Connective Tissue

• Found everywhere in the body

• Includes the most abundant and widely distributed tissues

• Functions– Binds body tissues together– Supports the body– Provides protection

Connective Tissue Characteristics

• Variations in blood supply– Some tissue types are well vascularized– Some have poor blood supply or are

avascular

• Extracellular matrix– Non-living material that surrounds living cells

Extracellular Matrix

• Two main elements1. Ground substance – mostly water along with

adhesion proteins and polysaccharide molecules

2. Fibers

• Produced by the cells called fibroblasts• Three types

– Collagen fibers– Elastic fibers– Reticular fibers

Connective Tissue Types

1. Areolar Tissue– Most widely distributed connective tissue– Soft, pliable. A type of “Loose Connective

Tissue”– Contains all fiber types

– Binds skin to underlying organs– Fills spaces between muscles– Common connective tissue beneath epithelium

Figure 3.19e

Connective Tissue Types

2. Adipose tissue (fat)– Matrix is an areolar tissue in which fat

globules predominate– Many cells contain large lipid deposits

(Adipocytes)– Functions

• Insulates the body• Protects some organs (kidneys)• Serves as a site of energy storage

Connective Tissue Types

3. Dense connective tissue– Main matrix elements are closely packed collagen fibers– Cells are fibroblasts– Very strong tissue. – Poor blood supply. Long repair time

– Examples• Tendon – attach muscle to bone• Ligaments – attach bone to bone

Connective Tissue Types

4. Cartilage. A rigid connective tissue composed of cells called Chondrocytes surrounded by a rubbery matrix.

3 types, each with a different matrix

Figure 3.19b

Hyaline Cartilage

Most common cartilageComposed of: Abundant collagen fibers in a rubbery matrix

Locations:Entire fetal skeleton is hyaline cartilageEnds of bonesSoft part of nose

Elastic cartilage– Provides elasticity. More Elastin fibers– Example: supports the external ear

Fibrocartilage– Highly compressible, composed of tightly

packed collagen fibers

– Example: forms cushion-like discs between adjacent vertebrae

Figure 3.19c

Connective Tissue Types

5. Bone (osseous tissue)– Composed of:

• Bone cells called Osteocytes, in lacunae (cavities)

• Hard matrix of calcium phosphate cementing large numbers of collagen fibers together

– Used to protect and support the body– Site of blood cell formation– Store Calcium– Highly organized, excellent blood supply,

very active tissue, heals rapidly.

Connective Tissue Types

6. Blood– Blood cells surrounded by fluid matrix– Fibers are visible during clotting– Functions as the transport vehicle for

materials

Muscle Tissue

• Composed of elongated cells

• Have the ability to contract or shorten and produce movement

• Three types– Skeletal muscle– Cardiac muscle– Smooth muscle

Muscle Tissue Types

1. Skeletal muscle

– Can be controlled voluntarily– Attached to bones– Cells are long and threadlike (called fibers)– Cells are striated– Cells have more than one nucleus

(multinucleated)

Figure 3.20a

Muscle Tissue Types

2. Smooth muscle– Involuntary muscle (cannot be

consciously controlled)– Surrounds hollow organs (stomach,

intestines, blood vessels)– Attached to other smooth muscle cells– No visible striations– One nucleus per cell

Muscle Tissue Types

3. Cardiac muscle

– Found only in the heart– Function is to pump blood (involuntary)– Cells attached to other cardiac muscle

cells at intercalated disks– Cells are striated– One nucleus per cell– Does not need nervous stimulation to

contract.

Nervous Tissue

• Neurons and nerve support cells (neuroglia)

• Function is to send impulses to other areas of the body

– Irritability– Conductivity

Figure 3.21