connective tissue

لاعتم قلاخ مان هب Dr. Zahiri

What's the main role of connective tissue?

o Mechanical support o Material that connects and binds cells into tissues o Binds tissues to each other o Protection and Defense o Serving as a medium for exchange o Storage (water, ions, minerals, Growth factor) o Energy supply

What's the contents of connective tissue?

cells connective tissue ECM

 Fibers  Ground substance  Fluid

The cells

Mesenchyme Cells of connective tissue Adult Fixed Cells

Fibroblast Macrophage Adipose cells Mast cells Undifferentiated mesenchyme cell

Wandering Cells

Lymphocytes Plasma cells Blood cells

Mesenchymal cells

 Small fusiform or stellate cells  Not easily distinguished from fibroblasts  Have delicate chromatin pattern  Pluripotential

Fibroblast

 are most common cells of C.T.

 Produce and secrete ECM  Active fibroblast has more cytoplasm include of developed RER, Golgi apparatus and euchromatic nucleus = activated (wound healing)  Inactive fibroblast (Fibrocyte) has flattened nuclei, sparse cytoplasm  Fibroblasts may differentiate to adipose cells or chondrocytes

wound healing



Myofibroblast :

• are modified fibroblasts • They have bundle of actin similar to smooth muscle cells • Abundant in wound healing ( wound contraction) 

Activated Fibrocyte

= fibroblast

Macrophage (MPS)

 Origin: BM monocyte ( in blood) Macrophage in C.T.

 Irregular membrane surface; nucleus may be oval and is eccentric  Size: 10-30 micro  Phagocytosis of cell debris and micro organisms  Presenting antigens to lymphocytes  RBC turnover in spleen  Secretion of cytokins, enzyme  In chronic inflammation form Epitheloid cells or multinuclear giant cells

   

Mast cell

Cytoplasm full of granules containing heparin, histamine, proteases, chemotactic factors, chondroitin sulphate Size: 10-13 micro Centeric nucleus Originate from bone marrow stem cell

- Immediate hypersensitivity reaction - Slow reaction

Plasma cell

 Common in intestinal lamina propria and glands secreting immunoglubulins such as lacrimal glands, salivary glands, and mammary gland  Oval cell with basophilic cytoplasm, clock face nucleus  Differentiate from B - lymphocytes  Life span 10-20 days

Adipocyte

Others

 Neutrophils  Eosinophils  Basophils  Lymphocytes - small, heterochromatic nucleus

Fibers

 Collagen fibers  Elastic fibers  Reticular fibers

Collagen fibers

 Staining ( Eosin - pink; Mallory’s - blue; Masson’s – green)  Physical feature

Chemical components

 prolin  lysin  Hdroxy prolin  Hydroxy lysin

Biosynthesis

Disorders

:

 Osteogenesis imperfecta (gene or amino acid)  Progressive systemic Sclerosis (fibrose- keloid)  Vitamin C is a co-factor for prolin hydroxylase

Reticular Fibers (Collagen type III)

 Staining (Argylophilic- PAS)  Physical feature  Formative cell  Disorders ( ehlers-Danlos IV)

(a) Connective tissue proper: loose connective tissue, areolar Description: Gel-like matrix with all three fiber types; cells: fibroblasts, macrophages, mast cells, and some white blood cells.

Function: tissue fluid.

Wraps and cushions organs; its macrophages phagocytize bacteria; plays important role in inflammation; holds and conveys Location: capillaries.

Widely distributed under epithelia of body, e.g., forms lamina propria of mucous membranes; surrounds Epithelium Lamina propria Photomicrograph: Areolar connective tissue, a soft packaging tissue of the body (300x).

Elastic fibers Collagen fibers Fibroblast nuclei

(b) Connective tissue proper: loose connective tissue, adipose Description: fat droplet.

Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, have nucleus pushed to the side by large Function: Provides reserve food fuel; insulates against heat loss; supports and protects organs.

Location: Under skin in the hypodermis; around kidneys and eyeballs; within abdomen; in breasts.

Adipose tissue Mammary glands Photomicrograph: Adipose tissue from the subcutaneous layer under the skin (350x).

Nucleus of fat cell Vacuole containing fat droplet

(c) Connective tissue proper: loose connective tissue, reticular Description: network.

Network of reticular fibers in a typical loose ground substance; reticular cells lie on the Function: Fibers form a soft internal skeleton (stroma) that supports other cell types including white blood cells, mast cells, and macrophages.

Location: Lymphoid organs (lymph nodes, bone marrow, and spleen).

Spleen Photomicrograph: connective tissue fibers forming the internal skeleton of the spleen (350x).

