Embryogenesis and Development Flashcards
Ampulla
widest part of fallopian tube where fertilization occurs
When sperm meets the ______ in the fallopian tube, it binds to the ____ and releases _____ that allows the head of the sperm to penetrate through the corona radiata and zona pelucida.
secondary oocyte ; oocyte; acrosomal enzymes
Acrosomal Apparatus
penetrates cell membrane when sperm meets secondary oocyte
Cortical Reaction
once sperm penetrates secondary oocyte, a release of calcium ions depolarizes membrane to prevent other sperm from penetrating and increase metabolic rate of zygote.
Fertilization Membrane
cellular membrane of zygote once depolarization occurs
Dizygotic/Fraternal Twins
Fertilization of two eggs by 2 different sperm ; no more genetically similar than any other sibling pairs
Monozygotic/Identical Twins
single zygote splits in two and since genome is same, they are identical
Monochorionic/Monoamniotic Twins or Dichorionic/Diamniotic twins occur based on when seperation occurs
as more gestational structures are shared, more risks for fetus to develop
Conjoined Twins
if division of zygote is incomplete and two offspring end up attached
Monochorionic/Monoamniotic Twins
they are monozygotic twins which share the same amnion and chorions
Dichorionic/Diamniotic Twins
they are monozygotic twins which have their own amnion and chorions
After fertilization in the fallopian tubes, zygote travels to the _____ for implantation.
uterus
Cleavage
rapid mitotic cell divisions zygote undergoes when moving to uterus
divides into small cells to increase the SA:V and nuclear:cytoplasmic ratio for gas/nutrient exchange
The first cleavage produces ___
embryo
Indeterminate Cleavage
cells that can develop into complete organisms ; monozygotic twins
Determinate Cleavage
cells that are comitted to differentiate into different cells
Morula
solid mass of cells that arrive from multiple divisions of the embryo
Blastulation
when morula forms the blastula
Blastula/Blastocyst
hollow ball of cells from morula that contains fluid filled inner cavity known as a bastocoel
made of trophoblast and inner cell mass
Trophoblast Cells
surround the blastocoel (fluid filled cavity) of blastula and give rise to chorion/placenta
interface between embryo and maternal blood supply
Inner Cell Mass
cells that prutruve into the blastocoel and rise into the organism itself
Blastula moves through the fallopian tube to the uterus and burrows into the _____
endometrium
Sequence of Cell Masses
Zygote -> Embryo -> Morula -> Blastula
Chorion
risen from trophoblast cells which are a extraembryonic membrane that develops into placenta
Chorionic Villi
finger like projections made by the trophoblast cells that develop into the placenta for gas exchange
Umbilical Cord
embryo connected to placenta via this ; comes from remnants of yolk sac and allantosis
2 arteries and a vein where vein brings in oxygenated blood/nutrients, the artieris carry waste
Yolk Sac
supports embryo until placenta is functional and where blood cell development occurs
Allantosis
extraembryonic membrane that does early fluid exchange between yolk sac and embryo
Amnion
surrounds allantosis as a shock absorbing membrane
Gastrulation
generation of three distinct cell layers from cell mass implantation
Archenteron
membrane invagination into the blastocoel, becomes the gut
Blastopore
opening of the archenteron
In deuterostomes, such as humans, the blastopore develops into the _____ , in protostomes, it develops into the _____
anus; mouth
The Primary Germ Layers
Ectoderm
Mesoderm
Endoderm
Ectoderm
a primary germ layer, outermost later giving rise to the integyment
