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Embryo Farmer Test 4
Embryology - Dr. Farmer - Test 4
| Question | Answer |
|---|---|
| Primitive Gut | Tube of endoderm; formed in week 4 by lateral, cranial, and caudal folding |
| Divisions | Pharynx-buccopharyngeal membrane to tracheobronchial diverticulum; Foregut-pharynx to duodenal bile duct entrance; Midgut-Duodenum distal to bile duct entrance to prox 2/3 of transverse colon; Hindgut-Dist 1/3 transverse colon to cloacal membrane |
| Germ Layer Sources | Endoderm-epithelial lining and glands of mucosa, parenchyma of digestive glands; Splanchnic mesoderm-supporting structures including muscular walls and peritoneum |
| Arterial Supply | Foregut-Celiac a.; Midgut-Superior Mesenteric a.; Hindgut-Inferior Mesenteric a. |
| Foregut | Esophagus, Stomach, Duodenum, Liver, Gall Bladder, Pancreas |
| Esophagotracheal septum | Separates digestive and respiratory tubes |
| Esophageal Muscular Coat | From mesoderm-upper 2/3 striated, lower 1/3 smooth |
| Atresia | Prox esophagus portion ends in blind sac; Leads to polyhydramnios when accompanied by esophagotracheal fistula |
| Esophagotracheal fistula | Dist esophagus connected to trachea; Results in polyhydramnios when accompanied by atresia |
| Stomach | Dilation of foregut-week 4; Rotates longitudinally 90 degrees clockwise, originates on dorsal side-now on left, Anterior posterior axis clockwise-originally dorsal side now inferior and forms greater curvature |
| Pyloric stenosis | Narrowing of pyloric lumen; Hypertrophy of m. layer; Obstructs passage of food; Projectile vomiting after feeding |
| Duodenum | Formed by foregut-prox to entrance of bile duct- and midgut; C-shape caused by stomach rotation; Lumen obliterated during 2nd month and then recanalized |
| Liver | Liver bud from prolif. endoderm in wk 3; Penetrates septum transversum (mesodermal plate b/t pericardial cavity and yolk sac stalk) and expands; Connection to foregut forms bile duct; Ventral outgrowth of bile duct forms gall bladder and cystic duct |
| Liver continued | Hepatic sinusoids - from vitelline vv.; CT, Kupffer's and hematopoeitic cells from mesoderm; Functions-hematopoeisis (uterine life) and bile production in wk 12 |
| Mesenteries | Dorsal mesogastrium; Ventral mesogastrium |
| Dorsal Mesogastrium | Greater omentum, attached to greater curvature of stomach (originally dorsal) |
| Ventral mesogastrium | From septum transversum; Divided by developing liver into 2 parts-lesser omentum-b/t liver and stomach, falciform ligament-b/t liver and ventral body wall |
| Pancreas | 2 buds (dorsal/ventral) of endoderm in duodenal region; Rotation of duodenum causes ventral bud to lie below and behind dorsal bud; Islets of Langerhans-2nd month-insulin secretion during month 5 |
| Dorsal Bud | Dorsal mesentery-attached to duodenum via duct of Santorini; Major portion of gland; Dist portion of main pancreatic duct (of Wirsung); Dorsal duct may persist as accessory pancreatic duct |
| Ventral Bud | Close to bile duct; attached to duodenum via duct of Wirsung; Uncinate process; inferior part of pancreatic head; prox part of main pancreatic duct (of Wirsung) |
| Annular Pancreas | Ventral pancreatic bud encircles duodenum and may constrict or obstruct it |
| Accessory pancreatic tissue | Most commonly found in Stomach or Meckel's Diverticulum |
| Midgut | Communicates with yolk sac via vitelline duct; Supplied by superior mesenteric a.; In adult, extends from junction of bile duct with duodenum to dist 1/2 transverse colon |
| Primary intestinal loop | From rapid elongation of gut tube; Cephalic limb-dist duodenum, jejunum, prox ileum; Caudal limb-dist ileum, cecum, appendix, ascending colon and prox 2/3 transverse colon |
| Physiological herniation and rotation | During wk 6 d/t rapid growth, esp. of cephalic limb; Midgut occupies extraembryonic coelom in umbilical cord; rotates 270 degrees CCW around sup. mesenteric a., further elongation/coiling |
| Physiological herniation/rotation continued | Retraction occurs in wk 10-jejunum 1st to reenter abdomen, cecal bud (forms cecum and appendix) last to reenter abdomen |
| Hindgut | Dist 1/3 transverse colon; Descending colon; Sigmoid colon; Rectum; Prox anal canal; Internal lining bladder/urethra |
