Tuesday, July 31, 2012

The Connective Tissue


Objectives:
·        Identify the connective tissue.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
·        Differentiate between the different types of connective tissue.
·        Identify the contents and structures of the connective tissue.
·        Recognition of different types of the fibers.
·        Distinguish between different types of cartilage.

General location: under the epithelial tissue.

General function: supporting.

General components: each connective tissue contains three elements which are:
                                      CELLS,,,, FIBERS,,,, GROUND SUBSTANCES
Usually the cells are responsible for fibers and ground substances synthesis which are together called MATRIX.

Types of fibers: 1* COLLAGEN fibers also known as white fibers, they are found as thick bundles of fibers, characterized by being strong and tough.
                           2*ELASTIC fibers also known as yellow fibers, they are thin individual fibers but elastic and flexible, can also be seen as wrinkled fibers.
                           3*RETICULAR fibers which are thin highly branched, they make network like structure, act in filtration.
Ground substances: are complex combination between polysaccharide and protein such as hyaluronic acid, chondroiton sulfate, dermatan sulfate and keratin sulfate. In addition, minerals like calcium and phosphate could be found in the matrix of the connective tissue.

TYPES OF MATURE CONNECTIVE TISSUE
A- LOOSE CONNECTIVE TISSUE 

1*AREOLAR CONNECTIVE TISSUE
Description: this tissue contains low amount of fibers but with large amount of cells mainly fibroblasts which are spindle shaped cells with central dark nuclei and peripheral light cytoplasm in addition to the presence of different types of the white blood cells, large amount of blood vessels can be seen in the matrix of this tissue because of spaces found there.
Function : support
Location : hypodermal layer
Slide #1: a mammal spread film of fasciae stained with verhoeff and eosin stains. This tissue represents the areolar tissue. Note the loosely distributed collagenous and elastic fibers and the cells dispersed in between (you can see nuclei of the fibroblast cells).

2*ADIPOSE TISSUE
Description: the adipocytes are able to store large amount of fat in their cytoplasm, so the nucleus is taking the peripheral position. The majority of the cytoplasm is occupied by the fat vacuole in spite of appearing as empty one but that because of tissue processing using organic solvents. Blood vessels may be seen between adipocytes. 
Function: *support for vital organs (cushioning system).
                *fat storage used in need as energy source
                *heat isolation
Location: surround heart and kidneys
                Subcutaneous layer
Slide #2: a section in fatty tissue stained with hematoxylin & eosin. Notice the adipocytes, which look large round empty circles with the cytoplasm being the line surrounding the space, also notice the nuclei, which look round dark and pushed to the periphery.


3*RETICULAR CONNECTIVE TISSUE
Description: the reticulocytes are rounded cells with central dark nucleus and the cytoplasm is evenly distributed around the nucleus. The matrix is filled with thin highly branched fibers forming network structure.
Function: support and filtration
Location: liver and lymph node
Slide #3: a section from lymph node stained with silver. The slide represents the reticular tissue. Note the network of the black stained reticular fibers and the round darkly stained round nuclei of the reticulocytes in between the reticular fibers.


B*DENSE CONNECTIVE TISSUE
Description: contains large amount of fibers, specifically collagen, and fewer amounts of cells which are mainly fibroblasts. According to the arrangement of the fibers, the tissue is classified into two types

1*REGULAR DENSE CONNECTIVE TISSUE
Description: The collagen fibers are arranged in rows with light colors (pink, blue) look like thin lines while the fibrocytes are compressed between these fibers rows with central dark nuclei and lighter cytoplasm.
Function: supporting and connection between bones and muscles.
Location: ligaments and tendons.
Slide #4: a longitudinal section of mammal tendon stained with hematoxylin & eosin. Notice the parallel bundles of collagen fibers and the nuclei of the fibroblasts squeezed in between these fibers.


