Questions and Answers
What is the function of the syncytiotrophoblast during implantation?
What is the main function of the corpus luteum during embryonic development?
What is the bilaminar disk composed of?
What is the role of hCG in embryonic development?
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What is the function of the prochordal plate?
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What is the function of progesterone during embryonic development?
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What is the primitive streak?
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What surrounds the bilaminar disk?
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What is the primary function of fibroblast growth factor 8 (FGF8) in gastrulation?
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What is the outcome of snail protein inhibiting E-cadherin formation?
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What is the purpose of the primitive groove?
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Which of the following is a characteristic of the mesoderm?
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What is the outcome of cells moving through the primitive groove?
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What is the role of the notochord in neuralation?
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What is the adult remnant of the notochord?
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What is the process by which cells migrate and move away from one another?
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Study Notes
Embryonic Development Week 1-2
- The previous video covered fertilization, cleavage, and the formation of the blastocyst.
- Now, we're discussing the development of the embryo up until week 2.
Trophoblast and Blastocyst
- The trophoblast is the outer cell layer of the blastocyst.
- The trophoblast differentiates into two layers: syncytiotrophoblast and cytotrophoblast.
- Syncytiotrophoblast is a syncytium of nuclei and cytoplasm without well-defined cell membranes.
- The cytotrophoblast has well-defined cell membranes with nuclei inside.
Implantation and Placenta Formation
- The blastocyst implants into the uterine lining through specific proteins (selectins and integrins).
- The syncytiotrophoblast releases hydrolytic enzymes, breaking down the uterine lining and creating a connection with maternal blood vessels.
- This connection forms the placenta, allowing for the exchange of oxygen, nutrients, and waste between the mother and fetus.
Hormones and Endometrial Lining
- The corpus luteum produces progesterone, which maintains the endometrial lining.
- The syncytiotrophoblast produces human chorionic gonadotropin (hCG), which stimulates the corpus luteum to continue producing progesterone.
- Progesterone prevents the shedding of the endometrial lining, allowing for implantation and development of the embryo.
Bilaminar Disk and Gastrulation
- The embryo blast forms a bilaminar disk with two layers: epiblast and hypoblast.
- The epiblast is the top layer, and the hypoblast is the bottom layer.
- The bilaminar disk is surrounded by the amniotic cavity above and the primitive yolk sac below.
Prochordal Plate and Primitive Streak Formation
- The prochordal plate is a thickened area of epiblast cells that provides orientation of cranial and caudal ends.
- Signaling processes cause epiblast cells to form a primitive streak, which is a thickened area of cells.
- The primitive node is a knob-like structure at the cranial end of the primitive streak.
Cell Migration and Gastrulation
- Cells in the center of the primitive streak and node die, creating a cavity.
- Nearby cells secrete fibroblast growth factor 8 (FGF8), which stimulates the migration of epiblast cells.
- FGF8 binds to receptors on epiblast cells, activating an intracellular process that forms snail protein.
- Snail protein inhibits the formation of E-cadherin, allowing cells to migrate and move away from one another.
- This process is called epithelial migration, which is crucial for gastrulation.### Primitive Streak and Groove Formation
- Thickening in the primitive streak creates a space called the primitive groove
- Primitive node becomes the primitive pit when a space forms within it
- EPI blast cells release fibroblast growth factor 8, causing them to move through the primitive groove
Gastrulation and Germ Layer Formation
- EPI blast cells move through the primitive groove, replacing the hypo blast and forming the endoderm
- More EPI blast cells move through the primitive groove, forming the mesoderm
- The three germ layers formed are: ectoderm, mesoderm, and endoderm
Germ Layer Characteristics
- Ectoderm: forms skin, nervous system, and related structures
- Mesoderm: differentiates into paraxial, intermediate, and lateral plate mesoderm, forming muscles, bones, connective tissue, and organs
- Endoderm: forms the lining of the GI tract, accessory organs, and glands
Notochord Formation
- Ectodermal cells move through the primitive pit, forming a tube-like structure called the notochord
- The notochord induces neuralation and becomes the adult remnant called the nucleus pulposus
Importance of Notochord
- Releases growth factors that cause thickening of the ectoderm, forming the neural plate and neural tube
- Becomes the adult remnant, nucleus pulposus, in the intervertebral discs
Embryonic Development Week 1-2
Trophoblast and Blastocyst
- The trophoblast is the outer cell layer of the blastocyst, which differentiates into syncytiotrophoblast and cytotrophoblast.
- Syncytiotrophoblast is a syncytium of nuclei and cytoplasm without well-defined cell membranes.
- Cytotrophoblast has well-defined cell membranes with nuclei inside.
Implantation and Placenta Formation
- The blastocyst implants into the uterine lining through specific proteins (selectins and integrins).
- Syncytiotrophoblast releases hydrolytic enzymes, breaking down the uterine lining and creating a connection with maternal blood vessels.
- This connection forms the placenta, allowing for the exchange of oxygen, nutrients, and waste between the mother and fetus.
Hormones and Endometrial Lining
- Corpus luteum produces progesterone, which maintains the endometrial lining.
- Syncytiotrophoblast produces human chorionic gonadotropin (hCG), which stimulates the corpus luteum to continue producing progesterone.
- Progesterone prevents the shedding of the endometrial lining, allowing for implantation and development of the embryo.
Bilaminar Disk and Gastrulation
- The embryo blast forms a bilaminar disk with two layers: epiblast and hypoblast.
- The bilaminar disk is surrounded by the amniotic cavity above and the primitive yolk sac below.
Prochordal Plate and Primitive Streak Formation
- The prochordal plate is a thickened area of epiblast cells that provides orientation of cranial and caudal ends.
- Signaling processes cause epiblast cells to form a primitive streak, which is a thickened area of cells.
- The primitive node is a knob-like structure at the cranial end of the primitive streak.
Cell Migration and Gastrulation
- Cells in the center of the primitive streak and node die, creating a cavity.
- Nearby cells secrete fibroblast growth factor 8 (FGF8), which stimulates the migration of epiblast cells.
- FGF8 binds to receptors on epiblast cells, activating an intracellular process that forms snail protein.
- Snail protein inhibits the formation of E-cadherin, allowing cells to migrate and move away from one another.
Primitive Streak and Groove Formation
- Thickening in the primitive streak creates a space called the primitive groove.
- Primitive node becomes the primitive pit when a space forms within it.
Gastrulation and Germ Layer Formation
- EPI blast cells move through the primitive groove, replacing the hypoblast and forming the endoderm.
- More EPI blast cells move through the primitive groove, forming the mesoderm.
- The three germ layers formed are: ectoderm, mesoderm, and endoderm.
Germ Layer Characteristics
- Ectoderm: forms skin, nervous system, and related structures.
- Mesoderm: differentiates into paraxial, intermediate, and lateral plate mesoderm, forming muscles, bones, connective tissue, and organs.
- Endoderm: forms the lining of the GI tract, accessory organs, and glands.
Notochord Formation
- Ectodermal cells move through the primitive pit, forming a tube-like structure called the notochord.
Importance of Notochord
- Releases growth factors that cause thickening of the ectoderm, forming the neural plate and neural tube.
- Becomes the adult remnant, nucleus pulposus, in the intervertebral discs.
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Description
Learn about embryonic development from week 1-2, covering the trophoblast and blastocyst formation, including syncytiotrophoblast and cytotrophoblast.
