DOCSLIB.ORG

Types of Kidney and Evolution of Urinogenital Ducts in Vertebrates

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Types of Kidney and Evolution of Urinogenital Ducts in Vertebrates Types of kidney and evolution of urinogenital ducts in vertebrates Excretion is a major physiological process found in all the animal groups by which nitrogenous wastes and toxins are removed from the body. Kidney is the major excretory organ of the vertebrates. Before going to discuss about the different types of kidney found across the vertebrate groups, we should have a look on the evolution of excretory system among different animal groups as discussed in the chart below: Animal groups Main excretory structures Protozoans Plasmalemma or general body surface Porifera and Cnidaria Plasma membrane of each cell Platyhelminthes (Planaria, tapeworm etc.) Protonephridia or flame cells Nemathelminthes (Nereis, earthworm, leech Renette cells (H-shaped) etc.) Annelids Nephridia Arthropods Insects, centipedes, and millipedes Malpighian tubules Crustaceans (e.g. Prawn) Antennary or green glands Scorpions and spiders Coxal glands Molluscs Keber’s Organ and the organ of Bojanus Echinoderms No specialized excretory organ Hemichordates Proboscis gland Urochordates Neural gland Cephalochordates Solenocytes Vertebrates One pair of kidneys Development of kidney in the vertebrates: The embryonic mesoderm differentiates on each side of the body into a segmented dorsal epimere, a small mesomere in an intermediate position and an unsegmented ventrolateral hypomere. Kidney tubules arise from the mesomere. The meomere is as long as the coelom. Gradually it pinches off from the overlying epimere. Anteriorly it remains relatively thin and becomes segmented into units called nephrotomes. Posteriorly, it does not become segmented and is called the nephrogenic cord. Nephrotomes and nephrogenic cord merge into one another at a level that varies among different animal groups. Figure 1: Developmental origin of kidney in the vertebrates Among the vertebrates, the excretory system is composed of kidneys and urinary tubules. In vertebrates, there is a pair of kidneys situated dorsal to the abdominal cavity one on either side of the vertebral column and held in position by peritoneum. Each kidney is made up of a large number of uriniferous tubules known as nephrons. From the point of origin and evolution, the kidneys are classified as: archinephros, pronephros, mesonephros, and metanephros. Archinephros: It is believed that kidneys in all modern vertebrates evolved from a hypothetical kidney known as Archinephros or Holonephros, which is extended from anterior to the posterior end of the body, with segmentally arranged glomeruli and nephrostomes. Each tubule opens separately into the coelom by a peritoneal funnel and nephrostome. Archinephros was found in primitive vertebrate probably extended the entire length of the body cavity & had external glomeruli that drained the coelomic fluid. Each segment of the body contained one pair of Uriniferous tubules with peritoneal funnels. Malphigian bodies remained hanging in the coelom collecting the waste matter from it and pouring in the common archinephric duct. The archinephric duct eventually opens into the cloaca. Archinephric kidney is present in the larval myxine and some apodan amphibians. In the embryos of all vertebrates, archinephros appear as a transitory structure from which pronephros has evolved. In present day vertebrates, uriniferous tubules appear in two or three stages of succession. These stages are pronephros, mesonephros, and metanephros. These stages have evolved from the original archinephros. Figure 2: Structure of Archinephros Pronephros: Pronephros develop in the anterior most part of the nephrotome. 