🛑 The Placenta

Question 1

What is the placenta?

Answer 1

• the connector between the mother and the devloping foetus
• placental development and function determines the outcome of pregnancy

Question 2

what is the role of the placenta?

Answer 2

• facilitate the exchange of oxygen, nutrients and waste between the mother & foetus
• it’s a key source of oxygen, energy and hormone for the foetus

Question 3

briefly describe fertilisation

fertilisation

Answer 3

• if sperm penetrates the egg, fertilisation occurs within the fallopian tubes; egg & sperm become zygotes
• The cilia in the fallopian tubes move the zygote along the fallopian tubes
• as the zygote moves to the uterus , it repeatedly divides forming blastocytes

blastocytes –> a hallow ball of cells

Question 4

what two main types of cell are contained in blastocytes?
what do they form later on?

fertilisation

Answer 4

• Throphoblasts –> which forms the placenta
• Inner cell mass –> which will form the embryo

Question 5

briefly describe what occurs on implantation

implantation

Answer 5

• around day 6 post fertilisation, blastocyte reaches the endometrium and begins impaltation process
• on the 8th day of development throphoblasts differentiate itno 2 layers:
  Cytotrophoblast (inner layer)
  Syncytiotrophoblasts (outer layer)

Question 6

describe cytotrophoblasts

implantation

Answer 6

they are stem cells that continuously proliferate into syncytiotrophoblasts during villi formation

Question 7

describe syncytiotrophoblasts

implantation

Answer 7

• releases hydrolytic enzymes to break down stromal tissues to allow invasion in endometrial lining
• secrets hCG (Human Chorionic Gonadotrphin) –> this stimulate the corpus luteum to keep producing progetserone until placenta takes ober hormone production

Question 8

describe what occurs in early placental formation

Answer 8

• On day 9 lacunea (spaces) form within syncytiotrophoblasts
• As the blastocyte invaded deeper the syncytiothroophoblasts break down maternal tissue - this allows blood (from uterine spiral arteries) to enter the lacunae (these are the spaces that form on day 9)
  These lacunea fuse to form lacunear networks (intervoillous space) –> this allow early uteroplacental circulatio by the end of week 2
• (simultaneously): the cytotrophoblasts initiate Primary Chorionic Villi formation by expanding into the sycytiotrophoblast

Primary Chronionic Villi –> they are finder like projections

Question 9

name the three stages of the chorionic villi development

early placenta formation

Answer 9

1. Primary Chorionic Villi formation
2. Secondary Chrionic Villt formation
3. Tertiary Chorionic Villi formation

Question 10

describe Primary Chroionic Villi formation

Answer 10

• this is day 11-13
  Formed by proliferation of the cytotrophoblasts which expand into the sorrounding syncytotrophoblast

Question 11

describe Secondary Chorionic Villi formation

Answer 11

• thsi is approx. day 16
  The extarembryonic mesoderm grows into villi & form a core of loose connective tissue

Question 12

describe Tertiary Chorionic Villi formation

Answer 12

• this is day 21
  The embryonic vessel begin to form in the embryonic mesoderm
  This villi grows towards the decidua basalis (of the maternal uterus) and spread across forming a cytotrophoblasts shell
  This villi branches outwards to provide a large surface area of placenta

*cytothrophoblastic shell is an external layer of cytothrophoblasts that have hrown to the maternal suface of the placenta

Question 13

describe the establishment of placental circulation

Answer 13

To accomodate the increased blood flow to the placentathe maternal spiral arteries undergo remodelling to create low resitsce, hgh blood flow conditions
Cytotrophoblasts cells invade the maternal spiral arteries to mek vessels larger & optimise blood flow to the placenta

Question 14

when is placental circuatio fully functional?

mturation of placental circulation

Answer 14

by the end of the first trimester

Question 15

describe the materna circulation

maturation of palcental circulation

Answer 15

• Maternal blood fill the intervillous spaces of the placenta as they entre through spiral arteries (of the uterus)
• The blood spreads through chorionic villi where nutrients + gas exchange occurs
  Via this gas exchange deoxygenated blood moves/ diffuse from foetal circulation to maternal circultion

deoxygenated blood w/ CO2

Question 16

describe the foetal circulation

maturation of placental circulation

Answer 16

• CO2 is transported to the placenta through umbillical arteries
• The blood passes through capillaries in the chorionic villi
• O2 diffuses down the concentration gradiant moving from an O2-rich environment (maternal blood) to lower o2 environmnet (foetal blood)
• The foetal oxygenated blood travels through the umbilical vein to supply oxygen to the foetus

oxygen diffuses from maternal blood into foetal blood

Question 17

what are the two key mechanisms involved in establishing placental circulation

Circulatio Mechanism

Answer 17

1. Vasculogenesis (from day 18-35 post-conception)
   The de novo formation of blood vessel within the developing chorionic villi
2. Angiogenesis (from early as day 21 post-conception)
   The physiological process that involves the growth of new blood vessels from pre-existing vessels –> this continues to dvelop to increase the vascular network & support the growth of the foetus

