CONNECTIVE
TISSUES
• Most abundant type of tissue
• Fills internal spaces, provides
structural support for other tissues,
and stores energy reserves
• Includes tissues such as fat, bone,
and blood
• Most types are well vascularized
• All types have a common origin
(mesenchyme)
• Includes 3 components:
– specialized cells
– extracellular protein fibers
– ground substance
• fluid or semi-solid which
surrounds cells
3 Major Cell Types
1. Fibroblast
– Most common fixed
cell
– Large, star shaped
– Produces fibers by
secreting protein into
matrix
2. Macrophages
•
•
•
Wandering Cells that
originate as WBC’s
Function as
scavengers that clear
foreign particles 
Phagocytosis
Also, play a role in
immunity by allerting
other WBC’s of
foreign particles
3. Mast Cells
• Large, widely
distributed cells
• Associated with
inflammation
• Releases heparin
and histamine
CLASSIFICATION
• 3 CATEGORIES:
• Connective tissue proper
• tissue with many types of cells and extracellular fibers in a
syrupy ground substance ex. Adipose tissue
• Fluid connective tissue
• cells suspended in a watery matrix that contains dissolved
proteins ex. Blood
• Supporting connective tissue
• low diverse cell population and a matrix of closely packed
fibers ex. Bone and cartilage
CONNECTIVE TISSUE PROPER
• Composed of many kinds of cells
– Fibroblasts, Macrophages, Adipocytes
• 3 types of fibers
– Collagen - long, straight unbranched; flexible but strong
ex: tendons, ligaments
– Reticular – cells suspended in a watery matrix that contains
dissolved proteins Bone & Cartilage: stabilizes cells &
vessels
– Elastic - contains the protein “elastin”. Branched, wavy,
will contract after stretching ex: elastic ligaments
• Ground Tissue – high viscosity; slows the spread of pathogens to make them
easier for phagocytes to catch
Real life apps
Connective Tissue Proper
• Loose connective tissue
(areolar)
– characterized by white and
yellow fibers between
fibroblasts
– packing material of the
body, cushions, attaches
skin to the body, supports
blood vessels
• Adipose tissue
– dominated by
adipocytes
– energy storage, brown
fat in infants (highly
vascularized)
– each cell consists of
large vacuole filled
with triglycerides
• Reticular Connective
Tissue
– complex open
framework of reticular
fibers
• supports walls of organs
such as liver and spleen
• Dense Connective Tissue
– consists of many closely packed
collagen fibers, elastin fibers, and
few fibroblasts
• regular - collagen fibers are
parallel to each other
– tendons, ligaments
• irregular - collagen fibers
are randomly arranged and
interwoven : provides strength
to resist forces applied from
many directions; interwoven
meshwork
– dermis
Elastic Connective
Tissue
• - consists of mainly
yellow elastic fibers
– parallel or branching
– walls of hollow
organs, large arteries,
heart etc.
FLUID CONNECTIVE
TISSUES
• Ground substance –
plasma
• Blood contains formed
elements: Erythrocytes,
leukocytes, Platelets
• Arteries carry blood from
heart to capillaries, water
and solutes move into
interstitial fluid, Veins
• Erythrocytes: carry oxygen (confined to
vessels)
• Leukocytes: fight infection (wander)
• Platelets: blood clotting
Supportive Connective Tissue
Bone & Cartilage
• I.
–
–
–
–
Cartilage
Cells: Chondrocytes
Matrix: Firm gel of proteoglycans
Avascular: heals slowly
Covering: Perichondrium: Composed of 2 layers
• Outer layer: dense irregular tissue
• Inner layer: cells
– Growth: Interstitial & Appositional
• Appositional: undergoes extensive remodeling on a regular basis
• Interstitial:
– 3 main types
Hyaline - Tightly packed collagen fibers
– Most Common Type
– Looks like white glass
– Functions: Reduces friction, important in growth and
repair of bones
– Locations: Between bone surfaces, nose, trachea,
intercostal cartilage
• Elastic - Numerous elastic
fibers
– flexible
– Functions: Provides support but
distorts without damage
– Locations: Ears, nose, epiglottis
• Fibrocartilage - matrix
dominated by collagen fibers
– Extremely durable
– Functions: Resists compression,
limits movement
– Locations: Between vertebrae,
pads within knee joints
• II. Bone - Most rigid connective
tissue
– Cells - Osteocytes
– Matrix - 1/3 collagen fibers & mixture of
calcium salts
– Vascularized - caniculi - extensive blood
vessels in matrix for exchange of materials
– Covering - Periosteum (2 layers)
• fibrous outer layer
• cellular inner layer
– Growth - Appositional
• undergoes extensive remodeling on a regular
basis
• responds to stresses: grow thicker & stronger =
exercise