補充 Development's phases for human
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beings.
2
3- 4 days
Fig. 16.8 (a)
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Fig. 15.10 The sperm have reached the egg and have
surrounded it. However, only one sperm will enter into
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fertilization.
4
Table 16-1 Early stages of
development
1. Fertilization (受精)
2. Cleavge (卵割)
3. Morula (桑椹胚)
3. Blastula (囊胚)
3. Gastrulation (原腸胚形成)
4. Neurulation (神經管形成)
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5
卵割
桑椹胚
囊胚期
Migration of cells
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卵割階段
Fig. 16.3 The gradual development of a grog embryo from the first
cleavage toward the morula stage.
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Frog
Chicken
Human
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Fig. 16-4a A comparison of Life
the
development of three vertebrates.
8
Frog
Chicken
Human
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Fig. 16-4b A comparison of Life
the
development of three vertebrates.
9
5-6 days
Fig. 16-8b
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10
Blustrula stage
Gratrulation stage
Fig. 16-5 a hen's egg.
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Table 16.2 Structures
Produced by the three
germ layers
Ectoderm All nervous
tissue; epidermis of skin,
parts of eyes and ears, hair,
pituitary gland, adrenal
medulla
Endoderm most linings of
digestive system, of
respiratory system
Mesoderm muscle,
cartilage, bone, blood,
Kidneys and gonads
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Fig. 16.1 Neurulation.
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Fig. 16-6 The basic tubewithin-a tube structure of
most invertebrates and
vertebrates.
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13
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Fig. 16-6 The basic tubewithin-a tube structure of
most invertebrates and
14
vertebrates.
羊膜
尿囊膜
絨毛膜
卵黃囊
Fig. 16-7 later development of membranes in the chick embryo
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Fig. 16-7 later development of membranes in the chick embryo
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補充 Late stage of development of the
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allantois in a chick
embryo.
17
Amnion
chorion
allantois
Yolk sac
Extraembryonic
coelom
補充 Early stage of development of the allantois
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in a four-day-oldLifechick
embryo.
18
補充 Embryo of placental mammal.
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19
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Fig. 16-4a A comparison of Life
the
development of three vertebrates.
20
Frog
Chick
Human
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Fig. 16-4a A comparison of Life
the
development of three vertebrates.
21
補充 various vertebrates
embryos at the
organogenesis stage of
development illustrating
similarity of gross structure.
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22
Fig. 16-2 Lens induction
in the vertebrate eye.
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23
Fig. Schematic of the Saunders-Zwilling hypothesis for the mutual
interactions of the apical extodermal ridge (AER) and mesoderm.
The AER stimulates mesodermal outgrowth, while an apical
ecotodermal maintenance factor (AEMF) from mesoderm promotes
the health and well being of the AER. The zone of polarizing activity
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(ZPA) may influence anterior-posterior
determination.
Fig. Experimental procedures (a, b) and results (a', b') of grafting
additional putative zones of polarizing
activity (ZPA) to different sites on25
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Fig. In the normal limb (A), the zone of polarizing activity is presumed
to be the source of morphogen, which would theoretically diffuse across
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26
the limb to form a concetration Life
curve,
as seen in B.
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27
Human development
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28
← At the beginning of the 2nd week, the embryo
has developed extensive membranes that lie in
close contact with the mother's tissues.
→ Well into the 3rd
week, the chorionic
membrane has
continued to penetrate
the mother's
endometrium. The
balloonlike structure The embryo at the 4th week↑. The dark lies
protected in its amniotic sac. The dark eye is
is the yolk sac.
prominent and the enormous brain lies trucked
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against theLifeembryonic
heart.
29
↑The human embryo is
shown at 42 days with
the surrounding
membrane removed .
It is about 16 mm long.
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At 6 weeks, with the
amnion removed, the
fingers are apparent and
the bulbous brain still
dominates the embryo.
Notice the tail trucked
under the abdomen.
The tiny pit above the
arm will become the ear.
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At about 7 weeks, the
embryo afloat in its
amniotic fluid, is clearly
anchored to its placenta by
the twisted umbilical cord
through which great blood
vessels pass.
The abdomen is swollen
due to the rapid growth of
the liver, the main bloodforming organ at this time.
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The 8-week embryo is
shown here is front view.
The organs are now more or
less complete.
The skeletal system is
among the last to form, but
bones are now evident in the
arms and legs.
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At 9 week lids have begun
to grow down over the eyes,
and the outer ear begins to
from.
The fetus may begin to
move, wave its arms and
legs, and may even suck its
thumb.
It is now beginning to fill
its amniotic space and will
assume the typical upsidedown fetal posture.
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At 10 weeks the skeleton is
well along in its
development.
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At 14 weeks the fetus is e
fist-sized. Ribs and blood
vessels are visible through
the translucent skin.
The vigorous movements of
the fetus can now be felt by
the mother.
Refinements such as
fingerprints and fingernails
have not yet developed.
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By the end of 5 months the fetus is
covered with fine-downy hair and its
head may have already started to
grow its own crop.
The heart is beating now at a rate of
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120 to 160 times per minute.
37
Fig. 16-9 The development of the human
embryo showing relative size at different
ages.
Note that at 4 weeks, every few features
are clearly distinguishable. The major
organs have begun to form. The embryo
at this time is strangely vulnerable to a
variety of dangers from drugs to radiation.
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Would you give a cigarette
to your unborn child?
You do every time you
smoke!
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Fig. 16-11 A plea
from a concerned
39
citizen.
Essay 16.1 Can humans
regenerate missing parts?
這隻手曾被鱷魚咬斷，再重新接
回來，並用這些裝置固定住。
幾年前，有位年青的男孩，不小
心切斷小手指頭。於醫院，通常
會將斷掉的部份，再重新接回來。
但由於醫療人員的疏失，包紮後，
忘了進行接縫的手術。過了幾天，
當這個疏失被發覺後，醫生急忙
來看情況。令他們吃驚的是，這
個手指有自行再生回來的趨勢。
目前，對小孩而言，醫院普遍採
用此再生的方法來處理相同的案
例。
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Essay 16.2 Wound healing.
Flesh wounds are dangerous. The protective covering around the body
has been broken, leaving an opportunity for invasion, by dangerous
organisms.
The body acts quickly by first sealing blood vessels in a process called
clotting (凝血).
Platelets (血小板) rush to the site, where they interact with a blood
protein called fibrinogen to form the clot. Some of the platelets releasing
a substance called serotonin, which constricts the blood vessels in the
area.
Once the blood flow has stopped, the body
begins to respond to other chemicals
(pyrogens) that have been released in
response to the trauma. 這可以促進地區的
血液循環，引入更多的白血球。
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An ethical concern
• 試管嬰兒，抽取夫妻的精子和卵子進行
體外受精。
• Some couples found out that the eggs and
sperm used were not theirs at all.
• Would you want to know if your baby bore
your genes?
• What would you do if the baby didn't?
• Would your feelings for the baby change?
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問題與討論
 請提出問題！
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