Embryology Flashcards
Face
mesenchyme for face region derived from
1) paraxial mesoderm
base +flat bones skull; voluntary m craniofacial region; dermis+CT of dorsal region head’ meningi caudal to prosencephalon
2) lateral plate of mesoderm
laryngeal cartilage (cricoid and arytenoid)+CT in region
3) neural crest (NC) cells from ectoderm of forebrain and hindbrain. migrate ventrally to pharyngeal arches, around forebrain and optic cup into face to form it= viscerocranium, parts of membranous and cartilaginous of neurocranium
(bone,tendon, dermis, pia, arachmoid, sensory n, glandular CT and dentin
4) ectoderm placodes + NC cells = neurons from 5,6,7,9 and 10 CN ganglia
- FORMATION OF PHARYNGEAL ARCH (rudimentary)
4th week, first appears as bars of mesenchymal tissue separated clefts (external) and puches (internal). pouches penetrate mesenchyme but no open common
4th week STOMODEUM form central part of face. 5 prominences/primordia are visible: x2mandibular and x2 maxillary prominence, frontonasal prominence (form 2 nasal p)
structure pharyngeal arch: mesenchymal and NC. outside is ectoderm and inside endoderm=epithelia
5th week: NASAL PLACODES appear on both sides frontonasal p by thickening endoderm. Invagination form of nasal placode ectoderm= NASAL PITS=NASAL PROMINENCE (med+lat).
next 2 weeks series developments
- maxillary p increases and grows medially= compression of medial nasal p (towards midline). cleft between lost+fuse= UPPER LIP
- LOWER LIP+JAW: mandibular p merges across midline
- maxillary p+ lat nasal separated by nasal lacrimal groove and endodermon grows + forms epi cord; canalization occurs =NASOLACRIMAL DUCT (on medial side of eye to inferior meatus of nose) widens LACRIMAL SAC
- maxillary p enlarge= CHEEKS+ MAXILLAE
-due to maxillary p growth towards midline causes 2 medial nasal p fuse= INTERMAXILLARY SEGMENT (6-7th week)
3 comp: labial (phlitrum of upper lip), upper jaw (four incisor teeth) and palatine (primary palate) *intermaxilalry segmentum continuous w nasal septum-dev frontal p (rostral part)
primary palate (intermax seg) main part is from two shelf like outgrowth maxillary p = PALATINE SHELVES (6th week) vertical position (obliquely+down)
- anteriorly, shelves flip up= horizontal : tongue drop, mandible grow forward and nasal septum prolongs
- shelves fuse= SECONDARY PALATE, SOFT PALATE
- incisive foramen separates 1+2 palate and uvula
- 10th week nasal septum fuses w 2 palate
pharyngeal arches+ pouches
first pharyngeal arch: trigeminal
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clefts
- anterior to incisive foramen= later cleft lip, cleft upper jaw or cleft between 1+2 palate
- posterior to incisive foramen: cleft 2 palate, cleft uvula
- combination of both
- unilaterally cleft lip (cheiloschisis unilateralis) (incomplete fusion of med + maxillary p)
- uni+bil cleft lip (cheilognathoschisis uni+bilateralis)= bilat common is male 80%
-cleft palate (palatoschisis) =common 67% female - unilateral everything (cheilognathopalatoschisis unilat)
facial clefts
- median cleft of lower lip+mandible
- oblique facial clefts (fail maxillary p + lat and med nasal p)
- macrostomia (lateral facial cleft)
- microstomia (excessive merge of mand+maxillary p)
- single nostril (one nasal placode developed)
- bifid nose (fail medial nasal p to merge completely)
Nasal cavities
formed by 5 prominence
- frontal p: forehead, bridge of nose, and med and lat nasal p
- med nasal p fuse= crest+tip of nose
- lat nasal p fuse= alae nasi
6th week: NASAL PITS (from nasal placodes) grow downwards+deepen (growth of nasal prominence penetrates mesenchyme);
forms ORONASAL MEMBRANE separate primitive nasal +oral cavity.
after breakdown, forms primitive choanae (each side of midline+behind 1 palate).