| Cloaca | Endoderm-lined cavity in contact with surface ectoderm at cloacal membrane; Terminal portion of hindgut; Divided by urorectal septum into primitive urogenital sinus and anorectal canal at wk 7; Cloacal membrane divided into urogenital and anal membranes |
| Proctodeum | Anal pit; Ectodermal depression; Separated from anorectal canal by anal memb; When memb ruptures, completes canal to surface-pectinate line, upper anal canal (endoderm of hindgut) of columnar epi, lower (ectoderm of proctodeum) of strat squam epi |
| Meckel's Diverticulum | Persistent portion of vitelline duct; May contain heterotopic pancreatic tissue or gastric mucosa |
| Metanephric | Definitive kidney-functional by wk 10; Sacral region-wk 5, moves cranially d/t lumbar and sacral growth; Ureteric bud; Metanephric tissue cap |
| Ureteric Bud | Metanephric diverticulum-outgrowth from mesonephric duct near cloacal entrance, forms collecting system-ureter, pelvis, calyces, collecting tubules |
| Metanephric Tissue Cap | Sacral region of urogenital ridge-induced by presence of collecting tubules to form renal vesicles (metanephric vesicles), vesicles-caps form nephron-glomerulus (blood vessel), Bowman's capsule, PCT, DCT, loop of Henle |
| Urogenital Sinus | Bladder/Urethra; Upper region(vesicle)-bladder-continuous with allantois, remnant forms med umbilical ligament (urachus), connects apex to umbilicus; Mid region (pelvic)-narrow canal, becomes prostatic/membranous urethra and female urethra |
| Urogenital Sinus continued | Lower region (phallic)-becomes penile urethra and lower vagina |
| Gonads-Origin | Gonadal(genital) ridge medial to mesonephric kidney; Primordial germ cells-from endoderm of yolk sac, migratory cells to genital ridge by wk 6; Gonads develop only when germ cells are present |
| Indifferent Gonad | Mesenchymal medulla and epithelial cortex; Primitive sex cords; TDF (Testis Determining Factor) |
| Primitive Sex Cords - Male | Invagination of cortical epithelium into medulla; Medullary cords canalize at puberty to become seminiferous tubules with spermatogonia and Sertoli cells, interstitial cells produce testosterone at wk 8 |
| Primitive Sex Cords - Female | Invagination of cortical epithelium into medulla; Medullary cords degenerate, 2nd generation of cords of invaginating epithelium forms cortical cords, form follicular cells |
| TDF | Testis Determining Factor; Gene carried on Y chromosome; Presence causes development of testis; Absence causes development of ovary |
| Indifferent Ducts | Mesonephric (Wolfian) and paramesonephric (Mullerian); Hormonal control-androgens, MIS, estrogens |
| Male ducts | Mesonephric duct forms epididymis, vas deferens, ejaculatory duct; MIS (from Sertoli cells) causes regression of paramesonephric ducts, remnant forms appendix, testis |
| Female Ducts | Mesonephric duct regresses; Paramesonephric duct forms oviducts, uterus, upper vagina; Lower portion of vagina forms from urogenital sinus |
| External genitalia-indifferent stage | Cloacal folds-divided into urethral folds (urogenital folds) and anal folds; Genital tubercle-anterior to cloacal membrane; Genital swellings(labioscrotal swellings)-lateral to urethral folds |
| Male external genitalia | Changes induced by androgens; Genital tubercle-penis; Urethral folds-Penile urethra; Genital swellings-Scrotum |
| Female External Genitalia | Estrogen induced; Genital tubercle-clitoris; Urethral folds-labia minora; Genital Swellings-labia majora |
| Gubernaculum | Ligament b/t scrotal swellings and testis; Provides pathway for descent |
| Descent of Testis | Causative factors-relative growth of abdominal cavity, androgens stimulus |
| Kidney anomalies | Multicystic dysplastic kidney (polycystic disease)-malformation of nephrons, requires transplant; Renal agenesis-degen of ureteric bud, unilateral is asymptomatic, bilateral results in oligohydramnios; Duplication of ureter-splitting of ureteric bud |
| Kidney anomalies continued | Pelvic/horseshoe kidney-failure of kidney to ascend, fusion of kidneys |
| Urachal Fistula | Allantois persists |
| Urachal cyst or sinus | Portion of allantois persists |
| Uterine canal | Duplication of uterus or vagina-failure of ducts to fuse; Bicornate uterus-partial fusion |
| Hypospadias | Urethra opens on inferior penis, incomplete fusion of urethral folds |
| Epispadias | Urethra opens on dorsum of penis, genital tubercle develops inferior to urethral folds |
| Congenital inguinal hernia | Intestinal loops pass through inguinal canal into scrotum |
