HISTOLOGY REVIEW Connective Tissues

1. HISTOLOGY REVIEWConnective Tissues Dr. Tim Ballard Department of Biology and Marine Biology

2. Areolar connective tissue Mesentery spread – Verhoeff – 4xobjective 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. This is a loose connective tissue. See how widely spread the fibers and cells are separated from one another.

3. Areolar connective tissue Mesentery spread – Verhoeff – 10xobjective 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

4. Areolar connective tissue Mesentery spread – Verhoeff – 40xobjective The loose arrangement of the fibers gives plenty of room for the wandering cells to pass through the tissue. 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

5. Adipose tissue Adipose tissue – section – H&E – 4xobjective 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. This honey-combed appearance is characteristic of adipose tissue.

6. Adipose tissue Adipose tissue – section – H&E – 10xobjective The arrowheads point out individual cells.

7. Adipose tissue Adipose tissue – section – H&E – 40xobjective 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. Black arrowhead – nucleus of an adipocyte; blue arrowhead – capillary within the adipose tissue.

8. Reticular connective tissue Spleen – section – silver – 10x objective 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. Reticular tissue consists of very small collagenous fibers. They are visualized as brownish-black fibers with the silver stain.

9. Reticular connective tissue Spleen – section – silver – 40x objective lymphocyte Arrowheads point out reticular fibers. The rounded nuclei are of lymphocytes residing in the organ.

10. Reticular connective tissue Lymph node – section – H&E – 40xobjective Notice that with the H&E stain individual reticular fibers are difficult to visualize. The nuclei are those of lymphocytes. This slide isn’t in our set.

11. Hyaline cartilage Trachea – cross section – H&E – 10xobjective 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. The bar with arrows indicates the thickness of the plate of hyaline cartilage located in the wall of the trachea.

12. Hyaline cartilage Trachea – cross section – H&E – 40xobjective lumen The matrix is rich in collagen (giving it a pink color) and cartilage-specific molecules called chondroitin sulfates (giving it a purplish color). Arrowheads indicate chondrocytes, the cell type of cartilage. The cells sit in spaces called lacuna and are surrounded by the matrix they have secreted.

13. Elastic cartilage Mouse ear – section – Verhoeff – 10xobjective lumen 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.

14. Elastic cartilage Mouse ear – section – Verhoeff – 40xobjective 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.

15. Fibrocartilage Pubic symphysis –section – Mallory’s – 4xobjective All of the bluish fibers are collagen. Notice all of the rounded cells (chondrocytes) sitting inside lacunae.

16. Fibrocartilage Pubic symphysis –section – Mallory’s – 10xobjective All of the bluish fibers are collagen. Notice all of the rounded cells (chondrocytes) sitting inside lacunae (arrowheads).

17. Fibrocartilage Pubic symphysis –section – Mallory’s – 40xobjective lacuna Chondrocytes (arrowhead) within its lacuna; collagen fibers (arrow) end