Bones and Joints form the skeletal system of body.There are about 206 bones in human body. Main functions of skeletal system are -
1. Giving support and protection to soft tissues and vital organs.
2. Giving attachment to muscles and assisting in body movements.
3. Formation of blood cells in the red bone marrow.
4. Storage of mineral salts like calcium and phosphorous.
Composition of Bone
Bone is structurally a complex organ and has the following composition.
water - 25%
Ossein,Osseomucoid and Osseo Albumin (organic solids) - 35%
inorganic salts of calcium - 45%
Calcium salts impart hardness to bones.
Structure of bone tissue: Refer to Cell and Tissues.
Functions of bone marrow :
Bone marrow performs functions of -
1) Formation of blood cells(Haemopoeisis)
2) Destruction of old RBC with the help of reticulo endothelial
cells(haemolysis)
3) Protection of body against infections by microbes with the help of reticuloendothelial cells against foreign particles(Defence mechanism)
4) Against foreign particles(Defence mechanism
Ossification
Ossification is the process of bone formation. Development of bones takes place from spindle shaped cells called osteoblasts.
There are two types of ossification.
They are-
1) Intra membranous ossification.
2) Intra cartilaginous ossification.
1. Intra membranous ossification : Type of ossification in which, dense connective tissue is replaced by deposits of calcium, forming bone is called as intramembranous ossification.
Ex: Bones of skull are formed by this process.
2. Intra cartilaginous ossification : Type of ossification in which,
cartilages are replaced by bone is called as intracartilaginous ossification. Most of the bones of the body are formed by this process
Types of Bones
Bones are mainly three types. They are - 1) Long bones. 2)Short bones 3) Flat bones 4) Irregular bones 5) Seasmoid bones.
1. Long bones: Long bones are found in limbs. A long bone has two ends. Ends of a long bone are called as epiphyses. These two ends are connected by shaft, which is called as diaphysis. Periosteum is the outer membrane covering the bone. Periosteum is followed by layer of compact bone. Central medullary canal is inside this.
Through nutrient foramen, arteries enter. Medullary canal contains yellow bone marrow. Extremities consist of mass of spongy bone, which contains red bone marrow. Yellow bone marrow contains fat and blood cells but is not rich in blood supply or red blood cells. Long bones develop from three centres called
centres of ossification. Centre of ossification present in shaft is called diaphysis and centres of ossification present at the ends of the bones are called epiphyses. Line of cartilage between epiphysis and diaphysis is called epiphyseal cartilage or epiphyseal plate.Epiphyseal plate separates epiphysis and diaphysis approximately upto 25 years of age.After this age,fusion of diaphysis and epiphysis takes place.After fusion,growth in length of bone becomes impossible.Acromegaly is growth of bone occurings after fusion of diaphysis and epiphysis by the overactivity of growth hormone.It will be confined mostly to the bones of face and limbs.This growth will be abnormal. Gigantism is growth occuring in immature bones before fusion of diaphysis with epiphysis due to excessive secreion of growth hormone.
2. Short bones : Short bones do not have shaft. They contain spongy substance covered by shell of compact bone.ex: small bones of wrist and ankle.
3. Flat bones : They contain two layers of compact bone with spongy substance between the two layers. They are found in pelvis and scapula.
4. Irregular bones : Bones which do not fall into any category are irregular bones. ex: vertebrae and bones of face.
5. Seasmoid bones : They are small bones and develop in tendons of muscles. ex: Patella of knee joint
1. Giving support and protection to soft tissues and vital organs.
2. Giving attachment to muscles and assisting in body movements.
3. Formation of blood cells in the red bone marrow.
4. Storage of mineral salts like calcium and phosphorous.
Composition of Bone
Bone is structurally a complex organ and has the following composition.
water - 25%
Ossein,Osseomucoid and Osseo Albumin (organic solids) - 35%
inorganic salts of calcium - 45%
Calcium salts impart hardness to bones.
Structure of bone tissue: Refer to Cell and Tissues.
Functions of bone marrow :
Bone marrow performs functions of -
1) Formation of blood cells(Haemopoeisis)
2) Destruction of old RBC with the help of reticulo endothelial
cells(haemolysis)
3) Protection of body against infections by microbes with the help of reticuloendothelial cells against foreign particles(Defence mechanism)
4) Against foreign particles(Defence mechanism
Ossification
Ossification is the process of bone formation. Development of bones takes place from spindle shaped cells called osteoblasts.
There are two types of ossification.
They are-
1) Intra membranous ossification.
2) Intra cartilaginous ossification.
1. Intra membranous ossification : Type of ossification in which, dense connective tissue is replaced by deposits of calcium, forming bone is called as intramembranous ossification.
Ex: Bones of skull are formed by this process.
2. Intra cartilaginous ossification : Type of ossification in which,
cartilages are replaced by bone is called as intracartilaginous ossification. Most of the bones of the body are formed by this process
Types of Bones
Bones are mainly three types. They are - 1) Long bones. 2)Short bones 3) Flat bones 4) Irregular bones 5) Seasmoid bones.
1. Long bones: Long bones are found in limbs. A long bone has two ends. Ends of a long bone are called as epiphyses. These two ends are connected by shaft, which is called as diaphysis. Periosteum is the outer membrane covering the bone. Periosteum is followed by layer of compact bone. Central medullary canal is inside this.
Through nutrient foramen, arteries enter. Medullary canal contains yellow bone marrow. Extremities consist of mass of spongy bone, which contains red bone marrow. Yellow bone marrow contains fat and blood cells but is not rich in blood supply or red blood cells. Long bones develop from three centres called
centres of ossification. Centre of ossification present in shaft is called diaphysis and centres of ossification present at the ends of the bones are called epiphyses. Line of cartilage between epiphysis and diaphysis is called epiphyseal cartilage or epiphyseal plate.Epiphyseal plate separates epiphysis and diaphysis approximately upto 25 years of age.After this age,fusion of diaphysis and epiphysis takes place.After fusion,growth in length of bone becomes impossible.Acromegaly is growth of bone occurings after fusion of diaphysis and epiphysis by the overactivity of growth hormone.It will be confined mostly to the bones of face and limbs.This growth will be abnormal. Gigantism is growth occuring in immature bones before fusion of diaphysis with epiphysis due to excessive secreion of growth hormone.
2. Short bones : Short bones do not have shaft. They contain spongy substance covered by shell of compact bone.ex: small bones of wrist and ankle.
3. Flat bones : They contain two layers of compact bone with spongy substance between the two layers. They are found in pelvis and scapula.
4. Irregular bones : Bones which do not fall into any category are irregular bones. ex: vertebrae and bones of face.
5. Seasmoid bones : They are small bones and develop in tendons of muscles. ex: Patella of knee joint
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