Development of Chick Embryo - MJF Veterinary College

Mahatma Jyotiba Fule College of Veterinary Science and Animal Husbandry, Chomu (Raj.)

PRESENTED BY:

Dr. Lakshmi kant

2019-2020

Assistant professor

DEPARTMENT OF VETERINARY ANATOMY AND HISTOLOGYCOLLEGE OF VETERINARY SCIENCE & ANIMAL HUSBANDRY, CHOMU

(RAJ.)

Development of Chick Embryo

DEVELOPMENT OF CHICK EMBRYO

ORGANOGENESIS

Development of chick embryo

CHICKEN

• Is a domesticated fowl.• As one of the most common and widespread domestic animals.

CLLASSIFICATION• Kingdom:• Phylum:• Class:• Order:• Family:• Subfamily:• Genus:• Species:• Subspecies:

Animalia Chordata Aves Galliformes Phasianidae Phasianinae GallusG. gallusG. g. domesticus

CHICK EGG

EGG

A fully formed and newly egg islarge and elliptical with one end(broader than the other).

TYPE

The egg of chick is telolecithal( having a large yolk situated ator near one end).

RELEASE

The egg is released from theovary, it takes 24 hours to passdown the oviduct, before beinglaid.

CHICK EGG

FERTILIZATION

• The fertilization is internal, upper part of theoviduct, resulting two polar bodies degenerate anddisappear.

STRUCTURE OF EGG & SHAPE

• It is oval in shape.

SIZE

• 3cm wide and 5cm long.

SHELL

• Made up 95% calcium carbonate, white and porous andexchange of gases occur, soft and flexible in a freshly -laidegg but soon become hard and brittle.

MEMBRANE• Two types of membrane, shell membrane and vitellinemembrane, separated at the broad end of the egg to enclose anair space.YOLK MEMBRANE• The layer of yellow yolk is thicker than those of the white yolks.Yolk contains about 50% water.Yolk consist of phospholipids, lecithin• Yellow yolk shows 60% fats and 70% proteins.• White yolk contains less fat and also less of fat soluble carotene.CHALAZA•Two end of the egg are some fibrous, rope like twistedstructure formed during journey of the oviduct.LATEBRAThe central flask shaped area that is enclosed of white yolk is calledlatebra.

ALBUMENIt has two types :Thick albumen and thin albumen GERMINAL DISC OR BLASTODIC/ BlastodermNucleus of the egg is surrounded by the negligible amount of yolk free cytoplasm called germinal disc.

DEVELOPMENT OF CHICK

CLEAVAGE OR SEGMENTATION

• It starts with the cleavage.

• It is meroblastic means confined to small area ofblastodisc (Duration it takes 12-16 hours).

• First cleavage forms two cells.

• Second cleavage occurs after 20 min of first cleavagefour cells formed.

• Third cleavage eight cells formed.

• Irregular cleavage occurs in four hours at theend cleavage 256 irregular cells formed.

CLEAVAGE OR SEGMENTATION

BLASTULATION

• After cleavage, blastulation occurs, dueto blastulation following structureformed.

• Sub-germinal cavity: it is similar toblastocoel.

• Area pellucida:

The translucent central area of the

blastoderm. Form the body proper.

• Area opaca:

The opaque area of the blastoderm

surrounding the area pellucida.

Help in the formation of extra

embryonic membrane such as yolk

sac.

PROCESS OF GASTRULATION

• Conversion of monoblastic egg into triplo-blastic gastrula.

• Gastrulation involves the formation of ectoderm, endoderm and mesoderm.

PRIMITIVE STREAK

• It is groove on the surface along the (future)anterior-posterior axis.

PRIMITIVE STREAK FORMATION

• The primitive streak is formed from the posteriormarginal 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 thehypoblast(endoderm) by the blastocoel.

• The epiblast will give rise to the three germ layersthe embryo, while the hypoblast will give rise toextra embryonic structure.

PRIMITIVE STREAK EXTENTION 15-16

HOURS AFTER FERTILIZATION

• The primitive streak extends by convergent extensionfrom the posterior to anterior pole.

• A depression form along the primitive streak calledprimitive groove.

18Hrs Chick Embryo

• Longitudinally oriented Primitive Streak is more obvious.

• Primitive fold is observable.

• Primitive groove is the invagination between primitive fold.

EXTRA-EMBRYONIC MEMBRANES

Yolk sac membrane

• The first of the extra-embryonic membranes to develop is the

yolk sac membrane.

• Initially recognised as the area vitellina, this is the outer area of

the blastoderm, consisting of three cell layers, which are a

continuation of the cell layers of the embryonic disc.

• There is an ectodermal layer adjacent to the vitelline

membranes,

• an endodermal layer adjacent to the yolk and in between a layer

of mesoderm cells.

• The mesoderm is split into two by a cavity, the extraembryonic

coelom, and only the mesoderm next to the endoderm develops

blood vessels (called the vascular mesoderm).

EXTRA-EMBRYONIC MEMBRANES

Amnion

• The flat tissue rises up to form folds over both the head

and tail of the developing embryo and by day 4 of

incubation the folds fuse together over the embryo to

enclose the amniotic sac.

• Consequently, the inner layer of the amnion is ectoderm,

and the outer one is avascular mesoderm.

EXTRA-EMBRYONIC MEMBRANES

Serosa

•Actually the inner layer of the amniotic fold fuse to form

the amniotic cavity and the outer layer forms the serosa.

•The extra-embryonic coelom is developed between the

serosa and amnion.

EXTRA-EMBRYONIC MEMBRANES

Allantois

•It appears on 3rd day as a diverticlum.

•It comes out and grow fast up to 10 days of incubation and

becomes extents with in the sero amniotic cavity (extra-

embryonic coelom) and there by surrounds the embryo as well

as yolk sac.

EXTRA-EMBRYONIC MEMBRANES

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