Connective Tissue Part II PDF

Connective Tissue Part II Prepared by: Dr. Amal Abd EL-Hafez Assist. Prof. of Histopathology  Learning Objective At the end of this lecture, you will be able to: List the fiber types of CT know the character of each type of CT fibers. Identify the ground substanc...

Connective Tissue Part II Prepared by: Dr. Amal Abd EL-Hafez Assist. Prof. of Histopathology  Learning Objective At the end of this lecture, you will be able to: List the fiber types of CT know the character of each type of CT fibers. Identify the ground substance of CT Compare between the types of connective tissue. Recognize the distribution of connective tissue types in the human body.  C.T. Fibers The connective tissue fibers are formed by proteins that polymerize into elongated threaded structures. They are 3 types:- 1. White collagenous fibers 2. Reticular fibers 3.Yellow elastic fibers Collagen and reticular fibers are formed of the protein collagen. Elastic fibers are composed mainly of the protein elastin.  Collagen Collagen is the most abundant protein in the human body, representing 30% of its dry weight. The collagens are a family of more than 25 members. Example of collagens: collagen type I, II, III, IV…… Collagen synthesis: collagen It is a protein formed mainly by fibroblasts, chondroblasts, osteoblasts, and odontoblasts. Collagen is synthesized first as collagen precursor called tropo-collagen which become maturated into collagen. Tropo-collagen is made of principal amino acids, glycine, proline, hydroxyproline and hydroxylysine. Vitamin C is vital for synthesis of normal collagen.  collagen Characters of collagen fibers 1.Strong 2. Resistant 3. Flexible but not elastic 4. white in fresh state 5.Present in several types e.g. collagen fiber type I, II, III …etc Sites: Ligaments & tendons Function: 6.Provide strength 7. resist stretch  Elastic Fibers Synthesis: by fibroblast and other cells e.g smooth muscle and chondroblast. It’s formed of a core of elastin and surrounding fibrillin proteins. Character: 1.Stretch & recoil 2.Flexible & elastic 3.Yellow in fresh state Function: Provide elasticity Sites: 1. Some ligaments. 2.Wall of large arteries (Aorta and its branches)  Reticular Fibers Structure : collagen type III Synthesis: reticular cells Character 1.Branch & anastomose to form network. 2.Stained black with silver Function: Supportive network forming background of organs (stroma) Definition: the extracelluar substance (material) in which the CT cells & fibers are embedded. The ground substance including the fibers forms the extracellular matrix (ECM) component of the CT. Structure: 1.Colorless, transparent, formed by fibroblast. 2.Mixture of glycosaminoglycans (GAGs), proteoglygans, glycoproteins, and tissue fluid. Function: 3.Medium for transport 4.Physical barrier against spread infection Classification of CT according to the consistency of matrix & cell type: If the matrix is soft, gel like → general CT ( CT proper) If not soft → specialized CT:- It may be rubbery → cartilage It may be solid or hard → bone It may be fluid → blood  Connective tissue proper Loose: Dense: (Cells more than fibers) (Fibers more than cells) 1.Areolar CT 1.Regular fibrous CT 2.Adipose CT 2.Irregular fibrous CT 3.Reticular CT 3.Yellow elastic CT 4.Mucoid CT  1. Loose Areolar C.T. Site: the most common, distributed under epithelia of body; surrounds capillaries…….etc Structure: Gel like abundant matrix. All fiber types are present. All CT cells: fibroblasts, macrophages, mast cells, and white blood cells. Function: support epithelial cells  2. Loose Adipose CT: Structure: Cells: mainly fat cells however, few other CT cells may be present. Fibers: all fiber types are present There are 2 types: 1.White adipose CT 2.Brown adipose CT  White [yellow; uni-locular] Adipose Tissue Structure: Lobules of uni-locular adipocytes separated by CT fibers. Sites: throughout the body Subcutaneous tissue. Around internal organs. Function: Storage and mobilization of fat.  Brown [multi-locular] Adipose Tissue Called brown fat because of its color, due to large number of blood capillaries & mitochondria. Structure: Lobules of multi-locular adipocytes separated by CT fibers + numerous blood capillaries + nerve fibers between fat cells. Function: Energy and heat production. Sites: Limited distribution. In new born: neck, axilla, around kidney, to be replaced by white fat in adult  3. Reticular C.T. Structure: Reticular fibers + reticular cells forming network together. Stain: Black with silver. Sites: Stroma of bone marrow and different organs. Function: supporting framework for bone marrow and organs.  4. Mucoid [Mucous] C.T. Structure: Matrix: Abundant jelly like ground substance Cells: fibroblasts. Fibers: fine collagen fibers & reticular fibers Sites: 1. The umbilical cord (Wharton's jelly). 2. Pulp of teeth. Mucoid [Mucous] C.T.  5.Regular Collagenous Dense C.T. Structure: Fibers: Parallel, closely packed bundles of collagen fibers. Cells: Fibroblasts are arranged in rows parallel to the fibers Matrix: scanty Function: Offer great resistance to traction forces. Sites: 1.Tendons of skeletal muscles, 2.Ligaments.  6. Irregular Dense Collagenous C.T: Structure: similar to the regular dense CT but the collagen bundles are irregularly arranged. Sites: Dermis of the skin, Capsules surrounding organs.  7. Elastic [yellow] C.T. Structure: Fibers: regular parallel elastic fibers (mainly, giving it a yellow color) + few thin collagen fibers. Cells: few fibroblasts. Matrix: scanty Function: Provide high elasticity. Sites: 1. Walls of large arteries. 2.Ligamentum nuchae.  RECOMMENDED REFERENCES, WEBSITES Junqueira's Basic Histology: Text and Atlas, Thirteenth Edition 2013 ISBN-13: 978-0071780339 ISBN-10: 0071780335 Edition: 13th The histology tutor: http://www2.yvcc.edu/histology zoomer/HistologyTutorials/hi stology_tutorials.htm