Endoskeleton | bone and cartilage | class 12

Описание: Aslam o alikum
I am Hassam ur Rahman and I am teaching Fsc biology since 2014 .I am always trying to improve myself and provide best lecture to students.i am taking content for the lecture from authentic and relevant sources but human errors are possible . you are requested to please highlight the mistakes.My lectures are equally reliable for Fsc and mdcat students
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This lecture is about
3. Endoskeleton
The endoskeleton is primarily made up of two types of tissues, bones and cartilage. Both bones
and cartilage are types of rigid connective tissue. Both consists of living cells embedded in the
matrix of protein called collagen.
Bone : It is the most rigid form of connective tissue. The collagen fibers of bone are hardened by
deposit of calcium phosphate. Bones supporting your arms and legs consist of an outer shell of
compact bone, with spongy bone in the interior. Compact bone is dense and strong and provides
an attachment site for a muscle. Spongy bone is light, rich in blood vessels, and highly porous. The
cavities of spongy bone contain bone marrow where blood cells are formed. There are three types
of cells associated with bone:
Bone-forming cell (osteoblast ), mature bone cell (osteocyte ), and bone dissolving cells (osteoclast
).Early in development, when bone is replacing cartilage, the osteoclasts invade and dissolve the
cartilage. Then osteoblasts replace it with bone. As bones grow, the matrix of bone is hardened
and the osteoblasts are gradually entrapped within it.
Cartilage : It is much softer than bone. It is a form of connective tissue. It covers ends of the bone
at the joint, and also supports the flexible portion of nose and external ears. The living cells of
cartilage are called chondrocytes. These cells secrete flexible, elastic, non-living matrix collagen
that surrounds the chondrocytes. No blood vessels penetrate into this cartilage. There are three
main types of cartilage.
(i) Hyaline Cartilage : It is the most abundant type in human body. It is found at the movable
joints.
(ii) Elastic Cartilage: It has matrix containing bundles of collagens fibers. It forms external
pinnae of ears and the epiglottis.
(iii) FibroCartilage: