The ectodermal cells migrate to form a raised groove known as the ________.
The result of polyspermy in humans is ________.
a nonfunctional zygote
It is impossible for sperm to be functional (able to fertilize the egg) until after ________.
they undergo capacitation
Milk ejection or let-down reflex is stimulated by which of the following hormones associated with pregnancy?
Estrogen and progesterone maintain the integrity of the uterine lining and prepare the mammary glands to secrete milk. Which of the following structures makes this possible during the first three months of pregnancy?
The placenta, a vitally important metabolic organ, is made up of a contribution from mother and fetus. Which portion is from the fetus?
Relaxin is a hormone produced by the placenta and ovaries. The function of this hormone is to ________.
relax the pubic symphysis
Hyaluronidase and proteinase are enzymes. How do they function in reproduction?
They act to break down the protective barriers around the egg, allowing the sperm to penetrate.
Which of the following is not a germ layer?
The formation of endodermal and ectodermal germ layers occurs at ________.
The lateral mesoderm forms ________.
the epithelial lining of the GI tract
Which of the following is a highly unlikely method of producing a child?
Failure of the foramen ovale to close at birth may result in ________.
mixing of oxygenated and nonoxygenated blood
Implantation involves ________.
embedding of the blastula in the uterine wall
The umbilical arteries carry ________.
waste products to the placenta
The correct sequence of preembryonic structures is ________.
zygote, morula, blastocyst
One sign of an infantʹs physical condition that is first noticed at birth is which of the following?
Hormones concerned with events of lactation include ________.
Just after implantation occurs, nutrition of the young embryo is primarily provided by ________.
digestion of endometrial cells
Onset of labor may be a result of all of the following factors except ________.
aspirin and similar drugs
Select the correct statement about fertilization.
Millions of sperm cells are destroyed by the vaginaʹs acidic environment.
signals the division of the trophoblast into two distinct layers
The surface cells of the inner cell mass become ________.
the primitive streak
Muscle tissue is formed by the ________.
Neural tissue is formed by the ________.
The trophoblast is responsible for forming the ________.
The cardiovascular system of a newborn must be adjusted after the infant takes its first breath. Which of the following is also true?
The ductus arteriosus constricts and is converted to the ligamentum arteriosum.
Sperm move to the uterine tube through uterine contractions and the energy of their own flagella. What other factor is involved in sperm movement?
reverse peristalsis of the uterus and uterine tubes
At which stage of labor is the ʺafterbirthʺ expelled?
Which hormone is not produced by the placenta?
During which stage of labor is the fetus delivered?
Implantation of the blastocyst is the result of all of the following except ________.
phagocytosis by the trophoblast cells
Cleavage as part of embryonic development is distinctive because it involves ________.
cell division by mitosis with little or no growth between successive divisions
Which of the following is true in reference to what may pass through the placental barriers?
nutrients, respiratory gases, wastes, and alcohol
Which of the following is not usually considered a teratogen?
Derivatives of the ectoderm include ________.
epithelium of the pineal and pituitary glands
Derivatives of the mesoderm include ________.
endothelium of blood and lymph vessels
Derivatives of the endoderm include ________.
epithelium of the respiratory tract
Developmental events during weeks 13-16 include ________.
the face looking human and the body beginning to outgrow the head
Developmental events during weeks 17-20 include ________.
limbs achieving final proportions
Developmental events during weeks 21-30 include ________.
distal limp bones beginning to ossify
Which metabolic change does not occur as the placenta enlarges?
increased levels of calcitonin
Select the correct statement about the special fetal blood vessels.
The umbilical vein becomes the ligamentum teres.
Which of the following statements about the events of fertilization is not true?
The two pronuclei divide.
Which developmental event occurs during the embryonic period?
Weak spontaneous muscle contractions just begin.
The decidua basalis is ________.
located between the developing embryo and the myometrium