Development of Orofacial Region PDF

By: ayah bataineh Audit: Dima raed atwa L -2 DEVELOPMENT OF OROFACIAL REGION ‫ال تعارض بين العلم والتعبد‬ ‫ ال‬،‫ " إنما يُراد العلم للعمل‬:‫ طلب العلم أحب إليك يا أبا عبدهللا أو العمل؟ فقال‬:‫سئل سفيان الثوري‬ ُ :‫قال عبدهللا بن المبارك‬ "‫ وال تدع العمل لطلب العلم‬،‫تدع طلب العلم للعمل‬ topic2: DE...

By: ayah bataineh Audit: Dima raed atwa L -2 DEVELOPMENT OF OROFACIAL REGION ‫ال تعارض بين العلم والتعبد‬ ‫ ال‬،‫ " إنما يُراد العلم للعمل‬:‫ طلب العلم أحب إليك يا أبا عبدهللا أو العمل؟ فقال‬:‫سئل سفيان الثوري‬ ُ :‫قال عبدهللا بن المبارك‬ "‫ وال تدع العمل لطلب العلم‬،‫تدع طلب العلم للعمل‬ topic2: DEVELOPMENT OF OROFACIAL REGION ❖ Folding of the embryo. After longitudinal folding the brain is the most cephalic part followed by the oropharyngeal membrane (prechordal membrane), then developing heart and liver. Buccopharyngeal membrane ruptures at 21 days→Stomodeum (primitive mouth): the cavity located outside the oropharyngeal membrane between the developing heart and brain (it will change later on). Ectoderm covers the outside of the embryo including the outside of the stomodeum. → later on it will become the lining epithelium The junction between the cavity which will be the stomach and the stomodeum is closed by the oropharyngeal membrane. (no communication between the early mouth and the early gut) GI is lined with endoderm while the mouth is lined with ectoderm. ✓ Branchial (pharyngeal) pouches ✓ Branchial (pharyngeal) clefts ✓ Branchial (pharyngeal) arches ❖ Branchial arches (very very important). 5-6 arches lined in the outside by ectoderm developing at different times so you will never see them together. 21 days After arches development Stomodeum will be located between 28 days 32 days arch 1 and frontonasal process of the developing brain. 26 days Each arch has a neural, vascular, muscular, skeletal component. Embryologic basis of all the differentiated structures of the head and neck such as the ear, tympanic cavity, lingual tonsils… 5 pairs of branchial arches appear on day 22.)5 ‫ او‬6 ‫(مش مهم عددهم في كتب‬ Correspond to the primitive vertebrae gill bars. On either side of the pharyngeal foregut Each arch consists of 3 layers: ✓ Outer covering of ectoderm ✓ Inner covering of endoderm. ✓ Middle core of mesenchyme. Except the first arch from inside and outside its ectoderm, because the tongue originates from the inside of the first arch and its lining is ectodermal. Arches are separated further into: ✓ External, ectoderm-lined pharyngeal clefts ✓ internal, endoderm-lined pharyngeal pouches 1 DEVELOPMENT OF OROFACIAL REGION First stages of a recognizable face at the end of the third week→ Frontal nasal process (cephalic portion of the neural tube) and Branchial arches Over weeks, the arches grow differentially (at different speed and different regions) and obliterate plates/grooves to give rise to the face. Each arch gives rise to a cranial nerve, muscles, and cartilage/bone. The size of the embryo at this stage is almost 1 cm. The first brachial arch will develop into: 1) maxillary 2) mandibular, and then they will fuse together with the frontonasal process to form the face. ✓ If any problem happened it will become a cleft (ex: cleft lip, cleft palate) ❖ Clefts and pouches. The cleft is the junction between each arch from outside, while the pouch is the junction between each arch from inside. The cleft has the number of the arch before it: cleft1 ,2… The first cleft laterally deepens to become the external auditory meatus and from inside it will become eustachian tube and then develops to become the tympanic cavity and the remnant tissue between them is the tympanic membrane. The deepening in the second pouch will become palatine tonsils. The deepening in the third pouch will separate into two parts: ✓ the upper part will become inf. parathyroid gland. ✓ the lower part will become thymus. The fourth pouch will become sup. parathyroid gland. The second and third and fourth clefts will disappear but sometimes they fuse and become cervical cyst/sinus (cystic lesion, it happens because second arch develops faster than the other arches). Note: the location of sup. Parathyroid and the inf. Parathyroid is different than their location in anatomy, then they will switch their location. Thyroid gland develops from the tongue not from these arches. ❖ Skeletal elements. First arch o Meckel’s cartilage (endochondral ossification): bar of cartilage that exists in the body if 1st arch, it’s temporary structure. A cross section of Meckel’s cartilage→ circle. ✓ Anterior part Doesn’t form the body of the mandible: act as template against its lateral surface the body of the mandible will form.