SKELETAL CONNECTIVE TISSUE

*it is hard connective tissue, due to presence of mineral like calcium & phosphorus in their matrix.
*it is further classified into two groups-

1. Cartilage

1. Bone

1. Cartilage
-study of cartilage is called chondrology.
-perichondrium- it is outer most covering and it gives shapes to cartilage. it is elastic in nature and made up of yellow fibre.
-matrix- it contains water as main component and chondriodin sulphate and also some mineral like calcium.
-lacunae- it is small open space and it contains cartilage-forming cells, chondrocytes. chondrocytes forms chondrin protine and chondrin protine combines with water,chondriotic-sulphate and mineral to make cartilage. this process is called chondrogeesis. cartilage contains white fibre for mechanical support.
-chondroplast cell- it is cartilage digesting cell, develops in old age and it is multi-nucleated.

*cartilage is called avascular connective tissue, because it does not contain distribution of blood vessel.
*the growth of cartilage is unidirectional,i.e. always towards peripheri.

Classification of cartilage on the basis of their properties-

• Hyline cartilage(transparent like glass)- it is most primitive and most abundant found in animal body. it contains small white fiber in matrix.. it is found in endings of long bones, in larynx, in ending of ribs, in hyoid etc
• Elastic cartilage- it is elastic in nature, their matrix contain long elastic fibres. it is found in nose- tip, ear pinna,vertebrae of shark
• Fibrous cartilage- it is the strongest cartilage,it contain long white fibrous matrix. it is found in inter-vertebral disc, in pectorial girdle
• Calcified cartilage- it is the hardest cartilage, because calcium is present in there matrix. it is found in pubis and pelvis girdle.

2.Bone

-study of bone is called osteology

-periostium-it is outer most covering of bone, it is made up of white connective fibre. it is tough, rigid and inelastic in nature. it gives shape to bone.

-osteoblast cell-it is bone forming cell, present just inside the periostium and also found in bone marrow

-osteocyte- it is also bone forming cell, present inside lacunae, it is formed by osteoblast. both osteoblast and osteocyte forms ossein protein.

-matrix- matrix of bone contain maximum amount of water, calcium phosphate and calcium hexose metaphosphate enzyme.

-lamellae- it is circular plate of bone matrix.

*Haversian canal-it is found in long bones of mammals.it contain longitudinal canal(Hervasian camal) and transverse canal(Volkman's canal) and the branched process is canal culi.

*process of formation of bone is called osteogenesis.

*Calcification-deposition of calcium on bone is called calcification.

*Decalcification-desolution of calcium from bone is called decalcification.

*Bone marrow- it is the central cavity of bone, which is filled with two types of cells-yellow bone marrow and red bone marrow.

-white bone marrow stores fat and red bone marrow helps in formation of blood.

-in children bone is completely filled with red bone marrow

Types of bone on the basis of formation-

• Cartilaginous/ replacing/endochondral bone-these bones are formed from deposition of calcium on cartilage.it is found in every limbs, bones of girdle, roof of the cranial vertebrae etc.
• Membranous/ dermal/investing bone- these bones are formed by deposition of calcium on mesenchyme. it is found in jaw bone, pectorial girdle, bone of floor of cranial etc
• Sesamoid bone- these bones are formed by the deposition of calcium on tendon. e.g.- patella.