Prenatal Development
Embryonic cell layer
(or germ layers) increased number of embryonic cells within the blastocysts
Major events in the second week of prenatal development
- bilaminar embryonic disc, a flattened circular plate of bilayered cells
3rd week of Embryonic Period
- the central nervous system begins to develop in the embryo - spinal cord and brain - neural groove deepens further and is surrounded by the neural folds
3. Fetal Period
-encompasses the beginning of the third month (9th week) of the nine months -period of time of maturation of existing structures as the embryo enlarges to become a fetus
Bilaminar embryonic disc includes these two layers
-superior epiblast layer: composed of high columnar cells and faces the amniotic cavity - inferior hypoblast layer: which is composed of small cuboidal cells and faces the yolk sac
By the end of Embryonic period (4th week) -
-the rudiments of all the principal adult organs are present ( by the end of the third month, the placenta, the site of exchange of nutrients and wastes, is functional)
Prenatal development
begins with the start of pregnancy and continues until the birth of the child
Prenatal development consists of 10 lunar months, divided into 3 successive periods
1. preimplantation period 2. embryonic period 3. fetal period
2. Embryonic Period
2nd period, extends from the beginning of the second week to the end of the eight weeks
During the _____ week of ________, the implanted blastocyst grows by increasing proliferation of the embryonic cells, with differentiation also occurring
2nd, prenatal development
The first _____ involves cellular proliferation and migration with some differentiation of cell populations.
3 weeks of embryonic period
The following _____ is characterized largely by the differentiation of all major external and internal structures.
4 weeks of embryonic period
Teratogens
Agents that damage the process of development, such as drugs and viruses, infections, radiation - women of reproductive age should avoid teratogens to protect the developmenting infant
Mesenchyme (an embryonic connective tissue)
Cells from the epiblast migrate between the epiblast and hypoblast layer to create mesnchyme
During the ______, the complexity of the structure and function of these cells increases.
Embryonic period
Period between 2 - 8 weeks
Embryonic period
1. Preimplantation Period
Fertilization to implantation, the first period prenatal development takes place during the FIRST week after conception, zygot undergoes mitosis and develops into a morula
Proliferation
Proliferation, a physiological process, following induction, controlled cellular growth during most of the prenatal development
What is the difference between the 9 months of gestation vs prenatal development?
The 9 months of pregnancy is divided into 3 month time spans/trimesters vs prenatal development is divides into 3 successive periods
Zygosis
a joining
Trophoblast layers
a layer of peripheral cells
Meiosis
a process of cell division in which diploid cells in the testes and ovaries are converted into haploid gametes
Embryoblast layer
a small inner mass of embryonic cells
End of 3rd week: the embryonic folding of the disk is turned into
an embryo
The processes that are included in the embryonic period cause the structure of the implanted blastocyst to become
an embryo
Maturation
attainment of adult function and size due to proliferation, differentiation, and morphogenesis
Cognitive malformation
birth defects, which are evident at birth occurring in both the preimplantation period and the embryonic period (first trimester)
Because of the ongoing process of mitosis and secretion of fluid by the cells within morula, they zygote becomes a vesicle known as
blastocyst (blastula)
The morula then develops into a
blastocyst, a vesicle, as resulting of continuing division and secretion of fluids
Differentiation
change in identical embryonic cells to become distinct, in both structure and function
Morphogenesis
development of different morphology, makes up its structures or shape, for each organ or system
Development of the central nervous system (3rd week)
differentiation of the neuroectoderm cells of the neural plate
Primordium
earliest recognizable stage of development in an organ of tissue during prenatal development
Oropharyngeal, buccopharyngeal, and cloacal membrane consist only of:
ectoderm and endoderm
In the 3rd week, Bilaminar embryonic disc becomes a trilaminar embryonic disc, consisting of
ectoderm, mesoderm, and endoderm
An embryo is recognized by the _____ week, which is the end of the _____ period.
