Embryo Test 3
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each of the black spaces below before clicking
on it to display the answer.
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| the fetal part of the placenta and the fetal membrane separate | the fetus from the endometrium
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| interchange of substances between the maternal and fetal blood takes place through | the placenta via the umbilical cord
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| what constitutes the fetal membranes | the chorion, amnion, yolk sac, and allantois. All develop from zygote except yolk sac and allantois
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| two components of the placenta (fetomaternal organ) | a fetal portion from the chorionic sac
a maternal portion from the endometrium
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| the placenta and umbilical cord function as the | transport system
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| function of the placenta and fetal membranes | protection
nutrition
respiration
excretion
hormone production
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| the placenta and fetal membranes are expelled as the | afterbirth (gravid endometrium)
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| the decidua refers to the | gravid endometrium (the functional layer which can be shead)
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| three regions of the decidua | decidua basalis- deep to conceptus forms maternal component
decidua capsularis-superficial overlying conceptus
decidua parietalis-remaining parts
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| formation of decidual cells | stromal cells enlarge in response to increasing progesterone. decidual cells enlarge as glycogen and lipids accumulate. decidual reaction
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| where do decidual cells degenerate? | in the region of the synctiotrophoblast to provide a source of nutrition and protection
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| when do anatomical arrangements for exchanges occur | end of third week
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| a vascular network is established | end of fourth week
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| chorionic villi covers entire chorionic sac | beginning of eighth week
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| when the chorionic villi degenerate they produce a smooth avascular area known as | smooth chorion, or chorion leave
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| as villi disappears, decidua basilis increase forming busy part of the sac known as | villous chorion or chorion frondosum
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| growth in size and thickness of placenta continues until... | 18 weeks
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| two parts of the placenta | fetal component- formed by villous chorion
maternal component- formed by decidua basalis
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| when is the decidual basalis almost entirely replaced by the fetal component | end of the fourth month
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| the fetal part of the placenta is attached to the maternal part by... | they cytotrophoblastic shell (external trophoblastic cells on maternal surface)
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| function of stem chorionic villi | anchor the chorionic sac to the decidual basalis via cytotrophoblastic shell
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| shape of the placenta is usually... | discoid shape
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| formation of placental septa | chorionic villi invade decidua basalis, tissue erodes and enlarges intervillous space producing wedge-shaped placental septa
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| function of placental septa | divides fetal part of placenta into cotyledons (consists of two or more stem villi)
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| the decidua basalis is almost entirely replaced by cotyledons by... | end of the fourth month
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| function of decidua capsularis | forms capsule and eventually obliterates the uterine cavity
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| decidua capsularis degenerates and disappears by | 22-24 weeks
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| intervillous space is derived from | lacunae
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| maternal blood enters intervillous space via | spiral endometrial arteries in the decidua basalis
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| formation of amniochorionic membrane | result of the rapid growth of the amniotic sac and its fusion with the smooth chorion
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| the ____ ruptures during labor | amniochorionic membrane
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| main exchange of materail takes place through ____ which arise from ____ | branch villi; stem villi
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| the circulation of the fetus and the mother are separated by... | placental membrane
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| function of the umbilical vein | carries oxygenated blood to the fetus
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| reducations of uteroplacental circulation may result in | fetal hypoxia (low O2), IUGR, or even fetal death
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| the intervillous space of mature placenta contains how much blood | 150 ml of blood replenished three or four times per minute
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| what happens to oxygen during uterine contractions | oxygen transfer to the fetus is decreased but does not stop
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| until about 20 weeks, the placental membrane consists of four layers: | synctiotrophoblast, cytotrophoblast, connective tissue of villus, and endothelium of fetal capillaries
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| eventually cytotrophoblast cells disappear over large areas leaving | thin synctiotrophoblast
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| at sites where the synctiotrophoblast comes in direct contact with the endothelium of the fetal capillaries ____ is formed | vasculosyncytial placental membrane
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| why does the placental membrane become progressively thinner | so that blood in many fetal capillaries is extremely close to the maternal blood in the intervillous space
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| formation of syncytial knots | during the third trimester, numerous nuclei in the syncytiotrophoblast aggregate to form the multinucleated protrusions or nuclear aggregations
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| a substance that forms near the end of pregnancy and consists of fibrin and other unidentified substances that result from againg | fibrinoid material
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| functions of the placenta | 1. metabolism- synthesizes glycogen, chloesterol, and fatty acids
2. transport- simple diffusion, facilitated diffusion, active transport, pinocytosis
3. infectious agents
4. endocrine secretion
5. umbilical cord
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| what are the endocrine secretions f the placenta | hCG- corpus luteum
hCS or hPL- breast preparation
hCT- thyroid
hCACTH or ACTH- pituitary
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| as the amnion enlarges it gradually... | obliterates the chorionic cavity forming the epithelial covering of umbilical cord
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| where is most amniotic fluid derived from | maternal tissue fluid by diffusion across the amniochorionic membrane from the decidua parietalis
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| major pathway for a passage of water and solutes in tissue fluid from the fetus before keratinization of the skin | through the skin
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| how is fluid secreted | by fetal respiratory tracts and enters the amniotic cavity
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| estimated daily rate of fluid to amniotic cavity from the respiratory tract | 300-400 ml
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| when does the fetus contribute to the amniotic fluid by expelling urine | the 11th week
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| volume of amniotic fluid progression | 20 ml at 10 weeks; 350 ml at 20 weeks; 700-1000 ml by 37 weeks
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| the fetus swallows up to ___ ml of amniotic fluid per day | 400 ml
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| critical functions of the amniotic fluid | permits symmetrical external growth, acts as a barrier, permits normal lung development, prevents adherence, ushions against injuries, controls body temperature, enables movement aiding in muscular development, homeostasis
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| formation and observance of the yolk sac | by the 20th week it is usually not visible anymore (1st trimester) sonographically early in the 5th weeksiginificance of the yolk sac
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| significance of the yolk sac | transfer of nutrients during 2nd-3rd weeks, blood development first occurs, incorporated as primitive gut during 4th week and gives rise to trachea, bronchi, lungs, and digestive tract, primordial germ cells appear and migrate to sex glands
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| fate of the yolk sac | atrophies as pregnancy advances. Uaually detaches from midgut by 6th week or persists as an ileal diverticulum or Meckel diverticulum
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| importance of allantois | blood formation during 3rd-5th week, blood vessels form from mesoderm, fluid diffuses through placental membrane for circulation, involutes to form urachus which becomes median umbilical ligament
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| dizygotic twins (fraternal) | 2 zygotes, 2 oocytes fertilized by individual sperm, 2/3 twins. 2 amnions, 2 chorions, and 2 placentas. may be fused
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| monozygotic twins (identical) | 1 zygote splits. division during blastocyst stage. develop in separate amniotic sac but same chorionic sac and share placenta (monochorionic diamniotic twin). umcommon: early sep of blastomeres result MZ twins with 2 amnions, 2 chorions, and 2 placentas
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| acardiac twins/ twin reversed arterial perfusion | complication of monochoronic twinning. acardiac twin (lacks organs and heart) and pump twin
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| triplets | 1 zygote (identical); 2 zygotes (identical and single); 3 zygotes
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| conjoined twins | 1 amnion, 1 chorion, 1 placenta with common blood supply. Blastomers fail to completely separate or adjacent embryonic discs fuse
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| twin-twin transfusion syndrome | fusion of placenta and vascular systems
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| parasitic twins | smaller body part protrudes from an otherwise normal host twin.
