Term
When is the Embryonic Period?
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Definition
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Term
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Definition
| The discharge of one mature oocyte and 3 polar bodies. |
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Term
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Definition
| A cell within a morulla. Rapidly dividing |
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Term
| Outside layer and inside layer of morula? |
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Definition
Outside - trophoblast
Inside - Embryoblast |
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Term
What is the blastocyst cavity?
When is it formed?
What else happens concurrent with blastocyst formation? |
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Definition
Blastocyst cavity is formed from fluid penetrating between the embryoblast and trophobast layer.
Forms around days 5-6 which is right around implantation |
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Term
| How do you make dizygotic twins? |
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Definition
| Two oocytes fertilized by two seperate sperm. |
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Term
| When does the split usually occur to form monozygotic twins? |
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Definition
May seperate anytime from blastocyst to bilaminar disc.
Most often occurs during early blastocyst stage.
When they seperate determines placenta arrangment. |
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Term
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Definition
| Pyopagus is the incomplete seperation of twins at the sacrum. |
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Term
| Where do most ectopic pregnancies occur? |
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Definition
| 95% occur in the uterine tube. |
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Term
| When does the bilaminar disc form and what layer of cells for the bilaminar disc layers? |
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Definition
| Forms during the second week and the embryoblast develops into epiblast and hypoblast layers. |
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Term
| What cavity does hypoblast surround? |
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Definition
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Term
| What cavity does the epiblast cells line? |
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Definition
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Term
| Name the cells of the epiblast layer that border the amniotic cavity and the cytotrophoblasts |
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Definition
| amnioblasts. special type of epiblast cell. |
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Term
| What is gastrulation and when does it occur? |
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Definition
Gastrulation is the process of epiblast layer cells invaginating and migrating into the primitive pit/streak to form endoderm and mesoderm
Occurs during the third week of development |
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Term
| How does gastrulation form the endoderm? |
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Definition
| invaginating epiblast cells displace hypoblast cells. |
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Term
| What embryological structure will give rise to the oral cavity? |
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Definition
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Term
| What embryological region provides head development signals? |
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Definition
| Anterior visceral endoderm. |
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Term
| Define Holoprosencephaly and cite its major cause |
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Definition
| Holoprosencephaly is as deficiency in midline cranial and fascial structures usually caused by high doses of alcohol |
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Term
| Define Sirenomelia and cite its major causes |
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Definition
Sirenomelia (aka caudal dysgenesis) causes deficient or absent lower limbs
Caused by insufficient migration of epiblast cells caudally.
Renal agenesis might also be present |
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Term
| Define Sacrococcygeal teratoma and cite its causes |
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Definition
tumor of sacrococcygeal area caused by remnant of the primitive streak. They will contain various forms of tissues
This is the most common tumor of newborns |
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Term
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Definition
| Transposition of all organs to the other side of the body. |
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Term
Define the embryonic period
What are its major characteristics? |
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Definition
Weeks 3-8
Period of tissue and organ formation to become recognizably human
Period of most susceptibility to congenital malformations. |
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Term
| What does ectoderm give rise to? |
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Definition
CNS
PNS
Sensory epithelium of eye, nose, ear
Skin and its derivatives
Pituitary gland
Tooth Enamel |
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Term
| What is the Neural Plate and what is it the beginning of? |
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Definition
| The neural plate is a cephalic thickening of ectoderm that is the beginning of the formation of the CNS |
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Term
| When does the caudal and cranial neural tube close? |
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Definition
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Term
| Where are neural crest cells located? |
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Definition
| They are a band of cells along the junction where the neural tube closes and the surface ectoderm |
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Term
Name neural crest derivatives
9 Things |
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Definition
ANTERIOR SKULL
Dorsal root ganglia
Sensory ganglia for CN V, VII, IX, and X
Autonomic ganglia
Adrenal Medulla
Melanocytes
C Cells of Thyroid
Conotruncal septum of heart
Schwann Cells |
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Term
| What cells are found in pharyngeal arches? |
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Definition
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Term
| From medial to lateral, what are the 3 parts of the mesoderm |
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Definition
| Paraxial, intermediate, and lateral plate mesodem |
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Term
| What are the segments of the paraxial mesoderm? |
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Definition
| Somites. Usually 42-44 somites |
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Term
| What does the intermediate mesoderm differentiate into? |
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Definition
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Term
Lateral plate mesoderm gives rise to?
What seperates these structures? |
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Definition
Parietal and visceral layers
Seperation between them is the intraembryonic covity. |
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Term
| what are the 3 seperations of the intraembryonic cavities? |
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Definition
| pericardial, pleural, and peritoneal cavites |
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Term
Where does blood vessel formation first occur?
Where does it occur next? |
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Definition
Starts in extraembyonic mesoderm around the yolk sac
Later, forms in the lateral plate mesoderm. |
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Term
What is the function of the liver during the embryonic period?
What happens after the embryonic period? |
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Definition
| The liver is colonized by hematopoeitic cells by week 6 and remains the major blood producer until seventh month when bone takes over |
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Term
| What is the significance of lateral folding of the trilaminar disc and what is it caused by? |
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Definition
lateral folding is caused by growth of somites.
