gen embryology - kolkata

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Information about gen embryology - kolkata

Published on November 1, 2012

Author: monban


Embryology : Embryology Prof. Manimay Bandyopadhyay 11/1/2012 PowerPoint Presentation: Primordial germ cell Mitosis Dark type A spermatogonia Mitosis Light type A & Dark type A spermatogonia Mitosis Type B spermatogonia Mitosis Primary spermatocyte Meiosis I-reduction division Secondary spermatocyte Meiosis II 4 Spermatid Spermiogenesis 4 Spermatozoa 11/1/2012 PowerPoint Presentation: The process of spermatogenesis including meiosis takes place in semeniferous tubules The sperms are stored , matured and gain motility in epididymis Capacitation takes place in the female genital tract, near isthmus of uterine tubes – 7 hours. It takes 64-74 days. The process starts in puberty. Androgen binding protein maintain high concentration of androgen in the seminiferous tubule. Primary spermatocyte is the largest germ cell. Size of a mature spermatozoon is 50-60 µ. 11/1/2012 PowerPoint Presentation: Spermiogenesis is transformation of spermatid into spermatozoa without further cell division. In it acrosome , neck, middle piece and tail is formed. Most of the cytoplasm is shedded and nucleus condensed. Head – 5 µ m in length- have nucleus with23 chromosome, covered by bilaminar acrosomal cap – derived from golgi apparatus. Middle piece – 5 µ m– have mitochondria. Principal piece – 50 µ m – have axial filaments, cytoplasm & cell membrane End piece - 5 µ m – have axial filaments, fibrous sheath, thin cytoplasm & cell membrane. 11/1/2012 PowerPoint Presentation: Spermatogenesis requires a temperature 2 0 C below the core body temperature. This is achieved in scrotum due to 1) counter current heat exchange mechanism 2) absent subcutaneous fat 3) sebaceous glands Hence intra abdominal testes, wearing tight scrotal support for long, hot baths, varicocele , working in heated environment for long leads to sterility. 11/1/2012 OOG ENESIS: OOG ENESIS 3 rd wk of IU life- germ cells are formed from endodermal cells of the dorsal wall of yolk sac 5 th wk of IU life - start appearing in the gonad & start mitosis 3 rd mth of IU life - primary oocyte 7 th mth of IU life – all are transformed in primary oocyte, remain surrounded by follicular cells – primary ovarian follicle Start prophase of meiosis I, completes it & goes into dictyotene phase because of oocyte maturation inhibitor of follicular cells At birth 7 lac -2 million At puberty 40,000 of which 500 will be ovulated 11/1/2012 PowerPoint Presentation: Primary / pre antral stage Graffin follicle Preovulatory stage Ovulation – secondary oocyte+ cumulus ovaricus + zona pellucida are shredded Polar bodies & corpus luteum degenerate IF FETILISATION TAKES PLACE THEN SECONDARY OOCYTE COMPLETES MEIOSIS II AND THE MATURE OVUM IS FORMED. zona pellucida Glycoprotein Formed in primary follicle stage from oocyte & granulosa cells Persists till morula Disappears at the end of 5 th day after fertilization 11/1/2012 Fertilization : Fertilization Uterine tube is lined by ciliated columner epithelium, cilia most abundant at the fimbriated end. Fertilization takes place in the ampulla within 24 hrs of ovulation. Fertilin acts as a barrier preventing it Zona pellucida prevents sticking / implantation there. It undergoes certain steps. 11/1/2012 PowerPoint Presentation: Approximation Prostaglandin of semen & oxytocin from neurohypophysis of female. Suction action of the uterine contraction Barriers & constrictions reduce the no of active spermatozoa – 300 to 500. Ciliary beats & contraction of musculature of the uterine tube. Contact & Fusion Capacitation- glycoprotein coat & seminal plasma is removed Corona radiata removed by hyaluronidase Zona pelliucida – by trypsin like substance & zona lysin Vitelline membrane – by fusion. 11/1/2012 PowerPoint Presentation: Effects Formation of mature ovum Restoration of diploid number of chromosome determination of chromosomal sex Determination of polarity of embryo 2 cell stage – 30 hrs 4 cell stage – 50 hrs 12 cell stage – 72 hrs 16 cell stage – within 96 hrs after fertilization. 