摘要:

AbstractThe development of the hepatic diverticulum was examined in 38 human embryos representing somite stages 1, 5, 8 and 10 through 29, inclusive. Interpretations were based on light microscopic study of serial sections of these embryos.The liver primordium was first identified in a five‐somite embryo as a flat plate of endodermal cells continuous with, but lying ventral to, the endoderm of the foregut at the anterior intestinal portal. It is positioned caudal and ventral to the developing heart. This plate of endoderm subsequently undergoes a progressive folding due to differential growth of adjacent structures. During the folding process there is a close spatial relationship between the cells of the endodermal plate and the caudal and ventral endothelial lining of the atrium and the sinus venosus. The result of this folding is the establishment of a “T‐shaped” diverticulum which projects ventrally and cephalically from the gut tract. The hepatic diverticulum is established by the 20 somite‐stage embryo. This mode of development of the hepatic diverticulum is compared to the classical interpretation and to the development of other viscer

ISSN:0002-9106    

DOI:10.1002/aja.1001310202

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

年代:1971

数据来源: WILEY

摘要:

AbstractImplantation in the beaver is superficial and antimesometrial. The embryonic disc occupies one side of the flattened mesometrial hemisphere of the large blastocyst. An endometrial papilla, unique to the beaver, forms on the mesometrial uterine wall just prior to chorioallantoic contact. The reniform placenta then develops around this papilla. Amniogenesis is by folding. A transient choriovitelline placenta develops very early. Yolk sac inversion is late, and the bilaminar omphalopleure is partially retained throughout gestation. The chorion persists until term as two paraplacental membranes. A large permanent allantoic vesicle is present. The labyrinthine placenta has a lobulate architecture. It possesses a hemodichorial barrier, the inner layer being syncytial and the outer cellular. Maternal blood is supplied by two arterial channels which do not penetrate the labyrinth, and is drained by a single, central venous channel. A large basal subplacenta develops by trophoblastic invasion of the endometrial papilla, and becomes quite massive at term. Its function is unknown. Except for this specialized subplacenta, all the fetal membrane characteristics are typical of the primitive sciuromorph group, to which the Castoridae seem to be closely related.

ISSN:0002-9106    

DOI:10.1002/aja.1001310203

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

年代:1971

数据来源: WILEY

摘要:

AbstractThe secretory terminations of monkey submandibular gland were studied by electron microscopy. The acini are composed of two types of secretory cells which are presumably serous and mucous in type. Myoepithelial cells are present also in the acini. The peri‐acinar connective tissue contains many unmyelinated nerve fibers. In some portions, the axons contain many synaptic vesicles of various types. These nerve endings partially lose their Schwann cell investment and reach the acinar basement membrane. In peri‐acinar connective tissue two types of nerve endings may be recognized. They are thought to be adrenergic and cholinergic in type. On the other hand, only one type of nerve ending (cholinergic) is observed within the acini. The intra‐acinar nerve endings are not surrounded by Schwann cell cytoplasm and make direct contact with plasma membranes of the myoepithelial and mucous cells, with a space about 200 Å wide intervening between the nerve and terminal cell. No nerve endings occur in the interspaces between the serous cells. Also, the ultrastructure of the secretory and myoepithelial cells is des

ISSN:0002-9106    

DOI:10.1002/aja.1001310204

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

年代:1971

数据来源: WILEY

摘要:

AbstractThe fine structure of developing cartilage is described in the area of the future vertebral bodies in the cervical region of chick embryos. Incubation ages range from 36 hours, when the sclerotome of the somite begins to break up, to the thirteenth day. In the 36‐ to 72‐hour interval cells of the sclerotome become free and assume stellate form. Polyribosomes nearly fill the largely undifferentiated cytoplasm. Microfibrils and amorphous material appear in the connective tissue spaceThe extent of the connective tissue space is determined by boundary (basement) membranes; externally by those of epithelium facing the geometric exterior of the organism and internally by those of endothelium, mesothelium, muscle, nerve and fat. The true contents of the connective tissue space are the connective tissues. As used in this paper “connective tissue space” refers to the extracellular portion, in which the fibrous and amorphous components exist.by the end of the third day. From the fourth through the sixth day both cellular contours and contents suggest fibroblasts. Microfibrillar diameter increases from 50 to 150 Å. Periodicity does not occur. Matrix granules appear and establish contact with microfibrils. From the eighth through the eleventh day the predominating cell types are chondroblasts and chondrocytes whose fine structure is typical. Microfibrils become more numerous and matrix granules larger. During days 11 through 13, chondrocytes show degenerative changes including lucid areas of nucleoplasm and cytoplasm with fragmentation of endoplasmic reticulum. Microfibrils and matrix granules are heavily concentrated in the connective tissue space and lucent osteoid

ISSN:0002-9106    

DOI:10.1002/aja.1001310205

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

年代:1971

数据来源: WILEY

摘要:

AbstractInjection studies were made of the blood vessels of developing human teeth, using 114 unfixed aborted fetuses and new‐born infants ranging in gestation age from three through nine months. These specimens were injected with India ink‐formalin, Micropaque‐formalin, Microfil, or vinyl acetate solutions via the umbilical vessels; in cases where an autopsy had been performed, injection was made through the carotid artery. After further fixation by immersion in 10% neutral formalin, the head was bisected in the sagittal plane. One half was dissected and tissue obtained for microscopic study; the other half was radiographed, dissected or dehydrated and cleared. These techniques revealed that the plexus of vessels which surrounds the developing dental organs is derived mainly from the inferior alveolar and palatine arteries, respectively. However, branches from vessels in adjacent tissues also supplied this plexus. The teeth growing most rapidly, and which usually erupt the earliest, receive the largest blood supply.Odontoblasts were supplied by vessels which course through the dental pulp to their deeper surface. The ameloblasts were adjacent to vessels in the capillary plexus on the outer surface of the enamel organ. A venous sinus was located at the base of the dental

ISSN:0002-9106    

DOI:10.1002/aja.1001310206

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

年代:1971

数据来源: WILEY

摘要:

AbstractThe fine structure of bat thyroid follicular cells was examined throughout the late hibernation period (January 17 to April 1), when thyroid gland function undergoes marked increase. The follicular cells during this period are squamous and possess few microvilli, an inconspicuous Golgi complex, scanty rough‐surfaced endoplasmic reticulum and a small number of mitochondria. The cells also exhibit conspicuous membrane‐limited dense bodies and atypical intercellular contacts. The atypical junctional complexes are characterized by a localized dense thickening of the apposed lateral plasma membranes which run parallel to each other for approximately 1 μ. The two dense membranes are separated by an intercellular space 75 Å wide and there is close apposition of rough‐surfaced endoplasmic reticulum and mitochondria. The occurrence of these unusual junctional complexes during late hibernation is discussed in relation to the known increase in thyroid function which occurs at th

ISSN:0002-9106    

DOI:10.1002/aja.1001310207

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

年代:1971

数据来源: WILEY

摘要:

AbstractEpithelial regeneration was determined with light and electron microscopy after preferential chemical destruction of olfactory epithelium in rabbits. Regeneration of either olfactory epithelium, ciliated columnar epithelium or a mixture of the two occurred. Previously observed interspecies variation in olfactory regenerative capability is therefore also an intraspecies variable. The ducts or glands of Bowman appeared to furnish the cells for either type of epithelial regeneration. Well differentiated olfactory cells re‐appeared as early as eight days after destruction with olfactory regeneration being essentially completed 30 days after destructio

ISSN:0002-9106    

DOI:10.1002/aja.1001310208

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

年代:1971

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001310201

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

年代:1971

数据来源: WILEY