Dark-staining network of reticular White blood cell (lymphocyte) Reticular fibers

(d) Connective tissue proper: dense connective tissue, dense regular Description: Primarily parallel collagen fibers; a few elastic fibers; major cell type is the fibroblast.

Function: Attaches muscles to bones or to muscles; attaches bones to bones; withstands great tensile stress when pulling force is applied in one direction.

Location: Tendons, most ligaments, aponeuroses.

Shoulder joint Ligament Tendon Photomicrograph: Dense regular connective tissue from a tendon (500x).

Collagen fibers Nuclei of fibroblasts

(e) Connective tissue proper: dense connective tissue, dense irregular Description: Primarily irregularly arranged collagen fibers; some elastic fibers; major cell type is the fibroblast.

Function: strength.

Able to withstand tension exerted in many directions; provides structural Location: Fibrous capsules of organs and of joints; dermis of the skin; submucosa of digestive tract.

Nuclei of fibroblasts Collagen fibers Fibrous joint capsule Photomicrograph: connective tissue from the dermis of the skin (400x).

Dense irregular

(f) Connective tissue proper: dense connective tissue, elastic Description: Dense regular connective tissue containing a high proportion of elastic fibers.

Function: Allows recoil of tissue following stretching; maintains pulsatile flow of blood through arteries; aids passive recoil of lungs following inspiration.

Location: Walls of large arteries; within certain ligaments associated with the vertebral column; within the walls of the bronchial tubes.

Aorta Heart Photomicrograph: Elastic connective tissue in the wall of the aorta (250x).

Elastic fibers

نازیزع دیشابن هتسخ

Classification of connective tissue

   Emberyonic (mesenchyme) Adult ( Loose- Dense) Dense( Regular- Irregular)

Elastic Fibers

      Staining (orsein) Chemical components:

oxytalan:

GP: fibromodolin 1,2 fibrilin Oxytalan+ elastin=

elaunin

Elaunin + elastin in core=

elastic

aa of elastin: Desmosin - isodesmosin  Disorders: marfan syndrom

Ground Substance

• • • An amorphous gel-like material it is not visible on slides, because it is removed during the preparation process composed of Glycosaminoglycans (GAG), Proteoglycans and multi adhesive Glycoproteins o

function

Glycosaminoglycans (GAGs) or mucopolysaccharides

 GAGs are negatively charged, long, rod-like chains of repeating disaccharides (Amino sugar + uronic acid) that have the capability of binding large quantities of water(hydrophilic)  GAGs consist of Hyaluronic acid, Dermatan sulfate, Chondroitin sulfate, Keratan sulfate, Heparan sulfate

Proteoglycan complex

 Constitute a family of macromolecules each is composed of a protein core to which GAGs are covalently bonded  (heparin( mast cell), Agrecan(ECM), Syndecans and fibroglycan(cell surface)  They have large volume like a bottle brush .

 Function: -Cell Binding to ECM

Glycoproteins

 They have binding site for several components of extracellular matrix as well as for: integrin molecules of the cell membrane that facilitate the attachment of cells to the extracellular matrix  (Fibronectin, Laminin, Chondronectin, Osteonectin, Entactin, Tenascin) • •

Fibronectin

is a v-shaped macromolecule that has binding site for extracellular components integrins of cell membrane,

 

Laminin

is very large has three polypeptide chains, it is located in basal lamina and has binding site for: heparan sulfate, type IV collagen, entactin and cell membrane

Fluid

 Edeme phenomen

Specific connective tissue

   Adipose tissue Bone and cartilage Blood

Adipose tissue (Fatty tissue)

 A kind of connective tissue with many adipocytes  Forms one of the largest “organs” of body  15-20% of body weight in men  20-25% of body weight in women  Over 2 times as much stored energy as glycogen  Subcutaneous adipose shapes body  Shock absorber in soles of feet and palms  Thermal insulation  Fills space between organs

Two Types of Adipose Tissue

 Yellow, White or unilocular  cells with one large fat droplet in cytoplasm  Brown or multilocular  cells with numerous smaller lipid droplets in cytoplasm and many mitochondria

Unilocular Adipose Tissue

 White to dark yellow depending on diet  Most common form in adults  Cells 50-150 mm diameter  Nuclei eccentric and flattened  Lipid droplet has no membrane  Heavily vascularized  Cell number constant after early postnatal period

Multilocular Adipose Tissue

 multiple droplets  vascularization and many mitochondria,  Central nucleus  Has a lobular organization like glands  Production of body heat by many mitochondria  In human neonate, produces heat