arches over the contents of the abdomen. Contractions of the diaphragm flatten it, drawing air into the lungs due to negative pressure - inspiration. Relaxation of this muscle results in expiration. There are three apertures which allow food and blood to pass between the thoracic and abdominal cavities. These apertures are named the Esophageal Hiatus, Aortic Hiatus, and the Vena Caval Foramen after the names of the structures which travel through them.
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