2 - Physiology Flashcards
What do LH and FSH do in women?
Hypothalamus releases gonadotrophin-releasing hormone (GnRH) to stimulate anterior pituitary to produce LH and FSH
LH and FSH stimulate development of follicles in the ovaries.
Theca granulosa cells around the follicles secrete oestrogen.
Oestrogen has negative feedback effect on the hypothalamus and anterior pituitary to suppress the release of GnRH, LH and FSH.
What is the role of oestrogen and progesterone?
Oestrogen
Produced by ovaries in response to LH and FSH. Promotes female secondary sexual characteristics:
- Breast tissue development
- Growth and development of the female sex organs (vulva, vagina and uterus) at puberty
- Blood vessel development in the uterus
- Development of the endometrium
Progesterone
Produced by the corpus luteum after ovulation. Produced mainly by the placenta from 10 weeks gestation onwards.
Acts on tissues that have previously been stimulated by oestrogen. Progesterone acts to:
- Thicken and maintain the endometrium
- Thicken the cervical mucus
- Increase the body temperature
What are the stages of puberty in girls?
AGED 8-14
- Breast buds (Thelarche)
- Pubic Hair
- Axillary hair and thicker pubic hair
- Menarche
FSH levels plateau about a year before menarche. LH levels continue to rise, and spike just before they induce menarche.
Why do overweight children go through puberty earlier?
Adipose tissue contains aromatase that converts androgens to oestrogens
What are the different phases of the menstrual cycle?
Follicular phase: from start of menstruation to the moment of ovulation (the first 14 or so days in a 28-day cycle)
Luteal phase: from moment of ovulation to the start of menstruation (strictly 14 days)
What happens in the follicular phase of the menstrual cycle?
FSH stimulates further development of secondary follicles. As the follicles grow, the granulosa cells that surround them secrete increasing amounts of oestradiol (oestrogen).
Oestrogen has negative feedback effect on the pituitary gland, reducing the quantity of LH and FSH produced.
Rising oestrogen also causes the cervical mucus to become more permeable, allowing sperm to penetrate the cervix around the time of ovulation
One of the follicles is the dominant follicle.
Luteinising hormone (LH) spikes just before ovulation, causing the dominant follicle to release the ovum from the ovary
What happens in the luteal phase of the menstrual cycle?
NB - Image
Follicle that released the ovum collapses and becomes the corpus luteum
Corpus luteum secretes high levels of progesterone, which maintains the endometrial lining and thickens cervical mucus
If fertilisation syncytiotrophoblast releases HCG to maintain the corpus luteum. Without hCG, the corpus luteum degenerates.
This fall in oestrogen and progesterone causes the endometrium to break down and menstruation to occur. Stromal cells of the endometrium release prostaglandins.
Negative feedback from oestrogen and progesterone on the hypothalamus and pituitary gland ceases, allowing FSH and LH to his again
What are the different stages a fertilised egg goes through before implantation?
- Zygote
- Morula
- Blastocyst (Syncitiotrophoblasts)
What is HCG produced by and why is it important?
Syncitiotrophoblasts after implantation
Maintains corpus luteum to allow it to keep producing progesterone and oestrogen until the placenta can take over
After implantation what is the next stage the blastocyst undergoes?
Cells of embryo blast split in two, with the yolk sac on one side and the amniotic cavity on the other. The embryonic disc sits between the two
Chorion surrounds this complex (cytotrophoblast and the syncytiotrophoblast)
How does the placenta develop?
Syncytiotrophoblast grows into endometrium and forms finger-like projections called chorionic villi, containing fetal blood vessels.
Chorionic villi nearest connecting stalk (chorion frondosum) are the most vascular and contain mesoderm. Cell proliferate and become the placenta. The connecting stalk becomes the umbilical cord.
Placental development is usually complete by 10 weeks gestation.
What are lacunae and how do they form?
Space around the chorionic villi that fills with maternal blood
Trophoblast invasion of the endometrium sends signals to the spiral arteries reducing their vascular resistance and making them more fragile. The blood flow to these arteries increases, and eventually they break down, leaving pools of blood called lacunae Maternal blood flows from the uterine arteries, into these lacunae, and back out through the uterine veins
What is the importance of the lacunae if they do not form properly?
If formation of these are inadequate can lead to pre-eclampsia
When there is high vascular resistance in the spiral arteries causing a sharp rise in maternal blood pressure
What are some of the functions of the placenta in general terms?
- Respiration
- Nutrition
- Endocrine
- Excretion/Kidneys (urea and creatinine)
- Immunity
How does oxygen get from mother to baby?
Fetal haemoglobin has higher affinity for oxygen so when the vessels run next to each other in the chorionic villi the oxygen is pulled from the mother’s blood
Carbon dioxide, hydrogen ions, bicarbonate and lactic acid are also exchanged in the placenta, allowing the fetus to maintain a healthy acid-base balance.
What is the endocrine function of the placenta?
HCG: maintain corpus luteum until can make it’s own progesterone
Oestrogen: softens tissues and makes them more flexible for birth, enlarges breasts and nipples
Progesterone: Week 5, maintains pregnancy by relaxation of the uterine muscles (preventing contraction and labour) and maintains the endometrium.
What are some of the side effects of raised progesterone in pregnancy?
All due to the relaxation of muscles it causes
- Heartburn
- Constipation
- Hypotension, headaches and skin flushing (relaxing of blood vessels)
- Raised body temperature
What are some changes to the following systems in pregnancy:
- Skin
- Endocrine
- Respiratory
What are some changes to the following systems in pregnancy:
- Renal
- Cardiovascular
- Blood
What are some changes to the following systems in pregnancy:
- Myometrium
- Cervix and Uterus
- Uterus
- Vagina
What are the three stages of labour?
1st Stage: From onset of true regular contractions until 10cm cervical dilatation
2nd Stage: From 10cm to delivery of baby
3rd Stage: From delivery of baby to delivery of placenta
What hormone controls labour?
Prostaglandins
Ripe cervix before delivery and then stimulate contraction of uterus
Prostaglandin E2 (Dinoprostone) can be given as a pessary to induce labour
What happens during the first stage of labour?
Cervical dilation and effacement occurs and a show (mucus plug) will come out. Baby head into pelvis
Usually takes 8 hours if first labour or 5 hours for subsequent
Latent Phase: 0 to 3cm dilation of the cervix, irregular contractions
Active Phase: 3-7cm dilation, regular contractions
Transition: 7-10cm, strong regular contractions
What observations need to be done for a woman in the first stage of labour?
Use a partogram
- Heart rate hourly
- Vitals 4 hourly
- Urinary frequency
- Frequency of contractions half hourly
- Vaginal exam hourly
- Regular analgesia
What happens during the second stage of labour?
From fully dilated to deliver and depends on 3 Ps (power, passenger, passage)
- Power: strength of contractions
- Passenger: Size, Attitude, Lie, Presentation
- Passage: shape and size
What are the different types of breech presentation?
Feet closest to cervix
- Complete (hips and knees flexed like cannonball)
- Frank (hips flexed and knees extended so bottom first
- Footling (foot through cervix)
What are the seven cardinal movements of labour?
- Engagement
- Descent
- Flexion
- Internal rotation
- Extension
- Restitution and External rotation
- Expulsion