Embryogenesis and Development Flashcards
What is the ampulla?
the widest part of the fallopian tube where fertilization occurs
Describe the fertilization reaction
(1) Sperm meets the secondary oocyte in fallopian tube
(2) Binds and releases acrosomal enzymes which allow penetration of the corona radiata and zona pellucida
(3) Sperm comes into contact with cell membrane and forms acrosomal apparatus
(4) Cell membrane is penetrated and the sperms pronucleus enters the oocyte
(5) Depolarization due to fusion initiates a wave of calcium which initiates the cortical reaction
(6) Cortical granules open and cause a cortical reaction which depolarized the cell membrane
(7) This reaction lifts the vitalline layer away from the egg plasma membrane creating the fertilization envelope
What is the fast block to polyspermy?
When the sperm and egg membranes fuse together the egg plasma membrane is depolarized for a few seconds, blocking any other sperm
What is the slow block to polyspermy?
When the cortical reaction causes a lifting of the vitalline membrane and create the fertilization envelope
What is cleavage?
the step after fertilization where the zygote undergoes rapid mitotic cell divisions to form an embryo of the same size, just with more cells
What are the two types of cleavage?
Indeterminate - results in cells that can still develop into complete organisms and not a specific kind of cell
Determinate - cells whose fates are already decided and will develop in a specific kind of cell
What is a morula?
a solid ball of cells that is formed after several divisions of the embryo
What is a blastula?
a hollow ball of cells with a fluid filled inner cavity that is formed by blastulation, the step after cleavage
What is a blastocoel?
the inner fluid filled cavity of a blastula
What is a blastocyst?
the mammalian version of a blastula
What are trophoblast cells?
they surround the blastocoel and give rise to the chorion and later placenta
What is the inner cell mass?
mass of cells that is inside the blastocoel, surrounded by trophoblast cells, and will give rise to the organism itself
What is the chorion?
(1) surrounds the embryo and yolks sac, facilitates exchange of oxygen and CO2 between embryo and external environment
(2) extraembryonic membrane that develops into the placenta and arises from the trophoblastic cells
What are chorionic villi?
microscopic fingerlike projections that penetrate the endometrium and help develop the placenta and support gas exchange
How does the umbilical cord work?
It has one vein that carries freshly oxygenated blood from placenta to embryo and two arteries that carry unoxygenated blood and waste away
Name four extraembryonic membranes
chorion, yolk sac, allantois, amnion
What does the yolk sac do?
supports the embryo until the placenta is functional and site of early blood development
What does the allantois do?
(1) stores nitrogenous wastes produced by embryo and facilitates respiration in combination with chorion
(2) involved in early fluid exchange between embryo and yolk sac. Eventually becomes part of umbilical cord
What does the amnion do?
(1) surrounds the embryo in an aqueous environment to protect from mechanical shock and support hydration
What is gastrulation?
the generation of three distinct cell layers
How is a gastrula formed?
The circular cell will begin to fold into itself, with one side of the membrane getting closer to the opposite and will eventually form a horseshoe shape
(add pic here)
What is the archenteron?
This pathway that was formed by in the folding inward of the membrane of the blastula and will eventually form the gut
What is a blastopore?
It’s just the opening of the archenterion, or the entrance to the invagination or future gut
What does the blastopore develop into in deuterstomes?
the blastopore becomes the anus
What does the blastopore develop into in protostomes?
the blastopore becomes the mouth
Are human deuterostomes or protostomes?
deuterosomes (anus first)
What are the primary germ layers?
ectoderm, mesoderm, endoderm
What is the ectoderm?
The ectoderm is the outermost layer of the blastula. It gives rise to the outside layers like skin, hair, nails, lens of eye, nervous system and inner ear.
What is the mesoderm?
The mesoderm is the middle layer of the blastula. It gives rise to the musculoskeletal, circulatory, and most of the excretory systems, gonads and some connective tissue
What is the endoderm?
