Parturition and lactation - Reproduction 4 Flashcards
Key learning objectives:
* Understand the key roles and source of
oestrogen and progesterone during pregnancy
* Describe the events responsible for both the
initiation and progression of labour
* Describe the process of lactation and its
control
See slide 3
Hypothalamus and Pituitary
What do they stand for?
PRH, PIH, CRH, ACTH
PRH= prolactin releasing;
PIH= prolactin Inhibiting;
CRH= corticotropin releasing (aka urocortin); ACTH= adrenocorticotropic
Oestrogen secreted into uterus causes?
Increased contractility of smooth muscle and increased responsiveness to oxytocin
Oestrogen secreted into anterior pituitary causes?
Prolactin secretion and growth and development of breast tissues
Oestrogen secretion in breasts causes?
Growth of duct tissue
Fat deposition
Suppression of lactation
Progesterone secretion into uterus?
Suppression of contractile activity (counteracts effects of oestrogens and oxytocin)
Maintenance of secretory-phase conditions
Progesterone secretion on breasts causes?
Growth of glandular tissue and suppression of lactation
hCG in male foetus causes?
production testosterone from Leydig cells= masculinization of the reprod. tract
MFP stands for?
Maternal-Placenta-Foetal-Unit
Problem with MPF?
Foetus cannot synthesise Progesterone (precursor for aldosterone and cortisol)
Placenta cannot synthesise Androgen (precursor for Oestrogens)
Solution to MFP?
– Placenta synthesises Progesterone for foetus (used by foetal adrenal glands → aldosterone, cortisol synthesis
– Mother and foetus synthesise Androgens for placenta
Placenta is an incomplete endocrine organ that needs help
SEE SLIDE 6 DIAGRAM
Can the foetus make oestrogen/progesterone?
No
Parturition requires?
– Dilation of cervical canal to accommodate passage of fetus from uterus
– Sufficiently strong contractions of uterine myometrium to expel fetus
Parturition means?
Childbirth
Mean pregnancy is how long and from when?
Mean pregnancy duration=38 weeks from ovulation/40 weeks from last menstruation
What is labor/delivery/birth?
Process whereby the foetus and its supporting placenta and membranes pass from the uterus to the outside world
Cervical dilation takes how long? up to?
24 hours
Delivery of the baby time period?
30-90 mins
Delivery of placenta - how long?
How much blood lost?
Uses what in the body?
15-30mins
350mL of blood lost
Smooth muscle cells and prostaglandins
Exact factors triggering increase in uterine contractility and initiating parturition not fully established
Factors that trigger increase in uterine contractility and initiating parturition could be?
From 2nd-3rd trimester - weak, spontaneous contractions (Braxton-Hicks) – uterine muscle fibres tighten and relax – not true labour. Toning uterine muscle? Blood flow to placenta?
Cervical softening?
What is prodromal labor?
– Days to weeks before true labour
– Consistent, uncomfortable contractions without/very little cervical dilation
– Cervix softening/ripening under influence of relaxin (placenta)
– Mucous plug expelled
Trigger for parturition what does the current theory suggest the signal is?
CRH: Corticotrophin-releasing hormone
Placenta: CRH released, acts on fetal pituitary
adrenocorticotropic hormone (ACTH)
– DHEA synthesis
– DHEA → Oestrogens
– Oestrogens enter maternal blood stream
Oestrogens level soaring towards onset of parturition is another trigger for parturition
1. What happens to connexions?
2. Oxytocin?
3. What happens with prostaglandins?
- Increases number of connexions - gap junctions between myometrial cells
- Increases oxytocin receptors in uterus;
- Increases prostaglandins produced by myometrium and foetal membranes
* Prostaglandins increase uterine responsiveness to oxytocin
* Cervical ripening – degrade local collagen fibres
See slide 10
Oxytocin increases uterine contractions - how?
▪ Acts directly on smooth muscle
▪ Thought labor initiated when oxytocin responsiveness reaches critical threshold – in response to normal oxytocin circulating levels
Inflammatory response is also a trigger or parturition?
1. What signals come from the foetus?
2. Immune cell invasion - what happens?
3. Inflammatory TFs play what role?
4. Increased proinflam cytokines and prostaglandins causes what to the uterus?
- Signals from fetus (surfactant lipoprotein
secretion, placental CRH, cortisol, estrogen) and mother (uterine stretch with increased
chemokine production, increased estrogen
receptor signaling) - Immune cell invasion of the fetal membranes, decidua, and myometrium – Proinflammatory cytokines (IL-1β, IL-8)
- Inflammatory TFs - NFB and AP-1 –
Proinflammatory and CAP gene expression,
decrease in PR activity - Increased proinflam cytokines and
prostaglandins: increased sensitivity of uterus to contraction inducing chemicals and help to
soften the cervix.
