Chapter 28 Pregnancy and Human Development
1. Answer: D
2. Answer: A
3. Answer: B
4. Answer: C
5. Answer: E
6. Answer: Amnion
7. Answer: Chorionic villus
8. Answer: Yolk sac
9. Answer: Decidua basalis
10. Answer: Decidua capsularis
6) Protective water-filled sac surrounding the embryo.
7) Extraembryonic membrane that develops from the trophoblast and some extraembryonic mesoderm, and forms part of the placenta.
8) Site of early blood cell production, and forms part of the gut (digestive tube).
9) The part of the endometrium destined to be a part of the placenta.
10) The part of the endometrium that surrounds the uterine cavity face of the implanted embryo.
Match the following:
11) Leads to the development of a morula and then a blastocyst.
12) Embedding of the blastocyst in the uterine wall.
13) Leads to the formation of the first cell of the new individual.
14) Leads to the establishment of the three primary germ layers.
15) Leads to enhancement of sperm motilityand increasing membrane fragility to enable enzyme release from acrosomes.
1) Conceptus is a term used to describe the developing human offspring.
2) The period from fertilization through week eight is called the embryonic period.
3) Fertilization occurs while the egg is still in the ovarian follicle.
4) Freshly deposited sperm are not capable of penetrating an oocyte.
5) By 72 hours after fertilization, the egg has divided into more than 160 cells and is called the morula.
6) Implantation begins six to seven days after ovulation.
7) A pregnancy test involves antibodies that detect GH levels in a woman's blood or urine.
8) The body systems of the developing embryo are present in at least rudimentary form at eight weeks.
9) Of the three germ layers, the mesoderm forms the most body parts.
10) A pregnant woman urinates more often than usual because the uterus compresses the bladder, and she must also dispose of fetal metabolic wastes.
11) The "fluid-filled, hollow ball of cells" stage of development is the blastocyst.
12) The embryonic stage lasts until the end of the eighth week.
13) The embryo is directly enclosed in and protected by the amnion.
14) In fetal circulation, one way in which blood bypasses the nonaerated lungs is by way of the foramen ovale.
15) An episiotomy is an incision made to widen the vaginal orifice, aiding fetal expulsion.
16) The placenta and its attached fetal membranes are collectively called the afterbirth.
17) Human placental lactogen initiates labor.
18) Surfactant production in premature infants is rarely a factor in providing normal respiratory activity.
19) A blastocyst is a hollow ball of cells, while the morula is a solid ball of cells.
20) A zygote is usually formed within the uterus.
Fill-in-the-Blank/Short Answer Questions
1) The first "milk" the mother produces is called ________.
2) As the newborn suckles, the mother's pituitary produces ________ to assist in producing milk.
3) The act of giving birth is called ________.
4) After the egg is fertilized, it is called a(n) ________.
5) The ________ cells of the blastocyst will take part in placental formation.
6) The ________ stage of development is the first in which all three germ layers of tissue are evident.
7) ________ is a tissue with star-shaped cells that are free to migrate widely throughout the embryo.
8) Neural tissue develops from the ________.
Answer: syncytial trophoblast cells
9) Which cells invade the endometrium, digesting the uterine cells they contact, so that implantation of the blastocyst can occur?
10) What embryonic structure is the structural base for the umbilical cord?
Answer: A buildup of carbon dioxide in the baby’s blood once the carbon dioxide is not being removed by the placenta causes acidosis. This excites respiratory control centers in the baby’s brain and triggers the first inspiration.
11) Explain what triggers a baby’s first breath.
12) The first axial support for the embryo is called the ________.
Answer: The placenta is fully formed and functional as a nutritive, respiratory, excretory, and endocrine organ by the end of the third month of pregnancy.
13) At what time in the pregnancy is the placenta fully prepared to fulfill the needs of the developing fetus?
Answer: The blastocyst floats freely in the uterine cavity for three or four days, during which time it is nourished by uterine secretions. Six days after ovulation, implantation begins. The trophoblast determines the readiness of the endometrium for implantation. If the mucosa is prepared for implantation, the blastocyst becomes embedded high in the uterus.
14) Briefly describe the events leading to the implantation of the blastocyst in the uterus, including how it is nourished.
Answer: Initially, the implanted embryo obtains nutrition by digesting the endometrial cells, but by the second month, the placenta is providing all the nourishment and oxygen the embryo requires. The placenta is also responsible for disposing of embryonic metabolic wastes.
15) How are the metabolic needs of the implanted embryo provided for?
Answer: After sperm penetration, the oocyte completes meiosis II and releases the second polar body. The two nuclei swell into pronuclei and join each other to form a zygote. The cell then undergoes its first mitosis and cell division to form two daughter cells.
16) Describe the events of the oocyte from sperm penetration to first cleavage.
Answer: Braxton-Hicks contractions are the weak, irregular uterine contractions resulting from the increase in estrogen production. Estrogen causes oxytocin receptors to form on the myometrial cells of the uterus and antagonizes progesterone's quieting influence on the uterine muscle. As a result, the myometrium becomes increasingly irritable, resulting in weak, irregular contractions.
17) Define Braxton-Hicks contractions.
Answer: Four factors that help to precipitate parturition include: (1) estrogen peaks to its highest levels in the mother's blood, causing irregular uterine contractions due to oxytocin and negation of progesterone's influence on the uterine muscle; (2) prostaglandins are stimulated by the increase in oxytocin to act as uterine muscle stimulants; (3) increasing emotional and physical stressors activate the mother’s hypothalamus, which signals oxytocin release; and (4) certain cells of the fetus begin to produce oxytocin, which in turn acts on the placenta, stimulating production and release of prostaglandins.
18) List four factors that help to precipitate parturition.
Answer: Many women suffer nausea until their systems become adjusted to elevated levels of estrogen and progesterone. Heartburn is common due to displacement of the esophagus and crowding of the stomach by the growing fetus in the uterus. Additional wastes from fetal metabolism cause the production of more urine. Due to pressure on the bladder by the uterus, urination is more frequent. Tidal volume increases during pregnancy, as does respiratory rate. Residual volume decreases and many women exhibit dyspnea. Total body water rises, acting as a safeguard against blood loss during birth. Blood volume increases, blood pressure and pulse rise, and cardiac output increases.
19) Briefly describe the physiological changes occurring in the mother during pregnancy.
Answer: A sperm entering the oocyte causes ionic calcium to be released into the oocyte cytoplasm, activating the oocyte and preparing it for cell division. This also causes the cortical granules to spill their contents into the extracellular space beneath the zona pellucida. Enzymes from the cortical granulus destroy sperm receptors, preventing further sperm entry. This spilled material binds with water, and as it swells, detaches all sperm still in contact with the oocyte membrane.
20) Describe the events allowing monospermy.
Answer: We begin to call the developing individual a fetus at the beginning of the ninth week.
21) When do we begin to call the developing individual a fetus rather than an embryo?
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