Data/hora: 23/06/2024 03:58:45

Biblioteca(s): 	Embrapa Pantanal.	
Data corrente: 	30/03/1999	
Data da última atualização: 	30/03/1999	
Autoria: 	FORBES, T. R.	
Título: 	Studies on the reproductive system of the alligator. IV. Observations on the development of the gonad, the adrenal cortex, and the Mullerian duct.	
Ano de publicação: 	1940	
Fonte/Imprenta: 	Carnagie Institute, v.28, n.174, p.131-155, 1940.	
Idioma: 	Inglês	
Notas: 	+ 4 plates.	
Conteúdo: 	The Gonad
1. The genital ridge is first seen as a tickening of the coelomic epithelium on the ventral and ventromedial surface of the mesonephros. The proliferating epithelium of the genital ridge is continuous medially with the primordium of the adrenal cortex. Epithelial proliferations from the ridge, at first with out organization, are later grouped into primary sex cords. Rete cords and infrequent germ cells are present. The germinal epithelium proper is completely blended with the underlying proliferation.
2. At a stage of 75 to 88 mm. head and trunk lenght there occurs a period of bisexuality. The gonal ios characterized by a well-defined layer of simple germinal epithelium (potential cortex) and a subjacent zone of medullary cords (potential seminiferous tubules). Thus both male and female gonad components are present in a primitive form. The germ cells have increased in  number. A primitive tunica albuginea is present.
3. During the succeeding period visible sex differentiation takes place. The ovaries develop a well-defined germinal epithelium in which germ cells are fairly numerous; the medullary cords are regressing and distended by large irregular cavities. The tests retain limited cortical areas external to the tunica albuginea; the medullary cords, still lacking lumina, are prominent and contain germ cells. Rete cords are infrequent.
4. The developmental progress shown by the gonads at three, six, twelve, and eighteen months after hatching is described. At the last-mentioned stage the ovary possesses a well-developed cortex crowded with ovogonia and ovocytes. The underlying medulla consists typically of a loose network of conective tissue strands separated by large lacunae; however, at the posterior end of the ovary there persists an area of solid medullary tissue which resembles a primitive testis and which lacks a cortex. Local cortical areas persist on the surface of the testis, where they lie external to and penetrate the dense tunica albuginea; a case of abnormal persistence of testicular cortex is described. The medullary cords have become incipient seminiferous tubules. Spermatogonia are numerous. 
5. The evidence indicates athat both male and female alligators exhibit a considerable degree of embryonic and juvenile bisexuality.
The Adrenal Cortex
6. The primitive adrenal cortex is seen as a thickened mass of coelomic epithelium lying on the ventromedial surface of the mesonephros and extending laterally from the root of the mesentery to the genital primordium, with which it is continuous. Buds are proliferated from the cortical promordium at an early stage and extend rapidly into the mesenchyme between the mesonephros and the aorta. The cortical cords become detached from their point of origin, but continue to increase in lenght and complexity. Adrenal medullary tissue migrates ventrally into the cortical mass. At the time of hatching the gland shows an organization essentially like that seen in the latest post-hatching stages sstudied.
7. In the alligator embryo the gonadal medullary cords and adrenal cortical cords have their origin as proliferation from contiguous regions of an area of coelomic epithelium; the two proliferations are initiated at the same time and at first have a marked histological resemblance. It is suggested that these morphological observations lend support to the concept, suggested by earlier writers on the basis of mammalian studies, that both male and female adrenal cortical tissue may under some circumstances show a physiological similarity to functional testicular (gonadal medullary) tissue by elaborating an androgenic substance. 
The Mullerian Duct 
8. The primordium of the Mullerian duct appears as an epithelial area interposed in the peritoneum and lying at the dorsolateral angle of the mesonephros. As development progress the epithelial plate becomes deeply grooved; the groove closes over, except at its ostial extremity, to form the anterior portion of the duct. The latter is completed by a posterior extension of a solid epithelial mass which secondarily develops a lumen. The duct extends caudally to, but does not actually communicate with the lumen of, the cloaca. This condition persists in the female in the most advanced post-hatching stages studied. In the male, the Mullerian ducts are fully formed prior to hatching, but have disappeared soon after hatching except for occasional short and more or less rudimentary segments which are present even in the oldest males to be examined. 	
Palavras-Chave: 	Gonad; Gonadas; Mullerian duct; Reptile.	
Thesagro: 	Jacaré; Reprodução; Réptil.	
Thesaurus Nal: 	adrenal cortex; reproduction.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Pantanal (CPAP)	
Exemplares: 	CPAP - (37878-1) - ADD - SP - -- - SP4438 -  - 4438 - DIS