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Embryo Test 1
NWHSU
| Question | Answer |
|---|---|
| When is the pre-embryonic period | 1st-2nd week |
| What are the main things that happen durring the first week | Fertilization, Cleavage, Blastocyst Formation, Implantation |
| Union of Male and female gametes to form a zygote | Fertilization |
| How long are gametes viable for fertilization | Male=24hrs Female=12-24hours post ovulation |
| Functions of Fertilization | 1)Restoration of diploid # (2n) of chromosomes (23 pair) 2)Determination of sex (XX is female XY is Male) 3)Initiation of cleavage |
| Process by which sperms are activated for fertilization | Capacitation |
| Describe capacitation and how long it takes | Takes about 7 hrs. Mechanism involves removal of a protein coat from sperm head. Allows for sperm to penetrate the Corona Radiata |
| Perforation of acrosome wall and release of enzymes to allow sperm to penetrate secondary oocyte barrier | Acrosome reaction |
| How many sperm are involved in fertilization | 200-300 million initially, only 300-500 reach fertilization site |
| Where should fertilization occur for optimal chance of success | The distal 1/3 of the uterine tube |
| How many barriers does the spermatozoon have to penetrate for fertilization to occur and name them | 1)Corona Radiata 2)Zona Pellucida 3)Oocyte Cell Membrane |
| Name give to follicular cell immediately surrounding oocyte that are adherent to oocyte after ovulation | Corona Radiata |
| Glycoprotein coat surrounding oocyte which is penetrated by acrosome reaction enzymes. | Zona Pellucida |
| Describe the Zona reaction | After spermatozoon penetrates zona pellucida and contacts the cell membrane of oocyte, the zona pellucida becomes impermeabel to penetration by additional sperms |
| What does penetration of the Oocyte Cell Membrane cause | 1)Spermatozoon and secondary oocyte fuse 2)Secondary oocyte finishes metaphase II, forms female pronucleus 3)sperm head separates from tail, forms male pronucleus 4)Pronuclei replicate, chromosomes intermingle, 1st cleavage mitotic division occurs |
| A series of mitotic cell divisions. Cells become smaller with each division forming a morula (3 days post-fertilization) | Cleavage |
| What is a morula and when is it formed | A ball of 12-16 blastomers with an inner cell mass and outer cell mass. Formed 3 days post-fertilization |
| During the 1st week a cavity soon forms within the morula. What is this step called? | Blastocyst formation. |
| Describe a Blastocyst and the time frame | A hollow ball of about 58 cells (4-4 1/2 days) Consists of Zona pellucida, Inner cell mass, outer cell mass |
| What is the inner cell mass of the blastocyst called | Embryoblast (forms embryo proper) |
| What is the outer cell mass of the blastocyst called | Trophoblast (forms most of placenta and extraembryonic membrane) |
| Penetration of blastocyst into endometrial lining of uterine wall. | Implantation |
| When and Why does implantation happen | 5 1/2-6 days. Due to proteolytic enzymes from the trophoblast, the blastocyst implants at embryonic pole since this area is more sticky |
| What phase of Meiosis is the Oocyte in during ovulation | Metaphase II. Won't leave Metaphase II unless fertilization is successful |
| What happen during the 2nd week | Formation of the bilaminar embryonic disc |
| Durring the 2nd week what does the trophoblast differentiate into | The Cytotrophoblast and the syncytiotrophoblast |
| Layer of mononucleated mitotic active cells which migrate and lose their cell membranes | Cytotrophoblast |
| A multinucleated mass of protoplasm which penetrates deeper into the endometrium of uterus. | Syncytiotrophoblast |
| Part of Syncytiotrophoblast that tap maternal sinusoids, maternal blood enters lacunae establising uneroplacental circulation and beginnings of placenta | Lacunae of syncytiotrophoblast |
