Early Nutrition and Function of the Placenta

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Questions and Answers

What primarily causes cramping pain in early labor?

Hormonal changes in the pituitary gland

Uterine muscle relaxation

Compression of blood vessels in the uterus (correct)

Tearing of perineal tissues

Which factor contributes to the involution of the uterus after parturition?

High levels of pituitary gonadotropin

Increase in ovarian hormone secretion

Autolysis of the placental site (correct)

Retention of placental tissue

What initiates the more severe pain experienced during the later stages of labor?

Hypoxia of placental tissues

Contraction of smooth muscles around blood vessels

Cervical and perineal stretching (correct)

Uterine muscle spasms

Which hormone is primarily responsible for the development of mammary gland tissue during pregnancy?

Estrogen Signup and view all the answers

What is the nature of the vaginal discharge known as 'lochia' after delivery?

Starts as bloody and then transitions to serous Signup and view all the answers

What is the primary function of the placenta during early pregnancy?

Facilitating diffusion of foodstuffs and oxygen from maternal blood to fetal blood Signup and view all the answers

Which cells are responsible for the initial nutrient source for the embryo after implantation?

Decidual cells Signup and view all the answers

When does the placenta start to provide nutrients to the embryo?

About 16 days after fertilization Signup and view all the answers

What major development occurs in the placenta to ensure nutrient transfer?

Development of maternal blood sinuses surrounding trophoblastic cords Signup and view all the answers

What is the nature of the decidua in relation to embryo nutrition?

Temporary source of nutrients for the embryo Signup and view all the answers

What limits the transport of substances through the placenta in early pregnancy?

Undeveloped placental membrane with low permeability Signup and view all the answers

What components make up the placenta?

Fetal components and maternal components Signup and view all the answers

How do nutrients typically pass through the placental membrane?

Diffusion Signup and view all the answers

What hormone is primarily responsible for promoting the release of free fatty acids for energy in the mother during pregnancy?

Glucocorticoids Signup and view all the answers

Which hormone's secretion is suppressed due to feedback inhibition from placental estrogen and progesterone?

FSH Signup and view all the answers

What physiological change is caused by increased secretion of aldosterone during pregnancy?

Fluid retention and hypertension Signup and view all the answers

The enlargement of which gland contributes to the increased production of thyroxine during pregnancy?

Thyroid gland Signup and view all the answers

What is the primary role of relaxin during pregnancy?

To relax ligaments and soften the cervix Signup and view all the answers

What is the expected weight gain range for a pregnant woman?

25 to 35 pounds Signup and view all the answers

During pregnancy, which of the following changes happens to the parathyroid gland?

Enlargement and increased calcium absorption Signup and view all the answers

What is a significant metabolic change in the mother due to increased metabolic load during pregnancy?

Increased basal metabolic rate Signup and view all the answers

Which hormone is primarily responsible for the synthesis and production of milk during lactation?

Prolactin Signup and view all the answers

What role does progesterone play in lactation?

Required for full development of the lobule-alveolar system Signup and view all the answers

What is the function of colostrum in mammalian lactation?

Provides antibodies to protect the newborn Signup and view all the answers

What happens to the levels of estrogen and progesterone immediately after birth?

They decrease significantly Signup and view all the answers

What triggers the surge in prolactin secretion during breastfeeding?

Sensory signals from the baby’s suckling Signup and view all the answers

Which hormones inhibit milk secretion during pregnancy?

Estrogen and progesterone Signup and view all the answers

Which hormones play a role in the growth of the ductal system in the mammary glands?

Growth hormone, prolactin, adrenal glucocorticoids, and insulin Signup and view all the answers

In nursing mothers, when does the ovarian cycle typically resume?

A few weeks after cessation of nursing Signup and view all the answers

What characterizes eclampsia?

Clonic seizures in the mother Signup and view all the answers

Which of the following is a common management step for eclampsia?

Vasodilating drugs followed by termination of pregnancy Signup and view all the answers

What hormonal change occurs near term to increase uterine excitability?

