PARTURITION
18-Mar-16
Male Reproductive System
1
Overview


Means birth of the baby
 Towards the end of pregnancy
 Increased uterine excitability
 Leading to strong rhythmical contraction
that the baby is expelled
Cause !

Progressive hormonal changes


18-Mar-16
Increase excitability of the uterine musculature
Progressive mechanical changes
Male Reproductive System
2
PARTURITION

Hormonal factors


Increase uterine contractility
Increased ratios of estrogen to
progesterone

Progesterone


Estrogen


Inhibits uterine contractility
Increase uterine contractility
From 7th month onwards


18-Mar-16
estrogen levels increase
progesterone levels remains
constant/diminishes
Male Reproductive System
3
PARTURITION

Oxytocin
 Secreted by neurohypophysis


increases uterine contractility near term
Observations
 Increased oxytocin receptors towards the
end
 Increased rate f oxytocin secretions at the
time of labor
 Labour prolonged in hypophysectomised
animals
 Uterine-cervix irritation/stretch increase
oxytocin production
18-Mar-16
Male Reproductive System
4
PARTURITION

Fetal hormones
i.
ii.
iii.

Oxytocin from pituitary gland
Cortisone from adrenal glands
PGs from fetal membranes
All increase the intensity of
uterine contraction
18-Mar-16
Male Reproductive System
5
PARTURITION

Mechanical factors that increase uterine
contractility
1.
2.
18-Mar-16
Stretch of the uterine musculature

Increased fetal movements

Twins are born on average 19 days earlier
than a single child

Increase contractility
Stretch or irritation of the cervix
 Elicit uterine contractions
 Rupture of membranes; head of baby stretches
cervix more forcefully than usual /irritation
Male Reproductive System
6
PARTURITION

Onset of labour
A positive feedback mechanism for
its initiation
Weak and slow rhythmical
contractions occurs most of
pregnancy period




Braxtom Hicks contractions
At the end we have stronger contractions that stretch
the cervix and later force the baby thru the birth canal
thereby causing parturition process called labour
18-Mar-16
Male Reproductive System
7
PARTURITION

Theory



Stretching of cervix by the fetus head finally
becomes great enough to elicit a strong reflex
increase in contractility of the uterine body
This pushes the baby forward which stretches the
cervix more and initiates more positive feedback
to the uterine body
Once the stretch of the uterine contraction
becomes greater than a critical value

each contraction leads to subsequent contraction


18-Mar-16
that becomes stronger and stronger
until maximum effect is achieved
Male Reproductive System
8
PARTURITION


Two types of positive feedback
Stretch of the cervix
1.
Uterine contractions

even more stretching of the cervix
Pituitary gland releases oxytocin
Abdominal muscle contraction during labour
2.



Pain signals- from uterus and birth canal during
labour elicit a neurogenic reflexes in the spinal
cord to the abdominal muscles causing intense
contractions of the muscles
Add greatly to the expulsion of the baby
18-Mar-16
Male Reproductive System
9
PARTURITION


Labour pains
Ist stage




Comes with each contraction
Caused by hypoxia of uterine musculature
Resulting from compression of the blood vessels
in the uterus
2nd stage


18-Mar-16
When the fetus is being expelled thru the birth
canal
Much ,ore severe pain caused by
i.
Cervical stretching
ii.
Perineal stretching
iii. Tearing of structures in the vaginal canal
itself
Male Reproductive System
10
PARTURITION

Pain conducted thru

The mothers spinal cord

to the brain

18-Mar-16
by somatic nerves instead of by the visceral
sensory nerves
Male Reproductive System
11
PARTURITION

Involution of the uterus after the
parturition
Occurs during the 1st-5th weeks
 Wt becomes less than half parturition wt
within 1 week
 4th week in lactating mothers as small as
before pregnancy
Cause



18-Mar-16
Suppression of pituitary gonadotropin and
ovarian secretion due to lactation
Male Reproductive System
12
PARTURITION



Placental site on the endometrial surface
autolyses, causing a vaginal discharge
(lochia)
Is first blood then serous in nature approx
10days
Endometrial surface becomes reepithelialised and ready for normal non
gravid sex life
18-Mar-16
Male Reproductive System
13
LACTATION


Development of the breast
1. monthly female sexual cycle

Begins at puberty




Stimulated by the estrogen
Stimulates growth of the breast
mammary glands
Deposition of fats to give the breast mass
2. high eostrogen state of pregnancy

