Chpt.3 Prenatal Development

bilaminar embryonic disc epiblast-columnar hypoblast-cuboidal second

A ___ ____ ____ is eventually developed from the blastocyst and appears as a three-dimensional but flattened, essentially circular plate of bilayered cells. It has both a superior and an inferior layer. The superior ____ layer is composed of high ____cells and the inferior ___ layer is composed of small _____ cells. This happen during ____ week.

syndrome

A ____ is a group of specific signs and symptoms. For example, Down syndrome, is a disorder with known pathogenesis, so it is more than just a set of signs and symptoms, despite the syndrome nomenclature.

reread

Adults with Down syndrome have an increased risk of developing Alzheimer disease, a brain disorder that results in a gradual loss of memory, judgment, and ability to function. Although Alzheimer disease is usually a disorder that occurs in older adults, about half of adults with Down syndrome develop this condition by age 50.

rubella

An example of an infective teratogen is the virus causing ___, which can result in cataracts, cardiac defects, and deafness.

Syphills incisors molars

Another infective teratogen is the bacterial spirochete causing ____, Treponema pallidum, because it produces defects in the ____ (Hutchinson incisor) and ___ (mulberry molar) as well as blindness, deafness, and possible paralysis if not treated.

proliferation appositional growth interstitial

Another type of physiologic process that follows induction as well as the other processes is the dramatic process of ____, which is controlled levels of cellular growth present during most of prenatal development. Growth may be by _____, in which a tissue enlarges its size by the addition of layers on the outside of a structure. In contrast, growth may be by _____, which occurs from deep within a tissue or organ.

embryonic

Because the beginnings of all essential external and internal structures are formed during the ____ period, this is considered the most critical period of prenatal development. Thus, developmental disturbances occurring during this period may give rise to major congenital malformations of the embryo.

38 somites

By the end of the third week, the mesoderm additionally differentiates and begins to divide on each side of the tube into ___-paired cuboidal segments of mesoderm, forming the ____.

congenital malformations birth First trimester (preimplantation & embryonic periods)

Clinical Considerations for Prenatal Development Developmental disturbances that involve the orofacial structures as well as other parts of the body can include ___ ___ or birth defects, which are evident at ___. When does this mostly occur?

somites

Differentiated mesoderm gives rise to the ___ which are located on both the sides of the developing nervous system.

Radiation death injury intellectual

Direct exposure to high levels of ___ can act as an environmental teratogen during the embryonic period. Radiation may injure embryonic cells, resulting in cell ___, chromosome ____, and delay of ___and physical growth. The severity of embryonic damage is associated with the absorbed dose, the dose rate, and the state of embryonic or fetal development at the time of exposure. However, congenital abnormalities have not been directly linked to a diagnostic level of radiation, such as that used in the dental setting. Scattered radiation from a radiographic examination of the oral cavity administers a dose of only a few millirads to a pregnant woman, which is not known to be teratogenic to an embryo. The American Dental Association recommends the use of dosimeters and work practice controls for pregnant dental staff who work with radiographic equipment. Studies of pregnant patients receiving dental care have affirmed the safety of dental treatment including the administration of radiographs when using the protective controls. The American College of Obstetricians and Gynecologists (2017) reaffirmed its opinion: "Patients often need reassurance that prevention, diagnosis, and treatment of oral conditions, including dental x-rays (with shielding of the abdomen and thyroid) ... [are] safe during pregnancy."

primitive streak

During the beginning of the third week of prenatal development within the embryonic period, the ___ ___ forms within the bilaminar embryonic disc.

Morphogenesis

During the embryonic period, the complexity of the structure and function of these cells increases. This is accomplished by ______, which is the process of development of specific tissue structure or shape.

embryonic folding

During the fourth week of prenatal development within the embryonic period, the disc undergoes ___ ____, establishing for the first time the axis, which places forming tissue types into their proper positions for further embryonic development as well producing a somewhat tubular embryo

Central Nervous System (CNS)

During the later part of the third week, the ___ ___ ___ begins to develop in the embryo. Many steps occur during this week to form the beginnings of the spinal cord and brain.

proliferation cellular differentiation germ layers blastocyst

During the second week of prenatal development, within the embryonic period, the implanted blastocyst grows by increased _____ of the embryonic cells, with differentiation also occurring resulting in changes in cellular morphogenesis; every ridge, bump, and recess now indicates these increase levels of ___ ___. This increased number of embryonic cells creates the embryonic cell layers (or ___ ___) within the ____. Look at table 3.4***

Face neck oral cavity

Each of the structures of the ___(3) has a primordium, the earliest indication of a tissue type or an organ during prenatal development.