Question 18

what is the placental vascular network development controlled by?

circulation mechanism

Answer 18

it’s controlled by vasculogenic and angiogenic ptocesses throughout pregnancy

Question 19

what is the circulation mechanism regulated by?

circukation mechanism

Answer 19

agniogenic factors (produced by the placenta)

Question 20

what are key regulators of angiogenetic factors

angiogenetic factors

Answer 20

regulators include proteins such as:
* Vascular Endothelial Growth Factor (VEGF)
promotes the growth and permeability of blood vessel
* Placental Growth Factors (PGF)
enhances angiogenesis by stimulating VEGF receptors
* Fibroblast Growth Factor (FGF)
contrinbute to the regulation of blood vessel formation

Question 21

describe the placenta by 10-12 weeks gestation

the maturing placenta

Answer 21

• by the end of the 1st trimester, the placenta is well established
• the chorionic villi are sourrounded by maternal blood to allow the functions of the placenta between mother & foetus
• the mature placenta is - a flattened disc, 20 cm in diameter and 2.5 cm thick

Question 22

what is the chorionic plate?

Answer 22

the foetal side of the placenta

Question 23

what is the chorionic plate composed of?

Answer 23

• Amnion
  the innermost membrane that sorrounds the foetus and the amniotic fluid
• Chorion
  a layer that contains mesodermal tissue & supports the chorionic villi
• Blood vessels
  The foetal blood vessel that branch into the chorionic villi that extend into the intervillous spaces
  Forms a boundary between the foetal side & maternal side of the placenta

Question 24

what is the basal plate

Answer 24

the maternal side of the placenta

Question 25

describe the basal plate

Answer 25

* it's where the chorionic villi attach * facilitates maternal-ffetal blood supply * contains maternal spiral arteries that supply blood to the intervillous spaces

Question 26

what is the placental barrier/ membrane?

Answer 26

it's the multilayered functional interface where maternal-foetal exchange occurs within chorionic villi ## Footnote *but it's semi-permeable (don't get confused by the word 'barrier') as it aloows sumbsances to pass through e.g. alcohol*

Question 27

what is the amniotic fluid?

Answer 27

a fluid substance contained within the amniotic membrane

Question 28

describe the production of amniotic fluid

Answer 28

* produced early 1st trimester (around 6 weeks) * originates from maternal plasma * diffuses from maternal side to the amnionn & into the amniotic sac * consists mainly of wwater, nutrients and electrocytes

Question 29

describe the development of amniotic fluid

Answer 29

* Asfoetal kidneys start to develop & funtion (weeks 12-14) the foetus begins producing **urine**, which becomes an amniotic fluid component * Foetal **swallowing** & **urination** contributes to maintaining the balance of amniotic fluid volume

Question 30

what are the functions if amniotic fluid?

Answer 30

* **Protection** Provides physical cushioning from external pressure or injury Carrier antibacterial properties that helps protect the foetus from infection * **Temperature regulation** (in utero) acts as an insulating buffer * **Facilitates movement** Enables foetus to move freely (supporting their muscle and skeletal development) * **Fluid balance** as itv allows the foetus to swallow & urinate back into the amniotic fluid * **Lung development** through inhalation and exhalation of amniotic fluid, making the brathing movement ## Footnote also ... produces & releases hormones provides nutrition

Question 31

what influences foetal growth & development? | placental nutrition

Answer 31

maternal nutrient availability & the ability of the placenta to transport the nutrients

Question 32

list some (placental) nutrients | Placental nutrition

Answer 32

* glucose * amino acids * fatty acids * vitamins & minerals

Question 33

in terms of placental nutrition, what can impact short-term & long-term offspring health outcomes? | placental nutrition

Answer 33

inadequate or excessive nutrient intake

Question 34

describe gas exchange in the placenta | transport

Answer 34

* the placenta is the only facilitator of oxygen for the foetus * foetal heart best has a higher affinity for O2 to allow foetal oxygenation * O2 diffuses via the placenta & CO2 diffuse into maternal blood for excretion

Question 35

describe waste removal in the placenta | transport

Answer 35

* removes metabolic waste products *e.g. urea & creatin* from the foetus and maternal bloostream * removed from maternal bloodstream through kidneys

Question 36

describe immune protection in the placenta | placental protection

Answer 36

* selectively allows maternal antibodies to pass the foetal bloodstreams * provides *passive immunity*, offering protection against infection from maternal exposure

Question 37

describe the barrier function of the placenta | placental protection

Answer 37

* semi-permeable barrier - selectively allows substances to cross the placenta while blocking others via export pumps * export pumps like **Multidrug Resistance Protection 1** (MDR1) & **Breats Cancer Resistance Protection** (BCRP) control substances passing into foetal circulation + export unwanted/ harmful molecules into maternal blood * produces enzymes to break down maternal hormone (e.g. cortisol) to protect the foetus from excessive exposure * not effective in all cases *e.g. alcohol, thalidomide, anticonvulsants warfarin*. Some viruses casue transplacentalinfection *CMV, Rubella, Polio, Vacinella*

