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Treacher Collins syndrome
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Pierre Robin syndrome
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Embryology
Anatomy
| Question | Answer |
|---|---|
| Treacher Collins syndrome | Defects of eyes, ears,mandible and palate; Malar hypoplasia (underdeveloped zygoma orbit & lower jaw), Downslanting palpebral fissures, Notched lower eye lids, Deformed external ears, Occasional middle and internal ear defects Incomplete octocephaly |
| Pierre Robin syndrome | Mandibular hypoplasia, Cleft palate, Macrostomia, Glossoptosis; With micrognathia, or retrognathia, the chin is posteriorly displaced causing the tongue to fall backward toward the posterior pharyngeal wall; obstruction of the airway on inspiration |
| Ectopic parathyroids | Parathyroids may be near or within the thyroid or thymus or near bifurcation of Common carotid artery. |
| 5th pharyngeal pouch | Ultimobranchial Body gives rise to the parafollicular cells or C cells - lateral rudiment of the thyroid; C cells differentiate from the neural crest. |
| Di George syndrome | absent parathyroid gland; failure of differentiation of 3rd and 4th pouches into thymus and parathyroids. The immune deficit is caused by hypoplasia or aplasia of the thymus gland 1st arch syndrome defects. Chromosomal deletion defect |
| Congenital absence of thymus and parathyroids | Susceptible to infections; Fish mouth deformity- shortened philtrum; Low set notched ears; Nasal clefts; Thyroid hypoplasia Defects of arch of aorta and heart |
| Mesoderm Cells Differentiate into: | Muscles and Arteries |
| Neural Crest Cells: | Differentiate into Bone and Connective Tissue. |
| Pharyngeal Arches (1,2,3,4) | contain somitomeric mesoderm and neural cells. |
| Pharyngeal Pouches (1,2,3,4) | are evanginations of endoderm that lines the foregut. |
| Pharyngeal Grooves (1,2,3,4) | are invaginations of ectoderm located between each pharyngeal arch |
| Pharyngeal membranes (1,2,3,4) | structures consisting of ectoderm, intervening mesoderm and neural crest, and endoderm located between each pharyngeal arch. |
| Arch 1 (Maxillary and Mandibular prominences) | CN: V; Mesoderm-M. of mastication; mylohyoid, anterior belly of digastric, tensor tym/pala; Neural Crest - Maxilla, mandible, incus, malleus, zygomatic bone, squamous temporal bone, palantine bone, vomer, sphenomandibular ligament, and meckel's cartilage. |
| Arch 2 | CN: VII; Mesoderm-M.of facial expression, posterior belly of digastric; stylohyoid, stapedius; Neural Crest-Stapes, styloid process, stylohyoid ligament, lesser horn and upper body of hyoid bone and Reichert's cartilage |
| Arch 3 | CN: IX, Mesoderm-Stylopharyngeus, commmon carotid arteries, internal carotid arteries; Neural Crest - Greater horn and lower body of hyoid bone. |
| Arch 4 - 6 | CN: X (superior laryngeal N); Mesoderm - Muscles of Soft palate (except tensor veli palantini) muscles of pharynx (except stylopharyngeus) cricothyroid, cricopharyngeus, laryngeal cartilages, R subclavian artery, arch of Aorta 6th arch (inferior laryngeal |
| Pouch 1 and 2 | Epithelial lining of auditory tube and middle ear cavity, and mastoid air cell; Epithelial lining of palantine tonsil cyrpts. |
| Pouch 2 and 3 | Inferior parathyroid gland + Thymus; Superior parathyroid gland - Ultimobranchial body. |
| Goove 1 and Membrane 1 | Epithelial lining of the external auditory meatus; Tympanic membrane. |
| Intermaxillary Segment and primary palate forms: | when the two medial nasal prominences fuse together at the midline and gives rise to the philtrum of the lip, four incisor teeth, and primary palate of the adult. The primary palate forms anterior to the incisive foramen. |
| Secondary Pallate forms: | from the outgrowths of the maxillary prominences called palantine shelves, which fuse in the midline, posterior to the incisive foramen. |
| The FACE forms: | From three swellings: Frontalnasal prominence, a pair maxillary prominence (pharyngeal arch 1), and a pair mandibular prominence |
