Embryogenesis & Development Flashcards
Fertilization
Penetration of the sperm through the cell membrane of an oocyte causes a cortical reaction - release of Ca2+ which depolrizes the membrane of the ovum preventing fertilization of the ovum by multiple sperms and increase metabolic rate of the new formed diploid zygote
Ampulla
Widest part of the fallopian tube where fertilization occurs
Dizygotic Twins
Fraternal twins (2 eggs with 2 different sperm)
Monozygotic Twins
Identical twins (1 zygote splits into 2)
Cleavage
- Zygote undergoes rapid mitotic cell divisions by dividing into progressively smaller cells
- Nuclear to cytoplasmic ratio increases
- Surface area to volume ratio increases allowing for increased gas exchange
Steps of Egg Growth
- Zygote (immediately after fertilization)
- 2 cells
- 4 cells
- 8 cells
- 16 cells
- Morula (solid mass of cells)
- Blastula (hollow ball of cells)
- Gastrula (multiple layers of cells)
Blastulation
Moving from Morula (solid mass of cells) to Blastula (hollow ball of cells)
Gastrulation
Moving from Blastula (hollow ball of cells) to Gastrula (multiple layers of cells)
- Generation of 3 distinct layers (endoderm, ectoderm and mesoderm) once the cell mass implants
Blastula
Moves into the uterus and burrous into the endometrium
Inner Cell Mass
Part of the Blastula:
Inner cells that give rise to the organism itself
Trophoblast
Part of the Blastula:
Outer cells that give rise to chorion and later to the placenta
Chorion
Extraembryonic membrane that develops into the placenta
Chorionic Villi
Fingerlike projections that penetrate the endometrium and support maternal fetal gas exchange
Fetus to Placenta Blood Exchange
Two arteries carry away deoxygenated blood and waste
Placenta to Fetus Blood Exchange
One Vein carries oxygenated blood and nutrients in
Umbilical Cord
Connects embryo to placenta
Yolk Sac
Early blood cell development; Embryo is supported by this before the placenta; later becomes the umbilical cord
Allantois
Extraembryonic membrane for early fluid exchange
Amnion
Extraembryonic membrane for amniotic fluid; shock absorber
Archenteron
Formed from gastrulation and later develops into the gut
Blastopore
Opening of the archenteron which later becomes the anus
Germ Layers
- Endoderm
- Ectoderm
- Mesoderm
- Archenteron (Blastopore)
Endoderm
“Endernal Organs”
Innermost layer which gives rise to epithelial linings
- Lining of digestive tract
- Pancreas
- Liver
- Lung
- Thyroid
- Bladder
- Urethra
Ectoderm
“Attract Oderm”
Outermost layer which gives rise to the integument system
- Skin (Epidermis)
- Eyes
- Nervous System
- Ears
- Pituitary Gland
Mesoderm
Middle layer giving rise to several different systems
- Bone Marrow
- Skeletal muscle
- Smooth muscle
- Cardiac muscle
- Heart
- Blood vessels
- Kidney Tubules
Differentiation
Selective transcription of the genome
Implantation
Embryo implants in uterus during blastula stage
Neurulation
Germ layers develop a nervous system
Induction
Part of Differentiation:
Ability of one group of cells to influence the fate of other nearby cells
Inducers
Part of Differentiation:
Mediate induction - chemicals which diffuse from the organizing cells (responsive cells)
Notochord
Mesodermal cells form along the axis of the organism
Neural Folds
Overlying ectodermal cells slide inward from the notochord surrounding the neural groove
Neural Tube
Fuse neural folds grow toward one another giving rise to the central nervous system
Neural Crest Cells
At the tip of each neural fold, gives rise to peripheral nervous system
Teratogens
Substances that interfere with development
- Alcohol
- RX Drugs
- Viruses
- Bacteria
- Environmental Chemicals
- Maternal Health
Determination
Commitment of cell to having a particular function in the future
Differentiation
Cell assumes structure, function and biochemistry of that cell type
Stem Cells
Give rise to cells that will differentiate but have not yet done so
Totipotent
Greatest potency, can differentiate into any cell type, either in the fetus or placental structures
Pluripotent
Cells can differentiate to any cell type EXCEPT placental structures
Multipotent
Cells can differentiate into multiple types of cells in a particular group
Responder
Cell that is induced - must be competent and able to respond to signal
Autocrine
Signal acts on the same cell that created the signal
Paracrine
Signal acts on cells in the local area
Juxtacrine
Signals feature a cell directly stimulating receptors of the adjacent cell
Exocrine
Secrete hormones that travel through blood to distant target tissues
Inducer
Commonly growth factors - peptides that promote differentiation and mitosis in certain tissues
Cell Migration
Cell must be able to disconnect from adjacent structures and migrate to their anatomically correct location
Apoptosis
Programmed cell death via apoptotic signals or pre-programming
Necrosis
Cell death in which the cell dies as a result of injury
Apoptotic Blebs
- Self contained pieces remaining after the cell undergoes changes in morphology and divides
- These can be digested by other cells to recycle materials
Regeneration
Ability of an organism to regrow certain parts of the body
Complete - lost / damaged tissues is replaced with identical tissues
Incomplete - Newly formed tissue is NOT identical in structure or function to the tissue it is replacing
Senescence
Biological aging - at cellular level the cells fail to divide, telomeres (ends of chromosomes) begin to shorten
Telomerase
Enzyme preventing senescence and controls cell division
Fetal Circulation
- Fetal and maternal blood do not mix
- Diffusion moves nutrients and waste
- Higher partial O2 in maternal blood
- Fetal Hemoglobin (HbF) have a higher affinity for O2
Placental Barrier
Serves immune protection, allows for the crossing of antibodies, gas, nutrients and waste exchange
Shunts
Direct blood away from organs not in use like the lungs or the liver in the fetus
Foramen Ovale
One way valve connects right and left atrium in the heart in fetuses
Ductus Arteriosus
Shunts leftover blood from pulmonary artery to the aorta in fetuses
Ductus Venosus
Shunts blood returning from placenta to the inferior vena cava in fetuses
First Trimester (Fetus)
- Major organs begin to develop
- Brain is fairly developed
- Heart begins to beat
- Cartilaginous skeleton begins to harden
Second Trimester
- Growth
- Movement begins
- Appearance becomes more human; toes and finger elongate
Third Trimester
- Growth
- Brain development
- Antibodies transported from mother to fetus
- Less active (less room to move)
Steps of Birth
- Cervix thins out and amniotic sac ruptures (water-breaking)
- Strong uterine rhythmic contractions of smooth muscle coordinated by prostaglandins and oxytocin
- Birth of child
- Placental and umbilical cord are expelled (after-birth)
