A manual of anatomy . cal inshape, its apex resting upon the sideof the ala of the thyreoid cartilageand the base extending down to thefifth or sixth tracheal ring. Theisthmus is a narrow band of gland-ular tissue that connects the twolateral lobes across the second, thirdand fourth of the trachea a pyramidal lobe (saidto occur in 40 per cent.) is seenextending upward from the uppermargin of the isthmus. Being firmly attached to the underlyingstructures the thyreoid follows the larynx in its movements. The arteries are the superior and inferior thyreoid arteries. Thesuperior
A manual of anatomy . cal inshape, its apex resting upon the sideof the ala of the thyreoid cartilageand the base extending down to thefifth or sixth tracheal ring. Theisthmus is a narrow band of gland-ular tissue that connects the twolateral lobes across the second, thirdand fourth of the trachea a pyramidal lobe (saidto occur in 40 per cent.) is seenextending upward from the uppermargin of the isthmus. Being firmly attached to the underlyingstructures the thyreoid follows the larynx in its movements. The arteries are the superior and inferior thyreoid arteries. Thesuperior and middle thyreoid veins empty into the internal jugularvein of each side; the inferior thyreoid vein joins its fellow of theopposite side to empty into the left innominate vein. The nerves are derived from the middle and inferior cervicalganglia of the sympathetic system. THE PARATHYREOIDS The parathyreoids are usually four in number, two superior andtwo inferior, although as many as twelve may be present. Each 338. Fig. 249.—Thyreoid gland, ventralview. {From a photograph.) THE CHROMAPHYL SYSTEM 339 weighs from gram to 3 grams and is about l-i inch (6 mm.) inlength and about % inch (3 mm.) in diameter. They are yellowishbrown in color and may be lenticular, or nearly spherical in superior are behind the lateral lobes of the thyreoid body at thelevel of the lower border of the cricoid cartilage. The inferior arevariable in position and may be found behindthe lower part of the lateral lobes and at adistance below. Each is supplied by a branchfrom the inferior thyreoid artery. CHROMAPHYL SYSTEM A number of small organs in the body stainpeculiarly when treated with chromium salts;they secrete adrenalin and are classed underthe chromaphyl system. The adrenals are thelargest and the others comprise the carotidbodies, aortic bodies and paraganglia; all areclosely associated with the sympatheticsystem. THE ADRENALS The adrenals, or suprarenal glands {glandulcEsupra
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecthumananatomy, bookyea
