Pregnant and nursing patient 1 - physiology Flashcards
1
Q
What is the site of fertilisation?
A
oviduct
2
Q
How long after ovulation must an ovum be fertilised by?
A
within 24hrs of ovulation, will begin to disintegrate after this
3
Q
How long can sperm survive in the female reproductive tract?
A
typically survive approx. 48hrs but can survive up to 5 days
4
Q
What percentage of sperm reach the site of fertilisation in the upper 1/3 of the oviduct?
A
0.001%
5
Q
What does the fertilised ovum divide and differentiate into as it moves from the site of fertilisation in the upper oviduct to the site of implantation in the uterus?
A
blastocyst
6
Q
What is the blastocyst composed of?
A
a hollow ball of cells encircling a fluid filled cavity with a dense of mass cells grouped to one side, known as the inner cell mass
7
Q
What is the trophoblast?
A
- thin outer most layer out blastocyst
- accomplishes implantation after which it develops into the foetal portion of the placenta
8
Q
What part of the blastocyst is destined to develop into the foetus?
A
the inner cell mass
9
Q
What is the site of implantation?
A
the endometrium of the uterus
10
Q
What is the first stage of implantation?
A
- when the free-floating blastocyst adheres to the endometrial lining, cords of trophoblastic cells begin to penetrate the endometrium
11
Q
What is the second stage of implantation?
A
- advancing cords of trophoblastic cells tunnel deeper into the endometrium, carving out a hole for the blastocyst. The boundaries between the cells in the advancing trophoblastic tissue disintegrate
- inner cell mass is starting to differentiate, giving rise to the start of the amniotic cavity
12
Q
What is the third stage of implantation?
A
- when implantation is finished, the blastocyst is completely buried in the endometrium, and the inner cell mass continues to differentiate and divide giving rise to the developing embryo
13
Q
What forms the placental villi?
A
Finger-like projections of chorionic tissue form the placental villi which protrude into a pool of maternal blood
14
Q
What breaks down the maternal capillary walls?
A
Maternal capillary walls are broken down by the expanding chorion so that maternal blood oozes through the spaces between the placental villi
15
Q
What branches off the umbilical arteries?
A
Foetal placental capillaries branch off umbilical arteries and project into the placental villi
16
Q
What separates the foetal blood in the vessels from the maternal blood?
A
the capillary wall and thin chorionic layer that forms the placental villi
17
Q
What does the maternal blood enter the placenta via?
A
maternal arterioles
18
Q
Once it has entered through the maternal arterioles, what does the maternal blood do?
A
percolates through the pool of blood in the intervillus spaces
19
Q
What happens in the pool of blood in the intervillus spaces?
A
This is where exchanges are made between the foetal and maternal blood before the foetal blood leaves through the umbilical vein and maternal blood exits through the maternal venules
20
Q
How does foetal blood leave the placenta?
A
through the umbilical vein
21
Q
How does maternal blood leave the placenta?
A
through the maternal venules
22
Q
What organs systems does the placenta form the functions of, and why?
A
the kidneys, and the digestive and respiratory systems
- the foetus has these organ systems but within the uterine environment they cannot and do not need to function
- the mother’s digestive tract, respiratory system, and kidneys serve the fetus’ needs as well as their own
23
Q
Why should pregnant people be cautious about exposing themselves to anything potentially harmful?
A
many drugs, environmental pollutants, other chemical agents, and microorganisms in the mother’s bloodstream can cross the placental barrier, and some of them may harm the developing fetus
24
Q
How do oxygen, carbon dioxide, water and electrolytes cross the placenta membrane?
A
by simple diffusion
25
How does glucose cross the placenta membrane?
by facilitated diffusion
26
How do amino acids cross the placenta membrane?
by secondary active transport
27
How does cholesterol cross the placenta membrane?
via receptor mediated endocytosis
28
What kind of organ does the placenta become during pregnancy?
a temporary endocrine organ
29
During pregnancy, what do 3 endocrine systems interact to do?
- to enhance growth and development of the foetus
- to coordinate the timing of the birth
- to prepare the mammary glands for nourishing the baby after birth
30
During pregnancy, what 3 endocrine systems interact?
- placental hormones
- maternal hormones
- fetal hormones
31
What are the most important placental hormones?
- Human chorionic gonadotropin (hCG)
- oestrogen
- progesterone
32
Why is the placenta unique among endocrine tissues?
