Histology
Lab -6-
Shorooq Wessam
Cartilage and Bone
Cartilage : is aspecial of connective tissue . It exhibits tensile strength
form ,provides firm structural support for soft tissues , allows flexibility
without distortion ,and is resilient to compression.Three main types of
cartilage are found in the body :Hyaline ,elastic and fibrocaytilage .
cartilae is classified based on the amount and types of fibers that are
present in the extracellular matrix.
Hyaline cartilage
is the most common type .In embryos ,hyaline cartilage serves as
askeletal model for most bones .As the individual grows,the cartilage
bone model is gradually replaced with bone through a process called
endochondral ossification.
Elastic cartilage
Is similar in appearance to hyaline cartilage . except for the presence
of numerous branching elastic fibers in its matrix.Elastic cartilage ,is
highly flexible and is found in the external ear epiglottis and larynx.
Fibrocartilage
Is characterized by large amount of irregular and dense bundles
of collagen layers of cartilaye matrix and thichk ,dense layers of
collagen fibers . fibrocartilage is found in the intervertebral
disks,symphysis pubis.
1
Bone:Similar to cartilage,bone is also aspecial form of connective tissue and
consists of cells,fibers a and extracellular matrix . Because of mineral
deposition in the matrix, bones become calcified.As aresult, they can
bear more weight than cartilage, serve as arigid skeleton for the body
and provid attachment sites for muscle and organs . bones also protect
the brain in the skull , the heart and lungs in the thorax and the urinary
and reproductive organs between the pelvic bones .
Types of Bone
Examination of bone in cross section shows two types : compact bone and
cancellous ( spongy bone ) . In long bones , the outer , cylindrical part is
the dense compact bone . the inner surface of compact bone adjacent to
the marrow cavity is the cancellous bone . In new bernes , the marrow
cavity is red and produces blood cells .In adults , the marrow cavity
normally is yellow and filled with adipose ( fat ) cells. In compact bone ,
the collagen fibers are arranged in thin layers of bone called lamellae
that are parallel to each other in the periphery of the bone or are
concentrically arranged around ablood vessel . In along bone , the outer
ciIn along bone , the outer circumferntial lamellae are deep to the
periosteum . the inner circumferential lamellae surround the bone
marrow cavity . concentric lamellae that surround acanal with blood
vessels , nerves and loose connective tissue are called osteon ( Haversian
systems ) . the space in the osteon that contains blood vessels and
nerves is the central ( Haversian ) canal . most of the compact bone
consists of osteons . Lacunae that have osteocytes and are connected via
canaliculi are found between the lamellae in each osteon .
2