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PART 1. Basic Embryology. Embryology. Embryology – study of the origin and development of single individual Prenatal period Embryonic period – first 8 weeks Fetal period – remaining 30 weeks. Embryonic Period. Figure 3.1 (1 of 2). Fetal Period. Figure 3.1 (2 of 2). - PowerPoint PPT Presentation
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PowerPoint® Lecture Slides prepared by Leslie Hendon,
University of Alabama, Birmingham
HUMAN ANATOMY
fifth edition
MARIEB | MALLATT | WILHELM
3
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Basic Embryology
PART 1
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
Figure 3.1 (1 of 2)
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Fetal Period
Figure 3.1 (2 of 2)
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
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
Figure 3.2
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
The Embryonic Period
Week 1 – from zygote to blastocyst Conception – in lateral third of uterine tube
Zygote (fertilized oocyte) moves toward the uterusBlastomeres – 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
Figure 3.3
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
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
Figure 3.4 (1 of 3)
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Implantation of the Blastocyst
Figure 3.4 (2 of 3)
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Implantation of the Blastocyst
Figure 3.4 (3 of 3)
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
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
Figure 3.5e–h
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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
Figure 3.6
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
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
bodyCranial part of the neural tube becomes the brainMaternal 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
PowerPoint® Lecture Slides prepared by Leslie Hendon,
University of Alabama, Birmingham
HUMAN ANATOMY
fifth edition
MARIEB | MALLATT | WILHELM
3
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Basic Embryology
PART 2
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Changes in the Embryo
Figure 3.7a, b
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Changes in the Embryo
Figure 3.7c, d
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
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
Figure 3.8
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
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
bladderNotochord – 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
Figure 3.10
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Week 4 – The Body Takes Shape
Mesoderm (continued) Somites divides into
SclerotomeDermatomeMyotome
Intermediate mesoderm formsKidneys 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 skinBonesLigaments
PowerPoint® Lecture Slides prepared by Leslie Hendon,
University of Alabama, Birmingham
HUMAN ANATOMY
fifth edition
MARIEB | MALLATT | WILHELM
3
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Basic Embryology
PART 3
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
The Germ Layers in Week Four
Figure 3.9a–d
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
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
Figure 3.11
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
The Fetal Period
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
PLAY Ultrasound of Fetus
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Developmental Events of the Fetal Period
Table 3.1 (1 of 3)
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Developmental Events of the Fetal Period
Table 3.1 (2 of 3)
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Developmental Events of the Fetal Period
Table 3.1 (3 of 3)