The endoderm is the innermost layer of the blastula and forms the epithelial linings of digestive and respiratory tracts, along with other organs like: pancreas, thyroid, bladder, urinary tracts and some liver.
Selective Transcription
only the genes that are needed for that particular which allows for differentiation
What is induction?
the ability of one group of cells to influence the differentiation of another group of cells through chemical messengers called inducers
What is neurulation?
the development of the nervous system
What is the notochord?
a rod of mesodermal cells that will go on to become the spine
Describe the process of neurulation?
(1) The notochord induces a group of overlying ectodermal cells to slide inward
(2) The ectodermal cells pushing inward cause the neural plate to buckle, forming a neural groove which is surrounded by peaks called neural folds
(3) The neural folds grow together until they form the neural tube which will give rise to the central nervous system
(4) Neural crest cells are found at the top of each neural fold and these give give to the PNS
(5) Ectodermal cells will migrate over the neural tube and enclose the whole thing
What is specfication?
The first step in cell specialization where the cell is reversibly designated as a specific cell type
What is determination?
The second step in cell specialization where the cell is irreversibly committed to a particular function in the future
What are morphogens?
specific molecules secreted by cells that can influence determination
What is differentiation?
the cell is undergoing a change in structure, function and biochemistry
What are cells called that can differentiate into any type of cell?
totipotent
What are cells called that can differentiate into any type of cell except those from the placenta/embryo?
pluripotent
What are cells called that can only differentiate within a certain group?
multipotent
What are the ways cell-cell communication can occur and describe them?
Autocrine - signals act on the cell same that secreted it; self acting
Paracrine - signals act on cells in the local area
Juxtacrine - signals must have physical contact with the cell
Endocrine - signals travel through the body in the bloodstream and work through hormones
What are growth factors?
peptides that promote differentiation and mitosis in certain tissues
What is biological aging called?
senescence
What is thought to be a cause of aging?
research shows that shortening of telomeres on chromosomes after multiple rounds of mitosis will lead to unraveling of important DNA and therefore aging and death
Describe fetal hemoglobin
HbF has a higher affinity for oxygen than regular adult hemoglobin which helps it get oxygen to the fetus and keep it in the fetal circulatory system
Umbilical arteries vs umbilical veins
Arteries carry deoxygenated blood away from the fetus toward the placenta; veins carry oxygenated blood toward the fetus from the placenta which was oxygenated there
How do adult and fetal circulation differ?
The fetal lungs and liver are not used during fetal development. All gas exchange happens through the placenta and the mother’s liver is largely in charge of detoxification, as well as partly the placenta too.
What are the three fetal shunts?
(1) Foramen ovale
(2) Ductus arteriosus
(3) Ductus venosus
What does the foramen ovale do?
(1) Foramen ovale - a one way valve that connects the [right atrium to the left] and bypass the right ventricle and stay out of the lungs
What does the ductus arteriosus do?
(2) Ductus arteriosus - moves leftover blood from the [pulmonary artery to the aorta] and puts blood straight into circulation without the lungs
What does the ductus venosus do?
(3) Ductus venosus - bypasses the liver by moving blood directly from the [placenta to inferior vena cava]
What happens in the first trimester of pregnancy?
Heart beats at around 22 days, major organs like eyes, gonads, limbs and liver start to form, skeleton forms into bone, brain is kind of developed and it is now known as a fetus
What happens in the second trimester of pregnancy?
Grows a lot and begins to move around, face looks human and toes and fingers elongate
What happens in the third trimester of pregnancy?
Rapid growth and brain development, antibodies are shared from mother to fetus
How long is a human pregnancy? (in days)
around 280 days
What is vaginal childbirth called?
parturition
What hormone helps induce vaginal contractions?
oxytocin
What are the three phases of birth?
(1) Cervix thins out and amniotic sac ruptures (water breaking)
(2) Strong contractions push the fetus out
(3) The placenta and umbilical cord are expelled
