91. Resting mammary gland (HE)92. Lactating mammary gland (HE)

93. Umbilical cord (HE)94. Placenta (HE)

95. Chicken embryo (HE)

The mammary gland consists of 15 to 20 lobes,each of which is an individual conpound alveolar gland with its own lactiferous duct opening onto the surface of the nipple.The interlobar stroma is dense connective tissue and varying amount of fat.Within each lobe, similar interlobular connective tissue bands courses between lobules.

In an inactive gland, connective tissue is aboundant and and glandular elements are minimal.

Adipose tissue

lobule

Dense interlobular connective tissue

A lobule contains groups of small tubules lined with cuboidal or low columnar epithelium.These look like ducts and usually remain in this state as long as the gland is inactive.The tubules are embedded in loose cellular connective tissue, the intralobular connective tissue. Surrounding this is the dense interlobular connective tissue and fat.

lobule

Interlobular connective tissue

Intralobular connective tissue

Glandular tubules

The mammary gland is fully developed in lactation.The lobules are filled with alveoli.Their lumens contain milk secretion. The amounts of the connective tissue stroma and adipose tissue, relative to the parenchyma decrease considerably.

Interlobular connective tissuelobules

Milk is produced by the epithelial cells of the alveoli and accumulates in their lumens and inside the lactiferous ducts.The secretory cells become low cuboidal and their cytoplasm contains spherical lipid droplets of various sizes.

Interlobular connective tissue

Milk secretion

Lipid droplets

The umbilical cord connects the embryo/fetus to the placenta.It is covered by simple cuboidal epithelium of the amnion.It contains the umbilical vessels:2 umbilical arteries and 1 umbilical vein.These vessels are embedded in Wharton s jelly (mucous tissue).

One of the umbilical arteries

Amniotic epithelium

Wharton s jelly

The cells of the Wharton s jelly stain slightly basophilic.They have processes connecting with each other. The aboundant jellylike ground substance is rich in hyaluronic acid.The Wharton s jelly contains only a few fibers.

cells

It consists of a fetal part formed by the chorion, and a maternal part, formed by the decidua basalis.Fetal portion (chorion):It consists of the chorionic plate and the chorionic villi arising from it.The chorionic villi may be either free or anchored to the decidua basalis.The surfaces of the villi are bathed with maternal blood (intervillous sace) from the lacunae of the basal decidua.

Epithelium of the amnion

Chorionic plate

Chorionic villi

Base of villous stemm

The maternal portion comprises the basal plate or decidua basalis and its septal projections (placental septa) that form incomplete separations between individual cotyledons.

Decidua basalis

Intervillous space with maternal blood

Chorionic villi

Chorionic villi

Chorionic plate

Trophoblast of the chorion

Intervillous space

Chorionic villi

Branches of umbilical vessels with fetal blood

Intervillous space containing maternal blood

Extraembryonic connective tissue (mesenchyme)

Syncytial trophoblasts

Placental barrier

cytotrophoblast

Fetal blood

Intervillous space

ectoderm

endodermnotochord

Neural tube

somite

Intraembryonic coelom

Somatic mesoderm

Splanchnic mesoderm

Intermediate mesoderm /

nephrogonotom