Female reproductive system + pregnancy Flashcards
What are the main functions of the female reproductive system?
Produce haploid gametes
Facilitate fertilisation
Site for implantation of the embryo
Provide physical and nutritional needs to nurture the neonate after birth
What is the structure of the ovaries?
Cortex- outer zone with germinal epithelial layer that contains oocytes
Inner medulla- blood vessels and lymph
Oocytes are enclosed in follicle, follicular cells secrete steroid hormones
What are the three layers of the uterine wall?
Perimetrium
Myometrium
Endometrium
What is the structure of the endometrium?
Simple columnar epithelial cells
Compound tubular glands
Spiral arteries
Neuroendocrine control of the menstrual cycle
Hypothalamic-pituitary-gonadal axis drives the menstrual cycle
Hypothalamic neurons release gonadotropin-releasing hormone (GnRH)
Hypophyseal portal system connects hypothalamus to anterior pituitary
What is the effect of GnRH binding to receptors?
Binds to G protein coupled receptor activating PLC, leading to the formation of DAG, IP3 and an increase in Ca2+
Leads to exocytosis of gonadotropins FSH and LH
Action of FSH and LH on the ovaries
Stimulate ovaries to secrete progesterone from the theca and oestrogen, inihibin and activin from the granulosa
What do oestrogen and progesterone do?
Develop ovum
Maintain corpus luteum
Maintain pregnancy
What happens during the follicular phase of the endometrial cycle in terms of hormones?
Oestrogen forms channels to propel sperm
What happens in the proliferative phase of the endometrial cycle?
Secretion of oestrogen increases
Stimulated growth of endometrium, glands, stroma, spiral arteries elongate
What happens in the secretory phase of the endometrial cycle?
Following ovulation and is dominated by progesterone, endometrial proliferation slows and thickness decreases
Glands are tortuous with accumulated glycogen vacuoles, increased mucus
Stroma is oedamatous, ending in menses
How do hormonal contraceptives work?
Feedback to hypothalamus decreasing secretion of GnRH
Negative feedback on anterior pituitary gonadotropins to inhibit FSH/LH
Low FSH insufficient to stimulate folliculogenesis, low LH insufficient for ovulation
Progestin affects cervical mucus, fallopian tube motility, endometrial glycogen
How does the hormonal ‘morning after pill’ work?
Higher dose preparations inhibit ovulation and interfere with implantation
So therefore can be used as a postcoital contraceptive
How does fertilisation occur?
Sperm acrosomal reaction- penetration
Oocyte activation leads to cortical reaction: second meiotic division and prevents polyploidy
Fusion of haploid pronuclei to form diploid zygote
How does implantation occur?
Endometrium reception of blastocyst, which promotes endometrial stromal cells to predecidualize
Invasion of the endometrium is in 4 stages- hatching, apposition, adhesion and invasion
What are the two types of blastocyst trophoblastic cells?
Inner cytotrophoblast
Outer syncytiotrophoblast
What is the function of the intervillous space of the placenta?
Spaces between the mother’s blood vessels and fetal chorionic villi
Reduces force and velocity for exchange
What is the function of the syncytiotrophoblast lacunae?
Placental barrier between maternal and fetal blood
Merge and fill with maternal blood
In the mature placenta what is maternal and fetal blood seperated by?
Fetal capillary endothelium
Mesenchyme
Syncytiotrophoblast
Cytotrophoblasts
What substances are transported from maternal to fetal blood and how?
Glucose- facilitated diffusion
Amino acids- secondary active transport
Vitamins- active transport
What substances are transported from fetal to maternal blood and how?
Waste urea and creatine- diffusion
How are large molecules such as antibodies, hormones and LDL transported?
Receptor mediated endocytosis
Hormonal changes during trimester 1
In the trophoblast and then placenta- human chorionic gonadotropin HCG ‘rescues’ corpus luteum
Corpus luteum- continues secretion of progesterone and oestrogen to support endometrium
Hormonal changes during trimesters 2-3
Placenta becomes the primary hormone source
Human placental lactogens (hCS)- coordinate fuel economy of glucose to FA, ketone storage for neonate and development of mammary glands
Progesterone synthesised from circulatory progesterone
Oestrogen- placenta-foetal synthesis
What is stage 0 of parturition?
Quiescence- prelude to birth form conception to initiation of parturition, 95% of gestation
Uterus is relaxed and insensitive to uterotonic hormones
Progesterone suppresses myometrial contractions
Braxton-Hicks contractions in preparation
What happens during stage 1 of parturition?
Preparation for birth prior to labour
Foetal-H-P-adrenal axis increases in cortisol which increases oestrogen:progesterone, leads to an increase in contractility
Oestrogen stimulates prostaglandin release
What does the release of prostaglandin during stage 1 of parturition lead to?
Promotes formation of gap junctions
Softening, thinning and dilation of the cervix
What happens during stage 2 of parturition?
Increased prostaglandin and oxytocin levels lead to myometrial contraction and cervical dilation
Increased myometrial connectivity and responsiveness
Positive feedback using Ferguson reflex
Stages of delivery- dilation, expulsion and placental
What is the Ferguson reflex?
Neuroendocrine regulation of oxytocin
Uterine contraction stimulates prostaglandin
What happens during stage 3 of parturition?
Haemostasis- vasoconstriction of spiral arteries to decrease haemorrhaging
Decrease in placental oestrogen which leads to myometrial atrophy adn regression of uterine vasculature
Cervix remodelling
How long does it take to reestablish the endometrial cycle?
3-5 months
What structures are important for lactation?
Alveoli- secretory unit of breasts
Contractile myoepithelial cells and adipose tissue
What is colostrum?
First milk
High in fat, proteins and antibodies
How are hormones for lactation controlled during pregnancy?
Oestrogen + progesterone stimulate breast growth and development
Oestrogen stimulates anterior pituitary prolactin (PRL), the major milk production hormone and also stimulates breast development
In pregnancy oestrogen + progesterone inhibit PRL activity on breast
What is mammogenic hormone action?
Promotion of cell proliferation
What is lactogenic hormone action?
Promotion of initiation of milk production by PRL
What is galactokinetic hormone action?
Promotion of myoepithelial contraction by oxytocin
What is galactopoietic hormone action?
Maintenance of milk production by PRL + cortisol
