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