Answer
A Complete Classification of Connective Tissues
There are many systems of classification of connective tissues. The main criteria used for categorization are fibers( amount and type), and ground substance ( composition and physical consistency). Time of appearance, cell types, tissue vascularity, and functions are minor characteristics applied to refine classifications. The following is a commonly used categorization:
1. Embryonic Connective Tissues
1A. Mucous connective tissue: the mucoid contents of umbilical cords
1B. Mesenchyme : the embryonic connective tissue in the fetus. All mature connective tissues
derive from mesenchyme. Mesenchyme tissue is replaced by mature connective tissue as the
organism passes through infancy, childhood, adolescence and into adulthood. However,
traces may still be found in some young adults.
2. Mature Connective Tissues
2A. Loose connective tissues
2Ai. Areolar tissue
2Aii. Adipose tissue
2Aiii. Reticular tissue
2.B. Dense connective tissues
2Bi. Dense regular connective tissue
2Bii Dense irregular connective tissue
2Biii. Elastic connective tissue
2C. Cartilage
2Ci. Hyaline cartilage
2Cii. Fibrocartilage
2Ciii. Elastic cartilage
2D. Rigid Connective tissue: Bone
2Di. Compact bone
2Dii. Cancellous/Spongy bone
2E. Liquid Connective Tissues
2Ei. Blood
2Eii. Lymph
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Work Step by Step
Connective Tissues
Composition: Connective tissues comprise the following components :cells, fibers, ground
substance and blood supply --in some cases.
Cells: Some cells of found in various types of connective tissue are fibroblasts, chondroblasts,
chondrocytes, osteoblasts, osteocytes, reticular cells, fat cells, mast cells, plasma cells,
formed elements of and lymphocytes.
Matrix. The matrix of a connective tissue is the non-living substances secreted by fibroblasts
the two constituents of matrix are fibers and the ground substance..
Fibers: The fibers of connective tissues are collagen fibers, reticular fibers and elastic fibers
different types and combination of fibers are found in different types of connective
tissues.
Ground substance: The character of ground substance varies from the solid calcified
substance of bone through the firm gel of cartilage , the viscous gel of areolar cartilage
to the frank fluid consistency of blood plasma and lymph . mainly, ground substance is a
solution of ions,salts, proteins, mucopolysaccharides ( glycosaminoglycans)
proteoglycans of varying viscosity.
A. Loose connective Tissue; The subtypes in this group are areolar, adipose(fat) and reticular
connective tissue.. In this type cells are few( except for the adipose type) . Loose
connective tissue underlies epithelium in many body locations. It anchors and supports
the epithelium ; it also supplies it with nutrients and oxygen and removes carbon-dioxide
and various kinds of dissolved waste solutes. Areolar tissue is able to perform all of these
functions because of its rich vascular supply and the open loose texture of its ground
substance
Dense Connective Tissues:
The sub-types in this group are dense regular connective tissue, dense irregular
connective tissue and Dense elastic connective tissue.
The cells are mainly fibroblasts but the relatively few fibroblasts and the scant ground
substance are of less importance than the type,amount and orientation of the fibers.
Fiber type is the most important characteristic in this grouping. The fibers are Type I collagen,
Type II collagen and elastic fibers. Large Type I collagen fibers are arranged in wavy parallel
bundles in dense regular tissue. In dense irregular Tissue collagen fibers display a 3-D
arrangement in the ground substance. Fibers of elastic connective tissue are made of
elastin and fibrillin.
Type I collagen have great tensile strength. Type II network resists stress from several
directions and elastic fibers enable tissue to extend ( up to 150%) and recoil to original
dimensions.
Cartilage:
The subtypes of the class are hyaline cartilage, fibrocartilage and elastic cartilage
Cells : The cells are chondroblasts (modified fibroblasts) and chondrocytes( mature chondroblasts).
Matrix. The ground substance is usually a firm but flexible gel in which is embedded a network of
collagen and elastic fibers.. The collagen fibers confer toughness on cartilage and the
elastic fibers confer flexibility. However, collagen ground substance may have over 70%
water. The dissolved solutes are usually proteins and the glycosaminoglycans(GAGs)
chondroitin sulfate, hyaluronic acid(HLA), keratan sulfate, and dermatan sulfate.
Hyaline cartilage has a perichondrium with fibroblasts and chondroblasts. . Chondrocytes exist in
spaces of matrix called lacunae. This cartilage is found at the ends of ribs and in the
epiphyseal plates of long bones
Fibrocartilage. there is no perichondrial layer of connective tissue around this type of cartilage
Cells; Chondrocytes in lacunae
fibers: Thick collagen fibers
ground substance(GS) : Scant; semi-firm in consistency
This is the strongest type of cartilage. it may be found in menisci(pads) of knees, and in
intervertebral discs. This tissue resits compressive shocks.
Elastic cartilage; Perichondrial layer layer present
Cells; Chondrocytes in lacunae
Fibers: Elastic fibers plus some Type II collagen fibers
This tissue confers strength and elasticity but maintains shape
Locations ; pinnae, epiglottis,
Rigid Connective Tissue : Bone
Compact bone
Cells ; osteoblasts and osteocytes, osteoclasts
osteoblasts produce the proteinaceous ground substance as well as the collagen fibers.
The matrix is then hardened to a rigid consistency by the infiltration of salts of inorganic
elements, principally, calcium and phosphorus.
Organization. The matrix of compact bone is organized into cylindrical structures around a central of Haversian canal. The cylinders are called osteons. The central canal contains blood vessels
and nerves. Chondrocytes live in spaces in the matrix called lacunae. Canaliculi , small passages, connect the lacunae with the central canal. This enables the osteocytes to access the blood supply of the central canal This permits them to get nourishment and get rid of wastes. Long bones which are partly compact bone in structure, have a marrow cavity in which is fatty (yellow) bone marrow with adipocytes and triglyceride stores.
Cancellous or Spongy bone.
Cells: osteoblasts and osteocytes
No osteons exist in this type of bone
Matrix: collagen fibers and calcified ground substance
Structure: Three dimensional network of spikes and trabeculae(processes)
Red bone marrow and blood vessels exist inspaces between the trabeculae
Spongy bone exist in cranial bones, ribs and at the ends of long bones.
Spongy bone houses hematopoietic tissue and protects internal organs from
physical shock.
Liquid Connective Tissue:
Blood
Cells : Leukocytes, erythrocytes and thrombocytes ( platelets). Platelets are not living cells. They
are fragments of bone marrow cells known as megakaryocytes
Matrix: Blood plasma-- an aqueous solution of gases, ions , salts, and proteins; The major
protein solutes are hormones, enzymes, albumin, globulins, and
fibrinogen ( precursor of fibrin fibers)
Blood is in heart and blood vessels . It distributes nutrients and oxygen. It also removes wastes of all
types.
White blood cells protect against microbes, antigens, allergens. Platelets are essential
factors that induce clotting to protect against excessive bleeding.
The high water content of blood enables it to function in the distribution of body heat, and
the maintenance of temperature homeostasis.
Lymph
Cells : mainly lymphocytes;:These cells are important in immunological antigen-antibody
reactions.
Lymph matrix: This is a pale proteinaceous fluid found in lymph vessels and lymphoid organs.
It links the interstitial fluid with blood plasma. One of its functions is to return
water and proteins to the cardiovascular system. Lymph flows in a one -
-way route to the blood vessels and the heart.