1-13 tubules in each, one pair to each segment. Near each tubule, a glomerulous without any Bowman’s capsule is present. This is known as external glomeruli. When Bowman’s capsule is present, it is known as internal glomeruli. The uriniferous tubules of each pronephros open into a common duct, known as pronephric duct. It runs backward to open into the embryonic cloaca. A pair of pronephros is found in all vertebrate embryos but becomes functional kidney only in some adult cyclostomes and embryos of all anamniotes. Pronephros, when functions as adult kidney, it is known as the Head Kidney found in Myxine and some teleost. Figure 3: Nephros and development of various ducts 1. Pronephros, 2. Mesonephros, 3. Metanephros forming, 4. Metanephros Mesonephros: Mesonephros develops from the nephrotome behind the pronephros and the pronephros later degenarates. Each mesonephric uriniferous tubule with a funnel and Malpighian body, joins the existing pronephric duct. This duct is now known as mesonephric duct or Wolffian duct. Later, the segmental mesonephric tubules undergo budding and their segmental arrangement is lost, and they may have no peritoneal funnel. As the mesonephros in an anamniote forms from the middle part of the nephrotome and as it does not extend through the length of the coelom, this adult anamniote mesonephros is called the Opisthonephros. Mesonephros are the functional kidneys of adult cyclostomes, fishes, and amphibians. They also form the kidney of amniote embryos in which they degenerate in the adult. Figure 4: Mesonephric tubules. Metanephros: It is the functional kidney of adult amniotes. It is formed from the posterior part of nephrotome behind the mesonephros. Metanephros has a double origin. A tubular outgrowth arises from the mesonephric duct near the cloaca. It reaches the nephrotome where it branches to form connecting tubule and calyces. The metanephric kidney begins as a small outgrowth from the more posterior end of the mesonephric duct. This is initially called a metanephric bud. Later, as the nephric tissue develops around this new duct a new kidney structure forms. The proximal part of the tubular outgrowth becomes the ureter or metanephric duct. The nephrotome behind the mesonephros gives rise to metanephric uriniferous tubules of which there are thousands with no segmental arrangements. The tubule becomes long and much coiled and have developed Malpighian body or renal corpuscles without peritoneal funnel. Thus, all .
Load more

Recommended publications
  • Te2, Part Iii
    TERMINOLOGIA EMBRYOLOGICA Second Edition International Embryological Terminology FIPAT The Federative International Programme for Anatomical Terminology A programme of the International Federation of Associations of Anatomists (IFAA) TE2, PART III Contents Caput V: Organogenesis Chapter 5: Organogenesis (continued) Systema respiratorium Respiratory system Systema urinarium Urinary system Systemata genitalia Genital systems Coeloma Coelom Glandulae endocrinae Endocrine glands Systema cardiovasculare Cardiovascular system Systema lymphoideum Lymphoid system Bibliographic Reference Citation: FIPAT. Terminologia Embryologica. 2nd ed. FIPAT.library.dal.ca. Federative International Programme for Anatomical Terminology, February 2017 Published pending approval by the General Assembly at the next Congress of IFAA (2019) Creative Commons License: The publication of Terminologia Embryologica is under a Creative Commons Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0) license The individual terms in this terminology are within the public domain. Statements about terms being part of this international standard terminology should use the above bibliographic reference to cite this terminology. The unaltered PDF files of this terminology may be freely copied and distributed by users. IFAA member societies are authorized to publish translations of this terminology. Authors of other works that might be considered derivative should write to the Chair of FIPAT for permission to publish a derivative work. Caput V: ORGANOGENESIS Chapter 5: ORGANOGENESIS
