Anatomy Theme 7
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- Created by: Splodge97
- Created on: 11-05-17 20:53
What must occur during fertilisation?
Gametes must fuse to form diploid number when sperm penetrates corona radiata and zona pellucida (layers of ovum)
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What are the responses to fertilisation?
Cortical and zona reactions, 2nd stage of meiotic division, metabolic activation of the egg (ovum surface depolarised, causes large Ca2+ influxwhich activates signalling pathways to prevent double fertilisation)
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What is cleavage?
Parcelling of the ovum into smaller sub-units of the same size (no significant divison as growth restricted by zona pellucida). 2 cells in 30hrs, 4 cells in 40hrs, 16 cells in 3-4 days (morula formed).
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What is the morula?
16 cell stage at end of cleavage, inner and outer mass cells formed (differentiation determined by factors from uterine stroma)
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What is the blastocoel?
Formed when water is actively pumped into morula, pushing inner cell mass cell to the pole (forming the bastocyst by 4.5 days)
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What do the epiblast and hypoplast split the bilaminar embryo into?
Extra embryonic coelom and primitive yolk sac
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When is implantation?
Starts at 5 days, finishes at 11
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How is an allograft embryo sustained?
Immune supression in the syncytrophoblast (outer layer which provides early nutriition)
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What is gastrulation? When does it start?
When cells from cleavage move relative to each other so they are exposed to different factors from the uterine stroma. Starts at 16 days after implantation with pre-somite embryo (when three layers forming).
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When is the tri-laminar embryo complete?
18 days
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What does the ectoderm derive?
Nervous system, skin epidermis and sensory epithelia of nose, eye and ear
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When does the neural tube deepen? When is it complete?
Deepens at 19 days, complete by 21
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When does epidermis form?
At the end of neurulation
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What are the 31 somites derived from? What to they form?
The homeobox genes, form the spinal vertebrae
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What do the neural crest cells form?
In body = PNS, linings of body cavities and viscera (when migrated to lateral plate trunk mesoderm). In head = head and neck ganglia and (when fused with mesoderm) facial skeleton and connective tissue lining great vessels.
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What causes first arch syndrome?
Deformation of facial skeleton through incorrect migration of neural crest cells
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What does trunk mesoderm form?
Paraxial part = sclerome (forms connective tissue around vertebral column) and dermamyotome (forms dermis and muscle). Intermediate part = kidneys. Lateral plate part = mesoderm linings of body cavities and viscera (when fused with neural crest).
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What does head mesoderm form?
Paraxial part = somitomeres (fated outcomes in head and neck). Generally = dermis, muscle, majority of skull, mesoderm linings of cavities and viscera. With neural crest = facial skelton, connective tissue lining great vessels.
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When does lateral and cephalo-caudal folding of endoderm (to form GI tract) occur?
19-28 days
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Describe cephalo-caudal folding
Caused by rapid longitudinal growth of neural tube, embryo curves in on itself, slower-growing epidermis forms casing around early brain
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Describe lateral folding
Caused by rapid lateral growth of the somites, causes embryo to besome spherical in transverse section, gut (lined by mesoderm and epidermis) is formed at centre suspended by mesentry (replacing primitive yolk sac), mesoderm replaces amnion
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Where do the foregut and epidermis connect?
Bucco-pharyngeal membrane (later forms palatoglossal arch)
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What does each pharyngeal arch contain at 28 days?
Skeletal element, one cranial nerve, a mesoderm strand
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When does growth of the mesoderm of the pharyngeal arches occur?
35 days, pushes aside mesoderm, least in arch I so last place where endoderm and mesoderm communicate (forms external auditory meatus)
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What are the bony derivatives of arch I?
Mandibular process, maxillary process, Meckel's cartilage (disappears except malleus and incus), external auditory meatus (where communicates with endoderm)
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What are the muscular derivaties of arch I?
Muscles of mastication, anterior digastrc, mylohyoid, tensor veli palatini, tensor tympani (also tuberculum impar and lateral lingual swellings)
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What are the bony derivates of arch II?
Styloid process, lesser cronu and upper body of hyoid, stylohyoid ligament, Riechert's bar, stapes
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What are the muscular derivates of arch II?
Muscle sof facial expression, posterior digastric, stylohyoid, stapedius (also part of hyperbrachial eminence)
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What are the bony derivates of arch III?
Greater cornu and lower body of hyoid
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What are the muscular derivates of arch III?
Stylopharyngeous (plus part of hyperbrachial eminence)
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What are the bony derivates of arch IV/VI?
Cartilages of larynx
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What are the msucular derivates of arch IV/VI?
Muscles of pharynx, larynx and soft palate (excluding tensor veli palatini); also epiglottic swelling (and part of hyperbrachial eminence from VI)
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What is derived from pharyngeal pouch I?
Tubotympanic recess, pharyngotympanic tube, middle ear
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What is derived from pharyngeal pouch II?
Palatine tonsil and tonsillar fossa
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What is derived from pharyngeal pouch III?
Thymus gland, inferior parathyroid glands
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What is derived from pharyngeal pouch IV?
Superior parathyroid glands, C cells of thyroid
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What replaces the bucco-pharyngeal membrane in facial development?
Stomodeum (early mouth), occurs at 28 days
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What does the frontonasal prominence form?
Forehead, nose, philtrum and primary palate. Eroded by nasal placodes at 35 days (forms nasal cavities). By 40 days formed lateral (gives bridge of nose) and median (gives philtrum) nasal swellings.
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What do tha maxillary swellings form?
Main part of cheek, maxilla, zygoma, lateral upper lip, secondary hard palate and soft palate
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What do the mandibular swellings form?
Lower lip, rest of the cheek and mandible
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What forms the anterior 2/3 of the tongue?
Lateral lingual swellings overgrowing tuberculum impar
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What forms the posterior 1/3 of the tongue?
Hyperbrachial eminence arch III and IV parts overgow part from arch II
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Why are the tongue muscles innervated by XII?
Actually migrated from the occipital somites (not the pharyngeal arches)
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What is the primary palate derived from?
Intermaxillary segment (just below the nasal septum)
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What is the secondary palate derived from?
Palatal shelves (outgrowths of the maxillary swellings)
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When does palate development occur?
6.5-7.5 weeks
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What are primary and secondary palatal defects?
Primary are anterior to incisive fossa (marks point where primary and secondary palates fuse), secondary defects are posterior to it
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What causes median cleft lip?
Median nasal swellings don't fuse to form philtrum
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What causes a bilateral facial cleft?
Lack of fusion between mandibular and maxillary swellings (so lips long and thin)
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What causes microstomia?
Too much fusion between mandibular and maxillary swellings (so small, pursed mouth)
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When does petrous temporal bone development begin?
32 days (medial to tubotympanic recess)
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What occurs in petrous temporal bone development at 42 days?
Tegmen tympani grows laterally over the tubotympanic recess
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What occurs in petrous temporal bone development at 8 weeks?
Tympanic ring forms around the end of the tubotympanic recess, squamous part forms, styloid process forms (from 2nd arch cartilage)
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When is the mastoid process pulled down by its associated muscles?
2-3 years
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When does the mandibular fossa develop?
Neonatal (just after birth)
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Other cards in this set
Card 2
Front
What are the responses to fertilisation?
Back
Cortical and zona reactions, 2nd stage of meiotic division, metabolic activation of the egg (ovum surface depolarised, causes large Ca2+ influxwhich activates signalling pathways to prevent double fertilisation)
Card 3
Front
What is cleavage?
Back
Card 4
Front
What is the morula?
Back
Card 5
Front
What is the blastocoel?
Back
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