Biology: Chapter 4: Embryogenesis Flashcards
what is fertilization
joining of a sperm and an ovum
where does fertilization occur
ampulla of the fallopian tube
What happens when a sperm penetrates the ovum
an acrosomal apparatus appears and the sperm injects its pronucleus; calcium is released to prevent other sperm from fertilizing the egg (cortical reaction)
how do fraternal twins happen
result from the fertilization of two eggs by two different sperm
how do identical twins happen
splitting of the zygote into two
What happens after the first cleavage of the zygote
it becomes an embryo as it is no longer unicellular
What is an indeterminate cleavage
results in cells that are capable of becoming any cell in the organism
what is determinate cleavage
results in cells that are committed to differentiating into a specific type of cell
what is the morula
solid mass of cells seen in early development
what is the blastula (blastocyst)
has fluid filled center called a blastocoel with two different structures: trophoblast and inner cell mass
what are trophoblasts
cells in the blastula that become placental structures
what is the inner cell mass
cells in the blastula that becomes the organism
where does the blastula implant
the endometrial lining
what is the chorion
contains chorionic villi which penetrate the endometrium and create interface between maternal and fetal blood
what supports the embryo before the placenta forms
yolk sac
what is the allantois
involved in early fluid exchange between the embryo and the yolk sac
what is the amnion
lies inside the chorion and produces amniotic fluid
what happens during gastrulation
the archenteron is formed with a blastopore at the end; As the archenteron grows through the blastocoel it contacts the opposite side establishing three germ layers
what is the ectoderm
becomes the epidermis, hair, nails, the epithelial of the nose and mouth, anal canal, lens of the eye and the nervous system (adrenal medulla)
what is the mesoderm
becomes muscloskeletal, circulatory, excretory systems; gives rise to the gonads, muscular and connective tissue layers of digestive and respiratory systems and the adrenal cortex
what is the endoderm
becomes epithelial linings of the respiratory and digestive tracts; parts of the pancreas, thyroid, bladder, and distal urinary tracts
what happens during neurlation
the notocord induces a group of overlying ectodermal cells to form neural folds surrounding a neural groove; the folds fuse to form the neural tube; the tip of each neural fold contains neural crest cells
what does the neural tube become
CNS
what does the neural crest become
PNS
what are teratogens
substances that interfere with development causing defects or death
what is determination
commitment of the cell to a specific lineage
what are morphogens
promote development of specific cell line; cell must have competency to respond to morphogens
what is differentiation
refers to the changes of a cell due to selective transcription to take on appropriate characteristics of cell type
what are totipotent stem cells
able to differentiate into all cell types; including placental structures and germ layers
what are pluripotent stem cells
able to differentiate into all three of germ layers and their derivatives
what are multipotent stem cells
able to differentiate only into a specific subset of cell types
what is autocrine signaling
signals act on the same cell that released the signal
what is paracrine signaling
signals acts on local cells
what is juxtacrine signaling
signals act through direct stimulation of adjacent cells
what is endocrine signaling
signals act on distant tissues after traveling through circulatory system
what are growth factors
peptides that promote differentiation and mitosis in certain tissue
what is reciprocal induction
two tissues both induce further differentiation in each other
what is apoptosis
programmed cell death
what is necrosis
cell death as result of an injury
why is the placenta important
nutrient, gas, and waste exchange through concentration gradients
what is fetal hemoglobin
has a higher affinity for oxygen to assist the transfer and retention of oxygen into the fetal circulatory system
what is the placental barrier
serves as immune protection against pathogens and assists in antibody transfer
what hormones does the placenta excrete
estrogen, progesterone, and human chorionic gonadotropin
what are umbilical artieries
carries deoxygenated blood to the placenta from the fetus
what are umbilical veins
carries oxygenated blood from the placenta to the fetus
what is the importance of the foreman ovale
bypasses the lungs by connecting the right atrium to the left atrium
what is the importance of the ductus arteriosus
bypasses the lungs by connecting the pulmonary artery to the aorta
what is the importance of the ductus venous
bypasses the liver by connecting the umbilical vein to the inferior vena cava
what is happens during the first trimester
organogenesis occurs (heart, eyes, gonads, limbs, liver, some of the brain)
what happens during the second trimester
tremendous growth, movement begins, the face becomes human, and digits elongate
what happens during the third trimester
rapid growth and brain development; transfer of antibodies to the fetus
what happens during birth
1) cervix thins and amniotic sac ruptures
2) uterine contractions coordinated by prostaglandins and oxytocin
3) placenta and umbilical cord are expelled