    [Show full text]
  • Development of the Urogenital System of the Dog
    DEVELOPMENT OF THE UROGENITAL SYSTEM OF THE DOG MAJID AHMED AL-RADHAWI LICENCE, Higher Teachers' Training College, Baghdad, Iraq, 1954 A. THESIS submitted in partial fulfillment of the requirements for the degree MASTER OF SCIENCE Department of Zoology KANSAS STATE COLLEGE OF AGRICULTURE AND APPLIED SCIENCE 1958 LD C-2- TABLE OF CONTENTS INTRODUCTION AND HEVIEW OF LITERATURE 1 MATERIALS AND METHODS 3 OBSERVATIONS 5 Group I, Embryos from 8-16 Somites 5 Group II, Embryos from 17-26 Somites 10 Group III, Embryos from 27-29 Somites 12 Group 17, Embryos from 34-41 Somites 15 Group V , Embryos from 41-53 Somites 18 Subgroup A, Embryos from 41-<7 Somites 18 Subgroup B, Embryos from 4-7-53 Somites 20 Group VI, Embryos Showing Indifferent Gonad 22 Group VII, Embryos with Differentiatle Gonad 24 Subgroup A, Embryos with Seoondarily Divertioulated Pelvis ... 25 Subgroup B, Embryos with the Anlagen of the Uriniferous Tubules . 26 Subgroup C, Embryos with Advanced Gonad 27 DISCUSSION AND GENERAL CONSIDERATION 27 Formation of the Kidney .... 27 The Pronephros 31 The Mesonephros 35 The Metanephros 38 The Ureter 39 The Urogenital Sinus 4.0 The Mullerian Duot 40 The Gonad 41 1 iii TABLE OF CONTENTS The Genital Ridge Stage 41 The Indifferent Stage , 41 The Determining Stage, The Testes . 42 The Ovary 42 SUMMARI , 42 ACKNOWLEDGMENTS 46 LITERATURE CITED 47 APJENDEC 51 j INTRODUCTION AND REVIEW OF LITERATURE Nephrogenesis has been adequately described in only a few mammals, Buchanan and Fraser (1918), Fraser (1920), and MoCrady (1938) studied nephrogenesis in marsupials. Keibel (1903) reported on studies on Echidna Van der Strioht (1913) on the batj Torrey (1943) on the rat; and Bonnet (1888) and Davles and Davies (1950) on the sheep.
    [Show full text]
  • ROBO2 Restricts the Nephrogenic Field and Regulates Wolffian Duct–Nephrogenic Cord Separation
    Developmental Biology 404 (2015) 88–102 Contents lists available at ScienceDirect Developmental Biology journal homepage: www.elsevier.com/locate/developmentalbiology ROBO2 restricts the nephrogenic field and regulates Wolffian duct–nephrogenic cord separation Elanor N. Wainwright 1, Dagmar Wilhelm 2, Alexander N. Combes 3, Melissa H. Little 4, Peter Koopman n Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia article info abstract Article history: ROBO2 plays a key role in regulating ureteric bud (UB) formation in the embryo, with mutations in Received 7 April 2015 humans and mice leading to supernumerary kidneys. Previous studies have established that the number Received in revised form and position of UB outgrowths is determined by the domain of metanephric mesenchymal Gdnf ex- 28 May 2015 pression, which is expanded anteriorly in Robo2 mouse mutants. To clarify how this phenotype arises, we Accepted 30 May 2015 used high-resolution 3D imaging to reveal an increase in the number of nephrogenic cord cells, leading Available online 23 June 2015 to extension of the metanephric mesenchyme field in Robo2-null mouse embryos. Ex vivo experiments Keywords: suggested a dependence of this effect on proliferative signals from the Wolffian duct. Loss of Robo2 Kidney resulted in a failure of the normal separation of the mesenchyme from the Wolffian duct/ureteric epi- Wolffian duct thelium, suggesting that aberrant juxtaposition of these two compartments in Robo2-null mice exposes Ureteric bud the mesenchyme to abnormally high levels of proliferative stimuli. Our data suggest a new model in Nephrogenic cord Mouse which SLIT-ROBO signalling acts not by attenuating Gdnf expression or activity, but instead by limiting epithelial/mesenchymal interactions in the nascent metanephros and restricting the extent of the ne- phrogenic field.
