Light and electron microscopic examination of serial transverse sections of interalveolar septa of hamster lung have demonstrated a virtually continuous connective tissue sheet of variable thickness in the interalveolar septum. This central sheet, like connective tissue elsewhere, is composed of ground substance in which are immersed cells, collagen and elastin. A capillary network lies on each surface of this sheet. The capillary basement membrane is continuous with the central sheet but in contrast to it is thin, uniform and devoid of cells, collagen or elastin. Capillaries on one surface frequently anastomose directly through the septum with capillaries on the opposite surface.The central sheet is shown to be virtually continuous despite frequent thinning. Whenever cells, collagen or elastin occur in the interalveolar septum, it is always in the central sheet. The efficiency of this arrangement in combining optimum gas conductance with adequate mechanical support is pointed out.The central sheet is also continuous with the perivascular connective tissue cuff and thus may serve as an important route of extracellular fluid transport to the perivascular lymphatics.
An electron microscopical investigation was made of neuronal terminals in operatively removed human duodenum and jejunum. No intraepithelial neur o a d elements were found. The lamina propria mucosae, submucosa and muscular layer possessed, in addition to large bundles of unmyelinated nerve fibers, small ones consisting of three or four s o n s wrapped by infoldings of one Schwann cell. Some of these axons were light; others contained mitochondria and clear vesicles measuring 200-500 A across. Still other axons had dense-cored vesicles with a diameter -700 A.The plasma membranes of vesiculated axons were not thickened and only in part invested by the Schwann cell, but were covered by a basement membrane. Such profiles were interpreted as nerve terminals, and were separated from fibers of the muscularis mucosae, bases of epithelial cells and submucous capillaries by interspaces measuring 5,0004,800 A. The gap between neuronal terminals and smooth muscle in the muscular wall was smaller (900A, more often I,SOCr3,00OA). The myenteric plexus contained nerve bundles consisting of the usual axons and of preterminals; some of the latter contained small clear vesicles, others predominantly larger granulated vesicles, and stilI others a mixture of both types of vesicles. The similarities and differences of neuronal terminals occurring in animals and in man were pointed out. The significance of the findings of this study was discussed in the light of current concepts of the physiology of autonomic nerve transmission.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.