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?

Estrogen and Progesterone Signup and view all the answers

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

To transport milk from the ampulla to the outside Signup and view all the answers

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

Facilitates the sperm cell's penetration through the zona pellucida Signup and view all the answers

What initiates the acrosomal reaction in the sperm cell?

Binding to the zona pellucida Signup and view all the answers

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

Reaction of the cortical granules Signup and view all the answers

What is the result of the cortical reaction during fertilization?

Prevention of polyspermy Signup and view all the answers

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

Completion of fertilization Signup and view all the answers

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

Morula Signup and view all the answers

What characterizes a blastocyst during its development?

It has an inner cell mass and a fluid-filled cavity Signup and view all the answers

What process occurs first during the invasion of the syncytiotrophoblast?

It invades the endometrial veins. Signup and view all the answers

Which of the following best describes the primary chorionic villi?

They arise from the proliferation of cytotrophoblast cells. Signup and view all the answers

What is the fate of the secondary chorionic villus?

It becomes a tertiary chorionic villus. Signup and view all the answers

How do the lacunae contribute to placental function?

They house maternal blood and assist in nutrient transfer. Signup and view all the answers

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

Waste products flow from the fetus to maternal blood. Signup and view all the answers

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

They invade the villus to form fetal capillaries. Signup and view all the answers

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

It facilitates the exchange of carbon dioxide for oxygen. Signup and view all the answers

What occurs after the primary chorionic villi formation?

They continue to grow and develop into secondary villi. Signup and view all the answers

Which function of the placenta is crucial for fetal nutrition?

Direct transfer of nutrients via blood. Signup and view all the answers

What is the primary role of hCG in early pregnancy?

To maintain the corpus luteum Signup and view all the answers

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

Between weeks 7 and 9 of gestation Signup and view all the answers

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

Estriol Signup and view all the answers

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

17α-Hydroxylase Signup and view all the answers

Why is the placenta considered an imperfect endocrine organ?

It lacks cholesterol synthesis capabilities Signup and view all the answers

What is the role of progesterone in pregnancy?

Reduces uterine contractility Signup and view all the answers

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

Maternal-placental-fetal unit Signup and view all the answers

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

Impaired hormone synthesis Signup and view all the answers

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

Progesterone Signup and view all the answers

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

It requires collaboration between the mother and fetus Signup and view all the answers

What is the primary role of progesterone during pregnancy?

To maintain uterine quiescence and decrease smooth muscle contractility Signup and view all the answers

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

400 to 800 μg/day Signup and view all the answers

During which stage of labor does active labor occur?

Stage 2 Signup and view all the answers

How does estriol affect the synthesis of progesterone during childbirth?

It inhibits the synthesis of progesterone by the placenta Signup and view all the answers

What is the primary function of relaxin during pregnancy?

To maintain uterine quiescence and aid in tissue remodeling Signup and view all the answers

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

Less than one third of the total maternal weight gain represents the fetus. Signup and view all the answers

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

Progesterone, oxytocin, relaxin, and prostaglandins Signup and view all the answers

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

There is an effective withdrawal of progesterone function Signup and view all the answers

What occurs during Stage 0 of labor?

Uterine tranquility and refractoriness to contraction Signup and view all the answers

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

Promoting cervical ripening and increasing uterine contractions Signup and view all the answers

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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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.