See slide 11 diagram
What critical responsiveness is necessary for the progression of parturition?
Oxytocin
Contractions begin at labor onset and what feedback cycle increases the force?
Positive-feedback cycle progressively increases
force
Does oxytocin cause stronger/weaker contractions?
Stronger
The pressure of foetus against cervix reflex causes what and what is this reflex called?
Pressure of fetus against cervix reflex increases oxytocin secretion – neuroendocrine
reflex
How long does this positive-feedback cycle progressively increase until?
Until cervical dilation and delivery are complete
Oestrogen has what effect with oxytocin?
Induces oxytocin receptors on uterus
Oxytocin has a + feedback and comes from foetus and pituitary what does it stimulate the placenta to make and what does it stimulate with the uterus?
Oxytocin stimulates the uterus to contract and stimulates placenta to make prostaglandins
Prostaglandins stimulated by oxytcin stimulates what?
More contractions of the uterus
See slide 13
Stages of LABOR
1. 1st stage is called?
2. How long does it?
- Cervical dilation
- Lasts from several hours to 24 hours+
in a first pregnancy
2nd stage of labor is called?
Usually lasts?
When does it begin?
- Delivery od the baby
- Usually lasts 30 to 90 min
- Begins when cervical dilation is complete
- 3rd stage of labor is called?
- What happens?
- How long?
- Delivery of the placenta
- Second series of uterine contractions separates placenta from uterine wall
- Shortest stage – usually completed within 15 - 30 min after baby is born
Breast is mainly made of?
Primarily adipose tissue with basic duct system
Duct system of breasts:
Secretory lobules empty into?
Ductless of 15-20 lobules combine into what?
This widens where?
Lactiferous duct carries the secretions where?
Secretory lobules empty into ductules
Ductules of 15 to 20 lobules combine into duct, Widens at the ampulla (reservoir).
Lactiferous duct carries the secretions to the outside.
Alveoli are the fundamental?
Secretory units - secretory epithelial cells (alveolar cells, secrete milk) + myoepithelial cells (milk ejection).
There are different pathways for secretion of the different milk components
Much of breast development occurs when?
Much of breast development occurs during first months of pregnancy
When are mammary glands capable of milk production?
Mid-pregnancy
There is inhibition of lactation during pregnancy why?
Oestrogen and progesterone during last
half of pregnancy block effect of prolactin
Prolactin and oxytocin roles in lactation?
Prolactin – Milk secretion
Oxytocin – Milk ejection
What is gestation?
Time between conception and birth
During gestation there is elevated placental oestrogen and progesterone which promotes the development of what?
Elevated placental oestrogen and progesterone promote development of ducts and alveoli in mammary glands - Prolactin
What initiates lactation?
Decrease in placental steroids at child birth: parturition
Lactation is sustained by?
Sucking as it triggers release of oxytocin and prolactin
Oxytocin has what role with lactation?
Causes milk ejection by stimulating myoepithelium to squeeze secreted milk out
through ducts
See diagram slide 17
Prolactin stimulates what in regards to lactation?
Stimulates synthesis of enzymes essential for milk production by alveolar epithelial cells
Stimulates secretion of more milk to replace milk ejected as baby nurses
Note: If not breastfeeding, What happens to PRL levels?
They fall -> ↑ GnRH -> ↑ LH and resumption of ovulation ~ 4-8 weeks
See slide 18
Human milk is fully mature when?
4-6 weeks post martum
Human milk how many kcal/dL
How much protein/dL
fat/dL
Lactose/dL
Leukocytes/dL
70kcal/dL
0.9g protein/dL (casein, lactalbumin)
4.5g fat/dL
7g lactose/dL
1-2*106 leukocytes/dL
What is colostrum?
breast milk first 5 days post partum
What is colostrum rich in?
Its a laxative to expel?
Prevents the build up of?
Rich in immunological content - IgA, IgG
Laxative to expel meconium
Prevents build up of bilirubin
Colostrum how many kcal/dL
How much protein/dL
fat/dL
Lactose/dL
Leukocytes/dL
Colostrum – First 5 days post partum
54kcal/dL
2.7g protein/dL
2.9g fat/dL
5.7g lactose/dL
7-8*106 leukocytes/dL
