![Page 1: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/1.jpg)
Embryonic Development
Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~early stage of development of multicellular organism
Includes:
1. cell division 2. cell growth 3. cell differentiation
~changing of unspecialized embryonic cells into specialized cells, tissues,& organs
![Page 2: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/2.jpg)
Early Embryonic Development
Cleavage is the first major phase of embryonic development It is the rapid succession
of cell divisions (Mitotic) It creates a multicellular
embryo from the zygote NO growth Stages:
1. Morula~solid ball of cells
2.Blastula~ single layer of cells surrounding a fluid-filled cavity called the blastocoel
ZYGOTE 2 cells
4 cells
8 cells
Many cells(solid ball)
BLASTULA(hollow ball)
Cross sectionof blastula
Blastocoel
![Page 3: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/3.jpg)
Embryonic Development
Gastrulation is the second major phase of embryonic development
The cells at one end of the blastula move inward,
It adds more cells to the embryo
It sorts all cells into three distinct cell layers
The embryo is transformed from the blastula into the gastrula
![Page 4: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/4.jpg)
Embryonic Development
The three layers produced in gastrulation
Ectoderm, the outer layer
Endoderm, an embryonic digestive tract
Mesoderm, which partly fills the space between the ectoderm and endoderm
![Page 5: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/5.jpg)
Embryonic Development
The tissues and organs of a tadpole emerge from cells of the ectoderm, mesoderm, and endoderm
![Page 6: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/6.jpg)
Embryonic Development
ectoderm cells~ eventually they develop into the skin and nervous tissue of the animal
endoderm cells ~develop into the lining of the animal’s digestive tract and into organs associated with digestion.
mesoderm cells ~develop into the muscles, circulatory system, excretory system, and, in some animals, the respiratory system.
![Page 7: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/7.jpg)
Embryonic Development
Organs start to form after gastrulationEmbryonic tissue layers begin to
differentiate into specific tissues and organ systems
![Page 8: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/8.jpg)
Changes in cell shape, cell migration, and programmed cell death give form to the developing
animal
Tissues and organs take shape in a developing embryo as a result of cell shape changes cell migration
Ectoderm
![Page 9: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/9.jpg)
Development
programmed cell death (apoptosis)
Cellsuicide
Dead cellengulfed anddigested byadjacentcell
![Page 10: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/10.jpg)
Embryonic induction initiates organ formation
Induction is the mechanism by which one group of cells influences the development of tissues and organs from ectoderm, endoderm, and mesodermAdjacent cells and cell layers use chemical
signals to influence differentiation Chemical signals turn on a set of genes
whose expression makes the receiving cells differentiate into a specific tissue
![Page 11: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/11.jpg)
Pattern formation organizes the animal body
Pattern formation is the emergence of a body form with structures in their correct relative positions It involves the response of genes to spatial
variations of chemicals in the embryo
![Page 12: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/12.jpg)
HUMAN DEVELOPMENT
The embryo and placenta take shape during the first month of pregnancy
Gestation is pregnancy It begins at conception and continues until
birthHuman gestation is 266 days
(38 weeks or 9 months)Mouse gestation is 1 monthElephant gestation is 22 months
![Page 13: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/13.jpg)
HUMAN DEVELOPMENT
Human development begins with fertilization in the oviduct
Ovary
Ovulation
Fertilizationof ovum
Cleavage starts
Blastocyst(implanted
Endometrium
Uterus
Oviduct
![Page 14: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/14.jpg)
HUMAN DEVELOPMENT
Cleavage produces a blastocyst
A blastocyst is a fluid-filled cavity The inner cells of
the blastocyst form the baby
The outer cells form the embryo trophoblast
ENDOMETRIUM
ENDOMETRIUM
Cavity
Trophoblast
Inner cell mass
![Page 15: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/15.jpg)
HUMAN DEVELOPMENT
The trophoblast secretes enzymes to enable the blastocyst to implant in the uterine wall
ENDOMETRIUM
UTERINE CAVITY
Trophoblast
Multiplying cellsof trophoblast
Blood vessel(maternal
Futureyolk sac
Future embryo
![Page 16: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/16.jpg)
HUMAN DEVELOPMENT
Gastrulation occurs and organs develop from the ectoderm, endoderm, and mesoderm
Yolk sac
Mesodermcells
Amnion
Chorion
![Page 17: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/17.jpg)
HUMAN DEVELOPMENT
Meanwhile, the four embryonic membranes develop Amnion~fluid filled sac
for protection Chorion ~ will form the
embryo’s part of the placenta
Yolk sac ~ produces first blood cells &germ cells
Allantois ~ will form the umbilical cord (ropelike structure that attaches embryo to uterus)
Yolk sac
Chorion
Amnion
Allantois
![Page 18: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/18.jpg)
HUMAN DEVELOPMENT
The embryo floats in the fluid-filled amniotic cavity,
The placenta’s chorionic villi absorb food and oxygen from the mother’s blood
Placenta
Amnioticcavity
Chorion
Chorionicvilli
Yolk sac
Mother’s bloodvessels
Embryo
Amnion
![Page 19: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/19.jpg)
Placenta
Food & gases diffuse across blood vessels
![Page 20: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/20.jpg)
HUMAN DEVELOPMENT
Embryonic development of essential organs occur in early pregnancy
The embryo may encounter risks from faults in its genes & from mother’s exposure to environmental factors
The placenta allows for a variety of substances to pass from mother to fetus Protective antibodies German measles virus HIV Drugs (prescription and nonprescription) Alcohol Chemicals in tobacco smoke
![Page 21: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/21.jpg)
Human development from conception to birth is divided into three trimesters
First trimester First three months The most rapid changes occur during the first trimester
7 weeks 10 weeks
4 weeks
![Page 22: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/22.jpg)
Human development from conception to birth is divided into three trimesters
Second trimester Increase in size of fetus General refinement of human features
12 weeks
![Page 23: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/23.jpg)
Human fetal development
The fetus just spends much of the 2nd & 3rd trimesters just growing
…and doing various flip-turns & kicks inside amniotic fluid
Week 20
![Page 24: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/24.jpg)
Human fetal development
24 weeks (6 months; 2nd trimester)
fetus is covered with fine, downy hair called lanugo. Its skin is protected by a waxy material called vernix
![Page 25: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/25.jpg)
Human fetal development
30 weeks (7.5 months)
umbilical cord
![Page 26: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/26.jpg)
Getting crowded in there!!
32 weeks (8 months)
The fetus sleeps 90-95% of the day & sometimes experiences REM sleep, an indication of dreaming
![Page 27: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/27.jpg)
Human development from conception to birth is divided into three trimesters
Third trimester Growth and
preparation for birth
![Page 28: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/28.jpg)
Childbirth is hormonally induced and occurs in three stages
Hormonal changes induce birthLabor is controlled by a positive feedback
mechanismEstrogen released from the ovaries
increases the sensitivity of the uterus to oxytocin
![Page 29: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/29.jpg)
Positive feedback Mechanism
Oxytocin is a powerful stimulant for the smooth muscles of the uterus Oxytocin also
stimulates the placenta to make prostoglandins that stimulate the uterine muscles to contract even more
Uterine contractions stimulate the release of more and more oxytocin and prostoglandins
![Page 30: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/30.jpg)
Birthpositive feedback
![Page 31: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/31.jpg)
Three stages of labor
1.Dilation of the cervix is the first stage
-Cervix reaches full dilation at 10cm Longest stage of
labor (6-12 hours or longer)
Dilation of the cervix
![Page 32: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/32.jpg)
Three stages of labor
Expulsion is the second stage Period from full dilation of
the cervix to delivery of the infant
Uterine contractions occur every 2-3 minutes
Mother feels urge to push down with her abdominal muscles
Infant is forced down and out of uterus and vagina within a period of 20 minutes
![Page 33: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/33.jpg)
Three stages of labor
The delivery of the placenta is the final stage of labor Usually occurs
within 15 minutes after the birth of the baby
![Page 34: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/34.jpg)
The end of the journey!
And you think 9 months of Biology is hard!
![Page 35: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/35.jpg)
Childbirth is hormonally induced and occurs in three stages
Hormones continue to be important after the baby and placenta are deliveredDecreasing progesterone and estrogen
levels allow the uterus to return to its pre-pregnancy state
Oxytocin and prolactin stimulate milk secretion
![Page 36: Embryonic Development Development: series of orderly, precise steps that transform a zygote into a multicellular embryo ~ early stage of development of](https://reader035.vdocuments.site/reader035/viewer/2022062808/56649d9f5503460f94a89a5e/html5/thumbnails/36.jpg)
Reproductive technology increases our reproductive options
Reproductive technology Hormone therapy can
increase sperm or egg production
Surgery can correct blocked oviducts
Assisted reproductive technology In vitro fertilization
(IVF) Surrogate motherhood