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| what is a mesentery | a double layer of peritoneum that begins as an extension of the visceral peritoneum covering an organ; it connects the organ to the body wall and conveys vessels and nerves to it
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| what is intraperitoneal viscera | the abdominal gut tube and its derivatives suspended in what will later become the peritoneal cavity
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| what is retroperitoneal | an organ is located behind the peritoneum from a view point inside the peritoneal cavity
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| retroperitoneal organs | kidneys and bladder. (ascending and descending colon, duodenum and pancreas are secondarily retroperitoneal)
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| what are the arteries supplying the primitive gut | celiac trunk (foregut) , superior mesenteric artery (midgut), and inferior mesenteric artery (hindgut)
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| when does the primitive gut form | during week 4 when te embryo folds and incorporates the dorsal part of the yolk sac
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| the endoderm of the primitive gut gives rise to | the epithelial lining of most of the digestive tract, biliary passages, and parenchyma of liver and pancreas
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| the epithelium of the cranial and caudal ends of the digestive tract is derived from | ectoderm of the stomodeum and proctodeum
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| muscular and connective tissue components of the digestive tract are derived from | splachnic mesenchyme surrounding the primitive gut
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| the lower respitory organs begin to develop during _____ and includes | 4th week. includes the larynx, trachea, bronchi, and lungs
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| development of the laryngotracheal groove | develops caudal to the 4th pair of pharyngeal pouches and indicates respiratory diverticulum. Endoderm gives rise: larynx, trachea, bronchi, and pulmonary epithelium. Splachnic meso: connective tissue, cartilage, and smooth muscle
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| as the diverticulum elongates it is invested with ___ and its distal end enlarges and forms ____ | splanchnic mesenchyme; tracheal bud
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| the opening of laryngotracheal tube becomes | primordial laryngeal inlet
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| during the 4th and 5th weeks, rapid proliferation of ____ converts the opening slit from the esophagus into a T-shaped glottis | 4th and 6th pharyngeal arch mesenchyme
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| cartilage develops from mesenchyme and grow to produce | arytenoid swellings
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| epithelial linings of larynx develops from | endoderm of the laryngotracheal tube
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| when does recanalization occur | by the 10th week and form laryngeal ventricles
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| what develops from the caudal part of hypopharyngeal eminence | epiglottis0from proliferation of mesenchyme in ventral 3rd and 4th pharyngeal pouches
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| the rostral part of the hypopharyngeal eminence forms | the posterior 3rd or pharyngeal part of the tongue
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| endodermal lining of the laryngotracheal tube differentiates into | epithelium of the trachea
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| the lung bud develops into 2 endodermal bronchial buds which grow into | the pericardioperitoneal cavities, the primordial of the pleural cavities
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| early in the 5th week, each bronchial bud enlarges into the | primordium of a primary bronchus
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| primary bronchi divide into | secondary bronchi and then tertiary bronchi
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| when do the respirator bronchioles develop | by week 24
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| lungs acquire a layer of visceral pleura from | splanchnic mesenchyme
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| the thoracic body wall is lined by a layer of | parietal pleura derived from somatic mesoderm
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| pseudoglandular period | 6-16 weeks. cranial segments of lungs mature faster. lumina of bronchi become larger. lung tissue highly vascularized. terminal bronchioles give rise to 2 or more respiratory bronchioles. respiration possible but not likely. saccules developed
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| terminal saccular period | 26 weeks to birth. terminal sacs arise. epithelium of alveoli becomes thin. blood-air barrier established. terminal saccules lined by type I alveolar cells or pneumocytes
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| function of pneumocytes | exchange
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| function of type II alveolar cells | secrete pulmonary surfactant (complex mixture of phospholipids and proteins). reaches adequate levels 2 weeks before birth.
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| ____ accelerates fetal lung development and surfactant production | glucocorticoid treatment
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| alveolar period | postnatal. 95% mature alveoli develop. alveoli separated by secondary septa. increase in size of lung.
