A manual of human physiology, including histology and microscopical anatomy, with special reference to the requirements of practical medicine (1885) (14594851197)

Identifier: manualofhumanphy01land (find matches)
Title: A manual of human physiology, including histology and microscopical anatomy, with special reference to the requirements of practical medicine
Year: 1885 (1880s)
Authors: Landois, L. (Leonard), 1837-1902 Stirling, William, 1851-1932
Subjects: Physiology Histology
Publisher: Philadelphia, P. Blakiston, Son, and Company
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library



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tinguished from veins by their thickerwalls, due to the greater development of smooth muscular andelastic tissues — the middle coat (tunica media) of the arteries isspecially thick, while the outer coat (t. adventitia) is relatively thin. (The absence of valves is by nomeans a characteristic feature.) The arteries consist of three coats(Fig. 40). (1.) The Tunica intima,or inner coat, consists of a layer of(a) irregular, long, fusiform nucleatedsquamous cells forming the exces-sively thin transparent endothelium(His, 1866), immediately in contactwith the blood-stream. (Like otherendothelial cells, these cells are heldtogether by a cement substance whichis blackened by the action of silvernitrate.) Outside this lies a very thin, moreor less fibrous, layer - - sub-epithelialhit/cr — in which numerous spindle orbranched protoplasmic cells lie em-bedded within a corresponding systemof plasma canals. Outside this is anelastic lamina (b\ which in the smallestjg a structureless Or fibrous
Text Appearing After Image:
d Fig. 40. Small artery to show the various layers which compose its walls — . . «, endothelium; b, internal elastic elasticmembranc— in artenesof medium lamina; c, circular muscular fibres see it isafcnestrated membrane (Henle), of the middle coat ;</, the connective while in the largest arteries there may tissue outer coat (T. adventitia). , , , i , • i be several layers 01 elastic laminae or fenestrated elastic membrane mixed with connective tissue. (In somearteries the elastic membrane is distinctly fibrous, the fibres beingchiefly arranged longitudinally. It may be stripped off, when it formsa brittle elastic membrane, which has a great tendency to curl up atits margins. In a transverse section of a middle-sized artery itappears as a bright wavy line, but the curves are probably produced STRUCTURE OF ARTERIES. 121 by the partial collapse of the vessel. It forms an important guide tothe pathologist in enabling him to determine which coat of theartery is diseased.) In mid