1. Connective Tissue
Forms metabolic and structural connections between tissues
Found ___________ in the body and represents most abundant tissue by weight.
Examples: Blood, tendons, fat, cartilage, bone
Some systems are almost exclusively composed of connective tissue
Skeletal, integumentary
Derived from _____________
Is vascularized.
Loose & Adipose = good supply, Dense = poorly supplied
Form and function may vary
can be elastic and flexible, rigid, semisolid, liquid
Reserve for energy, protective sheath, provides framework of structural support, transport medium, promotes healing, controls foreign invaders

2. Connective Tissue Components
3 major components of connective tissue:
Extracellular fibers, Ground substance, Cells
Extracellular Matrix = Extracellular fibers + Ground substance
Matrix surrounds and separates the cells, providing important structural and nutritional support to them, allowing them to be farther apart than epithelial cells.
1. Extracellular fibers
Collagenous, Reticular, Elastic
2. Ground substance
Liquid, solid, or gel
3. Cells
Fixed cells
Fibroblasts, Adipocytes (fat cells), Reticular cells
Wandering cells
Mast cells, Leukocytes (white blood cells), Macrophages (fixed and wandering)

3. Connective Tissue Components: Ground Substance
An amorphous, homogenous material that ranges from ______ to _____ to _______.
Composed of glycoproteins called __________________ (GAGs)
hyaluronic acid
Help to orient fiber formation in connective tissue.
Is medium through which cells exchange nutrients and waste with the bloodstream.
Acts as ______ absorbing cushion and helps to protect the delicate cells that it surrounds.
Serves as obstacle for invading microorganisms.

4. Fibers of Connective Tissue
Collagenous:
Most common fiber found in the body
Strong, thick bands composed of collagen (structural protein).
Organized into bundles
Resist pulling forces, so they are found in tendons and ligaments that are continuously being pulled and stretched.
wavy appearance when not stretched
Sometimes called white fibers
Density and arrangement can vary
depending on tissue function.
Loose around organs to dense within
tendons.

5. Fibers of Connective Tissue
Reticular:
Composed of collagen, but are not thick
Thin, delicate, branched into complicated networks.
Form support for around highly cellular organs
endocrine glands, lymph nodes, spleen, bone marrow, liver
Found around blood vessels, nerves, muscle fibers, capillaries
Elastic:
Composed primarily of protein elastin.
Are branched and form networks
Can stretch and contract.
Found in tissues that stretch: vocal cords, lungs, skin, blood vessel walls.
May be referred to as yellow fibers.

7. Major Cell Types of Connective Tissue
Fixed Cells:
Remain in the connective tissue
Produce and maintain the matrix
Fibroblast:
secrete fibers and ground substance of the matrix
Can reproduce and are metabolically active.
Name is based on location
Chondroblast (cartilage), osteoblast (bone), etc.
As the cells mature and the matrix is formed, cells become less active and are called –cytes.
Chondrocyte, osteocyte, fibrocyte
Can revert back to blast if more matrix is needed.

8. Major Cell Types of Connective Tissue
Fixed cells continued.
Adipose cells/Adipocytes:
Found throughout connective tissue
Resemble fibroblasts early on, but as they age they become filled with lipid and swell.
nucleus gets pushed to the side
Adipocytes clustered together form adipose tissue.
found all over, but is prominent under the skin, behind the eyes, around the kidneys, and in the abdomen
Reticular Cells:
Flat, star-shaped cells that form net-like connections with other cells
Manufacture of reticular fibers.
Found in tissues of the immune system: lymph nodes, spleen, bone marrow

9. Major Cell Types of Connective Tissue
Wandering Cells:
Move in and out of connective tissue as needed.
Leukoctyes: (white blood cells)
Found in blood and move into connective tissue during periods of infection.
Squeeze through the simple squamous epithelium of blood vessels (diapedesis)
Important in immune function- engulf and digest invaders or produce antibodies against them
Mast cells
Carry histamine and heparin granules which initiate inflammatory response when released into tissue
Usually found near blood vessels

10. Major Cell Types of Connective Tissue
Wandering cells continued..
Macrophages:
Phagocytotic scavengers that may be either fixed or transient in connective tissue.
Engulf microbes, dead cells and debris that are digested by the macrophage’s lysosomes
drawn to sites of infection where they engulf invaders
Given different names depending on locations
Kupffer cells in liver, microglial cells in brain