Human Development Flashcards
What is the zone pellucide?
-Plasma membrane of the egg.
-This layer is surrounded by a follicle cell layer called the corona radiate (source of nutrients.
What is a zygote?
-The resulting single cell produced by fertilization.
-1-16
What is a morula?
-Once the zygote reaches 16 cells.
-Begins to fill with fluid.
-Reaches uterus 3-5 days after fertilization.
What is cleavage?
-Process of cell division without cell enlargement/growth.
What is a blastocyst?
-Mass of cells with a hollow core.
-Embryoblast develops into the embryo.
-Trophoblast forms the outer layer and will develop into the chorion. (Which will turn into the placenta).
-Implants to endometrium between day 5-7.
-Trophoblast secrets enzymes that digest the endometrium and the blastocyst sinks into layer.
-Complete by day 10-14.
What is human chorionic gonadotropin (hCG)?
-Hormone that maintains the corpus luteum.
-Secreted by trophoblast (chorion later).
-Secretion of estrogen and progesterone is maintained (endometrium layer is maintained.)
-Function is later replaced by the placenta.
What is the amniotic cavity?
-Space formed between the inner cell mass and the trophoblast.
Describe the embryonic disk
-Inner cell mass (embryoblast) flattens to form the embryonic disk (structure that contains the germ layers).
-Gastrulation: embryonic disk forms into three layers:
-Ectoderm: Nervous system, epidermis (skin,hair).
-Mesoderm: Skeleton, muscles, reproduction system.
-Endoderm: lining of the digestive and respiratory systems, endocrine glands.
-Embryo is now a gastrula.
What is neurolation?
-Forming of the tube that will develop into the brain and spinal cord.
What does the development of the organs and organ systems from the 3 embryonic layers involve?
-Growth: cell division.
-Morphogenesis: development of body form and structure.
-Differentiation: enables cells to develop particular shape and function.
What are extra-embryonic membranes?
-Structures that support the embryo.
-Allantois: forms the umbilical cord.
-Amnion: fills with fluid (amniotic fluid) to protect embryo from trauma, temp changes, and freedom of movement.
-Chorion: outermost membrane and forms fetal part of placenta.
-Yolk sac: produces first blood cells and contributes formation to digestive tract.
Describe the placenta
-Where metabolic (nutrients/waste) exchange happens.
-Fully developed by 10 weeks.
-Acts as a barrier between the two blood supplies.
-Does not filter drugs, alcohol, and nicotine (teratogens).
-Secrets estrogen, progesterone and hCG.
-Membrane exchange for O2, H2O, vitamins/minerals, antibodies, hormones, etc between fetal blood and maternal blood.
When is the embryo most likely to develop abnormalities as a result of teratogens?
-Between the 4th and 8th week of the first trimester. (When development of organ systems occurs).
What are major developments of the first trimester (weeks 1-12, first 3 months).
-Development of organ systems.
-Nervous system develops.
-Eye starts.
-Fetus is 9 weeks to birth.
What are major developments of the second trimester? (Weeks 13-14, second 3 months).
-Everything is now working.
-Brain starts to direct motor activity (less reflex).
-Develops awareness of environment.
-Digestive system becomes active but not used.
-testosterone and eggs start to be made.
-Hands, legs, fingerprints.
What are major developments of the third trimester? (Weeks 25-38, last 3 months)
-Growth and putting on fat.
-Doubles in size, triples in mass.
-Senses develop.
-Brain starts to create memory.
-Lungs are last of organs to develop.
-Digestive system and respiratory system.
What is artificial insemination?
-One of the technologies used to enhance reproductive potential (usually first option).
-Sperm are deposited into the uterus.
-Other examples include surrogacy, superovulation, hormone therapy, embryo transfer, etc.
-Doesn’t work if women has heavy STIs or scar tissue in fallopian tubes.
What is vetro fertilization?
-Usually second option for technologies that enhance reproductive potential.
-Immature eggs are retrieved from follicles.
-Eggs are combined with sperm in glassware.
-Developing embryo(s) are inserted into the uterus or oviduct.
What do identical twins happen?
-A single zygote splits into 2 early into development, and since both embryos come from the same zygote they share the same genetic info, and are identical.
