Module 28: Development and Inheritance

Lesson 4: Physiological Changes in Pregnancy

Thay Đổi Sinh Lý Trong Thai Kỳ

Nội dung bài học:
Mỗi bài học (lesson) bao gồm 4 phần chính: Thuật ngữ, Luyện Đọc, Luyện Nghe, và Bàn Luận.
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Dưới đây là danh sách những thuật ngữ Y khoa của module Development and Inheritance.
Khái quát được số lượng thuật ngữ sẽ xuất hiện trong bài đọc và nghe sẽ giúp bạn thoải mái tiêu thụ nội dung hơn. Sau khi hoàn thành nội dung đọc và nghe, bạn hãy quay lại đây và luyện tập (practice) để quen dần các thuật ngữ này. Đừng ép bản thân phải nhớ các thuật ngữ này vội vì bạn sẽ gặp và ôn lại danh sách này trong những bài học (lesson) khác của cùng một module.

Medical Terminology: Development and Inheritance

acrosomal reaction
release of digestive enzymes by sperm that enables them to burrow through the corona radiata and penetrate the zona pellucida of an oocyte prior to fertilization
cap-like vesicle located at the anterior-most region of a sperm that is rich with lysosomal enzymes capable of digesting the protective layers surrounding the oocyte
third stage of childbirth in which the placenta and associated fetal membranes are expelled
finger-like outpocketing of yolk sac forms the primitive excretory duct of the embryo; precursor to the urinary bladder
alternative forms of a gene that occupy a specific locus on a specific gene
transparent membranous sac that encloses the developing fetus and fills with amniotic fluid
amniotic cavity
cavity that opens up between the inner cell mass and the trophoblast; develops into amnion
autosomal chromosome
in humans, the 22 pairs of chromosomes that are not the sex chromosomes (XX or XY)
autosomal dominant
pattern of dominant inheritance that corresponds to a gene on one of the 22 autosomal chromosomes
autosomal recessive
pattern of recessive inheritance that corresponds to a gene on one of the 22 autosomal chromosomes
fluid-filled cavity of the blastocyst
term for the conceptus at the developmental stage that consists of about 100 cells shaped into an inner cell mass that is fated to become the embryo and an outer trophoblast that is fated to become the associated fetal membranes and placenta
daughter cell of a cleavage
Braxton Hicks contractions
weak and irregular peristaltic contractions that can occur in the second and third trimesters; they do not indicate that childbirth is imminent
brown adipose tissue
highly vascularized fat tissue that is packed with mitochondria; these properties confer the ability to oxidize fatty acids to generate heat
process that occurs in the female reproductive tract in which sperm are prepared for fertilization; leads to increased motility and changes in their outer membrane that improve their ability to release enzymes capable of digesting an oocyte’s outer layers
heterozygous individual who does not display symptoms of a recessive genetic disorder but can transmit the disorder to their offspring
membrane that develops from the syncytiotrophoblast, cytotrophoblast, and mesoderm; surrounds the embryo and forms the fetal portion of the placenta through the chorionic villi
chorionic membrane
precursor to the chorion; forms from extra-embryonic mesoderm cells
chorionic villi
projections of the chorionic membrane that burrow into the endometrium and develop into the placenta
form of mitotic cell division in which the cell divides but the total volume remains unchanged; this process serves to produce smaller and smaller cells
pattern of inheritance that corresponds to the equal, distinct, and simultaneous expression of two different alleles
thick, yellowish substance secreted from a mother’s breasts in the first postpartum days; rich in immunoglobulins
pre-implantation stage of a fertilized egg and its associated membranes
corona radiata
in an oocyte, a layer of granulosa cells that surrounds the oocyte and that must be penetrated by sperm before fertilization can occur
cortical reaction
following fertilization, the release of cortical granules from the oocyte’s plasma membrane into the zona pellucida creating a fertilization membrane that prevents any further attachment or penetration of sperm; part of the slow block to polyspermy
first stage of childbirth, involving an increase in cervical diameter
describes a trait that is expressed both in homozygous and heterozygous form
dominant lethal
inheritance pattern in which individuals with one or two copies of a lethal allele do not survive in utero or have a shortened life span
