Lecture notes on Connective tissues
by
Odokuma Emmanuel Igho
Lecturer, Dept of Human Anatomy and Cell Biology
Delta State University, Abraka
www.odokumaemmanuel.com
Introduction
• Connective tissue are tissues that
connect muscle and epithelium.
• Functions of connective tissues
–Provision of support (e.g. bone),
–Storage of energy (e.g. fat), and
–Distribution of nutrients (e.g.
blood).
–Protection (lymphoid tissue)
Components
• Specialized cells
• Extracellular protein fibers
• A fluid
substance
(extracellular)
ground
• The extracellular components form
the matrix surrounding the cells.
• This matrix constitutes most of the
volume of connective tissue.
• Matrix is a connective tissue cell’s
specific product,
• This
product
determines
its
specialized function.
Classification
• Cell type and arrangement
• Matrix type and arrangement
Classification
• Connective tissue proper
– Dense
• Regular
• Irregular
– Loose
• Areolar
• Reticular
• Specialised connective tissue (based on Cell and Matrix
type)
– Blood cell and plasma
– Osteocytes and bony matrix
– Chondrocytes and Cartilaginous matrix
• Others
Embryonic connective tissue
Connective tissue proper
• Dense connective tissue
– more fibres, less ground substance; – e.g. Tendons
• Loose connective tissue
– more ground substance, less fibers; – e.g. fat (adipose tissue)
• Cells of CT Proper
– The predominant cell in CT proper is the
• Fibroblast others are ; Mast, Melanocytes,
Lymphocytes ,Microphages, Macrophages,
Adipocytes, Mesenchymal stem cells
• Fibres of CT Proper
• Collagen
• Reticulin
• Elastic
• The type and arrangement of these fibres forms
the basis for the classification of CT Proper into
• Dense CT
• Loose CT
Fibers in connective tissue proper:
1. Collagen fibers:
– The most common fibers in connective
tissue proper.
– Long, straight and un-branched
– Strong and flexible;
– Resists force in one direction - examples:
tendons and ligaments
2. Reticular fibers:
–Similar to collagen fibers but shaped
differently.
–network of branching, interwoven
fibers (stroma);
–strong and flexible;
–resists force in many directions;
–stabilizes the positions of functional
cells (parenchyma) and structures
3. Elastic fibers:
• Contain the protein elastin.
• Branched and wavy;
• Return to original length after stretching
• Example: elastic ligaments of vertebrae
Dense connective tissues
There are 2 forms of dense connective
tissue:
• Dense regular
–Collagenous
–Elastic
• Dense irregular
–Collagenous
–Elastic
Dense regular connective tissue
•
Has tightly packed, parallel collagen fibers.
Tendons attach muscles to bones.
Ligaments connect one bone to another,
Aponeuroses which ensheet Large flat
muscles
Dense regular
Dense regular
Dense regular
2. Dense irregular connective tissues
• Possess interwoven networks of fibers.
• Distributed in the
• Skin,
• Perichondrium
• Periosteum),
• Forms capsules around some organs
Loose connective tissue
• Areolar
• Reticular
• Adipose
Areolar tissue (areola = little space)
• Open framework distorts without
damage
• Viscous ground substance absorbs shock
• Elastic fibers return to original shape
• Holds blood vessels and capillary beds
• Example: separates skin from deeper
structures
Adipose tissue (fat)
• Similar to areolar tissue but contains many
adipocytes (fat cells) which store fat.
• Adipose tissue also absorbs shocks and slows
heat loss. –
• There are 2 types of adipose tissue:
• (1) white fat, the most common adipose
tissue,
• (2) brown fat, a more vascularized tissue with
adipocytes containing many mitochondria.
Reticular tissue
• Reticular tissue has a complex, 3dimensional network of supportive
fibers (stroma).
• The stroma support functional cells
(parenchyma).
• Reticular organs include spleen, liver,
lymph nodes and bone marrow.
Specialised CT
• Fluid
– blood
• Supportive
– Cartilage
– Bone
Fluid Connective Tissues
• The fluid connective tissues are
liquids carrying specialized cells and
suspended proteins.
Fluid connective tissue
• Composed of
+ Fluid matrix
Dissolved proteins,
+Specific cell types.
• There are 2 types of fluid connective
tissues:
– blood
– lymph
• Blood consists of solids (formed
elements) and matrix (fluid elements).
There are 3 types of formed elements in
blood:
• Red blood cells (erythrocytes)
• White blood cells (leukocytes)
• Platelets
• The fluid element of blood is the watery
matrix called plasma.
• Extracellular fluid of blood is called
plasma
• Extravascular matrix fluid is termed
interstitial fluid.
• Interstitial fluid drains into the lymphatic
vessels - lymph.
Supportive connective tissues
• support soft tissues and the weight
of the body.
• The 2 types of supportive connective
tissues are:
–Cartilage: a gel-type ground substance
with
various
fibers
for
shock
absorption and protection.
–Bone: which is calcified for weight
support.
• Cartilage matrix consists of proteoglycans
derived
from
polysaccharides
(chondroitin sulfates) and ground
substance proteins.
• Cartilage
cells
in
the
matrix
(chondrocytes) are surrounded by
chambers called lacunae.
• Cartilage has no blood vessels
• Chondrocytes produce an anti-growth
chemical (antiangiogenesis factor).
• The perichondrium, consists of an outer,
fibrous layer (for strength) and
• An inner, cellular layer (for growth and
maintenance).
Types of cartilage
• Hyaline
• Fibrous
• Elastic
(1) Hyaline cartilage is translucent and has
no prominent fibers.
• Provides stiff, flexible support.
• Reduces friction between bones.
• Found in synovial joints, rib tips, sternum
and trachea
(2) Elastic cartilage
• Has tightly packed elastic fibers.
• Supportive but bends easily.
• Found in the external ear and
epiglottis.
(3) Fibrocartilage
• Very dense collagen fibers.
• Limits movement and prevents boneto-bone contact.
• Found in
–pads knee joints,
–pubic bones and intervertebral discs.
Cartilage
Hyaline
Elastic
Fibrous
Cellularity
Moderate,
Moderate
sized
Round to
oval;
in clusters
Abundant;
Sparse;
Large sized, spindled;
Round to
In singles
oval;
In singles
Fiber
Sparse
Moderate
Abundant
G Substance
Abundant
Moderate
Sparse
Bone
• Bone or osseous tissue is strong
because of calcification (calcium
salt deposits),
• It resists breakage due to its
flexible collagen fibers. -
• Osteocytes are arranged around
blood vessels in central canals within
the matrix.
• Small channels through the matrix
(canaliculi) allow osteocytes to
exchange nutrients and wastes with
their blood supply.
• A periosteum (with a fibrous layer
and a cellular layer) covers the
surface of most bones.
• Unlike
cartilage,
bone
is
metabolically active, and can repair
itself or adapt to activity.
Embryonic connective tissues
These are
–Mesenchyme or
–Embryonic stem cells
The first connective tissue to appear in
embryos.
Summary