Increase in estrogen-to-progesterone ratio Signup and view all the answers

What role does oxytocin play during labor?

It increases the number of oxytocin receptors in the uterus Signup and view all the answers

What is a mechanical factor that enhances uterine contractility?

Stretch or irritation of the cervix Signup and view all the answers

Why do twins typically arrive earlier than single births?

The increased stretch of uterine musculature Signup and view all the answers

Which statement about hormonal factors increasing uterine contractility is false?

Higher levels of progesterone are present before labor Signup and view all the answers

What causes the stretching of the cervix to initiate labor reflexes?

Mechanical stretching or irritation of the cervix Signup and view all the answers

Study Notes

Early Nutrition of the Embryo

Progesterone helps in the conversion of endometrial stromal cells into larger cells, containing nutrients like glycogen, proteins, lipids, and minerals.
These enlarged cells are called Decidual Cells. The mass of these cells is called Decidua.
The first week after implantation, the embryo relies solely on the stored nutrients in Decidual cells. This continues until the 8th week.
After the 16th day after fertilization, the placenta begins to deliver nutrients.

Function of the Placenta

Trophoblastic cords (form villi) attach to the endometrium.
Fetal blood capillaries grow into these cords.
Maternal blood sinuses develop outside the cords.
Villi with fetal blood, are surrounded by sinuses containing maternal blood.
The placenta is a combination of fetal and maternal components.
Nutrients and other substances pass through the placenta mainly by diffusion.

Permeability of the Placenta

The primary role of the placenta is to facilitate the diffusion of food and oxygen from the mother's blood to the fetus, and the diffusion of waste products in the opposite direction.
In early pregnancy, the placental membrane is still underdeveloped, meaning it is thick and has a small surface area.
This makes it less permeable.

Other Hormonal Factors in Pregnancy

Almost all the non-sexual endocrine glands in the mother's system react to pregnancy.
This is due to the increased metabolic load on the mother and the influence of placental hormones on the endocrine glands.
Pituitary Secretion:
- The anterior pituitary enlarges and increases the production of Corticotropin, Thyrotropin, and Prolactin.
- The secretion of FSH and LH is suppressed by the feedback inhibition of placental estrogen and progesterone.
Increased Corticosteroid Secretion:
- Pregnancy leads to increased secretion of Glucocorticoids, aiding in mobilization of amino acids from the mother's tissues for fetal tissue synthesis.
- Also, there is an increase in Aldosterone secretion, which causes reabsorption of excess sodium leading to fluid retention.
Increased Thyroid Gland Secretion:
- The thyroid gland enlarges and increases its production of Thyroxine.
- This is due to the thyrotropic effect of placental hCG and the secretion of placental human chorionic thyrotropin.
Increased Parathyroid Gland Secretion:
- The parathyroid gland enlarges, increasing calcium absorption from the mother's bones.
- Maintaining calcium ion concentration in the mother's extracellular fluid while the fetus uses calcium for ossification.
Secretion of "Relaxin" by the Ovaries and Placenta:
- Relaxin is secreted by the corpus luteum of the ovary and the placenta.
- This causes relaxation of the ligaments of the symphysis pubis and softens the cervix of the pregnant woman during delivery.

Response of the Mother's Body to Pregnancy

Pregnant women experience a typical weight gain of 25 to 35 pounds.
This includes the weight of the fetus, amniotic fluid, placenta, fetal membranes, uterus, breasts, extra fluid in the blood and ECF, and fat accumulation.

Eclampsia

Eclampsia represents an extreme form of preeclampsia.
It's characterized by vascular spasm throughout the body, clonic seizures in the mother (sometimes followed by coma), decreased kidney output, liver malfunction, extreme hypertension, and a generalized toxic condition of the body.
It usually occurs shortly before childbirth.
The best management involves vasodilating drugs followed by immediate termination of pregnancy.

Physiology of Parturition and Lactation

Parturition

Parturition marks the birth of the baby.
Increased Uterine Excitability Near Term:
- There are progressive hormonal changes that cause increased excitability of the uterine musculature.
- There are also progressive mechanical changes happening in the uterus near term.

