This is a note on connective tissue

1. SPECIALIZED CONNECTIVE TISSUE:
SUPPORTING TISSUE. (CARTILAGE &
BONE)
DR. RILWANU BELLO
DEPARTMENT OF ANATOMY
FBMS, CHS, UDUS.

2. • The term connective tissue is applied to a tissue that
fills the interstices between more specialized
elements and serves to hold them together and
support them
• For the latter reason some authorities prefer to call
it support tissue
• Basic component of connective tissue; fibres, cells,
and intercellular substance (ground substance)

3. Connective Tissue Cells
Macrophage
Plasma Cell
Lymphocyte

4. CONNECTIVE TISSUE FIBERS
Collagenous Fibers
(bundles)
Reticular Fibers
(networks)
Elastic Fibers
(anastomosing bundles)

5. TYPES OF CONNECTIVE TISSUE
• Different concentration and density of the cells,
fibres and extracellular macromolecles produce
graded variation in histological structure within
connective tissue
• Descriptive names or classifications used for the
various type of connective tissue denote either a
major component or a structural characteristic of
the tissue

6. • (A) CONNECTIVE TISSUE PROPER:
I - loose (areolar) connective tissue
ii – Dense irregular connective tissue
Iii – Dense regular connective tissue
• (B) EMBRYONIC CONNECTIVE TISSUE:
i – Mesenchyme (mesodermal layer of the early
embryo)
ii – Mucoid (mucus) connective tissue (matrix of the
fetal umblical cord)

7. • SPECIALIZED CONNECTIVE TISSUE:
i – Reticular connective tissue
Ii – Adipose tissue
Iii – Cartilage
Iv – Bone
V - Blood

8. CARTILAGE
• Is a tough, flexible form of connective tissue
characterized by extracellular matrix; variation in the
composition of these matrix components and cells
produce three types of cartilage adapted to local
biomechanical needs
• Cartilage consist of cells called chondrocytes
embedded in an extensive ECM
• Chondrocytes synthesize and maintain ECM
components and are located in matrix cavities called
lacunae

9. Functional unit of the cartilage: chondron

10. • Collagen, hyaluronic acid proteoglycans and various
glycoproteins are the principal macromolecles
present in all types of cartilage matrix.
• In all three forms, cartilage is avascular and receives
nutrients by diffusion from capillaries of adjacent
connective tissue (perichondrium)

11. Functions
• Supports regions of the body which require varying
degree of flexibility
• Provides gliding area for the joint, facilitating
movements (in Hyaline Cartilage)
• Essential for the growth of long bones (In Hyaline
Cartilage)

12. PERICHONDRIUM
• Is a sheath of dense connective tissue that surrounds
cartilage in most places, forming an interface
between the cartilage and the tissue supported by
the cartilage.
• The perichondrium harbours the cartilge vascular
supply as well as nerves and lymphatic vessels
• Articular cartilge which covers the surface of bone
in movable joints lacks perichondrium and is
sustained by the diffusion of oxygen and nutrients
from the synovial fluid.

13. • Perichondrium has 2 layers:
Outer – Fibrous,
Inner- Cellular - chondrogenic cells, undifferentiated
flat cells, proliferating and differentiating into
chondroblasts

14. perichondrium
chondroblasts

15. HYALINE CARTILAGE
• Hyaline (Gr. Hyos; glassy) cartilage; the most
common of the three forms, is homogeneus and
semitransparent in the fresh state (blue-white
translucent appearance)

16. • DISTRIBUTION OF HYALINE CARTILAGE
• In adults hyaline cartilage is located;
• In the epiphyseal plate of long bones; where it
makes possible longitudinal bone growth
• Costal cartilage; that connects ventral end of the rib
to the sternum
• Articular cartilage; (articular surfaces of most
synovial joints). These articular cartilages provide the
bone ends with smooth surfaces from which there is
little friction.

17. Hyaline Cartilage

19.  Articular cartilage
 Covers the external surface of
the epiphyses
 Made of hyaline cartilage
 Decreases friction at joint
surfaces
Figure 5.2a

20. • The skeletal framework of the larynx is formed by
numerous cartilages, of these, the thyroid cartilage,
the cricoid cartilage and the arytenoid cartilage are
composed of hyaline cartilage.
• Part of the nasal septum and the lateral wall of the
nose are made up of pieces of hyaline cartilage
• In embryo, hyaline cartilage forms the temporary
skeleton that is gradually replaced by bone

21. CARTILAGE: LOCATIONS

22. • MATRIX:
• The dry weight of hyaline cartilage is 40% collagen
embedded in a firm hydrated gel of proteoglycans
and structural glycoproteins
• In routine histology preparations, the proteoglycans
cause the matrix to be generally basophilic and the
thin collagen fibrils are barely discernible
• Most of the collagen in hyaline cartilage is type II
collagen, although small amount of several minor
types are also present.