ductus arteriosus
shunt in the pulmonary trunk that diverts oxygenated blood back to the aorta
ductus venosus
shunt that causes oxygenated blood to bypass the fetal liver on its way to the inferior vena cava
primary germ layer that develops into the central and peripheral nervous systems, sensory organs, epidermis, hair, and nails
ectopic pregnancy
implantation of an embryo outside of the uterus
developing human during weeks 3–8
embryonic folding
process by which an embryo develops from a flat disc of cells to a three-dimensional shape resembling a cylinder
primary germ layer that goes on to form the gastrointestinal tract, liver, pancreas, and lungs
upper layer of cells of the embryonic disc that forms from the inner cell mass; gives rise to all three germ layers
incision made in the posterior vaginal wall and perineum that facilitates vaginal birth
second stage of childbirth, during which the mother bears down with contractions; this stage ends in birth
unification of genetic material from male and female haploid gametes
fertilization membrane
impenetrable barrier that coats a nascent zygote; part of the slow block to polyspermy
developing human during the time from the end of the embryonic period (week 9) to birth
foramen ovale
shunt that directly connects the right and left atria and helps divert oxygenated blood from the fetal pulmonary circuit
watery, translucent breast milk that is secreted first during a feeding and is rich in lactose and protein; quenches the infant’s thirst
process of cell migration and differentiation into three primary germ layers following cleavage and implantation
complete genetic makeup of an individual
in human development, the period required for embryonic and fetal development in utero; pregnancy
having two different alleles for a given gene
opaque, creamy breast milk delivered toward the end of a feeding; rich in fat; satisfies the infant’s appetite
having two identical alleles for a given gene
human chorionic gonadotropin (hCG)
hormone that directs the corpus luteum to survive, enlarge, and continue producing progesterone and estrogen to suppress menses and secure an environment suitable for the developing embryo
lower layer of cells of the embryonic disc that extend into the blastocoel to form the yolk sac
process by which a blastocyst embeds itself in the uterine endometrium
incomplete dominance
pattern of inheritance in which a heterozygous genotype expresses a phenotype intermediate between dominant and recessive phenotypes
inner cell mass
cluster of cells within the blastocyst that is fated to become the embryo
postpartum shrinkage of the uterus back to its pre-pregnancy volume
systematic arrangement of images of chromosomes into homologous pairs
process by which milk is synthesized and secreted from the mammary glands of the postpartum female breast in response to sucking at the nipple
silk-like hairs that coat the fetus; shed later in fetal development
let-down reflex
release of milk from the alveoli triggered by infant suckling
descent of the fetus lower into the pelvis in late pregnancy; also called “dropping”
postpartum vaginal discharge that begins as blood and ends as a whitish discharge; the end of lochia signals that the site of placental attachment has healed
fetal wastes consisting of ingested amniotic fluid, cellular debris, mucus, and bile
primary germ layer that becomes the skeleton, muscles, connective tissue, heart, blood vessels, and kidneys
tightly packed sphere of blastomeres that has reached the uterus but has not yet implanted itself
change in the nucleotide sequence of DNA
neural fold
elevated edge of the neural groove
neural plate
thickened layer of neuroepithelium that runs longitudinally along the dorsal surface of an embryo and gives rise to nervous system tissue
neural tube
precursor to structures of the central nervous system, formed by the invagination and separation of neuroepithelium
embryonic process that establishes the central nervous system
nonshivering thermogenesis
process of breaking down brown adipose tissue to produce heat in the absence of a shivering response
rod-shaped, mesoderm-derived structure that provides support for growing fetus
development of the rudimentary structures of all of an embryo’s organs from the germ layers
physical or biochemical manifestation of the genotype; expression of the alleles
organ that forms during pregnancy to nourish the developing fetus; also regulates waste and gas exchange between mother and fetus
placenta previa
