9. Explain How Specific Muscular Contractions

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1. Why does the trachea lined with pseudostratified ciliated columnar epithelium while the alveoli are lined with simple squamous epithelium? The trachea is lined with pseudostrastified ciliated columnar epithelium because the globlet cells that are there produce sticky mucous to coat the inner lining and catch any debris in inhaled air before it gets to the lungs. The columnar cells have cilia that push mucous away from the lungs. The alveoli are lined with simple squamous epithelium because the very thin epithelium will facilitate the diffusion of oxygen and carbon dioxide.

2. Explain how specific muscular contractions lead to quiet breathing.
The muscles used for quiet breathing are the external intercostal and the diaphragm. Upon inspiration
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The GI tract from the esophagus to the large intestine is composed of four layers. Describe the general histology of these layers.
The four layers of the GI tract are the mucosa, submucosa, muscularispropria, and adventia or serosa.
Mucosa: is the innermost layer and its main function is for absorption and secretion. It is made up of simple columnar epithelium tissue and exocrine cells.
Submucosa: composed of loose connective tissue, with larger blood vessels, lymphatic, nerves and can contain mucous secreting glands
Muscularispropria: composed of two smooth muscles; the inner which is segmentation and the outer which is peristalsis which allow movement of food through the gut
Adventia or serosa: outermost layer composed of loose connective tissue covered by the visceral peritoneum. Contains blood vessels, lymphatics and
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The urinary bladder is a sac-like hollow organ that is used for the storage of urine. Urine slowly fills up the bladder and stretches its elastic walls and can hold 600 to 800 milliliters of urine. The urethra is the tube that transports urine from the bladder to the exterior of the body. There are two muscles in the urethra that control the flow of the urine. They are the internal sphincter which when open results in the sensation of needing to urinate and the external urethral sphincter a skeletal muscle that will allow urine to pass through or delay urination. Regulation of ion /acid balances is the responsibility of the kidneys. The kidney can control the excretion of ions such as potassium, sodium, and calcium into the urine. If the ions are higher than normal the kidneys can increase their excretion out of the body to return them to a normal level. The ph balance is controlled by the kidneys ability to monitor and regulate the levels of hydrogen and bicarbonate ions in the

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