induction, proliferation, differentiation, morphogenesis, maturation embryo teeth orofacial organ

Embryonic Period These physiologic processes include ___ (5) These processes cause the structure of the implanted blastocyst to become, with further development, an ____. These physiologic processes also allow the ____ and associated ____ structures as well as other ____ structures to develop in the embryo.

placenta trophoblast endometrial tissue second

Even later, the ____, a prenatal organ that joins the pregnant female and developing embryo, develops from the interactions of the ____ layer and __ ___. What week does this occur in? The formation of the placenta and the developing umbilical circulation permit selective exchange of soluble bloodborne substances between them. This includes oxygen and carbon dioxide as well as nutritional and hormonal substances.

spina bifida

Failure of fusion of the neural tube results in neural tube defects of the tissue overlying the spinal cord, such as the meninges, vertebral arches, muscles, and skin. One type of neural tube defect is ____, characterized by defects in the vertebral arches and various degrees of disability

fourth face neck

Finally, during the ____ week, the ___ and ___begin to develop, with the primitive eyes, ears, nose, oral cavity, and jaw areas.

Maturation

Finally, the physiological process of ____ of the tissue types and organs begins during the embryologic period and continues later during the fetal period. An embryo is recognizable by the eighth week of prenatal development, which is the end of the embryonic period.

neuroectoderm. neural plate neural groove

First, a specialized group of cells differentiates from the ectoderm and is now considered ______. These cells are localized to the ___ ___ of the embryo, which is a central band of cells that extends the length of the embryo from the cephalic end to the caudal end. This plate undergoes further growth and thickening, which cause it to deepen and invaginate inward forming the ___ ___. What week?

inherited voluntary

Genetic testing is a type of medical testing that identifies changes in chromosomes, genes, or proteins. Most of the time, testing is used to find changes that are associated with ____ disorders. The results of a genetic test can confirm or rule out a suspected genetic condition or help determine a person's chance of developing or passing on a genetic disorder. Several hundred genetic tests are currently in use and more are being developed. Genetic testing is ___. Because testing has both benefits and limitations, the decision about whether to be tested is a personal and complex one. A genetic counselor can help by providing information about the pros and cons of the test and discussing the social and emotional aspects of testing.

Preimplantation Period trisomy 21 meiosis

If any disturbances occur in ____ during fertilization, major congenital malformations result from the chromosomal abnormality in around 10% of cases. An example of this is Down syndrome or _____ where an extra chromosome number 21 is present after meiotic division. During what period does this happen?

Treacher Collins syndrome orofacial

If there is failure of migration of the neural crest cells to the facial region, ___ ____ ___ (TCS) or mandibulofacial dysotosis develops in the embryo. This results in failure of specific areas of ____ development, presenting with downward slanting eyes, underdeveloped zygomatic bone, drooping lateral lower eyelids, and conductive hearing loss, with malformed or absent ears as well as dental developmental disturbances, such as anodontia with absent teeth, enamel dysplasia with abnormal mineralization, and micrognathia (small lower jaw).

ectopic pregnancy

Implantation may also occur outside the uterus, involving the condition of ____, with most occurring in the fallopian tube. This disturbance has several causes but is usually associated with factors that delay or prevent transport of the dividing zygote to the uterus, such as scarred uterine tubes due to pelvic inflammatory disease. In the past, ectopic pregnancies ruptured causing loss of the embryo and threatening the life of the pregnant woman but now they are successfully treated with medications.

third mesoderm endoderm

In addition, during the beginning of the ___ week, some cells from the epiblast layer move or migrate toward the hypoblast layer only in the area of the primitive streak and become ______, an embryonic connective tissue, as well as embryonic _____.

neural crest cells mesenchyme oral, dental tissue enamel

In addition, during the third week, another specialized group of cells, the __ ___ __ (NCCs), develop from neuroectoderm. These cells migrate from the crests of the neural folds and then disperse within the _____. The NCCs are essential in formation of most ___ and ___ ___ except for the ___and certain types of cementum as well as the development of the face and neck.

fusion

In the case of the neural tube, the process of ____ as the name implies can be the joining of two separate surfaces on the embryo.