| What does the Embryoblast differentiate into | Epiblast (columnar cells/dorsal surface on adult) and Hypoblast (cuboidal cells/ventral surface on adult) |
| What do the epiblast and hypoblast form together | Bilaminar embryonic disc |
| Describe the Amniotic Cavity | Develops dorsal to epiblast. Roof is called Amnion |
| What is the Amnion formed by | Roof of Amniotic cavity. Inner layer of amnioblasts and outer layer of extraembryonic somatopleuric mesoderm |
| Describe the Yolk Sac/Exocoelomic Cavity | Develops ventral to hypoblast. Has inner lining of extraembryonic endoderm and an outer layer of extraembryonic splanchnopleuric mesoderm |
| Describe the Chorion | Develops most peripherally. It surrounds the chorionic cavity/extraembryonic coelom, has villi and forms most of the placenta |
| What is the chorion made of | inner layer of extraembryonic somatopleuric mesoderm, cytotrophoblast and outer syncytiotrophoblast |
| Non invasive benign tumor that develops if chorion persists after an abortion | Hydatidiform mole |
| A malignant tumor that forms if chorion persista after an abortion | Chorionepithelioma |
| 3rd-8th weeks of development | Embryonic Period |
| What happens in the third week of development | Formation of Trilaminar disc |
| Invaginating areas producing the notochord. Located at the cephalic end of primitive streak | Primitive node and primitive pit |
| a longitudinal mesodermal rod forming the central axis of the embryo | Notochord |
| Area of trilaminar embryonic disc where there is an inward migration of epiblastic cells | Primitive Streak |
| Describe Gastrulation | Epiblast -> embryonic ectoderm and mesoblast -> inraembryonic mesoderm and embryonic endoderm |
| What are the three germ layer that make up the trilaminar disc | Embryonic ectoderm, intraembryonic mesoderm, embryonic endoderm |
| What is cephalocaudal gradient of differentiation | The head of the embryo starts to advance before the tail |
| What happens during the fourth week of development | Establishment of body form (folding of the embryo). |
| What direction does the embryo fold durring the 4th week | Lateral folding (produces cylidrical embryo with intraembryonic coelomic cavity surrounded by lateral and ventral body walls. Causes amniotic cavity to surround.) Cephalocaudal Folding (forms head and tail. Causes amniotic cavity to go around as well) |
| What fuses to form umbilical cord | Vitelline duct and connecting stalk |
| What process is primarily involved during the embryonic period | Morphogenesis (molding of the body and its organs into form and pattern) |
| What is the 9th-38th weeks of development called | Fetal Period |
| How long is a typical pregnancy | 38 weeks post-fertilization or 40 weeks from last menstrual period |
| Characteristics of the Fetal Period of development | Histogenesis, Rapid Growth, Takes on human appearance |
| Maturation of the organs at the histological level | Histogenesis |
| Most critical time period developmentally | Embryonic Period (weeks 3-8), This is when morphogenesis is happening |
| What is a Teratogen | Anything that causes a malformation |
| What does Ectoderm become | Anterior pituitary, hair, nails, lens, enamel, skin, mammary glands ear, epidermis, ganglia and sensory nerve, adrenal medulla, cartilages of branchial arches, CNS, pineal gland, posterior pituitary, retina |
| What does Endoderm become | Epithelium of parathyroid and thyroid gland, auditory tube, tympanic cavity, tonsils, pharynx, bladder, GI tract, liver, pancreas, lungs, bronchi, and trachea |
| What are the different types of Mesoderm | Paraxial mesoderm, Intermediate mesoderm, Lateral plate mesoderm |
| What does the Paraxial mesoderm become | Somites->most SKM, skeleton except skull, CT, dermis |
| What does the Intermediate mesoderm become | Urogenital system (kidneys, ducts, gonads, associated glands) |
| What does the Lateral plate mesoderm become | CT and muscles of viscera, adrenal cortex, spleen, cardiovascular and lymphatic systems, serous membranes (peritoneum, pleura, pericardium) |
