Reticular connective tissue
Reticular connective tissue consists of reticular cells and the network of
reticular fibres formed by them. Most connective tissues contain reticular
fibres, but only in reticular connective tissue are they the dominant fibre
type.
In a number of tissues and organs, reticular
connective tissue forms the structural framework in which the cells of the
organ are suspended. The open meshwork of fine fibres is particularly
useful in tissues and organs in which diffusion and / or cell movements are
functionally important
, for example, in the liver, lymph
nodes and the spleen.
Adipose tissue
Adipose tissue is essentially loose connective tissue containing large
numbers of adipocytes. There are two types of adipose tissue, which derive
their names from the colour of the tissue (white or brown) and the number of
lipid droplets found in the adipocytes.
- Adipocytes of white, unilocular adipose tissue contain one large
lipid droplet.
- Adipocytes of brown, multilocular adipose tissue contain many
lipid droplets.
White adipose tissue does not only function in the storage of lipids. For
example, in the palms of the hands, on the plantar surface (sole) of the feet
and in the gluteal region (buttocks) it has a structural, cushioning function.
In these regions, accumulations of adipocytes are surrounded by strong
connective tissue fibres. Also, the distribution of white adipose tissue is
different in males and females and is part of the secondary sexual characteristics.
The storage and mobilisation of lipids does require quite some metabolic
activity of the tissue. Consequently, adipose tissue has a rich supply of
capillaries.
Brown adipose tissue occurs mainly during development and may account for 2
- 5 % of the body weight in a newborn. In adult individuals most of the brown
fat has further differentiated into white fat. Adipocytes in brown fat contain
plenty of mitochondria. A very rich capillary supply and the cytochromes found
in the mitochondria give the tissue its characteristic colour. A protein (
UCP-1 or thermogenin) found in these mitochondria
decouples the oxidation of fatty acids from the generation of
ATP.
Instead, these cells generate heat.
The location of the brown fat reflects its heat-generating
function. It is located in the axilla (armpits), between the shoulder blades,
in the region of the neck and along large blood vessels. The heat generated by
the brown fat warms the blood which supplies nearby organs or which re-enters
the trunk from the limbs.
white
adipose tissue: sections of skin - H&E, trichrome, van Gieson
Section are rarely prepared to show just white adipose
tissue. The hypodermis, i.e. lightest and loosest appearing layer, of skin
sections will typically contain large areas of adipose tissue. Other good
candidates are bone sections which contain yellow bone marrow or sections of
lymph nodes which are often embedded in adipose tissue. Small spots of adipose
tissue should be present in many other sections.
brown adipose tissue:
sections of brown adipose tissue or kidney - trichrome, H&E
Brown adipose tissue is often located in the connective
tissue close to the renal hilus or in the renal sinus of sections which contain
the entire kidney of small laboratory animals. Look for an indentation in the
outline of the kidney, which corresponds to its hilus.
Thick Skin -
H&E
In well-preserved thin sections, the adipocytes form a
mosaic of rounded or slightly angular white tiles, which correspond to the
locations of the lipid droplets, separated from each other by darker seams,
which correspond to the cytoplasm of the adipocytes and the sparse connective
tissue components between them. Because of the large size of the adipocytes
you will only rarely see it "typical" signet ring-like appearance
of the cells.
Although the tissue my be a little distorted, thicker sections give a good
three dimensional feel of the adipose tissue. The cytoplasmic rims of the
adipocytes form thin veils which enclose the open spaces which were occupied
by the lipid droplets. Oval adipocyte nuclei are often located close to the
corners at which the adipocytes meet.
Draw two or three adipocytes at high magnification and a
survey image which illustrates the appearance of adipose tissue at low
magnification.
|
|
Kidney
- trichrome
In the renal sinus, islands of brown adipose tissue are often surrounded by
white adipose tissue, which emphasises the different appearances of the two
tissue types. In brown adipose tissue, the nuclei of adipocytes are round and
located more or less centrally in a cytoplasm which, after the extraction of
lipids during tissue preparation, looks very frothy. Cell borders can be
difficult to identify. Capillaries are very frequent.
Sketch the appearance of the brown adipose tissue. Contrast
the characteristic features of white and brown adipose if both types are
present side by side.
|
![thumbnail]( "Reticular connective tissue")
Title:
Reticular connective tissue
by:
om
at
2013-02-15T02:54:00+07:00
Rating: 4.8
of 5 Reviews
Reticular connective tissue