The zygote cell is the first stage of the embryo. The zygote contains DNA from both parents which create a unique new identity that has never existed. That is the start of a baby, therefore a pregnancy is not just the woman and her body; new life has already begun since the zygote has the four criteria needed to establish biological life which include growth, metabolism, reaction to a stimuli, and reproduction. About 22 days after conception the baby’s heart begins to circulate its own blood and a heartbeat can be detected and by six weeks that same baby has facial features and brain activity has begun. By after just 10 short weeks, still in the first trimester, the baby can…
Forms stroma (scaffolding) of highly cellular organs on which they arrange their parenchyma (functional cells)…
Ovules begin life as a small projection into the cavity of the ovary. Still remaining attached to the ovary wall by a placenta, the ovule bends as it grow and develop. In the beginning, the ovule is a group of similar cells that is called the nucellus. The nucellus contains the embryo sac. As development continues, the mass of cells differentiates to form the inner and outer integument that surrounds and protects the nucellus, but leaves a small opening called the micropyle. This opening is to allow male gametes to pass and interact with the female gamete (haploid egg cell) located in the embryo sac. Each anther contains four pollen sacs. Pollen grains develop inside each pollen sac that begins with a mass of large pollen mother cells in each sac that are all diploid. The wall thickens in each pollen grain and forms an inner layer called the intine and an outer layer called the exine. Surface patterns are different on pollen grains from different species. After pollen grains have matured, the anther dries out and splits open, which releases the pollen. This process is called…
Hensen’s node is the neural organizer in amniotes which signals the primitive streak, the site of invagination during blastulation. Grafting of Hensen’s node to the anterolateral region generates a patterned nervous system (Stern, 2005). RNA from Hensen’s node was used because Hensen’s node is the site of neural induction and as such, proteins encoded by expressed transcripts in this region should be implicated in induction and gastrulation. RNA was used to generate a cDNA library selecting for secreted…
Epithelial tissues are the inside layer of internal and external surfaces and body cavities, including ducts carrying secretions from glands. They may be composed of some layers of cells, called compound epithelia or just a single layer which is known as simple epithelia. The lowest or bottom layer of cells is attached to the basement membrane for support and connection. Part of the basement membrane is concealed by the epithelia but they are supplied with oxygen and nutrients from deeper tissues by diffusion which is the passage of the molecules from a high concentration to a low concentration. As they are surface tissues and exposed to friction, their ability for growth and repair is greater than other tissues and generally occurs during sleep.…
The large round cells allow it to slide or move past each other. It also allows the tissue to stretch .…
viii. Gastrulation-After cleavage, a rearrangement of cells forms a 3-layered embryo with a primitive gut.---3 germ layers(embryonic tissues) are created; endoderm, mesoderm, and ectoderm…
Enchanted Learning . (2010). Animal Cell Anatomy . Retrieved May 31, 2012, from Enchanted Learning : http://www.enchantedlearning.com/subjects/animals/cell/…
Sinauer AssociatesTopic Number Search Bioethics Help Home Link Contents for all chapters 1. Developmental Biology: The Anatomical Tradition 2. Life Cycles and the Evolution of Developmental Patterns 3. Principles of Experimental Embryology 4. The Genetic Core of Development 5. The Paradigm of Differential Gene Expression 6. Cell-Cell Communication in Development 7. Fertilization: Beginning a New Organism 8. Early Development in Selected Invertebrates 9. The Genetics of Axis Specification in Drosophila 10. Early Development and Axis Formation in Amphibians 11. The Early Development of Vertebrates: Fish, Birds and Mammals 12. The Emergence of the Ectoderm: Central Nervous System and Epidermis 13. Neural Crest Cells and Axonal Specificity 14. Paraxial and Intermediate Mesoderm 15. Lateral Plate Mesoderm and Endoderm 16. Development of the Tetrapod Limb 17. Sex Determination 18. Postembryonic Development: Metamorphosis, Regeneration, and Aging 19. The Saga of the Germ Line 20. An Overview of Plant Development 21. Medical Implications of Developmental Biology 22. Environmental Regulation of Animal Development 23. Developmental Mechanisms of Evolutionary Change…
is known as the embryonic stage the embryo gets its illustrated above rather then processed foods and…
• Primordial germ cells (46, 2N) migrate from the wall of the yolk sac and…
Primary (Neural) Induction The reaction which initiates both the formation of the CNS and causes the central longitudinal axis of the body to be established. Occurs shortly after gastrulation. Chordal cells induce overlying ectoderm to form neural plate. Inductor: Chordamesoderm Responding Tissue: Ectoderm Consideration: The inductor and inductee must be at the right place at the right time. The ectoderm must be competent to be induced…
A maternal to zygotic gene expression occurs due to the blastomeres receiving their mRNA from oocytes. The cell gene length begins to increase due to the gap phases increasing in length. The entire cell becomes more rounded, as the blastomeres begin to pile on top of each other. There is no clear plane for cleavage at this stage. In this phase, the embryo will arrive in midblastula transition phase. The plane of cleavage is no longer able to be identified, and no blastocoel is available. The Yolk Syncytial Layer (YSL), by the blastodisc interaction with the yolk, is formed around the 512-cell stage. When Squint, a nodal factor, is expressed due to high concentrations of β-catenin in the nuclei, the cells begin to associate with each other. This forms a fate prediction in the later stages of the blastula. After YSL begins to get larger, the cell begins to undergo epiboly which causes blastomeres closest to the margin to exhibit proteins like Squint, which, due to its ability to alter nodal concentrations, can aid in cell determination. The low concentrations of nodal induce the notochord formation, whereas higher concentrations induce prechordal plate formation.…
DSE is when a minimal proliferation of unorganized tissue precedes embryo formation while in ISE callus proliferates profusely before embryo formation. It has been suggested that in DSE, proembryogenic competent cells are already present and the expression of the embryogenetic program merely depends on favorable conditions. We believe that a minimal reprogramming is required for DSE expression, whereas in ISE a major cell reprogramming is necessary for de-differentiation to acquire the embryogenic. The main factors involved in each case depend on the nature and…
Gastrula – when cell begins to specialize to form an embryo the structure of the developing embryo.…