Chapter Summary
I. EMBRYONIC CONNECTIVE TISSUE
A. Mesenchymal Connective Tissue
1. Cells
Stellate to spindle-shaped mesenchymal cells have processes that touch one another. Pale scanty cytoplasm with large clear nuclei. Indistinct cell membrane.
2. Extracellular Materials
Delicate, empty-looking matrix, containing fine reticular fibers. Small blood vessels are evident.
B. Mucous Connective Tissue
1. Cells
Fibroblasts, with their numerous flattened processes and oval nuclei, constitute the major cellular component. In section, these cells frequently appear spindle-shaped, and resemble or are identical with mesenchymal cells when viewed with a light microscope.
2. Extracellular Materials
When compared with mesenchymal connective tissue, the extracellular space is filled with coarse collagen bundles, irregularly arranged, in a matrix of precipitated jelly-like material.
II. CONNECTIVE TISSUE PROPER
A. Loose (Areolar) Connective Tissue
1. Cells
The most common cell types are fibroblasts, whose spin- dle-shaped morphology closely resembles the next most numerous cells, the macrophages. The oval nuclei of macrophages are smaller, darker, and denser than those of fibroblasts.Mast cells, located in the vicinity of blood vessels,may be recognized by their size, the numerous small granules in their cytoplasm, and their large, round, centrally located nuclei. Occasional fat cells resembling round, empty spaces bordered by a thin rim of cytoplasm may also be present. When sectioned through its peripherally squeezed, flattened nucleus, a fat cell has a ring-like appearance.
Additionally, in certain regions such as the subepithelial connective tissue (lamina propria) of the intestines, plasma cells and leukocytes are commonly found. Plasma cells are small, round cells with round, acentric
nuclei, whose chromatin network presents a clock face (cartwheel) appearance. These cells also display a clear, paranuclear Golgi zone. Lymphocytes, neutrophils, and occasional eosinophils also contribute to the cellularity of loose connective tissue.
2. Extracellular Materials
Slender bundles of long, ribbon-like bands of collagen fibers are intertwined by numerous thin, straight, long, branching elastic fibers embedded in a watery matrix of ground substance, most of which is extracted by dehydration procedures during preparation. Reticular fibers, also present, are usually not visible in sections stained with hematoxylin and eosin.
B. Reticular Connective Tissue
1. Cells
Reticular cells are found only in reticular connective tissue. They are stellate in shape and envelop the reticular fibers, which they also manufacture. They possess large, oval, pale nuclei, and their cytoplasm is not easily visible with the light microscope. The other cells in the interstitial spaces are lymphocytes, macrophages, and other lymphoid cells.
2. Extracellular Materials
Reticular fibers constitute the major portion of the intercellular matrix. With the use of a silver stain, they are evident as dark, thin, branching fibers.
C. Adipose Tissue
1. Cells
Unlike other connective tissues, adipose tissue is composed of adipose cells so closely packed together that the normal spherical morphology of these cells becomes distorted. Groups of fat cells are subdivided into lobules by thin sheaths of loose connective tissue septa housing mast cells, endothelial cells of blood vessels, and other components of neurovascular elements.
2. Extracellular Materials
Each fat cell is invested by reticular fibers, which, in turn, are anchored to the collagen fibers of the connective tissue septa.
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D. Dense Irregular Connective Tissue
1. Cells
Fibroblasts, macrophages, and cells associated with neurovascular bundles constitute the chief cellular elements.
2. Extracellular Materials
Haphazardly oriented thick, wavy bundles of collagen fibers, as well as occasional elastic and reticular fibers are found in dense irregular connective tissue.
E. Dense Regular Collagenous Connective Tissue
1. Cells
Parallel rows of flattened fibroblasts are essentially the only cells found here. Even these are few in number.
C O N N E C T I V E T I S S U E 79
2. Extracellular Materials
Parallel fibers of densely packed collagen are regularly arranged in dense regular collagenous connective tissue.
F. Dense Regular Elastic Connective Tissue
1. Cells
Parallel rows of flattened fibroblasts are usually difficult to distinguish in preparations that use stains specific for elastic fibers.
2. Extracellular Materials
Parallel bundles of thick elastic fibers, surrounded by slender elements of loose connective tissue, comprise the intercellular components of dense regular elastic connective tissue.
4 CARTILAGE AND BONE
CHAPTER OUTLINE
Graphics
Graphic 4-1 Compact Bone p. 88
Graphic 4-2 Endochondral Bone Formation p. 89
Tables
Table 4-1 Cartilage Types, Characteristics, and
Locations
Plates
Plate 4-1 |
Embryonic and Hyaline Cartilages. |
|
Human p. 90 |
Fig. 1 |
Embryonic hyaline cartilage |
Fig. 2 |
Hyaline cartilage. Trachea. |
Fig. 3 |
Hyaline cartilage |
Fig. 4 |
Hyaline cartilage. Trachea |
Plate 4-2 |
Elastic and Fibrocartilages p. 92 |
Fig. 1 |
Elastic cartilage. Epiglottis |
Fig. 2 |
Elastic cartilage. Epiglottis |
Fig. 3 |
Elastic cartilage. Epiglottis |
Fig. 4 |
Fibrocartilage. Intervertebral disc |
Plate 4-3 |
Compact Bone p. 94 |
Fig. 1 |
Decalcified compact bone. Human |
Fig. 2 |
Decalcified compact bone. Human |
Fig. 3 |
Decalcified compact bone. Human |
Fig. 4 |
Undecalcified ground compact bone. |
|
Human x.s. |
Plate 4-4 |
Compact Bone and Intramembranous |
|
Ossification p. 96 |
Fig. 1 |
Undecalcified ground bone. Human x.s. |
Fig. 2 |
Intramembranous ossification |
Fig. 3 |
Intramembranous ossification |
Fig. 4 |
Intramembranous ossification |
Plate 4-5 |
Endochondral Ossification p. 98 |
Fig. 1 |
Epiphyseal ossification center |
Fig. 2 |
Endochondral ossification l.s. |
Fig. 3 |
Endochondral ossification |
Plate 4-6 |
Endochondral Ossification p. 100 |
Fig. 1 |
Endochondral ossification |
Fig. 2 |
Endochondral ossification |
Fig. 3 |
Endochondral ossification x.s. |
Plate 4-7 |
Hyaline Cartilage, Electron Microscopy |
|
p. 102 |
Fig. 1 |
Hyaline cartilage (EM) |
Plate 4-8 |
Osteoblasts Electron Microscopy p. 103 |
Fig. 1 |
Osteoblasts from long bone (EM) |
Fig. 2 |
Osteoblasts (EM) |
Plate 4-9 |
Osteoclast, Electron Microscopy p. 104 |
Fig. 1a |
Osteoclast from long bone (EM) |
Fig. 1b |
Osteoclast (EM) |
Fig. 2 |
Osteoclasts. Human. |
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