Embryogensis and Development Flashcards
Ampulla
Widest region of fallopian tube where fertalization usually occurs
What are the wo major components of the ovum (outside of cellular membrane)?
- Zona Pellucida: acellular mixture of glycoproteins
- Aid in protection of ovum
- Aid in sperm binding
- Corona Radiata
- layer of cells that adhere to oocyte during ovulation
Explain process and major components of Fertilization.
- Sperm comes into contact with ovum (often in ampulla)
- Sperm Penetrates ovum with acrosomal enzymes
- Forms Acrosomal Apparatus with ovum membrane
- Tube-like structure that penetrates membrane (fusing with ovum membrane) so that pronucleus can be release into ovum for completion of meiosis II
- Cortical Reaction Occurs after penetration
- Fertlization Membrane is Produced
- Depolarized and impenetratable
Two main purposes of Cortical Reaction
Releases of calcium ions:
- Depolarizes the ovum membrane to prevent further fertilzation by additional sperm
- Increase metabolic rate of the newly formed zygote
Fertilization of two different eggs release during the same ovulatory cycle and fertilized by two different sperm. Each develop their own, chorion, amnion, and placenta.
Dizygotic (Fraternal) Twins
Single Zygote splits into two. Have same genetic material. Can share embryonic structures such as placenta, chorion, and amnion.
Monozygotic (Identical) twins
Three classifications of monozygotic twins.
- monochorionic/monoamniotic
- monochorionic/diamniotic
- Diamniotic/monochorionic
Four Major Processes that Occur after fertilization.
- Cleavage
- Blastulation
- Gastrulation
- Neurulation
Brief Summary of four processes that occur after fertilzation.
- Cleavage: Rapid mitotic division of the embryo forming a morula (with the first nulifying the unicellular defining character of a zygote)
- Blastulation: Blastula with Blastocoel is formed and comprised of inner cell mass and surrounding trophoblast. (known as a blastocyst in mammals). Implantation also occurs during blastulation.
- Gastrulation: Generation of three distinct cell layers forming a gastrula (with ectoderm, mesoderm, and endoderm)
- Neurulation: Development of the nervous sytem.
Important aspects of Cleavage
Purpose: Rapid Mitotic Division of New Embryo
- Cells Increase two ratios
- N:C
- SA:V
- Indetermine Cleavage vs. Determinite Cleavage
Process in which cells are capable of becoming any part of the body during cleavage.
Indeterminate Cleavage
Process by which cells are committed to differentiating into a specific cell during cleavage.
Determinate Cleavage
Solid mass of cells created by embryonic cleavage.
Morula
Important Aspects of Blastulation
- Blastula (hollow ball of cells) with Blastocoel (fluid -filled inner cavity)
- Two different cells types: Inner Cell Mass + Trophoblast
Part of the Blastula that becomes the placental structures.
Trophoblasts
After Implanation into the Endometrium, the trophoblasts begin development of the:
- Chorion: extraembryonic membrane that becomes placenta
- Chorionic Villi: finger-like projections (that also develop into placenta)
- Penetrate into endometrium and support maternal-fetal gas exhange
Consists and 2 arteries and 1 vein encased in a gelatinous substance and function as maternal-fetal blood exchange. Also connects placenta to developing embryo.
Placenta (Formed from yolk sac and allantois)
- Arteries: deoxygynated fetal blood and waste from embryo to placenta
- Vein: oxygynated blood from placenta to embryo
Site of early blood cell development (functions in place of placenta until it becomes fully functional)
Yolk Sac
Site of early fluid exchange between yolk sac and embryo
Allantois (together with yolk sac become the placenta)
Thin tough membrane filled with amniotic fluid that surrounds the allantois. “Shock absorber” during pregnancy.
Amnion
Be able to understand and analyze the major aspects of fetal develoment within this picture.
Important aspects of gastrulation.
- Formation of the Gastrula = Archenteron + Blastospore
- Archenteron: membrane invagination into blastocoel (gut)
- Blastospore: Opening of Archenteron (anus(in deuterosomes))
- Formation of Primary Germ Layers = Beginning of Differentiation
- Ectoderm
- Mesoderm
- Endoderm
“Atractoderm”
Ectoderm (what can make a person attractive)
-Skin, hair, nails, facial structures, and nervous systems
Oderm: Means to “get around”
Mesoderm
- Bones and muscles
- Circulatory System
“In-doderm” (Lining of Organs)
Endoderm
- Respiratory and Digestive Tract and accessory organs
Explain Process of Neurulation
- Rod of mesoderm cells form a notochord along axis of organism
- Notochord induces ectodermal cells to pinch inward to form neural fold
- Neurol groove forms as a result of the the ectoderm pinching inwards and eventually separating from surrounding neural fold to form neural tube
- Neural Tube, which becomes CNS, is surrounding by neural crest, which become PNS
- Ectoderm migrates over tube and crests to cover nervous system
Interfere with embryonic development and can cause defects or death.
