Respiratory System

Head and Cervical Regions:

The tongue is a very vital organ of the mouth for chewing and swallowing food. It has papillae on the surface that help give it it's rough texture. Cattle have filiform, conical, fungiform, and vallate papillae, the fungiform and vallate having the taste buds. Conical papillae are unique to ruminants as well.

The pharynx is the passageway that leads from the mouth and nose to the esophagus and larynx. The structure allows swallowed foods and liquids to go to the esophagus and air to go to and from the trachea during respiration.

The hyoid apparatus is the bone that is linked to movement in the tongue and the styloid process of the the temporal bone. It suspends the tongue and larynx and pivots to pull the cartilage of the larynx, allowing the cartilage to close. It consists of the stylohyoid, thyrohyoid, certatohyoid, and basihyoid.

The epiglottis is one of the cartilages of the larynx that closes the passage to the trachea so that food does not enter the wind pipe. Any stimulus that the larynx receives would cause this to close. The glottis is part of the larynx that consists of the vocal cords and the opening between them. It affects the pitch of sound that is released by the expansion and contraction.

The four cartilages of the larynx includes the epiglottic cartilage, thyroid cartilage, arytenoid cartilage, and cricoid cartilage. The Arytenoid and Thyroid cartilages sit on top of each other, with the vocal cord between them. Any movement between the muscles that pulls these two cartilages would change the tension of the vocal folds and change the pitch of the sound that's created. These are all hyaline cartilages and help support the vocal cords and keep food from entering the trachea and lungs.

The trachea is the tubular portion of the respiratory system after the larynx, which leads air into the lungs, made up of pseudostratified columnar epithelium with cilia. This structure is made up of tracheal rings, which support the trachea because it would be hard for it to re-inflate if it collapsed. Between the rings is a filamentous connection called the annular ligament. The rings are not complete, but make a somewhat u-shape, which is completed by a muscular portion, called the trachealis muscle, which is a smooth muscle. The trachea bifurcates into two bronchi branches at the center arch, called the carina. These two branches are called the principal bronchi, which then divide into secondary bronchi, followed by tertiary bronchi, and then ending in alveolar ducts with alveoli. As the bronchioles become smaller and smaller, they lose cartilaginous support and shift to simple squamous epithelium as they get to the alveoli. This shift is to allow for air exchange, as alveoli are the site of this in the lungs.

Cattle have planum nasolabiale, which is the external part of their nose. The planum, or dark leathery part of the nose extends all of the way to their upper lip. The tissue of the planum is specialized with sweat glands to help keep the nose moist. The vestibule is part of the nasal cavity and it is enclosed by keratinized stratified squamous epithelium. It is supported by cartilage of the nose and is lined with little hairs that help filter dust, sand, and other particles, to prevent them from entering the lungs.

Thoracic Region:

The diaphragm is the skeletal muscle at the base of the chest, dividing the thoracic cavity from the abdominal cavity. A change in volume of the thoracic cavity by the contraction of the diaphragm and intercostal muscles would result in the increase or decrease of pressure in the pleural. If pressure increases, air goes out, and if pressure decreases, air comes in. The esophageal hiatus is the opening in the diaphragm that the esophagus passes through to get to from the thoracic to the abdominal cavity. The aortic hiatus is another opening of the diaphragm that allows passage of the aorta into the retroperitoneal space, which is the space behind the peritoneum. The vena cava foramen is the third opening of the diaphragm that allows the inferior vena cava to pass through.

The lungs are a pair of organs that are filled with air. The alveoli are the functional unit of the lungs, which allow for gas exchange with oxygen and carbon dioxide in the blood. These alveoli create the spongy component of the lungs. There are two pleura of the lungs, which are serous membranes that envelope the lungs. The visceral pleura covers the lungs and the parietal pleura covers the inside of the thorax. Between these two pleura is pericardial fluid to reduce the friction of the layers gliding together.