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Chapter 27 review questions
Terms in this set (46)
Gestation is the time that a developing embryo and fetus spends within the uterus, or womb. It is a period of three integrated trimesters, each 3 moths long.
Distinguish among embryonic, fetal and prenatal development
Embryonic development refers to the events that occur during the first 2 months after fertilization. Fetal development begins at the start of the 9th week and continues until birth. Prenatal development consists of both embryonic and fetal development.
What is postnatal development?
Postnatal development begins at birth and continues until maturity.
Fertilization is the fusion of a secondary oocyte and a sperm to form a zygote.
How many chromosomes are contained within a human zygote?
Why are numerous sperm required to fertilize a secondary oocyte?
Man sperm are needed to achieve fertilization because one sperm does not contain enough acrosomal enzymes to erode the corona radiata surrounding the secondary oocyte
A pre-embryo that consists of a solid ball of cells is known as what type of structure?
The morula is the pre-embryo stage that is a solid ball of cells
Describe the trophoblast
The trophoblast is the cell layer surrounding the blastocyst. These cells nourish the embryo and later form part of the placenta.
Describe the blastocyst and its roll in implantation
The blastocyst consists of an outer trophoblast and an inner cell mass. Implantation begins about 6 to 9 days after fertilization, when the blastocyst adheres to the uterine lining, or endometrium. The trophoblast cells in contact with the uterine lining divide and form a syncytiotrophoblast that erodes the endometrial lining. Nutrients from uterine glands are absorbed by the syncytiotrophoblast and distributed by diffusion through the cytotrophoblast to the inner cell mass. The blastocyst becomes enclosed within the endometrium by about 10 days after fertilization.
Describe the process that forms the primary germ layers and cite the layer that contributes to nearly all body systems
Gastrulation is the process that forms the primary germ layers- the endoderm, ectoderm, and mesoderm- from the embryonic disc. It is from these germ layers that the body systems differentiate. The mesoderm contributes to nearly all body systems except the nervous and respiratory systems.
Name the 4 extra-embryonic membranes
The four-extra embryonic membranes are the yolk sac, amnion, allantois, and chorion.
From which germ layers do the extra-embryonic membranes form, and what are each membranes functions?
The yolk sac forms from the endoderm and mesoderm; it is an important site of blood cell formation. The amnion forms from the ectoderm and mesoderm; it encloses the fluid that surrounds and cushions the developing embryo and fetus. The allantois forms from the endoderm and mesoderm; its base gives ride to the urinary bladder. The chorion forms from the mesoderm and cytotrophoblast; it surrounds the blastocoele.
Describe the placenta
The placenta forms the interface between the embryonic/ fetal system and maternal system. It becomes the primary support structure for the developing embryo and fetus. The placenta is the site for nutrient, gas, and waste exchange between maternal and embryonic/ fetal bloodstreams.
Describe the chorionic villi
The chorionic villi are structures that extend outward into the maternal tissues, forming and intricate, branching network through which maternal blood flows. Embryonic blood vessels extend into each chorionic villus.
Compare the body stalk with the yolk stalk
The body stalk is the connection between the embryo and the chorionic; it contains portions of the allantois and blood vessels that carry blood to and from the placenta. The yolk stalk is the connection between the endoderm of the embryo and the yolk sac.
Identify the structure connecting the fetus to the placenta and name the extra-embryonic membrane from which it is derived.
The umbilical cord connects the fetus to the placenta and its derived from the allantois
Name the hormones synthesized by the syncytiotrophoblast
The hormones synthesized by the syncytiotrophoblast are human chorionic gonadotropin (hCG), human placental lactogen (hPL), placental prolactin, relaxin, progesterone, and estrogens.
The presence of which hormone in the urine provides a reliable indicator of pregnancy, as detected by home pregnancy tests?
The presence of human chorionic gonadotropin (hCG) in the urine is a reliable indicator of a pregnancy.
When does the placenta become sufficiently functional to continue the pregnancy?
After the first trimester, the placenta is sufficiently functional to maintain the preganancy
Organogenesis is the process of organ formation
Identify the general events of fetal development during the second and third trimesters.
In the second trimester, the organ systems increase in complexity. During the third trimester, many of the organ systems become fully functional.
A fetus undergoes its largest absolute weight gain during which trimester?
During the third trimester, the fetus undergoes its largest absolute weight gain
List the major change that occur in maternal systems during pregnancy
The major changes that occur in maternal systems during pregnancy are increases in respiratory rate and tidal volume, blood volume, nutrient requirements, glomerular filtration rate (GFR), and the size of the uterus and mammary glands
Why does a mother's blood volume increase during pregnancy?
A mothers blood volume increases during pregnancy to compensate for the reduction in maternal blood volume resulting from blood flow through the placenta.
Based on the illustrations showing the locations of the internal organs in nonpregnant and pregnant women, explain why some pregnant women have trouble breathing.
Some pregnant women have trouble breathing because the enlarged uterus presses up against abdominal organs and the diaphragm, crowding the lungs.
List and describe the factors involved in initiating labor contractions.
