Connective Tissue
• Found everywhere in the body; most abundant
and widely distributed of the primary tissues
• The dense layer of the basement membrane of all
epithelial tissues is created by connective tissue
• Connective tissue connects the epithelium to the
rest of the body
• Vary widely in appearance and function, but they
all share three basic components; specialized
cells, fibers, and ground substance
• Never exposed to the outside environment
Functions of Connective Tissue
 Establish a framework for the body
Transport fluids and materials
Protect organs
Support, surround, and interconnect other
types of tissue
Store energy reserves
Defend the body from invading
microorganisms
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)
• Fibers and ground substance together constitute
the matrix which surrounds the cells
Classification of Connective Tissues
• Classified on the basis of their physical
properties
Three general categories:
1. Connective tissue proper – includes tissues with many types of
cells and fibers in a ground substance
a. Loose connective tissues
b. Dense connective tissues
2. Fluid connective tissues – blood and lymph
3. Supporting connective tissues – less diverse cell population and
more densely packed fibers
a. Cartilage
b. Bone
Connective Tissue Prosper
• Sub-divisions:
1. Loose connective tissues (areolar, adipose,
and reticular)
2. Dense connective tissues (dense regular,
dense irregular, and elastic)
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Connective Tissue Proper: Loose
Areolar connective tissue (little space)
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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: 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
Connective Tissue Proper: Loose
Figure 4.8c
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
Connective Tissue Proper: Loose
Figure 4.8d
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
Connective Tissue Proper: Dense
Regular
Figure 4.8e
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)
Connective Tissue Proper: Dense
Connective Tissue Irregular
Proper: Dense Irregular
Figure 4.8f
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
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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: 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
Connective Tissue: Hyaline Cartilage
Figure 4.8g
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)
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
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)
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
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
Connective Tissue: Bone (Osseous
Tissue)
Figure 4.8j
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)
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