16 Questions
What is the peripheral region of the chick blastodisc called?
Area opaca
Which zone of the area opaca is known as the margin of growth?
Peripheral zone
Where do the cells in the inner zone of the area opaca originate from?
Zone junction
Which region of the area opaca forms blood islands?
Germ wall
What gives the area pellucida its translucent appearance?
Overlying subgerminal cavity
Which part of the chick blastodisc initially lacks blood islands or blood vessels?
Area vitellina
What are the fundamental regions of the heart that begin to develop in a chick embryo after 33 hours of incubation?
Truncus arteriosus, ventricle, atrium, and sinus venosus
Which brain region of the developing chick embryo later differentiates into the cerebral hemispheres, thalamus, hypothalamus, and optic vesicles?
Prosencephalon
What does the term 'optic vesicle' refer to in relation to the chick embryo's development?
Paired lateral evaginations containing an opticoel
Which region of the brain is described as the mid region in the developing embryonic brain of a chick embryo?
Mesencephalon
What is the embryological significance of the infundibulum in a chick embryo?
Formation of cerebral aqueduct
What is the role of the notochord in the developing embryo?
Defining the anterior/posterior axis in the embryo
Which structure marks the opening of the foregut in developing amniote embryos?
Anterior intestinal portal
Where are the blood islands found in the developing embryo?
In the yolk sac of amniotes
Which part of the rhombencephalon becomes part of the IV ventricle?
Myelencephalon
What is the role of the intermediate mesoderm in embryonic development?
Developing into pronephros and later mesonephros and metanephros
Study Notes
Development of the Chick Embryo
- 24-hour chick embryo whole mount comprises of area opaca and area pellucida.
Area Opaca
- The peripheral region of the chick blastodisc surrounding the area pellucida.
- Divided into three zones:
- Peripheral zone (margin of growth)
- Zone of junction (intermediate region)
- Inner zone (germ wall)
Area Opaca Vasculosa
- The inner region of the area opaca where thickenings of the splanchnic mesoderm form blood islands.
- Structures to note:
- Sinus terminalis (vein encircling the area vasculosa)
- Blood Islands (masses of splanchnic mesoderm that form the first red blood cells and blood vessels)
Area Opaca Vitellina
- The outer region of the area opaca which initially lacks any blood islands or blood vessels.
Area Pellucida
- The central region of the blastodisc where the primitive streak forms.
- Lies directly over the subgerminal cavity and appears translucent under the microscope.
Brain Development
- Rhombencephalon: the most posterior region of the brain, divided into metencephalon and myelencephalon.
- Metencephalon: anterior subdivision of the hindbrain, forms the metacoel (part of IV ventricle).
- Myelencephalon: posterior region of the rhombencephalon, forms the myelocoel (part of IV ventricle).
- Spinal cord: region of the neural tube posterior to the myelencephalon, with a narrow cavity.
Other Structures
- Notochord: a rod-like structure originating from mesoderm, defining the anterior/posterior axis.
- Nephrotome: a stalk-like connection between somites and lateral plate mesoderm, forms the pronephros, mesonephros, and metanephros.
- Somites: 11-12 pairs present in this stage of development.
- Anterior intestinal portal: the opening of the foregut in developing amniote embryos.
- Foregut: marked by the faint lines extending forward from the margins of the anterior intestinal portal.
- Heart: a single, tubular, S-shaped organ that bulges to the right side of the body.
33-Hour Chick Embryo
- Developmental advances mainly in the brain and heart regions.
- Primary brain vesicles present:
- Prosencephalon (forebrain)
- Mesencephalon (midbrain)
- Rhombencephalon (posterior region of the brain)
- Heart regions beginning to develop:
- Truncus arteriosus
- Ventricle
- Atrium
- Sinus venosus
Learn about the development of the chick embryo with a focus on the 24-hour chick embryo whole mount area opaca. Explore the characteristics of the area opaca, its differentiation into three zones, and its significance in embryonic development.
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