Pregnant and nursing patient: overview of physiology

Question 1

What is the inner cell mass?

Answer 1

destined to become fetus

Question 2

describe trophoblast

Answer 2

accomplishes implantation and develops into fetal portions of placenta

Question 3

What are functions of the placenta?

Answer 3

• forms the functions of the kidneys and digestive and respiratory systems

Question 4

How are nutrients and Oxygen brought to the fetus?

Answer 4

In the maternal blood are acquired by the mother’s digestive and respiratory systems, and the CO2 and wastes transferred into the maternal blood are eliminated by the mother’s kidneys and lungs

• the mother’s digestive tract, respiratory system, and kidneys serve the fetus’s needs as well as her own

Question 5

What does the placenta become?

Answer 5

the placenta becomes a temporary endocrine organ during pregnancy

Question 6

Describe the three endocrine systems

Answer 6

During pregnancy three endocrine systems interact to support and enhance the growth and development of the fetus, to coordinate the timing of parturition (birth), and to prepare the mammary for nourishing the baby after birth:

• placental hormones
• maternal hormones
• fetal hormones

Question 7

What are the most important placental hormones?

Answer 7

• Human chorionic gonadotropin (hCG)
• estrogen
• progesterone

Question 8

Why is the placenta a unique among endocrine tissues?

Answer 8

1) Transient tissue
2) Secretion of its hormones is not subject to extrinsic control. Instead, the type and rate of placental hormone secretion depend primarily on the stage of pregnancy

Question 9

describe human chorionic gonadotropin (hCG)

Answer 9

Peptide placental hormone that cats to prolong the life span of the corpus luteum (CL)

Question 10

Describe CL in pregnancy

Answer 10

Is an ovarian endocrine unit that grows larger and produces increasingly greater amounts of estrogen and progesterone for ~ 10 weeks post - implantation
- maintenance of a normal pregnancy depends on high concentrations of estrogen and progesterone
- persistence of estrogen and progesterone maintains the thick, pulpy endometrial tissue and menstruation ceases during pregnancy

Question 11

describe hCG in male fetus

Answer 11

hCG stimulates precursor leydig cells in the fetal testes to secrete testosterone, which masculinises the developing reproductive tract

Question 12

Where is hCG eliminated?

Answer 12

In the urine

Question 13

How is hCG detected?

Answer 13

pregnancy diagnostic tests detect hCG in the urine as early as the first month of pregnancy (~ 2 weeks after the first missed menstrual period)

• hCG may be the underlying trigger for “Morning” sickness

Question 14

Why doesn’t the placenta secrete estrogen in the first place instead of secreting hCG, which in turn stimulates the corpus luteum to secrete this hormone (and progesterone)?

Answer 14

• The placenta does not have all the enzymes needed for estrogen synthesis in the first trimester
• estrogen synthesis requires a complex interaction between the placenta and the fetus

Question 15

describe the secretion of progesterone

Answer 15

• The placenta can synthesise this hormone soon after implantation
• However, the amount of progesterone produced is proportional to placental weight
• The placenta is too small in the first 10 weeks to produce enough progesterone to maintain the endometrial tissue
• the increase in circulating progesterone in the last 7 months of gestation reflects placental growth during this period

Question 16

What are the roles of estrogen and progesterone during pregnancy?

Answer 16

• High concentrations of both hormones are required to maintain pregnancy
• Both hormones are secreted by the CL of pregnancy in the 1st trimester and by the placenta in the 2nd and 3rd trimesters

Question 17

describe estrogen

Answer 17

• stimulates growth of the myometrium, which increases in size throughout pregnancy. The stronger uterine musculature is needed to expel the fetus during labour
• also promotes development of mammary gland ducts, through which milk will be ejected during lactation

Question 18

describe progesterone

Answer 18

• main role is to prevent miscarriage by suppressing contractions of the uterine myometrium
• also promotes formation of a mucus plug in the cervical canal to prevent vaginal contaminants from reaching the fetus
• progesterone stimulates development of milk glands in the breasts in preparation for lactation

Question 19

When is the period of gestation (pregnancy)?

Answer 19

Is ~38 weeks from conception (40 weeks from the end of the last menstrual period)

Question 20

What are some of the physical changes within the mother that accommodate the demands of pregnancy?

Answer 20

• Uterine enlargement
• Breasts enlarge and develop the ability to produce milk
• volume of blood increases by 30%
• weight gain (mostly from increased weight of the uterus and increased blood volume)
• respiratory activity increases ~20%
• urinary output increases, and the kidneys excrete additional wastes from the fetus
• Increased nutritional requirements for the mother

Question 21

Describe what parturition (labour, delivery or birth) requires

Answer 21

1) Dilation of the cervical canal to accommodate passage of the fetus from the uterus through the vagina and to the outside

2) Contractions of the uterine myometrium that are strong enough to expel the fetus

Question 22

Describe braxton-hicks contractions

Answer 22

• Occur during the last trimester
• Mild contractions that are experienced with increasing strength and frequency
• Sometimes regular enough to be mistaken for the onset of labour (“false labour”)

Question 23

Describe softening of the cervix

Answer 23

• Dissociation of cervical collagen fibres allows cervix to dilate during labour
• Cervical softening is caused largely by relaxin, a peptide hormone produced by the CL of pregnancy and by the placenta
• (Relaxin also relaxes the birth canal by loosening the connective tissue between the pelvic bones)

Question 24

What is a breech birth?

Answer 24

Any part of the body other than the head approaches the birth canal first

Question 25

Describe the third stage of birth (delivery of placenta)

Answer 25

• Shortly after delivery, a second series of uterine contractions separates the placenta from the myometrium and expels it through the vagina (“afterbirth”)
• Completed within 15-30 minutes
• After the placenta is expelled, continued contractions of the myometrium constrict the uterine blood vessels at site of placental attachment, to prevent haemorrhage

Question 26

Describe involution

Answer 26

• After delivery, the uterus shrinks to its pregestational size (involution)
• Takes 4-6 weeks

Induced by:
- Fall in estrogen and progesterone when the placenta is lost at delivery
- The process is facilitated in mothers who breast-feed their infants. Oxytocin promotes myometrial contractions that help maintain uterine muscle tone, enhancing involution

Question 27

What triggers development of the breast?

Answer 27

During pregnancy:
- Estrogen promotes extensive duct development
- Progesterone stimulates abundant alveolar-lobular formation
- Prolactin (anterior pituitary hormone) and human chorionic somatomammotropin (hCS; placental hormone) induce the synthesis of enzymes needed for milk production
- Prolactin also stimulates milk production after parturition
- Stimulatory action of prolactin is blocked in later stages of pregnancy by high levels of estrogen and progesterone
- Immediately after parturition est & prog levels fall, allowing prolactin to induce milk production

Question 28

Describe suckling

Answer 28

• Suckling triggers a neuroendocrine reflex that leads to secretion of:
• Prolactin (stimulates milk production)
• Oxytocin (stimulates milk ejection)
• Oxytocin stimulates contraction of myoepithelial cells
• Oxytocin hastens involution
• Oxytocin suppresses LH & FSH secretion - suppresses menstrual cycle

Question 29

Advantages of breast feeding for the mother

Answer 29

• Oxytocin release triggered by nursing hastens uterine involution
• Prolactin inhibits GnRH, thereby suppressing FSH and LH secretion
• Lactation, therefore, tends to prevent ovulation, decreasing the likelihood of another pregnancy (although not a reliable method of contraception)

Question 30

Answer 30

Question 31

Question 32