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
33
What is human chorionic gonadotropin (hCG)?
- peptide placental hormone that acts to prolong the life span of the corpus luteum (CL)
- secreted by the developing chorion
34
What is the corpus luteum (CL) of pregnancy?
an ovation endocrine unit that grows larger and produces increasingly greater amounts of oestrogen an progesterone for ~10 weeks post-implantation
35
What does maintenance of a normal pregnancy depend on high concentrations of?
oestrogen and progesterone
36
What does persistence of oestrogen and progesterone maintain?
maintains the thick, pulpy endometrial tissue and menstruation ceases during pregnancy
37
In a male fetus, what does hCG stimulate?
stimulates precursor Leydig cells in the fetal testes to secrete testosterone, which masculinises the developing reproductive tract
38
How is hCG eliminated?
in the urine (this is how pregnancy tests work)
39
What may hCG been the underlying trigger for?
morning sickness
40
When does peak secretion of hCG occur?
approx. 60 days after the end of the last menstrual period
41
When does the fall in hCG secretion occur?
at a time when the corpus luteum is no longer needed because the placenta has began to secrete substantial quantities of oestrogen and progesterone
42
Why doesn’t the placenta secrete oestrogen in the first place instead of secreting hCG, which in turn stimulates the corpus luteum to secrete this hormone (and progesterone)?
- the placenta does not have all the enzymes needed for oestrogen synthesis in the first trimester
- oestrogen synthesis requires a complex interaction between the placenta and the fetus
43
How is oestrogen synthesised?
- the placenta secretes increasing quantities of progesterone and oestrogen into the maternal blood after the first trimester
- the placenta itself can convert cholesterol into progesterone but lacks some of the enzymes necessary to convert cholesterol into oestrogen
- in the foetal adrenal cortex, dehydroepiandroesterone (DHEA) can be derived from cholesterol
- DHEA reaches the placenta by means of the foetal blood
- DHEA can be converted into oestrogen in the placenta
44
Can the placenta synthesis progesterone?
yes, unlike oestrogen, the early placenta is capable of synthesising progesterone shortly after implantation
45
What is the amount of progesterone produced proportional to?
placental weight
46
After how long can the placenta produce enough progesterone to maintain the endometrial tissue?
10 weeks - the placenta is too small in the first 10 weeks
47
What does the increase in circulating progesterone in the last 7 months of gestation reflect?
placental growth during this period
48
What are oestrogen and progesterone secreted by in the 1st trimester, and in the 2nd and 3rd trimesters?
1st trimester - CL of pregnancy
2nd and 3rd trimesters - placenta
49
What are the roles of oestrogen during pregnancy?
- stimulates growth of myometrium, which increases in size throughout pregnancy. The strong uterine musculature is needed to expel the fetus during labour
- promotes development of mammary gland ducts, through which milk will be ejected during lactation
50
What is the myometrium?
uterine musculature
51
What are the roles of progesterone during pregnancy?
- main role is to prevent miscarriage by suppressing contractions of the uterine myometrium
- promotes formation of a mucus plug in cervical canal to prevent vaginal contaminants from reaching the fetus
- stimulates development of milk glands in the breasts in preparation for lactation
52
What is responsible for the development of the milk glands and the gland ducts?
glands - progesterone
ducts - oestrogen
53
Roughly how long is the period of gestation?
~38 weeks from conception (40 weeks from end of last menstrual period)
54
What physical changes happen within the mother to accommodate the demands of pregnancy?
- uterine enlargement
- breasts enlarge and develop ability to produce milk
- volume of blood increases by 30%
- weight gain
- respiratory activity increases ~20%
- urinary output increases, and the kidneys excrete additional wastes from the fetus
- increases nutritional requirements for the mother
55
What are the average increases in basal metabolic rate over pre-pregnancy values, for the 1st, 2nd and 3rd trimesters?
5, 10, and 25% respectively
56
What is parturition?
labour, delivery or birth
57
What does parturition require?
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
58
What changes happen during late gestation to prepare for parturition?
- Braxton-Hicks contractions
- Softening of the cervix
- the fetus shifts downwards (the baby “drops”)
59
What is softening of the cervix?
- dissociation of cervical collagen fibres allows cervical 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)
60
What happens during the onset of parturition?