| When is the primitive gut formed and what are it's sections | End of 1st month 1)Foregut 2)Midgut 3)Hindgut |
| What are the two parts of the foregut | Cranial part (pharyngeal gut or pharynx) and caudal part |
| When does development of the pharyngeal region take place | 4th-5th week |
| Outpocketings (4 pairs) of endodermal surface of lateral walls of the pharyngeal gut | Pharyngeal Pouches |
| Inpocketings (4 pairs) of the ectodermal surface of the lateral walls of the pharyngeal gut | Pharyngeal Clefts |
| Bars of mesodermal tissue (5 pairs) covered on outside by surface ectoderm and on inside by endoderm of the pharyngeal gut | Pharyngeal (branchial) Arches |
| How many Pharyngeal arches are there | 5 numbered 1-4 and 6 |
| Describe the development of the 1st pharyngeal arch | Maxillary Process (no cartilage)(maxilla & zygomatic bone, hard palate, squamous part of temporal bone) Mandibular Process (Meckel's cartilage derivatives[Malleus and incus, sphenomandibular ligament & ant. ligament of malleus], Mandible[no cartilage]) |
| Describe the development of the 2nd pharyngeal arch | Reichert's cartilage derivatives (Stapes, Styloid process, stylohyoid ligament, lesser horn/cornu and superior half of body of hyoid) |
| Describe the development of the 3rd pharyngeal arch | Cartilage of the arch forms (Greater horn/cornu and inferior half of body of hyoid) |
| Describe the development of the 4th and 6th pharyngeal arches | Laryngeal cartilages |
| Describe the differentiation of paraxial mesoderm | At 20 days 1st somites appear in cephalic region -> Somites appear in craniocaudal sequence at about 3 pairs/day -> At end of 5th week 42-44 pairs have developed |
| How many pairs of somites and how are they classified | 42-44 total pairs -> Occipital (4) Cervical (8) Thoracic (12) Lumbar (5) Sacral (5) Coccygeal (8-10) |
| What do somites differentiate into | Sclerotomes and Dermatomes (dermatomes become myotomes) |
| Where do myoblasts come from | Myotomes which come from dermatomes which come from somites |
| What are myoblasts | Primitive muscle cells |
| Describe the myotomes of the Head | Occipital myotomes (4 pair); innervated by hypoglossal (XII) n. Form tongue muscles |
| Myotomes of the neck and trunk | Cervical, thoracic, lumbar, sacrococcygeal |
| What is an Epimere | name given to dorsal parts, innervated by posterior primary divisions, forms extensor muscles of vertebral column |
| What is a Hypomere | Name given to ventral parts, innervated by anterior primary divisions, forms lateral and ventral flexor muscles of vertebral column |
| Describe the Cervical Myotomes | Innervated by cervical spinal nn. Epimere forms(deep intrinsic back muscles) Hypomere forms(prevertebral neck mm, scalene mm, infrahyoid mm, geniohyoid mm, sensory part of trapezius and SCM mm.) |
| Describe the Thoracic Myotomes | Innervated by thoracic spinal nn. Epimere(deep intrinsic back muscles) Hypomere(intercostal mm, transverse thoracic m, oblique mm of the abdomen, transversus abdominis and rectus abdominis) |
| Describe the Lumbar myotomes | Innervated by lumbar spinal nn. Epimere(deep intrinsic back muscles) Hypomere( quadratus lumborum m) |
| Describe the sacrococcygeal myotomes | Innervated by sacrococcygeal spinal nn. 5 sacral and 3-5 coccygeal pairs remain post-development. Epimere(ligaments) Hypomere(muscles of pelvic diaphragm, SKM of the anus and sex organs) |
| Where does do limb myoblasts come from | They are hypomeres of the adjacent trunk myotomes. Myoblasts migrate into limb buds from myotomes to surround developing bones (7th week) |
| What are Preotic Myotomes | Located in head just anterior to developing ear. Each is innervated by its own CN (III, IV, or VI). Believed to from head mesoderm and form the extrinsic eye muscles |
| What are Brachiomeric muscles | Muscles which develop from pharyngeal arches, in the 4th-5th week, innervated by same nerve as the pharyngeal nerve where it began |
