Lecture 2 Flashcards
Klinefelter Syndrome
Males that have an extra x in most of their cells, the more x’s the more severe, 1:500-1,000. Penetrance, women over 35 have a higher incidence
Klinefelters clinical appearance:
Gynecomastia (man boobs),max and mand prognathism (causes cross bits and malocclusion). Permanent crowns larger than usual. Inc pulmonary and autoimmune disorders, diabetes mellitus in 8%, high incidence of cleft palate.
Klinefelters clinical management:
Bolton discrepancy (tooth size ration wont accommodate a proper occlusal relationship) growth abnormalities, max and mand prognathism, Taurodontism (extension of pulp chamber below alveolar crest, failure of hertswig epithelial shift to invaginate at proper level, enlarged pulp chamber, apical displacement, no constriction at CEJ, caries control important (due to potential calcification and extra canals)
Turners Syndrome:
One normal x and the other missing/altered. 1:2,500 females. Webbed neck, low hairline on back of neck, lymphedema, early loss of ovarian function, 1/3-1/2 with heart defect. Short stature defect on SHOX gene (essential for skeletal development especially in arms and legs.
Clinical management of syndromic patients
Good understanding of the syndrome is important, congenital heart defects so consult with cardiologist, mental handicaps, need realistic goals for oral problems,
Cleavage
Subdivides zygote without increasing in size. Starting at 8 cell size, blastomere begins to flatten. Outer surface become convex and inner surfaces become more concave. Called compaction and involves changing the blastomere cytoskeleton.
Preimplantation genetic diagnosis (PGD)
Remove a blastomere and screen for aneuploidy or translocation with karyotype analysis. Done on old pts and high risk
Trophoblast
part of the cleaving embryo, peripheral outer cell mass, placenta and associated membranes
embryoblast
part of cleaving embryo, inner cell mass that gives rise to embryo proper
day 4
morula consist of 30 cells. Trophoblast has a sodium potassium ATPase pump that pumps in ions and water follows. Fills a large cavity called the blastocyst cavity
blastocyst
has the fluid filled cavity. The inner cell mass forms the embryonic pole and the other end is abembryonic pole.
Zona hatching
Blastocyst’s zona pellucida degenerates and replaced by a underlying layer of trophoblast cells called the cytotrophoblast
Syncytiotrophoblas
Trophoblast cells in contact with uterine wall lose cell membrane coalesce to form syncytium and implants into the uterine wall
Bilaminar embryonic disk
During the second week the embryoblast splits into epiblast (primary ectoderm) and hypoblast (primary endoderm)
Amniotic cavity
Appears day 8 as fluid collects between cells of epiblast and overlying trophoblast. A layer of epiblast cells expands toward the embryonic pole and differentiates into a thin membrane (amnion) separating the new cavity and from the cytotrophoblast. Remainder of epiblast and hypoblast now constitute a bilaminar disk which develops into embryo proper
Coagulation plug
Acellular material that seals the small hole where the blastocyst implanted.
Extraembryonic endoderm:
day 9 the hypoblast sends out a proliferation of cells that lines the cytotrophoblast. Completely surrounds the former blastocyst and is called the Heuser’s membrane
extra embryonic mesoderm
filling in between heusers membrane and the cytotrophoblast with loosely arranged cells
primary yolk sac
blastocyst cavity after heusers membrane is formed
cytotrophoblastic lacunae
day 11-13 anastamose with maternal capillaries and become filled with blood
extraembryonic coelom or chorionic cavity
12-13 days. extraembryonic mesoderm splits into two layers. seperates the embryo with its attached amnion and yolk sac from the outer wall of the blastocysts
endodermal lining of the definitive yolk sac
breaks up the primary yolk sac, happens on day 12, migrates over the inside of the extraembryonic mesoderm
major structure associated with the developing embryo throught eh 4th week
definitive yolk sac-primordial germ cells first identified in this wall
primitive streak
primitive groove, pit, and node. beginning of third week
gastrulation
cell migration, invagination and ingress. day 16 the epiblast cells near the primitive streak begin to proliferate, flatten, and lose their connections with each other. develop long flat foot like processes (pseudopodia) which allow them to migrate through primitive streak
definitive endoderm
invading epiblast cells replace the hypoblast- gives rise to gut and gut derivatives
intraembryonic mesoderm
invading epiblast cells form a middle layer. migrate laterally (somites= vertebral column, skeltal muscle, and dermis) and cranially
notchordal process
hollow, mesodermal cells migrates cranially on day 17.
prechordal plate
thickening of endodermal layerwhich is formed my mesodermal cells. gives rise to the endodermal layerof the orppharyngeal membrane (forms the mouth and participates in patterning of the cranial nerve tube.
ectoderm
once ingress of epiblast is complete its called ectoderm and bilaminar disk is now trilaminar
bilaminar membrane
fusion of ectoderm and endoderm. 3rd week.
