Development of chick powerpoint
•Download as PPTX, PDF•
43 likes•46,533 views
The egg of a chick is oval in shape, approximately 3cm wide and 5cm long. It has a porous shell made of calcium carbonate that allows for gas exchange. Inside are two types of membranes, the shell membrane and vitelline membrane, that separate to enclose an air space at the broad end. The egg undergoes fertilization internally in the upper part of the oviduct, where two polar bodies degenerate. Over 12-16 hours, the fertilized egg undergoes cleavage and then blastulation, forming three germ layers and extraembryonic structures through gastrulation and organogenesis.
Development of chick powerpoint
- 3. EGG A fully formed and newly egg is large and elliptical with one end broader than the other . TYPE The egg of chick is telolecithal ,sub type of polylecithal. RELEASE The egg is released from the ovary, it takes 24 hours to pass down the oviduct, before being laid . FERTILIZATION The fertilization is internal ,upper part of the oviduct, resulting two polar bodies degenerate and disappear.
- 5. STRUCTURE OF EGG SHAPE It is oval in shape SIZE 3cm wide and 5cm long SHELL Made up 95% calcium carbonate, white and porous and exchange of gases occur, soft and flexible in a freshly –laid egg but soon become hard and brittle. MEMBRANE Two types of membrane, shell membrane and vitalline membrane , separated at the broad end of the egg to enclose an air space
- 6. YOLK MEMBRANE The layer of yellow yolk are thicker than those of the white yolks. Yolk consist of phospholipids, lecithin Solid yolk shows 60% fats and 70% proteins Whit yolk contains less fat and also less of fat soluble carotene to which the yellow colour is due Yolk contains about 50% water ALBUMEN It has two types Thick albumen and thin albumen CHALAZA Two end of the egg are some fibrous ,rope like twisted structure formed during journey of the oviduct LATEBRA The central flask shaped area that is enclosed of white yolk is called latebra GERMINAL DISC OR BLASTODIC Nucleus of the egg is surrounded by the negligible amount of yolk free cytoplasm called germinal disc
- 8. DEVELOPMENT OF CHICK CLEAVAGE OR SEGMENTATION It starts with the cleavage It is meroblastic means confined to small area of blastodisc Duration it takes 12 16 hours First cleavage forms two cells Second cleavage occurs after 20 min of first cleavage four cells formed Third cleavage eight cells formed Irregular cleavage occurs in four hours at the end cleavage 256 irregular cells formed BLASTULATION After cleavage, blastulation occurs, due to blastulation following structure formed Sub-germinal cavity : it is similar to blastocoel Area pellucida: Form the body proper Area opaca: Help in the formation of extra embryonic membrane such as yolk sac
- 10. PROCESS OF GASTRULATION Converting of monoblastic egg into triploloblastic gastrula Gastrulation involves the formation of ectoderm, endoderm and mesoderm PRIMITIVE STREAK FORMATION The primitive streak is formed from the posterior marginal region cells . The streak first becomes visible as the epiblast (ectoderm) thickens at the posterior pole . PRIMITIVE STREAK FORMATION 7-8 HOURS AFTER FERTILIZATION The epiblast (ectoderm) is separated from the hypoblast by the blastocoel The epiblast will give rise to the three germ layers the embryo, while the hypoblast will give rise to extra embryonic structure. PRIMITIVE STREAK EXTENTION 15-16 HOURS AFTER FERTILIZATION The primitive streak extends by convergent extention from the posterior to anterior pole. A depression form along the primitive streak called primitive groove.
- 12. FORMATION OF HENSON’S NODE 19-22 HOURS AFTER FERTILIZATION This bird eyes view shows the primitive streak and Henson’s node . At this stage ingression through the primitive streak of cells destined to become endoderm and mesoderm has begun. HENSON’S NODE It is formed by cells of presumptive notochord and floor of neural tube . FORMATION OF NOTOCHORD (NOTOGENESIS) A narrow strip of blastoderm just in front of primitive knot consist of presumptive notochordal cell responsible for the formation of notochord. FORMATION OF NEURAL TUBE (NEUROGENESIS) In front of the primitive streak lie neural plate cells . These cells folds roll up and unite mid-dorsally ,enclosing a neural tube , forming fore brain , mid and hind brain. MEROBLASTIC SOMITES On either side of notochord lies thick, solid, dorsal somatic
- 13. ORIGIN OF COELOM The ventral or lateral plate mesoderm split into two layers The outer somatic or parietal layer lies next to ectoderm with which it forms the somatopleure The inner splanchnic or visceral layer in contact with endoderm form the splanchnoplure. Space or cavity formed between these two mesodermal layers is coelom or splanchnocoel. ORGANOGENY Formation of organs is called organogeny
- 14. EXTRA EMBRYONIC MEMBRANE OR FOETAL MEMBRANE YOLK SAC The chief embryonic food is yolk which is surrounded by the sac like investing membrane called yolk sac Yolk sac is made up of splanchopluere FUNCTION: The function of yolk sac is to protect the yolk keep it in position , digest and absorb it. Yolk sac serves as a primary organ of nutrition of embryo AMNION : It is made up of inner ectoderm, the space between amnion and embryo is filled with amniotic cavity having amniotic fluid. FUNCTION It protect the embryo from mechanical jerks and prevent its desication.
- 15. CHORION It is made up of outer ectoderm ,the cavity between amnion and chorion is called chorionic cavity FUNCTION Chorion also provides the liquid medium for the embryo. ALLANTOISE The bladder like structure is called allantoise Allontoise is made up of splanchnopleure endoderm inside and splanchnic mesoderm outside ALLANTO- CHORION The mesodermal layers joined the allantoise with chorion called allanto-chorion , a compound layer is formed FUNCTION It serves as Respiratory organ ,Excretory organ, Nutritional organ