Physiology of Motherhood Flashcards
What are the two parts of the uterus
Endometrium and myometrium
Describe the endometrium
Inner layer has good blood supply. Is the maternal contribution to the placenta
Describe the myometrium
Muscle layer, no contractions during pregnancy, contractions for labour
What is partuition
Labour, delivery of the baby, placenta and associated membranes
What initiates paruition
Chemical and physical factors
What is parturition physically associated with
Regular, painful uterine contractions
What is parturition physiologically associated with
Cervical ripening- cervix softens, shortens and dilates
Where do contractions occur
In the myometrium
What inhibits contractions during pregnancy
Progesterone
What type of muscles are used for contractions
Smooth muscles (involuntary control)
What happens in the last few weeks of pregnancy in terms of contractions
Braxton-Hicks practice contractions. They are painless and last a few seconds
Why do Braxton-Hicks contractions occur
Due to increased levels of oestrogen
How is parturition initiated
Complex interplay of local regulators, hormones and physical factors.
What are the physical factors associated with the initiation of parturition
Progressive stretching of the myometrium and placental insufficiency
What does progressive stretching of the myometrium result in
It becomes thinner and increases in excitability. At a critical level of excitability spontaneous contractions occur which squeeze the foetus towards the cervix.
What does placental “insufficiency” result in
The placenta is no longer able to provide sufficient nutrients and oxygen. Foetal capillaries in the placenta are blocked with blood clots and debris
What is involved in the chemical initiation of parturition
Hormone levels (in mother and foetus) and possibly other bioactive factors
What are the 4 hormone initiators of labour
Less progesterone. More oestrogen, prostaglandins and oxytocin
Which two chemical stimulate the release of oestrogen
Corticotropin-releasing hormone (CRH) and cortisol
Where is CRH secreted from and how does it increase oestrogen levels
It is released from the placenta and pituitary gland and releases oestrogen building blocks
Where is cortisol secreted from and how does it increase oestrogen levels
Secreted from foetal adrenal gland. Increases the oestrogen: progesterone ratio. It removes the inhibitory effect of progesterone on the myometrium
What happens to oestrogen levels towards the end of pregnancy
There is a large increase
What does the increase in oestrogen levels do
Increases the sensitivity of the uterus to contractile stimuli, increases the number of receptors for oxytocin in the uterus. Stimulates the release of prostaglandins
Where is oxytocin produced
In the posterior pituitary gland of the mother and foetus
What does oxytocin do
Stimulates powerful contractions of the uterus and stimulates the production of prostaglandins during pregnancy.
What does oxytocin do following delivery
It reduced blood loss
What are prostaglandins synthesised by
The placenta and myometrium
What can prostaglandins be used for
Inducing labour
What do prostaglandins do
Enhance contractions. One way is by releasing the calcium required for contractions
What happens to the baby before labour can begin
The baby has rotated, dropped low in the pelvis and head has “engaged” with the cervix. Results in stretching of the cervix
What does stretching of the cervix result in
Stretch receptors send messages to release oxytocin
What are the 3 stages of labour
- Dilation
- Explusion
- Placental
How long does dilation last
6-12 hours
When does dilation occur
From the onset of labour until full cervical dilation (10cm)
What happens during dilation
Opening up and thinning of the cervix. The cervix stretches around the engaged head. Uterine contractions increase in strength and frequency.
How long does explusion last
Minutes-hours
Usually less than 2 hours
When does explusion occur
Time from full cervical dilation until birth
What does the baby do during expulsion
Rotate to make birth easier
What happens during explusion
Continuous strong contractions force the foetus down and out of the uterus and vagina. Contractions alone are sufficient for delivery yet sometimes need to push
What happens to blood flow in the umbilical chord after birth
Blood continues to pass for a short time until blood pressure drops and blood flow stops
When can you cut the umbilical chord and why
Only once blood flow has stopped as useful nutrients is passed to the baby during this short time
How long does placental last
5-30 minutes
When does placental occur
From birth until delivery of the placenta
What happens during placental
Powerful contractions result in: explusion of placenta and membranes and closure of uterine blood vessels to reduce blood loss
What is lactation
Supply of milk to feed baby
Where is milk supplied from
The mammary glands
What happens to the mammary glands during pregnancy
Hormone induced changes occur
What stimulates the delivery of milk
Part hormonal part suckling
What is initially secreted from the breasts
Colostrum
Why do the breasts enlarge during pregnancy
Ducts proliferate, increasing in cell number and secretion. Fat is deposited between the lobules
Which hormones stimulate milk production
Combination of progesterone, oestrogen and placental lactogen
Why is milk production inhibited during pregnancy
Due to high levels of oestrogen and progesterone. Both decrease at birth
What hormone is secreted after birth
Prolactin
What is milk production stimulated by
A rise in prolactin and oxytocin
What further stimulates prolactin and oxytocin
Suckling
Where is prolactin secreted from
The anterior pituitary gland
What is the function of prolactin
Stimulates milk-producing epithelial cells
What is needed to maintain milk production
High levels of prolactin
Where is oxytocin secreted from
The posterior pituitary gland
What is the function of oxytocin
It stimulates milk ejecting epithelial cells
Describe the milk production and ejection reflex
Suckling -> sensory input -> hypothalamus ->
a. ) posterior pituitary -> oxytocin -> milk ejection
b. ) anterior pituitary -> prolactin -> milk production
When does lactation end
2-3 weeks after weaning
How long it’s colostrum present for
Until day 4
What is colostrum
A yellow fluid
What is the composition of colostrum
High in protein, low in fat, rich in immune molecules especially IgA, rich in some vitamins: A, D, E, K, rich in mnerals
What is the main source of energy in milk
Fat
What sugar is contained in milk
Lactose in high levels
What protein is contained in milk
Casein
What is found in milk apart from protein, sugar and fat
Calcium, minerals and vitamins
Which cells that fight against infection are found in breast milk
White blood cells
Which molecules are found in breast milk
IgA antibody, interferon and lysozyme
What properties do interferon and lysozyme have
They are antibacterial
What affect does breast feeding have on the infant later in life
Slight reduction in lymphoma, heart disease, allergies, respiratory and GI infections
What affect does breastfeeding have on mother
Protects against osteoporosis and breast cancer
How much milk does a baby weight 5-6kg consume a day
0.8-1 litre
How many calories does each litre of milk contain
750
What effect does the high calorie content of breast milk have on the mother
She needs extra nutrient in take, especially calcium and phosphate
