Histology Lecture 7 - Connective Tissue PDF

Connective tissue (Histology lecture) by Dr./ Dalia Noya Assistant professor of Histology Faculty of medicine Menoufia University ILOS Identify the components of connective tissue. Describe the histology of fibers and extracellular matrix. Classify the C.T....

Connective tissue (Histology lecture) by Dr./ Dalia Noya Assistant professor of Histology Faculty of medicine Menoufia University ILOS Identify the components of connective tissue. Describe the histology of fibers and extracellular matrix. Classify the C.T. cells and describe the histological features of each one. Correlate each C.T. cells to it’s function. Classify the types of connective tissue. Describe the histological characters of each type of connective tissue. Functions of connective tissue: 1- The main function is structural forming capsule & the internal architecture that support the cells of the organs. 2- It forms tendons, ligaments and the areolar tissue which fills spaces between the organs 3- Supports the soft tissues of the body e.g heart, lung &brain. 4- Share in the body defense and stores fat. 5- Share in the body defense as it contains phagocytes and immuno- competent cells  CONNECTIVE TISSUE  Connective tissue is the tissue which binds & connect organs together & tissues in the same organ together.  It is highly vascular and highly innervated.  Types of connective tissue include bone, cartilage, fat & lymphatic tissue  Connective tissue is composed of: 1- ground substance (matrix) 2- Fibers 3- cells 1- Ground substance Ground substance is a colorless and transparent substance presents between cells and fibers which binds them together. It is mixture of polysaccharides, glycoproteins and proteoglycans. These polysaccharides are secreted by fibroblasts. Ground substance also contains water and mineral salts. Function: interaction of neighboring cells, adhesion of cells and fibers.  2- Fibers of connective tissue Collagen Reticular Elastic fibers fibers fibers Structur Wavy fibers of variable Thin fibers branch to form Thin wavy branching e width a meshwork (reticulum) fibers Consist Collagen molecules Fibrils of type III Elastin protein s of polymerized into collagen collagen fibrils Functio Flexible fibers with high Provides a supporting Elasticity: Fibers can n tensile strength framework for cells. stretch to 150 % of length and return to the original state Light Seen as wavy fibers of Thin fibers, not Thin wavy fibers: Microscopy variable width (often visible in routine Weakly stained by H&E Special stains VIP thick): stains (H&E) H&E: stains collagen Special stains: Orcein: stains elastic fibers pink Silver: stains reticular fibers brown Masson trichrome: fibers black/brown Van Gieson: stains stains collagen fibers PAS: stains reticular elastic fibers yellow green fibers pink Mallory: stains collagen fibers blue Location Most abundant fiber Reticular connective In the wall of large blood type of connective tissue, stroma of liver, vessels, as aorta, also tissue kidney &lymph node present in ligamentum nuchae. 3-Cells of connective tissue 1- Fixed cells ( They are long- lived and stable) as: 1-Fibroblast , fibrocytes. 2- Undifferentiated mesenchymal cells. 3- Fat cells (adipocytes ) 4-Pericytes 5-Endothelial cells 6-Reticular cells 7-Histocytes (fixed macrophages) 2- Free cells (They are short- lived, motile and enter the C.T. from the blood)as: 1-free macrophage 2-plasma cell 3-mast cell 4-pigment cell 5-leucocytes of blood Fixed connective tissue cells: 1- Fibroblasts: Fibroblasts synthesize and secrete collagen and elastin, as well as the ground substance. Irregular shape, many short and sharp cytoplasmic processes  Pale, oval nucleus, & prominent nucleolus Basophilic cytoplasm rich in rER and Golgi apparatus and many ribosomes. Fibrocytes: spindle shaped cells, smaller than fibroblasts, cytoplasm poor in organelles. 2 - Undifferentiated Mesenchymal Cells (UMCS): They are similar to fibroblasts, but smaller and are found in the embryonic CT. They act as stem cells can differentiate to give the other types of CT cells. 3- Reticular cells: Star shaped cells with long processes by which they are interconnected, synthesize collagen type III which forms reticular fibers. Together with reticular fibers , they form the background of organs. 4- Adipocytes (fat cells): They are two types 1- Unilocular 2- Multilocular  Unilocular adipocyte Multilocular adipocyte shape Spherical cells, 50 – 150 μm in size Polygonal cells, smaller than unilocular. nucleus eccentric, flattened nuclei Spherical nucleus is usually in the center of the cell. cytoplasm thin rim of cytoplasm surrounding a single large many fat vacuoles of different sizes. fat vacuole which left empty after dissolution of A lot of mitochondria contain cytochrome lipid in hematoxylin and eosin section giving oxidases (brown color). signet ring appearance. Golgi apparatus, RER and SER are present. Function storage of fat, thermal isolation, body shape, heat production and warming the blood organ support, cushions. Site White adipose tissue Brown adipose tissue 5- Macrophages Macrophages are characterized by their phagocytic ability. They are present in the connective tissue of most organs and are often referred to as “Histiocytes”. They have a characteristic irregular surface, & an eccentrically located, oval or kidney- shaped nucleus. In the E/M, macrophages are have a well developed Golgi apparatus and many lysosomes. Macrophages are derived from bone marrow precursor cells (monocytes).  