18-Mar-16
Glandular tissue become completely
developed for production of milk
Male Reproductive System
14
LACTATION

1. growth of the ductal system

Eostrogen-major role

Secreted by placenta all thru pregnancy





Growth & branching of ductal system
Increased breast stroma quantity
Large quantity of fat laid down in stroma
Other hormones
 Growth hormone
 Prolactin
 Adrenoglucocorticoids
 insulin
Each plays some role in protein metabolism
18-Mar-16
Male Reproductive System
15
LACTATION

Initiation of lactation

Function of prolactin



From mother anterior pituitary gland
Progesterone/oestrogen inhibit actual
milk secretion
Other hormones with lactogenic effect

18-Mar-16
Placental human chorionic
somatomammotropin
Male Reproductive System
17
LACTATION

CLOSTRUM





Fluid produced last few days before and after the fisrts
few days after parturition
Contain protein & lactogen as milk
No fat
Maximum rate of production is 1/100 that of milk
production
Soon after birth




18-Mar-16
Sudden loss of progesterone and eostrogen from
placenta
Prolactin lactogenic effect takes over
From days 1-7 breast begins to secrete copious
quantities of milk instead of colostrum
Background production of growth hormone, insulin,
cortisol, parathyroid hormone provide amino acids,
fatty acids, glucose and calcium required for milk
production
Male Reproductive System
18
LACTATION


Prolactin levels decreases soon after
birth
Each time the mother nurses the baby,
nervous signals from the nipples to
hypothalamus cause a 10-20 fold surge
in prolaction secretion that last for
about 1 hour
18-Mar-16
Male Reproductive System
19
LACTATION

Hypothalamic control of prolactin secretion


Hypothalamus inhibit prolactin production
Damage to the hypothalamus or blockage of the
hypothalamic hypophysial portal tract



Increase prolactin secretion
Decrease secretion of the anterior pituitary hormones
Prolactin inhibitory hormone formed in
hypothalamus

18-Mar-16
is transported to hypothalamic hypophysial portal
system then to anterior pituitry gland
Male Reproductive System
20
LACTATION

SUPPRESSION of the female
ovarian cycles in nursing mothers

18-Mar-16
Nerve signals from the breast to the
hypothalamus that cause prolactin
secretion
 inhibit secretion of GnRH by the
hypothalamus
 Decreasing LH/FSH
Male Reproductive System
21
LACTATION

Ejection/let down process in milk
secretion
Function of oxytocin
 Neurogenic reflex
 Hormonal reflex
When the baby suckles
 Sensory impulses are transmitted thru
somatic nerves from the nipples to
mothers spinal cord then to her
hypothalamus


18-Mar-16
Male Reproductive System
22
LACTATION

Increased nerve signals


Oxytocin



promote oxytocin secretion & cause prolactin
secretion
Increases contraction of myoepithelial cells
surrounding the outer walls of alveoli
Milk expressed from alveoli into ducts at a
pressure of +10 to 20mmHg
30-60 seconds after a baby begins to suckle,
milk begins to flow

18-Mar-16
Process called milk ejection/milk let down
Male Reproductive System
23
LACTATION

milk production



Inhibition of milk ejection



Physical touch/suckling/fondling
Psychic – baby cry
Psychogenic factors
Generalized sympathetic nervous system
stimulation through out the mothers body
Inhibit oxytocin secretion

18-Mar-16
Depress milk production
Male Reproductive System
24
LACTATION

Milk composition


Nutrients
Antibodies


Against E. coli
Other anti-infection agents

Wbc



18-Mar-16
Neutrophills
macrophages
Macrophages against E.coli which
cause lethal diarrhoea in newborns
Male Reproductive System
25
LACTATION

Metabolic drain on the mother caused by
lactation


With this degree of lactation great quantities of
metabolic substrates are lost from the mother
For instance




18-Mar-16
50 gm of fat per day
100gm of lactose per day
2.3 of ca2pho4 per day
Out put of calcium & phosphates by lactating
mammals is greater than intake
Male Reproductive System
26
LACTATION



Unless the mother is drinking large
quantities of milk and has adequate intake of
vit D to supply the needed calcium &
phosphate
Parathyroid glands enlarge greatly
Bone becomes progressively decalcified
18-Mar-16
Male Reproductive System
27