Development and Embrogenesis Flashcards
Ampulla
Widest part of the fallopian tube where fertilization occurs
acrosomal apparatus
-when sperm comes into direct contact with secondary oocyte, it forms a tubelike structure (acrosomal apparatus) that extends to and penetrates the cell membrane
Cortical reaction
- after penetration of the sperm through the cell membrane, a release of calcium ions occurs
- release of calcium depolarizes the ovum membrane
1. depolarization prevents ovum fertilization by more than one sperm
2. `depolarization increases metabolic rate of newly formed diploid zygote
fertilization membrane
-depolarized impenetrable membrane
Dizygotic of Fraternal Twins
formed by the release of two eggs during one ovulatory cycle
- two eggs fertilized by different sperm
- no more genetically similar than any siblings
Monozygotic or Identical twins
- form when a single zygote splits into two
- all genetic material identical
- if splitting is incomplete, conjoined twins
After fertilization in fallopian tube
zygote travels from fallopian tube to uterus for implantation
Cleavage
- the rapid mitotic devisions the zygote experiences while moving to the uterus
- creates embryo (no longer unicellular)
Indeterminate cleavage
- results in cells whose function has yet to be determined
- can still develop into complete organisms
- monozygotic (identical twins) formed from indeterminate cleavage of the same embryo
determinate cleavage
- results in cells whose functions are already determined
- these cells are committed to differentiating into a certain type of cell
morula
a solid mass of embryonic cells formed after several divisions
blastula
morula undergoes blastulation which forms a hollow ball of cells
-an embryo with a blasted out cavity is known as a blastula
blastocoel
the fluid filled cavity of a blastula
blastocyte
mammalian blastocoel
trophoblast
outer cells of blastocyte
-specialized to create an interface between maternal blood supply and the developing embryo (placental cells)
inner cell mass
protrudes into the blastocoel and gives rise to the organism
umbilical cord
connects embryo to the placenta
chorion
- formed by the trophoblastic cells
- extraembryonic membrane that develops into the placenta
chorionic villi
- formed by the trophoblasts
- microscopic finger like projections that penetrate the endometrium
- as they develop into placenta, they support maternal-fetal gas exchange
yolk sac
- used to support embryo until the placenta is functional
- site of early blood cell development
allantois
- involved in early fluid exchange between the embryo and the yolk sac
- umbilical cord formed from remnants of yolk sac and allantois
amnion
- thin, rough membrane that surrounds the allantois
- filled with amniotic fluid
- acts as cushion to weaken impact of maternal movement on embryo
gastrulation
the generation of three distinct cell layers
-after implantation
gastrula
structure after gastrulation
archenteron
the membrane invagination into the blastocoel
-later develops into the gut
blastopore
the opening of the archenteron
Deuterostomes
- humans
- blastopore develops into anus
protostomes
-blastopore develops into the mouth
primary germ layers
ectoderm, mesoderm, endoderm
ectoderm
- outermost layer
- forms nervous system
- “attracto” derm= things that attract
mesoderm
- middle layer
- develops into several different systems including the musculoskeletal, circulatory and most excretory systems
- “means” oderm- getting around in the body
endoderm
- innermost layer
- forms linings of digestive and respiratory tracts, the pancreas, thyroid, bladder and urinary tracts
selective transcription
-the transcription of of only the genes needed for the particular cell type
induction
-the ability of one group of cells to influence the fate of other nearby cells
neurulation
development of the nervous system
- occurs after the three germ layers are formed
- form from the ectoderm
notochord
- a rod of mesodermal cells forms this
- acts as a primitive spine
- induces a group of overlying ectoderm cells to slide inward forming neural folds
neural tube
neural folds grow towards one another until they fuse into a neural tube
-gives rise to central nervous system
Neural crest
cells at the tip of each neural fold are the neural crest cells
-these cells migrate outward to form the peripheral nervous system and specific cell tissues
morphogens
molecules secreted from cells that may cause nearby cells to follow a particular developmental pathway
differentiation
the changing of structure, function and biochemistry of a cell to match the determined cell type
Determination
commitment of a cell to have a particular function in the future
stem cells
-cells that have not yet differentiated or which give rise to other cells that will differentiate are known as stem cells
totipotent stem cells
- include embryonic stem cells
- stem cells of greatest potency, can differentiate into any cell type
pluripotent stem cells
- stem cells immediately after the formation of the three germ cell layers
- can differentiate into any cell other than those found in the placenta
multipotent stem cells
stem cells found in more specialized cells
-can differentiate into any cell within a particular group
autocrine signals
act on the same cell that secreted the signal
paracrine signals
act on cells in local area
juxtacrine signals
a cell directly stimulates the receptors of the adjacent cell
endocrine signals
involve secreted hormones that travel through the bloodstream to a distant target tissue
apoptotic blebs
- during apoptosis the cell undergoes changes in morphology and divides into many self contained pieces
- can be digested by other cells
Necrosis
Cell dies as a result of injury
Senescense
Biological aging
telomeresthe ends of chromosomes
- prevent lost of genetic information from ends of DNA
- prevent DNA from unraveling
- as cell replicates telomeres get smaller
fetal hemoglobin(HbF)
contained in the blood of a fetus
-higher affinity for oxygen than does adult hemoglobin
umbilical artery
carries blood away from the fetus toward the placenta
-carries deoxygenated blood
umbilical vein carries blood
toward the fetus from the placenta
-carries oxygenated blood
Fetal shunts
used to direct blood away from the liver and lungs of the fetus so that they can continue to develop for birth
foramen ovale
one way valve in fetus that connects the right atrium to the left atrium
- one of three shunts
- bypasses lungs
ductus arteriosus
shunts leftover blood from the pulmonary artery to the aorta
-bypasses lungs
ductus venosus
shunts blood returning from the placenta via the umbilical vein directly to the inferior vena cava
-bypasses liver
first trimester
First few weeks, the major organs begin to develop
- heart beats after 22 days
- eyes, gonads, limbs and the liver start to form
- bone starts to form by seventh week
- by the end of the eighth week the embryo is known as a fetus
second trimester
- rapid growth
- fetus begins to move in amniotic fluid, toes and fingers elongate
- face looks human
third trimester
- rapid growth and brain development
- antibodies from mother are transported in preparation for life outside the womb
Three phases of birth
1) cervix thins and the amniotic sac ruptures
2) strong uterine contractions result in the birth of the fetus
3) placenta and umbilical cord are expelled (afterbirth)
