Histology Lecture 9: Connective Tissue (1) PDF

Histology lecture (9) Connective tissue (1) Histology  Supports, binds and separates various tissues and organs. A. Connective tissue proper. B. Special types of CT: Carti...

Histology lecture (9) Connective tissue (1) Histology  Supports, binds and separates various tissues and organs. A. Connective tissue proper. B. Special types of CT: Cartilage. Bone. Blood and hematopoietic tissue Lymphoid tissue. White collagenous fibres Macromolecules. Fibroblast. Yellow elastic fibres Multi-adhesive Macrophage. Reticular fibres glycoprotein. Mast cells. Plasma cells. Lymphocytes. Leukocytes. Adipose I A WHITE COLLAGENOUS FIBRES 1. Color: the bundles are white in color. 2. Strong and resist stretch. 3. It forms wavy bundles: the bundles branch but the single fiber does not branch. 4. Can be affected by; converted into gelatin by boiling. Destroyed by acids and alkalies. Digested by pepsin and collagenase enzyme (of bacterial origin). Histology The bundles can be stained: Acidophilic Blue Red 1- Each collagenous bundle is formed of group of fibers which are composed of fibrils. 2- Each fibril is formed of tropocollagen molecules:-  These molecules are synthesized by fibroblasts.  Length: 280 nm.  Each molecule is composed of three polypeptide chains twisted around each other to form a triple helix.  The arrangement of tropocollagen molecules gives the fibril a cross banding appearance. Histology  Bone.  The tropocollagen molecules  Tendon  Forms fibrils & fibers.  Teeth.  Dermis of skin  Hyaline & elastic cartilage.  Forms fibrils only.  Reticular stroma of liver, spleen,  Network of fibrils. kidney, endocrine glands &  Special stain: silver lymph nodes.  Basal lamina of basement  Network of tropocollagen membranes. molecules.  Basal lamina of the placenta.  Thin fibrils. Histology B YELLOW ELASTIC FIBRES 1- Color: yellow. 2- Thin, long and highly refractile. 3- Elastic in nature, recoil after release of stretch. 4- The fibers branch and may form elastic membranes, e.g. in the wall of the aorta. 5- Not affected by boiling. 6- Can be digested by pancreatic elastase enzyme. ’ ’ Acidophilic. Yellow. Black. Each fiber is formed of : 1. Elastin protein in the center. 2. Oxytalan fibers in the periphery called. Sites: 1. In the walls of arteries. 2. In the trachea, bronchi and bronchioles. 3. Ligamentum flavum between vertebrae. Elastic fibers produced by fibroblasts (in CT) and by smooth muscle cells (in arteries). Marfan syndrome: patients with deficiency in deposition of elastin develop aortic swellings called aneurysms, a life –threatening condition Histology C RETICULAR FIBRES Reticular → tend to form network Argyrophilic → due to affinity to Silver. They are very thin fibers that branch and anastomose to form a network. Not Black. Magenta colored (polysaccharides). stained. Type III collagen in the center (can be stained by silver). Coated by glycoprotein (can be stained by PAS). Stroma of parenchymatous organs e.g. Liver, spleen and lymph nodes. Reticular lamina of the basement membranes. Histology II 1. Fibrous component: collagenous, elastic and reticular fibers. 2. Tissue fluid: derived from capillaries. 3. Amorphous component : formed of two main parts: a. Glycosaminoglycans (gags): Soft jelly like hard Not linked to a core of protein (synthesized Linked to a core of protein forming by a class of integral membrane proteins proteoglycans. called hyaluronan synthases instead of rER and Golgi pathway). Sites Sites 1. Mucoid CT (Wharton's jelly of umbilical 1. Chondroitin sulphate in cartilage & cord, vitreous body of eye and Pulp of bone. growing teeth) 2. Heparan sulphate in basal lamina 2. Synovial fluid. Can be hydrolysed by hyaluronidase enzyme Not affected. (released by bacteria and sperms). b. Glycoproteins:  Chondronectin in cartilage.  Osteonectin in bone.  Fibronectin in C.T. proper.  Act as adhesive material.  magenta-colored (due to presence of glycoproteins).  e.g. Toluidine blue: reddish purple in color (due to presence of gags).  N.B. Metachromasia means that the tissue is stained giving a color different from the color of the dye. Histology III 1. Undifferentiated Mesenchymal Cells 1. Mast cells 2. Fibroblasts. 2. Free macrophages 3. Adipose cells. 3. Plasma cells 4. Reticular Cells. 