low placement of fetus within uterus causes placenta to partially or completely cover the opening of the cervix as it grows
formation of the placenta; complete by weeks 14–16 of pregnancy
penetration of an oocyte by more than one sperm
primitive streak
indentation along the dorsal surface of the epiblast through which cells migrate to form the endoderm and mesoderm during gastrulation
pituitary hormone that establishes and maintains the supply of breast milk; also important for the mobilization of maternal micronutrients for breast milk
Punnett square
grid used to display all possible combinations of alleles transmitted by parents to offspring and predict the mathematical probability of offspring inheriting a given genotype
fetal movements that are strong enough to be felt by the mother
describes a trait that is only expressed in homozygous form and is masked in heterozygous form
recessive lethal
inheritance pattern in which individuals with two copies of a lethal allele do not survive in utero or have a shortened life span
sex chromosomes
pair of chromosomes involved in sex determination; in males, the XY chromosomes; in females, the XX chromosomes
circulatory shortcut that diverts the flow of blood from one region to another
one of the paired, repeating blocks of tissue located on either side of the notochord in the early embryo
superficial cells of the trophoblast that fuse to form a multinucleated body that digests endometrial cells to firmly secure the blastocyst to the uterine wall
variation of an expressed characteristic
division of the duration of a pregnancy into three 3-month terms
fluid-filled shell of squamous cells destined to become the chorionic villi, placenta, and associated fetal membranes
true labor
regular contractions that immediately precede childbirth; they do not abate with hydration or rest, and they become more frequent and powerful with time
umbilical cord
connection between the developing conceptus and the placenta; carries deoxygenated blood and wastes from the fetus and returns nutrients and oxygen from the mother
vernix caseosa
waxy, cheese-like substance that protects the delicate fetal skin until birth
pattern of inheritance in which an allele is carried on the X chromosome of the 23rd pair
X-linked dominant
pattern of dominant inheritance that corresponds to a gene on the X chromosome of the 23rd pair
X-linked recessive
pattern of recessive inheritance that corresponds to a gene on the X chromosome of the 23rd pair
yolk sac
membrane associated with primitive circulation to the developing embryo; source of the first blood cells and germ cells and contributes to the umbilical cord structure
zona pellucida
thick, gel-like glycoprotein membrane that coats the oocyte and must be penetrated by sperm before fertilization can occur
fertilized egg; a diploid cell resulting from the fertilization of haploid gametes from the male and female lines
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Dưới đây là các bài văn nằm ở bên trái. Ở bên phải là các bài luyện tập (practice) để đánh giá khả năng đọc hiểu của bạn. Sẽ khó khăn trong thời gian đầu nếu vốn từ vựng của bạn còn hạn chế, đặc biệt là từ vựng Y khoa. Hãy kiên nhẫn và đọc nhiều nhất có kể, lượng kiến thức tích tụ dần sẽ giúp bạn đọc thoải mái hơn.
A full-term pregnancy lasts approximately 270 days (approximately 38.5 weeks) from conception to birth. Because it is easier to remember the first day of the last menstrual period (LMP) than to estimate the date of conception, obstetricians set the due date as 284 days (approximately 40.5 weeks) from the LMP. This assumes that conception occurred on day 14 of the menstrual cycle, which is usually a good approximation. The 40 weeks of an average pregnancy are usually discussed in terms of three trimesters, each approximately 13 weeks. During the second and third trimesters, the pre-pregnancy uterus—about the size of a fist—grows dramatically to contain the fetus, causing a number of anatomical changes in the pregnant person (Figure 1).
Virtually all of the effects of pregnancy can be attributed in some way to the influence of hormones—particularly estrogens, progesterone, and hCG. During weeks 7–12 from the LMP, the pregnancy hormones are primarily generated by the corpus luteum. Progesterone secreted by the corpus luteum stimulates the production of decidual cells of the endometrium that nourish the blastocyst before placentation. As the placenta develops and the corpus luteum degenerates during weeks 12–17, the placenta gradually takes over as the endocrine organ of pregnancy.

