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CONNECTIVE TISSUE

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Title: CONNECTIVE TISSUE


1
CONNECTIVE TISSUE
  • Connective tissue is composed of cells surrounded
    by an extensive extracellular matrix. There are
    a number of different types of connective tissues
    that are classified by the organization and
    composition of the cellular components and the
    extracellular matrix. The following slides
    demonstrate and describe these connective tissues
    and their components.

2
Basic Connective Tissue Types
  • The basic connective tissue types include loose
    connective tissue, dense irregular connective
    tissue and dense regular connective tissue.
    These are classified based on the relative
    density and organization of the extracellular
    matrix components. There are a number of cell
    types that are resident to connective tissue.
    These are described in subsequent slides.

3
  • This shows a thin, plastic section of loose
    connective tissue from the oviduct stained with
    methylene blue- azure II. This type of
    connective tissue is very cellular and has few
    collagen fibers. The large elongated cell
    (arrow) is a fibroblast with an oval nucleus and
    much euchromatin.

4
  • This shows loose connective tissue from the
    mammary gland stained with hematoxylin and eosin.
    The loosely arranged collagen fibers (arrows)
    are acidophilic and lightly stained in this
    picture. A mast cell with a round nucleus is
    seen (MC) with a considerable amount of
    heterochromatin. Eosinophilic secretory granules
    fill the cytoplasm of this cell.

MC
5
  • This shows loose fibrous connective tissue
    similar to that seen in the previous slide.
    Another mast cell (MC) is located near the center
    of the field. Thin, light-staining collagen
    fibers (arrows) are seen in this picture.

MC
6
  • This shows a spread (not a tissue section) of a
    thin piece of mesentery illustrating a different
    view of loose connective tissue. The large,
    dark-staining cells are mast cells (MC) whose
    granules obscure the nuclei. The largest oval
    nuclei belong to mesothelial cells (Me), that
    form an epithelium on either side of the
    connective tissue. The smaller, oval nuclei
    belong to macrophages (Ma). These cells tend to
    have associated granular material in their
    cytoplasm. Other oval-shaped nuclei seen here
    are those of fibroblasts.

Ma
Me
MC
7
  • This shows a transmission electron micrograph of
    a mast cell illustrating numerous dense secretory
    granules in the cytoplasm. Note also the
    elongated nucleus (Nu) with abundant
    heterochromatin.

Nu
8
  • This shows another plastic section of loose
    connective tissue stained with methylene blue-
    azure II. A number of fibroblasts are seen (Fi)
    with oval euchromatic nuclei. A monocyte (Mo) is
    also seen with a darker, indented nucleus. A
    binucleate neutrophil (N) and a macrophage (Ma)
    with a small, light-staining nucleus are also
    seen.

Mo
N
Fi
9
  • This shows two plasma cells (PC) located in the
    loose connective tissue of the mammary gland.
    These cells have round, eccentric nuclei with
    slightly basophilic cytoplasm (indicating the
    presence of RNP). The large, pale nucleus is
    that of a fibroblast while the darker nuclei are
    those of fibrocytes.

PC
10
  • This shows adipose tissue stained with
    hematoxylin and eosin. The lipid in these fat
    cells is dissolved out during the fixation and
    embedding process. Only a thin rim of cytoplasm
    and the flattened nuclei (arrows) are seen.

11
  • This shows a developing adipose cell (arrow)
    stained with hematoxylin and eosin. Note the
    ring of cytoplasm and the rounded nucleus
    surrounding a lipid droplet. Acidophilic
    collagen fibers are seen around the cell.

12
  • This shows adipose cells preserved so that the
    lipid is retained in the cell and stained with
    osmic acid, hence the really dark appearance of
    the cells.

13
  • This shows loose connective tissue (CT) within a
    mucosal fold in the gall bladder. Numerous
    collagen fibers and abundant cells can be seen in
    the connective tissue. The cells cannot be
    readily identified at this magnification. (What
    type of epithelium is seen here?)

CT
14
  • This shows a section of the spermatic cord
    illustrating dense irregular connective tissue.
    In dense connective tissues, the abundant
    collagen fibers form interwoven bands of tissue.
    In contrast to loose connective tissue, there are
    relatively few cells (mainly fibrocytes). On the
    edges of the tissue is a simple squamous
    epithelium (Ep).

Ep
15
  • This shows dense irregular connective tissue at
    higher magnification than in the previous slide.
    The bundles of brownish collagen fibers can be
    seen coursing in different directions and
    different planes. A few thinner, darker staining
    elastic fibers can be seen in this section
    (arrows).

