Development of Chick Embryo Stages

In this article we will discuss about the development of chick embryo stages, fertilized eggs are procured from recognised poultry farm and incubated in the laboratory.

Development of chick embryo stages

4 Hours

The blastodisc differentiates into area pellucida and area opaca four hours after egg incubation. The embryo’s future caudal ends will be marked by the thickening of one quadrant of the area pelluciada. The thickening process becomes more extended after 7 to 8 hours. This is the beginning of primitive streak.

Developmental Stages of Chick Embryo Zoology

Chick embryo, 4 hours after incubation (W.M.).

16 Hours

After 16 hours, the embryos’ primitive streak is so evident that they are considered to be in the primitive streak stage W.M. is made up of a central furrow, also known as primitive grooves lined with thickened primitive ridges. Closely packed cells from Hensen’s Node, a thickened area at the cephalic edge of the primitive streak. 

A portion of the pellucida that is adjacent to the primitive streak has an increased thickness and assumes an embryonic elliptical form. Area pellucida assumes an elliptical shape. 

The long axis of the future embryonic body is represented by a long primitive streak. The area opaca is the closest to the caudal end of this streak. Area pellucida assumes an elliptical shape. The long axis of the future embryonic body is represented by a long primitive streak. The area opaca is the closest to the caudal end of this streak.

Developmental Stages of Chick Embryo Zoology 2

Whole mount of chick embryo, 16 hours after incubation.

18 Hours

It is the 18-hour stage development of chick embryo. The darkened area opaca in the peripheral and the central translucent area of pellucida can be clearly seen at this stage of development of chick embryo. 

The pro-amnion is located in the anterior portion. It is a smaller and more translucent area of the pellucida. It is distinguished by the absence mesoderm. The primitive streak runs through the center of the area pellucida’s posterior half. 

Primitive folds are being used to bind the primitive groove. The neural groove is bound by neural folds in the area pellucida’s anterior half. A thickening separates the primitive streak from the neural groove. It has a depression in its centre, known as Hensen’s pit. A primitive streak can lead to an outgrowth, the notochord located below the primitive groove.

Developmental Stages of Chick Embryo Zoology 3

W.M. 18 Hours Chick Embryo.

21 Hours

It is a Whole Mount of 21 hours chick embryo. The visible areas of the central transparent and colourless pellucida, as well as the dark opaca in the perimeter, are clearly visible at this stage development of chick embryo. The pro-anmnion is located in the anterior portion. 

It is a smaller and more translucent area of the pellucida. It is distinguished by the absence mesoderm. The primitive streak runs through the center of the area pellucida’s posterior half. Primitive folds are being used to bind the primitive groove. The neural groove is bound by neural folds in the area pellucida’s anterior half. 

A thickening separates the primitive streak from the neural groove, with the Hensen’s nod containing a small depression at the Hensen’s pit’s centre. A small outgrowth is formed by the primitive streak, which includes the notochord below the primitive groove and mesoderm to either side. In the area of pellucida, embryonic and additional embryonic regions are also distinguished at this stage. 

The ectoderm in the anterior most part has created the head fold. This is a pocket-like extension to neural folds. The ectoderm also transforms the underlying endoderm into a pocket-like structure called the -foregut. The size of the proambion is relatively small.

W.M. of 21 Hours Chick Embryo.

24 Hours

It is a 24 Hours W.M. stage of development of chick embryo, which means that there are 4 pairs of somites in the chick embryo. The chick embryo’s dark outer area is visible, as well as the central transparent and colourless pellucida. The proamnion is located in the anterior portion. It is a smaller and more translucent area of the pellucida. It is distinguished by the absence mesoderm.

The primitive streak runs in the middle of the area pellucida. Its posterior half has a primitive groove at its centre. Primitive folds bind the primitive groove. The neural groove is bound by neural folds in the area pellucida’s anterior half. Hensen’s node, which has a small depression at the centre, is what separates the primitive streak from the neural groove.

The primitive groove is immediately below. A small outgrowth, the notochord, and mesoderm are both found on either side. The area is home to the pellucida embryonic as well as extra embryonic areas. The ectoderm in the anterior-most part has given rise to the head fold, which is an extension of the neural folds that looks pocket-like. 

The pocket-like foregut is also formed from the underlying endoderm. The proamnion shrinks greatly. The mesoderm of the embryonic area was separated into 3-4 pairs by Hensen’s Node. Forebrain is formed in the neural canal at the head fold. The foregut opens on both sides into an amino-cardiac vessel.

W.M. of 24 Hours or 4 Pairs of Somites Stage of Chick Embryo.

30 Hours

This stage development of chick embryo is characterized by the clearly visible darkened area opaca, central transparent and colourless pellucida, and the peripheral area that is dark. The anterior portion is home to the proamnion. 

This is a smaller and more transparent region of the area pellucida. It is distinguished by the absence mesoderm. The primitive streak runs through the center of the area pellucida’s posterior half. Primitive folds bind the primitive groove.

