Human Development- Exam 1 Flashcards
What are the 3 main stages of human development and when do they occur?
Proliferation period: 0-3 weeks
Embryonic period: 3-8 weeks
Fetal development period: 9 weeks- term
Fertilization of the ovum yields:
zygote
The zygote has a full compliment of genetic material rendering it:
diploid
The zygote undergoes mitotic division forming the:
blastomere
Greater than 32 blastomeres =
morula
At what cell stage does the morula develop an internal blastocystic cavity?
64 cell stage
When the morula develops an internal blastocystic cavity, it is now referred to as:
blastocyst
any mass that is lined with any type of cell (typically an epithelium), hollow inside, and sometimes fluid filled:
cyst
The blastocyst travels down the uterus and:
implants itself into the uterine wall
Once the blastocyst into the uterine wall, it will create arms that anchor it in place called:
syncytiotrophoblast
The blastocyst develops an inner cell mass at 6-7 days and is referred to as:
an embryoblast
Implantation of the embryoblast into the uterine wall begins at day _____ and is complete at day ____.
day 4; day 10
After the blastocyst implants into the uterine wall it becomes:
enveloped into the uterine wall
The inner cell mass of the embryoblast transitions into the:
bilaminar embryonic disc
At the stage in which the embryoblast envelopes into the uterine wall and becomes the bilaminar disc, it is now able to receive:
blood supply, nutrients, and protection
The outer cell mass of the bilaminar embryonic disc becomes the ___ & ____ layers.
cytotrophoblast & syntrophoblast
cytotrophoblast & syntrophoblast layers are precursors to the:
Placenta
What two layers make up the bilaminar embryonic disc?
Epiblast layer & Hypoblast layer
The epiblast layer of the bilaminar disc is comprised of:
ectoderm and mesoderm
The hypoblast layer of the bilaminar disc is comprised of:
endoderm
The development of a large cavity that forms at the top just under the hypoblast is called the:
yolk sac
The development of a secondary cavity above the epiblast forms the:
amniotic cavity
List the structures associated with the bilaminar embryonic disc: (6)
- epiblast layer
- hypoblast layer
- amniotic cavity
- blastocyst cavity
- syntrophoblasts
- cytotrophoblasts
Enlargment of the amniotic cavity and migration of cells out of the hypoblast form:
Heuser’s membrane
The heuser’s membrane will form the internal lining of the blastocyst cavity- now called the:
yolk sac
The internal lining of the yolk sac cavity:
Heuser’s membrane
The cell layer surrounding the entire blastocyst (completely enveloped in the uterine wall)
chorionic layer
During the 3rd week of development, the bilaminar embryonic disc is characterized by formation of the:
primitive streak, notochord, and neural tube
The cleft that starts to form on the surface of the bilamininar disc during week 3 of development
primitive streak
During the 3rd week of development, the bilaminar embryonic disc is characterized by formation of the primitive streak, notochord, and neural tube. The 3 distinct germ layers at this point at this point in development are:
Ectoderm
Mesoderm
Endoderm
The distinct embryonic germ layer that was formerly the epiblast layer:
ectoderm
The distinct embryonic germ layer that was formerly the hypoblast layer
endoderm
Cells from the epiblast layer invaginate in to form the ____ during the 3rd week of development
mesoderm
The primitive streak is characterized by the formation of:
pit, node, and groove
_____ cells invaginate within the ____ and migrate towards the cephalad until they reach the ____.
pre-notochordal
primitive node
prechordal plate
Pre-notochordal cells invaginate within the primitive ode and migrate toward the cephalad until the reach prechordal plate. They detach themselves from the ectodermal layer to line within the mesoderm forming the _____.
notochord
Functions as a primitive skeletal support of the embryo around which the axial skeleton later forms
notochord
The notochord induces the formation of ___.
somites
Precurser of the vertebral column, ribs, and associated back muscles and overlying dermis:
somites
The notochord forms in what position?
midline
The notochord is formed from _____ cells
ectodermal
The notochord is formed from ectodermal cells derived from the ____.
primitive node
The notochord functions as a primitive axial skeleton for the embryo, establishing:
symmetry and polarity of development and induction of the somites
What are the 3 layers of mesoderm during the proliferation period of human development?
Paraxial, intermediate, and lateral plate
What are the two categories of lateral plate mesoderm
parietal and visceral
List the derivatives of mesoderm (proliferation period)
- paraxial mesoderm
- intermediate mesoderm
- lateral plate mesoderm
What is derived from the paraxial mesoderm?
somites
What is derived from the intermediate mesoderm
urogenital system
What is derived from the parietal portion of the lateral plate mesoderm?
