Military roentgenology / War Department.

Date:
[1944]
Catalogue details

Licence: Public Domain Mark

Credit: Military roentgenology / War Department. Source: Wellcome Collection.

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    195. PANCREAS. a. It is an elongated organ shaped like a pistol with the muzzle pomting toward the hilum of the spleen. It is composed of a head, neck, body, and tail. It occupies a position beneath the stomach. It furnishes pancreatic juice which is secreted by one or two ducts (Wirsung and Santorini). b. Function of pancreas: (1) Produces a pancreatic secretion which is capable of splitting all three classes of foodstuffs, that is, carbohydrates, fats, and proteins. (2) Produces a hormone, insulin, which is secreted into the blood and acts to convert blood sugar into glycogen. SECTION VI. RESPIRATORY SYSTEM 196. GENERAL. a. Respiration (breathing) is a process common to all forms of animal life. It consists of supplying oxygen to the cells of the body and relieving them of the carbon dioxide formed during the burning of foods. b. Anatomically, the respiratory system Is com- posed of: the nose, paranasal air sinuses, mouth, pharynx, larynx, trachea, bronchi, and lungs. 197. NOSE. a. It is the organ of smell. It is composed of an outer or external portion and an internal por- tion. The framework of the external nose is composed of the nasal bone and a greater amount of cartilage. b. The nose has a dual function: (1) Olfactory function—which is accomplished by the fine distribution of the branches of the first cranial nerve which pass through the foramina of the cribriform plate of the ethmoid and are distributed to the upper portion of the nasal septum. (2) Respiratory function—which is carried out by means of a mucous membrane, richly supplied with blood, serving thereby to warm and moisten the inspired air. In this region also there are located many fine hairs called “cilia.”” When they are moist, they catch dust particles in the mhaled air and thus serve as filters. 198. PARANASAL SINUSES. a. They are located in the skull and vary in form and size in different mdividuals. The walls of each sinus are covered with mucous membrane from which cilia extend. These include the— (1) Frontal air-smuses—two in number. They are situated behind the superciliary arches. By means of the frontonasal duct, they drain into the middle meatus of the nose. (2) Ethmoidal air-sinuses—which consist of many thin-walled cavities, honeycomb in structure; they are frequently referred to as air-cells. They lie in the upper portion of the nasal cavity and are sepa- rated from the orbit by the thin plate of the ethmoid. (3) Sphenoidal air-sinuses—two in number, lo- 130 cated behind the nasal cavities and situated within the body of the sphenoid bone beneath the sella turcica. They drain into the posterior portion of the middle nasal meatus. (4) Maxillary air-sinuses—referred to as the antrum of Highmore and are located within the body of the maxillary bones. They, too, drain into the middle meatus. The roots of the upper teeth extend up into the floor of these sinuses. b. Function of the paranasal sinuses includes: regulation of temperature and moisture of the inspired air, filtering foreign particles, acting as resonance chambers, affecting voice tone and they lighten the weight of the skull. - 199. LARYNX. It is the organ of voice and is situated in the upper anterior part of the neck above the trachea. It is composed of nine cartilages; thyroid, cricoid, epiglottis, two arytenoids, two cornicu- late, and two cuneiform. With the onset of puberty, the cartilages begin to ossify; as age advances, they may be completely changed to bone. 200. TRACHEA. It is a tube (the wind-pipe) which carries the air between the larynx and the bronchi. It is about 5 mches Jong and lies partly in the neck, partly in the thorax. It begins where the larynx ends. Cartilaginous rings serve for support of its walls. 201. BRONCHI. They are the two tubes extending beyond the trachea. Their structure is identical with that of the trachea. The primary bronchi divide into secondary bronchi and with further divisions they become smaller and smaller, eventually becoming bronchioles. The bronchioles divide into the terminal bronchioles within the lungs and then divide further into atria. Each of these atria then communicate with air sacs into which the alveoli open. It is here that the exchange of gases takes place. 202. LUNGS. They are composed of two pyramidal, spongy lobes adapted to the function of oxygenating the blood. The lungs are covered with a membrane known as the visceral pleura. There is a second layer of pleura adjacent to the thoracic wall—the parietal pleura. Between the layers of parietal and visceral pleura is the pleura cavity which normally contains a small amount of serous fluid. The pleural cavity is part of the thoracic cavity. The lungs, heart, and associated structures lie in the thoracic cavity. The surfaces of the lungs are the diaphragmatic (base), costal (adjoming the ribs) and mediastinal (medial aspects). The hilum of the lung is the area through which the essential structures enter the lung. The apex of the lung is the rounded portion extending up toward the neck. The right lung contains three lobes, superior, middle, and inferior partially divided by two fissures. The left lung usually contains only two lobes, inferior and supertor.