| Muscle and Nerve of the 1st Pharyngeal arch | Muscles (4 primary muscles of mastication, mylohyoid, tensor tympani, tensor veli palatini, anterior belly of degastric) Nerve (Mandibular branch of trigeminal, V3) |
| Muscle and Nerve of the 2nd Pharyngeal arch | Muscles (muscles of facial expression, posterior belly of digastric, stapedius, stylohyoid) Nerve (Facial, VII) |
| Muscle and Nerve of the 3rd Pharyngeal arch | Muscles (stylopharyngeus, possibly upper pharyngeal constrictors) Nerve (glossopharyngeal IX) |
| Muscle and Nerve of the 4th Pharyngeal arch | Muscles (constrictors of the pharynx, cricothyroid, levator veli palatini) Nerve (Vagus X) |
| Muscle and Nerve of the 6th Pharyngeal arch | Muscles (all muscles of larynx except cricothyroid and part of transverse arytenoid) Nerve (Vagus X) |
| Muscle and Nerve of the Postbranchial region | Muscles (trapezius and SCM [in part]) Nerve (Spinal accessory, XI and ventral rami of C2-4) |
| Where does smooth muscle come from | Largely from splanchnic (visceral) mesoderm (from lateral plate) surrounding the GI tract and its derivatives/ Vessels in limbs, head and body wall develop SmM coats from local mesenchyme |
| Where does Cardiac muscle come from | Develops from splanchnic mesoderm that surrounds the primitive heart tubes |
| Where does Muscle fascia come from | Derived from remaining mesenchyme which is left over after muscle development |
| When do Extraembryonic blood vessels start form and from what | In the 3rd week from mesenchymal cells (angioblasts) |
| Describe the process of forming extraembryonic blood vessels | Angioblasts from the Chorion, connecting stalk and wall of yolk sac form the angiogenic cell clusters (blood islands) -> Lumen forms -> blood vessels form -> blood vessels penetrate embryo proper |
| What are angiogenic cell clusters | Isolated masses and cords of cells |
| How is the lumen of extraembryonic blood vessels formed | By confluence of intercellular clefts. Central cells form primitive blood cells and peripheral cells form endothelial lining |
| where do the extraembryonic blood vessels come from | Vitelline vessels come from blood islands of yolk sac. Umbilical vessels come from blood islands of allantois in connecting stalk (connected with chorionic vessels) |
| When do Intraemryonic blood vessels form | Late 3rd week |
| Describe the steps to get the endocardial heart tubes | Blood islands in splanchnic mesoderm (lateral sides of embryo) -> horseshoe-shaped plexus of blood vessels (lateral and anterior) -> Endocardial Heart Tubes |
| Describe the steps to get the Dorsal Aortae | Blood Islands in splanchnic mesoderm (near midline of embryo) -> longitudinal vessels -> dorsal Aortae |
| When is the primitive CV system established | End of 3rd week |
| Vitelline vessels come from? | Yolk sac |
| Umbilical vessels come from | Chorion |
| Dorsal Aortae comes from | body of embry proper |
| What is blood formed from | Mesenchymal cells |
| Where is blood formed during the late 3rd week-2nd month | Yold sac and Allantois |
| Where is blood formed during the 5th week-2nd month | Body mesenchyme and blood vessels |
| Where is blood formed during the 6th week-birth and is most active area until mid fetal life | Live |
| Where is blood formed during the 4th-8th month | Spleen |
| Where is blood formed during the 4th-5th month and then through the rest of your life | Red Bone Marrow |
| Formation and position of endocardial heart tube 1st step | Cardiogenic plate at 19 days is initially anterior to prochordal plate and ventral to developing pericardial cavity. Due to longitudinal expansion of brain a 180 degree rotation of prochordal plate and cardiogenic plate around transverse axis happens. |
| Formation and position of endocardial heart tube 2nd step | Cardiogenic plate is now caudal to prochordal plate and dorsal to pericardial cavity. Cardiogenic plate contains developing heart tubes and pericardial cavity |