Teratogens
Two subsequent mechanisms that result in cell specialization
- Determination
- Differentiation
Determination
Commitment of a Cell lineage, which is accomplished by:
- Uneven segregation of cellular material during mitosis
OR
- Morphogens: promote development down to a specific cell lineage
Changes a cell undergoes due to selective transcription to take on characteristics of a specific cell lineage.
Differentiation
Undifferentiated cells that give rise to other cells that will differentiate
stem cells
List and describe 3 different types of stem cells
- Totipotent (most potent): can differentiate into any cell (including placental structures or actual fetus)
- Pluripotent (gastrulation): can differientiate into all three germ layers and their derivatives, but not placental strucutures.
- Multipotent (least potent - most specialized): Can differientiate into multiple types of cells within a specific group
Determines how many different cell types a stem cell can become.
Potency
What are the roles of the inducer and responder in cell-to-cell communication?
Inducers promote differentiation by secreting a signal to induce another cell, which is the responder. Responder must be “competent,” or able to respond to inducing signal.
List the four types of cell to cell communcation.
1) Autocrine
2) Paracrine
3) Juxtacrine
4) Endocrine
(Also remember that signals often occur via gradients)
Type of cell-to-cell communication where signal that acts on the same cell the released the signal.
Autcrine
Type of cell-to-cell communication where signal on cells in local area.
Paracrine
Type of cell-to-cell communication where signal acts through direct stimulation of nearby cells.
Juxtocrine
Type of cell-to-cell communication where signal acts on distant tissues after traveling through bloodstream.
Endocrine
These are inducers made of proteins that promote differentiation and mitosis in certain tissues.
Growth factors (most of which only target/code for specific cells or tissue)
Reciprocal Induction
When two tissues induce further differentiation on the other (i.e. one induces a signal to an adjacent cell, which in return induces a signal on the initial cell).
Describe the Process of Apoptosis.
- Cell divides into many self-containing apoptotic blebs
- Blebs are ingested by other cells
(This method prevents waste/toxins from being released into extracellular environment because pieces are still within cellular membrane; Apoptosis can be important for sculting certain anatomical features, such as the webbing between digits.)
Process of cell death in which cell dies due to injury.
Necrosis
(Can be harmful to other cells due to release of toxic substances)
Regerative Capacity
Ability for Organism to regrow certain body partss.
Where gas, nutrient, and waste exchange occur in an embryo.
Placenta
Method by which nutrients and waste products are transfered from fetus to mother.
Diffusion (which requires a gradient)
Explain how oxygen, carbon dioxide, and waste are exchanged between fetus and mother.
Diffusion via a gradient
- Oxygen
- Mother has a higher partial pressure of oxygen than child
- Fetus has HbF, which has a higher affinity for O2 than maternal Hb
- HbF assists with transfer and retention of oxygen in fetal circulatory system
- CO2 and waste
- Mother has a higher affinity for transfer and retention of CO2 and waste products (opposite of HbF)
List the three major functions of the Placenta
- Waste, gas, and nutrient exchange
- Immune Protection (protects against pathogens and transfers antibodies to fetus)
- Endocrine Functions (secretes est. and prog. to allow pregnancy to continue)
List two organs that do not serve a purpose prior to birth.
1) Liver (detoxification and metabolism are primarily controlled by mother’s liver)
2) Lungs
List 3 shunts that block off blood flow to lungs and liver.
- Foramen Ovale
- Ductus Arteriosis
- Ductus Venous
Connects the right atrium to the left atrium, bypassing the lungs during fetal development.
Foramen Ovale
(Remember than during fetal development, pressure on the right side of the heart is greater than pressure in the left side of the heart, which reverses upon birth)
Connects the pulmonary artery to aorta, bypassing the lungs during fetal development.
Ductus arteriosis
Connects the umbilical vein to inferior vena cava, bypassing the liver during fetal development.
Ductus Venous
Major Milestones during First Trimester of Pregnancy.
Organogenesis
Major Milestones during Second Trimester of Pregnancy.
- Rapid Growth
- Face Becomes Distinct
- Digits Elongate
Major Milestones during First Third of Pregnancy.
- Rapid Growth
- Brain Development
- Transfer of Materna Antibodies to fetus
Parturition
Vaginal Birth
List events that occur during vaginal birth.
- Cervix thins out
- Amniotic Sac Ruptures
- Uterine Smooth Muscles Contract (coordinated by prostaglandins and peptide hormone oxytocin)
- Fetal Birth
- Afterbirth (placenta and umbilical cord)