4. Pigment cells. 5. Macrophages cells. 5. Blood leucocytes Histology The commonest cell that are responsible for synthesis of C.T. matrix and fibers. Pericytes (branched cells around blood capillaries) Mesodermal cells of embryo. which develop from U.M.C. Can divide Cannot divide. Undifferentiated. Fully differentiated 1. During fetal life: in embryonic CT (mesenchymal  The most common type of C.T. cells. and mucoid CT).  Very numerous in the loose C.T. 2. In post-natal life: in pulp of deciduous teeth. Its remains form pericytes around capillaries.  Tiny.  Branched with few cell processes that are long and  Branching spindle-shaped cells. thin.  Common in embryonic CT (mesenchymal and mucoid CT).  oval, vesicular (with fine chromatin and prominent  Central, large, oval, single and vesicular. nucleolus) and eccentric in position.  Pale basophilic (due to free ribosomes).  basophilic with negative Golgi image.  mainly free ribosomes  The cytoplasm is rich in ribosomes, rER and  little rER and small Golgi prominent Golgi & Some mitochondria  Microtubules and microfilaments to preserve the shape of the cell. Histology  It acts as a multipotent stem (mother) cell 1- Synthesis of the components of C.T. matrix. 2- Synthesis of nearly all types of C.T. fibers (fiber-forming cells). 3- Responsible for growth of C.T. and healing of wounds.  Spindle-shaped but more flat and has fewer processes.  Darker.  Less basophilic (less rer).  Preserve and renew the already formed components of CT matrix and fibers. Histology From migrating blood monocytes (that originally UMC. develop from UMCs in bone marrow). Cannot divide. Cannot divide. Fully differentiated. Fully differentiated.  Mainly in loose CT.  Reticular stroma of parenchymatous organs  Large. Small.  Branched cell with many processes. The reticular  Rounded with pseudopodia (processes). fibers are attached to their processes.  The 2nd most common cell in loose CT. The commonest cell in reticular CT.  Eccentric, small, kidney-shaped oval or irregular,  Central, oval and pale. single and pale. 1. Hx & E → Pale basophilic and not clear. 1. Hx & E → Pale basophilic. 2. Special stains → 2. Special stain → Silver stain. Vital stain e.g. trypan blue. Supravital stain e.g. neutral red.  Much lysosomes, few rER and free polysomes,  Few organelles including rER, ribosomes and small Golgi and few mitochondria. mitochondria.  Psudopodia, phagosomes and pinocytotic vesicles. Histology A) M1 "killer" macrophages:  It acts as a multipotent stem (mother) cell for: 1. Phagocytic function: can phagocytize foreign 1. Supportive function: with reticular fibers, they bodies e.g. bacteria. both form a delicate network which support 2. Many phages may fuse together and form parenchymal cells. multinucleated foreign body giant cells to attack a 2. Antigen Presenting Cells (APCs): present large foreign body. antigens to T-Helper lymphocytes to activate the 3. Antigen Presenting Cells (APCs): present antigens immune system. to T-Helper lymphocytes to activate the immune 3. Phagocytic function. system. 4. Secretory function: they secrete enzymes (e.g. collagenase and elastase) and cytokines. B) M2 "repair" macrophages: function in constructive processes like wound healing and tissue repair. They secrete growth factors and other cytokines. Histology UMCs → Lipoblast → Brown adipocyte → White adipocyte. Can’t divide. Fully differentiated. 1. Mainly in sites of white adipose In sites of Brown adipose CT CT. 2. Also in loose CT. 10-times smaller than white 10-times larger than brown adipocyte adipocyte oval The main cells in adipose CT A single central and rounded A single flat peripheral nucleus nucleus. pushed to one side giving a Signet Ring appearance. Contains many fat droplets: Contains a large fat globule: 1. Paraffin sections (Hx&E) → 1. Paraffin sections (Hx&E) → an Cytoplasm is acidophilic with many empty space due to dissolved fat vacuoles due to dissolved fat globule. droplets. 2. Frozen sections with special fat stains:  Sudan III → lipid is orange in color.  Sudan black or Osmic acid → lipid is black in color. 1. Multiple fat droplets. 1. A single large fat globule. 2. sER and numerous mitochondria 2. sER and some mitochondria are are scattered among the fat present in the remaining droplets. cytoplasm beside the nucleus.