(just guide the mandible) Act as a scaffold for the body of the mandible to form at its lateral aspect. Disappears finally. ✓ Middle part The perichondrium (the covering of the middle part)→Anterior malleolar ligament (attached on malleus, it dampens the vibration of the malleus) and the Sphenomandibular ligament (connects the lingula with the sphenoid, it supports the temporomandibular joint and it’s a key ligament in local anesthesia to block the inf. Alveolar nerve) 2 DEVELOPMENT OF OROFACIAL REGION ✓ Dorsal end – Malleus (first ear ossicle) o Pterygoquadrate bar cartilage →Incus Second arch o Reichert’s cartilage ✓ Dorsal end – Stapes. ✓ Remainder: Styloid process and stylohyoid ligament. Hyoid bone except greater horn Third arch - Greater horn of hyoid Fourth to sixth arches – Thyroid, cricoid & arytenoid cartilages, within the larynx. ❖ Nervous elements First arch→ Trigeminal nerve (V) Second arch→ Facial nerve (VII) Third arch→ Glossopharyngeal (IX) Fourth to sixth arches→ Vagus nerve (laryngeal branch). ❖ Muscular elements. First arch, Muscles innervated by trigeminal nerve: ✓ Muscles of mastication: masseter, temporalis, medial and lateral pterygoid. ✓ Anterior belly of digastric (each belly is supplied by different nerve, post belly→ facial) The digastric muscle develops within two branchial arches: the first and the second arches. ✓ Mylohyoid ✓ Tensor tympani ✓ Tensor veli palatini (the main muscle of the palate) Second arch ✓ Muscles are innervated by facial nerves. ✓ Muscles of facial expression (ex: buccinator, orbicularis ocli, orbicularis oris, zygomaticus minor and major..) ✓ Posterior belly of digastric ✓ Stylohyoid. Third arch: Muscles innervated by glossopharyngeal nerve→Palatopharyngeus muscle Fourth to sixth arches o Muscles innervated by the pharyngeal branch of Vagus nerve. ✓ All muscles of the pharynx except palatopharyngeus ✓ All muscles of the soft palate except tensor veli palatini o Muscles innervated by the laryngeal branches of Vagus nerve. ✓ Intrinsic laryngeal muscles ✓ Extrinsic laryngeal muscles ❖ Vascular elements)‫(أقل أهمية بالعاده ما بسأل عليه الدكتور باالمتحان‬. Each arch – right & left aortic arch vessel. 3 DEVELOPMENT OF OROFACIAL REGION Leads from the heart. Ascends dorsally to the face, brain & posterior region of the body. Third arch vessel becomes prominent to take over the facial region of the first two – common carotid artery. Fourth arch vessel – dorsal aorta Blood supply for neck & face Before week seven – internal carotid After week seven – external carotid ❖ Pharyngeal pouches ❖ Tongue formation Appears at 32 days ,4 weeks and a half after fertilization. Develops from: ✓ Swellings from 1st arch (anterior 2/3s)→2 Lateral swellings, Tuberculum impar ✓ Swelling from 3rd (posterior 1/3)→Copula/Hypobranchial eminence, Overgrows 2nd arch and fuses with the ant. Swellings ✓ Swelling from 4th arch (extreme posterior, root of the tongue)→Epiglottis. Sulcus terminalis: separate the ant. 2/3 and post.1/3 of the tongue (the fusion line between what was coming from the first arch and what was coming from the 3rd arch) Foramen cecum→ remnant of the Thyroglossal duct: a duct that develops from the foramen cecum area and goes down and lead to the formation of Thyroid glands. ✓ We can find thyroid tissue in the tongue (lingual thyroid) ❖ Innervation of the tongue Anterior 2/3s o Sensory→ First arch nerve (trigeminal through lingual nerve) o Taste→Facial nerve through chorda tympani, Glossopharyngeal (Vallate papillae migration→ anatomically: just ant. To the sulcus terminalis, embryologically→from the 3rd arch ) ✓ There is a contribution from the second arch in the formation of taste buds, so they are innervated by the facial nerve. o Motor→ Hypoglossal nerve XII (muscles of the tongue are from myotomes of metotic somites: from arch 3-6 contribute to the formation of the muscles of the tongue.) Posterior 1/3 o Sensory and taste (including Vallate papillae) →Third arch nerve (glossopharyngeal) Extreme posterior o Sensory and taste→ Fourth arch nerve (Superior laryngeal nerve). 