摘要:

AbstractFusion of atrioventricular endocardial cushions begins during Hamburger‐Hamilton stage 27 and is completed during stage 28 (5 to 6 days incubation age). Connective tissue cells of these cushions are derived from the proliferating endocardial cell layer. The character of the organelles in cells of these cushions changes progressively as the cushions approach, meet and fuse: granular endoplasmic reticulum accumulates; Golgi complexes become extensive, and nuclei develop irregular shapes. These occur first in the connective tissue cells of the cardiac jelly and later in the endocardial cells. Fusion apparently is accomplished by liberation of the endocardial endothelial cells into the cardiac jelly, where, along with pre‐existing connective tissue cells, they become cells of the membranous interventricular septum. Gradually the cells appear to merge into one morphological population and thus become indistinguishable from each other. Both endocardial cells and connective tissue cells exhibit uptake of tritiated thymidine and undergo mitosis before, during and after fusion of the cushions. An outstanding characteristic of these cells is their continuing vitality throughout the entire process of fus

ISSN:0002-9106    

DOI:10.1002/aja.1001330102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY

摘要:

AbstractThe deep layers of the transversospinal back muscles were studied in 25 healthy human subjects. Bipolar fine wire electrodes were inserted bilaterally at the level of the sixth thoracic and the third lumbar spinous processes. Activity was registered simultaneously in sitting and standing, and during movements while in these positions. It was shown that the same muscle group displayed different patterns of activity in the thoracic compared to the lumbar level. Variations in the pattern of activity during forward flexion, extension and axial rotation suggest that the transversospinal muscles adjust the motion between individual vertebrae. The experimental evidence confirms the anatomical hypothesis that the multifidi are stabilizers rather than prime movers of the whole vertebral column.

ISSN:0002-9106    

DOI:10.1002/aja.1001330103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY

摘要:

AbstractThe nasal cavities of 14 deer mice,Peromyscus maniculatus, were examined histologically to determine the variability in surface area of the olfactory epithelium and its correlation with nasal cavity volume, area of non‐olfactory epithelial surface, and body size.Forty‐four per cent of the nasal cavity surface ofP. maniculatusis covered by a non‐olfactory epithelium with an area of 129.8 mm2; the epithelial surface consists of gradations in type from keratinized stratified squamous rostrally to ciliated pseudostratified columnar caudally. An extensive portion of this epithelium is non‐ciliated and devoid of goblet cells. Situated dorsocaudal to the non‐olfactory epithelium is the olfactory epithelial surface measuring 166.8 mm2in area.The areas of total, non‐olfactory and olfactory epithelial surfaces are highly variable in a sample of mice containing two subspecies, both sexes and various ages. Surface area measurements of non‐olfactory and olfactory epithelia are correlated significantly with body length, body weight and volume of the nasal cavity. A relatively constant epithelial area to volume ratio is present in the nasal cavity ofP. maniculatus. It is surmised that a stable ratio of molecules in the air to epithelial area may occur wit

ISSN:0002-9106    

DOI:10.1002/aja.1001330104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY

摘要:

AbstractThe sequence of degeneration in colchicine‐poisoned or in transected peripheral nerve fibers is reported. The results lead us to conclude that the Schwann cell is the predominant agent of axon and myelin destruction. The Schwann cytoplasm burgeons, swells the Schmidt‐Lanterman clefts and the adaxonal layer of cytoplasm, and invades the electron‐dense bands of myelin. The axolemma and adaxonal membranes are eroded and Schwann organelles invade the axoplasm commingling with those of the axon to form a peripheral “reactive zone.” The reactive zone of organelles surrounds a core of compacted neurofilaments which may persist for days. Eventually the entire contents, commingled organelles and neurofilaments, are destroyed. The myelin sheath is destroyed without being separated from its Schwann cell

ISSN:0002-9106    

DOI:10.1002/aja.1001330105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY

摘要:

AbstractThe establishment of liver parenchyma, extrahepatic ducts and associated venous channels were examined in serial sections of 100 human embryos representative of Horizons XI through XVII.The liver parenchyma first begins to develop from the cephalic end of the hepatic diverticulum in embryos between the 20‐ and 25‐somite stage. The parenchyma develops as cords from the walls of the diverticulum which anastomose around isolated endothelium‐lined spaces (blood islands) in the septum transversum. As growth and anastomoses of the parenchymal cords continue, the isolated endothelium‐lined spaces form an interconnecting capillary bed which interdigitates with the developing parenchymal cords. The larger omphalomesenteric veins develop simultaneously with the parenchyma and are continuous with the smaller venous channels which interdigitate with the parenchymal cords. These larger developing veins become surrounded by the developing parenchymal cords. As the parenchymal cords branch from the cephalic end of the diverticulum, that portion of the diverticulum becomes reduced to a small tubular structure, the common hepatic duct, which is always continuous with the parenchyma. As the cephalic portion of the original diverticulum is reduced in size, there is a localized outgrowth from the ventral wall of the caudal end of the original diverticulum. This localized outgrowth becomes the cystic duct and gallbladder. The remainder of the caudal segment of the diverticulum elongates to become the common bile duct. The ventral pancreas develops as a localized outgrowth from the dorsal wall of the common bi

ISSN:0002-9106    

DOI:10.1002/aja.1001330106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY

摘要:

AbstractTissue containing the attachment of nerve roots to the spinal cord was dissected from seven rats perfused with buffered aldehydes. Both dorsal and ventral roots were obtained from all cord levels. All tissues were prepared routinely for electron microscopy.The outer layers of the root sheath are homologous with the outer layers of the pia mater and are essentially continuous with it. The inner layers of the root sheath, which are a structurally modified and centrally directed continuation of the perineurium across the subarachnoid space, terminate as an open‐ended tube near the junction of the peripheral and central nervous systems. Here there is direct continuity between the endoneurial connective tissue space and the pial connective tissue space. The latter, in turn, communicates directly with the subarachnoid space through fenestrations between pial cells. The relationship of this to certain clinical manifestations is briefly discusse

ISSN:0002-9106    

DOI:10.1002/aja.1001330107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001330101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1972

数据来源: WILEY