L14. Physiology - Pregnancy & Parturition
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Questions and Answers

Which hormone is responsible for stimulating uterine contractions and has a self-perpetuating effect during childbirth?

  • Human placental lactogen
  • Oxytocin (correct)
  • Prolactin
  • Estrogen

What is the primary role of myoepithelial cells in the context of lactation?

  • To enhance the absorption of lactose
  • To stimulate milk ejection (correct)
  • To secrete milk proteins
  • To regulate hormonal levels in the breast

Which of the following components is NOT typically found in human milk?

  • Human chorionic somatomammotropin (correct)
  • Lactalbumin
  • Cholesterol
  • Lactose

During pregnancy, which two hormones primarily contribute to the full development of the breasts?

<p>Estrogen and Progesterone (C)</p> Signup and view all the answers

What is the function of the lactiferous duct in the lactation process?

<p>To transport milk from the ampulla to the outside (A)</p> Signup and view all the answers

What is the function of zona pellucida 3 (ZP3) in fertilization?

<p>Facilitates the sperm cell's penetration through the zona pellucida (B)</p> Signup and view all the answers

What initiates the acrosomal reaction in the sperm cell?

<p>Binding to the zona pellucida (A)</p> Signup and view all the answers

Which biological event occurs following the rise in intracellular calcium levels in the oocyte?

<p>Reaction of the cortical granules (A)</p> Signup and view all the answers

What is the result of the cortical reaction during fertilization?

<p>Prevention of polyspermy (A)</p> Signup and view all the answers

What occurs immediately after the fusion of male and female pronuclei?

<p>Completion of fertilization (D)</p> Signup and view all the answers

Which structure forms from the zygote during its transit to the uterine cavity?

<p>Morula (A)</p> Signup and view all the answers

What characterizes a blastocyst during its development?

<p>It has an inner cell mass and a fluid-filled cavity (D)</p> Signup and view all the answers

What process occurs first during the invasion of the syncytiotrophoblast?

<p>It invades the endometrial veins. (C)</p> Signup and view all the answers

Which of the following best describes the primary chorionic villi?

<p>They arise from the proliferation of cytotrophoblast cells. (D)</p> Signup and view all the answers

What is the fate of the secondary chorionic villus?

<p>It becomes a tertiary chorionic villus. (D)</p> Signup and view all the answers

How do the lacunae contribute to placental function?

<p>They house maternal blood and assist in nutrient transfer. (B)</p> Signup and view all the answers

Which statement accurately reflects the interaction between maternal and fetal systems at the placenta?

<p>Waste products flow from the fetus to maternal blood. (C)</p> Signup and view all the answers

What is the significance of mesenchymal cells in the development of the chorionic villus?

<p>They invade the villus to form fetal capillaries. (D)</p> Signup and view all the answers

What major role does the placenta serve with respect to gas exchange between the mother and fetus?

<p>It facilitates the exchange of carbon dioxide for oxygen. (B)</p> Signup and view all the answers

What occurs after the primary chorionic villi formation?

<p>They continue to grow and develop into secondary villi. (D)</p> Signup and view all the answers

Which function of the placenta is crucial for fetal nutrition?

<p>Direct transfer of nutrients via blood. (D)</p> Signup and view all the answers

What is the primary role of hCG in early pregnancy?

<p>To maintain the corpus luteum (D)</p> Signup and view all the answers

At what point does the luteal-placental shift occur during pregnancy?

<p>Between weeks 7 and 9 of gestation (C)</p> Signup and view all the answers

What hormone is predominantly produced by the placenta during pregnancy, especially in late gestation?

<p>Estriol (D)</p> Signup and view all the answers

Which enzyme deficiency contributes to the placenta's inability to synthesize certain estrogens?

<p>17α-Hydroxylase (C)</p> Signup and view all the answers

Why is the placenta considered an imperfect endocrine organ?

<p>It lacks cholesterol synthesis capabilities (B)</p> Signup and view all the answers

What is the role of progesterone in pregnancy?

<p>Reduces uterine contractility (A)</p> Signup and view all the answers

What concept describes the collaborative synthesis of hormones between the mother, placenta, and fetus?

<p>Maternal-placental-fetal unit (B)</p> Signup and view all the answers

What is a significant consequence of the placenta's inability to manufacture adequate cholesterol?

<p>Impaired hormone synthesis (B)</p> Signup and view all the answers

Which hormone primarily prevents the propagation of uterine contractions during pregnancy?

<p>Progesterone (C)</p> Signup and view all the answers

How does the placenta interact with the mother and fetus in steroid biosynthesis?

<p>It requires collaboration between the mother and fetus (A)</p> Signup and view all the answers

What is the primary role of progesterone during pregnancy?

<p>To maintain uterine quiescence and decrease smooth muscle contractility (B)</p> Signup and view all the answers

What is the recommended daily intake of folic acid for effective prophylaxis against neural tube defects during pregnancy?

<p>400 to 800 μg/day (D)</p> Signup and view all the answers

During which stage of labor does active labor occur?

<p>Stage 2 (C)</p> Signup and view all the answers

How does estriol affect the synthesis of progesterone during childbirth?