Differentiation cells tissue organs

In the process of ___, a change occurs in the embryonic cells, which are identical genetically but later become quite distinct structurally and functionally. This occurs at various rates in the embryo. Many parts of the embryo are affected, including ___, ____ types, _____, and systems.

second week ectoderm mesoderm endoderm

In what week do you see the development of embryonic cell layers? (during this time cell are developing but layers are not developed yet) When these cells are developed completely its the THIRD week _____-Origin is epiblast layer, columnar, future structures include epidermis, sensory epithelium of eyes ears nose nervous system, neural crest cells, mammary and cutaneous glands ____-Origin migrated epiblast cells, varies shape, future structures are dermis, muscle, bone, lymphatics, blood cells and bone marrow, cartilage, reproductive, and excretory organs, connective tissue ____-origin migrated epiblast cells, cuboidal, respiratory and digestive system linings liver, pancreatic cells

chromosome abnormalites environmental teratogens (Women of reproductive age should avoid teratogens to protect the developing infant from possible congenital malformations)

Malformations can be due to genetic factors, such as ____ ___ or____ agents and factors. These environmental agents and factors can include infections, drugs, and radiation and are considered ____.

3rd week

Mesenchyme (with pointer). what week?

neural folds neural tube FOURTH fusion

Near the end of the third week, the neural groove deepens further and is surrounded by the ___ ___. As further growth of the neuroectoderm occurs, the ____ ____ is formed during the ___ week by the neural folds undergoing ____ at the most superior part.

ectodermal dysplasia anodontia

One syndrome that can occur within the embryonic period is ___ ___, which involves the abnormal development of one or more structures from ectoderm. There may be partial or complete ____, the absence of some or all teeth in each dentition, and the teeth that are present for either dentition frequently have developmental disturbances.

trophoblast embryoblast

Preimplantation Period After a week of cleavage, the blastocyst consists of a layer of peripheral cells, the ___ layer and a small inner mass of embryonic cells or _____ layer.

mitosis, cell division morula blastocyst (or blastula)

Preimplantation Period After fertilization, the zygote then undergoes ____, or individual____ or cleavage. After initial cleavage, the solid ball of cells is known as a ____. Because of the ongoing process of mitosis and secretion of fluid by the cells within the morula, the zygote becomes a vesicle known as a ___ .

implantation endometrium

Preimplantation Period By the end of the first week, the blastocyst stops traveling and undergoes _____ and thus becomes embedded in the prepared _____, the innermost lining of the uterus on its back wall.

karyotype

Preimplantation Period The photographic analysis of a person's chromosomes is done by orderly arrangement of the pairs in a _____, with the sex known by the presence of either having XX chromosomes for woman or XY for man.

diploid 46

Preimplantation Period The result of this process is the joining of the ovum's chromosomes with those of the sperm. This joining of chromosomes from both biologic parents forms a new individual with "shuffled" chromosomes. To allow this formation of a new individual, the sperm and ovum are joined, resulting in the proper number of chromosomes, which is the ____ number of ___.

Pre-Implantation (fertilization & implantation) zygote and blastocyst

Prenatal Development periods 1st week is called the _____ period What is made during this time? (2)

Start, Pregnancy Birth, child 9 gestation trimesters

Prenatal development begins with the____ of ____ and continues until the ____ of the ____; the ___ months of ____ is usually divided into 3-month time spans or ____

endometrium amniotic cavity yolk sac

Second Week-bilaminar embryonic disc After its creation, the disc is suspended in the ___ lining the uterus between two fluid-filled cavities, the ___ ____, which faces the epiblast layer, and the ___ ____, which faces the hypoblast layer and serves as initial nourishment for the disc.

fetal tetracycline stain

Systemic tetracycline antibiotic therapy of the pregnant woman can act as a teratogenic drug during the ___ period. This therapy can result in ___ ____ with the child's primary teeth that are developing at that time. This intrinsic yellow to yellow-brown discoloration within the teeth can occur in slight, moderate, or severe degrees as the antibiotic becomes chemically bound to the dentin for the life of the tooth. This stain is easily visible because of the transparency of overlying enamel. The adult's permanent teeth may also be affected, similarly to the primary teeth, if the drug is given to a child during their development. If the permanent teeth are involved, treatment may require full-coverage crowns or veneers to improve the appearance of the teeth, although, in some cases, vital tooth whitening may even out the discoloration. Thus, this type of antibiotic therapy should be avoided if possible in pregnant women and children

reread

THIRD WEEK A, Formation of the neuroectoderm from the ectoderm within the neural plate that thickens to form the neural groove. B, Neural groove deepens to become surrounded by the neural folds. C, Neural folds meet and fuse, forming the neural tube.

fetal

The ___ period of prenatal development follows the embryonic period. It encompasses the beginning of the ninth week or third month continuing to the ninth month, with the maturation of existing structures occurring as the embryo is enlarging to become a fetus. This process involves not only the physiologic process of maturation of the individual tissue types and organs but also further proliferation, differentiation, and morphogenesis, as discussed before with the development of the embryo.

preimplantation period the embryonic period

The _____ period make up the first trimester of the pregnancy.

