What is Bone?

A bone is a connective tissue in which living cells, tissues and other components are contained within hard, non-living intercellular material.

Calcium phosphate and collagen are the two most important components of bone. These constituents distinguish it from similar structures such as enamel and chitin. Together, bone tissues make up the human and other vertebrates’ skeleton systems. These structures come in many sizes and shapes, each with a different level of complexity that is suitable for different purposes. The hard bone tissue forms a honeycomb-like structure internally made up of osteoblasts (or osteoclasts) and osteoclasts (or osteoblasts). Osteoblasts make new cells that protect and line the bone’s outer surface, while osteoclasts extract minerals from the cells.

Bones are composed of mineralized tissues that include other tissues such as bone marrow and periosteum. Two types of tissues are made up of bones: cortical and cancellous. The cortex of all bones is covered by cortical bone, which is more dense and rigid. It is responsible for approximately 80% of the total bone mass. It is also responsible for the inner tissue of bones. The cancellous bone forms this internal tissue and is more spongy than dense. Because it is flexible, the cancellous bone is often found at the ends long bones.

Cancellous bone has a higher blood flow and can often contain bone marrow or hematopoietic cells, which form different types of blood cells. There are five types of bones in the human body: long bones, short bone, sesamoid bone, flat bones and irregular bones. While long bones can be found on the limbs, short bones can be found on the wrists or ankles. The skull is made up of flat bones, while the sesamoid bone forms the majority of the joints. The bones give shape and structure to the whole body. They work in conjunction with muscles to aid movement. Bone marrow also hosts blood cell formation.

Examples of Bones

Humerus

The longest and most important bone in the upper limb is the humerus. It consists of a distal and proximal ends that connect to the elbow and the shoulder. The humerus’ head joins the glenoid cavity or shoulder plate at the proximal part. The trochlea connects at the distal tip with the distal ends of radius and the ulna. Humerus has an outer cortical bone, which is rigid and dense, just like other long bones. The peritoneum, which is the outer bone, is covered by connective tissue.

The cancellous bone, which is more flexible and spongy than the cortical bones, is found within the cortical bones. This cavity contains bone marrow, which is important in hemopoiesis. Adults have yellow bone marrow, while children have red. Because many muscles are connected to the humerus bone, it is vital for muscle movement.

Skull

The skull, which is the most important part of all vertebrates’ skeletons, provides protection for the brain and other sense organs. It is composed of two parts: the cranium, and the facial bones. The cranium is the covering of the brain and various nerves. While the facial bones provide facial structure and protection to the sense organs, the cranium protects the brain. The skull’s bones are linked by fibrous joints, which are immovable and fused in adulthood. Most of the bones in the skull consist of flat bones, which are similar in structure to long bones. Adult red blood cells are formed in flat cells, with the majority of them being made by adults.

What is Cartilage?

Cartilage, a fibrous, strong tissue, is flexible and elastic. It forms rubber-like padding on the ends of long bones, which aids in bone movement.

Cartilages, which are part of connective tissue, also form a structural component of many organs such as the nose and ear. Because they contain more collagenous tissue, cartilages are less rigid and dense than bones. Extracellular matrix is made up of collagen fibers and elastins. Chondrocytes are the specialized cells found in cartilage. They divide to create new cells.

The lack of blood vessels and nervous supply in the cartilages means that chondrocytes receive nutrition and oxygen via diffusion. Chondrocytes grow and divide at a slow pace, which is why they do not increase in size or weight. Based on the number and composition of the cartilage components, there are three types of cartilage: fibrocartilage (hyaline cartilage), elastic cartilage (fibrocartilage) and hyaline. The translucent and shiny hyaline cartilages can be found mostly in the ribs, joints and nose larynx.

Fibrocartilages can be found mostly in joints, and they have more collagen than other cartilages. They are found in the intervertebral disks, the pubic synphysis, as well as other joints. Elastic cartilage has more elastin protein and is flexible than other cartilages. It is found in the pinna, the inner ear. A glycoprotein called lubricin is found in cartilages. It helps with bio-lubrication, and protects it from wear and tear.

Because cartilages have very limited repair capabilities, it is difficult to repair them. Because the chondrocytes live in lacunae, they cannot travel to the affected areas. It takes longer for cartilage damage to heal. Cartilage serves a primary purpose. It provides a smooth surface for other tissues to glide and move easily. They also serve as a place for attachment to muscles.

Examples of Cartilage

Auricular cartilage of the ear

The cartilage in the ears is the auricular cartilage, which forms the outer part of the ears (outer). It gives the ear shape and allows for movement. Elastin protein is higher in Auricular cartilage, which is an example of elastic cartilage. This cartilage, like all cartilages is not supplied with any blood supply or nerve supply. This cartilage is permanent and will not change throughout your life. It also supports the development of your ear bones. For fashion reasons, many people pierce the cartilage of the ear. There are safer ways to puncture the ear but some piecing can lead to infection. Infections of the cartilage can cause tissue damage or perichondritis.

Costal cartilage

The hyaline cartilages in the ribs, the Costal cartilages, serve to lengthen the rib bones forward and allow for the elasticity of ribcage. These cartilages are located at the medial end of the ribs and are not present towards the anterior. These cartilages become longer as the length of bones in the ribcage decreases. These cartilages contain more elastin protein than any other cartilages in the body, making them more flexible and elastic.

Difference Between Bone and Cartilage – Bone vs Cartilage

Basis for Comparison	Bones	Cartilages
Definition	A bone is a connective tissue in which living cells, tissues and other components are contained within hard, non-living intercellular material.	Cartilage, a fibrous, strong tissue, is flexible and elastic. It forms rubber-like padding on the ends of long bones, which aids in bone movement.
Nature	Bones can be rigid, flexible, or strong.	Cartilages can be flexible, soft, or elastic.
Types	There are five types:a) Long bonesb) Flat bonesc) Short bonesd) Irregular bonese) Sesamoid bones	There are three types:a) Fibrocartilageb) Elastic cartilagec) Hyaline cartilage
Blood supply	Calcium salts are deposited in bone to provide a rich supply of blood.	Except for some cartilage that has no calcium salts deposition, there is little blood supply to the cartilage.
Directions of growth	Bidirectional bone growth is i.e. It grows in both directions.	Cartilage growth is unidirectional. It grows only on one side.
Bone marrow	There is bone marrow. All blood cells are made from bone marrow.	It is missing bone marrow.
Canals	Both the Volkmann canal and the Haversian canal system are represented in bones.	Cartilage is missing the Volkmann canal and the Haversian canal system.
Cells	Osteocytes are the name given to bone cells.	Chondrocytes are the name given to cartilage cells.
Rigidity	Calcium carbonates and phosphates in the matrix cause bone hardening.	Except for calcified cartilage, cartilage is soft.
Composition	The matrix that forms bones is made up of a protein called Ostein. It can be either organic or inorganic.	The matrix that forms cartilage is made up of a protein called Chondrin. It is organic.
Matrix	Matrix is found in bones and is located in the lamellae.	The matrix in cartilages is described as a homogeneous mass that lacks lamellae.
Lacunae	Canaliculi are present in bones’ lacunae, where each one of the cells is only one.	Canaliculi are not present in cartilage lacunae, and each one has 2-3 cells.
Prevalence	In the fetal and early childhood periods, bone replaces cartilage.	Cartilage is most common in embryo stages, where the skeletons are first made up of cartilages.
Appearance	The 6th-8th week of an embryo is when bone tissues appear. After that, cartilage ossification takes place.	Late teens see the end of cartilage growth as chondrocytes cease dividing and regenerate poorly in adults.
Functions	Bone protects the body from mechanical damage and provides a structure/shape for it. Bone is responsible to produce RBC and WBC.	They preserve the flexibility and shape of fleshy appendages, and reduce friction at joints. Cartilage acts as shock absorbers between the weight-bearing bone.