test 7 Flashcards
when does prenatal development begin
how is it divided
- begins at the start of pregnancy and continues until the birth of the child
- 9 months of gestation divided into 3 trimesters
what periods make up each trimester
first trimester: preimplantation period AND embryonic period
second and third trimester: fetal period
define primordium
earliest indication of a tissue or an organ during prenatal development
developmental disturbances can include ________ which are evident at ______
most occur during both ____ and _____
Such malformations occur in _____ cases
One of leading causes of _____
developmental disturbances can include CONGENITAL MALFORMATIONS which are evident at BIRTH
most occur during both PREIMPLANTATION PERIOD and EMBRYONIC PERIOD
Such malformations occur in 3/100 cases
One of leading causes of INFANT DEATH
what causes malfomation
- genetic factors (chromosome abnormalities)
- environmental agents/factors
what are teratogens
environmental agents and factors including infections, drugs, chemicals, and radiation
examples of teratogens
drugs: ethanol (alcohol), tetracycline, lithium, methotrexate, warfarin, thalidomide, androgens, progesterone
chemicals: methymercury, polychlorinated biphenyls
infections: rubella virus, syphilis spirochete, herpes simplex, human immunodeficiency
radiation: high levels of ionizing radiation
pregnant women and dental xrays`
diagnostic levels of radiation should be avoided but have not been directly linked to congenital malformations
if xrays are needed, wear proper lead gear and minimize exposure
PREIMPLANTATION PERIOD
______ week after conception
______ meets ______ during fertilization
Union of ovum and sperm forms a _______
During fertilization, the final stages of ______ occur in the _____
FIRST week after conception
OVUM meets SPERM during fertilization
Union of ovum and sperm forms a FERTILZIED EGG (ZYGOTE)
During fertilization, the final stages of MEIOSIS occur in the OVUM
PREIMPLANTATION PERIOD
The result of this process is joining of ovum’s _______ with those of the sperm
Joining of chromosomes from both biological parents forms a new individual with “_________” chromosomes
To allow this formation of a new individual, the sperm and ovum, when joined, have proper number of chromosomes (from diploid number of ___)
If both these cells carried the full complement of chromosomes:
- Fertilization would result in a zygote with ___ the proper number
- Result is severe ________ and/or _____
The result of this process is joining of ovum’s CHROMOSOMES with those of the sperm
Joining of chromosomes from both biological parents forms a new individual with “SHUFFLING” chromosomes
To allow this formation of a new individual, the sperm and ovum, when joined, have proper number of chromosomes (from diploid number of 46)
If both these cells carried the full complement of chromosomes:
- Fertilization would result in a zygote with 2 TIMES the proper number
- Result is severe MALFORMATINS and/or PRENATAL DEATH
KARYOTYPE
The _______ of a person’s chromosomes is done by ______ arrangement of the pairs in a karyotype, with the sex known by the presence of either having ___ chromosomes for females or ___ for males
The PHTOGRAPHIC ANALYSIS of a person’s chromosomes is done by ORDERLY arrangement of the pairs in a karyotype, with the sex known by the presence of either having XX chromosomes for females or XY for males
PREIMPLANTATION PERIOD
After fertilization:
Zygote undergoes _______ (individual cell division or _____)
Ongoing process of ______ and secretion of
fluid by the cells
Zygote becomes a vesicle known as a _________
After fertilization:
Zygote undergoes MITOSIS (individual cell division or CLEAVAGE)
Ongoing process of MITOSIS and secretion of
fluid by the cells
Zygote becomes a vesicle known as a BLASTOCYST
what are the hourly/daily stages of growth of a zygote
zygote: 12-24 hours
2 cells: 30hours
4 cells: 40-50 hours
8 cells: 60 hours
16 cells: 4 days
blastocyst: 5 days
implantation 6 days
PREIMPLANTATION PERIOD
describe implantation in 3 steps
- blastocyst approaches endometrium
- trophoblasts invade endometrium
- endometrial tissue grows over the blastocyst to complete implantation
what developmental disturbances can occur during the PREIMPLANTATION PERIOD
down syndrome (trisomy 21)
DOWN SYNDROME
Disturbances in ______ (during fertilization)
Major congenital malformations result from
_______ abnormality
___% of cases
Example: Down syndrome (_______), where _____ chromosome number 21 is present after meiotic division
Disturbances in MEIOSIS (during fertilization)
Major congenital malformations result from
CHROMOSOMAL abnormality
10% of cases
Example: Down syndrome (TRISOMY 21), where EXTRA chromosome number 21 is present after meiotic division
what are the physical differences in patients with down syndrome (6)
- epicanthic folds
- flat, broad face
- widely spaced eyes
- oblique eyelid fissures
- flat bridged nose
- furrowed lower lip
CLINICAL CONSIDERATIONS FOR PATIENTS WITH DOWN SYNDROME
Eruption patterns ______ and may occur in an
______ order; Delay may be as long as _____
Patient may have altered ____; not enough
______ to chew some foods
High rate of _______
- Other irregularities: (7)
Eruption patterns DELAYED and may occur in an UNUSUAL order; Delay may be as long as 2-3 YEARS
Patient may have altered DIET; not enough
TEETH to chew some foods
High rate of MISSING TEETH (primary and permanent)
Other irregularities:
1. microdontia/malformed teeth
2. underdeveloped midface/jaw
