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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 (where vertebrae are) – 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
Splancnic
Mesoderm
gives rise
to: Heart
and blood
vessels
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
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What do I need to know?
Which structures originate from ectoderm, mesoderm and
endoderm – Slide 8
List 6 unique features found in all vertebrates at some
stage of their life:
1. tube within a tube
2.bilateral symmetry
3. dorsal hollow nerve cord
4. notocord and vertebrae
5.segmentation
6. pharyngeal pounches
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings


Distinguish between the types of tissues that make up th
eendoderm, ectoderm and mesoderm and explain how
these tissues relate to their developmental processes.
Both endoderm and ectoderm are epithelial tissues. These
cells are joined together in sheets that form external or
internal linings of the body. The mesoderm consists of
mesenchyme tissue whose cells don’t stick together.
Instead, the cells and groups of cells are free to migrate
within the embryo to eventually give rise to muscles, bones
and viscera.(organs)
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings