DEVELOPMENT
and
HUMAN REPRODUCTION
VOCABULARY
1. EMBRYOLOGY: the study of the
development of embryos
2. CLEAVAGE: series of cell divisions of
the zygote that occurs without growth
until cells are reduced to adult size
3. GASTRULATION: when cells of the
blastula cave in to form the gastrula
4. DIFFERENTIATION: transformation of
unspecialized cells into specialized cells,
tissues, and organs
5. ZYGOTE: the diploid cell
resulting from fertilization of
the egg by sperm
6. EMBRYO: multicellular
organism in the early stages
of development
7. BLASTULA: early stages
of embryonic development
when a single layer of cells
have a fluid filled center
8. GASTRULA: early stage
of embryonic
development when
primary germ layers are
forming
9. MORULA: early stage of
embryonic development
when a solid ball of cells
are formed by cleavage
of the fertilized egg
10. PLACENTA: a temporary
organ through which the
fetus is provided food and
oxygen from the mother and
gets rid of wastes for the
fetus
11. UMBILICAL CORD: the
structure that connects the
fetus to the placenta
12. PRENATAL: before birth
13. POSTNATAL: after birth
14. GESTATION: the length of the pregnancy
15. AMNIOTIC SAC: fluid filled sac that
surrounds and protects the embryo
16. AMNIOTIC FLUID: fluid that fills the
amnion
THE EMBRYO’S EARLY
STAGES OF
DEVELOPMENT
CLEAVAGE
♦ Early mitotic divisions of
the zygote
♦ Increase in cell numbers,
decrease in cell size
♦ Solid ball of cells = morula
♦ Cells then arrange into a
hollow sphere = blastula
♦ Hollow center =
blastoceal
Identify the diagrams
ZYGOTE
MORULA
BLASTULA
GASTRULATION
(occurs in about 3 weeks)
♦
♦
♦
♦
cells start to grow before dividing
cells on one side move inward
inner layers form = primary germ layers
three layered embryo = gastrula
1.
ECTODERM
•
•
•
2.
•
•
•
•
3.
nervous system, brain
lining of mouth, nose, anus
outer layer of skin, nails,
hair
MESODERM
GASTRULA
(three layered embryo)
ENDODERM
bones and muscles
blood and blood vessels
reproductive and excretion cells
inner layer of skin
ENDODERM
•
•
•
•
lining of digestive tract
lining of respiratory tract
liver, pancreas
endocrine glands and bladder
ECTODERM
MESODERM
DIFFERENTIATION
♦ a series of changes in the embryonic cells
resulting in
unspecialized cells → specialized cells → tissues → organs
♦ all cells have the same DNA
♦ different sections of the cells’ DNA may be “turned
off” or “turned on” causing differentiation into
specific kinds of cells
GROWTH
♦ increase in cell size as well as the number
of cells resulting in
GASTRULA
EMBRYO
FETUS
BABY
CHILD
TEEN
ADULT
STAGES OF EMBRYONIC DEVELOPMENT
fertilized egg
2 cells
blastula
4 cells
gastrulation
8 cells
gastrula stage
morula
WHAT an EMBRYO NEEDS
1.
2.
3.
4.
5.
food (yolk)
temperature control
oxygen
waste removal
protection
WHERE DOES DEVELOPMENT
TAKE PLACE?
1. EXTERNAL DEVELOPMENT
or
2. INTERNAL DEVELOPMENT
EXTERNAL DEVELOPMENT
development of the embryo outside of the mother’s
body
(in water or on land)
1. External development in water:
•
•
•
•
food = yolk
oxygen and wastes diffuse in and out
temperature = mating occurs at the right
time of year
large numbers of eggs – so many get eaten
EXTERNAL DEVELOPMENT
development of the embryo outside of the
mother’s body
(in water or on land)
1. External development on land:
•
•
•
•
food = yolk
oxygen and wastes diffuse in and out
watery environment inside the shell
eggs are protective or mom protects (birds)
INTERNAL DEVELOPMENT
development of the embryo inside of the mother’s
body
1. Eggs – sharks, garter snakes (food
provided by yolks)
2. Embryos develop in womb or uterus
•
•
born undeveloped – feed on mother’s milk
well protected by mom (most survive)
INTERNAL DEVELOPMENT
development of the embryo inside of the mother’s body
♦ Placenta mammals – blood circulation of the
embryo in close contact with mom’s through
the placenta
♦ Non-placenta mammals
1.egg-laying mammals (anteater, duckbill platypus)
2.pouched mammals development completes in
pouch (marsupials/kangaroos)
2. amniotic fluid
3. allantois
1. chorion
4. embryo
5. air space
9. shell
6. yolk sac
8. albumin
7. yolk
Give the function of the following:
Extraembryonic membranes:
1. Chorion
♦
Gas exchange between the embryo and the
environment
2. Allantois
♦
♦
♦
Extension of the embryo’s digestive tract
Its blood vessels exchange gases
Collects metabolic waste
3. Amnion
♦
Cushion for protection
4. Yolk sac
♦
Food source