It closes the ventral body around the umbilical ring and pulls the amniotic cavity around the embryo. |
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Term
| What creates the head and tail fold? |
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Definition
| growth of the brain vesicles and lenthening of embryonic axis |
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Term
| What are the boundaries of the foregut? |
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Definition
| endodermal derived tube from the buccopharyngeal membrane to the liver bud. |
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Term
| What gives rise to the respiratory system? |
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Definition
| forms from an outgrowth of the ventral wall of the foregut. |
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Term
| What is the fetal period and what occurs during this time? |
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Definition
| weeks 9 till birth and is a time of growth and functional maturation |
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Term
| When are the primary ossification centers present? |
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Definition
| start at week 8 and are in all long bones by the 12th week. |
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Term
| What are the two cell types formed from trophoblast cells? |
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Definition
| the outer layer is the syncytiotrophoblast and inner (fetal side) layer is the cytotrophoblast. |
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Term
| How do cells of the syncytiotrophoblast form? |
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Definition
| syncytiotrophoblast cells from from invaginating cytotrophoblast cells. |
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Term
| What is the decidua reaction? |
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Definition
| The decidua reaction is when the uterus becomes loaded with glycogen and lipids, and becomes edematous. |
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Term
| What is the difference between lacunae and sinusoids? |
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Definition
Lacunae are large spaces formed from syncytiotrophoblasts.
Sinusoids are maternal capillaries that fill the lacunae with materal blood that are present within the uterus. |
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Term
| How does the secondary yolk sac form? |
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Definition
| by pinching off of the hypoblast to form the secondary (definitive) yolk sac and the chorionic cavity. |
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Term
| How does the amnion and yolk sac remain attached to the chorion? |
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Definition
| Via the connecting stalk which will differentiate into the umbilical cord. |
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Term
| What is the outer cytotrophoblast shell? |
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Definition
| Forms during the third week when cytotrophoblast cells surround the syncytiotrophoblast and firmly attach it to the endometrium. |
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Term
| What seperates maternal and fetal blood? |
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Definition
| the villi that bathe in maternal blood are seperated by fetal capillary endothelium and syncytiotrophoblast (these two together are referred to as the placental barrier) |
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Term
| What is the chorion frondosum? |
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Definition
| the fetal portion of the placenta |
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Term
| What is the decidua basalis? |
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Definition
| The maternal part of the placenta overlying the chorion frondosum |
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Term
| What secretes hCG and what does it do? When is it not needed? |
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Definition
hCG is secreted from the syncytiotrophoblasts to maintain the corpus luteum so that it produces enough progesterone to maintain the pregnancy.
In the fourth month it can be removed due to the ability of the placenta to produce enough progesterone. |
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Term
| Why does the placenta produce estrogen? |
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Definition
| To stimulate uterine growth and mammary development |
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Term
What are the uses of amniotic fluid?
5 functions |
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Definition
shock absorption
Preventing embryonic adhesion to amnion
Allow fetal movements
Allow fetal growth (lung expansion)
Provides barrier to infection |
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Term
| What causes polyhydramnios? |
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Definition
| Can be caused by anencephaly or intestinal atrasia (incomplete connections). This prevents swallowing and absorption which will cause fluid excess |
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Term
| What causes oligohydramnios and what are its possible consequences? |
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Definition
| Can be caused by renal agenisis or amnion rupture and can cause clubfoot or lung hypoplasia. |
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Term
| What is each pair of somites innervated by? |
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Definition
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Term
| What part of the somite forms vertebrae? |
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Definition
| Sclerotome cells migrating to surround the notochord. |
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Term
How is the body of a vertebrae formed?
Therefore, how is an intervertebral disc formed? |
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Definition
the body of a vertebrae is formed by half cephallicaly from the sclerotome above and the caudal half by the sclerotome below.
Therefore, interverebral discs form from the original divisions between the caudal and cephalad halves of a sclerotome |
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Term
| What is characteristic of all spina bifida cases? |
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Definition
The vertebral arches of several adjacent vertebrae do not close.
If covered by hair and skin --> occulata
If exposed --> cystica |
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Term
| What spinal segments correspond to the upper and lower limb buds? |
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Definition
Upper limb - C5-T1
Lower Limb - L2-S3. |
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Term
What is the apical ectodermal ridge?
What is the progress zone? |
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Definition
| Thickened ectoderm overlying mesenchyme mesoderm beneath. The AER activates the underlying tissue to divide rapidly and grow the limb. This area is known as the progress zone |
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Term
| How do hands and feet form? |
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Definition
| In the 6th week, handplates and footplates form. Mesenchyme condenses to form digital rays and apoptosis of webs create fingers and toes. |
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Term
| When do the limbs rotate? |
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Definition
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Term
Define Amelia and Meromelia
What is it caused by? |
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Definition
Total (amelia) and partial (meromelia) absence of an extremity.
Caused by maternal thalidomide ingestion. |
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Term
How does the cranial vault form?
What is the skullcap called? |
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Definition
Skull cap forms intramembraneously
The skullcap is called the calvaria. |
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Term
| What is the most common form of craniosynostosis? |
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Definition
| Scapholocephaly - premature fusion of the sagittal structure. |
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Term
What types of mutations are related to mutated fibroblast growth factor receptors?
Main example of disease? |
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Definition
FGFR are shown to cause syndromes involving craniosynostosis and limb deformities.
Achondroplasia. |
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Term
| Name the parts of the chondrocranium cartilages |
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Definition
Parachordal cartilage - base of occipital
Hypophyseal cartilage - body of sphenoid
Trabeculae cranii - body of ethmoid
ala orbitalis - lesser wings of sphenoid
Ala temporalis - greather wings of sphenoid
Periotic Capsules - parts of temporal bone |
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Term
| What determines the muscle type each muscle forms into? |
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Definition
| The type of neuron innervating it. |
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Term
| what is a complete absence of the abdominal musculature system called and what is it caused by? |
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Definition
| Prune belly syndrome - associated with urinary tract obstruction and pulmonary hypoplasia due to oligohydramnios |
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