Connective Tissue Chapter 4 (cont.)

I. General Characteristics A. Three components: 1. Specialized cells 2. Extracellular protein fibers 3. Ground substance * Extracellular fibers & ground substance together make up the matrix, which surrounds the specialized cells.

B. Never exposed to the outside environment C. Highly vascular D. Provide pain, pressure, temperature & other sensations E. Make up the framework of the body

F. Transport fluids & dissolved materials G. Protect organs H. Support, surround, and interconnect other tissues I. Defend against microorganisms

II. Classification of C.T. A. Connective Tissue Proper (C.T.P.) 1. There are many different types, depending on proportion of cells, fibers, & ground substance.

2. Cell Types a. Fibroblasts i. Most abundant, permanent cell in CTP ii. Only cell that is ALWAYS in every CTP b. Macrophages i. Large cells scattered in matrix ii. Engulf pathogens and damaged cells iii. Play an important role in the immune system

c. Adipocytes- adipose cells (fat cells) d. Mesenchymal cells i. Stem cells ii. Respond to local injury or infection

e. Melanocytes i. Make and store melanin ii. Common in epithelium of skin, determines skin color iii. Also in eye

f. Mast cells i. Small, mobile cells ii. Found near blood vessels iii. Release chemicals (like histamine) to stimulate inflammation after injury or infection g. Lymphocytes i. Migrate throughout the body ii. May turn into plasma cells, which make antibodies h. Microphages- help out macrophages

3. Connective Tissue Fibers (all formed by fibroblasts) a. Collagen fibers i. Long, straight, unbranched ii. Most common fibers in CTP iii. Fibers are like strands in a rope iv. Flexible, yet VERY strong Tendons- connect muscle to bone Tendons- connect muscle to bone Ligaments- connect bone to bone Ligaments- connect bone to bone Bones will usually break before T&L will! Bones will usually break before T&L will!

b. Reticular Fibers i. Thinner than collagen fibers ii. Branched network that stabilizes positions of blood vessels, nerves… c. Elastic Fibers i. Contain the protein elastin ii. Fibers are branched and wavy

4. Ground Substance a. Fills spaces between cells, surrounds fibers b. Viscous, clear fluid, slows spread of pathogens

5. Lose Connective Tissue (Areolar) a. Packing material of the body b. Cushions & supports organs & tissues c. Contains elastic fibers d. Forms a layer that separates skin from muscle e. Common injection site of drugs

* Adipose Tissue- padding, shock absorbing, insulating * Reticular Tissue

Fibroblasts - - Magenta arrow Elastic fibers - - Red/Orange arrow Macrophages - - Green arrow Collagen - - Blue arrow

a. Dense Regular Connective Tissue i. Parallel fibers ii. Ex. Tendons, Ligaments b. Dense Irregular Connective Tissue i. Interwoven mesh ii. Ex. Skin, Leather

B. Fluid Connective Tissue- cells suspended in a watery matrix w/ dissolved proteins. 1. Blood a. Erythrocytes- i. red blood cells (RBC) ii. Make up ½ of the volume of blood iii. Carry Oxygen b. Plasma- watery ground substance c. Leukocytes a. White blood cells (WBC) b. Immune system component d. Platelets- function in clotting

2. Lymph a. Interstitial fluid that enters back into the blood stream b. Carries messages of injury/infection to immune system

C. Supporting Connective Tissues- Closely packed cells 1. Chondrocytes- cartilage cells 2. Lacunae- small chambers that chondrocytes occupy

3. Cartilage- firm gel, avascular a. Hyaline Cartilage i. Most common type ii. Made of closely packed collagen fibers iii. Tough, but flexible iv. Found between ribs & sternum, nose, elbow, knee

Hyaline Cartilage

b. Elastic Cartilage i. Extremely resilient & flexible ii. Found in ears, & larynx

c. Fibrocartilage i. Made of densely interwoven collagen fibers ii. Extremely tough & durable iii. Found between vertebrae, knee

4. Bone- composed of calcium, other minerals & collagen a. Osteocytes- bone cells b. Canaliculi i. Branching network of cytoplasmic extensions ii. Transfer materials between blood vessels & osteocytes c. Periosteum- sheath around bones

Bone