gestation chapter 51 section 3. fertilization from the moment of fertilization until the time of...
TRANSCRIPT
Gestation
Chapter 51Section 3
Fertilization From the moment of fertilization until the
time of birth, about 9 months, is called gestation
Each sex gamete contains one set of chromosomes
After a sperm penetrates the egg, the egg undergoes meiosis II and the sperms nucleus fuses with the eggs nucleus
Takes 1n cells and makes them 2n cells Known as a zygote
Haploid-----Diploid
Fertilization occurs in the fallopian tubes
Cleavage While still in the fallopian tubes, the
fertilized egg undergoes a series of mitotic division This is known as cleavage
This cleavage produces a ball of cells called a morula Not much larger than the zygote
This morula will divide and release a fluid resulting in a blastocyte
Implantation
The morula makes it way to the uterus
Attaches to the thickened uterine lining
Releases an enzyme that breaks down the epithelial tissue and burrows into the wall.
The process of burrowing and embedding is called Implantation
Pregnancy
Will be split up into trimesters
During each trimester, significant changes occur
Typically a 9 month period
First Trimester
Most dramatic change in human development occurs during the first trimester
For the first 8 weeks, the developing human is called an embryo
During the first 2-3 weeks, the embryo will resemble embryos of other animals
First Trimester During development an amniotic sac forms
around the embryo This fluid in the sac cushions the embryo
A second membrane forms a yolk sac This is where the first blood cells originate
Another membrane called the chorion surrounds all the membranes. This membrane will form small fingerlike
projections in the uterine lining.
These projections will join with a portion of the uterine lining to form the placenta
First Trimester The placenta
Nutrients, gases, pathogens, drugs and other substances can pass from mother to embryo through the placenta
MOTHERS don’t do drugs!
Embryo is attached to the placenta by the umbilical chord
From 8 weeks until birth, the developing tiny human is called a fetus
Organogenesis
The process by which the ectoderm, the mesoderm, and the endoderm layers develop into internal organs
Second Trimester During the second trimester the uterus
enlarges
The heartbeat can be heard
Skeleton forms
Layer of soft hair grows over the skin
The fetus wakes and sleeps This is when the mother feels the baby move
Fetus swallows and sucks it thumb
Can make a fist, hiccup, kick its feet, and curl its toes
By the end of the 2nd trimester the fetus is 13.4in long
Second Trimester
Third Trimester During the 3rd trimester, the fetus
grows quickly and undergoes the changes that allows it to survive outside the mothers body
Can see light and darkness
Can react to music and loud sounds
During the last half of the trimester, the fetus develops fat deposits Makes a baby look rounded and less
wrinkled Will also insulate the body to
maintain a steady temperature
Birth
Are you ready to watch a video of childbirth? Neither am I
Usually occurs 38 weeks after fertilization
All muscular contractions and other events that lead to childbirth are called Labor
The afterbirth is the expulsion of placenta, amnion sac, and uterine lining after childbirth
One more nerd video!
You are now done with all the learning for this school year.
I hope you guys have enjoyed the power points and they have helped you learn
Baby after birth
Newborns lungs expand for the first time
Umbilical cord is cut and tied The umbilical veins and arteries
close off within 30 minutes
This and other changes all for completion of the cardiopulmonary and renal circulation Allows baby to survive independent
of mother
Respiratory and excretory systems become fully functional