2. Characteristics of Connective
Tissue
• Most abundant tissue in the body
• Vascular
• Cells scattered widely in extra-cellular
matrix
• Does not occur on free surfaces
3. Connective Tissue
Functions
• Binds one kind of tissue to another (loose
connective tissue, tendons)
• Support (bone and cartilage)
• Physical protection (bones, adipose tissue)
• Immune protection (white blood cells)
4. Classification of Connective
Tissue
• Connective tissue
proper
– Loose or areolar
– Dense irregular
connective tissue
(dermis of the skin)
– Dense regular
connective tissue
a.) collagenous
(tendons)
b.) elastic
– Reticular
– Adipose
• Specialized connective
tissue
– Hyaline cartilage
– Elastic cartilage
– Fibrocartilage
– Bone
– Blood
5. Basic Components
of Connective Tissues
• Cells
• Protein Fibers
• Ground
Substance
Together, the protein
fibers and ground
substance are
referred to as the
“extracellular
matrix”
6. Major Cell Types
within Connective Tissue Proper
• Fibroblasts – the most common cell type within C.T.
Synthesize fibers and ground substance
• Macrophages – Derived from monocytes which leave the
bloodstream and enter tissue. Function as phagocytes that
destroy bacteria
• Mast Cells – specialized WBCs that contain granules of heparin
(anticoagulant) and histamine (vasodilator). Mediate
inflammation.
• Plasma Cells – derived from B lymphocytes and are responsible
for synthesis of antibodies
• Leukocytes – WBCs that migrate into C.T. by diapedesis,
especially during inflammation
• Adipose (fat) cell – stores fat (triglycerides)
7. Connective Tissue Cells
Quiescent fibroblasts (“fibrocytes”)
are elongated cells with thin
cytoplasmic extensions
Mast cells are oval C.T. cells
which are filled with granules
which, when released, trigger
inflammation
8. Connective Tissue Cells
The nucleus of plasma cells is spherical and eccentrically placed containing an
arrangement of chromatin that resembles the face of a clock. The pale area of
cytoplasm (arrows) is the location of the Golgi apparatus. The darker basophilic areas
represent mostly rough endoplasmic reticulum involved in synthesis of antibodies.
9. Fibers
- Collagenous: made of the protein collagen (most
abundant protein in the body); form the bulk of
tendons and ligaments (called “white fibers”
because they look white in living tissue)
– Elastic: made of the protein elastin; allow stretch
and recoil (called “yellow fibers). Found in skin,
blood vessel walls, and lungs.
– Reticular: made up of thinner collagen fibers
coated with glycoprotein; form a scaffold-like
framework in organs. Not visible in routine H&E
stains. Abundant in reticular connective tissue
which forms the “stroma” (a scaffold-like support
framework) of soft organs such as spleen &
lymph nodes.
10. Ground Substance
• Ground substance: component of C.T., an
amorphous substance that fills the spaces
between the cells and fibers.
• May be fluid, semifluid, gelatinous, or
calcified.
• Supports cells, binds them together, stores
water, and provides a medium through
which substances are exchanged between
blood and cells.
11. Ground Substance
• Contains water and and assortment of large
organic molecules:
– GAGs (glucosaminoglycans) – polysaccharides
which trap water, making the ground substance
more jelly-like. Ex. hyaluronic acid (component
of synovial fluid which lubricates joints
– Proteoglycans – core proteins to which GAGs
are attached. Examples: chondroitin sulfate
(gives cartilage its stiffness), and dermatan
sulfate.
14. Loose (Areolar) Connective
Tissue
• Widely distributed, well-vascularized
• Major function is to connect adjacent
structures of the body
• Stretchable and easily pulled apart during
dissection
• Locations include lamina propria of mucous
membranes, hypodermis, serosal linings of
peritoneal and pleural cavities, and superficial
fascia
17. Dense Irregular Connective
Tissue
• Composed primarily of dense bundles of
collagenous fibers interwoven in irregular,
swirling arrangements that can withstand
stresses applied from any direction
• Major cell type is the fibroblast
• Locations include the dermis (inner layer of
the skin), fibrous capsule of organs and
joints, and deep fascia surrounding muscles
19. Dense Regular Connective
Tissue
• Also called “collagenous dense regular
fibrous tissue”
• Composed primarily of parallel collagen
fibers which withstand a considerable
amount of tensile stress when the pulling
force is applied in one direction
• Major cell type is the fibroblast
• Locations include ligaments, tendons, and
aponeuroses
22. Elastic Connective Tissue
• Sometimes referred to as “elastic dense regular
connective (fibrous) tissue”
• Composed of parallel arrangement of primarily
elastic fibers. Space between fibers is filled
with thin collagen fibers and fibroblasts
• Limited distribution - yellow ligaments of
vertebral column, walls of some arteries
24. Reticular Connective Tissue
• A three dimensional web (the word reticular means
“like a net”) composed of slender, branching
reticular fibers forming the stroma of the bone
marrow and lymphoid organs (spleen, lymph nodes)
• Associated with specialized fibroblasts called
reticular cells which partially cover the reticular
fibers with cytoplasmic processes – creating cell-
lined spaces through which blood or lymph
percolates
• Macrophages, lymphocytes, and plasma cells are
abundant
27. Adipose Tissue
• Type of C.T. in which adipocytes (fat cells)
predominate
• Stores energy in the form of triglycerides
• Provides thermal insulation and supports and
protects organs
• Locations include hypodermis (tissue), around
kidneys and eyeballs, abdomen, breasts, and
other genetically determined areas (e.g. hips or
thighs)
30. Cartilage
• 3 types
- Hyaline cartilage – most abundant type, found in
ribs (costal cartilage), the growth plates
(epiphyseal plates) of bones, respiratory passages
(tracheal rings, bronchi), nose
- Elastic cartilage – external ear (pinna), epiglottis,
eustachian tube
- Fibrocartilage – intervertebral discs, menisci of
knees, pubic symphysis
31. Characteristics of Cartilage
• Major cell type is the chondrocyte housed within
spaces called lacunae (the young active form of
the cell is the chondroblast)
• Avascular – note that this is an exception to the
rule that C. T. is vascular, so cartilage heals slowly
• Extracellular matrix varies as to the type of fiber
depending on the function of the cartilage.
Fibrocartilage has collagen fibers which impart
greater strength to provide for weight–bearing.
Editor's Notes
Areolar tissue
Three large, dark mast cells in a stretched preparation of areolar connective tissue. In H & E the secretory granules stain a deep red color. Most of the other nuclei in the field belong to fibroblasts.