    [Show full text]
  • Urinary System Intermediate Mesoderm
    Urinary System Intermediate mesoderm lateral mesoderm: somite ectoderm neural NOTE: Intermediate mesoderm splanchnic groove somatic is situated between somites and lateral mesoderm (somatic and splanchnic mesoderm bordering the coelom). All mesoderm is derived from the primary mesen- intermediate mesoderm endoderm chyme that migrated through the notochord coelom (becomes urogenital ridge) primitive streak. Intermediate mesoderm (plus adjacent mesothelium lining the coelom) forms a urogenital ridge, which consists of a laterally-positioned nephrogenic cord (that forms kidneys & ureter) and a medially-positioned gonadal ridge (for ovary/testis & female/male genital tract formation). Thus urinary & genital systems have a common embryonic origin; also, they share common ducts. NOTE: Urine production essentially requires an increased capillary surface area (glomeruli), epithelial tubules to collect plasma filtrate and extract desirable constituents, and a duct system to convey urine away from the body. Kidneys Bilateraly, three kid- mesonephric duct neys develop from the neph- metanephros pronephros rogenic cord. They develop mesonephric tubules chronologically in cranial- mesonephros caudal sequence, and are designated pro—, meso—, Nephrogenic Cord (left) and meta—, respectively. cloaca The pronephros and mesonephros develop similarly: the nephrogenic cord undergoes seg- mentation, segments become tubules, tubules drain into a duct & eventually tubules disintegrate. spinal ganglion 1] Pronephros—consists of (7-8) primitive tubules and a pronephric duct that grows caudally and terminates in the cloaca. The tubules soon degenerate, but the pronephric duct persists as the neural tube mesonephric duct. (The pronephros is not functional, somite except in sheep.) notochord mesonephric NOTE tubule The mesonephros is the functional kidney for fish and am- aorta phibians. The metanephros is the functional kidney body of reptiles, birds, & mammals.
    [Show full text]
  • Embryology of the Kidney Rizaldy Paz Scott | Yoshiro Maezawa | Jordan Kreidberg | Susan E
    1 Embryology of the Kidney Rizaldy Paz Scott | Yoshiro Maezawa | Jordan Kreidberg | Susan E. Quaggin CHAPTER OUTLINE MAMMALIAN KIDNEY DEVELOPMENT, 2 MOLECULAR GENETICS OF MODEL SYSTEMS TO STUDY KIDNEY NEPHROGENESIS, 22 DEVELOPMENT, 8 GENETIC ANALYSIS OF MAMMALIAN KIDNEY DEVELOPMENT, 15 KEY POINTS • The development of the kidney relies on reciprocal signaling and inductive interactions between neighboring cells. • Epithelial cells that comprise the tubular structures of the kidney are derived from two distinct cell lineages: the ureteric epithelia lineage that branches and gives rise to collecting ducts and the nephrogenic mesenchyme lineage that undergoes mesenchyme to epithelial transition to form connecting tubules, distal tubules, the loop of Henle, proximal tubules, parietal epithelial cells, and podocytes. • Nephrogenesis and nephron endowment requires an epigenetically regulated balance between nephron progenitor self-renewal and epithelial differentiation. • The timing of incorporation of nephron progenitor cells into nascent nephrons predicts their positional identity within the highly patterned mature nephron. • Stromal cells and their derivatives coregulate ureteric branching morphogenesis, nephrogenesis, and vascular development. • Endothelial cells track the development of the ureteric epithelia and establish the renal vasculature through a combination of vasculogenic and angiogenic processes. • Collecting duct epithelia have an inherent plasticity enabling them to switch between principal and intercalated cell identities. MAMMALIAN KIDNEY DEVELOPMENT The filtration function of the kidneys is accomplished by basic units called nephrons (Fig. 1.1). Humans on average have 1 million nephrons per adult kidney but the range of ANATOMIC OVERVIEW OF THE 4 MAMMALIAN KIDNEY total nephrons is highly variable across human populations. Each mouse kidney may contain up to 12,000–16,000 nephrons The kidney is a sophisticated, highly vascularized organ that depending on the strain.5 This wide range in nephron number plays a central role in overall body homeostasis.
