Chapter 5 Flashcards
(Fate Map)
Cells that migrate at the lateral edges of the node and from the cranial end of the streak become the?
A. Paraxial mesoderm
B. Intermediate mesoderm
C. Lateral Plate mesoderm
A
(Fate Map)
Cells migrating through the midstreak region become the?
A. Paraxial mesoderm
B. Intermediate mesoderm
C. Lateral Plate mesoderm
B
(Fate Map)
Cells migrating through the more caudal part of the streak form the?
A. Paraxial mesoderm
B. Intermediate mesoderm
C. Lateral Plate mesoderm
C
(Fate Map)
Cells that migrate through the caudalmost part of the streak contribute to the?
Extraembryonic mesoderm
Expansion of the embryonic disc occurs mainly in the
A. Caudal region
B. Cephalic region
B. Due to the continuous migration of cells from the primitive streak region in a cephalic direction
Germ layers begin specific differentiation by the middle of:
A. 2nd week
B. 3rd week
C. 4th week
D. 5th week
B
Caudal differentiation begins by the end of the
A. 3rd week
B. 4th week
C. 5th week
B
A deficiency in the midline in craniofacial structure results to?
Holoprosencephaly. Forebrain is small, the two lateral ventricles often merge into one, the eyes are closed together (hypotelorism)
(Clinical Correlates)
Insufficient mesoderm is formed in the caudalmost region of the embryo. Urogenital system and lumbosacral vertebrae abnormalities ensue.
Caudal dysgenesis or sirenomelia.
Defects: hypoplasia and fusion of the lower limbs, vertebral abnormalities, renal agenesis, inperforate anus and anomalies of the genital organs
These are clusters of ploripoitent cell that proliferates and form tumors in the saccroccygeal region
Sacrococcygeal teratoma. The most common tumor in newborns
True or False.
Teratomas arise from primordial germ cells that fail to migrate to the gonadal ridge
True
(Birth Defects Associated with Laterality)
Refers to the normal positioning of the internal organs
Situs solitus
Refers to the condition where the positioning of all organs is reversed in a mirror image arrangement
Situs inversus
One or more organs are abnormally reversed in position or isomerisms or iversions are present
Situs ambiguus or heterotaxy
There is a failure to properly establish the L-R axis
Laterality defects. Patients do not have complete situs inversus but aolear to ve predominantly bilaterally left-sided or right-suded
(Spleen reflects differences)
Left sided bilaterality have
A. Polysplenia
B. Asplenia
C. hypoplastic spleen
A
(Spleen reflects differences)
Right sided bilaterality have
A. Polysplenia
B. Asplenia
C. Hypoplastic spleen
B and C
Individuals with this condition do not have a high risk for having other congenital abnormalities but have agreater risk for a heart defect or severe cardiac malformation. They have bronchiectasis (20% of px) and chronic sinusitis due to Kartagener Syndrom (abnormal cilia)
Situs inversus
Patients with this conditioin have a wide variety of other birth defects - midline malformations, neural tube defects, cleft palate, anal atresia etc. the heart exhibits more laterality than most organs
Situs ambiguous
Mutations in what transcription factor causes X-linked heterotaxy
ZIC3 (zinc finger transcription factor). Birth defects include neural tube defects, limbs, ompholocoelenand most have severe heart malformations
This neurotransmitter is an important signal molecule for establishing laterality
Serotonin (5-HT)
These drugs increases risk if having different types of heart malformations and multiple other birt defects
Selective serotonin reuptake inhibitors (SSRIs)
Prozac, Paxil, Zoloft, Lexapro, Celexa
The trophoblast at the beginning of the third week is characterized by the
A. Primary villi
B. Secondary villi
C. Tertiary villi
A. This consists of a cytotrophoblastic core covered by a syncytial layer.
The core of the primary villi is penetrated by mesodermal cells and grow toward the decidua, this neiwly formed structure is known as
Secondary villi
(By the end of 3rd week)
Mesodermal cells in the core begin t8 differentiate into blood cells and small blodd vessesl, forming the villous capillary system. The villus is now known as
Tertiary villus or definitive placental villus
The heart begins to beat in what week
Fourth
Cytotrophoblastic cells establish contact with the neighbouring villous stems forming the
Outer cytotrophoblastic shell. This shell surrounds the trophoblast entirely and attaches the chorionic sac firmly to the maternal endometrial tissue
The part of the endometrium where the placenta will form is called
Stem or anchoring villi. Those that branch in the sides are free or terminal villi where exchange of nutrients and other factors occur
The embryo is attached to its trophoblastic shell by the
connecting stalk
It forms the connection between the placenta and embryo
Umbilical cord. Developed from the connecting stalk
Epiblast cells move inward (invaginate) forming what germ cell layer/s
Endoderm and mesoderm
Cells that do not migrate through the streak but remain in the epiblast form what layer of the germ cell
Ectoderm
Most characteristic event during 3rd week of gestation
Gastrulation
Begins with the formation of primitive streak on the surface of epiblast
Cell migration and specification is controlled by the
FGF 8. Synthesized by streak cells
FGF 8 controls cell movement by
A. Down-regulating E-cadherin
B. Up-regulating E-cadehrin
A.
E-cadherin is a protein theat binds the epiblast together
E-cadherin controls cell specification into the mesoderm by regulating which expression
A. BRACHYURY (I) expression
B. BRACHYURY (T) expression
C. BRACHYURY (H) expression
B. BRACHYURY (T) expression
Temporarily connects the aminiotic and yolk sac cavities
Neurenteric canal
Formed at the caudal end of the embryonic disc that is similar as the oropharyngeal membrane
Cloacal membrane
A small diverticulum formed by the posteror wall of the yolk sac
Allantois or allontoenteric diverticulum. Appears around the 16th day of development
