Development of Head and Neck PDF

Development of Head and Neck PHARYNGEAL ARCHES The development of the head and neck begins in the 4th and 5th week. Growth of mesenchymal tissue in the cranial region of the embryo results in the formation of arches. They are called «pharyngeal» arches since they develop beneath the head, in the pha...

Development of Head and Neck PHARYNGEAL ARCHES The development of the head and neck begins in the 4th and 5th week. Growth of mesenchymal tissue in the cranial region of the embryo results in the formation of arches. They are called «pharyngeal» arches since they develop beneath the head, in the pharyngeal region of the neck What are the sources that give rise to head and neck? Paraxial mesoderm Lateral plate mesoderm Neural crest Ectodermal placode (neuroectoderm) Paraxial mesoderm: ✔ Scull base ✔ A part of the occipital bone ✔ Skeletal muscles of the posterior head ✔ Skin and connective tissue of the posterior head ✔ Meningea, caudal to prosencephalone (brain membranes) BACK HEAD! Lateral mesoderm: ✔ Laringeal cartilages (arytenoid and cricoid) ✔ Connective tissue within the laryngeal region LARYNX FACE Neural crest: ✔ Skeletal structures of the face and pharyngeal arches (cartilages and bones), teeth, tendons, skin, pia mater, arachnoid mater, sensory neurons and secretory gland stroma. The mesenchymal growth that turns into the pharyngeal arches, are formed by the migration of neural crest cells –which are located in the upper position of neural tube-, from the dorsal site of the embryo, towards the ventral site. Pharyngeal arches Ectodermal placodes (neuroectoderm): structures that have both neural and ectodermal components NEURAL DETAILS ABOUT THE EYES, NOSE, EARS, BLA BLA… At the end of the 4th week, 4 pairs of pharyngeal arches are formed ARTERIAL SUPPLY ARCH ARTERIAL DERIVATIVES 1st arch Aortic arch 1 becomes the maxillary artery 2nd arch Aortic arch 2 becomes the stapedial artery 3rd arch Aortic arch 3 becomes the common carotid artery and a part of the internal carotid artery 4th arch Aortic arch 4 becomes subclavian artery on the right and arch of aorta on the left 6th arch Aortic arch 6 becomes the pulmonary arteries NERVE SUPPLY  A total of 6 pharyngeal arches are formed in the embryo  1st pharyngeal arch pair appears at the beginning of the 4th week, which includes the MAXILLARY and MANDIBULARY processes STOMADEUM: future mouth, closed by the oropharyngeal membrane Two more pairs of pharyngeal arches will be seen (5th and 6th) Pharyngeal arch 5 and pharyngeal pouch 5 completely regress in the human. NEURAL TUBE Elements of pharyngeal arches Pharyngeal arches are mesenchymal tissues (light blue) surrounded by  ectoderm in the lateral aspect (external/dark blue) which will make the skin and connective tissue of the head and neck  and by endoderm in the medial aspect (internal/green) which will make the epithelial layer of the respiratory and gastointestinal systems. What is pharyngeal pouch and pharyngeal cleft? Pharyngeal clefts are the EXTERNAL grooves between two arches Pharyngeal pouches are the INTERNAL grooves between two arches Electron microscopic image of the pharyngeal arches Clefts and pouches are notable First Pharyngeal Arch The first pharyngeal arch is comprised of two parts: Maxillary prominence (dorsal portion) – becomes the future maxilla, zygomatic bone and part of the temporal bone. Is associated with the maxillary cartilage, which gives rise to the incus. Mandibular prominence (ventral portion) – becomes the future mandible. Is associated with Meckel’s cartilage, which gives rise to the malleus and the sphenomandibular ligament. Derivatives of Pharyngeal Arch Cartilages The dorsal end of the first arch cartilage becomes ossified to form two middle ear bones, the malleus and incus. The middle section of the cartilage regresses, but its perichondrium forms the anterior ligament of the malleus and sphenomandibular ligament. Derivatives of Pharyngeal Arch Cartilages Ventral parts of the first arch cartilage form the horseshoe-shaped primordium of the mandible. Derivatives of Pharyngeal Arch Cartilages The dorsal end of the second arch cartilage (Reichert cartilage) contributes to the