placenta and the mammary gland rachel boggus boggusrl@email.uc.edu

Placenta and the mammary gland

Rachel BoggusBoggusrl@email.uc.edu

04/21/23 Free Template from www.brainybetty.com 2

Orientation to development of the placenta

• What happens to the stratum functionalis after implantation?

• What are these responses called? What is the endometrium now called?

Orientation to development of the placenta

• What happens to the stratum functionalis after implantation?– Cells enlarge and proliferate

decidual cells… synthesize prolactin and relaxin. Also becomes more highly vascularized

• What are these responses called? What is the endometrium now called?– Called decidual reaction,

endometrium called decidua

Selective elaboration of the chorion

• What does it mean to say that implantation is interstitial?

• What is the chorion frondosum?

• What is the chorion laeve?

Selective elaboration of the chorion

• What does it mean to say that implantation is interstitial?– Embryo completely embeds itself

into maternal decidual tissue

• What is the chorion frondosum?– Disk shaped region of chorion that

continues to develop

• What is the chorion laeve?– Regions of chorion near decidua

capsularis that regress

Development of Embryonic Circulation

• Develops from intraembryonic mesenchyme within the fetus

• These vessels are connected to two umbilical arteries and one umbilical vein.

What are the layers of the early placenta?

1) Epithelial layer of the amnion2) Extraembryonic mesenchyme3) Cytotrophoblast4) Syncytiotrophoblast5) Zone connecting villi and lacunae

(intervillous space)6) Syncytiotrophoblast7) Maternal decidua

Placenta

• What is the chorionic plate?

Placenta

• What is the chorionic plate?– Syncytiotrophoblast,

cytotrophoblast and underlying extraembryonic reticulum

Histology

• What are hofbauer cells?

• Where are they visualized?

• What are anchoring villi?

• What is the cytotrophoblastic shell?

Histology

• What are hofbauer cells?– Fetal macrophages

• Where are they visualized?– Within mesenchyme of the villi

• What are anchoring villi?– Stem villi that extend across the

intervillous space and connect with the decidual side

Red = chorionic plate; blue = stem villi

• If it reaches the other side it is an anchoring villi

BASAL PLATE = Green arrows: anchoring villi; cytotrophoblasts: blue arrow

Red Arrow: fibrinoid

Placenta

• What is the maternal side of the placenta called? What is it composed of?

• What is fibrinoid?

Placenta

• What is the maternal side of the placenta called? What is it composed of?– Basal plate, syncytiotrophoblast,

cytotrophoblast shell, and decidual tissue

• What is fibrinoid?– Extravillous cytotrophoblast cells

and maternal blood clots form this acidophilic extracellular matrix

Basal plate between arrows

Functions of syncytiotrophoblast

• What are cytotrophoblast cells like?

• What about the syncytiotrophoblasts? (hormones, appearance?)

• What maintains the corpus luteum?

Functions of syncytiotrophoblast

• What are cytotrophoblast cells like?– Stem cells—cuboidal, dispersed

chromatin, lack of elaborate organelles

• What about the syncytiotrophoblasts? (hormones, appearance?)– Very active cells—multinucleated,

microvilli, numerous pinocytic vesicles. HCG, estrogen, progesterone and prolactin

• What maintains the corpus luteum?– HCG

Red Arrow: cytotrophoblastBlue Arrows:

Syncytiotrophoblast

Maternal cotyledons

• What are they?

Maternal cotyledons

• What are they?– Formed by placental septa– Composed of core of decidual tissue

covered by cytotrophoblast and snycytiotrophoblast.

– Do not reach the opposing chorionic plate

Gas Exchange

• They love to ask questions about gas exchange so know this!

• Is there direct mixing of fetal and maternal blood?

• What are the layers that O2 must pass through initially?

Gas Exchange

• They love to ask questions about gas exchange so know this!

• Is there direct mixing of fetal and maternal blood? NO

• What are the layers that O2 must pass through initially?

1. syncytiotrophoblast2. cytotrophoblast3. basement membrane cytotropho..4. extraembryonic mesenchyme5. basement memb. Fetal endoth.6. fetal endothelial cells

What are the modifications as the placental matures?

• Clustering of the nuclei of syncytiotrophoblast syncytial knots

• Cytotrophoblast cells cease division (eventually not a continuous layer)

• Fetal bld vessels move closer to syncytiotrophoblast layer (eventually basal lamina of syncyts. fuses with fetal endothelium basal lamina.)

Syncytial knots (they LOVE these)

Umbilical cord

• What does the core develop from?

• What does the mesenchyme form?

• What covers the outside of the cord?

• What does the mature umbilical cord consist of?