The neural groove is a band of neural folds that runs through the area pellucida’s anterior half. Hensen’s node, which has a small Hensen’s pit in its centre, separates the primitive streak from the neural groove. The primitive streak is located immediately below the primitive groove and the mesoderm is on the other side.

In the area of pellucida, embryonic and additional embryonic areas are also distinguished at this stage. The ectoderm in the anterior-most portion has created the head fold, which is a pocket-like extension of the neural folds. The underlying endoderm is now pocket-like foregut. 

The proamnion has been reduced. 8-10 pairs of somites have been created by the mesoderm in front Hensen’s Node. The fore brain has been formed in the area of the head fold by the anterior portion of the neural canal. The foregut is well developed, as are the cardiac vesicles. The embryonic area that is larger has increased in size.

W.M. of 30 Hours of 8-10 Pairs of Somites Chick Embryo. 

33 Hours

The dark area opaca in the peripheral and central pellucida is not clearly visible at this stage of development of chick embryo. Because of the lengthening and shrinking of neural canals and neural folds, the primitive streak is now comparatively less prominent. The embryonic area that is larger has increased in size. 

11-12 pairs have been created by the mesoderm located in front of Hensen’s node. The foregut is well developed, as are the cardiac vesicles. The brain can be divided into three parts: the forebrain (mid-brain), the mid-brain, and the hindbrain. The area opaca is now called area vasculosa. Proamnion is gone. Anterior omphalomesenteric vein developed.

W. M. of 33 Hour Chick Embryo of 11-12 Pairs Somites.

36 Hours

It is W.M. after 36 hours. The dark outer area opaca, central transparent and colourless pellucida areas are not visible at this stage of development of chick embryo. The embryonic area has increased in size. Because of the great lengthening and shrinking of neural canals and neural folds, the primitive streak is now comparatively less. 

The notochord extends from the brain to the end of the body. 13-14 pairs have been created by the mesoderm located in front of Hensen’s node. The brain can be divided into three distinct regions: the fore, mid and hindbrains. Optic vesicles are found in the fore and hind regions of the brain. 

The area opaca is now called the area vasculosa. Proamnion is gone. The vitelline artery and the anterior omphalomesenteric vein have been developed. Heart was created by the cardiac vesicle.

W.M. of Chick Embryo of 13-14 Pairs Somites or 36 Hours.

48 Hours

It is W.M. for 48 hours chick embryo. The area pellucida and the area opaca are not visible at this stage of development of chick embryo. The embryonic area has increased in size. Primitive streak has disappeared. 26-28 pairs have been created by the mesoderm located in front Hensen’s node. 

The brain can be divided into prosencephalon (telencephalon), prosencephalon (mesencephalon), metancephalon (mylencephalon), mesencephalon (metancephalon) and mesencephalon. The ventricle and atrium have been separated from the heart. The development of sinus venosus, truncusarteriosus, and other parts of the heart has also begun. 

The optic cup and lens have been separated. The optic vesicle is also sufficiently developed. Due to cranialflexion, the head has curled on the right side. The pharyngeal and gill-slits of the pharynx have been also differentiated. A tail bud was also found behind Hensen’s node. The vitelline artery, anterior omphalomesentric and lateral amniotic veins have all been discovered.

W.M. of 48 hours development of chick embryo of 26-28 Pairs of Somites.

72 Hours

The area pellucida and opaca are not visible at this stage of development of chick embryo. The embryonic area has increased in size. Primitive streak has disappeared. 36 pairs of somites have been created by the mesoderm located in front Hensen’s node. The brain can be divided into telencephalon (mesencephalon), metancephalon (mylencephalon), and mesencephalon (metancephalon). 

The ventricle and atrium have been separated from the heart. The eye has been divided into an optic cup and lens. Additionally, the optic vesicle is now sufficiently developed. Cranial flexion has caused the head to bend on the right side. There are four pairs of gill slits. 

The tail bud is very well developed, which has led to the development of allentoic stalks and tails. The anterior omphalomesentric and vitelline veins, lateral amniotic folds, and vitelline arterial have all developed. The middle region is home to a pair fore limb buds, and the front of the tail to a pair hind-limb buds. These will produce fore and hind limbs. Visceral arches and the amniotic cavity, as well as the olfactory pit and visceral arches have all been developed.

W.M. of 72 Hours or 36 Pairs of Somites development of chick embryo

96 Hours

After 96 hours of incubation, the whole embryo has been rotated 90 degrees so that the egg lies on its left side. The embryo is now attached to the yolk by a thin stalk. The yolk saltk quickly becomes enclogated and the embryo can become straight in the mid-dorsal area, then convex dorsally. 

As the cranial, cervical and dorsal flexures increase, the embryo bends on itself, so its original straight long axis becomes C-shaped. Its head and tail are closer together. The more developed lens is visible in the optic cup. From the auditory vesicle, an endo-lymphatic conduit arises. 

Visceral arches are now thicker. Appendage buds grow rapidly and become more elongated. 41 pairs of somites are now present. Allantois also appears. Also, the omphalomesenteric artery is also known as the Omphalomesenteric Vein.

Developmental Stages of Chick Embryo Zoology 11

W.M. of 96 hours development of chick embryo

Further Readings