4. DEVELOPMENT OF OROFACIAL REGION ❖ Development of the face. Growth of: 1. The first arch that have divided into: Maxillary processes (separated by stomodeum) and Mandibular processes (meat at the midline) 2. Frontonasal process (leads from the fast development of the forebrain). Face forms around stomodeum which is located between: frontonasal (above) process and the mandibular processes (bottom) and maxillary processes (sides) Between maxillary processes we have cavity which is not continuous with the foregut they are separated by buccopharyngeal membrane (was prechordal plate) Buccopharyngeal membrane ruptures at 21 days At this stage we have the first appearance of the eye (completely at the side) External acoustic meatus develops from the first brachial cleft (downward then they will go up) The junction between frontonasal process and maxillary process (between pink and yellow) → deepen to form the eye→ deepen to form a canal → Nasolacrimal duct. Nasolacrimal duct: Forms between lateral nasal swellings and maxillary process The heart is developing just under the face. ❖ Frontonasal process (unpaired) The full distance from one side to the other side of the frontonasal process is 10 mm Nasal placodes o Nasal pit → nostrils o Medial nasal swellings (together → Intermaxillary segment) ✓ Mid portion of the nose ✓ Philtrum of upper lip ( part of the frontonasal process ) ✓ Primary palate o lateral nasal swellings→ Alae of the nose Nasal pits: depressions at either side of the frontonasal process will lead to the formation of nostrils (very separated at the side). ✓ Nasal pits will deepen and form two swellings around the nasal pits: 1- lateral swellings 2-medial swellings. ✓ Then we will have fusion with the two medial swellings to form intermaxillary segment ✓ Intermaxillary segment then will go down to form the philtrum of the upper lip (the midline of the lip) and it will form the primary palate (the part of the palate that holds the upper incisors) ✓ Embryologically the philtrum is not from the first arch it’s part of the frontonasal process. ✓ Upper incisors: develop in bone that comes from intermaxillary segment from frontonasal process 5 DEVELOPMENT OF OROFACIAL REGION ❖ 1st arch processes (paired) o Maxillary processes ✓ Much of the maxilla ✓ Lateral parts of upper lip o Mandibular processes→ Mandible (except the angle of the mandible which is supplied by cervical nerves), Lower lip The maxillary process was at the side of the of the stomodeum and bellow the frontonasal process, with the fast development of the frontonasal process into nasal placodes they will be located between maxillary processes. ❖ Palate 6 Starts at 6 weeks. (don’t focus on ages) Primary palate (premaxilla) continuous with the philtrum which are part of the frontonasal process. Each sense organ develops within capsule. Optic capsule and nasal capsule develop endochondrally. Nasal septum: post. → Vomer bone, ant. → ethmoid bone, they fuse with the primary palate At this stage each all of the processes are separated because the tongue is occupying the space between them The tongue is huge at this stage and occupying distance between the two maxillary processes (palatine shelfs) and occupying distance between secondary palate. Secondary palate ✓ Palatine processes ✓ 1st they are vertically oriented. ✓ Tongue in between ✓ Horizontal reorientation (when tongue go down) ✓ Fusion with primary palate ✓ Fusion with each other ✓ Fusion with nasal septum Palate completed by 60 days. With the further growth of the fetus superioinferiorly the tongue will go down, this will clear the space between secondary palates, and they start to orient their position and fuse with nasal septum and with the primary palate. Direction of fusion (very important, look at the picture) : 1. primary palate and ant. Part of secondary palate and nasal septum will fuse together in the midline. 