| Cryptorchism | Testes remain in pelvis or unguinal canal |
| Pseudohermaphroditism | Genotypic sex masked by phenotype of opposite sex; Male-46XY-may have mutant testosterone; Female-46XX-congenital adrenal hyperplasia |
| AIS | Androgen Insensitivity Syndrome-testicular feminization syndrome; Normal appearing females; Normal breast development; No menstruation; Medically, legally, socially female; Faulty receptors |
| Pharyngeal Arches | Bars of mesenchyme separated by clefts exteriorly and pouches internally; 1,2,3,4,6; 5 doesn't form |
| Arch 1 | Mandibular arch; Maxillary process-maxilla, zygomatic, part of temporal; Mandibular process-Meckel's cartilage, mandible, incus, malleus; Mm-mastication, mylohyoid, anterior digastric, tensor tympani, tensor palatine; Nn-motor-V3, sensory-V1,V2,V3 |
| Arch 2 | Hyoid Arch; Skeletal-stapes, styloid process, stylohyoid lig, lesser horn/upper body hyoid; Mm-stapedius, stylohyoid, posterior digastric, facial expression; Nn-CN VII |
| Arch 3 | Skeletal-lower body/greater horn hyoid; Mm-stylopharyngeus; Nn-CN IX |
| Arches 4 and 6 | Laryngeal cartilages-thyroid, cricoid, arytenoid, corniculate, cuneiform; Mm-4-cricothyroid, pharynx constrictors, 6-mm. of larynx; Nn-4-sup laryngeal n.-constrictors, 6-recurr laryngeal n.-intrinsic |
| Pharyngeal pouches | Dilation of endodermal tube wall; Pouches 1 through 5 |
| Pouch 1 | Tubotympanic recess-contacts cleft 1, dist forms primitive tympanic (middle ear) cavity, prox forms eustachian tube |
| Pouch 2 | Tonsillar crypts of palatine tonsil |
| Pouch 3 | Forms dorsal/ventral wings; Dorsal wing-inferior parathyroid gland, ventral wing-thymus |
| Pouches 4 and 5 | Found together; 4- forms superior parathyroid gland; 5 forms ultimobranchial body-incorporated into thyroid gland to form parafollicular cells (produce calcitonin) |
| Pharyngeal Clefts | Grooves on external surface b/t arches; 1st forms EAM; 2 through 4 form cervical sinus (temporary)-cutoff from surface by rapid growth of arch 2 |
| Anterior 2/3 of tongue | Oral part-arch 1; Tuberculum impar-median tongue bud; Lateral lingual swellings-dist tongue buds; Median sulcus (superficial) and lingual septum(internal) mark fusion of lat ling swellings; Separated from root by transverse groove-terminal sulcus |
| Posterior 1/3 of tongue | Pharyngeal (root); caudal to foramen cecum (opening of thyroglossal duct); Copula(arch 2)-overgrown and disappears; Hypobranchial eminence (arches 3 and 4)-separated from oral part by terminal sulcus |
| Tongue innervation | Motor-CN XII-myoblasts derived from occipital myotomes; Taste-ant-CN VII-facial n, chorda tympani, post-CN IX-glosspharyngeal n; General sensory-ant-V3, post-mostly CN IX, some CN X above epiglottis |
| Thyroid | Wk4- 1st endocrine gland to appear; Thickening in pharynx forms thyroid diverticulum; Connected to tongue via thyroglossal duct; 2 lobes connected by isthmus; Pyramidal lobe in 1/2 of people, sup to isthmus, persistent inf end of thyroglossal duct |
| Thyroid Hormones | After week 11 |
| Formation of face | From mesenchyme derived from neural crest; wks 4 to 8; stomodeum; 5 primordia surrounding stomodeum; nasal placodes and nasal pits |
| Stomodeum | Primitive mouth; And end of gut tube; Buccopharyngeal membrane (prechordal plate) |
| 5 Primordia Surrounding Stomodeum | Frontonasal prominence-rostral boundary of stomodeum; Paired maxillary prominences-lateral boundaries of stomodeum; Paired mandibular prominences-caudal boundary of stomodeum |
| Nasal placodes and nasal pits | Nostrils and nasal cavity; Week 5; Ectodermal thickenings on ventrolateral part of frontonasal prominence; Pits surrounded by medal and lateral nasal prominences |
| Medial Nasal Prominences | Pushed medially by developing maxillary prominences; Fusion in midline forms intermaxillary segment-philtrum of upper lip, portion of maxilla with 4 incisor teeth, primary palate |
| Lateral Nasal Prominences | Separated from maxillary prominence by groove-nasolacrimal groove-will form nasolacrimal duct b/t eye and nasal cavity |
| Primordial contributions to face formation | Frontonasal prominence-forehead, nose bridge, med/lat nasal prominences-medial-philtrum, crest/tip of nose, lateral-alae of nose; Maxillary prominences-cheeks lat upper lip; Mandibular prominences-lower lip |