epidermis, hair, nails and nervous system/inner ear
Mesoderm
primary germ layer, develops in musculoskeletal, circulatory and excretory systems
Gonads, muscular and connective tissue layers of the digestive and respiratory systems and the adrenal cortex
Endoderm
primary germ layer, inner most layer
epithelial linings of the digestive and respiratory tracts including the lungs
Pancreas, thyroid, bladder, distal urinary tracts and liver
Selective Transcription of Genome
how cells with the same genes are able to develop into different cell types
Induction
ability of surrounding cells influence he fate of other nearby cells
Inducers
chemicals which diffuse from organizing cells to responsive cells
Neurolation
development of the nervous system occurs once the three germ layers are formed ; comes from ectoderm
Steps of Nervous System Development
1) Notochord forms like spinal cord
2) Notochord induces ectodermal cells to form neural folds around neural groove
3) Neural folds fuse into neural tube to rise CNS
4) Neural crest cells at the tip of the folds migrate out to form PNS and tissues (calcitonin thyroid,, malanocytes in skin)
5) Ectodermal cells will migrate to the neural tube and cover the rudimentary nervous system
Organogenesis
development of organs
Teratogens
substances which interfere with development and can lead to defects/death of the developing embryo
Each teratogen has/does not have the same effect on every embryo/fetus, ______ of the individual embryo influences the effects of the teratogen along with…
does not
genetics
route/length of exposure, rate of placental transmission, identity of teratogen
Common Teratogens
alcohol, prescription drugs, viruses, bacteria, and enviornmental chemicals
Maternal health can/cannot influence health of embryo. Some examples are ____
can
hyperglycemic mothers resulting in large babies with hypoglecemia due to too much insulin production
Folic deficient mothers can prevent neural tube closure leading to anacephaly
Determination
commitment of a cell to having a particular function later
2 Ways Determination can Occur
1) mRNA and protein in parent cell is asymmetrically distributed between daughter cells so presence of mRNA determines which cell is produced
2) May occur due to secretion of specific molecules nearby
Morphogens
cause nearby cells to follow a particular developmental pathway
REMEMBER! Determination is a commitment to a specific cell type, but has not produced the ____ it needs to carry out the functions of the cell- that is the goal of _____
products, differentiation
Differentiation
cell undertakes changes in structure/function/biochemistry to match the cell type it is to become.
Stem Cells
cells that have not yet differentiated, foundin embryo and certain areas of adult tissue
Potency
the tissues a particular stem cell can differentiate into
Totipotent
stem cells which can ultimately differentiate into any type of cell, found in embryo or in placental structures
Pluripotent
cells can differentiate into any cell type except those in the placenta
Multipotent
cells can differentiate into multiple types of cells within a particular group
Concerns of stem cell use
- ethics of killing embryo
- immunologic concerns
- can become cancerous
Pros and Cons of Adult Stem cell Usage
Pros:
- no worries of immunologic concerns as cells are transplanted back
- no ethics
Cons:
- limited potency
Determination and differentiation of a cell depends on the _____ of the cell itself as well as the identity of the _____
location; surrounding cells
Responder
cell that is induced, the responsive cell
To be induced, a responder must be ____ , or be able to respond to the inducing signal.