    [Show full text]
  • Renal Development
    RENAL DEVELOPMENT Jon Barasch M.D., Ph.D. Telephone: 305-1890 e-mail: [email protected] SUGGESTED READING: Larsen, 3rd edition, pp 265 (first three paragraphs) - 266, 268-276 and figure 10-10 LEARNING OBJECTIVES: You should be able to: 1. Describe the three kidneys that are produced during development and know what happens to each one. 2. Explain what is meant by ‘reciprocal induction’ and why it poses problems in interpreting experiments in developing kidney. 3. Describe the stages of nephron formation from the renal vesicle. 4. Discuss the regulators of mesenchymal to epithelial transition in the intermediate mesoderm and metanephric mesenchyme and name three molecules mediating conversion. 5. Describe branching morphogenesis and name the three patterns in the developing metanephros. 6. Discuss three key important ligands and their receptors. 7. Discuss the classification of congenital renal abnormalities that are associated with urological abnormalities and the possible underlying mechanisms for their association. SUMMARY: The urogenital system derives from mesenchymal cells by a process of conversion to epithelia. The development of the kidney relies on three mechanisms of epithelial morphogenesis. 1. Some newborn epithelia migrate extensively (Wolffian duct), 2. some undergo branching morphogenesis (ureteric bud) and 3. some produce highly segmented tubules (nephrons). GLOSSARY: Angiotensin II: your favorite vasoconstrictor and regulator of proximal tubule reclamation of NaCl and water by receptor type 1. Receptor type-2 modulates cell growth and seems to play a role in congenital abnormalities. Arcade: a tubule of ureteric bud that induces a few nephrons simultaneously. The nephrons join to a common drainage called a connecting tubule that feeds into the ureteric’s collecting duct.
    [Show full text]
  • Embryology of Urogenital System
    Embryology Of urogenital system 2018-2019 DR. Hassna B. Jawad Objective learning : At the end of the lecture you should be able to : Know Origin of urogenital system from the urogenital ridge Enlist the Structures derived from urogenital ridge Know the 3 sets of successive kidney system Recognize the pronephron ,its time of appearance ,location and function Recognize the Mesonephron, its time of appearance ,location and function Recognize the metanephron ,its source, time of appearance ,location and function Describe the development of ureter from ureteric bud Describe the development of collecting duct Describe Positional changing of kidney and its blood supply Describe the development of urinary bladder from urogenital sinus Describe the development of urethra from urogenital sinus Origin Of Urogenital sinus Two embryonic structures play an important part in the development of urogenital system: 1-Intermediate mesoderm 2-Cloaca The urogenital system develops from the intermediate mesenchyme (mesoderm) – Urogenital Ridge. The part of the urogenital ridge giving rise to the urinary system is the nephrogenic cord and the part giving rise to the genital system is the gonadal ridge. 1 Embryology Of urogenital system 2018-2019 DR. Hassna B. Jawad Development of urinary system: 3 sets of successive kidneys : Pronephron: These bilateral structures appear early in the fourth week. Segmented division of intermediate mesoderm form a few cell clusters and 5-7 pairs pronephric tubules in the cervical region. One end of the tubules opened at coelomic cavity and the other end opened in to pronephric duct 2 Embryology Of urogenital system 2018-2019 DR. Hassna B. Jawad Function : The tubules transmits the waste product from coelomic cavity to the pronephric duct that runs caudally and open into the Cloaca .
