Changes to female repro system + placenta growth Flashcards
State the functions of the placenta using ‘serpent’
S - storage E - endocrine R - respiration P - protection E - excretion N - nutrition T - transfer
Explain the placental function ‘storage’
metabolises glucose and stores it as glycogen. Iron and fat-soluble vitamins
Explain the placental function ‘endocrine’
oestrogen and progesterone
Explain the placental function ‘respiration’
gaseous exchange to and from the foetus by diffusion
Explain the placental function ‘protection’
limited barrier to infection and some medication e.g chicken pox, syphillis, TB
Explain the placental function ‘excretion’
carbon dioxide and bilirubin
Explain the placental function ‘nutrition’
transferred from the maternal to fetal blood for baby to grow and develop
Explain the placental function ‘transfer’
of substances e.g. glucose
Within a few days of fertilisation, how doe the endometrium get prepared for the embryo?
trophoblasts produce human chorionic gonadotrophin (hCG) to prepare the endometrium
What is the term for structural changes and increased vascularity within the endometrium?
decidualisation
The endometrium is referred to as the decidua in pregnancy. What are the 3 regions of the decidua?
- decidua basalis
- decidua capsularis
- decidua vera/parietalis
Describe the decidua basalis
lies between the developing embryo and the stratum basalis of the uterus at the implantation site
Describe the decidua capsularis
covers the developing embryo separating it from the uterine cavity
Describe the decidua vera/parietalis
line the remainder of the cavity
What are the two stages of implantation?
1 prelacunar
2 lacunar
Explain the ‘prelacunar’ stage of implantation
- 7 days post conception
- blastocyst makes contact with decidua
- placentation begins
- maternal connective tissue invaded
- trophoblasts differentiate in to two layers - cytotrophoblasts, syncytiotrophoblasts
When implantation occurs, the trophoblasts differentiate into two layers:
cytotrophoblasts - cells of the inner layer that retain their cell boundaries
syncytiotrophoblasts - cells in the outer layer that retain their cell boundaries
Explain the ‘lacunar’ stage of implantation
- increasing number of syncytiotrophoblasts invading blood vessels
- ‘lacunae’ - small lakes form within these cells
- the lacunae will become the intervillous spaces, bathed in blood 10-12 weeks following conception
- placenta accreta - abnormally adhered placenta due to excessive trophoblastic invasion
What are chorionic villi?
finger-like projections of chorion surround by cyto and syncytotrophoblastic layers
Define vasculogenesis
new blood vessels develop in response to a low level of oxygen
Define angiogenesis
further growth of blood vessels produce a vascular network which connect blood vessels developed in the embryo via umbilical arteries and veins
The villi differentiate and specialise in to:
anchoring villi and nutritive villi
Where does the villi mostly profuse before development of the placenta?
into the decidua basalis where the blood supply is greatest - known as the chorion fronosum - this then develops in to the placenta
Explain the process of syncytiptrophoblasts creating ‘small lakes’
the syncytiotrophoblasts surrounded the villi erode the walls of the maternal vessels as the penetrate the low myometrium, opening them up in a funnel shape. This forms a lake of maternal blood which the villi float in
Until what gestation doe the villi cover the entire chorionic sac?
8 weeks
What happens to the chorionic villi touching the decidua capsularis?
degenerate after 8 weeks due to limited blood supply and come the chorion laeve which become the chronic membrane
As the conceptus grows what happens to the decidua capsularis an parietalis?
capsularis bulges into the uterine cavity and fuses with the parietalis
What is the amnion? Where is it? What does it contain?
The amnion is a tough, smooth, translucent membrane, lining the chorion, surface of the placenta and umbilical cord. It contains cells which produce amniotic fluid and prostaglandins
The amniotic cavity is filled with amniotic fluid. What is it’s function?
- provides a buoyant environment that protects the embryo
- helps maintain a homeostatic temperature
Where does amniotic fluid come from?
initially from maternal blood and later, fetal urine
What are the 3 layers of the uterus?
- perimetrium
- myometrium
- endometrium
Describe the perimetrium
- thin layer of peritoneum over the uterus and uterine tubes
- connective tissue made up of collagen and elastin fibres
- continuous with broad ligaments
What happens to the perimetrium during pregnancy?
- distorted during pregnancy
- increases stress and stretch on ligaments
- ligaments stretching will make it hard to localise pain later in pregnancy
What are the ligaments associated to the perimetrium?
suspensory ligaments
round ligaments
broad ligaments
What changes occur to the myometrium in pregnancy?
- smooth muscle cells increased length 10 fold
- oestrogen and progesterone increase mass and composition of extracellular matrix
There are 3 phases of myometrial development. What are they?
proliferative, synthetic, contractile
What happens in proliferative phases of myometrial development?
increase in number of smooth muscle cells (myocytes)
What happens in synthetic phase of myometrial development?
increase size of myocytes and remodelling of ECM (extracellular matrix)
What happens in the contractile phase of myometrial development?
muscle cell size stabilises and muscle prepare prepares for the labour phase
Define uterine quiescence
a state of quietness or inactivity
hormone control
At what gestation can braxton hicks begin?
12 weeks
What changes occur to the endometrium (decidua) in pregnancy?
- decidualisation - nourishment and dampening of the local immune response
- increased vascularity
- placental development
What happens to the cervix during pregnancy?
the closed, rigid structure becomes soft, distensible and effaced (thinning out) by term
Cervix: What is ‘hegar’s sign’?
softening of the cervix due to progesterone
Cervix: What is ‘goodell’s sign’?
blue/purple colouration due to increased blood flow
What is the ‘cervical plug’?
thick mucus secreted to form a plug known as the operculum. The operculum prevents ascending infections (through vagina, up to cervix, travelling up)
Vagina: What is ‘chadwick’s sign’?
blue/purple colour due to increased blood flow
What changes occur to the vagina in pregnancy?
- vaginal walls - mucosa thickens, connective tissue loosens, smooth muscle cells increase in size
- leucorrhea - thick, white discharge
- increased acidity to protect from infection