competent
Cell-cell communication can occur viz _______ signals
Autocrine, Paracrine, Juxtacrine and Endocrine
Autocrine
signals act on same cell that secreted the signal
Paracrine
signals act on cells in the local area
Juxtacrine
no diffusion, but feature a cell directly stimulating receptors to an adjacent cell
Endocrine
secreted hormones that travel through blood stream to distant target tissue
Growth Factos
inducers which are peptides to promote differentiation/mitosis in certain tissues
growth factors can code for particular tissues
Reciprocal Development
the responding cells induce signals back to the signaling cells to respond (example forming of lens can cause signaling to then form retina)
Cell Migration
cells must move to their proper location to function
ex: neural crest cells must migrate throughout the body to form the PNS structures like gnaglia
Apoptosis
programmed cell death to form structures
Apoptotic Blebs
cell divides into small pieces which can be digested by other cells to recycle materials
membrane bound so harmful substances are not released into the enviornment
Necrosis
cell death due to injury which leads to harmful substances leaking leading to an immune response
Regenerative Capacity
ability of an organism to regrow certain parts of the body
stem cells migrate to initiate refrowth
Complete vs Incomplete Regeneration
C: lost or damaged tissue is replaced with identical tissue
I: new formed tissue is not identical in structure/function to the injured tissue (Humans)
In humans, regenerative capacity varies by ______
tissue type; liver is high, heart is very low, kidney is middle
Senescence
biological againg where molecular and cellular structures begin changing and can lead od eventual failure of cells to divide
Telomeres
ends of chromosomes that reduce the loss of genetic info from the ends of chromosomes and help prevent the DNA from unraveling
high concentration of guanine and cytosine knots off the end of the chromosome
difficult to replicate and shorten during DNA synthesis
Reason for senescence is due to _____ shortening
telomere
Telomerase
reverse transcriptase that is able to synthesize ends of chromosomes to prevent senescence
present in germ, fetal and tumor cells
Placenta
organ where nutrient, gas and waste exchange occurs
It is crucial that maternal and fetal blood do not mix because____ hence ____ is preferred method of nutrient transfer
different blood types; diffusion
Diffusion requires a gradient, so this implies there is higher _______ in maternal blood than fetal blood
partial pressure of oxygen
Fetal Hemoglobin (HbF)
found in fetal blood that has a greater affinity for oxygen than adult/maternal hemoglobin to help keep oxygen in the fetus
Placenta is an _______ organ. This is because it produces _____
endocrine ; progesterone, estrogen and human chroionic gonadotropin (hCG) to maintain pregnancy
Placental barriers function is also _______ ; _____ cross to serve as protective function
immune protection; antibodies
Umbilical Arteries
carry blood away from fetus toward the placenta, like arteries carrying blood away from heart
Umbilical Vein
like veins from the heart, they carry blood blood from placenta to the fetus
Oxygenation (Gas Exchange) in fetus occurs at the ____ rather than the ____
placenta; fetal lungs
Differences in Fetal and Adult Circulation
- lungs and liver not significant prior to birth
- gas exchange at placenta instead of lungs
- Detoxification and metabolism controlled by mothers liver
Shunts
constructs in fetus to shield away lungs and liver as they are underdeveloped and sensitive to high blood pressure
Foramen Ovale
a type of shunt, one way valve connecting the right to the left atrium
pumps blood from inferior vena cava -> right atrium -> left atrium -> aorta
instead of right atrium to right venticle
Unlike adult circulation, the ___ side of the heart is at ___ pressure in developing fetus than the ___ side, which pushes blood through the opening. At birth, this pressure differetial switches, ____ the foramen ovale.
right, higher, left, shutting
Ductus Arteriosus
a type of shunt that shunts leftover blood from pulmonary artery to the aorta.
Ductus Venosus
a type of shunt which bypasses the liver by shunting blood returning fro placenta via umbilical vein directly to the inferior vena cava
liver receives blood supply from smaller hepatic arteries in systemic circulation
The larger the animal, the ___ the gestation period and the _____ offspring per pregnancy
longer; fewer
First Trimester of Human Gestation
- Major Organs Develop
- Hear Beat Begins to Beat
- Eyes, Gonads, Limbs, Liver Form
- Cartilaginous skeleton hardens to bone
- Embryo has become Fetus
- 9 cm long
Second Trimester
- Fetus grows and moves within amniotic fluid
- Toes/Fingers Elongate
- 30-36cm
Third Trimester
Rapid growth and brain development
Antibodies transported by highly selective active transport from mother to fetus to prepare for outside world
Growth Rate slow and fetus is less active as less room
Parturition
vaginal childbirth rhythmic contractions coordinated by prostaglandins and oxytocin
Three Phases of Birth
1) Cervix Thins and Amniotic Sac ruptures
2) Strong uterine contractions to birth fetus
3) Placenta and Umbilical Cord are expelled (Afterbirth)
