Ch 29: Development Flashcards
What are the steps of fertilization?
- Sperm meets egg and secretes acrosome
- Digestive enzymes of acrosome degrades protective zona pellucida layer
- Sperm penetrates and delivers nuclueus
- Zona pellucida instantly hardens becoming impermeable to any other sperm
- Meoisis 2 is completed
Cleavage begins immediately at _____ and consists of what 3 stages?
- Fertilization
- 2-cell, 4-cell, and 8-cell stages.
Cleavage is the…
rapid mitosis/division of the zygote upon fertilization
Cells during the cleavage stage are _____.
pleuripotent.
If a cell is pleuripotent, it means…
that it has the potential to develop to be any cell in the body.
Cell pleuripotentcy is lost at what stage of cleavage?
8-cell
What occurs during the 2-cell stage of cleavage?
- Proteins shift to one side
- Cell splits in two
- Protein per side may differ
What do the proteins in zygote regulate?
- Gene expression
- The ability of cells to make certian proteins
What are the characteristics of differentiation and determination?
- Fate of what cells will become is determined
- Some genes are turned off
- This gives cells identity and function
True or False
As rapid mitosis occurs, the zygote continues to grow.
False
It stays the same size
What are the three stages of prenatal development?
- Preembryonic stage
- Embryonic stage
- Fetal stage
The preembryonic stage is subdivided into what four parts?
- Zygote
- Cleavage
- Morula
- Blastocysts
Define:
Zygote
A single diploid cell formed by the union of egg and sperm
Define:
Cleavage
- Mitotic division of the zygote into smaller, identical blastomeres
Define:
Morula
A speroidal stage consisting of 16 or more blastomeres
Define:
Blastocyst
- Fluid filled, spheroidal stage with an outer mass of trophoblast cells and inner mass of embryoblast cells
- Becomes implanted nt he endometrium
- Inner cell mass forms embryonic disc and
- differentiates into three primary germ layers
Define:
Embryonic stage
- A stage in which the primary germ layers differentiate into organs and organ systems
- Ends when all organ systems are present
Define:
Fetal stage
A stage in which organs grow and mature at a cellular level to the point of being capable of supporting life independently of the mother.
The morula cells secrete fluid to form a _____, which form __ to __ days after fertilization.
blastocysts, 4-16
In a blastocyst, the inner layer is called the _____ and will become the ____. The outer cell layer consists of _____, which will become the _____.
inner cell mass, embryo, trophoblasts, embryonic membrane
What are the four extra embryonic membranes? Give description of each.
- Chorion; outermost layer which fuses with endometrium upon implantation and will become placenta
- Amnion; fluid filled sac around embryo
- Yolk sac; non-functional
- Allantois; non-functional
In its early development, the zygote gets its nutrients directly from the _____.
endometrium
At what part of the preembryonic stage does implantation occur?
blastocyst
Around day 15, the embryonic disc forms a thickened cell layer called the _____ along the midline.
primitive streak
Cells migrate toward and into the primative streak to form…
three germ layers.
Name the 3 primary germ layers that form from the primative streak.
- Ectoderm
- Mesoderm
- Endoderm
The ectoderm germ layer is the _____ layer and will become _____.
outer, skin and nervous system
The mesoderm germ layer is the _____ layer and will become _____.
middle, connective tissues and muscles
The endoderm germ layer is the _____ layer and will become _____.
inner, digestive system
The end of gastrulation is at __ days, and the zygote becomes ____.
16, an embryo
Gastrulation is the start of the formation of the…
gastric/digestive system.
Neurulation is….
the development of the nervous sytem
Organogensis is…
the formation of the organs
What are the characteristics of neurolation?
- Begins in ectoderm
- Primitive strek folds into a neural tube that runs the length of the embryo
- Top becomes brain, rest is spinal cord
- Ends around 3 weeks
In organogensis, what occurs during the first four weeks?
- Heart is formed and detectable by 3 weeks
- Formation of limb buds
- Eye development has started
In organogensis, what occurs in weeks 5-7?
- Full head development
- Full eye development
- Ears
- Digits
What has occured by the end of week 8?
Full species specific traits have been acquired.
What are the developmental traits of the second trimester?
- Facial movements
- Sucking reflex
- Hair
- Eyelids and lashes by the end at six months
What are the characteristics of the third trimester?
- At 7 months
- Eyes open
- Little body fat
- Underdeveloped lungs
- Premature birth range
- 8-9 months is when most growth occurs and systems mature for birth
What are the characteristics of the premature birth range?
- Begins at 7 months
- Baby will require medical attention
- Have underdeveloped lungs
- Will require respiraters and heaters
Birth is also known as _____/
Parturition
What are the steps of fetal delivery?
- Increasing levels of estrogen and progesterone from placenta, uterine stretching and pressure on cervix eventually lead to the secretion of oxytocin
- Oxytocin initiates contractions
- Continual pressure causes oxytocin secretion to continue creating positive feedback loop
- Contractions continue in strength pushing fetus into birth canal and out of the body.
- Placent is then delivered.
Mammary glands produce _____ for the first __ to __ days after birth.
colostrum, 1-3.
Colostrum contains the antibody _____.
Why is this important?
- IgA
- Provides systemic immunity for the first few days until mothers milk takes over
What does prolactin do?
stimulates mammary gland to produce milk
Secretion of prolactin starts in week __, and continues to…
5, increase during pregnancy
By the end of pregnancy, prolactin levels are __ times than they were at start.
20 times
What role does ocytocin play in nursing?
- Causes milk ejection
- Initiated by sucking
- If no production, milk production will stop
- If producing, volume will grow with baby to meet its needs
