Embryogenesis and Development Flashcards
Ampulla
Widest part of fallopian tube where fertilization happens
Acrosomal enzymes
When the sperm meets the secondary oocyte, it releases acrosomal enzymes to help it penetrate the ovum
Acrosomal apparatus
When the sperm penetrates the ovum, it makes this tubelike structure to penetrate the cell membrane of ovum and then sperm pronuclei enter the ovum.
Cortical reaction
When the sperm penetrates the ovum, calcium ions are released and this leads to depolarization of the ovum’s membrane. This increases metabolism of diploid zygote and makes the fertilized membrane impenetrable to other sperm.
Dizygotic (fraternal) twins
2 eggs are released in one cycle and fertilized by 2 sperm. Each zygote makes it own placenta, chorion, and amnion.
Monozygotic (identical) twins
Single zygote splits into two
What does incomplete division of a zygote result in?
Conjoined twins
Name the three combinations of chorion and amnion that twins can have.
Monochorionic/monoamnionic, monochorionic/diamnionic, dichorionic/diamnionic
As the zygote travels from the fallopian tube to the uterus for implanment, what process is it undergoing?
Division
Embryo
First division of zygote
What happens to embryo size during first few divisions? What increases? What is the advantage of this?
Embryo size is constant. The ratio of the nuclear space to cytoplasmic space increases as well as the ratio for surface area over volume. This increases area for gas and nutrient exchange.
Indeterminate cleavage
Cells can still divide into whole organisms. Monozygotic twins arise from these cells
Determinate cleavage
Cells are already committed to differentiating into a certain type of cell
Morula
Solid mass of cells after several divisions after embryo
Blastula/Blastocyst
Morula undergoes blastulation to become this. It is a hollow sphere where the trophoblast cells make up the boundary while there is an inner cell mass. The blastocoel is the fluid filled cavity.
Blastocoel
Fluid filled cavity of blastocyst
Trophoblast cells
Give rise to chorion and placenta
Inner cell mass
Give rise to organism
Chorionic villi
Trophoblast have these which help them penetrate endometrium and develop into placenta
Umbilical cord
Connects embryo and placenta. It has 2 arteries and 1 vein
Yolk sac
- Supports embryo until placenta made
- site for early blood cell development
Allantois
-Involved in early fluid exchange between embryo and yolk sac
What two structures develop into the umbilical cord?
Allantois and yolk sac
Amnion
Surrounds allantois and filled with amniotic fluid
Amniotic fluid
Absorbs shock during pregnancy
Chorion
Surrounds amnion for additional protection
Gastrulation
Generation of 3 distinct cell layers
3 steps of gastrulation
- Small invagination in blastula
- Cells move towards invagination and blastocoel disappears
- Tube develops
Archenteron
Membrane invagination becomes gut later
Blastopore
Opening of archenteron
Deutorostomes
Humans are this and this when the blastopore becomes the anus
Protostomes
Blastopore becomes mouth
The three primary germ layers
Ectoderm, mesoderm, endoderm
Ectoderm
- outermost layer
- skin, hair, nails
- The epithelia of nose, mouse, and lower anal canal
- eye lens, nervous system, inner ear
Mesoderm
- middle layer
- different systems, gonads, adrenal cortex
- muscular and connective tissue for digestive and respiratory system
Endoderm
- innermost layer
- epithelial lining of digestive and respiratory
- pancreas, thyroid, bladder, distal urinary tract, parts of liver
Selective transcription
Only genes needed for that particular cell type are transcribed
Induction and its steps
Ability of one group of cells to influence the fate of nearby cells
- Organizing cells release inducers or chemicals
- Inducers diffuse to responsive cells
Organizing cells
Release inducers
Responsive cells
Respond to inducers
Neuralation
Development of nervous system
Neuralation 3 steps
- Rod of mesodermal cells (notochord) forms along long axis of organism like a primitive spine
- Notochord induces group of overlying ectodermal cells to slide inward to form neural folds which surround a neural groove
- Neural folds grow toward each other to make a neural tube (precursor to CNS)
Neural crest cells
Lead to peripheral nervous system
Teratogens
Substances that interfere with development of embryo causing defects and/or death
What will happen to the fetus if the mother is hyperglycemic?