Non-Invasive Prenatal Testing (NIPT)

The advent of highly sensitive and efficient methods for DNA sequencing has allowed a totally new approach for prenatal genetic testing, at least for the initial screening test for a new pregnancy. Specifically, these new methods allow the detection of the very small amounts of fetal DNA that naturally circulates in the mother's blood during pregnancy. This is called ____.

cephalic end ectoderm & endoderm only third week.

The disc now has a __ __ or head end. At this end, the oropharyngeal membrane forms, which consists of what layers? what week is this?

preimplantation ovum fertilization zygote meiosis, ovum

The first period, the _____ period of prenatal development, takes place during the first week after conception. At the beginning of the first week, a woman's ___ is penetrated by and united with a man's sperm during ___. This union of the ovum and sperm subsequently forms a fertilized egg or zygote. During fertilization, the final stages of ___ occur in the ____.

induction

The first physiological process involved during prenatal development is the process of_____, the action of one group of cells on another, which leads to the establishment of the developmental pathway in the responding tissue and which is now considered to be compartmentalized.

embryonic period pattering

The second period, the ____ period of prenatal development, extends from the beginning of the second week to the end of the eighth week. Certain physiologic processes or spatial and temporal events called ____ occur during this period, which are considered key to further development.

prenatal support tissue embryo

The trophoblast layer later gives rise to important ___ ___ ____. The embryoblast layer later gives rise to the ____ during the prenatal period that follows the embryonic period.

trilaminar embryonic disk ectoderm

Third Week With three layers present, the bilaminar disc has thickened into a __ ___ ___. With the creation of the new embryonic cell layers of mesoderm and embryonic endoderm, the epiblast layer is now considered ___.

proliferation of cells bilateral symmetry

This furrowed, rod-shaped thickening in the middle of the disc results from an increased ____ ___ ___ in the midline area. The primitive streak causes the disc to have ___ ___, with a right half and left half.

primitive mouth digestive tract caudal 3rd week

This membrane is the location of the future ___ ___ or stomodeum of the embryo and thus the beginning of the ____ ___. The disc also has a ____ end or tail end. What week?

oropharyngeal cloacal forgut pharynx yolk sac midgut hindgut digestive tract 4th week

This movement of the embryonic cell layers forms one long and hollow tube lined by endoderm from the cephalic end to the caudal end of the embryo—specifically, from the ____ membrane to the ____ membrane The anterior part of this tube is the ____, which forms the primitive ____ or primitive throat and includes a part of the primitive ___ ____ as it becomes enclosed with folding. The two more posterior parts, the ____and ____, respectively, form the rest of the mature pharynx as well as the remainder of the ___ ___. week?

4th week

Trilaminar embryonic disc has folded into the embryo. Disc now has undergone embryonic folding as a result of extensive growth of the ectoderm and there is development of the brain with spinal cord, heart, and digestive tract. What week does this occur?

preimplantation period embryonic period, fetal period

What are the 3 distinct successive periods that have varying time spans during prenatal development?

fetal period

What constitutes the last 2 trimesters?

2-8 weeks (induction, proliferation, differentiation, morphogenesis, maturation) disc embryo folded embryo

What weeks are the embryonic period? What is made during this time? (3)

3rd-9th month (maturation matured embryo fetus

What weeks are the fetal period? what happens during this time? (2)

Fetal alcohol syndrome

___ ____ ___ presents with noted orofacial features and various levels intellectual disability. This syndrome is caused by the pregnant women's excessive use of ethanol during the embryonic period.

Down Syndrome microdontia (teeth smaller than normal)

______ This condition may also involve increased levels of periodontal disease, delayed tooth eruption, and fewer teeth present with _____.

Cytodifferentiation histodifferentiation Morphodifferentiation

______ is the development of different cell types. ______ is the development of different histologic tissue types within a structure. Development of specific tissue morphology _______ is the development of the differing morphology, which makes up its structure or shape, for each organ or system.

Embryology

______ is the study of prenatal development.

Amniocentesis

_________ (or amniotic fluid test [AFT]) is a prenatal diagnostic procedure to detect chromosomal abnormalities where the amniotic fluid is removed and its fetal cells are grown for microscopic study of the chromosomes as well as sampled for determination of other fetal complications. Pregnant women now have the option of getting a new type of prenatal genetic test, one that does not pose any risk and it can be performed very early in the pregnancy. This non-invasive prenatal testing (NIPT) is a cell-free fetal DNA testing that involves a simple blood draw from the pregnant woman.

primordium

the earliest indication of a tissue type or an organ during prenatal development