University:
American Career College
Course:
PHYS111 | Human Physiology
Academic year:

2020
Views:

111

Pages:

40
Author:

astralniew2

Head and Neck development Formation of the head • Neural crest (blue) • Lateral plate mesoderm • paraxial mesoderm • Ectodermal placodes (epipharyngeal placods) ectodermal placodes Pharyngeal Apparatus  The head and neck region of four and fifth week human embryo somewhat resemble these regions of a fish embryo of comparable stage  This explains the former use of designation branchial apparatus  Bronchial is derived from the Greek word bronchia or gill Pharyngeal Apparatus Pharyngeal apparatus consists of: 1. 2. 3. Pharyngeal arches Pharyngeal pouches Pharyngeal clefts The stomodeum Pharyngeal Arches  Each pharyngeal arch consists of a core of mesenchyme  Externally by ectoderm and internally by endoderm  In the third week the original mesenchyme is derived from mesoderm (paraxial and lateral plate)  During the fourth week most of the mesenchyme is derived from neural crest cells that migrate into the pharyngeal arches Fate of Pharyngeal Arches A typical pharyngeal arch contains:  An aortic arch, an artery that arises from the truncus arteriosus of the primordial heart  A cartilaginous rod that forms the skeleton of the arch  A muscular component that differentiates into muscles in the head and neck  A nerve that supplies the mucosa and muscles derived from the arch Arteries of Pharyngeal Arches Nerves of Pharyngeal Arches The first pharyngeal arch  Bones:  Dorsal portion, the maxillary process  Premaxilla, maxilla, zygomatic bone, and part of the temporal bone  Ventral portion, the mandibular process:    Meckel's cartilage form the incus and malleus Mandible: intermemberanous ossification Muscles: muscles of mastication (temporalis, masseter, and pterygoids), anterior belly of the digastric, mylohyoid, tensor tympani, and tensor veli palatini.  The nerve: the muscles of the first arch is provided by the mandibular branch of the trigeminal nerve  Supply to the skin of the face  Ophthalmic, mandibular and maxillary branches Second Pharyngeal Arch (hyoid arch)  The cartilage and bone: (Reichert's cartilage)   Muscles:   The stapes, styloid process of the temporal bone, stylohyoid ligament, and the lesser horn and upper part of the body of the hyoid bone Stapedius, stylohyoid, posterior belly of the digastric, auricular, and muscles of facial expression. Nerve : The facial nerve, the nerve of the second arch, supplies all of these muscles. Third Pharyngeal Arch  The cartilage:   The muscles:   Produces the lower part of the body and greater horn of the hyoid bone The stylopharyngeus muscles. Nerve:  Glossopharyngeal nerve Fourth and Sixth Pharyngeal Arches  Cartilaginous components:   Muscles:    Thyroid, Cricoid, Arytenoid, Corniculate and Cuneiform The fourth arch (cricothyroid, levator palatini, and constrictors of the pharynx) The sixth arch: intrinsic muscles of the larynx Nerve:  The superior laryngeal and recurrent laryngeal branches of the vagus Pharyngeal pouches First Pharyngeal Pouch: primitive tympanic or middle ear cavity auditory (eustachian) tube Second Pharyngeal Pouch: palatine tonsils (migration in 3-5th months) Pharyngeal pouches  Third pharyngeal pouch  Dorsal wing:    inferior parathyroid gland(5th week) Ventral wing: thymus Fourth pharyngeal pouch   Dorsal region: Superior parathyroid gland Ventral region: Ultimobranchial body  Parafouicular, or C cells:  Calcitonin secretion Pharyngeal clefts The first cleft: external auditory meatus Birth Defects Involving the Pharyngeal Region   Ectopic Thymic and Parathyroid Tissue Branchial Fistulas  Lateral cervical cyst Neural Crest Cells and Craniofacial Defects    Treacher Collins syndrome (mandibulofacial dysostosis) Robin sequence DiGeorge anomaly   velocardiofacial syndrome (VCFS) Hemifacial microsomia (oculoauriculovertebral spectrum, or Goldenhar syndrome). Branchial Fistulas Birth Defects Involving the Pharyngeal Region Treacher Collins syndrome Robin sequence DiGeorge anomaly Hemifacial microsomia Face  Facial prominences  Maxillary prominences   Mandibular prominences Frontonasal prominence      Nasal (olfactory) placodes, Nasal pits Nasal prominences Lateral nasal prominences; Medial nasal prominences End of 4th week 5th week Tongue Tongue  Appears in embryos of approximately 4 weeks  Two lateral lingual swellings ,One medial swelling: tuberculum impar  A second median swelling, the copula, or hypobranchial eminence,  a third median swelling: Epiglottal swellings Tongue sensory innervation  Since the mucosa covering the body: by the mandibular branch of the trigeminal nerve.   The posterior part originates from the second, third, and part of the fourth pharyngeal arch.  The fact that sensory innervation: the glossopharyngeal nerve  The epiglottis and the extreme posterior part: superior laryngeal nerve Motor and taste innervation  Tongue muscles: myoblasts originating in occipital somites. Hypoglossal nerve.  Special sensory innervation (taste):   The anterior two thirds of the tongue: chorda tympani branch of the facial nerve, The posterior third: glossopharyngeal nerve. Thyroid Thyroid gland     An epithelial proliferation in the floor of the pharynx between the tuberculum impar and the copula Foramen cecum, thyroglossal duct It reaches its final position in the seventh week To function : end of the third month, Face  Facial prominences  Maxillary prominences   Mandibular prominences Frontonasal prominence  Nasal (olfactory) placodes,   Nasal pits Nasal prominences   End of 4th week Lateral nasal prominences; Medial nasal prominences 5th week Nose Nose 5th week 6th week Nose 7th week 10th week Intermaxillary segment and secondary plate    A labial component Upper jaw component, Palatal component, Secondary palate Secondary palate Cleft Palate Nasal cavities  During the sixth week, the nasal pits are deepen  Oronasal membrane    primitive choanae definitive choanae: with formation of the secondary palate Paranasal air sinuses Teeth Teeth