HISTOLOGY REVIEWHISTOLOGY REVIEWConnective TissuesConnective Tissues

Dr. Tim BallardDr. Tim Ballard

Department of Biology and Marine BiologyDepartment of Biology and Marine Biology

Mesentery spread – Verhoeff – 4x objective

This is a loose connective tissue. See how widely spread the fibers and cells are separated from one another.

Areolar connective tissueAreolar connective tissue

Verhoeff’s stain is used to visualize both collagen and elastin fibers in the same sample. Collagen fibers are pink while elastin fibers are purple-black.

Elastin fiber (black arrowhead); collagen fiber (blue arrowhead); the nuclei are of various cell types, some of which are permanent and others that wander through

Mesentery spread – Verhoeff – 10x objective

Areolar connective tissueAreolar connective tissue

The spaces between fibers and cells are filled with water-based ground substance.

Elastin fiber (black arrowhead); collagen fiber (blue arrowhead); the nuclei are of various cell types, some of which are permanent and others that wander through

Mesentery spread – Verhoeff – 40x objective

Areolar connective tissueAreolar connective tissue

The loose arrangement of the fibers gives plenty of room for the wandering cells to pass through the tissue.

Adipose tissue – section – H&E – 4x objective

This honey-combed appearance is characteristic of adipose tissue.

Adipose tissueAdipose tissue

The H-E stain requires a series of alcohol dehydration steps. As a result, the fat droplets within the cells are “washed out” of the sample. You are looking at the remainder of the cell.

Adipose tissue – section – H&E – 10x objective

The arrowheads point out individual cells.

Adipose tissueAdipose tissue

Adipose tissue – section – H&E – 40x objective

Black arrowhead – nucleus of an adipocyte; blue arrowhead – capillary within the adipose tissue.

Adipose tissueAdipose tissue

Adipocytes are said to have a “signet ring” appearance. Like a class ring, for example, the stone and engraving are on one side connected by a thin band wrapping around.

Spleen – section – silver – 10x objective

Reticular tissue consists of very small collagenous fibers. They are visualized as brownish-black fibers with the silver stain.

Reticular connective tissueReticular connective tissue

Reticular fibers are used to form the stroma or framework (think infrastructure) of some organs. For example, the spleen and lymph nodes are made by a meshwork of reticular fibers. Lymphocytes and macrophages then invade the organ and take up residence in the spaces.

Arrowheads point out reticular fibers. The rounded nuclei are of lymphocytes residing in the organ.

lymphocyte

Spleen – section – silver – 40x objective

Reticular connective tissueReticular connective tissue

Lymph node – section – H&E – 40x objective

Notice that with the H&E stain individual reticular fibers are difficult to visualize. The nuclei are those of lymphocytes.

Reticular connective tissueReticular connective tissue

Muscle-tendon intersection – section – H&E – 4x objective

With the H&E stain, skeletal muscle fibers ion this section are darker than the adjacent collagen fibers.

Dense regular connective tissueDense regular connective tissue

muscle

dense regular CT

The major feature you are looking for here is the presence of pink fibers, densely packed together, and all passing in the same plane, parallel to one another. The nuclei of the fibroblasts that make the fibers are fusiform in shape, lying between the fibers.

Using this objective you can see that the collagen fibers are all lying in parallel to each other, with fibroblast nuclei wedged in between the fibers.

Dense regular connective tissueDense regular connective tissue

Muscle-tendon intersection – section – H&E – 10x objective

muscle

dense regular CT

adipose cells

fibroblast nuclei

Using this objective you can see that the collagen fibers are all lying in parallel to each other, with fibroblast nuclei wedged in between the fibers.

Dense regular connective tissueDense regular connective tissue

Muscle-tendon intersection – section – H&E – 20x objective

muscle

fibroblast nuclei

Using this objective you can see that the collagen fibers are all lying in parallel to each other, with fibroblast nuclei wedged in between the fibers.

Dense regular connective tissueDense regular connective tissue

Muscle-tendon intersection – section – H&E – 40x objective

muscle

fibroblast nuclei

Dense regular connective tissueDense regular connective tissue

Muscle-tendon intersection – section – H&E – 40x objective

fibroblast nuclei

collagen fibers

bone

Another example of dense regular connective tissue. In some of the following slides, look for it.

