Elaboration of yolk- reproduction, Biology

Elaboration of Yolk- Reproduction

Elaboration of nutritive material, vitellin or the yolk, for the early states of embryonic development is one of the important functions of the non-mammalian ovary. You are aware that mammals except monotremes and marsupials are viviparous. The development of the embryos in the viviparous animals takes place inside the mothers" body. Nutrition and other required things are provided to the embryos through maternal circulation. Most of the non-mammalian vertebrates are oviparous forms in which development of the embryos takes place outside the mothers' body. Therefore they have to be provided with nutrient material enough for the development till they reach a stage at which they manage to procure food by themselves.

The nutritive material in the oviparous animals is stored in the egg cytoplasm in the form of yolk. The constituents of the yolk are proteins, lipids, glycogen, nucleic acids and some minerals like phosphors. The process of yolk synthesis is called vitellogenesis. Vitellogenesis is under the control of gonadotropins. Gonadotropins induce the synthesis and secretion of estrogens in the ovary, which in turn stimulate the synthesis of vitellogenin, a yolk protein in the liver secreted into the blood stream. Vitellogenin reaches the ovary through blood and enters the egg cell. In the cytoplasm it is used in the yolk synthesis. Apart from egg production, synthesis of hormones and yolk, ovaries also play a vital role in the maintenance of pregnancy.

Posted Date: 1/16/2013 7:13:20 AM | Location : United States







Related Discussions:- Elaboration of yolk- reproduction, Assignment Help, Ask Question on Elaboration of yolk- reproduction, Get Answer, Expert's Help, Elaboration of yolk- reproduction Discussions

Write discussion on Elaboration of yolk- reproduction
Your posts are moderated
Related Questions
Disorders of Pituitary Function: The disorders of pituitary function result  in following conditions.  Hypopituitarism : Growth Hormone  (GH) Deficiency Hypopituitarism is

What are the main constituents of the earth's atmosphere in our time? The present atmosphere of the earth is constituted mostly of molecular nitrogen (N2) and molecular oxygen

Q. What is Osmotic diarrhoea? This kind of diarrhoea is caused by the presence of osmotically active substances in the intestinal tract, which in turn, favour the drawing of la

Digestion  of proteins Digestion  of proteins  is  initiated  in  the  stomach by pepsin.  Pepsin  acts upon food proteins  and  converts them  to proteoses  and  peptones whic

Define the Prevention of diseases - Function of Vitamin E? Because of its anti-oxidant function and its role in inhibiting cell proliferation of smooth muscles, vitamin E can b

a) What is meant by 'vaso-dilation'? b) What are the effects of vaso-dilation in the skin?   (a) Vaso-dilation is an enhance in diameter of small arterioles and

The sugar carried in the blood is glucose; the normal value of sugar in the human bloodstream is approximately 90mg per 100 bloods. Sugar is absorbed from the small intestines and

CHOROI D - Thin, net like made up of connective tissue, rich in blood vessels. Pigment present, red in rabbit, brown or black in man. It reduces internal reflection.

Q. What is Subxiphoid Short Axis Sweep? To obtain the subxiphoid short axis view transducer should be rotated by 90 degree clockwise, fi-om the previous position so that p

do you think the social and cultural environment of the 18th and 19th centuries helped or hindered the study of microbiology in particular and science in general