Connective Tissue Loose connective tissue Blood…why? Cartilage Collagenous fiber Plasma White blood cells 120 m 55 m Elastic fiber Cartilage Red blood cells Fibrous connective tissue Chondrocytes 100 m Figure 40.5 Exploring: Structure and Function in Animal Tissues 30 m Chondroitin sulfate Nuclei Bone Adipose tissue Central canal Fat droplets 700 m 150 m Osteon 1

Connective Tissue Most diverse tissue type Binds together, supports and strengthens other tissues. Protects and insulates internal organs Compartmentalizes structures – e.g. skeletal muscles Major transport system – ? Store energy – ? Immune response – ? Two basic elements: cell and matrix – material between the cells. Matrix contains: protein fibers and ground substance – the material between the cells and the fibers. Nerve supply -- ? Usually highly vascular: Exceptions are cartilage and tendons.

Types of Cells Widely spaced – Not tight packed like epithelial cells. Fibroblasts that secrete the fibers and ground substance of the extracellular matrix Macrophages that are involved in the immune system (fixed and wandering) Mast cells produce histamine, a chemical that dilates small blood vessels as part of the inflammatory response – The body’s reaction to injury or infection. Adipocytes are fat cells

Extracellular Matrix Two main elements Ground substance – mostly water along with adhesion proteins and polysaccharide molecules Supports cells Binds cells together Exchange of substances between blood and cells Fibers Produced by the cells Three types Collagen fibers Elastic fibers Reticular fibers The matrix is firm in some parts of the body, but hard in others. Examples: ?

Fibers (this they should know)

Fibers Collagen Fibers Made of protein called collagen Strong yet flexible Resist pulling forces Found in: Bone Cartilage Tendons Ligaments

Fibers Elastic Fibers Thiner than collagen fibers Made of the protein, elastin Can be stretch without breaking Found in: Skin Blood vessels lungs

Fibers Reticular Fibers Much thinner than collagen fibers Provide support for stroma (covering) of soft organs Found in: Basement membrane Nerve fibers Muscles Spleen Lymph nodes

Connective Tissue Fibers Summary There are three types of connective tissue fiber, all made of protein: Collagenous fibers provide strength and flexibility Found in: tendon, ligament, skin, cornea, cartilage, bone, blood vessels, gut, and intervertebral disc. Elastic fibers stretch and snap back to their original length Found in: Skin, blood vessel walls, lung tissue Reticular fibers join connective tissue to adjacent tissues Found in: liver, bone marrow, lymphatic organs, basement membrane

Quiz Which type of protein are collagen fibers made of? Which type of fiber provides support for soft organs? Which type of protein are elastic fibers made of? Which type of fibers can be found in blood vessels? Which type of fiber provides the greatest strength?

Ground Substance Forms the material between the cells and fibers of connective tissue. Made of water, proteins, and polysaccharides Instrumental in how tissues: Develop Migrate Proliferate Change shape Metabolize

Connective Tissue Types six major types of connective tissue: Loose connective tissue Dense connective tissue Cartilage Bone Blood tissue Lymph

Loose Connective Tissue 3 types of loose connective tissue Areolar connective tissue Adipose connective tissue Reticular connective tissue

Areolar Connective Tissue Forms the subcutaneous layer – Attaches skin to the underlying tissues and organs Made of collagen, elastic and reticular fibers. Made of fibroblast, macrophages, plasma, mast cells and adipocytes (fat cells) Figure 3.19e

Adipose Tissue Cells store fat. Functions Insulates the body Protects some organs Serves as a site of fuel storage Does an obese person have more blood vessels? Figure 3.19f

Reticular Connective Tissue Delicate network of interwoven fibers Forms stroma of lymphoid organs Lymph nodes Spleen Bone marrow Bind together smooth muscle cells Filter worn out blood cells and bacteria.

Dense Connective Tissue More and thicker fibers but fewer cells than loose connective tissue Main matrix element is collagen fibers Cells are fibroblasts Examples Tendon – attach muscle to bone Ligaments – attach bone to bone Figure 3.19d

Dense Connective Tissue Dense Regular Fibers arranged in parallel – Regular Tendons and most ligaments Dense Irregular Fibers not parallel – Irregular Heart valves Elastic Can extend and return to original length Lungs, arteries

Connective Tissue Types Bone (osseous tissue) Composed of: Bone cells in cavities Hard matrix of calcium salts Large numbers of collagen fibers Used to protect and support the body

Connective Tissue Types Hyaline cartilage Most common cartilage Composed of: Abundant collagen fibers Rubbery matrix Entire fetal skeleton is hyaline cartilage Figure 3.19b

Connective Tissue Types Elastic cartilage Provides elasticity Example: supports the external ear

Connective Tissue Types Fibrocartilage Highly compressible Example: forms cushion-like discs between vertebrae Figure 3.19c

Connective Tissue Types Blood Blood cells surrounded by fluid matrix Functions as the transport vehicle for materials Figure 3.19h