<p>It inhibits the synthesis of progesterone by the placenta (C)</p> Signup and view all the answers

What is the primary function of relaxin during pregnancy?

<p>To maintain uterine quiescence and aid in tissue remodeling (B)</p> Signup and view all the answers

Which of the following statements about the maternal weight gain during pregnancy is true?

<p>Less than one third of the total maternal weight gain represents the fetus. (D)</p> Signup and view all the answers

Which hormones play a crucial role in the initiation and maintenance of parturition?

<p>Progesterone, oxytocin, relaxin, and prostaglandins (D)</p> Signup and view all the answers

What typically happens to progesterone levels at the onset of labor?

<p>There is an effective withdrawal of progesterone function (B)</p> Signup and view all the answers

What occurs during Stage 0 of labor?

<p>Uterine tranquility and refractoriness to contraction (B)</p> Signup and view all the answers

Which of the following best describes the role of prostaglandins in labor?

<p>Promoting cervical ripening and increasing uterine contractions (A)</p> Signup and view all the answers

Flashcards

What is ZP3?

A protein on the surface of the egg cell (oocyte) that the sperm binds to, initiating the fertilization process.

What is the acrosomal reaction?

The release of enzymes from the sperm's acrosome, which helps the sperm penetrate the zona pellucida.

What is the cortical reaction?

The hardening of the zona pellucida after a sperm successfully enters the egg, preventing other sperm from fertilizing the egg.

What is the process of fertilization?

The process of the sperm nucleus fusing with the egg nucleus to form a single cell called a zygote.

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What is a morula?

A cluster of 16 cells formed by the rapid division (cleavage) of the zygote.

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What is a blastocyst?

A hollow ball of cells formed after the morula stage. It includes an outer layer (trophoblast) and an inner cell mass.

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What is implantation?

The implantation process involves the blastocyst attaching to the lining of the uterus (endometrium) and eventually embedding itself within the uterine wall.

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Syncytiotrophoblast

The outer layer of the developing embryo that invades the uterine wall to establish a connection with maternal blood supply. It forms finger-like projections called villi for nutrient and gas exchange.

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Lacunae

Small spaces within the developing placenta that fill with maternal blood, facilitating nutrient and gas exchange between mother and fetus.

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Invasion of Maternal Vessels

The process by which the syncytiotrophoblast invades uterine blood vessels, establishing a direct connection between maternal blood and the developing placenta.

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Primary Chorionic Villi

The earliest, simplest form of placental villi, consisting only of a core of cytotrophoblast cells.

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Secondary Chorionic Villi

A more complex form of chorionic villi, containing a core of cytotrophoblast cells and a surrounding layer of mesenchyme.

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Tertiary Chorionic Villi

The final stage of chorionic villi development, containing a core of cytotrophoblast cells, mesenchyme, and developing fetal capillaries.

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Intervillous Space

The large, interconnected space within the placenta filled with maternal blood, facilitating nutrient and gas exchange between mother and fetus.

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Placenta

The organ that connects the developing embryo to the uterine wall, facilitating nutrient and gas exchange, waste removal, and hormone production.

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Placental Transfer

The placenta transfers nutrients and oxygen from the mother to the fetus while removing waste products and carbon dioxide.

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Placental Immune Barrier Function

The placenta acts as a protective barrier to maternal immune cells, preventing rejection of the fetus, which is considered a foreign allograft inside the uterus.

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Placental Hormone Production

The placenta produces numerous proteins and steroid hormones to maintain pregnancy viability.

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Human Chorionic Gonadotropin (hCG)

Human chorionic gonadotropin (hCG) is a critical placental hormone produced early in the first trimester by the syncytiotrophoblast.

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hCG's Role in Corpus Luteum Maintenance

hCG maintains the corpus luteum, which is the primary source of progesterone and estrogen in early pregnancy.

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Corpus Luteum Limitations

The corpus luteum alone is inadequate to produce the high steroid levels required for late pregnancy.

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Placental Steroid Production in Late Pregnancy

The placenta takes over progesterone and estrogen production in late pregnancy.

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Luteal-Placental Shift

The shift from ovary to placenta as the main source of progesterone production during pregnancy is known as the luteal-placental shift.

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Pregnancy after Ovary Removal

Pregnancy can continue after the 7th week without the ovaries due to the placenta taking over hormone production.

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Maternal-Placental-Fetal Unit

The concept of the maternal-placental-fetal unit recognizes the interdependent roles of mother, placenta, and fetus in steroid hormone production during pregnancy.

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Placental Limitations in Steroid Synthesis

The placenta requires cholesterol, 17α-hydroxylase, and 17,20-desmolase for steroid hormone production, but it has limitations in producing these components.

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How does oxytocin contribute to labor?

The release of oxytocin during labor is a self-perpetuating cycle, meaning it stimulates uterine contractions, which in turn stretches the cervix, further stimulating oxytocin release.

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What is the galactokinetic effect?

The myoepithelial cells surrounding the alveoli in the breast contract, squeezing milk out of the ducts and into the lactiferous ducts.

