Review Flashcards
(43 cards)
How many pairs of somitomeres have formed at day 20 and where do the somites form?
- 20 pairs of somitomeres and the first pair of somites forms behind (caudal to) the 7th pair of somitomeres ate the expense of the 8th pair of somitomeres.
- 11 pairs of somitomeres are kept constant at the caudal end of the paraxial mesoderm.
What factor is used in the permanent cartilage pathway?
Sox-9
What factors are used in the endochondral bone pathway?
Runx-2, ihh, and BMP-6
Where do the Centrum, Neural Arches, and Costal processes/Ribs arise from?
Centrum:
Derived from ventral and medial parts of paired sclerotomes.
Neural Arches:
Arise from dorsal regions of sclerotomes
Costal processes/Ribs:
Proximal development depends on expression of myotomic myogenic factors, Myf-5 and Myf-6.
Distal development depends on BMP signals from somatopleural mesoderm.
What are vertebral boundaries made by?
Occipital-cervical boundary: Hox3
Cervical-thoracic boundary: Hox6
Attached-floating ribs boundary: Hox9
What are results of a single Hox gene knockout, Knockout of all Hox 10 paralogues, Knockout of all Hox 11 paralogues, and mutation of a single Hox gene?
Single Hox knockout: minor morphological effects notes
All 10: ribs on lumbar and sacral vertebra
All 11: Sacrum doesn’t form
Single mutation of Hox leads to minor mutations anatomically.
What are the characteristics of the clavicle?
Arises from neural crest and one of first bones to become ossified.
What are the parts of the viscerocranium?
Cartilaginous portion:
Pharyngeal arch I: (meckel’s cartilage, malleus, incus)
Pharyngeal arch II: (Reichert’s cartilage, stapes, styloid)
Membranous portion:
Part of temporal, zygomatic, maxillary, nasal, lacrimal, palatine, vomer, pterygoid plates, mandible, tympanic ring.
They elongation of primary ossification centers is due to what?
Shh
What are the functions of the placenta?
Diffusion of oxygen and carbon dioxide
Diffusion of foodstuffs
Excretion of waste products
What transcription factors are used for initial signaling for endoderm formation during gastrulation?
Depends on Nodal expression during gastrulation
Anterior-posterity gradient
Higher levels of nodal anteriorly
Lower levels of nodal + presence of FGF-4 posteriorly
Posterior gut expresses Cox-2
Anterior gut expresses Hex, Sox-2, Foxa-2
Refinement is due to Hox genes
Describe early heart formation:
Cardiac Tubes and Proepicardial primordium
Bilaterally paired tubes that form from the cardiogenic mesoderm:
-Fuse beneath foregut to form single tube
Each tube consists of outer and inner layer:
- Outer layer will form myocardium
- Inner layer will form endocardium
Cardiac jelly forms between the two layers:
-Specialized extracellular matrix
Proepicardial primordium:
-Source of pericardium and myocardial fibroblasts
How do the early heart forming cells migrate?
Cells migrating through anterior primitive streak:
-Outflow tract
Cells migrating through middle of the streak:
-Form ventricles
Cells migrating through streak most posteriorly:
-Form atria
NECESSARY GENES:
Nkx2-5, MEF2, GATA4
The cranial and caudal extent of the intermediate mesoderm is dependent on what?
Hox-4 through Hox-11
How is intermediate mesoderm formed?
Responds from BMP from lateral ectoderm and activin from paraxial mesoderm.
In segmentation clock, how are the somites formed?
At each critical location that will serve to divide adjacent somites, lunatic fringe will become concentrated at future anterior border of a somite, and c-hairy will be concentrated at the future posterior border of a somite.
How does the wavefront mechanism?
Increased FGF-8 caused mitosis in mesenchymal cells in posterior primitive streak, while increased retinoic acid more anteriorly opposes the action of FGF-8.
Remember, mesoderm originates from epiblast, passes through primitive streak as bottle cells, spreads laterally, and establishes a continuous layer between ectoderm and endoderm.
JUST KNOW THIS>
Describe the organization of the somite in the dermomyotome.
Shh signaling from the notochord and Wnt signaling from the dorsal neural tube create a balance that causes the myotome portion to commit to the myogenic lineage.
- Noggin inhibits BMP-4, which would normally inhibit myogenesis.
- BMP-4 produced by the lateral plate suppresses myogenesis in the ventrolateral dermomyotome and stimulates cells from this area to migrate from the somite into the limb bud.
FGF from the myotome signals the sclerotomes to produce sclera is, which causes the anterior and posterior borders of each somite to form the syndetome which is the precursor of tendons.
What the extraembryonic tissues and what makes up the Fetal-maternal interface?
Extraembryonic tissues:
- Amnion(Inner cell mass: epiblast derivative) Ect, Mes
- Yolk sac (inner cell mass: hypoblast derivative) End,Mes
- Chorion (part of fetal maternal interface) Ect, Mes
- Allantois (inner cell mass, interfaces with placenta via umbilical cord) End,Mes
Fetal-maternal interface:
- Placenta (Trophoblast derivative)
- Chorion (trophoblast derivative)
Differences between Early placenta and Late placenta.
Early:
- Thick
- Permeability low
- Small surface area
- Total diffusion conductance is minuscule
Late:
- Thin
- Permeability high
- Large surface area
- Large increase in placental diffusion
What are the functions of the HcG?
-Prevents involution of corpus luteum
-causes CL to increase secretion of progesterone and estrogens.
-Causes increased growth in CL
-Exerts interstitial cell-stimulating effect on testes of male fetus:
—Results in production of testosterone until birth
What are the functions of Progesterone?
- Causes decidual cells to develop in the endometrium
- Decreases contractility of pregnant uterus
- Increases secretions of Fallopian tubes and uterus
- May work with estrogen to prepare breasts for lactation
What after the functions of Human Chorionic Somatomammotropin?
- Causes decreased insulin sensitivity and decreased utilization of glucose by mother
- General metabolic hormone