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| at birth fluid in the lungs are cleared by 3 routes: | 1. mouth and nose by pressure on thorax
2. into pulmonary capillaries
3. into lymphatics and pulmonary arteries and veins
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| what causes hypoplasia | congenital diaphragmatic hernia
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| pharyngeal apparatus consists of | arches, pouches, grooves, and membranes
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| when do pharyngeal arches (brachial arches) develop | in the 4th week as neural crest cells migrate into the future head and neck
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| what does each arch consist of initially | mesenchyme derived from the intraembryonic mesoderm and is covered with ectoderm externally and endoderm internally
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| typical pharyngeal arches consist of... | aortic arch (arterial pattern of head and neck), cartilaginous rod, muscular component, and nerve
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| what is the first pair of pharyngeal arches | the primordium of the jaws which appear as surface elevations lateral to developing pharynx. (maxillary and mandibular processes form 1st pair)
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| how many pairs of pharyngeal arches are visible by the 4th week | 4 pairs
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| ____ arches are rudimentary and not visible on the surface | the 5th and 6th
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| what do SVE (special visceral efferent) components supply | muscles derived from pharyngeal arches
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| how is the sensory innervation of the ventral side of the face supplied | by the 3 divisions of the trigeminal nerve (3rd branch carries SVE fibers to muscles of mastication)
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| what do the aortic arches arise from | truncus arteriosus of primordial heart and terminates in dorsal aortae
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| what comes off the 1st aortic arch | maxillary arteries and may contribute to external carotid arteries
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| what comes off the 2nd aortic arch | stapedial arteries and hyoid artery
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| what comes off the 3rd aortic arch | common carotid arteries and internal carotid arteries
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| what comes off the 4th aortic arch | proximal part of the right subclavian artery and part of arch of aorta
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| what comes off the 6th aortic arch | part of the right and left pulmonary arteries, ductus arteriosus (shunts blood from pulmonary trunk to aorta by passing the lungs in fetus)
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| prominences of the 1st pharyngeal arch and nerve | maxillary prominence (rise to maxilla, zygomatic bone, and squamous part of temporal bone). Mandibular prominence (forms ventral mandible). Trigeminal nerve (CN5)- SVEs that innervate mastication muscles
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| what does the dorsal end of the 1st pharyngeal arch cartilage (meckel's cartilage) give rise to? | incus and malleous found in the middle ear
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| associations of the 2nd pharyngeal arch | stapes, styloid process of temporal bone, styloid ligament, part of hyoid bone, facial nerve (CN 7)- innervates muscles of facial expression, stapedius, and stylohyoid muscle
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| associations of the 3rd pharyngeal arch | part of hyoid bone, stylopharyngeus, glossopharyngeal (CN 9)- innervates stylopharyngeus
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| associations of the 4th and 6th pharyngeal arches (fuse to form laryngeal cartilages) | muscles of pharynx and larynx, striated muscles of esophagus, branches of vagus (CN 10)
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| derivatives of the 5th pharyngeal arch | it is rudimentary and has NO derivatives
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| derivatives of the 1st pharyngeal pouch | expands into a tubotympanic recess (distal part contacts 1st pharyngeal groove to become tympanic membrane). Middle part-tympanic cavity and mastoid antrum. Pharyngotympanic tube (eustacian tube, auditory tube)
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| derivatives of the 2nd pharyngeal pouch | largly obliterated as palatine tonsil develops but parts remain as tonsillar sinus
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| derivatives of the 3rd pharyngeal pouch | develops solid, dorsal bulbar part (becomes inferior parathyroid gland by week 6) and hollow, elongated ventral part (becomes thymus). Connection to pharynx reduced to a duct that degenerates
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| derivatives of the 4th pharyngeal pouch | forms dorsal bulbar and elongated ventral parts (ultimopharyngeal body). Connection with pharynx reduced to a duct that degenerates. Superior thyroid gland (5th week). Calcitonin Cells (C-cells, parafollicular cells)
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| function of the buccopharyngeal (oropharyngeal) membrane | separates the primitive mouth or stomodeum from the primitive pharynx
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| fate of the pharyngeal arches | during the 5th week, second pharyngeal arch enlarges and overgrows 3rd and 4th arches forming the cervical sinus. By end of 7th week, the 2nd -4th grooves and sinuses have disappeared
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| formation of pharyngeal pouches | primordial pharynx widens cranially to join stomodeum and narrows caudally to join esophagus. Endoderm of pharynx lines internal aspects of pharyngeal arches and passes into the balloon-like diverticula
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| function of pharyngeal grooves | grooves separates the arches externally. Only one pair of grooves contribute to postnatal structures- the first pair persists as the external acoustic meatus. The other grooves live in cervical sinus and are normally obliterated