- rhythmic, coordinated contractions begin at the onset of true labour
- as labour progresses, the contractions increase in frequency, intensity and discomfort
- these contractions force the fetus against the cervix, dilating the cervix
- having dilated the cervix enough for the fetus to pass through, these contractions force the fetus out through the birth canal
61
What factors are responsible for the progression of parturition?
Once parturition has begun there is a positive feedback cycle for oxytocin which acts to increase uterine contractions
- Pressure of the foetus against the cervix triggers a neuroendocrine reflex which in turn increases oxytocin secretion from the posterior pituitary, which increases uterine contractions
- This cycle is broken once the foetus has passed through the birth canal and is no longer pushing against the cervix
62
What are the 3 stages of labour?
1. cervical dilation
2. delivery of baby
3. delivery of placenta
63
What happens during the first stage of labour (cervical dilation)?
- the membrane surrounding the amniotic sac ruptures, amniotic fluid escapes out of the vagina and helps lubricate the birth canal
- cervix is forced to dilate to accommodate the diameter of the baby’s head (max. ~10cm)
- this may take many hours
64
Regarding cervical dilation, what issue can a breech birth cause?
if feet first, the feet may not dilate the cervix enough to let the head pass
65
What happens during the second stage of labour (delivery)?
- baby moves thorough the cervix to the vagina
- stretch receptors in the vagina activate a neural reflex that triggers contraction of the abdominal wall in synchrony with the uterine contractions
- mother can also voluntarily contract abs (“push”)
- after birth, the baby is freed from the placenta by cutting the umbilical cord. Cord is tied and forms the umbilicus (navel)
66
What happens during the third stage of labour (delivery of the placenta)?
- shortly after delivery a second series of uterine contractions separates the placenta from the myometrium and expels it through the vagina
- completed within 15-30 minutes
- after the placenta is expelled, continues contractions of the myometrium constrict the uterine blood vessels at site of placental attachement, to prevent haemorrhage
67
When does delivery begin, and how long does it usually take?
- begins once cervical dilation is complete
- usually takes 30-90 minutes
68
What is involution?
after delivery, when the uterus shrinks to its pre-gestational size
69
How long does involution take?
4-6 weeks
70
What is involution induced by?
- fall in oestrogen and progesterone when the placenta is lost at delivery
- the process is facilitated in mother who breast-feed their infants - oxytocin promotes myometrial contractions that helps maintain uterine muscle tone, enhancing involution
71
In non-pregnant females, what do the breasts consist of?
mostly of adipose tissue and a rudimentary duct system
72
What developments happen to the breasts during pregnancy?
- development of glandular structure
- each duct terminates in a lobule
- lobule made of milk producing glands - alveoli
- milk secreted from epithelial cells into lumen
73
What causes ejection of milk?
Alveolar epithelial cells secrete milk into the lumen and contraction of the surrounding myoepithelial cells ejects the secreted milk out through the duct
74
What is the role of prolactin and human chorionic somatomammotropic (hCS; placental hormone) in development of the breast?
induce the synthesis of enzymes needed for milk production
75
What is the role of prolactin in milk production?
prolactin also stimulated milk production after parturition
- stimulatory action of prolactin is blocked in later stage of pregnancy by high levels of oestrogen and progesterone
- immediately after parturition, oestrogen and progesterone levels fall, allowing prolactin to induce milk production
76
What does suckling trigger?
a neuroendocrine reflex that leads to secretion of:
- **prolactin** (stimulates milk production)
- **oxytocin** (stimulated milk ejection)
77
What is the role of oxytocin?
- stimulates contraction of myoepithelial cells (results in milk ejection)
- hastens involution
- suppresses LH and FSH secretion - suppresses menstrual cycle
78
Where is prolactin secreted from?
anterior pituitary
79
Where is oxytocin secreted from?
posterior pituitary
80
What are the components of breast milk?
Nutrients: water, triglyceride, lactose, proteins, vitamins, calcium and phosphate
In addition: immune cells, antibodies and other chemicals that are immunoprotective
81
What is colostrum?
the milk produced in the first 5 days after delivery
82
What does colostrum contain (compared to normal breast milk)?
lower concentrations of fat and lactose but higher concentrations of immunoprotective agents
83
What are the advantages of breast feeding for the mother?
- hastened uterine involution (oxytocin)
- suppressed LH and FSH secretion (prolactin)
- therefore, tends to prevent ovulation, decreasing likelihood of another pregnancy (although not a reliable method of contraception)