Mesothelial (serous) membranes that cover the peritoneal, pleural, and pericardial cavities
What is derived from the visceral portion of the lateral plate mesoderm?
The thin serous membranes that cover individual organs including the stomach, pancreas, and spleen
The epidermis (hair and nails) are derivatives of the:
ectoderm
The epithelium of the oral and nasal cavities and paranasal sinuses are derivatives of the:
ectoderm
Salivary and endocrine glands are derivatives of:
ectoderm
The nervous system is a derivative of:
ectoderm
Tooth enamel is a derivative of:
ectoderm
The GI tract epithelium and associated glands are derivatives of:
endoderm
Ectoderm creates a lot of ____ derives tissues and organs
epithelium
During what stage of human development does the neural tube develop?
proliferation period
During the development of the neural tube we start with a notochord, neural fold and neural crest which will further develop into the:
neural groove
During the development of the neural tube, what joins to form the neural tube?
neural crest cells
The neural tube is a precursor to:
the spinal column
During the development of the neural tube:
In the midline area, the neural crest cells will form the:
dorsal root ganglion
Spina Bifida, Meningocele, Menigomyelocele, Meningoencephalocele, and Anencephaly are all what type of defects?
neural tube related developmental
What occurs when the neural tube doesn’t form all the way to the bottom, due to folic acid deficiency
Spina Bifida
What neural tube deficiency is characterized by an extrusion of arachnoid and dura mater out of the head
Meningocele
What neural tube deficiency is characterized by an extrusion of neural tissue and all three meninges out of the head?
menignomyelocele
What neural tube deficiency is characterized by an extrusion of a ventricular cistern plus neural tissue?
menigoencephalocele
What neural tube deficiency is a fatal defect characterized by lack of development of the cranium and brain?
anencephaly
What neural tube defects are considered mild?
Spina Bifida and Meningocele
What neural tube defect is considered slightly more severe?
meningomyelocele
What neural tube defect is considered most severe but not yet fatal?
meningohydroencephalocele
What neural tube defect is considered fatal?
anencephaly
What determines the severity of the neural tube defect?
The amount of tissue extruding out
Neural crest cells may also be referred to as:
- ectomesenchyme
- neuroectoderm
All neural tube defects occur in what stage of human development?
proliferation period
If we are talking about oral-facial development in regard neural crest cells, what stage of human development are we referring to?
embryonic period
Around what day of development do we see the rostral neuropore closing, formation of heart prominence and somites and formation of caudal neuropore?
~day 24
Around what day of oral-facial development do we see the hyoid arch begin to form and when is it completely formed?
~24 days; ~26 days
Around what day of oral-facial development do we see formation of the mandibular arch, forebrain prominence, tail, and 3rd brachial arch?
~day 24
Around what day of oral-facial development do we see formation of the 4th brachial arch, the lower limb bud, the lens placode, and the upper limb bud?
~day 28
Everything from the neck up to the ear are derived from the:
pharyngeal arches
The pharyngeal arches can be compared to a stack of onion rings, and each ring contains:
A blood vessel, its own cranial nerve, and often will form its own cartilage
During oral-facial development (embryonic period), the 1st brachial groove will develop into:
external auditory canal
During oral-facial development (embryonic period), the 1st brachial pouch will develop into:
eustachian tube
During oral-facial development (embryonic period), the 2nd brachial pouch will develop into:
palatine tonsils
During oral-facial development (embryonic period), the 3rd brachial pouch will develop into:
inferior parathyroids/thymus
During oral-facial development (embryonic period), the 4th brachial pouch will develop into:
superior parathyroids/ultimobranchial body
Around what day of oral-facial development do the eyes and ears begin to form?
~41 days
Between the 3rd and 9th month of development, describe the head and body growth of the fetus:
Head stays the same size while the body continues to grow larger
At month 3 or fetal devleopment, the head to body ratio is:
50/50
List the processes formed during the development of the face:
- mandibular process
- maxillary process
- lateral nasal process
- median nasal process
In oral-facial development the oral cavity is known as:
stomodeum
What connects the oral and nasal facial processes?
philtrum
Clefts can be:
- palatal
- soft tissue
- lip
- nasal
What may cause a palatal cleft?
improper descending of the tongue
The palatal shelves fuse at the
junction of the primary palate
Fusion of the medial nasal process and maxillary process normally occur at _____ of gestation.
5-6 weeks
Defective fusion of the ____ process with the _____ process results in cleft lip
medial nasal process; maxillary process
Defective fusion of ____ results in a cleft palate
palatine shelves
Fusion of the palatine shelves normally begins during the ____ week and is completed by the ____ week.