| Formation and position of endocardial heart tube 3rd step | As cephalocaudal flexion takes place, the embryo simultaneously undergoes lateral folding causing the 2seperate endo cardial hear tubes to fuse together ventrally in the midline of the embryo. This formes the single endocardial heart tube at 21 days |
| Formation and position of endocardial heart tube 4th step | Dorsal mesocardium formed as heart tube expands and grows into pericardial cavity. the dorsal mesocardium temporarily attaches heart tube to dorsal part of pericardial cavity (soon it disappears) |
| Formation and position of endocardial heart tube 5th step | Formation of walls surrounding endocardial heart tube. Splanchnic mesenchyme (surrounding endocardial heart tube) -> myoepicardial mantle -> myocardium and epicardium. endocardial heart tube -> edocardium |
| When does the heart tube begin to beat | 22-24 days (7-13 somites) |
| How is the inrapericardial portion of the heart loop formed | From the bulboventricular portion dividing into bulbus cordis and the ventricle |
| Due to elongation of the heart tube inside the pericardial sac what must happen | The heart tube must bend inside the sac forming the bulboventricular sulcus on outside of tube and bulboventricular fold on inside. Causes the bulbus codis to move to right side of pericardial cavity and ventricle to left |
| Where does the common atrium come from and what happens to it | It starts out as the paired atria fuse. It ends up incorporated into the pericardial cavity |
| Forms at the atrioventricular junction (connects left side of common atrium with ventricle ) | Atrioventricular Canal |
| At junction of bulbus cordis and ventricle | Primary interventricular foramen |
| Describe ventricular formation | Primitive ventricle becomes the trabeculated part of left definitive ventricle. Proximal 1/3 of bulbus cordis becomes trabeculated part of right definitive ventricle |
| Describe Atrial Formation | Truncus arteriosus of bulbus cordis lies medially between right and left pouches of common atrium |
| Describe Sinus Venosus at 24 days | Consists of L. and R. Sinus horns and transvers portion. Each horn receives venous blood from 3 veins: vitelline, umbilical and common cardinal |
| Shifts opening of sinus venosus to right side of common atrium | Sinuatrial fold |
| Derivative of Sinus Venosus | Left common cardinal v. -> Oblique v. of left atrium; Left horn of sinus venosus ->coronary sinus; Transverse part of sinus venosus -> coronary sinus; right horn of sinus venosus -> incorporated into right atrium as sinus venarum |
| Derivative of Venous valves of sinuatrial orifice | Superior fusion of L. & R. venous valves -> septum spurium; Rest of L. venous valve later fuses with septum secundum; Superior part of R. venous valve -> forms crista terminalis; Inferior part of R. venous valve -> valve of IVC & valve of coronary sinus |
| Formation of Interatrial septa steps | 1)Septum Primum (septum I) 2) Septum Secundum (septum II) 3) fusion of Septum primum and secundum 4) derivation of definitive atrial components |
| Components of Septum Primum | Comes from growth of atrial pouches in roof of common atrium. Inf. edge grows downs toward endocardial cushion to split atria. Ostium primum-opening between atria. Ostium secundum-forms when sup. portion of septum primum perforates |
| Components of Septum Secundum | Forms between septum primum and septum spurium. Iferior edge grows down to meet endocardial cushion, however part reamins open as foramen ovale |
| What is probe patency of foramen ovale | Incomplete fusion of Septums |
| What is patent foramen ovale | Foramen ovale remains open |
| Where does the smooth-walled portion of R. atrium come from | From R. sinus horn |
| Where does the smooth-walled portion of L. atrium come from | From single primitive pulmonary vein |
| Where does the Auricular portion of R. atrium | From original embryonic R. artium before incorporation of R. sinus horn |