| First arch syndrome results from: | Abnormal formation of pharyngeal arch 1 because of faulty migration of neural crest cells causing facial anomalies. ie Treacher Collins Syndrome and Pierre Robin syndrome |
| Pharyngeal fistula occurs: | When pouch 2 and groove 2 persist, thereby forming a fistula generally found along the anterior border of the sternocleidomastoid muscle; The fistula is open; Whereas a cyst is closed |
| Primitive Streak | Beginning of third week; thickened linear band of epiblast on dorsal caudal aspect of embryonic disk; raised layer on the surface of the epiblast proliferates and migrates cranio-caudally. |
| Notochord | 1. Acts as rigid axis 2.foundation upon vertebral column (vertebral bodies) will form around it 3. Induces development of Neural plate from neuroectoderm (formation of nervous system); Forms nucleus pulposus of each intervertebral disk. |
| (Intraembryonic) Mesenchyme cells migrate from Primitive Node and Streak to Form: | Cranially: 1)Cardiogenic Mesenchyme 2)Notochord 3)Septum transversum; Laterally: 4) Para-axial, intermediate and lateral plate mesoderm; Caudally: 5) Infraumbilical part of anterior abdominal wall - Absence of of mesoderm in ectopia vesicae |
| Chordoma | is a localized intervertebral disk, capable of causing nerve damage; often develop in base of skull/nasopharyngeal region |
| Sacrococcygeal Teratomas | Can result from remnants of primitive streak that fail to differentiate; Can also be result of primordial Germ cells that fail to migrate from yolk sac back to the future gonad region. |
| Hydatidform mole | Grape like villi; HCG levels are markedly elevated; Patients with a hydatidiform mole are often large for dates and have hyperemesis gravidarum more frequently; Patients may present with bleeding, and may pass some of the grape-like villi. |
| Types of Hydatidform | Completed hyatidiform mole (No gestational sac-usaully); Triploidy - Partial hyadtiform mole with pregnancy |
| Intermediate Mesoderm | Urogenital system, including gonads, ducts and accessory glands. |
| Paraxial Mesoderm | Muscles skeleton except skull dermis of skin connective tissue |
| Lateral Mesoderm | Connective tissue of viscera and limbs serous membranes of pleura, pericardium and pericardium and peritoneum blood and lymph cells cardiovascular and lymphatic systems |
| Neurulation | Neural tube formation, begins as primitive ectoderm is induced by notochord to differentiate into neuroectoderm |
| Abnormal Neurulation | Exencephally Anencephaly -cranial neuropore hasn't closed, exposed brain tissue undergoes necrosis; Frequently combined with spina bifida in cervical and thoracic segments; Rachischisis, meningomyelocele and meningocele are very severe neural tube defect |
| Meningocele | The arachnoid protrudes through defect of vertebral arches but is covered by skin; sac like cyst is enlarged subarachnoid space filled with cerebrospinal fluid. |
| Derivatives of Neural Crest Cells | Spinal ganglia, Ganglia of Autonomic nervous system, Ganglia of cranial N, Sheaths of Peripheral N, Meingeal coverings of brain and spinal cord, pigment cells, Adrenal medulla, Odontoblast of tooth, other components of head. |
| Primitive Streak consists of: | Primitive groove, Primitive node, and primitive pit; First indication of gastrulation caused by proliferation of epiblast cells. |
| Embryonic Period | Folding of Embryo occurs in two planes, Cranio-caudal folding caused by growth of central nervous system and amnion and Lateral folding caused by growth of somites, amnion, and other components of lateral body wall; Embryo becomes 3-dimensional cylinder |
| Hox complex of genes | Controlls basic segmentation of human embryo in the cranio-caudal direction |
| Gastrulation is the process that establishes: | 3 definitive germ layers of the embryo (Ectoderm, intraembryonic mesoderm, and endoderm), forming a trilaminar embryonic disk by day 21 of development. |
| Cloacal Membrane | Located caudal to primitive streak, future site of anus, site where epiblast and hypoblast cells are fused |
| Paraxial Mesoderm | Becomes organized into segments known as somitomeres; Somitomeres 1-7 contribute mesoderm to pharyngeal arches; Remaining somitomeres condense in cranial caudal sequence to form a total of 35 pairs of somites by end of 5th week; First pair form at day 20; |
