horse-shoe shaped spaces between the lips and the cheeks anteriorly and laterally and the teeth and the gums medially and posterially
Buccal fat pad
a dense pad of underlying fat tissue at the posterior portion of each vestibule covered by the buccal mucosa
small elevation of tissue on the inner portion of the buccal mucosa that protects the opening of the parotid duct
where pink labial or buccal mucose meets the red alveolar mucosa at the mucobuccal fold
a dense pad of tissue just distal to the last tooth of the mandibular arch
gingiva at the margin of each tooth, also called free gingiva, which forms a cuff above the neck of the tooth
a space that the inner surface of the gingiva faces
gingiva between adjacent teeth, an extension of attached gingiva
lateral to each deep lingual vein, have fringe like projections
What periods of prenatal development make up the first trimester?
When do most developmental problems in prenatal development occur?
in the first trimester
environmental agents such as infections, drugs, and radiation that may cause malformations to the fetus
the earliest indication of a part or an organ during prenatal develpment
period of unattached conceptus that takes place during the first week of pregnancy
when a woman's ovum is penetrated by a man's sperm
a fertilized egg formed by the union of the ovum and sperm
When do the final stafes of meiosis occur in the ovum?
What is the result of the final stages of meiosis during fertilization?
the ovum's chromosomes join with the sperms chromosomes
When joined together how many chromosomes do the sperm and ovum have?
diploid number of 46
How is the situation of excess chromosomes in the zygote avoided?
with meiosis, because during the development of the sperm and ovum, this process emables the ovum and the sperm to reduce by one half the normal number of chromosomes to a haploid number of 23
What process does the zygote undergo after fertilization?
cell division of the zygote
true or false. mitosis of the zygote is an ongoing process
the collection of cells after the zygotes division
ongoing mitosis causes the blastocyst to what?
split into smaller and more numerous cells
Approximately how many days into the pregnancy is the zygote called the blastocyst?
about 5 days
When does mitosis take place versus when meiosis takes place?
mitosis-during growth or repair
As the blastocyst grows, where does it travel, or migrate, to?
from the site where fertilization took place (fallopian tube) to the uterus
blastocyst becomes embedded in the endometruim and continues to divide.
approximately when does implantation occur in the pregnancy
about 6 days into it
Where is the ideal place for implantation?
the back wall of the body of the uterus towards the mothers spine
dangerous situation where the blastocyst implants somewhere outside of the uterus
after 7 days of cleavage, or mitosis, name the 2 layers that the blastocyst consists of
peripheral cell layer, outside cells that will eventually become the prenatal support tissues (placenta, and umbilical circulation)
inner mass of embryonic cells, inner cells that will become the embryo
How does down syndrome occur?
there is an extra chromosome #21
the second period of prenatal development, extends from the beginning of the second week to the end of the eighth week.
Name the physiological processes that occur during the embryonic period of prenatal development
What do the physiological processes in the embryonic stage of development cause the implanted blastocyst to become?
Why are the physiological processes that occur during the embryonic period of prenatal development relevant to dental professionals?
because theses physiological processes alson allow the teeth and associated structures, as well as other organ structures, to develop in the embryo.
Name and define the first physiological process involved in the beginning of most embryological development.
Induction (the pow wow)
action of one group of cells on another that leads to the establishment of the developmental pathway in the responding tissue. The cells decide who they are going to be.
True or False. Whatever triggers cells to develop into structures from cellular interactions is poorly understood.
a type of physiological process that follows induction. it is controlled levels of cellular growth present during most of embryological development.
uncontrolled growth of cells
Name 2 types of proliveration/growth
Define Interstitial growth, and give examples.
growth that occurs from deep within a tissue or organ (like blowing up a balloon)
soft tissue growth
Define appositional growth and give an example
a tissue enlarges its size by the addition of layers on the outside of a structure (like paint on cinder block)
hard tissues such as mature bone or dental tissues
What are examples of some organs that use both interstitial and appositional growth to attain their natural size
cartilage and growing bone tissue
is growth of an embryo an increase of overall size, like a ballon? If not, then describe.
No. growth involves differential rates for different tissues and organs. for instance tooth eruption in a child, this occurs over many years allowing for the associated growth of the jaw bones.
physiological process where identically genetic cells start to become structurally and functionally different and start to become tissues.
during what physiological process do major tissues, organs, and organ systems begin to form from specialized cells?
Name the 5 different types/stages of differentiation
development of different cell types
development of different tissues within a structure
development of the differing structure, or morphology
the complexity of the structure and function of these cells increases
the process of development of specific tissue structure or shape
does induction continue to occur during the embryonic period? If so, what is it a result of?
Yes. it is a result of the new varieties of cells interacting with eachother producing an increasingly complex organism
tissues and organs growing up in form, function, and size
If anything goes wrong during the differentiation process, what is usually the end result?
When is an embryo recognizably human?
at the end of the embryonic period, or end of the eigth week
What occurs during the second week of prenatal development within the embryonic period?
the implanted blastocyst grows by increased proliferation of the embryonic cells as well as cellular morphogenesis and differentiation
bilaminar embryonic disc
forms in the second week. it is the 2 layer meeting point of 2 fluid filled cavities.
name the 2 layers of the bilaminar embryonic disc.
epiblast (top layer)
hypoblast (bottom layer)
What type of cells is the superior epiblast layer composed of?
high columnar cells
What type of cells is the inferior hypoblast layer made up of?
small cuboidal cells
What does the bilaminar disc develop into as prenatal development continues?
