1. Connective Tissue

2. General Characteristics
most abundant and widely distributed of all the tissue types
binds structures, provides support and protection, serves as frameworks, fills spaces, stores fat, produces blood cells, protects against infection, and helps repair tissue damage
farther apart than epithelial cells

3. General Characteristics—cont.
variations in blood supply
most are well vascularized
tendons and ligaments have a poor blood supply
cartilages are avascular
have an abundance of extracellular matrix
produced by the connective tissue and then secreted to the exterior
could be liquid, semisolid or gel-like, or very hard
various types and amounts of fibers are deposited in the matrix

4. Major Cell Types in Connective Tissue
Fibroblasts
most common type of fixed cell in connective tissue
large, star-shaped
produce fibers by secreting proteins into the extracellular matrix
produce three types of fibers: collagenous fibers, elastic fibers, and reticular fibers
Before 1st bullet—Connective tissue contain a variety of cell types. Some are called fixed cells b/c they reside in the tissue for an extended period of time (fibroblasts and mast cells). Some are called wandering cells b/c they move through and appear in the tissues temporarily, usually in response to injury or infection (macrophages).

5. Major Cell Types in Connective Tissue
Macrophages
wandering cells that originate as white blood cells
specialized to carry on phagocytosis
can move about and function as scavenger and defensive cells that clear foreign particles from tissues
After 1st bullet—almost as numerous as fibroblasts in some connective tissues
After 2nd bullet—process by which a cell engulfs and digests solids
Pic—shows several macrophages starting to engulf a cell

6. Major Cell Types in Connective Tissue
Mast cells
large and widely distributed
usually located near blood vessels
release heparin, which prevents blood clotting, and histamine, which promotes some of the reactions associated with inflammation and allergies
After 1st bullet—fixed cell

7. Connective Tissue Fibers
Collageneous fibers
thick threads of the protein collagen
flexible, but only slightly elastic
great tensile strength
important parts of ligaments (which connect bone to bone) and tendons (which connect muscles to bone)
Before 1st bullet—Remember these are secreted by fibroblast cells.
After 3rd bullet—they resist considerable force
After 4th bullet—b/c of their tensile strength, they are found in body parts that hold structures together
Bonus Question: Why are collagenous fibers called white fibers? (found in dense connective tissue and such tissue appears white)

8. Connective Tissue Fibers
Elastic fibers
composed of the protein elastin
thin fibers that branch forming complex networks
weaker than collageneous fibers but can stretch easily and resume original length and shape
common in body parts that are frequently stretched, like the vocal cords
Reticular fibers
very thin collagenous fibers
highly branched and form delicate supporting networks
found in a variety of tissues, including the spleen
Bonus Question: Why are they called yellow fibers? (tissues supplied with them appear yellowish)
Read blue box on page 100.
See Table 5.4 on page 100 for Review

9. Loose Connective Tissue
also called areolar tissue
soft, pliable tissue that cushions and protects the body organs it wraps
considered a connective tissue “glue”
lies beneath most layers of epithelium, where its many blood vessels nourish nearby epithelial cells
When a body region is inflamed, the areolar tissue in the area soaks up the excess fluid like a sponge. The area swells and becomes puffy, a condition called edema.
Before 1st bullet—There are six types of connective tissue: loose connective tissue, adipose tissue, dense connective tissue, cartilage, bone, and blood.
After 3rd bullet—binds the skin to the underlying organs and fills spaces between muscles
After pictures—What are fibroblast cells? (cells that produce fibers) collagenous fibers are the thick threads of protein collagen; the elastic fibers are the thin, branching fibers that are made of elastin
See Figure 5.13 on page 101.

10. Adipose Tissue also called fat
specialized form of loose connective tissue that develop when certain cells store fat in droplets within their cytoplasm and enlarge
lies beneath the skin where it insulates and stores energy
cushions joints and some organs
Read under Adipose Tissue on page 101.
About pictures—Adipose tissue cells contain large fat droplets that push the nuclei close to the cell membranes.
See Figure 5.14 on page 101.

11. Dense Connective Tissue
also called dense fibrous tissue
has collagen fibers as its main matrix elements
crowded between the collagen fibers are rows of fibroblasts that manufacture the fibers
form strong, ropelike structures such as tendons and ligaments
blood supply is low
also makes up the
lower layers of skin
(dermis)
After 4th bullet—enables tissue to withstand pulling forces
After 4th bullet—where they bind bone to bone or muscle to bone
After 6th bullet—tissue repair is slow
See Figure 5.15 on page 102.

12. Cartilages less hard and more flexible than bone
only found in a few places in the body
several types in the body
hyaline cartilage—most widespread; attaches ribs to breastbone, and covers the ends of bones where joints are formed
elastic cartilage—found where a structure with elasticity is desired, such as the external ear
fibrocartilage—very tough tissue; forms the cushionlike disks between the vertebrae of the spinal column; shock absorber
See Figures 5.16 on page 102 and Figures 5.17 and 5.18 on page 103.
Read box on page 103.

13. Bone most rigid connective tissue sometimes called osseous tissue
composed of bone cells sitting in cavities called lacunae and surrounded by layers of a very hard matrix
has an exceptional ability to protect and support other body organs
See Figure 5.19 on page 104.

14. Blood
considered a connective tissue because it consists of blood cells, surrounded by a nonliving, fluid matrix called blood plasma
“fibers” of blood are soluble protein molecules that become visible only during blood clotting
transport vehicle for the cardiovascular system
See Figure 5.20 on page 105.
See Table 5.5 on page 105.
Have students complete questions 1-4 on page 102 and 1-3 on page 105.

15. Muscle Tissue contract in response to specific stimuli
muscle fibers shorten during contraction
three types of muscle tissue: skeletal, smooth, cardiac
After 3rd bullet—About 40% of the body is skeletal muscle, and almost another is smooth or cardiac muscle.

16. Skeletal Muscle found in muscles that attach to bones
form the flesh of the body
can be controlled voluntarily
pull on bones or skin when they contract which results in gross body movements or changes in facial expressions
cells are long, cylindrical and multinucleate with obvious striations
See Figure 5.21 on page 107.

17. Smooth Muscle Tissue no striations are visible
individual cells have a single nucleus and are spindle shaped
found in the walls of hollow organs such as the stomach, bladder, uterus and blood vessels
When smooth muscle contracts, the cavity of an organ alternately constricts and dilates so that substances are propelled through the organ along a specific pathway.
contracts more slowly than the other two muscles
involuntary movement
See Figure 5.22 on page 107.

18. Cardiac Muscle Tissue found only in the heart
As it contracts, the heart acts as a pump and propels blood through the blood vessels.
has striations like skeletal muscle, but cardiac cells are uninucleate and fit together tightly at junctions called intercalated disks
under involuntary control
See Figure 5.23 on page 108.

19. Nervous Tissue cells are called neurons
All neurons receive and conduct electrochemical impulses from one part of the body to another.
have a unique structure—drawn out cytoplasm into long extensions
make up the structures of the nervous system
See Figure 5.24 on page 109.
See Table 5.6 on page 108.
Read “Types of Membranes” on page 109—defining the four types of membranes.