Overview Of Physiology

Question 1

Functions of the placenta

Answer 1

1. Forms the functions of the kidneys and digestive and respiratory systems (mother’s organs do the work for the fetus).
2. Nutrients and O2 brought to the fetus in the maternal blood are acquired by the mother’s digestive and respiratory systems.
3. CO2 and waste transferred into the maternal blood eliminated by mother’s kidneys and lungs.

Question 2

How do various substances cross over the placenta?

Answer 2

1. Simple diffusion: O2, CO2, water and electrolytes
2. Facilitated diffusion: glucose
3. Secondary active transport: amino acids
4. Receptor-mediated endocytosis: cholesterol

Question 3

Placenta: temporary endocrine organ

Answer 3

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 glands for nourishing the baby after birth.

1. Placental hormones
2. Maternal hormones
3. Feral hormones

Question 4

The most important placenta hormones are…

Answer 4

1. Human chorionic gonadotropin (hCG)
2. Estrogen
3. Progesterone

Question 5

The placenta is unique among endocrine tissues as…

Answer 5

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 6

Human chorionic gonadotropin (hCG)

Answer 6

Hormone - acts to prolong the life span of the corpus luteum (CL).

Question 7

Corpus luteum (CL)

Answer 7

An ovarian endocrine unit that grows larger and produces increasingly greater amounts of estrogen and progesterone for ~10 weeks post-implantation.

Question 8

How does estrogen and progesterone maintain a normal pregnancy?

Answer 8

Persistence of estrogen and progesterone maintains the thick, pulpy endometrial tissue and menstruation ceases during pregnancy.

Question 9

How do pregnancy tests work?

Answer 9

Detect hCG in the urine as early as the first month of pregnancy (~2 weeks after missed period).

Question 10

What does hCG ensure in male fetuses?

Answer 10

Stimulates the production of testosterone and the development of the reproductive tract.

Question 11

Where is estrogen and progesterone secreted from?

Answer 11

1. The corpus lutem in the 1st trimester
2. The placenta in the 2nd and 3rd trimester

Question 12

Role of estrogen

Answer 12

Stimulates growth of the myometrium, which increases in size throughout pregnancy. The stronger uterine musculature is needed to expel the fetus during labour.

Question 13

Role of progesterone

Answer 13

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 breast in preparation for lactation.

Question 14

The period of gestation

Answer 14

~38 weeks

Question 15

Physical changes within the mother to accommodate the demands of pregnancy

Answer 15

1. Uterine enlargement
2. Breasts enlarge and develop the ability to produce milk.
3. Volume of blood increases by 30%
4. Weight gain
5. Respiratory activity increases by 20%
6. Urinary output increases (having to pee for fetus too)
7. Increase in nutritional requirements

Question 16

Parturition

Answer 16

Labour/birth/delivery

Question 17

What occurs during parturition?

Answer 17

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 18

Braxton-Hick contractions

Answer 18

During last trimester
Often mistaken for labour

Question 19

Softening of the cervix

Answer 19

Dissociation of cervical collagen fibres allows cervix to dilate during labour.
Cervical softening is caused by relaxin, a peptide hormone produced by the CL of pregnancy and by the placenta.

Question 20

Breech birth

Answer 20

Any part of the body tries to exit the cervix before the head.

Question 21

Onset of parturition

Answer 21

1. Rhythmic, coordinated contractions begin at the onset of true labour.
2. As labour progresses, the contractions increase in frequency, intensity and discomfort.
3. Cervix dilates, fetus is pushed out the vagina.

Question 22

Stages of birth summaried

Answer 22

1. Amniotic sac ruptures “my water’s broke”
2. Delivery of fetus: 30-90 minutes
3. Delivery of placenta: second series of contractions 15-30mins.

Question 23

Involution

Answer 23

Uterus shrinking to its pregestational size induced by fall in estrogen and progesterone.

Facilitated by breast-feeding, oxytocin promotes myometrial contractions that help maintain uterine muscle tone, enhancing involution.

Question 24

Breast develops during pregnancy…

Answer 24

Develop a gland; each duct terminates in a lobule made of milk producing glands (alveoli), milk secreted from epithelial cells into lumen.

Question 25

What triggers development of the breasts?

Answer 25

During pregnancy: estrogen duct development, progesterone stimulates abundant alveolar-lobular formation.

Question 26

Prolactin

Answer 26

Initially inhibited by estrogen/progesterone during pregnancy, then when the levels of these hormones fall prolactin begins its action stimulating milk production.

Question 27

Suckling

Answer 27

Triggers secretion of:
Prolactin —> stimulates milk production.
Oxytocin —> stimulates milk ejection.

Question 28

Oxytocin

Answer 28

Contraction of myoepithelial cells.
Hastens involution
Suppresses LH & FSH secretion - suppresses mistrial cycle.

Question 29

Breast milk contents

Answer 29

Nutrients, water, immune cells, proteins, antibodies…e tc

Question 30

Colostrum

Answer 30

Milk produced in the first 5 days after delivery, contains lower concentrations of fat and lactose but higher concentrations of immunoprotective agents.