2*IRREGULAR DENSE CONNECTIVE TISSUE
Description: the large number of collagen fibers are randomly scattered in the matrix with different direction of orientation stained lightly. The fibrocytes which are low in number are distributed between the fibers with dark nuclei and light cytoplasm.
Function: support
Location: dermis of the skin.
Slide #5: A section from human skin, sectioned through epidermis, dermis, and hypodermis stained with hematoxylin & eosin. The same slide you saw in the first lab. Notice the dermis layer; it contain the collagen fibers as parallel bundles in some areas and as cross sectioned bundles in other areas with nuclei of the fibroblasts dispersed in between these fibers.
 

2*ELASTIC CONNECTIVE TISSUE
Description: it contains a lot of elastic fibers, which looks as wavy lines. Fibroblasts will be dispersed between the fibers.
Function: give elasticity to the organ
Location: wall of elastic artery (aorta), ligaments, and lung
Slide #6: a section of Mammal ligament stained with hematoxylin & eosin. Notice the wavy darker lines, which are usually grouped in different spots, you can see the nuclei of the fibroblasts in between.



C-CARTILAGE
Description: the chondrocytes are able to produce and precipitate large amount of chondroiton sulfate which gives the tissue jelly nature. The chondrocytes are localized in side special space which is called lacuna protecting it from the semisolid matrix. According to the additional contents of the matrix the cartilage tissue is classified into three types:

1*HYALINE CARTILAGE
Description: the chondrocytes which are rounded cells with central nuclei are located inside lacunae. Each lacuna may contain one, two or more chondrocytes. The matrix of this type contains very little amount of fibers, so it is clear and shiny like hyaline= glass. The tissue is surrounded by irregular dense connective tissue = the perichondrium to provide the tissue with nutrients because the cartilage tissue is avascularized tissue.
Function: support and maintenance
Location: upper respiratory pathways
Slide #7: a section of mammal trachea stained with hematoxylin & eosin. In the middle of the tracheal wall you can see the hyaline cartilage. Note the chondrocyte (large cells) in side the lacunae (spaces), notice also the dense irregular connective tissue surrounding the hyaline cartilage (perichondrium).

2*ELASTIC CARTILAGE
Description: the chondrocytes with their central dark nuclei are kept inside lacunae while the matrix is filled with light thin wrinkled fibers.
Function: support and elasticity
Location: ear pinna
Slide #8: a section from mammal external ear, stained with verhoeff and eosin in order to show the elastic fibers between lacunae. Notice the black lines (elastic fibers) surrounding the lacunae. You can see the chondrocyte inside the lacunae and the perichondrium surrounding the elastic cartilage tissue.



3*FIBROCARTILAGE
Description: the strongest and toughest type of cartilage because of the collagen fiber bundles filling the matrix compressing the lacunae containing the small chondrocytes with their own nuclei.
Function: support strongly
Location: intervertebral disks
Slide #9: a section in the mammal intervertebral disk stained with hematoxylin and eosin. Notice the thick bundles of collagen fibers in between the lacunae. Lacunae and chondrocytes here are smaller than those found in hyaline and elastic cartilages. Notice also that fibrocartilage doesn’t contain perichondrium.

D*BONE TISSUE
Description: the osteocyte is able to precipitate calcium and phosphorus in the matrix which becomes hard and solid one. According to the precipitation pattern the bone tissue is classified in to two types

1*THE SPONGY BONE
Description: the osteocytes precipitate minerals randomly as structure called trabiculae. Also the osteoclasts are found in this type for the metabolism of bone tissue.
Function: protection of red bone marrow.
Location: flat bones (skull)

2*THE COMPACT BONE
Description: this type of bone tissue is a repeated unit system; each unit is called osteon where the precipitation of minerals by osteocytes is regular as rounded layers called lamellae. The osteocytes are arranged at the lamellae kept inside lacunae one cell in lacuna. The different osteocytes are connected to each others by very fine canals radiating between them called canaliculi. The center of the osteon is occupied by a central canal which contains blood vessels. Adjacent osteons are connected by horizontal canal which is called Volkman's canal.
Function: support and muscle attachment.
Location: the diaphysis of the long bone.
Slide #10: Ground preparation of human bone, unstained thin cross section showing osteon structure. Notice the haversian (central) canals, Volkman's canal, lacunae, and canaliculi.
          

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