Embryology Flashcards
what are the 3 major prenatal periods
- 1st week
- embryonic period
- fetal period
what happens in the first week
- fertilization
- penetration sperm into ovum
- zygote = fertilized egg
- zygote divides quickly, 2->4->8->16 cells
what happens in the embryonic period
- during the 2nd week up to the 8th week
- cell differentiation that will eventually form organs and systems
- stage where there is more congenital malformation
when is the fetal period
- 3-9 months
when the adult body is being described as 2 tubes, what does it mean
- larger, outer tube is the outside body wall
- smaller, inner tube is the digestive tract
- in between space has the heart, lungs, etc
- at either end of the tub is the mouth and the anus
what are the 3 embryonic (germ) layers and what does each layer form
- ectoderm
- mesoderm
- endoderm
what does the ectoderm form
- epithelium, skin, tooth enamel, nasal, nervous system, dentin, cementum, and pulp
what does the mesoderm form
- skeletal, muscle, circulatory systems (blood, lymph, and vessels)
what does the endoderm form
- stomach, intestines, lungs, etc
what is the primitive mouth
- also called the stomodeum, becomes the oral and nasal cavities
- begins developing in 3rd week
- clefting or infold of ectoderm = stomodeum
what is the oropharyngeal membrane
- also called the buccopharyngeal membrane
- where the endo and ecto contact when ectoderm folds inwards = oropharyngeal membrane
- future area of palatine tonsil
- ruptures at week 4 -> creating opening between primitive mouth and primitive digestive tract
what is rathke’s pouch
- forms before the rupture of oropharyngeal membrane
- extension of posterior roof of stomodeum in front of oropharyngeal membrane
- grows upwards and breaks off toward the developing brain
- meets with down extension from brain
- future pituitary gland (growth hormone) and connection with the stomodeum is soon lost
what is the frontal process
- outgrowth above the stomodeum
- future forehead, upper part of face, nasal septum, anterior part of palate
what is the branchial arch
- u-shaped bands tissue which produce cartilage, bone, nerves, muscles, glands and connective tissue of the face and neck
- 5 branches in total: I, II, III, IV, V
which branchial arch will develop into the maxillary and mandibular processes
- branchial arch I
all parts of the face and all parts for the oral and nasal cavities (except for the tongue) are formed by which 2 primary embryonic structures
- frontal process
- 1st branchial arch
what happens after the establishment of the stomodeum, frontal process and branchial arches
- budding of round process occurs on either end of the first branchial arch, which will become the maxillary and mandibular processes
how the round buds off the ends of the 1st branchial branches grow
- inwards and upwards
- right and left meet to form maxillary processes
what does the remaining band of the 1st branchial arch become
- the right and left mandibular processes
- future lower lip, lower jaw and lower cheeks
how is the nasal process established
- 2 infolds on each side of the lower border of the frontal process
- olfactory pits -> future nostrils
what 3 parts do the olfactory pits divide into
- median nasal process: future tip/center of nose, nasal septum, anterior part palate
- right lateral nasal process: future right side of nose
- left lateral nasal process: future left side of nose
how does the philtrum and upper lip develop
- median nasal process grows down -> becomes globular process -> philtrum
- right and left maxillary process grows toward midline and becomes the sides of upper lips
- fusion of right and left maxillary process within the globular process
- complete fusion should be within the 6th week
what 3 tissues form the palate and when does this occur
- end of the 2nd month
- forms from the left and right maxillary processes and the globular process
- ingrowth of these 3 tissues into the stomodeum: right and left palatine process -> most of the palate (sides), and the globular process (intermaxillary segment of the premaxilla will form the anterior part of the palate
- all 3 structures fuse in the roof of the mouth in a Y-shape pattern starting in the anterior region
when and how is the nasal septum established
- as the palate is forming (end of the 2nd month)
- nasal septum forms from median nasal process
- grows back and downwards
- fuses with right and left palatine processes in the center of the hard palate
when is the fusion of the soft tissue and the roof of the mouth complete
- at the end of the 3rd month (does not include the bony tissue)
what forms the tongue
- the first 4 branchial arches
- anterior: 1st arch
- poster: 2nd, 3rd and 4th arches
what type of abnormalities can occur from improper fusion
- cleft lip
- cleft palate
- median cleft of the lower jaw
- oblique facial cleft
- macrostomia
- cysts
what is a critical period for the cleft lip
- 6th to 8th week
- 6th week: fusion of the upper lip begins
- 8th week: fusion of the upper lip is completed
- failure of one or both maxillary processes to fuse with the globular process will result in either a unilateral or bilateral cleft lip
- this appears as absence of the center and adjacent lip
when does the palate fuse
- between 8 to 12 weeks
- 8th week: fusion of the palate begins
- 12th week: fusion of the soft tissues palate completed
- zipper like fusion premaxilla to lateral palatine processes (left and right) - anterior and posterior
what is a mild cleft palate
- cleft uvula, maybe some soft palate split
what is a moderate cleft palate
- cleft of the soft and hard palate but not to the alveolar ridge
what is a severe cleft palate
- soft, hard and alveolar ridge are involved
what is a unilateral cleft of the palate
- lack of fusion with one palatal process with the nasal septum = opening into the nasal cavity
what is a bilateral cleft of the palate
- no fusion on either side of the nasal septum = opening on both sides of the septum into the nasal cavity
cleft lip and palate complications
- difficulty nursing and feeding
- speech development
- appearance
- oronasal infections