It will be large and hypoglycemic
Folic acid deficiency in the mother leads to
Neural tube defects
Specification
Cell is REVERSIBLY designated as a specific cell type. It can still become any cell type.
Determination
Cell is irreversibly committed to a specific lineage
Name 2 ways differentiation can happen
- Parent cell unequally distributes mRNA and proteins to daughter cells. Presence of specific mRNA and protein molecules lead to determination.
- Nearby cells secrete morphogens that cause neighboring cells to follow a particular development pathway
Differentiation
Physical changes to cell to match determined cell type
Stem cells
Cells that have not yet differentiated or that give rise to another cells that will differentiate
Totipotent stem cells
Have the greatest potency: can differentiate into any cell type in fetus or placental structures
Pluripotent stem cells
When the 3 germ cell layers have developed, these cells can differentiate into any except placental structures.
Multipotent stem cells
Can differentiate into multiple types of cells within a particular group
Inducers
Growth factors (peptides) that promote differentiation and mitosis in specific tissues
Reciprocal development
Bidirectional induction
How can morphogens induce different responses?
- Through concentration gradients
2. Multiple morphogens makes different combinations
Cell migration
Cells must be able to disconnect from adjacent structures and migrate to current location
Apoptosis
Programmed cell death; cell divides into self-contained protrusions called apopotic blems which can be broken apart into apoptitic bodies and digested by other cells. Materials are recycled.
Necrosis
Cell death in which cell dies from injury. It bursts open and internal substances are spilled.
Regenerative capacity
Ability of organism to regrow certain parts of body. Stem cells migrate to and initiate growth.
Complete regeneration
Lost/damaged replaced with identical tissue
Incomplete regeneration
Newly formed tissue isn’t identical structure/function to lost/damaged tissue
Regenerative capacities of the liver, kidney, and heart
From highest to lowest: Liver>kidney>heart
Senescence
Biological aging can occur at cellular and organismal level
Effect of shortened telomeres
Cells cannot divide
Telomeres
Prevent genetic information loss
Telomerase
Synthesizes telomeres and inhibits senescence; possibly promotes cancer
Placenta roles
Transfer of nutrients and gases via diffusion and via HbF, transfer antibodies, make estrogen, progesterone, and hCG
Fetal Hemoglobin
It has higher affinity for oxygen than adult hemoglobin
Umbilical arteries
Carry deoxygenated blood away from fetus to placenta
Umbilical vein
Carry oxygenated blood to fetus
What two organs does the fetus not use and what are they replaced by?
Lungs; gas exchange happens at heart
Liver; mother’s liver does detoxification and metabolism
After birth, what affects the lungs and liver the most?
High blood pressure
Shunts
Actively divert blood away from the lungs and liver in the fetus as they develop
Foramen ovale
One way valve which lets blood go from right atrium to left atrium
How is the foramen ovale closed after birth?
Before birth, the pressure in the right side is greater but this reverses after birth and shuts the shunt
Ductus arteriosus
Allows leftover blood from pulmonary artery to aorta
Ductus venosus
Allows blood from placenta to go to inferior vena cava
Does the liver have any vasculature during fetal developmenT?
It has small hepatic arteries
First trimester
- Become a fetus
- Major organs develop
- Brain fairly developed
- Heart beats
- Skeleton hardens
Second trimester
- Lots of growth
- Human appearance, toes, fingers
- Moves in amniotic fluid
Third trimester
- Rapid growth
- Further brain development
- Antibodies transported at high rate
- Fetus moves less because less room
Partuition
Prostaglandins and oxytocin lead to uterine contractions which lead to vaginal birth
3 stages of vaginal birth
- Cervix thins out and amniotic sac ruptures
- Uterine contractions lead to birth
- Afterbirth is when the placenta and umbilical cord are expelled
