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20 Cards in this Set
- Front
- Back
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Differential Growth
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- not all organs grow at the same rate, spinal cord stops growing, while the vertebral column continues to grow
- both eyes used to be on the sides like fish and birds, but the brain in the back grows faster, the eyes seem to have rotated towards the front |
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Two types of unions
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1. merging: is a union process where two bumps are united together by filling in from mesenchyme below, NOT a complex process
a. separte structures - mesenchyme covered with epithelium b. structures make contact c. epithelium fuses d. epithelium begins to break down and disappear (or change into mesenchyme) e. epithelium is gone and fusion is complete 2. Fusion: is a union of structures that are entirely separate from one another, more complex, more likely to go wrong, must come into direct contact with each other, epithelium coverings must fuse with each other, then break down, continuity b/w mesenchyme from both |
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The Face
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- at 5th week gestation, stomodeum, or oral pit or future mouth is surrounded by 5 lumps
- above is the frontal or frontalnasal process (or eminence, prominence), will form the forehead, middle of the nose, part of the upper lip and dental arch - below is the mandibular arch (1st arch) which is divided into maxillary and mandibular processes - mandibular process will form the mandible and other contents of the lower jaw, both sides meet as a dimple on the chin - 5 lumps around the stomodeum (primitative oral cavity), separated from the pharynx by the buccopharyngeal membrane (where ectoderm meets with the mesoderm, same as other orifices) |
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Maxillary Process
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form the cheek, parts of the upper lip, the maxillary, zygomatic and bit of temporal bone
- 2nd arch = hyoid arch - 3rd arch, 4th arch, and 6th arch (5th dissappeared) - Nasal Placodes: thickening of epithelium - Nasal pits - future nostrils - Nasomedial processes - or medial nasal proc - nasolateral processes - or lateral nasal proc |
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Mandibular Arch
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- two portions of the mandibular arch (arch 1) are maxillary and mandibular prominences and processes
- both nasomedial processes merge to be intermaxillary segement to form: the middle of the nose [crest, tip], the philtrum of the upper lip, part of dental arch with 4 incisors, and the primary palate - both nasolateral processes will form the sides and wings (alae) of the nose - upper lip/jaw is formed by both nasomedial processes and both maxillary processes - lower lip/ jaw is formed by mandibular prominences |
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clinical condersideration - failure of union
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- failure of union b/w the processes results in cleft lip (1/1000 births, more in males)
- in whites 1/700, more in asians 3/2000, fewer in blacks 1/2000 - more in white males - may be unilateral or bilateral - median cleft lip or hare lip - the maxillary process joins with the mandibular process to determine the size of the mouth - failure to join = macrostomia or "big mouth" - join to much = microstomia or small mouth |
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maxillary process
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it joins the nasolateral process on each side of the nose:
- to form the nasolacrimal groove - later becomes the nasolacrimal duct - dilated at upper end of the lacrimal sac - to drain tears from the eye to the nose - failure to join = oblique facial cleft or oronasal optic cleft, rarely occurs - small bumps b/w the mandibular arch and the hyoid arch will become the ears |
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pharyngeal (brachial) arches
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- core of mesenchyme (mesoderm + neural crest cells), covered outside by ectoderm, inside by endoderm
- neural crest will give off mesectoderm, which will become bones and consist of head and neck - there are 6 arches, the 5th disappears - each has a muscular, nerve, skeletal, and arterial component |
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mandibular arch (1)
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- maxillary and mandibular processes
- Nerve: CN V [trigeminal n.], maxillary and mandibular divisions - Muscles: mastications [temporal, masseter, medial, lateral pterygoids], mylohyoid; anterior belly of digastric; tensor palatine, tensor tampani - skeleton: premaxilla, maxilla, zygomatic bone, part of the temporal bone, Meckel's cartilage, malleus, incus, anterior ligament of malleus, sphenomandibular ligaments |
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Hyoid arch (2)
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- nerve: CN IIII [facial n.]
- muscles: fascial expressions[ buccinator, auricularis, frontalis, platysma, orbicularis oris, orbicularis oculi] posterior belly of digastric; stylohyoid,stapedus - skeleton: stapes; styloid process; stylohyoid ligament; lesser horn and upper portion of body of hyoid bone |
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Arch 3
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- nerve: CN IX [glossopharyngeal]
- muscles: stylopharyngeus - skeleton: greater horn and lower portion of the hyoid bone |
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Arch 4 - 6
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- nerve: CN X [vagus], superior laryngeal branch [nerve to 4th arch], recurrent laryngeal branch [nerve to 6th arch]
- muscle:cricothyroid, levator palantine, constrictors of the pharynx, intrinsic muscles of the larynx - skeleton: laryngeal cartilages (thyroid, cricoid, arytenoid, corniculate, cuneiform) |
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pharyngeal clefts
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- are grooves on the outside of the embryo (ecto)
- 1st cleft = external auditory meatus - others form cervical sinus, disappear later - if not, cervical or brachial cyst may occur, and may have fistula |
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pharyngeal pouches
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- are grooves on the inside of the embryo (endo)
- 1st pharyngeal pouch = auditory or eustachian tube, and middle ear caivty - tympanic membrane, ecto + endoderm |
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brachial or lateral cervical cyst
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may have fistula opens to the inside or outside
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mandibular hypoplasia
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genetic defect, abnormal neural crest cell migration or differentiation, causing Treaher Collins' syndrome
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the palate
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- single large cavity at the beginnig, no seperation b/w an oral cavity and a nasal cavity
- the palate develops from both maxillary processes and from the nasomedial process - nasomedial process form primary palate - maxillary process form palatal shelves, which will form secondary palate - the shelves change from vertical position to horizontal position, "flip up" - lower jaw grows downward and outward, and moves the tongue down with it "drop" - incisive foramen is in the midline where primary and secondary palate meet - palatine shelves are in vertical position on each side of the tongue - palatine shelves are in horizontal position, must override the tongue, the tongue moves forward and downward along with the lower jaw - both shelves contact each other and fusion occurs to form secondary palate. Primary palate fuses with secondary palate. Nasal septum grows downward and fuse. Now single cavity is divided into 1 oral cavity and 2 nasal cavities |
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cleft palate/ cleft uvula
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- failure of any event causes cleft palate (1/2500 births, more in females), cleft uvula
- which may involve primary (anterior), or secondary (posterior) palate or both - it may occur alone, or with cleft lip, or with other facial malformations - clefts can be: lip or palate or both, unilateral or bilateral, complete or incomplete |
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the tongue
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- develops on the floor of the oral cavity, but grows rapidly to expand into nasal cavity
- from 1st arch, 2 lateral lingual swellings, and one tuberculum impar, to form anterior 2/3 of tongue - form 3rd and 4th arches, to form posterior 1/3 and root of tongue - occipital somites form tongue muscles |
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tongue defects
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- normally, extensive cell degernation occurs under the tongue, only the frenulum left
- if not = ankyloglossia or tonque-tie, frenulum extends to the tip of the tongue - microglossia = to small tongue, hypoplasia, too little swellings - macroglossia = to big, hyperplasia, trouble speaking, biting tongue - bifid or fork tongue = incomplete union of 2 lateral lingual swellings - frenectomy: to fix, or for comestic reaction |