| Somites differentiate into following components: | Sclerotome: forms cartilage and bone components of vertebral column; Myotome: forms muscles; Dermatome: forms dermis and subcutaneous area of skin |
| Intermediate Mesoderm | forms urogenital ridge which is invovled in formation of future kidneys and gonads. |
| Caudal Dysgenesis (Sirenomelia) | Genetic Abnormalities and toxic insults result in incomplete gastrulation in the caudal end of the embryo; can also be result of decrease vascular flow to lower extremities. |
| Mesenchyme | From Epiblast cells through primitive groove to form intraembryonic mesoderm and intraembryonic endoderm. |
| Prechordal plate and Cloacle membrane | future mouth and anus |
| Day 16 | Trilaminar embryonic disc; Notochordal process; Cardiogenic mesoderm. |
| Fourth Branchial Arch, Cleft and Pouch Derivatives | Arch (Mesoderm): Arch of aorta(left), (R)T subclavian artery(right), CN X, Thyroid cartilage, Part of epiglottis, Cuneiform cartilage; Cleft (Ectoderm)-None; Pouch (Endoderm) - Superior parathyroid, thymus. |
| Third Branchial Arch, Cleft and Pouch Derivatives | Arch(mesoderm) - Common carotid artery part of ICA, CN IX, Hyoid (greater horn and part of body), part of epiglottis; Cleft (ectoderm)-None; Pouch (endoderm)-Inferior parathyroid, Piriform fossa, Thymus. |
| Second Branchial Arch, Cleft and Pouch Derivatives | Arch-Stapes, stapedial artery, CN VII/VIII, Styloid process, Hyoid bone (lesser horn/part of body), Root of tongue, Foramen Cecum, External ear, Part of Stapedius A; Cleft - none; Pouch-Palantine tonsil, Supratonsillar fossa, Thyroid gland's median anlage |
| First Branchial Arch, Cleft and Pouch Derivatives | Arch-Incus body, Malleus head and body, Pinna, Meckel's cartilage, External maxillery artery, CN V (V2/V3) maxillary/mandibular, Body of tongue, External ear; Cleft-External auditory canal; Pouch- Eustachian tube; Middle ear cavity; Mastoid air cells |
| Inferior Parathyroids (III) | Develop from 3rd Pharyngeal Pouch; Descend during week 4 into superior mediastinum meeting its fellow of opposite side to form bilobed Thymus; Lymphocytes of thymus-from mesenchyme and the thymocytes are derived from endoderm. |
| Superior Parathyroids (IV) | Descend only to superior part of thyroid as superior parathyroids; descends with thymus into neck |
| Formation of Palatine Tonsils | Develops from pouch as proliferation of endoderm into mesoderm; Pouch endoderm -tonsillar crypts; About 20 weeks mesenchyme around crypts differentiate into lymphoid tissue. |
| Eustachian Tube | Expands in tubotympanic recess; Distal part of this recess meets 1st pharyngeal groove; Cavity of TT recess forms middle ear cavity and mastoid antrum; Connection b/w TT recess and pharynx elongates to form Eustacian tube |
| Octocephaly or Franceschetti's syndrome | malformation of mandibular; Characterized by mandibular aplasia or hypoplasia (agnatia of micoragnatia), malposition of teeth, deformation of mouth, down-slanting palpebral fissure, Auricles pulled cuadally, defective acoustic meatus, conductive deafness, |
| Cranial Nerves 4 & 6th arches | 4th arch-CN X superior laryngeal Nerve; 6th arch CN X-XI Recurrent laryngeal Nerve |
| Ectopic thyroid | Lingual most common; Sublingual - high in neck or just below hyoid bone; |
| Accessory thyroid | Tissue may lie superior to thyroid, lateral to thyroid cartilage or on thyrhyoid muscle |
| Thyrogloassal cyst | Thyroid Moves up with protrusion of tongue; Develops from remnants of thyroglossal duct which may persist as a cyst in tongue or in midline of neck below hyoid. Cysts are closed; Sinuses are open; Asymptomatic unless infected. |
| Ectopic thyroid | Moves up with swallowing (Should be differentiated form thyroglossal cyst to prevent inadvertent removal of the only thryroid tissue; Superior more constant |
| Thyroid | Forms by day 24 (3rd week); from floor of the primitive pharynx a midline diverticulum descends in the neck; Descends anterior to anterior to hyoid and thyroid cartilage2; Attached to hyoid by levator glandulae thyroideae; Thyroglossal duct disintegrates; |