Relaxin, produced by the placenta, softens the public symphysis and dilates the cervix, and the weight of the fetus distorts the myometrium of the uterus. Distortion of the cervix and rising estrogen levels promote the release of oxytocin, and the already stretched smooth muscles of the myometrium become even more excitable.
Which chemicals are primarily responsible for initiating contractions of true labor?
Estrogens and oxytocin stimulate the production of prostaglandins, which are then primarily responsible for the initiating true labor.
Name the three stages of labor and describe the event that characterize each stage.
The dilation stage begins with the onset of true labor as the cervix dilates and the fetus begin to move toward the cervical canal; late in this stage, the amnion ruptures.
The expulsion stage begins as the cervix dilates completely and continues until the fetus has completely emerged from the vagina (delivery).
In the placental stage, the uterus gradually contracts, tearing the connections between the endometrium and the placenta and ejecting the placenta (also referred to as the afterbirth).
Explain the difference between colostrum and breast milk.
Colostrum contains antibodies and is produces by the mammary glands from the end of the 6th month pregnancy until a few days after delivery. After that, the glands begin producing breast milk, which contains antibodies and lysozyme but has a higher fat content than colostrum
Which hormone causes the milk ejection (milk let-down) reflex?
Name the stages of postnatal development and describe the time frame involved for each stage.
The postnatal stages of development are:
the neonatal period- from birth to 1 month
infancy, from 1 month to age 1 year
childhood from age 1 year until sexual maturation begins
adolescence, which begin with the onset of sexual maturations (puberty) between ages 10 and 15 years and ends when growth in body size is completed (around 18 years old)
maturity, which includes the rest of the persons life.
A final stage called senescence, or aging, overlaps with maturity.
Name the tree major interacting hormonal events associate with the onset of puberty
The tree interacting hormonal events associated with the onset of puberty are:
(1) increased GnRH production by the hypothalamus
(2) increased sensitivity to GnRH by the anterior lobe of the pituitary gland, and a rapid increase in circulating levels of FSH and LH
(3) increases sensitivity to FSH and LH by ovarian testicular cells
Why does a man have a deeper voice and a larger larynx than a woman?
A man has a deeper voice and a larger larynx than a woman because testosterone stimulates laryngeal development in males to a greater extent than estrogen stimulates laryngeal development in females.
Why are premenopausal women at lesser rick of atherosclerosis than men?
The higher estrogen level in premenopausal women (compared with adult men) decrease plasma cholesterol levels, thereby slowing plaque formation and lowering the risk of atherosclerosis
Distinguish between genotype and phenotype
Chromosomes and their component genes make up the genotype.
Anatomical and physiological characteristics from the expression of genes make up the phenotype.
How do autosomes and sex chromosomes differ?
Autosomes (non-sex chromosomes) are the 22 homologous pairs that affect somatic characteristics. He chromosomes of the 23rd pair are the sex chromosomes that determine whether an individual is male (XY) or female (XX)
How can you tell that the karyotype shown here is male?
The karyotype shown is male because it has an XY for the 23rd pair of chromosomes.
Define homozygous and heterozygous
Homozygous means that homologous chromosomes carry the same allele of a given gene.
Heterozygous means that homologous chromosomes carry different alleles of a given gene
Differentiate between simple inheritance and polygenic inheritance?
In simple inheritance, phenotypic characteristics are determined by interactions between a single pair of alleles.
Polygenic inheritance involved interactions among alleles of several genes.
The trait "freckles" operates through strict dominance. What would be the phenotype of a person who is heterozygous for this trait?
The phenotype of a person who is heterozygous for "freckles"- that is, a person with one dominant allele and one recessive allele for that trait- would be "freckles".
Compare strict dominance with codominance
In strict dominance, one allele dominates the other, so an individual who is heterozygous for a given trait exhibits the dominant phenotype. In codominance, an individual who is heterozygous for a given trait exhibits both of the phenotypes for that trait
Why are sex-linked traits expressed more frequently in males than in females?
Sex-linked traits are expressed more frequently in males because the small Y chromosome of males contains few genes that correspond to those on the larger X chromosome
Indicate the type of inheritance involved in each of the following situations: (1) children who exhibit the trait have at least one parent who also exhibits it; (2) children exhibit the trait even though neither parent exhibits it; and (3) the trait is expressed equally in daughters and sons.
(1) simple inheritance (dominant)
(2) simple inheritance (recessive)
(3) autosomal inheritance
Define single nucleotide polymorphism
A single nucleotide polymorphism is a variation in a single base pair in a DNA sequence
Name the disorder characterized by each of the following chromosomes patters: (1) XO and (2) XXY
(1) XO: Turner syndrome
(2) XXY: Klinefelter syndrome
Identify the chromosome pair involved in each of the following disorders: (1) ovarian cancer, (2) Tay-Sachs disease, and (3) spinocerebellar ataxia.
(1) ovarian cancer: chromosome pair 9
(2) Tay-Sachs disease: chromosome pair 15
(3) spinocerebellar ataxia: chromosome pair 6.
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