11/1/2012 PowerPoint Presentation: Implantation Takes place on 6 th / 7 th day after fertilization Occurs in the blastocyst stage when due to disappearance of zona pellucida trophoblast sticks 11/1/2012 Types of implantation: Types of implantation Central - Blastocyst within the cavity, just attached to the endometrium- rabbit, cow, dog, monkey Eccentric - Blastocyst remains within a uterine crypt – rat. Interstitial – blastocyst within the depth of endometrium – human. Germinal period : 0-3 wks Embryonal period : 4 th -8 th wk Foetal period : 9 th wk - delivery 11/1/2012 PowerPoint Presentation: Events in first week Cleavage division Transport to uterine cavity Blastocyst Zona pellucida disappears Implantation Day 7 11/1/2012 PowerPoint Presentation: Events in second week Implantation is completed by 12 th day Trophoblast – syncytio & cytotrophoblast Bilaminar germ disc – epiblast + hypoblast Amnion & chorion is formed 11/1/2012 PowerPoint Presentation: Events in THIRd week Germ disc becomes oval from circular Gastrulation Fibroblast growth factor 8 synthesised by primitive streak cells control cell migration by Inhibits E- Cadherin - protein that binds epiblast together Regulate Brachyury -T- expression which control cell specification of mesoderm Primitive streak is initiated & maintained by expression of nodal, a member of Transforming growth factor β Bone morphogenic protein 4 and fibroblast growth factor ventralise mesoderm. HNF3 β maintains primitive node – thus helps in notochord formation & brain vesicle development. Formation of 3 layered germ disc notochord formation starts on 17 th day chorionic villi changes its form 11/1/2012 PowerPoint Presentation: Derivatives of surface ectoderm Epidermis including hair, nails, Sebaceous & sweat glands epithelium of cheek, gum, enamel of teeth, roof of mouth, nasal cavity, para nasal air sinuses, salivary glands, lower part of anal canal, terminal part of urethra ant & post lobes of pituitary ext acoustic meatus, outer lining of tympanic membrane , membranous labyrinth of the ear corneal epithelium, conjunctiva, lacrimal gland nasolacrimal duct, lens, retina Mscls of iris, arrectores pilorum All mscls are mesodermal in origin except the above 2 11/1/2012 PowerPoint Presentation: Neural crest derivative Neural derivative 5 th , 7 th , 8 th , 9 th , 10 th cranial nerve ganglia spinal dorsal nv root ganglia sympathetic chain ganglia, Aurbach’s & Meissner’s plexus Parasympathetic ganglia & plexus of GIT Cellular derivative Schwann cells of all peripheral nerves Satellite cells, Glial cells Adrenal medullary cells, chromaffin cells, calcitonin producing cells Carotid body type I cells, pigment cells Odontoblast Connective tissue derivative Cranio facial skeleton – Frontal, parietal bones etc. Connective tissue of lacrimal, nasal, labial, oral, thyroid glands, thymus & parathyroid glands Choroid & sclera of eye, dentin of teeth, meninges Dermis of face & neck tunica media of outflow tract of heart & great vessels 11/1/2012 PowerPoint Presentation: aaaaaaaaaaaaaaaaaaa 1 st pair of somite start on 20 th day at occipital region On 30 th day 34-35 somites At the end of 5 th wk – 42-44 pairs 4 occipital, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 8-10 coccygeal somites Septum transversum Epicardium Fibrous pericardium central tendon of the diaphragm Kupffer cells of liver Falciform , triangular ligaments Lesser omentum Angiogenic mesenchyme Endocardium Endothelium of blood vessels vessels of choroid plexus Sinusoids of liver & spleen Circulating blood cells & micriglia 11/1/2012 PowerPoint Presentation: Endoderm of Foregut Mucous membrane from pharynx duodenum, Ampulla of Vater Epithelial lining of respiratory system, Auditory tube, tympanic cavity Parenchyma of tonsil, thyroid, parathyroid, thymus, Liver & pancreas Endoderm of Midgut Mucous membrane from duodenum, Ampulla of Vater Transverse colon, jn between right 2/3 rd & left 1/3 rd Meckel’s divertculum when exists Endoderm of Hindgut Mucous membrane up to pectnate line of anal canal Most of the mucous membrane of urinary bladder & urethra Parenchyma of prostate, bulbo urethral gland Epithelium of vagina Primitive sex cells (????) Internal trigone of bladder & upper part of posterior wall of prostatic urethra develops from intermediate mesoderm- by the incorporation of fused part of mesonephric duct 11/1/2012 Full term Placenta : Full term Placenta Diameter 15 – 25 cm Thickness 3cm Weight 500-600 gm Maternal side 15 – 20 cotyledons Fetal side chorionic plate 11/1/2012 PowerPoint Presentation: End of 2 nd month – no chorion laeve End of 3 rd month – ch laeve & decidua parietalis had fused 11/1/2012 Primary villus: Primary villus Central core of cytotrophoblast surrounded by syncytiotrophoblast Secondary villus Syncytiotrophoblast + cytotrophoblast + extra embryonic mesoderm Tertiary villus Syncytiotrophoblast + cytotrophoblast + extra embryonic mesoderm + fetal blood vessels 11/1/2012 PowerPoint Presentation: Uterine artery Uterine vein Ox - 90 Ox - 40 Ox – 20 Umbilical artery Umbilical vein Ox - 40 Placenta Trans placental pressure gradient in mm of Hg 35 7.5 11/1/2012 PowerPoint Presentation: Prenatal circulation 11/1/2012 Shunts in fetal circulation: Shunts in fetal circulation At ductus venosus – directing blood straight to the IVC without losing oxygen for liver At foramen ovale – directing oxygenated blood to left atrium for distribution to the head, neck and brain At ductus arteriosus – to direct venous blood to the placenta by passing the lungs 11/1/2012 Sites where major admixtures of oxygenated and deoxygenated blood takes place in foetal circulation: Sites where major admixtures of oxygenated and deoxygenated blood takes place in foetal circulation Terminal part of IVC Both atria, particularly in right atrium Distal part of the arch of aorta Oxygen saturation in those situations are just enough to maintain nutrition of the foetal tissues . 11/1/2012 PowerPoint Presentation: Post-natal circulation 11/1/2012 Circulatory changes occurring at birth: Circulatory changes occurring at birth Closure of the umbilical arteries Functional closure : few minutes after birth Actual obliteration : 2-3 months Cause of closure : change in oxygen tension Remnant : Distal part – Medial umbilical ligament Proximal part – Superior vesical artery 11/1/2012 PowerPoint Presentation: Closure of the umbilical veins Shortly after closure of the arteries. Indicates entry of the blood for sometime after birth Remnant: Ligamentum teres hepatis So ligature of umbilical cord after waiting for few minutes provides additional 50cc of placental blood to the new born 11/1/2012 PowerPoint Presentation: Closure of the ductus venosus Ligamentum venosum at the posterior aspect of the liver 11/1/2012 PowerPoint Presentation: Closure of the ductus arteriosus Functional closure : Immediately after birth Complete obliteration : 1-3 months Cause of closure : Release of Bradykinin from lung during initial inflation Remnant : Ligamentum arteriosum 11/1/2012 PowerPoint Presentation: 7 th Week 3 rd month 11/1/2012 PowerPoint Presentation: Closure of foramen ovale Functional closure : Starts after birth Actual obliteration : About an year Cause of closure : Septum primum pressing against the septum secondum Remnant : Fossa Ovalis In 20% individuals perfect anatomical closure might never take place. 11/1/2012 Defects in closure of Foramen ovale: Defects in closure of Foramen ovale Variety of Atrial septal defect . Asymptomatic at early part of life except murmur since there is only left to right shunt as the pressure in the left is always higher. When right atrial pressure increases then cyanotic spells can take place. 11/1/2012 PowerPoint Presentation: Umbilical cord Full term length- 50 cm, Breadth – 2 cm, Have false knots in it Contents : 2 umbilical arteries – from ventral division of internal iliac artery carry deoxygenated blood from fetus to chorionic villi Umbilical vein – Initially 2, soon right one disappears Carry oxygenated blood from placenta to the left branch of portal vein at porta hepatis of fetus 3) Wharton’s jelly –primary mesodermal cells of connecting stalk which undergone mucoid degeneration 4) Distal part of the Allantoic Diverticulum 5) Vitello -intestinal duct 6) Communication between extra & intra embryonic celom 11/1/2012 PowerPoint Presentation: Amniotic fluid Contain 2% solids – inorganic salts, urea, proteins, trace of sugar Amniotic cells have microvilli, may be golgi / fibrillar type The volume of fluid increases up to 6 th month of pregnancy, there after it diminishes, at the end of gestation the amount is 1 litre . Fetal urine is added from 4 th month onward as metanephric kidney functions from there From 5 th month onwards fetus swallows it, which is then absorbed in gut, then via blood goes to the maternal blood through placenta If the volume is more than 2 litres , then it is known as HYDRAMNIOS – oesophageal atresia , anencephaly Scanty amniotic fluid – OLIGOHYDRAMNIOS occur in congenital agenesis of kidney 11/1/2012

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