Connective Tissue-Cartilage Laboratory

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MICROSCOPIC ANATOMY

CONNECTIVE TISSUE & CARTILAGE LABORATORY

Daniel DjakiewDepartment of Biochemistry and Molecular & Cellular Biology

C406C, Medical/Dental Building

Slide 2 Embryonal Connective Tissue

This slide of the embryonal connective tissues demonstrates stellate shaped cells which are typical of embryonic connective tissue. These are multipotent cells which can specialize into different kinds of connective tissue cells. The processes of one cell seem to form a network with the processes of the neighboring cells. The amount and distribution of the fibrillar and amorphous components of the ground substance cannot be observed.

Slide 3 Mesenchymal Cells

H & E: Embryonic connective tissue is composed of undifferentiated and partially differentiated mesenchymal cells with a spindle shaped morphology scattered between extensive extracellular matrix.

Slide 4 Fibroblasts

This preparation demonstrates spindle or aster shaped fibroblasts in the actual act of elaborating collagen material. Notice the slender collagen fibers in the general ground substance.

Slide 5 Loose Connective Tissue

This slide demonstrates loose connective tissue stained with H&E. Notice the predominantly stained collagen fiber bundles lying loosely and irregularly in a faintly stained ground substance. Notice the spindle-shaped or elongate fibrocytes with deep staining nuclei and faint cytoplasm. Also observe in the center of the slide few fat cells whose fat has been dissolved out during preparation of the tissue. A few blood capillaries can also be seen.

Slide 6 Connective Tissue Cells

This slide demonstrates various types of connective tissue cells. Notice long slender fibrocytes (labeled a) and macrophages (labeled b) having eosinophilic cytoplasm. A round plasma cell (labeled c) with an eccentric nucleus and lightly basophilic cytoplasm is also present but is seen to better advantage in the next slide. Notice many lymphocytes (labeled d). A lymphocyte has a densely staining large nucleus and a meager cytoplasm.

Slide 7 Plasma Cells

This slide demonstrates plasma cells which elaborate the circulating antibodies in the body. Notice the characteristic cart-wheel arrangement of chromatin in the nucleus which is eccentric in position. The cytoplasm shows a light basophilia indicating protein synthesis.

Slide 8 Plasma Cell, EM

Electron micrograph of a plasma cell. Note the eccentrically located nucleus (1) containing heterochromatin (2) which gives rise to the characteristic cart-wheel appearance of the nucleus. Note the abundance of rough endoplasmic reticulum (3) interspersed with Golgi apparatus (4) and mitochondria (5).

Slide 9 Macrophages

Macrophages are phagocytic cells that act as scavengers on foreign bodies, dead cells and other tissue debris. They are present in considerable numbers in loose connective tissue. This slide demonstrates a number of macrophages (shown at the arrows). Notice an oval, often dented nucleus and a pale eosinophilic cytoplasm.

Slide 10 Macrophages

Macrophages cannot be identified easily in normal connective tissue. But when stimulated by an infection or an injury, they form a conspicuous cellular component of connective tissues. This slide demonstrates several macrophages that have phagocytozed large amounts of India ink.

Slide 11 Adipose Tissue

H & E: Adipose tissue is a prevalent cellular component of connective tissue such as within the hypodermis. Each adipose cell (A) is filled with a large secretory vacuole that forces the remaining cytoplasm and nucleus to the periphery.

Slide 12 Fat Cells

Since lipid or fat is dissolved in sections prepared with routine technical procedures, the selective staining of lipids requires either frozen sections or freeze-dried sections. In this slide, the dye Oil Red O has been used to demonstrate the lipids in a frozen section.

Slide 13 Fat Cells

This slide also demonstrates adipose connective tissue cells. Here the lipids are oxidized to a black color by treatment with osmium tetroxide. The lipid is extracted from the cells in the center of this slide.

Slide 14 Mast Cells

This preparation demonstrates two mast cells that are degranulating in the connective tissue. Mast cells are generally present peripheral to small blood vessels where they seem to help in the maintenance of normal haemostasis. A mast cell is a large cell with a spherical nucleus. Its cytoplasm is packed with granules that contain heparin and histamine. Heparin is a sulphated mucopolysaccharide and acts as an anticoagulant. Heparin present in the granules is stained purple in this slide with the dye, aldehyde fuchsin. Histamine, the other component of the cyoplasmic granules, increases capillary permeability and causes vasodilation.

Slide 15 Mast Cell, EM

Electron micrograph of a mast cell with short microvilli (4) within the stroma of the submaxillary gland. The heterochromatic nucleus (1) is surrounded by a cytoplasm filled with large membrane bound secretory granules (3) which contain heparin (anticoagulant) and histamine (a vasodilator).Collagen fibrils (2) are prevalent.

