Outline the pathway of air from the nostrils to the alveoli in the fetal pig. The nasal passages are separated from each other bt the nasal septum. The curvedturbinate bones in the sinus area increase the surface area of the passageways, creatingeddy currents that , along with hairs, cilia and mucus, help remove dust in the inhaled airand humidify it. Air enters the nasopharynx from the posterior end of the nasal passages, thenpasses into the pharynx, through the glottis, and into the larynx and ultimately the trachea. Air then passes through the voice box and over the vocal cords which vibrate when airpasses over them. The diaphragm is a sheet of muscle that seperates the abdonimal cavity from thethoracic cavity. The thoracic cavity is divided into three areas by membranes: The rightand left pleural cavities, which surround the lungs, and the pericardial cavity where theheart is located.The trachea, when it enters the thorax, divides into two bronchi. These bronchidivide into progressively smaller bronchioles. which finally end in micrscopic air sacscalled alveoli. In these air sacs, oxygen and carbon dioxide are exchanged between theblood and the inhaled air.25-4 Describe how the diaphragm and rib cage function in moving air into and outof a mammal’s lungs.Air enters the lungs as a result of the combined effects of the contraction of thediaphragm and 3 sets of muscle: sternocleidomastoid, pectoralis minor and intercostal. When these muscles contract, the volume of the thoracic cavity increases as the rib cageelevates and the diaphragm depresses, causing the air pressure in the cavity to decrease. Air rushes in through the respiratory passageways and expands the alveoli. this causes thepressure between the atmosphere and the pleural cavities to equilibrate. When thediaphragm and intercostal muscle relax, the rib cage drops and the diaphragm risesdecreasing the volume of the thoracic cavity. 26-3 List the valves of ...