16
  • This shows dense elastic tissue of the aorta at
    low magnification. The thin elastic fibers
    (stained black) in the wall of the aorta (arrows)
    form layers separated by spaces. The collagen
    fibers are stained brown in this section.

17
  • This shows another example of dense irregular
    connective tissue from the urinary bladder at low
    magnification. This particular section has more
    cells than the previous example, but still fewer
    than the loose connective tissue seen earlier.
    Most of the nuclei belong to fibrocytes.

18
  • This shows another picture of dense irregular
    connective tissue from the urinary bladder. Note
    that the collagen bundles in the top of the field
    are more organized than those at the bottom.

19
  • This shows a section of the penis illustrating
    dense regular connective tissue stained with
    hematoxylin and eosin. Most of the collagen
    fibers (pink staining) are oriented parallel to
    each other. The nuclei of fibrocytes are present.

20
  • This shows dense regular connective tissue (CT)
    from a ganglion. On the left side of the field
    are elongated nuclei of nervous tissue (NT). The
    remainder of the field is occupied by dense
    collagenous fibers with few, flattened nuclei of
    fibrocytes.

NT
CT
21
  • This shows a transmission electron micrograph of
    a macrophage. The nucleus (Nu) is eccentrically
    located and is relatively heterochromatic. Note
    the lysosomes/residual bodies (R) in the
    cytoplasm as well as mitochondria, rough
    endoplasmic reticulum. Also, note the collagen
    fibrils outside the cell (C).

Nu
R
C
22
  • This shows a transmission electron micrograph of
    a lymphocyte. Notice that the nucleus (Nu)
    occupies a large portion of the cell, is indented
    and has a fair amount of heterochromatin. The
    cytoplasm has only a few organelles and the
    plasma membrane tends to be irregular due to
    movement of the cell.

Nu
23
CARTILAGE
  • Cartilage is a specialized form of connective
    tissue composed of cells called chondrocytes and
    their surrounding matrix. There are three types
    of cartilage that are distinguished based on
    their matrix characteristics.

24
  • This shows a light micrograph of hyaline
    cartilage located in the trachea. The pieces of
    cartilage (HC) are bordered by dense regular
    connective tissue of the perichondrium (P). The
    cartilage cells or chondrocytes (arrows) are
    located in lacunae (these are difficult to
    discern at this magnification).

P
HC
25
  • This shows a portion of the previous picture at
    higher magnification illustrating the
    chondrocytes in lacunae (arrows). The matrix
    surrounding the cells is composed of collagen
    fibers (too small too be seen here) and other
    components including glycosaminoglycans such as
    chondroitin sulfate.

26
  • This shows hyaline cartilage (HC) from the nasal
    cavity illustrating chondrocytes in their lacunae
    and the glassy appearance of the surrounding
    matrix (purple staining here). Note the
    organization of the dense regular connective
    tissue of the perichondrium (P) as compared to
    the irregular dense connective tissue of the
    surrounding connective tissue ().

HC
P

27
  • This shows a higher magnification of hyaline
    cartilage from the trachea. The chondrocytes on
    the right side of the field are not as mature and
    fill their lacunae (arrow) while those of the
    left have more space surrounding the cell.

28
  • This shows a section of elastic cartilage stained
    with a Verhoeff stain. Identify the
    perichondrium (P) surrounding the cartilage.
    Note the specifically stained elastic fibers
    (arrows) characteristic of this cartilage type.
    Also notice that the chondrocytes and their
    lacunae get larger as they progress from the edge
    of the cartilage towards its center.

P
29
  • This shows a higher magnification view of elastic
    cartilage. The elastic fibers are more clearly
    seen in this picture as are the chondrocytes and
    their lacunae.

30
  • This shows elastic cartilage of the epiglottis
    stained with a Trichrome stain. Note that the
    collagen of the perichondrium (P) is stained
    green however, the collagen type II within the
    cartilage does not stain. The elastic fibers are
    stained purple (arrows)

P
31
  • This shows a light-stained section of
    fibrocartilage. The cartilage stains acidophilic
    due to the collagen fibers. Note that the
    chondrocytes and lacunae are small and often have
    some regular pattern to their organization (in
    rows). There is no perichondrium associated with
    this cartilage type.

32
  • This shows a higher magnification view of
    fibrocartilage illustrating the collagen fibers
    within the matrix surrounding the chondrocytes.
    This type of cartilage is often found between
    hyaline cartilage and dense connective tissue.

33
BONE
  • Bone is a specialized connective tissue with a
    mineralized extracellular matrix. Bone generally
    consists of three cell types including the
    osteoprogenitor cells, osteoblasts (osteocytes
    when differeniated) and osteoclasts. The
    following slides illustrate some of the features
    of bony tissue.

