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PowerPoint® Lecture Slides prepared by Leslie Hendon, University of Alabama, Birmingham 3 HUMAN ANATOMY PART 1 Basic Embryology fifth edition MARIEB | MALLATT | WILHELM Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Embryology Embryology – study of the origin and development of single individual Prenatal period Embryonic period – first 8 weeks Fetal period – remaining 30 weeks Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Embryonic Period Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.1 (1 of 2) Fetal Period Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.1 (2 of 2) The Basic Body Plan Skin – dermis and epidermis Outer body wall – trunk muscles, ribs, vertebrae Body cavity and digestive tube (inner tube) Kidneys and gonads – deep to body wall Limbs Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Basic Body Plan Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.2 The Embryonic Period Week 1 – from zygote to blastocyst Conception – in lateral third of uterine tube Zygote (fertilized oocyte) moves toward the uterus Blastomeres – daughter cells formed from zygote Morula – solid cluster of 12–16 blastomeres “Mulberry” Blastocyst – fluid-filled structure – ~ 60 cells Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Embryonic Period Stages of first week Zygote 4-cell Morula Early blastocyst Late blastocyst (implants at this stage) Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Fertilization and the Events of the First 6 Days of Development Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.3 Week 2 – The Two-Layered Embryo Bilaminar embryonic disc – inner cell mass divided into two sheets Epiblast and the hypoblast Together they make up the bilaminar embryonic disc Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Week 2 – The Two-Layered Embryo Amniotic sac – formed by an extension of epiblast Outer membrane forms the amnion Inner membrane forms the amniotic sac cavity Filled with amniotic fluid Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Week 2 – The Two-Layered Embryo Yolk sac – formed by an extension of hypoblast Digestive tube forms from yolk sac NOT a major source of nutrients for embryo Tissues around yolk sac Gives rise to earliest blood cells and blood vessels Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Implantation of the Blastocyst Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.4 (1 of 3) Implantation of the Blastocyst Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.4 (2 of 3) Implantation of the Blastocyst Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.4 (3 of 3) Week 3 – The Three-Layered Embryo Primitive streak – raised groove on the dorsal surface of the epiblast Gastrulation – a process of invagination of epiblast cells Begins at the primitive streak Forms the three primary germ layers Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Week 3 – The Three-Layered Embryo Three Germ Layers* Endoderm – formed from migrating cells that replace the hypoblast Mesoderm – formed between epiblast and endoderm Ectoderm – formed from epiblast cells that stay on dorsal surface *All layers derive from epiblast cells! Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Primitive Streak Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.5e–h The Notochord Primitive node – a swelling at one end of primitive streak Notochord forms from primitive node and endoderm Notochord – defines body axis Is the site of the future vertebral column Appears on day 16 Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Formation of the Mesoderm and Notochord Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.6 Neurulation Neurulation – ectoderm starts forming brain and spinal cord Neural plate – ectoderm in the dorsal midline thickens Neural groove – ectoderm folds inward Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Neurulation Neurulation (continued) Neural tube – a hollow tube pinches off into the body Cranial part of the neural tube becomes the brain Maternal folic acid deficiency causes neural tube defects Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Neurulation Neural crest Cells originate from ectodermal cells Forms sensory nerve cells Induction Ability of one group of cells to influence developmental direction of other cells Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Mesoderm Begins to Differentiate Somites – our first body segments Paraxial mesoderm Intermediate mesoderm – begins as a continuous strip of tissue just lateral to the paraxial mesoderm Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Mesoderm Begins to Differentiate Lateral plate – most lateral part of the mesoderm Coelom – becomes serous body cavities Somatic mesoderm – apposed to the ectoderm Splanchnic mesoderm – apposed to the endoderm Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint® Lecture Slides prepared by Leslie Hendon, University of Alabama, Birmingham 3 HUMAN ANATOMY PART 2 Basic Embryology fifth edition MARIEB | MALLATT | WILHELM Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Changes in the Embryo Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.7a, b Changes in the Embryo Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.7c, d Week 4 – The Body Takes Shape Folding of embryo laterally and at the head and tail Embryonic disc bulges; growing faster than yolk sac “Tadpole shape” by day 24 after conception Primitive gut – encloses tubular part of the yolk sac Site of future digestive tube and respiratory structures Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Week 4 – The Body Takes Shape Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.8 Week 4 – The Body Takes Shape Derivatives of the germ layers Ectoderm forms Brain, spinal cord, and epidermis Endoderm forms Inner epithelial lining of the gut tube Respiratory tubes, digestive organs, and urinary bladder Notochord – gives rise to nucleus pulposus within intervertebral discs Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Week 4 – The Body Takes Shape Mesoderm – forms Muscle Bone Dermis Connective tissues (all) Mesoderm differentiates further and is more complex than the other two layers Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Derivatives of Germ Layers Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.10 Week 4 – The Body Takes Shape Mesoderm (continued) Somites divides into Sclerotome Dermatome Myotome Intermediate mesoderm forms Kidneys and gonads Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Week 4 – The Body Takes Shape Mesoderm (continued) Splanchnic mesoderm Forms musculature, connective tissues, and serosa of the digestive and respiratory structures Forms heart and most blood vessels Somatic mesoderm – forms Dermis of skin Bones Ligaments Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings PowerPoint® Lecture Slides prepared by Leslie Hendon, University of Alabama, Birmingham 3 HUMAN ANATOMY PART 3 Basic Embryology fifth edition MARIEB | MALLATT | WILHELM Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings The Germ Layers in Week Four Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.9a–d Week 5-8 – The Second Month of Embryonic Development Limb buds form Embryo first looks recognizably human (week 8) Head is disproportionately large All major organs are in place Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3.11 The Fetal Period PLAY A time of maturation and rapid growth Cells are differentiating during the first half of the fetal period Normal births occur 38 weeks after conception Premature birth is one that occurs before 38 weeks Ultrasound of Fetus Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Developmental Events of the Fetal Period Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Table 3.1 (1 of 3) Developmental Events of the Fetal Period Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Table 3.1 (2 of 3) Developmental Events of the Fetal Period Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings Table 3.1 (3 of 3)