Umbilical cord

• What does the core develop from?– Extraembryonic mesenchyme of

connecting stalk

• What else does it form?– Umbilical vessels

• What covers the outside of the cord?– The expanding amniotic membrane

• What does the mature umbilical cord consist of?– Outer epithelial covering (amniotic

memb.), inner mucus CT (wharton’s jelly), and umbilical vessels

Two arteries, one vein

Mammary Gland

• How many lactiferous ducts are in each breast?

• Remember that they each emerge as a separate opening

• What happens just under the epithelium?

• What happens to the epithelium?

Mammary Gland

• How many lactiferous ducts are in each breast? 15-25

• Remember that they each emerge as a separate opening

• What happens just under the epithelium?– They dilate to form lactiferous sinus

• What happens to the epithelium?– Strat squam at openingstrat

columnarstrat, cuboidalsimple cuboidal with myoepithelial cells

Alveolar system

• What are the milk components, how are they produced?

Alveolar system

• What are the milk components, how are they produced?– Milk proteins synthesized by RER

and secreted by exocytosis– Lipid droplets not membrane bound

and are released within plasma memb. TRUE apocrine secretion

– IgA moved by transcytosissIgA

Lobes, lobules, and CT

• Remember that each lactiferous duct drains one lobe

• Lobes divided into lobules • Within each lobule, intralobular

CT is loose with lots of plasma cells which make the IgA

• Lots of adipose tissue surrounds the lobes

Nipple and areola

• What is the epithelium?

• How is it different than the rest of the breast?

Nipple and areola

• What is the epithelium?– Stratified squamous epithelium

• How is it different than the rest of the breast?– Longer dermal papilla

Nipple; blue = smooth muscle; note large

dermal papilla

Mammary Gland Development

• Before puberty sparse duct system with little adipose tissue

• At puberty which hormones induce secondary sex characteristics in breasts?

• What are these changes?

Mammary Gland Development

• Before puberty sparse duct system with little adipose tissue

• At puberty which hormones induce secondary sex characteristics in breasts?– Estrogen, progesterone, growth hormone,

thyroid hormone, glucocorticoids

• What are these changes?– Inc. adipose, CT, and bld. Vessels,

enlargement of areola

Post-puberty

• Beginning of cycle—sparse glands and ducts. End—more elaborate and lumen apparent within alveoli

• Pregnancy—estrogen induces branching and progesterone cause alveolar development

• Towards the end of pregnancy secretory cells enlarge and distend with colostrum

• After birth produces milk rich in lipid• SECRETORY cells eosinophilic with clear

vacuoles from lipid droplet dissolution

Immature breast

Mammary gland of pregnant woman

Lactating mammary gland – fat droplets IN

Regressing mammary gland

Hormones and milk production

• What happens to prolactin levels throughout pregnancy?

• What happens to estrogen and progesterone at birth?

• What happens with suckling?

Hormones and milk production

• What happens to prolactin levels throughout pregnancy?– They gradually increase but the high levels of

estrogen and progesterone inhibit milk production

• What happens to estrogen and progesterone at birth?– The levels fall and prolactin begins to induce milk

production

• What happens with suckling?– Skin is enriched with free nerve endings and

Meissner’s corpuscles. Stimulation during suckling releases prolactin from ant. Pituitary and induces the release of oxytocin from the posterior pituitary

Breast Cancer

• Remember that tumors arise from epithelial cells of the lactiferous ducts

Image Review

• Identify the amnion which consists of a simple cuboidal epithelium and an underlying layer of connective tissue.

• stem villi originating from the chorionic plate. They are filled with mesenchyme and lined by the two layers of trophoblast cells. The inner layer, the cytotrophoblast, divides and gives rise to the outer layer, the syncytiotrophoblast.

Mature Placenta

• The cytotrophoblast has disappeared and there is now one layer of syncytiotrophoblast. In places, the cytoplasm has thinned and the nuclei have accumulated in groups and clusters. These are called SYNCYTIAL KNOTS.

• Some of the villi show acellular pink-staining material called FIBRINOID which covers the surface.

• Also, in mature placental villi are many more capillaries that lie closer to the surface.

• Look at the maternal side of the placenta, where ANCHORING VILLI can be seen embedded in uterine epithelia. The DECIDUAL BASALIS with the DECIDUA cells are found in the endometrium.

Note anchoring villi on right

The cord

All them breasts inside that shirt

• In the immature mammary gland, there is a lot of connective tissue around the glandular cells

immature

• Lots of CT, not a lot of glands

Immature again

• mammary gland of pregnant woman show little intralobular connective tissue and much glandular tissue

Mammary gland of pregnant woman: no lipid in cells!

vs. lactating • A lot of gland, not a lot of CT and

LIPID IN THE CELLS (pregnant but not lactating does not have this)

lactating

placenta and the mammary gland rachel boggus boggusrl@email.uc.edu

regressfree template

decidual sidefree template

chorion frondosum

chorion laeve

decidual cells

regions of chorion

anchoring villi

hofbauer cells

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