• 48 Hour Chick Embryo Serial Cross Section 1
• 24 Hour Chick Embryo

Observation of living and plastic-embedded chick embryos

48 hour chick embryo serial cross section. With the use of serial cross-sections of chicken embryos, you are about to embark on one of the. 24-hour Chick Embryo. Serial Cross sections Photograph 01 of 15: 24 Hour Chick Section 2 of 240 through anterior tip of head fold. In this section, the anterior tip of the head fold can be seen. The portions that are visible at this level are portions of the neural folds.

The development of chick embryos has been studied since Aristotle. It is one of the most intensely studied organisms. One reason for this is that there are great similarities between avian and mammalian embryology. Another advantage is that the embryo is relatively accessible and can be operated on or treated with teratogens (substances that perturb development) while still in ovo(in the egg). Finally, fertilized chicken eggs are available year round and can be 'held' at 10-14ºC for several weeks before being set, producing embryos upon demand.

Embedded embryos

1. Examine plastic embedded specimens of '13-hour' or '16-hour', '24-hour', '33-hour','48-hour' and '72-hour' chick embryos. These terms refer to classic studies of chick development. In reality, chick embryos will develop at different rates for a number of reasons, including incubation temperature. In modern times, chicks always take longer to reach these stages. Two more accurate ways of describing the relative developmental age of a chick embryo are (1) the number of somites and (2) comparison to a staging series, such as the one devised by Hamburger and Hamilton (H&H; hamburger.pdf). The somites are the blocks of tissue on either side of the neural tube. Try to determine the number of somites and the H&H stage number of your embryos.

2. Try to identify the structures indicated in the diagrams. Pay particular attention to the developing circulatory system. Try to determine which germ layer forms each structure. Highlights include:

13- to 16-hour.Identify the area opaca and area pellucida. Locate the primitive streak. Hensen's node is located at the anterior end of the streak.

24-hour.Locate the neural folds and Hensen's node. Identify the anterior end of the embryo.

33-hour.The embryo is lying along the center of the blastodisc, dorsal side up. The heart is to the right, along the side of the hindbrain. It is a simple, looped tube;connected to the vitelline vein and the ventral aorta. What is the function of the vitelline vein? Identify the forebrain, midbrain and hindbrain. The optic vesicles are outpockets on either side of the forebrain. The neural plate runs along the dorsal midline and is not yet closed. You may also be able to see the notochord running along the midline.

48-hour.The head has bent forward and the body has begun to twist. The optic cup(eye) and the otic vesicle (ear) have formed. The neural tube has closed, except in the region of the hindbrain. A series of aortic arches run between the pouches

This page on the embryology in chicken relates to the following:

48 Hour Chick Embryo Serial Cross Section 1

Whole mount preparation 72 hours, with a detail view on the development of the head (More...)

Cross sections 72 hours; eye and heart formation (More...)

24 Hour Chick Embryo

Stage 72 hours

Whole-mount preparation 72 hours after fertilization
Information: 72 Hours after fertilization, the rotation of the embryo to the left is arrived such behind the region of the heart and only the caudal part of the embryo must twist 90 degrees. The two flexures in the head region are almost completed. The fourth pharyngeal groove develops and the pharyngeal arches are thicker. Due to the cranial flexure, the pharyngeal region (= region of the trachea) is now located at the ventral side of the head. The fore and hind limbs at the level of the 16th to the 20th respectively the 27th to the 32th somite pairs are visible as small buds at an incubation time of about 3 days.
Embryology of chicken 72 hours after fertilization: stained whole-mount preparation. 1 = Auditive (otic) vesicle, 2 = Myelencephalon, 3 = Metencephalon, 4 = Amnion, 5 = Mesencephalon, 6 = Optic vesicle + lens, 7 = Diencephalon, 8 = Epiphyse, 9 = Telencephalon, 10 = Branchial arches, 11 = Heart, 12 = Forelimb (wing) bud, 13 = Vitelline arteria/vein, 14 = Hindlimb (leg) bud, 15 = Tail
Information: The development of the brain is shown at higher magnification. The further development of the five brain vesicles (telencephalon, diencephalon, metencephalon, mesencephalon and myencephalon) in to the different head structures is clearly visible. The eye vesicles differentiate as two lateral projections of the diencephalon and come in contact with the external layer (ectoderm) to form the optic cup (neurectoderm) and the lens (ectoderm). The dorsal projection of the dieencephalon is also visible and will differentiate in to the epiphysis (epi= at the upper side). The depression at the ventral side of the diencephalon develops in to the hypophysis ( hypo= under; not visible in this fig.). The auditory vesicles develop at the level of the myencephalon.
Embryology of chicken 72 hours after fertilization: detail of the head in a stained wholemount preparation 1 = Auditive (otic) vesicle, 2 = Myelencephalon, 3 = Metencephalon, 4 = Amnion, 5 = Mesencephalon, 6 = Optic bulb, 7 = Lens, 8 = Diencephalon, 9 = Epiphyse, 10 = Telencephalon, 11 = Olfactory groove

Cross sections 72 hours
A. Eye and heart formation: left wholemount and right cross section (dorsal part oriented to the left) 1 = Spine, 2 = Dorsal aorta, 3 = Foregut, 4 = Heart formation, 5 = Lens, 6 = Optic vesicle, 7 = Diencephalon, 8 = Heart region, 9 = head
B. Heart formation: left wholemount preparation and right cross section (dorsal side oriented to the left) 1 = Spine, 2 = Dorsale aorta, 3 = Pleural cavity, 4 = Foregut with folding of the lung bud, 5 = Sinus venosus, 6 = Truncus arteriosus, 7 = Atrium, 8 = Regio cerebrale hemisphere of the telencephalon, 9 = Diencephalon, 10 = Olfactory groove, 11 = Heart region, 12 = Head region