Question 38

describe hormonal production in the placenta | hormone production

Answer 38

produces & secrets hormones/ growth factors to maintain preg + foetal development + preparation for bitrth & feeding

Question 39

list the hormones produced by the placenta | hormone production

Answer 39

* Human Chorionic Gonadorophin (hCG) * Progesterone * Oestrogen * Relaxin

Question 40

describe the placental hormone Human Chorionic Gonadotrophin (hCG) | hormonal production

Answer 40

* produced by syncytiotrophoblast * detectable 24-48 hrs of implantation * peaks at 8-12 weeks * prevents menstruation by ptolongig corpus luteum * associated with pregnancy sickness

Question 41

describe the placental hormone progesterone | placental hormone

Answer 41

* supporte embryo implantation * prevents premature uterine contractions * maintains endometrium (uterine linig) * strenghten pelvic floor muscles for labour

Question 42

describe placental hormone oestrogen | placental hormones

Answer 42

* suports the increase in uterine blood flow * supports growth (e.g. uterus, mammary glands) * supports milk duct development * activated & regukates other hormone production

Question 43

describe the placental hormone relaxin | placental hormone

Answer 43

* relaxes blood vessels, thus increasing blood flow * relaxes joints and ligaments * inhibits uterine contractions to prevent premature birth

Question 44

how can the placenta be best described as? | placenta at term

Answer 44

it's a foetalmaterna organ ## Footnote *this is bc the placental grows @ develops w/ the foetus to allow materno-foetal exchange*

Question 45

describe basal plate | placenta at birth

Answer 45

* has 10-40 cotyledons (lobes) *<-- these are elevated regions* * the cotyledons contain villous trees * divided by sulci (furrows) * weighs approx 500g * diameter of approx 15-20 cm * thickness of approx 2-3 cm

Question 46

why is the placenta examined? | placenta examination

Answer 46

* gives an idea of the uterine environment * assessed for completness * may indocate the health of the mother/ baby * findings may be cause for extra observation

Question 47

descriebe the steps to examining the placenta | placenta examination

Answer 47

* lay on flat surface w/ the **foetal side** facing up * note size, shape, smell, colour and completness * assess cord-note thickness (2.0-2.5), colour, lenght, vessels (3), Whartons Jelly, Insertion (central) * observe irregularities * observe membrane and assess for completness *(there shoukd be 1 single hole)* * Spred membrane out and look for extra vessels, lobes or holes * separate amnion from chronion to ensure both are present * turn over, inspect **maternal side** * assess the cotyledons (elevated regions that contains villious trees), divided by sulci (furrows) * assess completness * observe for any abnormalities: succenturiate lobes missing cotyledons fatty deposits infractions ## Footnote when examining: weigh swab take samples if required

Question 48

how is the placenta examined? | placental examination

Answer 48

* gain consent & gather equipment (lighting, placenta bag, specimen jar/ bag scissors) * lay on flat surface, foetal-side facing up * note size, shape, smell, colour & completness

Question 49

what causes calcification of the placenta?

Answer 49

* Deposition of excessive calcium phosphate minerals This can harden the placental tissues

Question 50

how can calcification of the placenta affect the placenta

Answer 50

* impair the normal expansions + functinons of th chorionic villi * obstruct/ narrow the spiral arteries * reduce placenta blood flow (and s oxygenation)

Question 51

what are the risk factors for calcifieed placenta?

Answer 51

* smoking * PIH (hypertension) * pre eclampsia

Question 52

what is rigged membranes?

Answer 52

when placenta membaranes are incomplet or are separated (@ birth)

Question 53

what can rigged membranes cause?

Answer 53

it can cause the risk of placental retention (@ birth)

Question 54

what are the risks of placenta retention due to rigged membrane (@ birth)?

Answer 54

* bleeding * infection * excessive pain * sepsis

Question 55

what is a succenturiate lobe?

Answer 55

one or more accessory placental lobe, which develops on the membrane

Question 56

what is succenturiate love associated with?

Answer 56

* abnormal vascualr development * retained placenta

Question 57

what can succenturiate lobe cause?

Answer 57

PPH (postpartum hemmorrhage) infection

Question 58

what are the risk factors to developing succenturiate lobe?

Answer 58

* multipary * uterien abnormalities

Question 59

after examinig the placenta, if abnormal what is done?

Answer 59

it's kept for turther inspection and refferred as appropriate ## Footnote examination should be discussed & documented

Question 60

after examining the placenta, if normal what is done to it?

Answer 60

* placed in a bag and disposed of (following the Trust plicy) ## Footnote examination should be discussed and documented

Question 61

(after an examination) why are clots of from the placenta retained?

Answer 61

ton assess QBL (quantitative blood loss)