34
  • This shows a low magnification view of the end of
    a long bone. Above the epiphyseal plate (EP) is
    spongy bone. The outer portion of the shaft is
    compact bone (CB), which is laid down by
    appositional growth from the periosteum. The
    compact bone surrounds the spongy bone and bone
    marrow of the shaft.

EP
CB
35
  • This shows a cross-section of developing bone
    from a fetal finger. The outermost layer is the
    connective tissue of the periosteum (P). Small
    pieces of calcified cartilage are seen (blue
    staining) as are hypertrophying cartilage
    (arrows).

Tendon
P
Spongy Bone
Developing Compact Bone
36
  • This shows a higher magnification of the previous
    slide illustrating developing bone.

Spongy Bone
Calcified Cartilage
37
  • This shows red blood cells (RBC) in the bone
    marrow bordering pieces of calcified cartilage
    (arrows). The calcified cartilage (blue) is
    covered with osseous tissue (deep pink staining).

RBC
38
  • This shows a scanning electron micrograph of bone
    surface. Note the Haversian Canals (HC), the
    concentric lamellae surrounding these and the
    lacunae of the osteocytes (arrows).

HC
39
  • This shows a section of decalcified bone. The
    structural features are similar to that in the
    previous slide illustrating the Haversian system.

Haversian Canal
Osteocytes
40
  • This shows a transmission electron micrograph of
    an osteocyte surrounded by its lacuna. The
    processes extending from the cell body are
    located in canaliculi (arrows). The matrix of
    the bone surrounds the canaliculi.

41
  • This shows a section of decalcified bone and
    associated skeletal muscle (SM). The skeletal
    muscle is attached to the connective tissue of
    the periosteum (P). The large space is due to
    shrinkage of the periosteum during processing of
    the tissue. Small Haversian Canals can be seen
    within the bone (arrows).

P SM
42
  • This shows a section of decalcified bone
    illustrating the connective tissue of the
    perioosteum (P). Osteoblasts are located along
    the inner edge of the periosteum (arrow). These
    cells will deposit and become entrapped in bony
    matrix (appositional growth).

P
Compact Bone
43
  • This shows another section of decalcified bone
    and associated skeletal muscle (SM). Note that
    the osteogenic layer of the periosteum is quite
    cellular (arrows) with basophilic osteoblasts
    located at the periphery of the bone.

SM
44
  • This shows bony tissue (upper right corner) and
    the dense irregular connective tissue of the
    periosteum (P). Note that the indentation of the
    periosteum into the bone contains looser
    connective tissue. Lining the periosteum are
    basophilic-stained osteoblasts (Ob)

Ob
P
45
  • This figure shows decalcified bone (B) and dense
    connective tissue of an associated tendon (T)
    attaching to the periosteum.

B
T
46
  • This shows decalcified bone illustrating a
    resorption canal surrounded by the bony tissue.
    Osteoclasts (arrows) can be seen lying next to
    the bony tissue.

47
  • This illustrates bone marrow (BM) adjacent to
    inner circumferential lamellae of bone. The dark
    irregular areas (arrows) are the original
    calcified cartilage indicating that this was
    formed by endochondral ossification.

BM
48
  • This illustrates bone marrow (BM) and the
    osteoblasts (Ob) lining bone. The osteoblasts
    extend into the beginning of a Volkmanns Canal
    (VC), which carries blood vessels into the
    Haversian system.

BM
Ob
VC
49
  • This schematic illustrates the process of
    intramembranous ossification. Mesenchymal cells
    form an elaborate network (1). These cells then
    enlarge and differentiate into osteoblasts (2).
    The cells lay down an intercellular matrix an
    form bony spicules (3) covered by osteoblasts.

1 2 3
50
  • This is a decalcified section of the root of a
    tooth and its associated alveolar bone (B). The
    root of the tooth is covered by cementum (C) and
    collagen fibers which anchor the tooth into the
    bony tissue.

B
C
51
  • This shows a high voltage electron micrograph of
    a relatively thick plastic section illustrating a
    fibroblast (Fi) with bundles of collagen fibers
    attaching to the cell surface (arrows).

Fi
52
  • This shows another high voltage electron
    micrograph of collagen fibrils (arrows) attaching
    to a myocyte (M). The very thin filaments are
    glycoproteins in the extracellular matrix while
    the dense globular material is proteoglycan (blue
    arrows).

M
53
  • This shows collagen fibers attached to two
    skeletal muscle cells (SM) and a capillary (C).

SM
SM
C
54
  • This shows a scanning electron micrograph of a
    fibroblast (Fi) within a network of collagen
    fibers.

Fi
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