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Chapter 29

Proteins exhibit more and more abnormalities in amino acid sequence with age
false - mostly folding
Older people have more trouble with thermoregulation because they have more subcutaneous fat and cannot dissipate body heat efficiently
false - they have less subcutaneous fat
During implantation and about six days after ovulation, the trophoblast forms a deep layer that retains individual cells called the ____ and a superficial layer composed of a multinucleate mass of cells whose plasma membranes broke down called the _____.
cytropholast; syncytiotrophoblast
As it implants, the conceptus is nourished by means of
trophoblastic nutrition
the chorion forms the fetal part of the placenta
In order for an egg to survive, it must be fertilized within _____ hours of ovulation
12 to 24
which of these lists the stages of prenatal development in correct order?
zygote, cleavage, morula, trophoblast, embryo, fetus
the epidermis, nervous system, pituitary, internal and external ear are derived from
The skin and hair become drier in old age because of
senescence of the sebaceous glands
an individual becomes a fetus at the end of _____ of gestation.
8 weeks
Which of these organ systems shows the greatest structural change in the transitional period after birth?
The capacitation of sperm involves
the removal of cholesterol from the plasma membrane
These are derivatives of ectoderm except
the dermis
At 5 months gestation, a fetus is covered with a cheesy sebaceous secretion called
vernix caseosa
Evolutionary theorists no longer believe that a function of death is to eliminate old and frail individuals for the good of the species
The first 6 weeks of postpartum life constitute
the neonatal period
Senescence of the immune system makes older people more subject to cancer and infectious disease because of a decline in
antigen-presenting cells and helper T cells
The fine hair on the body of a 5-month-old fetus is
By the time the conceptus arrives in the uterus
it consists of 16 or more cells
Most fetal blood bypasses the liver by way of a shunt called
the ductus venosus
Teratogens usually do not cause congenital anomalies
The observation that there is a limit to how many times a cell can divide is the basis for the
replicative senescence theory
The __________ encloses all the rest of the membranes and the embryo
The optimal "window of opportunity" to conceive a child is
a few days before ovulation to less than a day after
The neonatal period of life is considered to extend to an age of
6 weeks
During implantation, the embryoblast undergoes gastrulation
If the blastocyst implants in the uterine tube instead of the uterus, the pregnancy is called
This figure shows the placenta and embryonic membranes. What does "1" represent?
the placenta
Down syndrome (trisomy-21) results from
Prior to ejaculation, __________ in the sperm plasma membrane prevents premature release of ____________
Cholesterol; acrosomal enzymes
Which of these is not part of the pre embryonic stage of development
differentiation of organs
The cytotrophoblast is composed of cells that later become the embryo
Muscular weakness tends to develop in old age for all of the following reasons except
Reduced perfusion of the muscles ?????
slower conduction??????
In the blastocyst, the trophoblast will become _____, and the embryoblast will become _______.
part of the placenta; the embryo
In the fast block polyspermy, binding of sperm opens up _________ channels, which depolarizes the egg membrane and __________
Na+; prevents the entrance of any more sperm
During implantation, the trophoblast divides into a deep layer, the _____________, composed of individual cells, and a superficial layer, the _________, composed of a multinucleate mass of cytoplasm
cytotrophoblast; syncytiotrophoblast
The digital rays of a fetus give rise to
fingers and toes
The embryonic membranes include all of the following except the
These are have potentially teratogenic effects except
a teratogen is most likely to cause
a deformity of the limbs