3. severe crowding for those who have all their permanent teeth
4. small/conical roots (more likely to have perio disease)
5. tongue may protrude/ macroglossia
6. narrow palatal arch/high palatal vault
7. less space for tongue, affects speech and mastication
what is the second period in prenatal development
when does it occur
EMBRYONIC PERIOD
beginning of the second week to the end of the eighth week
EMBRYONIC PERIOD
Certain _______ processes or spatial and
temporal events called _____ occur during
this period
Physiological processes that facilitate _______
Certain PHYSIOLOGICAL processes or spatial and temporal events called PATTERNING occur during this period
Physiological processes that facilitate FURTHER DEVELOPMENT
induction
proliferation
differentiation
morphogenesis
maturation
induction: action of one group of cells on another that leads to the establishment of the developmental pathway in the responding tissue
proliferation: controlled by cellular growth and accumulation of byproducts
differentiation: change in identical embryonic cells to become distinct structurally and functionally
morphogenesis: development of specific tissue structure or differing form due to embryonic cell migration and inductive interactions
maturation: attainment of adult function and size due to proliferation, differentiation, and morphogenesis
EMBRYONIC PERIOD
describe induction (4)
- first physiological process
- action of one group of cells on another (responding tissue)
- establishment of the developmental pathway
- “game plan”
EMBRYONIC PERIOD
Describe proliferation (3)
- after/follows induction
- dramatic process of controlled levels of cellular growth
- present during most prenatal development
EMBRYONIC PERIOD
what are the two types of growth during proliferation
interstitial: occurs from deep WITHIN a tissue or organ
appositional: tissue enlarges its size by the ADDITION OF NEW LAYERS on the OUTSIDE of a structure (increases thickness)
EMBRYONIC PERIOD
describe differentiation (3)
- change occurring in genetically identical embryonic cells which later become distinct functionally and structurally
- occurs at various rates in the embryo
- many parts of the embryo are affected: cells, tissue types, organs, and systems
EMBRYONIC PERIOD (SECOND WEEK)
Implanted blastocyst grows by:
1) Increased _______ of the embryonic cells
2) _______ also occurring
3) Resulting in cellular _______
Every ridge, bump, and recess now indicate these increased levels of ________
Increased number of embryonic cells = creates
the embryonic cell layers (________) within the _______
Implanted blastocyst grows by:
1) Increased PROLIFERATION of the embryonic cells
2) DIFFERENTIATION also occurring
3) Resulting in cellular MORPHOGENESIS
Every ridge, bump, and recess now indicate these increased levels of CELLULAR DIFFERENTIATION
Increased number of embryonic cells = creates
the embryonic cell layers (GERM LAYERS) within the BLASTOCYST
what are the germ layers
ectoderm, mesoderm, endoderm, neural crest cells
*neural crest cells are not present in the embryonic disc until later in the 3rd week
ECTODERM
- origin
- morphology
- future structures
- epiblast layer
- columnar cells
- epidermis, sensory epithelium of eyes, ears, nose, mammary and cutaneous glands
MESODERM
- origin
- morphology
- future structures
- migrating cells from the epiblast layer
- varies
- dermis, muscle, bone, lymphatics, blood cells, bone marrow, cartilage, reproductive organs
ENDODERM
- origin
- morphology
- future structures
- hypoblast layer
- cuboidal
- respiratory and digestive system linings, liver and pancreatic cells
NEURAL CREST CELLS
- origin
- morphology
- future structures
- migrating neuroectoderm
- varies
- components of the nervous system, pigment cells, connective tissue proper, cartilage, bone, certain dental tissues
SECOND WEEK
the bilaminar embryonic disc is developed from what
how does it appear
what are the layers
developed from the blastocyst
appears as a flattened circular plate of bilayered cells
Superior layer/epiblast layer: made of high columnar cells
inferior layer/hypoblast layer: made of small cuboidal cells
SECOND WEEK
____ and developing _____ circulation
Permit selective exchange of soluble ________ substances between ________ and _______
Includes: (4)
PLACENTA and developing UMBILICAL circulation
Permit selective exchange of soluble BLOODBORNE substances between PREGNENT WOMEN and DEVELOPING EMBRYO
Includes OXYGEN, CARBON DIOXIDE, AND NUTRITIONAL/HORMONAL SUBSTANCES
EMBRYONIC PERIOD (THIRD WEEK)
at the beginning of the third week:
______ forms within the _______
PRIMITIVE STREAK forms within the BILAMINAR EMBYONIC DISC
THIRD WEEK
Embryonic connective tissue comes from _____ cell layers
Become _____ cells
Mesenchymal cells have potential to ______ and _______ into diverse types of _________
Forming cells (such as ________)
Embryonic connective tissue comes from MIGRATORY cell layers
Become MESENCHYME cells
Mesenchymal cells have potential to PROLIFERATE and DIFFERENTIATE into diverse types of CONNECTIVE TISSUE
Forming cells (such as FIBROBLASTS, CHONDROBLASTS, AND OSTEOBLASTS)
Mesenchyme: (mesenchymal connective tissue) is an example of _______ connective tissue, a type of _______ connective tissue, which is derived from _______ embryonic (or _____) layers and located _______ the embryo.
Mesenchyme: (mesenchymal connective tissue) is an example of RETICULAR connective tissue, a type of LOOSE connective tissue, which is derived from ALL THREE embryonic (or GERM) layers and located WITHIN the embryo.