Category: Biology Second Paper Lecture Sheet

Nose, ear, head of humerus and femur, joints, trachea, periosteum, epigøtis, intervertebral disc etc.

Cartilage is made up of semi-hard and elastic material called chondrin. Its matrix is composed of proteins called chondromucoid and chondralbunoid. Chondromucoid and chondralbuinoid together are called chondrin. It contains collagen, elastin, proteoglycan, chondrocytes etc. Cartilage cells are called chondrocytes. Clusters of chondrocytes are called lacunae. It is covered by perichondrium.

Cartilage is made up of semi-hard and elastic material called chondrin. Its matrix is composed of proteins called chondromucoid and chondralbunoid. Chondromucoid and chondralbuinoid together are called chondrin. It contains collagen, elastin, proteoglycan, chondrocytes etc. Cartilage cells are called chondrocytes. Clusters of chondrocytes are called lacunae. It is covered by perichondrium.

Where is the cartilage or orange bone: Nose, ear, head of humerus and femur, joints, trachea, periosteum, epigøtis, intervertebral disc etc.

Characteristics of cartilage or cartilage
1. Cartilage has no blood vessels or lymph.
2. It has no nerve conduction i.e. no sensation.
3. It takes longer for wounds to heal.
4. The perichondrium is covered by the mantle.
5. It contains chondroitin instead of calcium.
6. Calcium deposits in the cartilage cause the cells to die.
7. Cartilage gradually turns into bone.
8. Contains so much lubricin that acts as a lubricator.

Classification of cartilage
Cartilage is divided into 4 parts based on structure. These are-
1. Clear or Hyaline Cartilage: This cartilage matrix is transparent, firm, flexible, homogenous, bluish and elastic. It is covered by the perichondrium. It contains no fibers. It contains cavities called lacunae. Inside the lacunae are chondrocytes or chondroblasts. This cartilage is present in the nose, trachea, larynx, larynx, larynx of mammals, bones and embryos of vertebrates.
2. Biliary Cartilage: The matrix of this cartilage is opaque, elastic and light yellow in color. Yellow colored fibers are scattered in it. The fibers are branched and scattered. It is covered by the perichondrium. It contains cavities called lacunae. Inside the lacunae are chondrocytes or chondroblasts. It is present in external ear, pinna, tongue, eustachian tube, epiglottis, larynx, lymph nodes etc.
3. Whitish Cartilage: The matrix of this cartilage is opaque and colorless. It has white fibers. The fibers are unbranched and arranged parallel and in clusters. It is covered by the perichondrium. It contains cavities called lacunae. Inside the lacunae are chondrocytes or chondroblasts. It lies between the joints and vertebrae.
4. Calcified or calcareous cartilage: This cartilage matrix contains a large amount of calcium carbonate. Its matrix is rock solid. It resides in the head of the humerus and femur.

Function or importance of cartilage
1. Cartilage resists the tension and stress of various organs.
2. Gives shape to various organs.
3. Joints help join two or more bones together.
4. Protects bones from frictional injuries.
5. Helps tendons and ligaments attach to bones.
6. A glycoprotein called lubricin in cartilage acts as a lubricant.
7. Forms the embryonic skeleton of vertebrates and the endoskeleton of fishes such as chondrichthys.

The joint cavity containing oily and slippery fluid called synovial is called synovial joint. It is 7 types. namely-
(i) Pivot (atlas joint)
(ii) Hinge joint (elbow joint)
(iii) Ball and Cotoral Joints (Skandha/Femur Joints)
(iv) Flat joint (Carpal joint)
(v) Saddle (metacarpal joint)
(vi) Ellipsoid Joint (Carpal Joint)

Bone joints containing cartilage are called amphiarthrosis joints. It is of two types. namely-
(i) Symphysis (pubis symphysis)
(ii) Synchondrosis (joint of cartilage)