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What is prolactin's role in lactation?

Prolactin is a hormone responsible for the production of milk. It acts on the epithelial cells within the alveoli of the breast, stimulating the synthesis of milk components.

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How does human milk composition change?

The composition of human milk changes over time, transitioning from colostrum, a thick, yellowish fluid rich in antibodies, to mature milk, which is thinner and contains more lactose and fats.

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Describe the structure of the mammary gland.

The alveoli are tiny sacs within the breast where milk is produced. Groups of alveoli form lobules, which drain into ducts, ultimately leading to the lactiferous ducts that carry milk to the nipple.

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Recommended weight gain during pregnancy

The amount of weight a woman should gain during pregnancy (for a singleton pregnancy with a normal weight-to-height ratio).

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Progesterone's role in pregnancy

A hormone that helps maintain the uterus in a resting state during pregnancy, preventing contractions.

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Estriol's role in labor

A form of estrogen predominant during childbirth. It inhibits progesterone production and prepares the uterus for labor.

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Oxytocin's role in labor

A hormone that stimulates uterine contractions during labor, helping the baby to be born.

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Relaxin's role in labor

A hormone that relaxes the pelvic ligaments and softens the cervix, making childbirth easier.

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Prostaglandins' role in labor

Hormones that contribute to uterine contractions during labor, helping to dilate the cervix and move the baby down the birth canal.

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Stage 1 of labor

The first stage of labor, characterized by the onset of regular contractions and cervical dilation.

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Stage 2 of labor

The second stage of labor, which starts when the cervix is fully dilated and ends with the birth of the baby.

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Stage 3 of labor

The third stage of labor, during which the placenta is delivered.

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Stage 0 of labor

The period of time prior to the onset of labor, when the uterus is quiet and not contracting regularly.

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Study Notes

Pregnancy and Parturition Learning Objectives

  • Fertilization occurs when sperm penetrates the zona pellucida, the outer layer surrounding the oocyte.
  • Sperm undergo capacitation in the female reproductive tract.
  • A small number of sperm (50-100) reach the fallopian tube for fertilization.
  • Post-ovulation, the cumulus oocyte is moved to the uterus by smooth muscle and cilia.
  • Fertilization concludes with the fusion of male and female pronuclei to form a zygote.

Implantation

  • The zygote rapidly divides into a morula.
  • The morula transforms into a blastocyst.
  • The blastocyst implants in the uterine lining.
  • Implantation involves three stages: apposition, adhesion, and invasion
  • Apposition is initial contact between the trophoblast of the blastocyst and the uterine wall, typically in a crypt of the endometrium.
  • Adhesion occurs when the blastocyst attaches to the uterine wall.
  • Invasion occurs when the trophoblast invades the endometrial stroma.
  • The outer layer of a blastocyst is called trophoblast, and proliferates to form cytotrophoblast (inner layer) and syncytiotrophoblast (outer layer).
  • The inner cell mass of blastocyst is called embryoblast.

Placenta Development

  • The syncytiotrophoblast invades the uterine wall establishing utero-placental circulation.
  • The embryoblast forms an embryonic disk (epiblast and hypoblast).
  • Chorionic villi develop from the trophoblast, creating an interface for nutrient and waste exchange between mother and fetus.
  • Maternal blood vessels and the developing fetal capillaries intertwine in the intervillous space.
  • The placenta becomes the main source of progesterone and estrogens in week 7 - 9 of pregnancy.

Placenta Roles and Hormones

  • Transfers nutrients and oxygen from mother to fetus, and waste products in reverse direction.
  • Protects the fetus from maternal immune cells.
  • Secretes hormones to support pregnancy.
  • Human chorionic gonadotropin (hCG) maintains the corpus luteum, which produces progesterone and estrogen.
  • Placenta produces estrogen, progesterone, and other hormones throughout gestation.

Maternal-Placental-Fetal Unit

  • The maternal-placental-fetal unit (MPFU): A cooperative unit of mother, placenta, and fetus for steroid biosynthesis; cannot manufacture cholesterol; precursor of steroids.

Maternal Response to Pregnancy

  • Blood volume increases significantly.
  • Cardiac output increases.
  • Maternal needs for protein, iron, and folic acid increase, as do dietary demands for these elements.

Initiation and Maintenance of Parturition

  • Progesterone normally maintains a quiescent state of the uterus.
  • Parturition involves uterine contractions facilitating dilation of cervix and delivery, assisted by relaxin and prostaglandins
  • Progesterone's levels decrease as labor progresses.
  • Oxytocin and prostaglandins increase uterine contractions.

Lactation

  • Alveoli are the functional units of breasts, producing milk.
  • Milk production relies on hormonal regulation.
  • Suckling stimulates sensory neurons and releases prolactin and oxytocin.
  • Prolactin promotes milk production, while oxytocin causes milk ejection.

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Pregnancy & Parturition Lecture Notes 2024-25 PDF

Description

Test your knowledge on human reproductive physiology with questions covering hormones, lactation, fertilization, and embryonic development. This quiz challenges your understanding of key biological processes involved in childbirth and lactation.

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