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| function of the pharyngeal membranes | separates groove from pouch. The first pharyngeal membrane, along with intervening layer of mesenchyme, becomes the tympanic membrane
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| development of the thyroid gland | 1st endocrine to develop (24 days) begins as thickening of endoderm b/w 1st and 2nd pouches. Forms thyroid primordium (outpocket). descends as tongue grows. Connected by thyroglossal duct short. Hollow then solid & divides into rt and lt lobes by isthmus
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| how does the tongue begin to take shape | from a series of ventral swellings in the floor of the pharynx
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| in a 5-week old embryo, the tongue is represented by ____ in the venral regions of the 1st pharyngeal arches and ____ | a pair of lateral lingual swellings; two median unpaired swellings
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| where is the tuberculum impar located | between the 1st and 2nd arches
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| what does the copula do? | unites the 2nd and 3rd arches. It's formed by the fusion of the ventromedial parts of the 2nd pair of pharyngeal arches
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| function of the foramen cecum | marks the original location of the thyroid primordium and serves as a convenient landmark delineating the border between the original tuberculum impar and copula
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| how is growth of the body of the tongue accomplished | by great expansion of lateral lingual swelling with a minor contribution by the teberculum impar. lateral swellings overgrow the tuberculum and merge froming ant 2/3. Root of tongue derived from copula between 3rd and 4th pharyngeal arches forms post 1/3
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| nerve supply of the tongue | trigeminal- sensory mucosa ant 2/3 (1st arch)
Facial- tympani branch supplies taste ant 2/3 (2nd arch)
Glossopharyngeal- post 1/3 vallatate papillae (3rd arch)
Vagus- area superior to epiglottis (4th arch)
Hypoglossal- muscles of tongue excp 1 (4th a
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| development of salivary glands | begin as solid epithelial buds from the priimordial oral cavity. clubbed shaped ends of buds grow into mesenchyme. connective tissue derived from neural crest cells
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| development of parotid gland | first to appear. arise from oral ectoderm at angles of stomodeum. secretions start at 18 weeks.
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| development of the face from single frontonasal prominence | surrounds ventrolateral forebrain gives rise to optic vesicles for eyes. Frontal part forms forehead. Nasal part forms rostral stomodeum and nose
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| development of face from paired maxillary prominences | derivate of 1st pair pharyngeal arches. Form lateral boundaries of stomodeum
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| development of face from paired mandibular prominances | derivative of 1st pair of pharyngeal arches. Forms caudal boundary of stomodem. Lower jaw and lower lip first to form
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| how are prominences produced | by expansion of neural crest populations that originate from mesencephalic and rostral rhomencephalic neural folds.
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| what are nasal placodes | bilateral thickenings of the surface ectoderm on frontonasal prominence. Primordial of nasal epithelium. Lie in nasal pits (primordial of ant nares and nasal cavity)
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| function of nasolacrimal groove | separates lateral prominences from maxillary prominences
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| formation of the auricle | end of week 5 six auricular hillocks form around 1st pharyngeal groove
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| what does the intermaxillary segment give rise to | philtrum of upper lip. premaxillary part of maxilla and its associated gingiva. primary palate
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| summarize facial development based on the 5 facial primordial | 1. frontal nasal- forehead, dorsum and apex of nose.
2. lateral nasal-alae of nose
3. medial nasal- nasal septum, ethmoid, cribiform plate
4. maxillary- upper cheek and upper lip
5. mandibular-chin, lower lip, lower cheek
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| development of paranasal sinuses | some develop during late fetal period (maxillay sinuses ) remainder after birth. Form from outgrowths of nasal cavities and become pneumatic extensions.
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| development of primary palate (median palatine process) | (6 week) Primary palate from deep part of intermaxillary segment (formed by medial nasal prominences between internal surfaces). Forms premaxillary maxilla and small part of hard palate
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| secondary palate (lateral palatine process) | (6 week) from internal mesenchymal projections primordium of the hard and soft parts of palate
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| fusion of nasal septum and palatine processes | begins anteriorly during 9th week and completes postural by 12th week
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| what does the medial palatine raphe indicate | the lie of fusion of the lateral palatine processes
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| incisive fossa development | from nasalpalatine canal. common opening for small right and left incisive canals. Irregular suture on each side indicates fusion of primary and secondary palates
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| cleft lip | results from failure of mesenchymal masses in median nasal and maxillary prominences to merge. Genetic and environmental factors interfere with neural crest cells of 1st pharyngeal arch
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| cleft palate | results from failure of mesenchymal masses in the palatine processes to meet and fuse
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