The joint where the bones are joined by fibrous connective tissue is called fibrous connective tissue. It is of three types. namely-
(i) Suchar (Treaty of Ten)
(ii) Syndesmosis (tibia-fibula joint)
(iii) Gomphosis (joint of teeth and jaws)

The junction of two or more bones or cartilages is called a joint. There are three types of joints.
1. Fibrous or Synarthrosis Joint: The joint where the bones are joined by fibrous connective tissue is called fibrous connective tissue. It is of three types. namely-
(i) Suchar (Treaty of Ten)
(ii) Syndesmosis (tibia-fibula joint)
(iii) Gomphosis (joint of teeth and jaws)
2. Cartilaginous/Amphiarthrosis/Cartilaginous Joints: Bone joints containing cartilage are called amphiarthrosis joints. It is of two types. namely-
(i) Symphysis (pubis symphysis)
(ii) Synchondrosis (joint of cartilage)
3. Synovial joint: The joint cavity containing oily and slippery fluid called synovial is called synovial joint. It is 7 types. namely-
(i) Pivot (atlas joint)
(ii) Hinge joint (elbow joint)
(iii) Ball and Cotoral Joints (Skandha/Femur Joints)
(iv) Flat joint (Carpal joint)
(v) Saddle (metacarpal joint)
(vi) Ellipsoid Joint (Carpal Joint)

1. Structure of the body: Bones form the structure of the body and give specific shape to the body.
2. Preservation: The soft parts of the bony body protect the heart, lungs, brain, spinal cord, etc.
3. Movement: Skeletal muscles control body movement through contraction and expansion.
4. Red blood cell production: Red blood cells are produced from the bone marrow.
5. Immunity: Stabilized reticuloendothelial system increases the body’s immune system.
6. Breathing and Hearing: Some parts of the spine change and help in breathing and hearing.
7. Mineral salt storage: Bone stores calcium, phosphorus, potassium etc. About 97% of the body’s calcium is stored in bones.
8. Accumulation of toxic elements: If there are toxic elements in the body like lead, arsenic, etc., the bones store them.
9. As a junction: Acts as a junction of muscles, ligaments and tendons.
10. Pressure and ionic balance: Maintains internal pressure and ionic balance of the body.
11. Hormonal action: Osteocalcin hormone is produced from the bone marrow. This hormone regulates blood sugar and fat levels.
12. Chemical energy storage: As we age, some red bone marrow turns into yellow bone marrow. Bile bone marrow contains adipose cells. Adipose cells store chemical energy.

Haversian canals, lamellae, lacunae and canaliculi are collectively called Haversian canals or osteons. The structure of pure bone or osteon is described below-
1. Haversian Duct: The duct located in the unstable center is called Haversian duct. It contains veins, arteries and lymphatics. The Haversian ducts are connected to each other by the ducts of Vochmans.
2. Lamellae: 5-15 layers surround the Haversian canal. Each layer is called lamellae. It contains calcium, phosphorus and collagen.
3. Lacuna: Each lamella has small cavities. Each cavity is called a lacuna. Each lacuna contains bone cells called osteocytes or osteoblasts or osteoclasts.
4. Canaliculi: Each lacuna is surrounded by several fine canals. These ducts are called canaliculi. Lacunae are connected to each other by canaliculi. It transports nutrients and waste materials.
5. Medullary cavity: The cavity in the unstable center is called the medullary cavity. It is filled with red or yellow pulp

The inelastic cells that have less calcium and more marrow and are soft like a sponge are called spongy bones. Its structural and functional unit is called trabeculae. It has numerous kuthuri or voids. They are like sponge or honeycomb called cancellous or trabecular bone. Each trabecula is composed of osteocytes, lamellae, lacunae and canaliculi. Blood vessels from the unstable periosteum enter the trabeculae and supply nutrients to the bone cells. Haversianism does not exist. Carotid bones of mammals, large bony extremities, flat bones and all bones of birds are spongy in nature. Almost all bones in children are spongy. 20% of the total weight of the human body is spongy bone.