23. Hyaline Cartilage

24. • Hyalos=glass like
• Transparent, homogeneous
• H/E: Bluish, basophilic matrix
• Chondrocytes: large & in isogenous groups
• Territorial matrix
• Interstitial matrix
• Rich in Type II Collagen fibres

25. • CHONDROCYTES:
• Cells occupy relatively little of the hyaline cartilage
mass
• At the periphery of the cartilage, young
chondrocytes (or chondroblast) have an eliptic
shape with the long axis parallel to the surface
• Deeper in the cartilage, they are round and may
appear in group of up to eight cells that originate
from mitotic division of a single chondrocyte and are
called isogenous aggregates

26. Hyaline Cartilage

27. • Chondroblasts: short, small, elongated cells, rich in all cell organellae,
usually occuring singly, covered by asac like structure known as Lacunae
• Chondrocytes: matured cells , large, less cell organellae, in isogenous
groups, seen away from the perichondrium

28. • Cartilage cells and the matrix often shrinks during
routine histological preparation, resulting in both the
irregular shape of the chondrocytes and their
retraction from the matrix
• In living tissue and in freshly prepared sections the
chondrocytes fills the lacunae completely

29. • PERICHONDRIUM:
• Except at the articular cartilage of joints, all hyaline
cartilage is covered by a layer of dense connective
tissue, the perichondrium which is essential for the
growth and maintenance of of cartilage
• It consist largely of collagen type- I fibres and
fibroblasts
• Among these fibroblast, in the inner layer of
perichondrium are progenitor cells for chondroblast
that divide and differentiate into chondrocytes

30. Hyaline Cartilage

31. • Hyaline cartilage has been compared to a TYRE!
• Ground Substance = Corresponds to the RUBBER of
the tyre resisting Compressive forces
• Fibres = corrresponds to the treads of the tyre
resisting tensional forces

32. ELASTIC CARTILAGE
• Elastic cartilage is essentially similar to hyaline
cartilage except that it contains an abundant
network of elastic fibres in addition to collagen type
II which give it a yellowish colour
• H/E: elastic fibres difficult to see.
• Clearly visualized on special staining such as orcein
or resorcin fuchsin
• Elastic fibers stain BLACK with Weigert stain

34. Branching Elastic fibres give FLEXIBILITY &
SUPPORT

36. LOCATIONS OF ELASTIC CARTILAGE
• 1. It form the skeletal basis of the auricle and of the
lateral part of the external acustic meatus
• 2. The wall of the medial part of the auditory
(eustachian) tube is made of elastic cartilage
• 3. The epiglottis and two small laryngeal cartilages
(corniculate and cuneiform) consists of elastic
cartilage.
• Elastic cartilage in these locations includes a
perichondrium similar to that of most hyaline
cartilage

37. CARTILAGE: LOCATIONS

38. FIBROCARTILAGE
• Is essentially a combination of hyaline cartilage and
dense connective tissue with gradual transition
between these tissues
• Numerous dense collagen bundles oriented in the
direction of functional stress with some fibroblasts
• Chondrocytes of fibrocartilage occur singly and in
aligned isogenous aggregation and produce matrix
containing type II collagen fibres
• In some fibrocartilage, the matrix around the
chondrocyte is very sparse

39. Fibrocatilage

40. • Regions with chondrocytes and hyaline matrix are
separated with other regions containing bundles of
type I collagen and scattered fibroblast
• The relative scarcity of proteoglycans makes the
matrix of fibrocartilage more acidophilic than that
of hyaline or elastic cartilage
• There is no distinct surrounding perichondrium in
fibrocartilage

41. LOCATIONS OF FIBROCARTILAGE
• Intervertebral discs: each intervertebral disc has two
main components, the peripheral anulus fibrosus rich in
bundles of type I collagen and the central nucleus
pulposus with a gel like matrix rich in hyaluronic acid
• In the pubic symphysis
• Manubriosternal joints
• Deep groves of bone, where tendons run
• Articular discs in temporo-mandibular joints ,Sterno-
clavicular joints & Menisci of Knee joints
• Glenoidal labrum & Acetabular labrum

42. CARTILAGE: LOCATIONS

43. MEDICAL APPLICATION
• OSTEOARTHRITIS: A chronic condition that
commonly occur during aging, involves the gradual
loss or changed physical properties of hyaline
cartilage that lines the articular ends of bones in
joints.
• Joints that are weight bearing (knees, hip) or heavily
used (wrist, fingers) are most prone to cartilage
degeneration
• Cells of cartilage can give rise to either benign
(chondroma) or slow-growing, malignant
(chondrosarcoma) tumors

44. Histology of Bone

45. • As the main constituent of the adult skeleton, bone
tissue provides solid support for the body, protect
vital organs such as those in cranial and thoracic
cavities and harbours cavities containing bone
marrow, where blood cells are formed.
• Bone is a specialized connective tissue composed of
calcified extracellular matrix; the bone matrix and
three major cell types

46. Figure 3.19a Connective tissues and their common body locations.
Bone cells
in lacunae
Central
canal
Lacunae
Lamella
(a) Diagram: Bone Photomicrograph: Cross-sectional
view of ground bone (165×)

47. • Osteocytes (Gr. Osteon, bone + Kryos, cells): which
are found in cavities (lacunae) between bone matrix
layers (lamellae) with cytoplasmic processes
extending into small canaliculi between lamellae
• Osteoblast (osteon + Gr. Blaston, germ): which
synthesize the organic component of the matrix
• Osteoclasts (osteon + Gr. Klastos, broken): which are
multinucleated giant cells involved in the resorption
and remodelling of bone tissue

48. • All bones are lined on both internal and external
surfaces by layers of connective tissue containing
osteogenic cells – endosteum on the internal surface
surrounding the marrow cavity and periosteum on
the external surface
• Rigidity and hardness is provided by the matrix
which is impregnated with inorganic salts

49. OSTEOBLASTS
• Synthesize and secretes the organic component of
the bone matrix, which includes type 1 collagen
fibres, proteoglycans and several glycoproteins such
as osteonectin
• Mature osteoblasts are located exclusively at the
surface of the bone matrix, usually side by side in a
layer somewhat resembling a simple epithelium
• When actively engaged in matrix synthesis,
osteoblast have a cuboidal to columnar shape and
basophilic cytoplasm

50. The blue arrows indicate the osteoblasts.
The yellow arrows indicate the bone matrix
they’ve just secreted.

52. • When their synthesizing activity declines they
flattened and basophilia is reduced; inactive
osteoblast represent most of the flattened bone
lining cells in both the endosteum and periosteum

53. OSTEOCYTES
• Many osteoblast are gradually surrounded by the
material they secreted and differentiate further as
osteocytes enclosed simply within the lacunae that
are regularly spread throughout the mineralized
matrix
• In transition from osteoblast to osteocytes, the cells
extends many long dendritic processes which also
become surrounded by calcifying matrix
• Osteocytic processes, thus come to occupy the
many canaliculi

54. Osteocytes with Canaliculi

55. • When compared with osteoblast, the flat – almond-
shaped osteocytes exhibit significantly less RER,
smaller golgi complexes and more condensed
nuclear chromatin.
• These cells maintained the bony matrix and their
death is followed by rapid matrix resorption.

57. Osteocytes

58. OSTEOCLASTS
• These are very large motile cells with multiple
nuclei and play a major role in matrix resorption
(active erosion of bone minerals) during bone growth
and remodeling
• Contain large numbers of mitochondria and
lysosomes
• In areas of bone undergoing resorption, osteoclast lie
within enzymatically etched depresions or cavities in
the matrix known as resorption cavities (also called
Howship lacunae)

59. Osteoclasts

60. Remodeling Bone

61. • In active osteoclasts, the surface against the bone
matrix is folded into irregular projections, forming a
ruffled border surrounded by a cytoplasmic zone rich
in actin filaments which is the site of adhesion to the
matrix.
• This circumfrential adhesion zone create a
microenvironment between the osteoclast and the
matrix in which bone resorption occurs

62. Bone Resorption

66. MEDICAL APPLICATION
• In the genetic disease osteopectrosis which is
characterized by dense heavy bones (marble bones)
the osteoclasts lack ruffled borders and bone
resorption is defective
• This disorder result in overweight and thickening of
bones often with obliteration of the marrow
cavities and the loss of white blood cells

67. BONE MATRIX
• Inorganic materials represent about 50% of the dry
weight of the bone matrix
• The organic matter embedded in the calcified
matrix include type - 1 collagen, proteoglycan
aggregates and bone-specific multiadhesive
glycoproteins such as osteonectin
• Calcium-binding proteins; notably osteocalcin and
the phosphatases released in matrix vesicles by
osteoblast promote calcification of the matrix.