Name the 2 fluid-filled sacs that the bilaminar is between when it is suspended in the uterus's endometrium.
faces the epiblast layer
faces the hypoblast layer, and serves as intial nourishment for the bilaminar embryonic disc
What is the placenta formed from?
the trophoblast (outside cells) layer, and the endometrium.
The development of what 2 structures permit selective exchange of soluble bloodborne substances between the woman and the embryo?
the placenta and umbilical circulation system
What is considered the most critical period of prenatal development?
the embryonic period, because of the beginnings of all essential external and internal structures
Name and describe an example of an infective teratogen that can cross from the placent to the embryo from the pregnant woman that we discussed in class.
defects in the incisors (hutchinson's incisors) and molars (molberry molars) as well as blindness, deafness, and paralysis
Name and describe an example of a result of a teratogenic drug affect that we discussed in class.
fetal alcohol syndrome
learning disabilities and deformed facial features
Name and describe an antibiotic therapy of the pregnant woman that can act as a tetarogenic drug during the fetal period that we discussed in class.
permanently stains teeth. the antibiotic becomes chemically bonded to the dentin for the life of the tooth.
forms in the third week. It is a thickening of cells that splits the epiblast layer of the bilaminar embryonic disc in half. The right and left sides will be symmetrical. by this point, from a top view, the embryo would resemble the sole of a shoe, with a the head end wider than the tail end, and slightly narrowed in the middle.
what does the rod shaped thickening (primitive streak) in the middle of the disc result from?
increased proliferation of cells in the midline area.
What is mesenchyme? and when does it form?
an embryonic connective tissue
during the start of the third week
How is mesenchyme formed?
when some cells from the epiblast (superior) layer move or migrate toward the hypoblast (inferior) layer in the area of the primitive streak and get caught in the middle.
trilaminar embryonic disc
what the bilaminar embryonic disc turns into after the mesenchyme is formed. It now consists of 3 layers instead of 2.
What are the 3 layers of the trilaminar embryonic disc now called?
ectoderm (was previously the epiblast layer)
mesoderm (from mesenchyme)
endoderm (was previoulsy the hypoblast layer)
What does the ectoderm layer give rise to?
structures on the outside of the body:
sensory epithelium of the eyes, ears, and nose (senses)
neural crest cells
What does the mesoderm give rise to?
structures more in the middle of the body such as:
What does the endoderm layer give rist to?
structures on the very very inside of the body such as:
respiratory system linings
digestive system linings
What is ectodermal displasia?
abnormal development of the ectoderm. Affects the teeth, skin, hair, nails, facial structures, and glands. You will survive this situation, usually no miscarriage, and it is usually genetic.
head end of the embryo (wide end of the shoe)
what structure is formed at the cephalic end of the embryo? and what will it eventually become?
oropharyngeal membrane consisting of ONLY the ectoderm layer externally, and endoderm layer internally.
it will eventually become the primitive mouth and beninning of the digestive tract
tail end (more narrow part of the shoe)
what structure is formed at the caudal end of the embryo? And what will it eventually become?
The cloacal membrane (consists of only the ectoderm layer and endoderm layer)
it will eventually become the anus and terminal end of the digestive tract
At what point does the central nervous system begin to develop in the embryo?
during the later part of the third week of prenatal development
specialized group of cells the differentiate from the ectoderm and are localized to the neural plate of the embryo.
where all the neuroectoderm hangs out. A band of cells that extends the length of the embryo from the cephalic end to the caudal end
the plate starts to thicken and deepen further which forms this groove
the plate sinks even deeper and forms this fold
the neural folds meet superior to the neural groove and form this tube which fuses at the top and becomes the spinal cord
name and describe a type of neural tube defect that we discussed in class.
results as failure of fusion of the neural tube. it is characterized by defects in the verebral arches and various degrees of disability.
What are some prenatal vitamins that can be given to help preven spina bifida, cleft lip, and cleft palate?
folic acid (vitamin B9)
what are nueral crest cells? And what do they give rise to?
specialized cells the develop from the neuroectoderm and give rise to:
what do many embryologists consider the neural crest cell to be?
a fourth embryonic layer
once the neural crest cells reach their predetermined destinations, what happens with them?
the unergo differentiation into diverse cell types that are in part specified by local environmental influences
What are somites? And what do they eventually give rise to?
38 paired blocks of mesoderm along both sides of the neural tube
give rise to:
bones of head and neck
where do neural crest cells migrate from? and where do they disperse to?
migrate from the crest cells of the neuro folds, and disperse within the mesenchyme
What is the main process that occurs during the 4th week of the embryonic period? Describe this process
the disc starts to fold-establishing the human axis and placing the tissues in their proper formation for further development by extensive proliferation of the ectoderm, and differentiation of basic tissues.
After embryonic folding, describe where the layers are in relation.
endoderm is on the inside of the ectoderm, with the mesoderm filling in areas between these two layersl. this forms one hollow tube lined by the endoderm from the cephalic end to the caudal end of the embryo- or from the oropharynegeal membrane to the cloacal membrane.
What does that tube formedby embryonic folding become in the future?
the digestive tract
name the 3 major regions of the tube formed by embryonic tubing.
anterior section of the tube which eventually forms the throat. It also inclueds a protion of the primitive yolk sac as it becomes enclosed with folding.
middle section of the tube-forms the rest of the pharynx, and the rest of the digestive tract
posterior section of the tube- forms the rest of the digestive tract
What other structures begin to develop during the fourth week of prenatal development?
face, neck, and oral structures
beginning of 9th week, or third to ninth month. It is a time of maturation. Allows the newly formed tissues and organs to function
When does the embryo become a fetus?
during the fetal period of prenatal development
When can you detect the heartbeat of the fetus? And when can the mother recognize fetal movements?