The placenta converts weak androgens secreted by the maternal and fetal adrenal glands to estrogens, which are necessary for pregnancy to progress. Estrogen levels climb throughout the pregnancy, increasing 30-fold by childbirth. Estrogens have the following actions:

  • They suppress FSH and LH production, effectively preventing ovulation. (This function is the biological basis of hormonal birth control pills.)
  • They induce the growth of fetal tissues and are necessary for the maturation of the fetal lungs and liver.
  • They promote fetal viability by regulating progesterone production and triggering fetal synthesis of cortisol, which helps with the maturation of the lungs, liver, and endocrine organs such as the thyroid gland and adrenal gland.
  • They stimulate maternal tissue growth, leading to uterine enlargement and mammary duct expansion and branching.

Relaxin, another hormone secreted by the corpus luteum and then by the placenta, helps prepare the body for childbirth. It increases the elasticity of the symphysis pubis joint and pelvic ligaments, making room for the growing fetus and allowing expansion of the pelvic outlet for childbirth. Relaxin also helps dilate the cervix during labor.

The placenta takes over the synthesis and secretion of progesterone throughout pregnancy as the corpus luteum degenerates. Like estrogen, progesterone suppresses FSH and LH. It also inhibits uterine contractions, protecting the fetus from preterm birth. This hormone decreases in late gestation, allowing uterine contractions to intensify and eventually progress to true labor. The placenta also produces hCG. In addition to promoting survival of the corpus luteum, hCG stimulates the male fetal gonads to secrete testosterone, which is essential for the development of the male reproductive system.

The anterior pituitary enlarges and ramps up its hormone production during pregnancy, raising the levels of thyrotropin, prolactin, and adrenocorticotropic hormone (ACTH). Thyrotropin, in conjunction with placental hormones, increases the production of thyroid hormone, which raises the maternal metabolic rate. This can markedly augment a pregnant person’s appetite and cause hot flashes. Prolactin stimulates enlargement of the mammary glands in preparation for milk production. ACTH stimulates maternal cortisol secretion, which contributes to fetal protein synthesis. In addition to the pituitary hormones, increased parathyroid levels mobilize calcium from maternal bones for fetal use.
The second and third trimesters of pregnancy are associated with dramatic changes in maternal anatomy and physiology. The most obvious anatomical sign of pregnancy is the dramatic enlargement of the abdominal region, coupled with weight gain. This weight results from the growing fetus as well as the enlarged uterus, amniotic fluid, and placenta. Additional breast tissue and dramatically increased blood volume also contribute to weight gain (Table 1). Surprisingly, fat storage accounts for only approximately 2.3 kg (5 lbs) in a normal pregnancy and serves as a reserve for the increased metabolic demand of breastfeeding.

During the first trimester, a pregnant person does not need to consume additional calories to maintain a healthy pregnancy. However, a weight gain of approximately 0.45 kg (1 lb) per month is common. During the second and third trimesters, the appetite increases, but it is only necessary to consume an additional 300 calories per day to support the growing fetus. Most pregnant people gain approximately 0.45 kg (1 lb) per week.
As the body adapts to pregnancy, characteristic physiologic changes occur. These changes can sometimes prompt symptoms often referred to collectively as the common discomforts of pregnancy.

A. Digestive and Urinary System Changes

Nausea and vomiting, sometimes triggered by an increased sensitivity to odors, are common during the first few weeks to months of pregnancy. This phenomenon is often referred to as “morning sickness,” although the nausea may persist all day. The source of pregnancy nausea is thought to be the increased circulation of pregnancy-related hormones, specifically circulating estrogen, progesterone, and hCG. Decreased intestinal peristalsis may also contribute to nausea. By about week 12 of pregnancy, nausea typically subsides.

A common gastrointestinal complaint during the later stages of pregnancy is gastric reflux, or heartburn, which results from the upward, constrictive pressure of the growing uterus on the stomach. The same decreased peristalsis that may contribute to nausea in early pregnancy is also thought to be responsible for pregnancy-related constipation as pregnancy progresses.

The downward pressure of the uterus also compresses the urinary bladder, leading to frequent urination. The problem is exacerbated by increased urine production. In addition, the maternal urinary system processes both maternal and fetal wastes, further increasing the total volume of urine.

