types of connective tissue include proper and specialized

1. Lecture 4
M.Sc Hamid AL-Tameemi

2. Connective tissue
Connective tissue: is the tissue that connects, separates
and supports all other types of tissues in the body. Like
all tissue types, it consists of cells surrounded by a
compartment of fluid called the extracellular matrix
(ECM)(fibers and ground substances).

3. Basic Components of General Connective Tissue
Many tissues and organs of the body are made up mainly
of aggregations of closely packed cells e.g., epithelia, and
solid organs like the liver.
In contrast, cells are relatively few in connective tissue,
and are widely separated by a prominent intercellular
substance. Connective tissue can assume various forms
depending upon the nature of the ground substance,
and of the type of fibres and cells present.

8. Fibres in connective tissue
The most conspicuous components of connective tissue
are the fibres within it. These are of three main types.
1- Collagen fibres are most numerous. They can be
classified into various types.
Physical Properties
Collagen fibres can resist considerable tensile forces (i.e.,
stretching without significant increase in their length.
At the same time they are pliable and can bend easily.

10. 2-Reticular Fibres
These fibres are a variety of collagen fibre (type III). They
show periodicity (striations) of 67 nm. They differ from
typical (Type I) collagen fibres as follows.
(1) They are much finer.
(2) They are uneven in thickness.
(3) They form a network (or reticulum) by branching, and by
anastomosing with each other. They do not run in bundles.

11. 3-Elastic fibres.
Elastic fibres are much fewer than those of collagen.
They run singly (not in bundles), branch and
anastomose with other fibres. Elastic fibres are thinner
than those of collagen (0.1-0.2 μm).
Physical Properties
As their name implies elastic fibres can be stretched
(like a rubber band) and return to their original length
when tension is released. They are highly refractile and
are, therefore, seen as shining lines in unstained
preparations.

12. Types of Connective Tissue
Different combinations and densities of the cells,
fibers, and extracellular macromolecules just
described produce graded variations in histological
structure within connective tissue. Descriptive names or
classifications used for the various types of connective
tissue denote either a major component or a structural
characteristic of the tissue..
Adipose tissue, an important specialized connective
tissue, and two other supporting tissues, cartilage and
bone.

14. Connective Tissue Proper
In adults there are two general classes of connective
tissue proper,
1- loose connective tissue.
2- dense connective tissue.

15. Loose connective tissue
is very common and generally supports epithelial tissue.
It comprises a thick layer (the lamina propria) beneath
the epithelial lining of the digestive system and fills the
spaces between muscle and nerve fibers .
Usually well-vascularized whatever their location, thin
layers of loose connective tissue surround most small
blood vessels of the body.

17. Dense connective tissue
is adapted to offer stress resistance and protection. It
has the same components found in loose connective
tissue, but with fewer cells and a clear predominance of
collagen fibers over ground substance. Dense connective
tissue is less flexible and far more resistant to stress than
loose connective tissue

18. a-dense irregular connective tissue
bundles of collagen fibers appear randomly interwoven,
with no definite orientation. The collagen fibers form a
tough three-dimensional network, providing resistance
to stress from all directions

19. b- dense regular connective tissue
bundle of fiber are arranged according to a definite
pattern, with fibers and fibroblasts aligned in parallel for
resistance to prolonged or repeated stresses exerted in
the same direction .
Common examples of dense regular connective tissue,
such as tendons and ligaments, are strong, flexible
straps or cords that hold together components of the
musculoskeletal system. Overall, however, tendons are
poorly vascularized and repair of damaged tendons is
very slow.

21. Blood and cartalige
M.Sc Hamid Al-Tameemi

22. blood
blood is a specialized connective tissue in which cells
are suspended in fluid extracellular material called
plasma . Propelled mainly by rhythmic contractions
of the heart, about 5 L of blood in an average adult
moves unidirectionally within the closed circulatory
system. The so-called formed elements circulating in the
plasma are erythrocytes (red blood cells), leukocytes
(white blood cells), and platelets .

23. COMPOSITION OF PLASMA
Plasma is an aqueous solution, pH 7.4, containing substances
of low or high molecular weight that make up 7% of its
volume. Th e major plasma proteins include the following:
■ Albumin , the most abundant plasma protein, is made in
the liver .
■ α-Globulins and a-globulins , made by liver and other cells.
■ Ɣ –Globulins, which are immunoglobulins (antibodies)
secreted by plasma cells.
■ Fibrinogen , the largest plasma protein (340 kD), also made
in the liver.
■ Complement proteins , a system of factors important in infl
ammation and destruction of microorganisms

25. Cartilage
Different functional requirements have selected for the
three major forms of cartilage, each varying somewhat in
matrix composition. In hyaline cartilage , the most
common form, type II collagen is the principal collagen
type ( Figure 7–1 ). The more pliable and distensible
elastic cartilage possesses abundant elastic fibers in
addition to collagen type II.

26. Fibrocartilage , present in body regions subjected to
pulling forces, is characterized by a matrix containing a
dense network of coarse type I collagen fibers.

27. In all three forms, cartilage is avascular and receives
nutrients by diff usion from capillaries in adjacent
connective tissue (perichondrium). In some instances,
large blood vessels traverse cartilage to supply other
tissues, but these vessels release few nutrients to the
cartilage. As might be expected of cells in an avascular
tissue, chondrocytes exhibit low metabolic activity.
Cartilage also lacks lymphatic vessels and nerves.

28. The perichondrium
The perichondrium is a sheath of dense connective
tissue that surrounds cartilage in most places, forming
an interface between the cartilage and the tissues
supported by the cartilage. Th e perichondrium harbors
the cartilage’s vascular supply, as well as nerves and
lymphatic vessels. Articular cartilage, which covers the
surfaces of bones in movable joints, lacks
perichondrium and is sustained by the diff usion of
oxygen and nutrients from the synovial fluid.

29. HYALINE CARTILAGE
Hyaline (Gr. hyalos , glassy) cartilage, the most common
of the three forms.

31. Chondrocytes
Cells occupy relatively little of the hyaline cartilage mass.
At the periphery of the cartilage, young chondrocytes (or
chondroblasts) have an elliptic shape, with the long axis
parallel to the surface. Deeper in the cartilage, they are
round and may appear in groups of up to eight cells that
originate from mitotic divisions of a single chondrocyte
and are called isogenous aggregates. As the
chondrocytes become more active in secreting collagens
and other ECM components, the aggregated cells are
pushed apart and occupy separate lacunae.

33. ELASTIC CARTILAGE
=Elastic cartilage is essentially similar
to hyaline cartilage except that it
contains an abundant network
of elastic fibers in addition to
collagen type II.
-Elastic cartilage have a perichondrium
similar to that of most hyaline cartilage.

34. FIBROCARTILAGE
Fibrocartilage takes various forms but is essentially a
combination of hyaline cartilage and dense connective
tissue with gradual transitions betweeAn these tissues .
It is found in intervertebral discs, in attachments of
certain ligaments, and in the pubic symphysis.

35. There is no distinct surrounding perichondrium in
fibrocartilage. Intervertebral discs of the spinal column
are composed primarily of fibrocartilage and act as
lubricated cushions and shock absorbers preventing
adjacent vertebrae from being damaged by abrasive
forces or impacts.

36. CARTILAGE FORMATION, GROWTH, &
REPAIR
All cartilage forms from embryonic mesenchyme in the
process of chondrogenesis. Once initially formed, the
cartilage tissue enlarges both by interstitial growth,
resulting from the mitotic division of preexisting
chondroblasts, and by appositional growth, which
involves differentiation of new chondroblasts from the
perichondrium