Data Bases • Custom Term Papers • Free Term Papers • Free Research Papers • Free Essays • Free Book Reports • Plagiarism? Links • Top 100 Term Paper Sites • Top 25 Essay Sites • Top 50 Essay Sites • Search 97,000 Papers @ DirectEssays.com • Search 101,000 Papers @ ExampleEssays.com • Search 90,000 Papers @ MegaEssays.com Free Essays • Term Paper Sites • Chuck III's Free Essays • Free College Essays • TermPaperSites.com • My Term Papers • Get Free Essays • Essay World • Planet Papers	Search Lots of Essays Back to Subjects - Miscellaneous PLANTS PLANTS 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 curved turbinate bones in the sinus area increase the surface area of the passageways, creating eddy currents that , along with hairs, cilia and mucus, help remove dust in the inhaled air Air enters the nasopharynx from the posterior end of the nasal passages, then passes 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 air The diaphragm is a sheet of muscle that seperates the abdonimal cavity from the thoracic cavity. The thoracic cavity is divided into three areas by membranes: The right and left pleural cavities, which surround the lungs, and the pericardial cavity where the The trachea, when it enters the thorax, divides into two bronchi. These bronchi divide into progressively smaller bronchioles. which finally end in micrscopic air sacs called alveoli. In these air sacs, oxygen and carbon dioxide are exchanged between the 25-4 Describe how the diaphragm and rib cage function in moving air into and out Air enters the lungs as a result of the combined effects of the contraction of the diaphragm and 3 sets of muscle: sternocleidomastoid, pectoralis minor and intercostal. When these muscles contract, the volume of the thoracic cavity increases as the rib cage elevates 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 the pressure between the atmosphere and the pleural cavities to equilibrate. When the diaphragm and intercostal muscle relax, the rib cage drops and the diaphragm rises decreasing the volume of the thoracic cavity. 26-3 List the valves of the heart and describ how they operate. The heart consists of four valves the pulmonary semilunar, the tricuspid, the bicuspid and the aortic semilunar. The Four valves within the heart help prevent blood from flowing backward in the heart. The valves open easily in the direction of blood flow, but when blood pushes against the valves in the opposite direction, the valves close. Two of the valves are located between the atria and ventricles, and are known as atrioventricular valves. The right atrioventricular valve is formed from three flaps of tissue and is called the tricuspid valve, while the left atrioventricular valve has two flaps and is called the bicuspid or mitral valve. The other two valves are located between the ventricles and arteries. They are called semilunar valves because they each consist of three half-moon-shaped flaps of tissue. The right semilunar valve, between the right ventricle and pulmonary artery, is also called the pulmonary valve. The left semilunar valve, between the left ventricle and aorta, is also called the aortic valve. 26-4 Describe microcirculation in a capillary network. What controls whether The heart ejects oxygen-rich blood under high pressure out of the heart's main pumping chamber, the left ventricle, through the largest artery, the aorta. Smaller arteries branch off from the aorta, leading to various parts of the body. These smaller arteries in turn branch out into even smaller arteries, called arterioles. Branches of arterioles become progressively smaller in diameter, eventually forming the capillaries. Once blood reaches the capillary level, blood pressure is greatly reduced. Capillaries have extremely thin walls that permit dissolved oxygen and nutrients from the blood to diffuse across to a fluid, known as interstitial fluid, that fills the gaps between the cells of tissues or organs. The dissolved oxygen and nutrients then enter the cells from the interstitial fluid by diffusion across the cell membranes. Meanwhile, carbon dioxide and other wastes leave the cell, diffuse through the interstitial fluid, cross the capillary walls, and enter the blood. In this way, the blood delivers nutrients and removes wastes without leaving the capillary tube. After delivering oxygen to tissues and absorbing wastes, the deoxygenated blood in the capillaries then starts the return trip to the heart. The capillaries merge to form tiny veins, called venules. These veins in turn join together to form progressively larger veins. Ultimately, the veins converge into two large veins: the inferior vena cava, bringing blood from the lower half of the body; and the superior vena cava, bringing blood from the upper half. Both of these two large veins join at the right atrium of the heart. Because the pressure is dissipated in the arterioles and capillaries, blood in veins flows back to the heart at very low pressure, often running uphill when a person is standing. Flow against gravity is made possible by the one-way valves, located several centimeters apart, in the veins. When surrounding muscles contract, for example in the calf or arm, the muscles squeeze blood back toward the heart. If the one-way valves work properly, blood travels only toward the heart and cannot lapse backward. The precapillary sphincter controls whether blood enters a capillary. Bibliography: Word Count: 855
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