8th week of gestation; 12th week of gestation
45% of all clefts are:
combine cleft lip/cleft palate
30% of all cleft cases are:
isolated cleft palate
25% of all cleft cases are:
isolated cleft lip
The incidence of clef lip/celft palate is:
______ births in Chinese, Japanese, and Native American populations
_____ births in Caucasian populations
______ births in Afro-American populations
1:500
1:700
1:500
The incidence of cleft palate alone is:
1:2500 births
If one child is born with a cleft lip, is a _____ chance of a second child exhibiting the same defect
40%
Known teratogens involved in congenital malformations:
drugs, chemicals, and radiation
What chemicals are known teratogens that are involved in congenital malformations: (2)
methylmercury and polychlorinated biphenyls
List the drugs that are known teratogens involved in congenital malformations: (10)
- ethanol
- tertracycline
- dilantin
- lithium
- methotrexate
- warfarin
- thalidomide
- androgens
- progesterone
- retanoic acid
During oral-facial development, what may develop at the line of fusion between the palatine shelves and primary palate?
Nasopalatine Duct Cyst
Small depression at the very back of the tongue:
foramen cecum
The location in which the thyroid gland forms during oral facial development:
foramen cecum
The 2nd brachial arch on the outside overgrows the 3rd and 4th arches to form a:
cervical sinus
During what week of development does the cervical sinus (derived from the 2nd brachial arch) get resorbed?
7th week
Failure of resorption of the cervical sinus results in formation of:
Lateral cervical cyst/brachial fistula
A lateral cervical cyst or brachial fistula will typically form along what muscle?
sternocleidomastoid
The first brachial arch forms lateral brachial swellings which ultimately form the:
anterior part of the tongue
The 1st brachial arch is innervated by:
cranial nerve 5
The 2nd brachial arch gives ____ to the tongue
innervation
The 3rd and 4th brachial arch form the:
posterior portion of the tongue
If the embryonic precursor is brachial arch #1, the intermediate structures include: (3)
- median tongue bud
- foramen cecum
- lateral lingual swellings
If the embryonic precursor is brachial arch #1 and the intermediate structures include the median tongue bud, foramen cecum, and the lateral lingual swellings, the adult structure is: (3)
- overgrown by lateral lingual swellings
- origin of the thyroid ectoderm
- anterior 2/3 of the tongue
If the embryonic precursor is brachial arch #2, the intermediate structures include:
copula/tuberculum impar
If the embryonic precursor is brachial arch #2 and the intermediate structures include copula/tuberculum impar, the adult structure includes:
overgrown by hypobrachial eminence
If the embryonic prescursor is brachial arch #3, the intermediate structures include:
hypobrachial eminence
If the embryonic prescursor is brachial arch #3, the intermediate structures include the hypobrachial eminence the adult structures include:
posterior 1/3 of tongue
If the embryonic precursor is brachial arch #4, the intermediate structures include:
minor contributions to the hypobrachial eminence
If the embryonic precursor is brachial arch #4, the intermediate structures include minor contributions to the hypobrachial eminence, the adult structures include:
none
which brachial arches contribute to the most to the tongue?
brachial arches 1 & 3
Identify the cranial nerves responsible for innervation to each brachial arch:
Arch #1:
Arch#2:
Arch#3:
Arch#4:
Arch#6:
1.Trigeminal
2. Facial
3. Glossopharyngeal
4. Vagus
6. Hypoglossal
Brachial arch #1 is innervated by the trigeminal nerve which provides:
sensory to the anterior 2/3 of tongue
Brachial arch #2 is innervated by the facial nerve which provides:
Taste (special sensory) to anterior 2/3 via chorda tympani branch
Brachial arch #3 is innervated by the glossopharyngeal nerve which provides:
sensory to the posterior 1/3 of the tongue
Brachial arch #4 is innervated by the vagus nerve which provides:
sensory to the extreme posterior 1/3 via the superior laryngeal branch
Brachial arch #6 is innervated by the hypoglossal nerve which provides:
Motor to all tongue muscles
Failure of the thyroglossal duct to involute may result in:
Thyroglossal duct cyst
A thyroglossal duct cyst is usually found:
around the midline
Failure of the thyroid gland to involute at all will result in:
ectopic lingual thyroid
Thyroid tissue sitting on top of the tongue due to failure of involution:
ectopic lingual thyroid
The mandible, maleus, and incus are derived from:
Meckel’s cartilage (1st brachial arch)
The stapes, styloid process, stylohyoid ligament and the lesser horn of hyoid are derived from:
Reichart’s cartilage (2nd brachial arch)
The greater horn of Hyoid is derived from cartilage from the:
3rd brachial arch
Thyroid cartilage is derived from cartilage from the:
4th brachial arch
The development of the external ear occurs from 6:
auricular hillocks
