Flashcards in [Chapter 39] Reproduction Deck (172)
Describe what happens during day 5 after fertilization.
A blastocoel (fluid-filled cavity) forms in the morula as a result of surface cell secretions. By the thirty-two-cell stage, differentiation is occurring in an inner cell mass that will give rise to the embryo proper. This embryonic stage is the blastocyst.
Describe what happens during days 6-7 after fertilization.
Some of the blastocyst’s surface cells attach themselves to the endometrium and start to burrow into it. Implantation has started.
What is implantation?
The blastocyte attaches to the uterine lining, and the burrows into the endometrium. The inner cell mass develops into two flattened layers of cells called the embryonic disk.
What is the Amnion?
A membrane that will enclose the embryo in a fluid-filled, buoyant cavity.
What is the Chorion?
A third membrane that lines amnion and yolk sac, becomes part of placenta.
What is the Yolk Sac?
Germ cell source, becomes site of red blood cell formation.
What is the Placenta?
An organ that functions in exchanges of materials between the bloodstreams of a mother and her developing child.
What is the Allantois?
The fourth extraembryonic membrane, source of urinary bladder and blood vessels for the placenta.
Describe what happens during days 10-11 after fertilization.
The yolk sac, embryonic disk, and amniotic cavity have started to form actual from parts of the blastocyst.
Describe what happens during day 12 after fertilization.
Blood-filled spaces form in maternal tissue. The chorionic actual cavity starts to form.
Describe what happens during day 14 after fertilization.
A connecting stalk has formed between the embryonic disk and chorion. Chorionic villi,which will be features of a size placenta, start to form.
What is the inner cell mass of a blastocyte two weeks after fertilization?
A two-layered embryonic disk.
What is the Ectoderm of the Human Germ Layers?
Outer layer (epidermis) of skin; nervous tissue.
What is the Mesoderm of the Human Germ Layers?
Middle layer, connective tissue of skin; skeletal, cardiac, smooth muscle; bone; cartilage; blood vessels; urinary system; gut organs; peritoneum (coelom lining); reproductive tract.
What is the Endoderm of the Human Germ Layers?
Inner layer, lining of gut and respiratory tract, and organs derived from these linings.
What is Spina Bifida?
A birth defect where the neural tube and one or more vertebrae do not form as they should. The spinal cord will protrude out of the vertebral column at birth.
What are somites?
Multiple paired segments that arise from the mesoderm during the end of the third week, the embryonic sources of most bones as well as the head and trunk's skeletal muscles and overlying dermis.
True or False: Vessels of the embryo’s circulatory system extend through the umbilical cord to the placenta, where they run through pools of maternal blood. Maternal and embryonic blooddo not mix; substances diffuse between the maternaland embryonic bloodstreams.
True, all exchange of materials between an embryo and its mother takes place by the placenta.
How big is the embryo after the fourth week?
500 times its starting size, but still less than a centimetre in length.
What happens in the second trimester?
Developing nerves and muscles connect up, reflexive movements begin. Legs kick, arms wave about, and fingers grasp. At five months old, its heartbeat can be heard clearly through a stethoscope positioned on the mother’s abdomen. Movements of fetal arms and legs can be sensed. Soft, fetal hair (the lanugo) covers the skin (most will be shed before birth). A thick, cheesy coating protects the wrinkled, reddish skin from abrasion. In the sixth month eyelids and eyelashes form.
What happens at the beginning of the third trimester?
Eyes open (seventh month), all the portions of the brain have formed and have begun to function.
What do B-complex vitamins do for the embryo?
Taken early in the pregnancy, it reduce's the embryos risk of neural tube defects.
Why should pregnant women eat well-cooked meat and avoid cat feces (Besides common sense)?
To minimize the risk of infectious diseases leading to developmental problems, miscarriages, or stillbirth.
What is Fetal Alcohol Syndrome (FAS)?
Alcohol intake during pregnancy that leads to small head and brain, facial abnormalities, slow growth, mental impairment, possible heart problems, and poor coordination. The damage is permanent.
What does smoking lead to during pregnancy?
Increases risk of miscarriage, adversely affects fetal growth and development. Carbon monoxide in the smoke can outcompete oxygen for the binding sites on hemoglobin. Children of smokers are more likely to die of post delivery problems, be smaller, and have more heart defects.
What can Thalidomide lead to?
Infants of some of the women who used it during the first trimester had severely deformed arms and legs or none at all.
What can use of Isotretinoin (Accutane) lead to?
If taken early in a pregnancy, it can cause facial and cranial deformities and heart problems in the embryo.
What is the birth process known as?
What is Afterbirth?
Expelled placenta from the uterus.