Types of Connective Tissue: Embryonic Connective Tissues
mesenchymal connective tissue
) is found in
the developing structures in the
. It contains scat-
, which have
irregular, star or spindle shapes and pale-stained cytoplasm.
These cells exhibit
, which often give
the cells a stellate appearance. Mesenchymal cells are rela-
tively unspecialized and are capable of
different cell types in mature tissue cells, such as cartilages,
bones, and muscles.
Embryonic red blood cells
can be seen
in this specimen. These blood cells contain a nucleus in each
cell; this is characteristic of their immature state (anucle-
ated red blood cells are characteristic of the mature state
and are found in adult tissues). Interestingly enough, some
vertebrates, such as frogs and chickens, have nucleated red
blood cells in the adult state.
Mucous connective tissue, umbilical cord.
Toluidine blue stain,
An example of
mucous connective tissue
that has an abun-
dance of a
with some F
ne aggregates of col-
bers and stellate-shaped
is shown. It is
found in the umbilical cord and subdermal connective tis-
sue of the embryo. Mucous tissue is a major constituent of
the umbilical cord, where it is referred to as
This type of connective tissue does not differentiate beyond
this stage. In this example, the viscous ground
been stained with a special stain to reveal
and large stellate-shaped
chymal cells) predominate in the mucous tissue.
Embryonic red blood
Pathological Terms for Connective Tissue
: An itchy skin eruption, also known as
, characterized by wheals with pale interiors and well-deF
margins, often the result of an allergic response to insect bites, foods, or drugs (±ig. 4-3C).
: Itching of the skin due to a variety of causes including hyperbilirubinemia and allergic and irritant contact condi-
tions (±ig. 4-3C).
: An abnormal liver condition characterized by diffuse nodularity, due to F
brosis and regenerative nodules of
hepatocytes; frequent causes are alcohol abuse and viral hepatitis (±ig. 4-19C).
: Yellow staining of the skin, mucous membranes, or conjunctiva of the eyes caused by elevated blood levels of
the bile pigment bilirubin (±ig. 4-19C).
: A disorder that prevents the normal clotting process of blood; causes may be acquired, such as hepatic dys-
function, or congenital, such as decreased clotting factors, as seen in inherited conditions like hemophilia (±ig. 4-19C).
: Irreversible cell changes that occur as a result of cell death (±ig. 4-20C).