| Where does the Auricular portion of L. atrium | From original embyonic L. atrium before incorporation of primitive pulmonary vein |
| How are the atrioventricular canals formed | Superior and inferior endocardial cushions grow and fuse across the single atrioventricular canal forming R. and L. atrioventricular canals. Lateral AV cushions also appear on R & L sides |
| How is the Muscular portion of the interventricular septum formed | Expansive growth of primitive R & L ventricles causes medial walls to fuse, thus the primitive IV septum becomes the definitive muscular IV septum. |
| How is the membranous portion of the interventricular septum formed | Fusion of Left conal ridge, Right conal ridge, Posterior endocardial cushion |
| Formation of the Aorticopulmonary Septum | Bulbus Cordis is split into Truncus arteriosus portion, Conus cordis portion, and Trabeculated portion |
| Describe the truncus arteriosus portion of the bulbus cordis | R & L truncus swellings, these grow toward each other tweisting as they grow, then fuse forming aorticopulmonary septum (forms ascending aorta and pulmonary trunk) |
| Describe the Conus Cordis portion of the bulbus cordis | Forms R & L conal swellings; conal swellings participate in the development of membranous part of IV septum |
| Describe the Trabeculated portion of the bulbus cordis | Forms trabeculated part of R ventricle |
| What happens with surface ectoderm durring the development of the inner ear | At region of hindbrain begins to thicken during 3rd week to form otic placode. The placode soon invaginates to form otic pit which subsequently loses contact with surface to become the otic vesicle |
| What happens to neural crest cell adjacent to the otic vesicles durring inner ear development | They are joined by some cells of otic vesicle to form the auditory ganglion. this ganglion later splits into spiral and vestibular ganglia |
| What are the 3 subdivisions of the otc vesicle | Endolymphatic duct, utricle (semicircular canals), saccule (cochlear duct) All three together make up the membranous labyrinth |
| Mesenchyme surrounding the membranous labyrinth condenses to become the otic capsule which in turn will form the carilage precursor of what | Osseous labyrinth |
| Describe the formation of the auditory tube | Dilated distal end of 1st pharyngeal pouch grows laterally as tubotympanic recess. Comes to lie opposite 1st pharyngeal ectodermal cleft. Distal tubotympanic recess becomes primitive tympanic cavity & narrow proximal part of pouch becomes auditory canal |
| Where do the auditory ossicles come from | The area just above the typanic cavity shows several mesenchymal condensation that become the ossicles |
| What arch do the malleus, incus and stapes come from | malleus and incus from arch 1 and stapes from arch 2 |
| How does the Auricle of the external ear develop | 1st pharyngeal cleft deepens and a series of six hillocks of the 1st and 2nd pharyngeal arches appear during 6th week. Cleft becomes external auditory meatus and hillocks by growth and fusion give rise to auricle |
| Temporarily fills base of primitive external auditory meatus from the 3rd to 7th months | Meatal Plug |
| How is the tympanic membrane formed | Ectodermal epithelium from the floor of the 1st pharyngeal cleft. Endodermal epithelium from the expanded 1st pharyngeal pouch. Mesoderm intervenes between ectodermal and endodermal layers |
| Anomalies in Ear formation | Congenital deafness, Atresia of external acoustic meatus, Auricular anomalies |
| Primordia of External auditory meatus | 1st pharyngeal cleft ectoderm |
| Primordia of auricle | ectoderm and mesoderm of 1st and 2nd pharyngeal arches and hillocks |
| Primordia of tympanic membrane | 1st pharyngeal cleft ectoderm, mesoderm, 1st pharyngeal pouch endoderm |
| Primordia of Tympanic cavity and auditory tube | 1st pharyngeal pouch endoderm |
| Primordia of Ossicles | mesoderm |