stapes of the middle ear, styloid process of the temporal bone and stylohyoid ligament. The ventral end of the second arch cartilage ossifies to form the lesser cornu of the hyoid bone. Derivatives of Pharyngeal Arch Cartilages 3rd pharyngeal arch cartilage The third arch cartilage ossifies to form the greater cornu of the hyoid bone. (The body of the hyoid forms from the hypopharyngeal eminence.) Derivatives of Pharyngeal Arch Cartilages The fourth and sixth arch cartilages fuse to form the laryngeal cartilages, except for the epiglottis. The epiglottic and thyroid cartilages appear to develop from neural crest cells. The cricoid cartilage develops from mesoderm. Derivatives of Pharyngeal Arch Muscles 4-weeks 20-weeks Myoblasts from the first arch migrate from the neck to the head, where they give rise to the muscles of mastication (temporal, masseter, pterygoid: yellow colored), anterior part of the digastric muscle, mylohyoid, tensor tympani ve tensor palatini muscles Derivatives of Pharyngeal Arch Muscles 4-weeks 20-weeks Myoblasts from the second arch migrate from the neck to the head, where they give rise to the muscles of facial expression, auricular muscles and the posterior part of the digastric muscle Derivatives of Pharyngeal Arch Muscles Myoblasts of the 3rd pharyngeal arch give rise to M. stylopharyngeus Myoblasts from the 4th pharygneal arcus give rise to cricothyroid, levator palatini and constrictor muscles of the pharynx. ARCH DERIVATIVES ********************************************************* First arch (mandibular) Skeletal structures, ligaments: Malleus, short limb of incus, maxilla, zygomatic bone, hard palate, vomer bone, mandibule, temporal bone (squamous); anterior ligament of malleus, sphenomandibular ligament First arch Muscles: Muscles of mastication, mylohyoid muscle, belly maxilla, zygomatic bone, hard palate, vomer bone, mandibule, Skeletal structures, ligaments: Malleus, short limb ofanterior incus, of digastric muscle, tensor tympani, tensor veli palatini temporal bone (squamous); anterior ligament of malleus, sphenomandibular ligament Artery derivates: Maxillary artery Muscles: Muscles of mastication, mylohyoid Cranial nerve: Trigeminal nerve (CN V) muscle, anterior belly of digastric muscle, tensor tympani, tensor veli palatini Artery derivates: Maxillary artery Cranial nerve: Trigeminal nerve (CN V) Second arch (hyoid) Second arch Skeletal structures, ligaments: Stapes, long limb of incus, styloid process, lesser horn and upper part of body of hyoid bone; stylohyoid Stapes, ligament Skeletal structures, ligaments: long limb of incus, styloid process, lesser horn and upper part of body of hyoid bone; Muscles: Muscles of facial expression, stylohyoid muscle, posterior belly of digastric muscle, stapedius stylohyoid ligament Artery derivates: Stapedial artery, caroticotympanic arteries Muscles: Muscles of facialCranial expression, muscle, posterior belly of digastric muscle, stapedius nerve: Facial nerve stylohyoid (CN VII) Artery derivates: Stapedial artery, caroticotympanic arteries Cranial nerve: Facial nerve (CN VII) Third arch Skeletal Greater cornu, lower part body Third arch structures, ligaments: Skeletal structures, ligaments: Greater cornu, lower part of bodyof of hyoid bone of hyoid bone Stylopharyngeus muscle Muscles: StylopharyngeusMuscles: muscle Artery derivates: Common carotid artery, internal carotid artery (proximal portion) Artery derivates: Common carotid artery, internal carotid artery (proximal portion) Cranial nerve: Glossopharyngeal nerve (CN IX) Cranial nerve: Glossopharyngeal nerve (CN IX) Fourth arch Skeletal Laryngeal cartilages epiglottis) Fourth arch structures, ligaments: Skeletal structures, ligaments: Laryngeal cartilages (except (except epiglottis) Muscles: Cricothyroid veli palatini, constrictors of pharynx of pharynx Muscles: Cricothyroid muscle, levatormuscle, velilevator palatini, constrictors Artery derivates: Aortic arch, subclavian artery (proximal portion) Artery derivates: Aortic arch, subclavian artery (proximal portion) Cranial nerve: Superior laryngeal branch of vagus nerve (CN X) Cranial nerve: Superior laryngeal branch of vagus nerve (CN X) Fifth arch Transient arch