Slide 16 Leukocytes

H & E- Leukocytes constitute another cellular component of connective tissue. Shown here are neutrophils (arrow), a monocyte with the bean shaped nucleus, and a lymphocyte in which the nucleus occupies most of the cells volume.

Slide 17 Dense Irregular Connective Tissue

H & E: The dermis provides an example of dense irregular connective tissue. Collagen bundles (stained pink) are predominate and occur in several orientations. Fibroblasts can be observed between the collagen bundles.

Slide 18 Loose Connective Tissue, EM

This electron micrograph depicts loose connective tissue of the lamina propria within the small intestine. The overlying simple columnar epithelium is lined by a brush border of microvilli (1) and contains an even row of nuclei (2). Other features include a basal lamina (3); lumen of a venule 4) and plasma cells (5).

Slide 19 Fibroblasts & Collagen, EM

Electron micrograph of fibroblasts (1) with heterochromatic nuclei (2) and rough endoplasmic reticulum (3) synthesize tropocollagen (4), which is secreted and deposited as collagen fibrils shown in longitudinal section (5) and cross section (6) within the dermis.

Slide 20 Dense Irregular Connective Tissue

Dense connective tissues are characterized by the close packing of their fibers, a few fibrocytes and very limited amount of amorphous ground substance. This preparation demonstrates dense irregular connective tissue. Notice closely packed collagen bundles oriented in different directions. The nuclei of fibrocytes can also be seen.

Slide 21 Dense Regular Connective Tissue

This preparation of tendon serves as an example of dense regular collagenous connective tissue. Notice the regular compact arrangements of collagen fibers running in one direction. Also observe a few linearly oriented nuclei of the fibrocytes lying compressed between the fibers.

Slide 22 Dense Regular Elastic Connective Tissue

This slide demonstrates dense regular elastic connective tissue in a ligament. The elastic fibers which lie in parallel arrangement are stained red-purple with aldehyde fuchsin while the delicate connective tissue fibers occupying intervening spaces are stained green with the dye, fast green.

Slide 23 Reticular Fibers

Silver nitrate stain: Reticular fibers are common in lymph nodes. The reticular fibers (black stain) are secreted by reticular cells. Note the blood vessel (arrow).

Slide 24 Hyaline Cartilage

The following slides will introduce you to the study of cartilage, a special type of connective tissue in which the amorphous ground substance predominates over the cellular and fibrous components. This slide demonstrates hyaline cartilage stained with H&E. The cartilage cells called chondrocytes can be seen in the lacunae, which lie in an amorphous ground substance. The perichondrium, the dense connective tissue layer from which new chondrogenic cells proliferate and cause appositional growth of cartilage is located on the right-hand side of this slide, next to the loose connective tissue.

Slide 25 Cartilage

H & E: Cartilage consists of an amorphous ground substance containing chondrocytes within lacunae surrounded by territorial matrix. Note the perichondrium that is characteristic of appositional growth of cartilage.

Slide 26 Articular Cartilage

This slide demonstrates articular cartilage which serves as another example of hyaline cartilage. Notice a superficial layer of flattened cells lining the articular surfaces in the center of the slide and inner layers of chondrocytes that increase in size toward the deeper regions of the cartilage. Note that articular cartilage is devoid of perichondrium.

Slide 27 Interstitial Growth of Cartilage

This preparation demonstrates interstitial growth, by mitosis, of cartilage. Notice nests of chondrocytes in multiples of two, three or more located in the lacunae. They are surrounded by a dense amorphous ground substance which is stained deep red and forms the territorial matrix. The general ground substance stains lightly.

Slide 28 Elastic Cartilage

This is a preparation of elastic cartilage stained with iron hematoxylin and alcian blue. Notice the branching darkly stained elastic fibers that form a network in the ground substance around the chondrocytes. The elastic fibers vary in thickness in different cartilages and are generally more closely packed in the interior of the cartilage.

Slide 29 Fibrocartilage

This slide of the fibrocartilage is from the intervertebral disc where support and tensile strength is desirable. The cartilage cells here are similar to other chondrocytes and occur in groups and rows.

Slide 30 Epiphyseal Growth Plate

The epiphyseal growth plate contains cartilage undergoing interstitial growth. Chondrocytes within the zone of proliferation (between lines) grow interstitially by mitosis.

Slide 31 Chondroblasts, EM

Electron micrograph of hyaline cartilage containing chondroblasts (1) showing nuclei (2), rough endoplasmic reticulum (3), Golgi apparatus (4), lipid (5), glycogen (6) and intercellular ground substance with collagen fibrils (7).

Slide 32 Chondrocytes, EM

Electron micrograph of hyaline cartilage containing chondrocytes (1) in lacunae (2) and showing nuclei (3), lipid (4), territorial matrix (5), and intercellular ground substance (6).

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