Ch. 3: Embryogenesis and Development Flashcards
What occurs during fertilization?
occurs in the widest part of the fallopian tube – ampulla
sperm binds to secondary oocyte and release acrosomal enzymes that allow the head of the sperm to penetrate the corona radiata and zona pellucida
there is a release of calcium ions which prevents additional sperm from fertilizing the egg and increases the metabolic rate of the zygote – cortical reaction
What is the difference between fraternal/dizygotic twins and identical/monozygotic twins?
fraternal twins are a result of ferilization of two different eggs by two difference sperm
identical twins result from splitting a zygote in two
What is cleavage?
early division of cells in the embryo
after the first cleavage, the zygote becomes an embryo as it is no longer unicellular
indeterminate cleavage - cells that may become any organism
determinate cleavage - cells that are committed to a specific differentiation
What is the morula?
solid mass of cells seen in early development
What is a bastula?
morula undergoes blastulation
hollow ball of cells with a fluid filled inner cavity
trophoblast cells give rise to the placenta (on the outside)
inner mass cells give rise to the organism itself
What occurs during implantation?
the blastula burrows into the endometrium in the uterus
trophoblastic cells give rise to the chorion, an extraembryonic membrane which turns into the placenta and there are chorionic vila that are small projections taht penetrate the endometrium
What does the umbilical cord consist of?
two arteries and one vein encased in gelatinous substance
What is the yolk sac?
supports embryo before the placenta is functional and is the site of early blood cell development
What is the allantois?
membrane that is involved in early fluid exchange between the embryo and the yolk sac
What is the amnion?
surrounds the allantois
thin, tough membrane filled with amniotic fluid and acts as a shock absorber for the embryo
What is gastrulation?
generation of three distint cell layers
the archenteron is formed with a blastopore and three primary germ layers are formed
Germ layer
What is the ectoderm?
“attracto” (things that attract us to others)
outermost layer that gives rise to epidermis, hair, nails and epithelia of many things, lens of eye, nervous system
Germ layer
What is the mesoderm?
“means” (the means of getting around)
muscles, bones, circulatory system, gonads, connective tissue layers of digestive and respiratory systems
Germ layer
What is the endoderm?
linings of “endermal” (inner) organs
forms linings of digestive and repiratory tracts as well as many organs attached to these systems
Where is the adrenal cortex derived from?
mesoderm
Where is the adrenal medulla derived from?
ectoderm (contians some nervous tissue
Explain nerulation.
development of the nervous system after the germ layers are formed
1. rod of mesodermal cells - notochord - forms
2. induces group of overlying ectodermal vells to slide in to form neural folds that surround a neural groove
3. neural folds grow toward each other until fusing into neural tube
4. neural tube gives rise to CNS with the tip of each neural fold (neural crest cells) becomeing the peripheral nervous system
What are teratogens?
substances that interfere with embryo development
Ex. alcohol, drugs, viruses, bacteria, environmental chemicals
What is specification?
first stage of cell specilization
cell is reversibly designated as a specific cell type
What is determination?
cell commits to a particular function
may be cause by asymmetric distribution of mRNA and proteins during cleavage or due to secretion of specific molecules from nearby cells (morphogens - molecules that cause cells to follow a particular developmental pathway)
What is differentiation?
stem cells change their structure, function, and biochemistry ot match a cell type
What are totipotent cells?
greatest potency
differentiate into any cell type
What are pluripotent cells?
cells can differentiate into any cell type except for hose found in placental structures
What are multipotent cells?
cells that can differntiate into multiple types of cells within a particular group
Explain the types of cell-cell communication.
- autocrine signals - act on the same cell that secreted the signal
- paracrine signals - act on cells in local area
- juxtacrine signals - cell directly stimulating receptors of an adjacent cell
- endocrine signals - secred hormones that travel through the bloodsream to a distant target
Responder - cell that is induced (responsive cell)
Competent - responder must be able to respond to inducing signal
What is reciprocal induction?
two tissues both induce further differentiation in each other
Explain the umbilical arterties and the umbilical vein.
the umbilical arteries carry deoxygenated blood with waste products away from the fetus to the placenta
the umbilical vein carries oxygenated blood with utrients toward the fetus from the placenta
How does fetal hemoglobin (HbF) differ from adult hemoglobin (HbA)?
HbF has a higher affinity for oxygen that helps transfer and retain oxygen in the fetal circulatory system
Explain some functions of the placenta.
- forms a barrier for immune protection against pathogens
- secretes estrogen, progesterone, and human chorionic gonadotropin (hCG)
Explain the three shunts in the fetal circulatory system.
- foramen ovale - connects the right atrium to the left atrium (no lungs)
- ductus arteriosus - connects pulmonary artery to the aorta (no lungs)
- ductus venosus - connects umbilical vein to the inferioir vena cava (no liver)
What happens in the first trimester?
organogenesis occurs
hear, eyes, gonads, limbs, liver, brain
What happens in the second trimester?
growth occurs, movement begins, face becomes human, digits elongate
What happens in the third trimester?
rapid growth and brain development, transfer of antibodies to fetus
What happens during birth?
- cervix thins
- amniotic sac ruptures
- uterine contractions due to prostaglandins and oxytocin
- birht of fetus
- placenta and umbilical cord are expelled