secondary palate forms= choanae is positioned at junction of nasal cavity +pharynx
paranasal air sinus develops diverticula of lat nasal wall+ extends to maxilla, ethmoid, sphenoid and frontal bones; Reach max size at puberty and contribute to face
Tongue
4th week
- primary pharyngeal arch = x2 lateral lingual swelling, medial lingual swelling and tuberculum impar
- secondary PA= copula
- third and partly fourth PA: hypobronchial eminence
- fourth= epiglottis +third median swelling
behind third median swelling = LARYNGEAL ORIFICE+ ARYTENOID SWELLING on both sides lingual swelling increase in size + overgrows tuberculum impar= ant 2/3 tongue. mucosa lining is from primary PA so inn is mandibular branch of V hypobronchial eminense overgrows copula. 2,3, part 4 form root/post tongue; third PA overgrows second= inn by glossopharyngeal n - general sen: ant 2/3 V; root 1/3 glossopharyngeal; special sensory ( taste) chorda tympani branch of facial n VII + vagus n X foramen cecum= thyroid gland (thyroglossal duct); terminal sulcus is fusion line epiglottis+ post tongue inn superior laryngeal (4 PA) occipital somites-> myoblast-> muscles tongue inn hypoglossal n XII
congenital malformations of tongue
ankyloglossia: tongue tied = tongue attached floor (frenulum)
macro+microglossia
cleft tongue: incomplete fusion of lateral lingual swelling
congenital lingual cysts and fistulas - remnants thyroglossoduct
Tooth
starts w interaction between oral epi+ underlying mesenchymal (NC derived). enamel knox reg tooth development (early) derived ameloblasts
6th week: DENTAL LAMINA c shaped, from basal layer of oral epi
8th week: DENTAL BUDS (10) -for permanent teeth at 3 months
10th week: deep buds invaginate = CAP STAGE
F: stimulate proliferation+condensation of mesenchyme in enamel organ to form DENTAL PAPILLAE
early bell stage:
ectoderm lining of dental cap -> ENAMEL ORGAN (outer+inner enamel epi w ameloblast+ stellate reticulum (reticular fibres)+ stratum intermediatum
surrounding mesenchyme condense around primordium tooth = DENTAL SAC
bells stage:
invagination dental papillae deepends= bell shape
cells in dental papillae form= DENTAL PULP (when first calcified matrix is at cusp)
- ameloblast induce surface mesenchymal cells of dental papillae-> ODONTOBLAST which forms predentin which stimulate inner ameloblast form ENAMEL
- rest of cells dental papilae form fibroblasts dental pulp
odontoblasts
- develop w assoc GER, GA, mito
- polarised cells (nucleus basally)
- odontoblasts process forms and enlarge secreting predentin
- initial enamel secreted, odontoblasts retreat dermal papillae as dentin and leave behind a single process= pyramidal TOME’S FIBERS
ameloblasts
- differentiate by reverse polarity, nucleus on opp side
- initial enamel secreted, retrates and secreting pole= TOMES FIBRES and both surfaces of process make crystals
- development of enamel depends on vasc+ transportation of inner ameloblast (reg by stratum intermediatum)
cells of enamel rods reduce enamel reticulum and degenerate outer ameloblast
- rod = one ameloblast but interrod = 4
root formation
EPI ROOT SHEATH= HERTWIG SHEATH forms from dental epi penetrating underlying mesenchyme w proliferating ameloblasts. sheath grows along papillae
cementum formation
inner dental sac cells-> CEMENTOCYTES (cementum=specialised bone)+deposition of dentin
outer dental sac cells-> periodontal lig+ partly jaw bone
dentition
prenatal period=develop
birth-4y: root finish
mixed dentition 6-12y deciduous teeth w permanent teeth (erupt+shedding)
sooner in Females + mandibular teeth erupt b4 maxillary
eruption: central incisor, lateral incisor, first molar, canine and second molar look at pic
teeth anomalies
numerical: hyper, hypo, oligo and anodontia
shape: abnormal in individual or fusion of 2 buds=large tooth
size: macro and microdontia
genetic factors: amelogenesis (hardness, mineralisation of enamel and altered amount of ameloblasts)
dentinogenesis (lower mineralisation of dentin)
environmental factors
- nutritional def= vit D rickets= enamel hypoplasia
- tetracyclins= enamel hypoplasia+ yellow brown teeth
- syphilis= hutchinsons teeth discoloration
- rubella virus
- radiation
Day 0-
day 0: Fertilization- M+F fuse in ampulla of uterine tube
DAY 0-13
FERTILIZATION- M+ F fuse at ampulla
sperm move up uterine tube (uterine cilia+propolsion sperm); reach isthmus (30min-6 days)+stops. Goes at OVULATION sperm motile (chemoreceptors) to ampulla
spermatozoa can’t fertiliza until undergo CAPACITATION: (interaction of perm+uterine tube) glycoprotein coat+seminal p.m overlying region of spermatozoa. ACROSOME REACTION: bind ZP, its proteins (ZP3-4) activate enzyme ACROSIN+ TYPSIN to degrade ZP.