| Developmental changes and proportions | Early fetus-flat nose, lat eyes, mandible underdeveloped; Late fetal-eyes medial, forehead enlarges; Small face at birth-jaws still small, unerupted teeth, small nasal cavities and maxillary sinus |
| Intermaxillary segment | From medial nasal prominence; Upper jaw-4 incisors; Palatal-primary palate-wk 6; Rostral part of nasal septum joins portion from frontonasal prominence |
| Secondary palate | Major part of definitive palate; Palatine shelves-lat palatine processes, from maxillary prominence-wk 6, lat to tongue, wk 7-ascend above tongue and fuse midline, fuse ant w/ primary palate, sup w/ nasal septum |
| Incisive foramen | Midline landmark b/t primary and secondary palates |
| Nasal cavities | Nasal sacs within nasal pits separated from oral cavity by oronasal membrane; Rupture of oronasal membranes creates openings (primitive choanae) posterior to primary palate; Development of secondary palate shifts openings (definitive choanae) posteriorly |
| 1st arch syndrome | Failure of neural crest migration; Treacher Collins Syndrome0underdeve zygomatic bones and mandible, lower eyelid defects, deformed external ear and sometimes inner and mid ear; Pierre Robin syndrome-hypoplasia of mandible, cleft palate, eye/ear defects |
| 3rd and 4th Pouch Syndrome | Di George Sequence-hypoplasia of thymus and parathyroid glands, cardiac anomalies (aortic arch anomalies, persistent truncus arteriosus), malformed mouth |
| Ankyloglossia | Tongue-tie-extended frenulum |
| Thyroglossal Cyst/Fistula | Remnant of thyroglossal duct |
| Cleft lip and palate | Incisive foramen distal b/t ant/post clefts; Uni or bilateral; Ant clefts-cleft lip/upper jaw b/t primary/secondary palate, part of complete lack of maxillary prominence fusion with med nasal prominence |
| Cleft lip and palate continued | Posterior clefts-cleft secondary palate and uvula, lack of palatine shelf fusion |
| Oblique facial cleft | Failure of maxillary prominence to fuse with lateral nasal prominence, exposed nasolacrimal duct |
| Median cleft lip | Failure of fusion of medial nasal prominences, often accompanied by neural defects |
| Optic vesicle | Evaginates from forebrain wk4; induces surface ectoderm to form lens placode; Invaginates to form optic cup and choroid fissure; Post 4/5 optic cup (pars optica retinae) forms retina-pigment, neural layers and intraretinal space |
| Optic vesicle continued | Anterior 1/5 optic cup (pars ceca retinae) forms iris and ciliary body; Choroid fissure encloses hyaloid a.-a. forms central a. of retina, grow in n. fibers to form optic n. |
| Lens placode | Invaginates, loses contact with surface (wk 5), forms lens vesicle; Formation of primary lens fibers from posterior wall fills lumen of vesicle |
| Mesenchyme of eye | Choroid-vascular, continuous with pia mater of brain; Sclera-tough, fibrous, continuous with dura mater of brain |
| Cornea | Epithelial layer from surface ectoderm, stromal layer continuous with sclera; Epithelial layer from mesenchyme |
| Anomalies of Eye | Colobama iridis-choroid fissure fails to close where iris forms; Congenital cataracts-opaque lens, genetic, rubella infection; Micropthalmia-Small eyeball, intrauterine CMV or rubella infection, may be d/t trisomy 13 |
| Inner Ear | Otic placode-otic vesicle-wk4-placode thickening of surface ectoderml invaginates and forms otic vesicle-dorsal portion-memb labyrinth, utricle, semicircular ducts, endolymphatic duct |
| Inner Ear continued | Ventral wall of otic vesicle-saccule, cochlear duct, spiral organ of Corti in wall of cochlear duct for hearing; Mesenchyme surrounding vesicle forms cartilaginous otic capsule, ossifies and forms bony labyrinth of inner ear |
| Middle Ear | Tubotympanic recess-pouch 1; Tympanic cavity expands to surround ossicles; Malleus and incus-arch 1; Stapes-arch 2 |
| External Ear | EAM-1st cleft, meatal plug-prolif epithelial cells fill space, disappear 7th month; Tympanic memb-eardrum-ectodermal layer-cleft 1, endodermal layer-pouch 1, mid layer of CT |
| External Ear continued | Auricle-auricular hillocks-mesenchymal sweelings-3 from arch 1, 3 from arch 2, on each side of EAM, shifted from neck to final location via mandible development |
| Anomalies of Ear | Congenital deafness-may be d/t abnormalities of inner/mid ear or both-rubella or genetic; Auricular abnormalities-often associated with serious abnormalities such as trisomy 18 or 13 |
Created by:
lkeith
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