| Cartilage (Meckel’s Cartilage) | Dorsal end becomes the malleus and incus – Intermediate portion regresses, but the perichondrium forms: Anterior ligament of the malleus Sphenomandibular ligament –– Ventral portion forms the mandible |
| Inner ear development | Thickening of ectoderm; called otic placode; invaginates into underlying mesenchyme; detachaches from ectoderm and divides into 2 - urticular (urticle, semicircular canals and emdolymphatic duct) and saccular - saccule and cochlear duct |
| External Ear | 6 mesenchymal swellings-auricular hillocks, develop around the first branchial cleft, mesenchyme derived from mesoderm in 1st (3) and 2nd (3) branchial arches, |
| Nerve innervation to Developing Ear | Nerves that supply skin and muscle of external ear is by auriculotemporal nerve(sensory-1st arch) and facial nerve(motor-2nd arch; sensory) |
| Developing Ear | First pharyngeal cleft gives rise to external auditory meatus; 1st & 2nd arches give rise to external ear. |
| Tongue | Endodermal swellings on Arches 1-4 contribute to the tongue |
| Clefts | 2nd to 4th clefts become buried by overgrowth of 2nd arch to form cervical sinus (disappears by week 7), 1st cleft invades mesenchyme opposite 1st pouch to become EAC and ectoderm of tympanic membrane. |
| Pouches | 1st pouch becomes middle ear; 2,3,4 cleft become ganglion |
| Tympanic Membrane | Only membrane in the body to have all 3 layers |
| Cleft Palate | Anterior - when palatine shelves fail to fuse with primary plate; Posterior - occurs when palatine shelves fail to fuse with each other and nasal septum; Anteroposterior occurs when there is a combination of both defects. |
| Cleft lip | Unilateral or bilateral; Unilateral most common and arises when maxillary prominence fails to fuse with medial nasal prominence; And when underlying somitomeric mesoderm and neural crest fail to expand resulting in persistent labial groove |
| Intermaxillary segment gives rise to | Phitrum of the upper lip; upper incisor teeth and gums; primary palate (region of hard palate just posterior to upper incisors) |
| bridge of the nose and the intermaxillary segment formed by: | fusion of the 2 medial nasal prominences |
| The 2 mandibular prominences fuse to: | complete the lower jaw. |
| The sides (alae) of the nose formed by: | The 2 lateral nasal prominences fusing with the 2 maxillary prominences (but not with each other). |
| Time line for develpment | Pharyngeal arches (4wks), External face (6wks), Primary palate (6wks), Secondary palate (8wks), Completion of soft palate (12wks); Decrease with severity of potential congenital malformations over time. |
| 1st to form | Lower jaw and lip. |
| Anterior choanae | LNP & MNP proliferate and describe the nasal pits to form primordial nasal sacs |
| vomeronasal organ of Jacobson | Epithelium of nasal cavity differentiate to form olfactory epithelium |
| future nasolacrimal duct | Nasolacrimal groove separates the maxillary process from the lateral nasal prominence (Ectodermal derivative) |
| Oblique facial clefts | often bilateral extend from the upper lip to the medial margins of the orbit. When this occurs the nasolacrimal ducts are open grooves |
| Lateral or transverse facial clefts | extend from the mouth to the ear;Bilateral clefts often result in Macrostomia |
| Development of Palate | Develops from 2 primordia;Begins at the end of 5th week and completes by 12th week. Most critical period is b/w end of 6th week & beginning of 9th week |
| Primary Palate | Begins from the inter-maxillary segment Forms - Premaxilla- represented as the part anterior to the V shaped suture b/w that contain the incisors & incisive fossa. |
| Development of Tongue | Distal tongue buds merge with each other to form Ant 2/3 ;The post 1/3 of the tongue is formed by the rostral part of the hypobranchial emminence (Arch 3); Caudal part of hypobranchial emminence (Arch 4) forms the epiglottis |
| Tongue innervation | Tongue muscles originate from the occipital somites which bring with them innervation (CN XII), Innervation Ant 2/3 CN V; POST 1/3: CN IX; |
Created by:
togini