3 phases: 1) penetrate CORONA RADIATA 2) penetrate ZP (glycoprotein coat facilitate sperm binding + induce acrosomal reaction to degrade). contacts oocyte membrane cause release of LYSOSOMAL ENZYME (Ca too?)-> CORTICAL GRANULES cause ZP to be impenetrable= PERIVITTALINE BARRIER. 3) fusion of c.m: INTEGRIN (oocyte) mediates+ ligands=DISINTEGRIN (sperm).
after fusion 1)cortical+zona reactions: perivittalin barrier 2) second meiotic divison: for occyte before sperm enters formIng ovum (22 X)+ polar body 3) metabolic activation of egg (activate FACTOR carried by spermatozoon).
spermatozoon lies close female pronucleus and spermatozoo’s nucleus swell to form= M pronucleus. both lose nuclear envelope+ mitosis
Cleavage: zygote reach second cell stage division -> blastomere-> third=compact ball of cells held by TIGHT junction. compaction separate inner+outer
3 days after fertilization fourth: 16 cell MORULA (inner and outer mass)
Blastocyte: morula enters uterine cavity fluid penetrate ZP into inner mass (of stroma of endometrium). spaces merge=BLASTOCELE a single cavity (blastocyte epi walls form: embryoblast+ trophoblast (placenta).
6d: trophoblastic cells in embryoblast pole penetrate cells in uterine mucosa -> endometrium of blastocyte dissolve(trophoblast enzyme) -> 8d: implantation begin in endometrium stroma
trophoblast differentiate: CYTOTROPHOBLAST (inner, mononucleated cells w mitotic factor) + SYNCYTIOTROPHOBLAST (outer, multinucleated, no boundary)
cytotrophoblast differentiate to: HYPOBLAST (outside, small CUBOIDAL adj to bastocyte cavity)+ EPIBLAST (inside, COLUMNAR adj to amnionic cavity). both form BILAMINAR DISC 0.1-0.2 um???)
small cavity in epiblast= AMNIONIC CAVITY+ amnioblast??
9d: penetration of blastocyte into endometrium fixed by FIBRIN COAGULUM.
embryoblast pole: vacuole appear+fuse= LACUNAE
abemembryonic pole: EXOCOELIC MEMBRANE forms by flattened cells of hypoblast lines inner membrne if cytotrophoblast. this membrane+hypoblast form PRIMITIVE YOLK SAC (lining of exocoelic cav)
11+12d: blastocyte PROTRUSION to lumen of uterus. lacunar space create INTERCOMMUNICATING network of trohoblast (embryonic pole). (abembryonic pole has omre trophoblast in cytotrophoblastic)
maternal blood enter lacunar (cells of synciotrophoblast penetrate deeper in stroma and erode endothelial cells of sinusoidal cap) establish UTEROPLACENTAL CIRCULATION
cytotrophoblast+ primitive yolk sac= EXTRAEMBRYONIC MESODERM (loose CT); has two layers SOMATIC (parietal; surround cytotrophoblast+amnion) + SPLANCHNIC (visceral; surrounds yolk sac) cavity forms inside= CHORINIC CAVITY (surround amnionic cav+ primitive yolk sac except connectign stalk where germ disc connected to trophoblast)
13d: surface defect of endometrium healed but bleeding occur at implantation site PRIMITIVE VILLI: cellular column, formed by cytotrophoblast penetrate syntiotroblast SECONDARY YOLK SAC: new cells from hypoblast-> primitive-> profliferate to form it. large portion of primitive pinched off = EXOCOELIC CYSTS in chorionic cavity extraembryonic mesoderm= CHORIONIC PLATE connecting stalk (where embryonic mesoderm cross chorionic cavity) -> UMBILICAL CORD
gastrulation
notochord
gastrulation=germ layers
3week: PRIMITIVE STREAK (epibast groove) end = PRIMITIVE NODE has pit. cells of epiblast-> primitive streak and invaginate
some displace hypoblast= endoderm
some bewteen epiblast and endoderm= mesoderm
cell sreminaing in epiblast= ectoderm
migration reg by FGF8 - FIBROBLAST GROWTH FACTOR 8
As more cells move between epiblast+hypoblast, spread lat+cranially+ contact extraembryonic mesoderm where passes PRECHORDAL PLATE (cephalic direction). forms TIP OF NOTOCHORD+ OROPHARYNGEAL MEM
Notogenesis= neurolation for NS from endoderm
PRENOTOCHORDIAL cells invaginate primitive node + move forward craniallu and intercalate hypoblast forming 2 layers= NOTOCHORDIAL PLATE
hypoblast replaced by endoderm and cells of notochordial plate proliferate+ detach= DEFINITIVE NOTOCHORD
underlying neural tube+ signalling center for axial sk develop
cranial end forms first
notochord+ cells-> cranially to prechordial plate (caudal to primitive pit) cause indentation in epiblast= NEUROENTERIC CANAL (connect amnionic+yolk sac cav)
CLOCAL MEMBRANE= tightly adherent ecto+endoderm
16d: post wall of yolk sac form diverticulum= connecting stalk/ALLONTOIS/ allonteric diverticulum