B. Circulatory System Changes

Blood volume increases substantially during pregnancy, so that by childbirth, it exceeds its preconception volume by 30 percent, or approximately 1–2 liters. The greater blood volume helps to manage the demands of fetal nourishment and fetal waste removal. In conjunction with increased blood volume, the pulse and blood pressure also rise moderately during pregnancy. As the fetus grows, the uterus compresses underlying pelvic blood vessels, hampering venous return from the legs and pelvic region. As a result, many pregnant people develop varicose veins or hemorrhoids.

C. Respiratory System Changes

During the second half of pregnancy, the respiratory minute volume (volume of gas inhaled or exhaled by the lungs per minute) increases by 50 percent to compensate for the oxygen demands of the fetus and the increased maternal metabolic rate. The growing uterus exerts upward pressure on the diaphragm, decreasing the volume of each inspiration and potentially causing shortness of breath, or dyspnea. During the last several weeks of pregnancy, the pelvis becomes more elastic, and the fetus descends lower in a process called lightening. This typically ameliorates dyspnea.

The respiratory mucosa swell in response to increased blood flow during pregnancy, leading to nasal congestion and nose bleeds, particularly when the weather is cold and dry. Humidifier use and increased fluid intake are often recommended to counteract congestion.

D. Integumentary System Changes

The dermis stretches extensively to accommodate the growing uterus, breast tissue, and fat deposits on the thighs and hips. Torn connective tissue beneath the dermis can cause striae (stretch marks) on the abdomen, which appear as red or purple marks during pregnancy that fade to a silvery white color in the months after childbirth.

An increase in melanocyte-stimulating hormone, in conjunction with estrogens, darkens the areolae and creates a line of pigment from the umbilicus to the pubis called the linea nigra (Figure 2). Melanin production during pregnancy may also darken or discolor skin on the face to create a chloasma, or “mask of pregnancy.”

OpenStax. (2022). Anatomy and Physiology 2e. Rice University. Retrieved June 15, 2023. ISBN-13: 978-1-711494-06-7 (Hardcover) ISBN-13: 978-1-711494-05-0 (Paperback) ISBN-13: 978-1-951693-42-8 (Digital). License: Attribution 4.0 International (CC BY 4.0). Access for free at

The uterus grows throughout pregnancy to accommodate the fetus.

The linea nigra, a dark medial line running from the umbilicus to the pubis, forms during pregnancy and persists for a few weeks following childbirth. The linea nigra shown here corresponds to a pregnancy that is 22 weeks along.

ComponentWeight (kg)Weight (lb)
Placenta and fetal membranes0.9–1.82–4
Amniotic fluid0.9–1.42–3
Breast tissue0.9–1.42–3
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Dưới đây là video và các luyện tập (practice) của bài này. Nghe là một kĩ năng khó, đặc biệt là khi chúng ta chưa quen nội dung và chưa có nhạy cảm ngôn ngữ. Nhưng cứ đi thật chậm và đừng bỏ cuộc.
Xem video và cảm nhận nội dung bài. Bạn có thể thả trôi, cảm nhận dòng chảy ngôn ngữ và không nhất thiết phải hiểu toàn bộ bài. Bên dưới là script để bạn khái quát nội dụng và tra từ mới.
  1. Hormones (especially estrogens, progesterone, and hCG) secreted by the corpus luteum and later by the placenta are responsible for most of the changes experienced during pregnancy.
  2. Estrogen maintains the pregnancy, promotes fetal viability, and stimulates tissue growth in the mother and developing fetus.
  3. Progesterone prevents new ovarian follicles from developing and suppresses uterine contractility.
  4. Pregnancy weight gain primarily occurs in the breasts and abdominal region.
  5. Nausea, heartburn, and frequent urination are common during pregnancy.
  6. Maternal blood volume increases by 30 percent during pregnancy and respiratory minute volume increases by 50 percent.
  7. The skin may develop stretch marks and melanin production may increase.
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