Hormonal Factors That Increase Uterine Contractility

Increased ratio of estrogens to progesterone:
- During pregnancy, progesterone inhibits uterine contractility while estrogen increases it.
- The estrogen-to-progesterone ratio increases significantly towards the end of pregnancy.
Oxytocin:
- Oxytocin causes uterine contractions.
- Uterine muscle increases its oxytocin receptors in the last months of pregnancy.
- Oxytocin secretion by the neurohypophysis is significantly increased during labor.
- The stretching of the uterine cervix induces a hypothalamic neurogenic reflex.
Effect of fetal hormones:
- Fetal hormones, such as oxytocin, cortisol, and prostaglandins, also contribute to uterine contractions.

Mechanical Factors That Increase Uterine Contractility

Stretch of the Uterine Musculature:
- Stretching of smooth muscle organs increases their contractility.
Stretch or Irritation of the Cervix:
- Labor can be induced by rupturing the membranes, allowing the baby's head to stretch the cervix more forcefully.
- Stretching of nerves in the cervix initiates reflexes to the body of the uterus, causing myogenic transmission of signals from the cervix to the body of the uterus.

Labor pains

Cramping pain in early labor:
- This is mainly caused by hypoxia of the uterine muscle due to the compression of blood vessels within the uterus.
- It's initiated by the hypogastric nerves.
Stronger pain during expulsion:
- When the fetus is being expelled through the birth canal, pain becomes more intense due to cervical stretching, perineal stretching, and stretching or tearing of structures in the vaginal canal.
- It's initiated by somatic nerves.

Involution of the Uterus After Parturition

The uterus undergoes involution in the first 4 to 5 weeks after delivery.
It reduces in weight.
Suppression of pituitary gonadotropin and ovarian hormone secretion occurs during the first few months of lactation.
The placental site on the endometrial surface autolyzes, resulting in a vaginal discharge known as "lochia" (initially bloody, then serous).
The endometrial surface is re-epithelialized.

Development of the Breasts

The glandular tissue in the breasts begins developing during puberty, but it's only during pregnancy that it fully develops and becomes capable of producing milk.
Estrogens stimulate the growth of the breast's mammary glands and the deposition of fat, giving breasts their shape and mass.

Hormonal Regulation of Lactation

Other hormones involved in the ductal system development are: growth hormone, prolactin, adrenal glucocorticoids, and insulin.
Progesterone is crucial for the complete development of the lobule-alveolar system.

Prolactin and Lactation

Prolactin, secreted by the mother's anterior pituitary gland, promotes lactation.
- Blood prolactin levels rise steadily from the 5th week of pregnancy until childbirth.
- Estrogen and progesterone inhibit the actual secretion of milk.
- The placenta produces significant amounts of human chorionic somatomammotropin, which has lactogenic properties (promoting milk production).
Colostrum is a form of milk produced during late pregnancy and the first few days after parturition.
- It contains antibodies to protect the newborn against disease, is lower in fat, and higher in protein compared to regular milk.
- The colostrum also has a laxative effect, helping the baby pass their first stool.

Hormonal Regulation of Lactation (part 2)

After birth, the secretion of estrogen and progesterone from the placenta decreases, allowing prolactin's lactogenic effect to take over.
Each time the mother nurses her baby, nervous signals from the nipples to the hypothalamus cause a surge in prolactin secretion, lasting about an hour.

Prolactin and Oxytocin

Prolactin is responsible for the production and synthesis of milk, whereas oxytocin is involved in the release or ejection of milk.

Ovarian Cycles in Nursing Mothers

Ovulation usually doesn't resume in nursing mothers until a few weeks after they stop breastfeeding.

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Description

Explore the essential roles of early nutrition for the embryo and the overall function of the placenta in this quiz. Understand how the decidual cells provide initial nourishment and the processes that enable nutrient transfer between maternal and fetal blood. Test your knowledge on the crucial aspects of embryonic development and placental physiology.