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Embryo Farmer Test 4

Embryology - Dr. Farmer - Test 4

QuestionAnswer
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