Fifth arch Sixth arch Muscles: Intrinsic musclesMuscles: of larynx, striated muscles of esophagus Sixth arch Intrinsic muscles of larynx, striated muscles of esophagus Artery derivates: Ductus arteriosus, pulmonary arteries (proximal portion) Artery derivates: Ductus arteriosus, pulmonary arteries (proximal portion) nerve: Recurrent laryngeal branch of vagus nerve (CN X) Cranial nerve: Recurrent Cranial laryngeal branch of vagus nerve (CN X) Transient arch PHARYNGEAL POUCHES Pharyngeal pouches are the INTERNAL grooves between two arches Pharyngeal Pouches: Human embryo includes 5 pairs of pharyngeal pouches Among those, no.5 is atypical, and is accepted as a part of the 4th pouch. 1st Pharyngeal Pouch: It will form the eustachian tube, tympanic cavity and the tympanic membrane. 2nd Pharyngeal Pouch: Endoderm of the 2nd pharyngeal pouch grows into the mesenchymal tissue and forms the pair of palatine tonsils, which are infiltrated by the lymphatic tissue in the 3rd-5th months. 3rd Pharyngeal Pouch: 3rd pharyngeal pouch has a dorsal and a ventral part:  Dorsal part gives rise to the inferior parathyroid gland  Ventral part gives rise to the thymus, which is the first endocrine gland develops in the embryo. In time, the right and left pieces of the gland come together in the median line, descend to the inferior cervical region, and lose contact with the pharynx. 4th Pharyngeal Pouch: 4th pharyngeal pouch has a dorsal and a ventral part:  Dorsal part gives rise to the superior parathyroid gland  Ventral part is the recessus of the 5th pouch, and gives rise to the ultimobranchial body, which forms the C cells of the thyroid gland. 1st pharyngeal cleft  Give rise to the thympanic membrane in the adult  The remaining pharyngeal clefts separate due to the mesenchymal growth in between, and gives rise to no structure in the adult. Development of the Face The external human face develops between the 4th and 6th week of embryonic development. 4th week: The face is beginning to form by 5 swellings:  the frontonasal prominence,  a pair of maxillary prominences,  and a pair of mandibular prominences. A pair of ectodermal thickenings, called the nasal placodes form on the ventrolateral aspects of the frontonasal prominence and begin to enlarge. In the 6th week, the ectoderm at the center of each nasal placode invaginates to form an oval nasal pit, dividing the frontonasal prominence into the lateral and medial nasal processes. The medial nasal processes migrate toward each other and fuse to form the primordium of the bridge and septum of the nose. By the end of the 7th week, the inferior tips of the medial nasal processes expand laterally and inferiorly and fuse to form the intermaxillary process. The intermaxillary process gives rise to: Philtrum of the upper lip Premaxillary part of the maxilla and its associated gingiva Primary palate The primary and secondary palates fuse to form the definitive palate. The non-bony structures form the soft palate and uvula. Maxillary prominence continues to enlarge towards lateral nasal prominences and upwards to the cheek region. Craniofacial defects Treacher Collins syndrome (mandibulofacial disostosis): Zygomatic bones underdeveloped, malar hypoplasia Mandibular hypoplasia Outer ear deformation, downward sloping palpebral fissures It is autosomal dominant inherited, 60% new mutations, retinoic acid !! Cleft lip and cleft palate are distinct malformations based on their embryological formation, even though they often occur together. Pierre Robin syndrome: 1. arcus structures, especially the mandible, are affected Micrognatia Cleft palate Defect depends on both genetic and environmental factors The primary defect is caused by inability to develop mandible; After all, the posterior placement of the tongue prevents the palate racks from fusing It may also occur as a result of compression of the jaw by the chest in cases of oligohydramnios. Digeorge syndrome: 3rd and 4th pouch syndrome: Thymus and/or parathyroid hypoplasia or absence. hypocalcemia + cellular immunodeficiency + cardiac anomalies A Novel 22q11.2 Microdeletion in DiGeorge Syndrome DiGeorge syndrome associated with left lung aplasia Thank you for your attention!