2. the line of fusion continues posteriorly to fuse the two secondary palates 3. the line of fusion will go anterolaterally to join the secondary palate with the primary palate. (between the primary palate with one of the secondary palates ).. DEVELOPMENT OF OROFACIAL REGION Note: at this stage nasal septum and nasal cavity are continuous with the oral cavity, but with the development they will orient themselves ❖ Clefts : If something goes wrong during the fusion , the clefts will be the result. Every 700 birth there is 1 born with cleft (not rare ) Cleft lip: lack of fusion o may be as simple as white line on the upper lip (looks like scar tissue) o Others born with more severe cases → unilateral cleft (failure of complete fusion between the intermaxillary segment and the maxillary process on one side) ✓ May affect the lip alone→ surgery treatment. ✓ Or it may go down preventing the fusion between primary palate and secondary palate on one side → communication between oral and nasal cavity which leads to feeding problem. o Bilateral cleft: bilateral lack of fusion between intermaxillary segment and maxillary processes, affecting only the lip or affecting the lip and the primary palate. Cleft palate: Simple→ lack of fusion in the post. Part Severe→ unilateral cleft it may be continuous with lip → cleft palate/ lip. bilateral cleft palate/ lip→ no fusion at all (the worst one ) ✓ line of failure of fusion in the area between the incisors and canines (canines may not develop, and if they develop e must remove them to complete the surgery) ✓ Treatment: series of surgeries, speech therapist, feeding therapist. Rarely: median cleft → failure of the two median nasal processes to fuse completely (the intermaxillary process clefted) Facial cleft: failure of fusion between lateral nasal swelling and the maxillary process (cleft from the corner of the nose towards the eye). ❖ Development of the maxilla 7 intramembranous ossification (transmembranous ossification): this type of ossification happens in the connective tissue membrane. 2 ossification centers 1. Maxilla proper (within the body of the maxilla) ✓ Ossification starts at 40 days. ✓ Maxillary sinus (hollowed out) 2. Premaxilla (primary palate): Ossifies later than maxilla The body of the maxilla has Processes: ✓ Frontal: meet with the frontal bone ✓ Zygomatic ✓ Palatine: secondary palate ✓ Medial & lateral alveolar plates: the teeth develop between them.. DEVELOPMENT OF OROFACIAL REGION Later on segmentation (bone septum) will occur on each two developing teeth → bone filling ❖ Development of the mandible Meckle’s cartilage is the primary cartilage develops ( temporary cartilage). The first cartilage that appear within an area. Mandibular nerve will separate into Lingual nerve and inf. Alveolar nerve → Meckel’s cartilage located in between them. ✓ lingual nerve medial to Meckel’s cartilage, inf. Alveolar nerve is lateral. ✓ mental nerve→ go through mental foramen supply the lower lip ✓ incisive nerve will continue bellow ant. Teeth ✓ The nerves are fast developing as the brain grows fast→ the cranial component guide embryology. ✓ the ossification center where the inf. Alveolar nerve will divide. Development of body o Intramembranous ossification o Close association with Meckel’s cartilage o Ossification starts at ✓ 7 weeks ✓ At the site where mental nerve branches off ✓ Continues around IAN o Two Alveolar process o Symphasis menti (the junction between two mandibular halves) Fuses o at 1st postnatal year. ❖ Development of ramus 8. The part of the mandible above the mandibular foramen Endochondral ossification: a secondary cartilage will appear within condylar process and coronoid process Condylar cartilage: Appears at 11 weeks, Growth until 21 years. Coronoid cartilage: 14 weeks, Replaced by bone before birth. The difference between adult and infant mandible: in infant the ramus is very small, and the angle between body and ramus is obtuse, the growth is because of the endochondral ossification within condylar and coronoid processes. ❖ Mandibular units. Condylar+ coronoid → endochondral and the rest of the mandible is intramembranous. Body Angular → forms in response to: Medial pterygoid and Masseter m. laterally Coronoid → forms in response to temporalis Alveolar: Forms in response to teeth Once you lost your teeth the alveolar bone will be lost..