Transcript Chapt17 Lecture 13ed Pt 2

Human Biology
Sylvia S. Mader
Michael Windelspecht
Chapter 17
Development
and Aging
Lecture Outline
Part 2
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1
17.2 Pre-Embryonic and Embryonic Development
2. Embryonic development: Week 2
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amniotic cavity
embryonic disk
yolk sac
chorionic villi
chorion
a. 18 days
Figure 17.4a The stages of embryonic development.
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17.2 Pre-Embryonic and Embryonic Development
3 primary germ layers
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endoderm
mesoderm
amnion
amniotic cavity
notochord
ectoderm
yolk sac
Endoderm
Primary
Germ Layer
Ectoderm
(outer layer)
Mesoderm
(middle layer)
Ectoderm
Endoderm
(inner layer)
Figure 17.5 The embryonic germ layers.
Mesoderm
Human Adult Structures
Epidermis of skin; epithelial lining of oral
cavity and rectum; nervous system
Skeleton; muscular system; dermis of
skin; cardio vascular system; urinary
system; reproductive system; outer layers
of respiratory and digestive systems
Epithelial lining of digestive tract and
respiratory tract; associated glands of
these systems; epithelial lining of urinary bladder
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17.2 Pre-Embryonic and Embryonic Development
2. Embryonic development: Week 3
•
Nervous system
begins to develop.
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body stalk
•
The posterior neural
tube will become
the spinal cord and
brain.
amniotic cavity
allantois
embryo
yolk sac
chorionic villi
21 days
•
Development of the
heart begins.
Figure 17.4b The stages of embryonic development.
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17.2 Pre-Embryonic and Embryonic Development
2. Embryonic development: Weeks 4 and 5
•
4th week
– Embryo is slightly larger than the height of the
print in your _____.
– Chorionic villi form.
– Umbilical cord forms.
– _____________ form (later develop into legs
and arms).
– Hands and feet are apparent.
•
5th week
– Head enlarges.
– Eyes, ears, and nose become prominent.
5
17.2 Pre-Embryonic and Embryonic Development
2. Embryonic development: Weeks 4 and 5
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chorion
amnion
amniotic cavity
allantois
yolk sac
chorionic villi
amniotic cavity
c. 25 days
chorion
digestive tract
chorionic villi
amnion
umbilical cord
d. 35+ days
Figure 17.4c-d The stages of embryonic development.
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17.2 Pre-Embryonic and Embryonic Development
The embryo at week 5
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tail
brain
brain
optic
vesicle
optic
vesicle
tail
pharyngeal
pouch
pharyngeal
pouch
heart
region of
heart, liver
liver
limb bud
limb bud
umbilical
vessel
umbilical
vessel
somite
a.
b.
gastrointestinal tract
limb bud
© Lennart Nilsson, A Child is Born, Dell Publishing/Scanpix
Figure 17.6 The human embryo after five weeks of development.
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17.2 Pre-Embryonic and Embryonic Development
2. Embryonic development: Weeks 6-8
•
Embryo begins to look like a human being.
•
__________ actions occur.
•
All organ systems have been established.
•
The embryo is 38 mm by the end of this period
and weighs about the same as an aspirin
tablet.
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8 Weeks
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17.3 Fetal Development
3. Fetal development: Months 3 and 4
•
•
•
•
•
•
Hair develops.
The head slows in growth so that the body size
can catch up.
Cartilage begins to be replaced by _______.
It is possible to distinguish female from male
(month __).
The heartbeat can be heard with a stethoscope
(month __).
By the end of this period, the fetus is ~6 inches
and ~6 ounces.
10
20 Weeks
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12
13
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17.3 Fetal Development
3. Fetal development: Months 5-7
•
•
•
•
Fetal movement
can be felt by the
mother.
Fetus is in fetal
position.
Eyelids are fully
open.
Fetus size has
increased to ~12
inches and ~3
pounds.
Figure 17.8 A five- to seven-month-old fetus.
15
28 Weeks
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