1. Connective Tissues

2. Connective Tissue Found everywhere in the body
Most abundant and widely distributed of the primary tissues
Major functions:
Binding and support (bone and cartilage)
Protection (bone and cartilage)
Insulation (fat)
Transportation of substances (blood)

3. 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)

4. 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

5. Connective Tissue Proper: Loose
Areolar 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.

6. Connective Tissue Proper: Loose
Figure 4.8b

7. Connective Tissue Proper: Loose
Adipose 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

8. Connective Tissue Proper: Loose
Figure 4.8c

9. Connective Tissue Proper: Loose
Reticular 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

10. Connective Tissue Proper: Loose
Figure 4.8d

11. Connective Tissue Proper: Dense
Dense 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

12. Connective Tissue Proper: Dense Regular
Figure 4.8e

13. Connective Tissue Proper: Dense
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)

14. Connective Tissue Proper: Dense Irregular
Figure 4.8f

15. 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

16. 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

17. Connective Tissue: Cartilage
Hyaline 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

18. Connective Tissue: Hyaline Cartilage
Figure 4.8g

19. Connective Tissue: Cartilage
Elastic 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)

20. Connective Tissue: Elastic Cartilage
Similar to hyaline cartilage but with more elastic fibers
Maintains shape and structure while allowing flexibility
Supports external ear (pinna) and the epiglottis
Figure 4.8h

21. Connective Tissue: Cartilage
Fibrocartilage:
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)

22. Connective Tissue: Fibrocartilage
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
Figure 4.8i

23. Connective Tissue: Bone
Bone (Osseous Tissue):
Supports and protects body structures
Rocklike hardness
Provide cavities for fat storage and synthesis of blood cells
Well supplied by invading blood vessels

24. Connective Tissue: Bone (Osseous Tissue)
Figure 4.8j

26. Connective Tissue: Blood
Blood or vascular tissue:
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)

27. Connective Tissue: Blood
Figure 4.8k

28. Connective Tissue: Nervous Tissue
Main component of the nervous system (brain, spinal cord, and nerves)
Regulates and controls body functions

29. Nervous Tissue
Figure 4.10