eighth week, embryonic
The physiological process of maturation of the tissue types and organs begins during the ________ period and continues later during the ______ period.
embryological, fetal
Trophoblast layer gives important prenatal support tissue. The embryo blast layer later gives rise to the embryo during the prenatal period that follows the ________.
embryonic period
The second period _______ includes;
embryonic period includes: induction, proliferation, differentiation, morphogenesis, and maturation
Fourth week the ____ and _____ begin to develop, with the primitive eyes, ears, nose, oral cavity, and jaw area.
face and neck
Spina bifida
failure of fusion of the neural tube results in defects of the tissue overlapping the spinal cord, defects in the vertebral arches
Produced in the ovaries, secondary oocytes
female gametes
Last two trimesters consist of
fetal period
Induction
first physiological process involved during prenatal development, action of one group of cells on another that leads to the establishment of the development pathways in response
3rd week of prenatal development (at the Embryonic period)
forming the primitive streak within the bilaminar embryonic disc - epiblast and hypoblast come together
Mesenchyme
having potential to proliferate or differentiate into diverse types of connective tissue-forming cells
By the end of the first week, the blastocyst stops traveling and undergoes ____ thus becomes embedded in the prepared endometrium, the innermost inning of the uterus on its back wall
implantation
Ectodermal dysplasia
involves the abnormal development of one or more structures
Gametes
is the union and fusion of SEX cells
Endoderm
layer of cells lining the inner surface of the gastrula/digestive tract
Oropharyngeal memberane
location of future primitive mouth of embryo
Produced in the testes, called sperm
male gametes
End of the third week
mesoderm additionally differentiaties and begins to divide on each side of the tube into 38-paired cuboidal segments of mesoder, forming the somites
After the arrangement of the pairs in a karyotype, zygote then undergoes
mitosis, individual cell division or cleavage
First trimester includes
preimplantation period embryonic period
Aminocentesis
prenatal diagnostic procedure to detect abnormalities with amniotic fluid
After cleavage
solid ball of cells is known as morula
Neuroectoderm
specialized group of cells differentiates from ectoderm
neuroectoderm (3rd week)
specialized group of cells differentiates from ectoderm, localize to the neural plate of the embryo, plate undergoes thickening causing to deepen inward forming neural groove
Embryology
study of embryos and their development (prenatal)
Bilaminar embryonic disc
suspended in the endometrium lining the uterus between two fluids - filled cavities, the amniotic cavity, which faces the epiblast layer & yolk sac, which faces the hypoblast layer and serves as initial nourishment of the disc
The most vulnerable period of the embryo
the embryonic period
During the embryonic period, all of essential external/internal structures are formed so this is considered
the most critical period of prenatal development
In the development of the central nervous system (3rd week), there is a forming of
the neutral groove, nueral folds, neural tube
Karyotype
the number and visual appearance of the chromosomes in the cell nuclei of an organism or species, with sex known by having XX for W and XY for man
Final stage of meiosis occurs in
the ovum - resulting of the process is the joining of the ovum's chromosomes with those of the sperm
Down syndrome is caused by
the process of occasional malfunctions, producing zygotes with an abnormal number of chromosomes, resulting in individuals with congenital defects sometimes affecting the mouth and teeth at times - trisomy 21
A new organism is produced by
the union and fusion of cells
How are gametes different from somatic cells?
they contain the haploid chromosome number (one half) symbolized as "n".
A zygote develops into a new organism by
through repeated mitotic cell division
After a week, blastocyst consist of a layer of peripheral cells, ________, and a small inner mass of embryonic cells or _______.
trophoblast layer, embryo blast layer
At the end of 7-10 days, the blastocyst undergoes implantation which consists of
trophoblast layers and embryoblast layers
A zygote/egg
union and fusion of the gametes containing chromosomes (DNA) from both parents - ovum and sperm unite