    [Show full text]
  • Kidney Development and Function in the Fetus
    Kidney Development, - and Function in the Fetus Bob Caruthers, CST, PhD The kidneys produce urine, a blood filtrate, and regulate uri- can be seen in the fourth week. The pronephros is complete1 nary volume and composition. These regulatory activities regred by the start of the fifth week. The pronephros form involve balancing water and solute transport, conserving and regresses in a cranial-to-caudal sequence. No pronephric nutrients, eliminating waste products, and regulating acid and glomeruli (cluster of capillaries) have been observed, and no bases. The primary purpose of kidney function is to maintain a vesicles are associated with the pronephric duct. The stable environment in which cellular and tissue metabolic pronephros is, therefore, not active in urine producti0n.Y activity can proceed at an optimal level. The kidneys secrete the hormone renin, erythropoietin and 1.25-dihydroxy vita- MPSONEPHROS min D. Renin helps regulate blood pressure. Erythropoietin The mesonephros originates in the nephrogenic cord that is helps regulate erythrocyte production. 1,25-dihydroxy vitamin part of the intermediate mesoderm. Early mesonephric forma- D plays a role in calcium metabolism. This article will discuss tion is evident before the pronephros has completed its regre: the development of the kidney, and its role in the fetus."' sion. The mesonephros also degenerates in a cranial-to-cauda Since the kidneys are bilateral structures, development sequence. Some of the cranial structures are degenerating in involves both right and left kidneys. During fetal develop- the fifth week of fetal development while the caudal structun ment, three separate nephric structures develop in succession; are still differentiating.
    [Show full text]
  • Mesonephric Duct, a Continuation of the Pronephric Duct
    Anhui Medical University Development of the Urogenital System Lyu Zhengmei Department of Histology and Embryology Anhui Medical University Anhui Medical University ORIGINS----mesoderm ---paraxial mesoderm: somite ---intermediate mesoderm urinary and genital system ---lateral mesoderm paraxial neural intermediate mesoderm groove mesoderm endoderm notochord lateral mesoderm Anhui Medical University Part I Introduction The 【】※ origins of origins of urogenital urogenital system system?? Anhui Medical University differentiation of intermediate mesoderm •intermediate mesoderm Nephrotome nephrogenic cord urogenital ridge mesonephric ridge，gonadal ridge Anhui Medical University 1.Formation of nephrotome Nephrotome: The cephalic portion of intermediate mesoderm becomes segmented, which forms pronephric system and degenerates early. 4 weeks Anhui Medical University intermediate 2.Nephrogenic cord mesoderm Its caudal part gradually isolated from somites, forming two longitudinal elevation along the posterior wall of abdominal cavity Nephrogenic cord urogenital ridge Anhui Medical University 3. Urogenital ridge Mesonephric ridge: The outside part of the urogenital ridge giving rise to the urinary system Gonadal ridge: the innerside part giving rise to the genital system Anhui Medical University Part II Development of Urinary system Three sets of kidney occur in embryo developmnet ( 1)pronephros (2) mesonephros (3) metanephros Development of Bladder and urethra Cloaca Urogenital sinus Congenital anomalies of the urinary system Anhui Medical University
    [Show full text]
  • Developmental Biology
    DEVELOPMENTAL BIOLOGY DR. THANUJA A MATHEW DEVELOPMENT OF AMPHIOXUS • Eggs- 0.02mm in diameter, microlecithal, isolecithal Cleavage- Holoblastic equal • 1st & 2nd Cleavage- Meridional • 3rd Cleavage-lattitudinal- 4 micromeres& 4 macromeres are produced • 4th Cleavage-Meridional & double • 5th Cleavage- lattitudinal & double • 6th Cleavage onwards irregular 2 BLASTULATION • Blastocoel is filled with jelly like subtance which exerts pressure on blastomeres to become blastoderm • Blastula – equal coeloblastula but contains micromeres in animal hemisphere & macromeres in vegetal hemisphere 3 4 GASTRULATION • The process of formation of double layered gastrula. • The outer layer- ectoderm& inner layer- median notochord flanked by mesoderm. The remaining cells are endodermal cells. • Begin after 6 hrs with flattening of prospective endodermal area. • Characterized by morphogenetic movements & antero posterior elongation 6 7 Morphogenetic movements • 1. Invagination of P.endodermal cells into blastocoel reducing the cavity and a new cavity is produced- gastrocoel or archenteron which opens to outside through blastopore • Blastopore has a circular rim - lip • P.notochord lie in the dorsal lip • P.mesoderm lie in the ventro lateral lip 8 • 2. Involution – rolling in of notochord • 3.Covergence- mesoderm converge towards ventro lateral lip and involute in • 4.Epiboly- Proliferation of ectodermal cell over the entire gastrula 9 Antero posterior elongation • Notochord – long median band • Mesoderm- two horns on either sides of notochord Ectoderm • Neurectoderm -elongate into a median band above notochord • Epidermal ectoderm - cover the rest of the gastrula 10 NEURULATION • 1.Neurectoderm thickens to form neural plate. • 2. Neural plate sinks down • 3. Edges of neural plate rise up as neural folds • 4.Neural folds meet and fuse in the mid line • 5.
