Connective Tissue

• Found everywhere in the body• Most abundant and widely distributed of the

primary tissuesMajor functions:• Binding and support (bone and cartilage)• Protection (bone and cartilage)• Insulation (fat)• Transportation of substances (blood)

Structural Elements of Connective Tissue

• Ground substance – unstructured material that fills the space between cells and contains the fibers

• Fibers – provide support (collagen, elastic, or reticular)• Cells – fibroblasts (connective tissue proper),

chondroblasts (cartilage), osteoblasts (bone), hematopoietic stem cells (produces blood cells), and accessory cells (mast cells = cluster along blood vessels that detect foreign microorganisms; macrophages = “eat” foreign materials)

Connective Tissue Prosper

• Sub-divisions: 1. Loose connective tissues (areolar, adipose, and reticular)2. Dense connective tissues (dense regular, dense irregular, and elastic)

*Except for blood, all mature connective tissues belong to this class

Connective Tissue Proper: LooseAreolar connective tissue (little space)

Most widely distributed connective tissue Supports and binds other tissues Holds body fluids Defends against infection Stores nutrients Functions as a universal packing tissue and

connective tissue “glue” because it helps to hold the internal organs together and in their proper positions.

Connective Tissue Proper: Loose

Figure 4.8b

Connective Tissue Proper: LooseAdipose connective tissue (“white fat”)• 90% of tissue’s mass is made of fat cells • Cells are packed closely together• Richly vascularized (high metabolic activity)• Abundant (approx. 18% of an average person’s

body weight)• Acts as a shock absorber• Provides insulation• Stores energy• Prevents heat loss from body

Connective Tissue Proper: Loose

Figure 4.8c

Connective Tissue Proper: LooseReticular connective tissue• The only fibers in its matrix are reticular fibers

(reticular cells are scattered along)• Limited to certain sites• Forms a stroma (internal framework) that

supports many blood cells in lymph nodes, spleen, and bone marrow

Connective Tissue Proper: Loose

Figure 4.8d

Connective Tissue Proper: DenseDense Regular:• Parallel collagen fibers with a few elastic fibers• Provides great resistance to tension• Attaches muscles to bone or to other muscles,

and bone to bone Tendons – attach skeletal muscles to bone

Ligaments – connect bones to bones at joints

Aponeuroses – sheet like tendons; attach muscles to other muscles or bones

Connective Tissue Proper: Dense Regular

Figure 4.8e

Dense Irregular:

•Irregularly arranged collagen fibers with some elastic fibers•Forms sheets in body areas where tension is exerted from many different directions•Found in the dermis (skin), digestive tract, fibrous joint capsules, and the fibrous coverings that surround some organs (kidneys, bones, cartilages, muscles, and nerves)

Connective Tissue Proper: Dense

Connective Tissue Proper: Dense Irregular

Figure 4.8f

Connective Tissue Proper: Dense Irregular

Connective Tissue Proper: Dense

Elastic: • High proportion of elastic fibers• Allows recoil of tissue following stretching,

maintains blood flow through arteries and recoil of lungs following inspiration

• Found in walls of large arteries, walls of bronchial tubes and some ligaments of the vertebral column

Connective Tissue: Cartilage

• Stands up to both tension and compression• Tough, but flexible• Lacks nerve fibers • Avascular• Receives nutrients by diffusion from blood

vessels located in the connective tissue membrane surrounding it

Connective Tissue: CartilageHyaline cartilage:

– Made up of Collagen fibers• Most abundant form of cartilage in the body• Covers the ends of long bones (articular cartilage)• Supports the tip of the nose, connects the ribs to the

sternum, and supports most of the respiratory system passages• Most of the embryonic skeleton is formed of hyaline

cartilage before bone is formed

Connective Tissue: Hyaline Cartilage

Figure 4.8g

Connective Tissue: CartilageElastic Cartilage:• Similar to hyaline cartilage but with more elastic

fibers• Found where strength and “stretchability” are

needed• Forms the external ear and the epiglottis (flap

that covers the opening to the respiratory passageway when we swallow)

Connective Tissue: Elastic Cartilage

Figure 4.8h

• Similar to hyaline cartilage but with more elastic fibers

• Maintains shape and structure while allowing flexibility

• Supports external ear (pinna) and the epiglottis

Connective Tissue: Cartilage

• Structural intermediate between hyaline cartilage and dense regular connective tissues

• Compressible and resists tension well• Found where strong support and the ability to

withstand heavy pressure are required• Intervertebral discs & spongy cartilage of the

knee (menisci)

Fibrocartilage:

Connective Tissue: Fibrocartilage

Figure 4.8i

• Matrix similar to hyaline cartilage but less firm with thick collagen fibers

• Provides tensile strength and absorbs compression shock

• Found in intervertebral discs, the pubic symphysis, and in discs of the knee joint

Connective Tissue: Bone

• Supports and protects body structures• Rocklike hardness• Provide cavities for fat storage and synthesis

of blood cells• Well supplied by invading blood vessels

Bone (Osseous Tissue):

Connective Tissue: Bone (Osseous Tissue)

Figure 4.8j

Connective Tissue: Blood

• Fluid within blood vessels• Most atypical connective tissue (does not

connect things or give mechanical support)• Functions as the transport vehicle for the

cardiovascular system (carries nutrients, wastes, and respiratory gases)

Blood or vascular tissue:

Connective Tissue: Blood

Figure 4.8k

Connective Tissue: Nervous Tissue• Main component of the nervous system (brain,

spinal cord, and nerves)• Regulates and controls body functions

Nervous Tissue

Figure 4.10