68. Remodeling Bone

69. PERIOSTEUM AND ENDOSTEUM
• The periosteum is organized much like
perichondrium. The outer layer is dense connective
tissue with small blood vessels, collagen bundles and
fibroblasts
• Bundles of periosteal collagen fibres called
perforating (or Sharpey) fibres penetrate the bone
matrix binding the periosteum to bone

70. Periosteum
Mesenchyme
Fibroblasts
Osteoprogenitor
cells

71. • The inner layer of periosteum is a more cellular
layer containing bone lining cells osteoblasts and
mesenchymal stem cells called osteoprogenitor cells.
with the potential to proliferate and differentiate into
osteoblasts
• The principal functions of periosteum are to nourish
the osseous tissue and provide continuous supply of
new osteoblast for appositional bone growth or
repairs

72. ENDOSTEUM
• Internally, the very thin endosteum covers small
trabeculae of bony matrix that project into the
marrow cavities.
• Although considerably thinner than the periosteum,
endosteum also contains osteoprogenitor cells,
osteoblasts and bone lining cells

73. MEDICAL APPLICATION
• Osteoporosis: is an imbalance in skeletal turnover so
that bone resorption exceeds bone formation
• This lead to calcium loss from bone and reduced
bone mineral density.

74. TYPES OF BONE
• Microscopic examination of bone tissue shows two
type of organization; lamella and woven bone,
which is usually more immature than lamella bone.

75. LAMELLA BONE
• Most bone in adult compact or cancellous is
organized as lamella bone characterized by multiple
layers of lamellae of calcified matrix each 3 – 7
micrometre thick
• The lacunae are organized either parallel to each
other or concentrically around a central canal

77. • Compact bone;
• Is hard and dense and resemble ivory.
• It occurs on the surface cortex of bones being
thicker in the shaft of long bones and in the surface
plates of flat bones
• The collagen fibres in the miniralized matrix are
arranged in layers, embedded in which are
osteocytes

78. Compact Bone

80. • Most of these lamellae are arranged in concentric
cylinders around vascular channels (Haversian cana )
forming haversian system or osteon which usually lie
parallel to each other and to the long axis of the
bone.
• Haversian system (or osteon) is a structural and
functional unit of the compact bone

81. Histology of Compact Bone

82. OSTEON
• An osteon ( or Haversian system) refers to complex
of concentric lamellae (4 – 10) surrounding a small
central canal that contain blood vessels, nerves loose
connective tissue and endosteum
• Between successive lamellae are lacunae each with
one osteocyte interconnected by canaliculi
containing the cells dendritic processes
• The outer boundary of each osteon is a more
collagen rich layer called the cement line

83. • Each osteon is a long, sometimes bifurcated cylinder
generally parallel to the long axis of diaphysis
• The central canal communicate with the marror
cavity and the periosteum and with one another
through transvers perforating canal (or Volkman’s
canal).
• The transverse canal have few, if any concentric
lamellae

84. Histology of Compact Bone

87. • Cancellous (or spongy) bone;
• Consist of spongywork of trabeculae arranged not
haphazardly but in a very real pattern best adapted
to resist the local strain and stress
• If for any reason there is alteration in the strain to
which cancellous bone is subjected, there is
rearrangement of trabeculae
• Cancellous bones are found in the interior of bones
and at the articular ends of the long bones

89. • Slender bony trabeculae that branch and anastomose with
one another.
• Enclose irregular marrow spaces containing blood vessels
and haemopoietic tissue that give rise to new blood vessels.
• They receive nutrition from blood vessels in the bone
marrow

93. • Blood vessels do not usually lie within this bony
tissue and osteocytes depend on diffussion from
adjascent medullary vessels
• Medullary cavity of the long bone and interstices of
cancellous bone are filled with red or yellow marrow
• At birth all the marrow of all the bones is red, active
haemopoises going on everywhere.

94. • As age advances, the red marrow atrophies and is
replaced by yellow fatty material with no power of
haemophoises. This changes begin in the distal part
of the limbs and gradually progresses proximally.
• By young adult life, red marrow remain only in the
ribs, sternum, vertebrae, skull bones and proximal
ends of the femur and humerus, these are the sites
of deposition of malignant metastases

95. WOVEN BONE
• Is nonlamella and characterized by random
disposition of type 1 collagen fibres and is the 1st
bone tissue to appear in embryonic development
and in fracture repair
• Woven bone tissue is usually temporary and is
replaced in adults by lamella bone except in a very
few places in the body, for example near the
sutures of the calvaria and in the insertions of some
tendons.

96. • In addition to irregular, interwoven array of collagen
fibres, this type of bone has a lower mineral content
(it is more easily penetrated by x- rays) and often a
higher proportion of osteocytes than mature lamella
bone.
• These features reflect the fact that woven bone
forms more quickly but has less strength than lamella
bone.