Dense irregular connective tissueDense irregular connective tissue

The dermis is where we go to see the features of dense irregular connective tissues. Look for collagen fibers passing in multiple directions.

Skin – section – H&E – 4x objective

dermis

epidermis

The major feature you are looking for now is the presence of pink fibers, less densely packed together, and passing in multiple directions to resist tensile forces pulling from multiple directions.

Dense irregular connective tissueDense irregular connective tissue

Look at all the pink-stained collagen fibers. Can you see that they are passing in multiple directions?

Skin – section – H&E – 10x objectiveepidermis

Dense irregular connective tissueDense irregular connective tissue

In this section, you see collagen fibers passing in multiple directions. Can you visualize how they appear in three-dimensions?

collagen fiber passing

longitudinally

collagen fiber passing out of the screen at you

(in cross section)

collagen fiber cut obliquely

fibroblast nucleus

Skin – section – H&E – 40x objective

Elastic connective tissueElastic connective tissue

Aorta – section – H&E – 10x objective

The aorta is a large elastic artery. As such it has 40 – 70 layers of elastin fibers in its wall, with some collagen fibers, and fewer smooth muscle fibers interspersed between. All of these stain pink with H&E, so to visualize elastin fibers, histologists use the Verhoeff stain, which preferentially stains elastin purple-black. With the H&E stain, elastin fibers may be seen as bright pink, refractile fibers.

Elastic connective tissueElastic connective tissue

In this section, you see elastin fibers, purple-black, passing circumferentially around the aorta. See how they are coiled like a spring?

elastin fibers

Aorta – section – Verhoeff – 10x objective

Elastic connective tissueElastic connective tissue

Since this section has been counterstained with H&E, you can also see collagen fibers and smooth muscle cells (pink), although you can’t differentiate them.

elastin fibers

Aorta – section – Verhoeff – 40x objective

Trachea – cross section – H&E – 10x objective

The bar with arrows indicates the thickness of the plate of hyaline cartilage located in the wall of the trachea.

Hyaline cartilageHyaline cartilage

Ciliated pseudostratified columnar epithelium

The matrix of hyaline cartilage stains a light to dark bluish-purple with H&E. Newer matrix (immediately adjacent to the cells) stains darker than older matrix.

Arrowheads indicate chondrocytes, the cell type of cartilage. The cells sit in spaces called lacuna and are surrounded by the matrix they have secreted.

lumen

Trachea – cross section – H&E – 40x objective

Hyaline cartilageHyaline cartilage

The matrix is rich in collagen (giving it a pink color) and cartilage-specific molecules called chondroitin sulfates (giving it a purplish color).

Mouse ear – section – Verhoeff – 10x objective

Elastic cartilageElastic cartilage

Remember that the Verhoeff stain is specific of elastin fibers, staining them purple-black. There is a counterstain for collagen that is pink. This is a weakly-stained specimen. In a better preparation, the matrix would be stained intensely purple-black.

The bar with arrows indicates the thickness of a plate of elastic cartilage located in the ear, giving it structure and flexibiility.

Mouse ear – section – Verhoeff – 40x objective

Elastic cartilageElastic cartilage

Chondrocytes in elastic cartilage retain a fairly high mitotic rate throughout life . As result, there are many more cells than you would see in hyaline cartilage.

Chondrocyte within its lacuna (arrowhead). Although a weak stain, notice all of the dark-stained elastin fibers in the matrix.

Pubic symphysis –section – Mallory’s – 4x objective

All of the bluish fibers are collagen. Notice all of the rounded cells (chondrocytes) sitting inside lacunae.

FibrocartilageFibrocartilage

Pubic symphysis –section – Mallory’s – 10x objective

FibrocartilageFibrocartilage

All of the bluish fibers are collagen. Notice all of the rounded cells (chondrocytes) sitting inside lacunae (arrowheads).

lacuna

Pubic symphysis –section – Mallory’s – 40x objective

FibrocartilageFibrocartilage

Chondrocytes (arrowhead) within its lacuna; collagen fibers (arrow)end