| Primordia of inner ear | surface ectoderm (membranous labyrinth and auditory ganglion) and neural ectoderm/crest (auditory ganglion) |
| Describe formation of optic cup | Optic grooves appear on medial wall of forebrain. Optic vesicle contacts ectoderm inducing lens placode to form. Optic vesicle attached to diencephalon by optic stalk. Vesicle indents forming two-layered optic cup with the choroid fissure on inf. surface |
| Describe the formation of optic lens | Lens placode invaginate forming a lens pit, then loses its surface contact forming the lens vesicle. Lens vesicle eventually forms the lens of the eye |
| Differentiation of the inner wall of optic cup | Differentiates into neural retina, with its three orders of neurons (primary rods and cones, secondary bipolar cells, tertiary ganglion cells), inner layer of ciliary body and inner layer of iris. |
| Differentiation of outer wall of optic cup | Begins to show a deposition of pigment(pigment layer of retina, ciliary body and iris) at the time of closure of the choroid fissure. Also fors the dilator and sphincter pupillae mm of the iris. |
| Differentiation of the cavity of optic cup | Separates the two layer of the retina. The cavity termed the intraretinal cleft is present only as a potential space after the 10th week |
| Describe the blood supply of the eye with regards to the hyaloid artery | A branch of the ophthalmic artery (hyaloid artery) enters the open choroid fissure to supply the vitreous body and lens. The distal part regresses leaving the hyaloid canal of the vitreous body. Proximal part forms the central artery of the retina |
| What are the ciliary arteries that arise from the ophthalmic artery | Short posterior, long posterior and anterior ciliary arteries |
| Where do the short and long ciliary arteries run and what do they supply | Both run in choroid layer. Short posterior supplies pigment layer of retina. Long posterior supplies iris and ciliary body |
| Where does the anterior ciliary artery run and what does it supply | runs on rectus muscles and their tendons. Supplies iris and ciliary body |
| Mesenchyme surrounding the optic cup condenses to form? | uveal layer of iris, vitreous body, bony orbit, ciliary mm, choroid layer, extrinsic eye mm, suspensory ligaments, sclera, blood vessels |
| What happens when there is cavitation of mesoderm between surface ectoderm and the lens of the eye | Forms the anterior chamber, leaving a thin iridopupillary membrane anterior to the lens |
| How are the eyelids and conjunctival sac formed | Suface ectoderm folds over the cornea from above and below. eyelids fuse from 10th week-7-8month. Invagination of surface ectoderm forming glands and hair follicles happens. Condensation of mesenchyme to form CT and muscle of eyelid happens |
| What is the Congenital anomaly of the eye causing total agenesis | anophthalmia |
| What is the Congenital anomaly of the eye causing a small eye | Microphthalmia |
| What is the Congenital anomaly of the eye causing one median eye | Cyclopia |
| What is the Congenital anomaly of the eye causing failure of closure of choroid fissure; usually only involves the iris, but may include the retina and optic nerve | Coloboma of iris |
| What is the Congenital anomaly of the eye causing the optic cups to fuse together | Synophthalmia |
| Derivation of Neural ectoderm in eye | pigment retina, neural retina, ciliary epithelium, epithelium of iris, sphincter and dilator pupillae mm, neural part of optic nerve |
| Derivation of Surface ectoderm in eye | lens, eyelid epithelium, conjunctival epithelium, corneal epithelium, glandular epithelium |
| Derivation of mesoderm in eye | Sclera, choroid, blood vessels, extrinsic eye mm, ciliary m, blood vessels, bony orbit, vitreous body, stroma of iris, suspensory ligaments, substantia propria of cornea, Descemet's membrane of cornea, endothelium of cornea |
Created by:
bmlanger
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