Free connective tissue cells: 1- Plasma cell  Plasma cells are derived from B- lymphocyte. They are antibody- producing cells.  These large, ovoid cells have basophilic cytoplasm due to their richness in rER.  The nucleus of the plasma cell is generally spherical but eccentrically placed.  The Golgi apparatus and centrioles occupy a region that may appear pale in routine histological preparations giving the characteristic negative Golgi image  The nucleus of a plasma cell has the appearance of a cartwheel (compact, peripheral regions of heterochromatin alternating with lighter areas of euchromatin).  Function: Synthesis of immuno-globulins (antibodies). 2- Mast cell :  Mast cells are oval cells. -The cytoplasm is filled with basophilic secretory granules. -The nucleus is spherical centrally situated and often obscured by abundant secretory granules. -Mast cells function: 1- Secretion of heparin which is an anticoagulant 2- Secretion of histamine which initiates allergic reactions 3- Pigment cells (melanocytes): They have oval cell body with long cytoplasmic processes. Their cytoplasm contain granules with melanin pigment. Function: Protection against UV rays 4- Free Macrophages: They are wandering cells, derived from blood monocytes, which enter the connective tissue upon need. They are phagocytic cells that participate in the immunological responses. 5- leucocytes (white blood cells)  Types of connective tissue 1- Connective tissue proper: a. loose connective tissue. b. Dense connective tissue ( regular – irregular). 2- Connective tissue with special properties: a- Elastic b- Reticular c- Adipose d- embryonic (mesenchymal, mucous) 3- Specialized connective tissue: a. Cartilage. b. Bone tissue. c. Blood. d. Lymphatic tissue.  Types of connective tissues proper 1.Loose areolar connective tissue 2.Mucoid connective tissue 3.Dense connective tissue 4.Reticular connective tissue 5.Elastic connective tissue 6.Adipose connective tissue 1.Loose areolar connective tissue:  It contains almost all types of cells and fibers.  It is called also areolar connective tissue as it contains potential areolae.  It is soft, flexible and distributed widely in the body.  It supports other body tissues. 2. Mucoid connective tissue:  Mucoid tissue has an abundance of ground substance composed chiefly of hyaluronic acid.  It is a jelly- like tissue containing very few collagen fibers.  The cells in this tissue are mainly fibroblasts.  Mucous tissue is the principal component of the umbilical cord. It is referred to as Wharton’s jelly. 3. Dense connective tissue: It consists of the same component of loose connective tissue but there are fewer cells and a clear predominance of collagen fibers. Its less flexible and more resistance to stress than its loose connective tissue. It has two types:  Dense regular connective tissue  Collagen fibers are arranged according to a definite pattern.  They consequently offer great resistance to traction forces.  Tendons are the most common example of this tissue.  Dense irregular connective tissue  Collagen fibers are arranged in bundles without a definite orientation.  Provide resistance to stress in all directions.  This tissue presents in capsules of the organs, reticular layer of the dermis, sclera and fibrous capsule of the joint. Dense regular CT Dense irregular CT 4. Reticular connective tissue: It is a special type of loose connective tissue that provides the architectural framework of organs. It is formed of reticular cells and branched reticular fibers. 5. Elastic connective tissue:  Elastic connective tissue is composed of bundles of thick, parallel elastic fibers. The spaces between these fibers are occupied by thin collagen fibers and flattened fibroblasts.  The yellow color and great elasticity are due to abundance of elastic fibers. Elastic tissue is present in yellow ligaments of vertebral column. 1. Adipose connective tissue:  Adipose connective tissue is a special type of connective tissue in which adipose (fat) cells predominate.  There are two types of adipose tissue: 1-White adipose tissue:  This type is composed of unilocular fat cells.  It represents 15- 20% of body weight in normal weight men and 20- 25% of body weight in normal weight women. Functions: 1. site of storage of energy & thermal insulation of the body 2. subcutaneous layers help to shape the surface of the body. 3. pads of adipose tissue act as shock absorbers chiefly in palms and soles. 4. filling spaces and keep some organs in position 2- Brown adipose tissue:  This type is composed of multilocular fat cells. It is also called brown fat due to the large number of blood capillaries in their tissues and numerous mitochondria.  It constitutes 5% of adipose tissue of human newborn.  It is important mainly in the first few months of neonatal life.  In exposure to cold brown fat produces heat that warms the blood passes through it  No One of adipose tissue is transformed into another. Thank you