    [Show full text]
  • Urogenital System for Women
    Journal of Midwifery Vol 6 : No 1 (2021) http://jom.fk.unand.ac.id Article Urogenital System for Women Reyhan Julio Azwan1, Bobby Indra Utama2, Yusrawati3 1Department of Obstetrics and Gynecology, Faculty of Medicine, Andalas University, Padang , Indonesia SUBMISSION TRACK ABSTRACT Recieved: January 20, 2021 Final Revision: June 03, 2021 Functionally, the urogenital system can be divided into two Available Online: June 28, 2021 completely different components : urinary system and genital system. However, embryologically and anatomically, the two KEYWORDS are closely related. Both originate from a single mesodermal urogenital ridge (intermediate mesoderm) along the posterior wall of the abdominal cavity, and initially, the excretory ducts of both CORRESPONDENCE systems enter the same cavity, the cloaca. The urogenital Phone: 0811668272 system is a system consisting of the urinary system which is E-mail: [email protected] divided into the urinary tract and the genital system. Where the urinary system is divided into the upper and lower urinary tracts. The upper urinary tract consists of the kidneys, renal pelvis and ureters, while the lower urinary tract consists of the urinary bladder and urethra. The external genital system in men and women is different, in men it consists of the penis, testes and scrotum, while in women it consists of the vagina, uterus and ovaries. The following will describe the urogenital system in women. Kidney System During intrauterine life, in humans three renal systems are formed which slightly overlap in cranial-to-caudal order: pronephros, mesonephros and metanephros. Pronephros is rudimentary and non-functional; the mesonephros may function in the short term during early fetal life; metanephros forms the permanent kidney.
    [Show full text]
  • The Cleavage Stage Origin of Spemann's Organizer: Analysis Of
    Development 120, 1179-1189 (1994) 1179 Printed in Great Britain © The Company of Biologists Limited 1994 The cleavage stage origin of Spemann’s Organizer: analysis of the movements of blastomere clones before and during gastrulation in Xenopus Daniel V. Bauer1, Sen Huang2 and Sally A. Moody2,* 1Department of Anatomy and Cell Biology, University of Virginia 2Department of Anatomy and Neuroscience Program, The George Washington University Medical Center, 2300 I Street, NW Washington, DC 20037, USA *Author for correspondence SUMMARY Recent investigations into the roles of early regulatory the ventral animal clones extend across the entire dorsal genes, especially those resulting from mesoderm induction animal cap. These changes in the blastomere constituents or first expressed in the gastrula, reveal a need to elucidate of the animal cap during epiboly may contribute to the the developmental history of the cells in which their tran- changing capacity of the cap to respond to inductive growth scripts are expressed. Although fates both of the early blas- factors. Pregastrulation movements of clones also result in tomeres and of regions of the gastrula have been mapped, the B1 clone occupying the vegetal marginal zone to the relationship between the two sets of fate maps is not become the primary progenitor of the dorsal lip of the clear and the clonal origin of the regions of the stage 10 blastopore (Spemann’s Organizer). This report provides embryo are not known. We mapped the positions of each the fundamental descriptions of clone locations during the blastomere clone during several late blastula and early important periods of axis formation, mesoderm induction gastrula stages to show where and when these clones move.
    [Show full text]