buccopharyngeal membrane
cranial membrane
cloacal membrane
caudal membrane
caudal eminence
day 26 the remnants of primitive streak leave behind a caudal midline mass of mesoderm
notochordal plate
days 16-22 the hollow notochordal process fuse with the underlying endoderm in a caudal to cranial manner. disengages from the endoderm to form notochord
neural plate
thickening of the ectoderm on either side of the midline, cranial to the primitive node.wider at cranial portion (for brain) day 22 the neural plate represents about 25% of the length it will be. day 23-24 its 50%.
neurulation
fourth week, converts neural plate into a hollow tube which sinks and differentiates into brain and spinal cord
neural groove
crease above the notochord. crease ventrally to form the neural tube and canal
neural crest cells
day 24. detach from neural tube and undergo epithelial to mesenchymal transformation, and migrate to different parts of the body where they make up a variety of structures. the route and where they stop migrating determines what they become.
day 22
neural groove begins to close, starts in middle and goes laterally. 24 cranial closes and 26 caudal closes. then neural tube is covered dorsally by mesenchyme
main force for folding
growth of different embryonic structures. embryonic disc and amnion grow while yolk sac says the same. notochord, neural tube, and somites stiffen so the main force is on the thin flexible disc.
oropharyngeal membrane
cranial rim of embryonic disc, future mouth
cardiogenic area
horshoe shaped, cranial to oropharyngeal membrane. gives rise to heart
septum transversum
day 22, thickened bar of mesoderm, just caudal to cranial margin of embryonic disc, diaphragm, stomach, duadenum
cranial rim
face, neck, chest
caudal rim
contains coacal membrane, folds ventrally
body folding result
tube inside a tube is established. ectoderm on outside and endoderm on inside
anencephaly
upper part of neural tube fails to close- neural tube defect. missing forebrain, cerebrum, skull and skin of head
spina bifida
lower portion of neural tube fails to close, physical and mental disabilities. genetic, nutriotional, environmental. folic acid/ vit b
encephalocele
failure of skull to close completely, brain squishes out somehwere on head. rare 1;500. girls more likely occcipital, boy more likely front of skull, north america more common back, SE asia more comman front. if meninges involved its an miningoencephalocele. with CSF its meningiohydroencephalocele. tx: surgery
myelomeningoecele
most serious type of spina bifida, sac of fluid with spine and nerves out the opening, moderate to sever disabiltes,
meningiocele
spina bifida, just sac of water, minor disabilties
spina bifida occulta
small gap but no pouch, no disabilites
pharyngeal arches
1,2,3,4,6. internal endoderm pouch (4), external ectoderm cleft (4), mesenchymal core (somatic mesoderm (artery and muscle) and neural crest mesencyme(bone cartilege and CT)
pharyngeal membrane
area between clefts and pouches, both endoderm and ectoderm
1st pharyngeal arch
4th week. maxx and mand process. max: cartilage= palatopterygoquadrate forms incus and alisphenoid (eye)
mandible cartilege (meckels) neural crest, malleous.
Somatic mesoderm: maxillary artery and muscles of mastication
pharyngea membrane: tympanic membrane
NC mesenchyme; max, mand, zygomatic, squamous.
trigeminal nerve 5
2nd pharyngeal arch
cartilege= stapes, styloid process, stylohyoid, lesser horn and upper rim of hyoid.
stapedial artery
muscles of facial expression, digastic (posterior), stylohyoid, stapedius muscles
facial nerve 7
failure of the sinus to obliterate leaves cervical cyst
3rd pharyngeal arch
cartilage: lower rim of hyoid bone (body) and greater horn
somatic mesoderm: stylopharyngeous muscle
common and internal corotid artery
glossophayrngeal nerve 9
fourth arch
arch of aorta, right subclavian, initial pulmonary arteries.
constrictors of pharynx, cricothyroid, and levater veli palatini
sixth arch
ducctus arterious, definitive pulmonary arteries.
intrinsic muscles of larynx
cranial nerves and arches
5,7,9,10 (superior laryngeal branch), 10 (recurrent laryngeal branch)
pharyngeal cleft 1
external auditory canal, preauricular cysts and fistulas. may threaten facial nerve
2,3,4 pharyngeal clefts
obliterated, can form cysts of fistulas along the anterior border of the sternocleidomastoid muscle
1 pharyngeal pouch
eustacian tube and middle ear cavity
2 pharyngeal pouch
crypts of the palatine tonsil, lymphocytes form the actual tonsil
3 pharyngeal pouch
dorsal/superior form inferior parathyroid glands
ventral/inferior form thymus
4 pharyngeal pouch
dorsal= superior parathyroid.
ventral=ultimobranchial body (induces migration of nearby NC cells into parafollicular cells of thyroid
thryoid gland
late 4 week. proliferate at foremen cecum, descends through thyroglossal duct, duct breaks down in 5 week. migrates till week 7. not from any arch, arises from midline thyroid diverticulum (endoderm) endoderm differentiate into follicular cells
issues: ectopic thyroid or MIDLINE cysts
