Understanding Human Bones: Definition, Types, Anatomy, and Functions

The rigid calcium rich organs of human body, which forms the crucial part of human skeletal is called bones. The bones are meant to provide the support, prote

FORENSIC ANTHROPOLOGY

Shubham Kumar

1/28/20246 min read

beige and white skeleton
beige and white skeleton
white human skull
white human skull

The bones in human body are the prime organs which the part in body framework. Their study is very helpful in fields like forensic anthropology, physiotherapy, and in another medical fields. In case you aren't into any of the fields, then also you must know about your body and the reason how are you able to move your fingers to read this blogpost 😊.

In this article we are going to get valuable information about the human bones, its definition, types, anatomy and functions.

Human Bone

The rigid calcium rich organs of human body, which forms the crucial part of human skeletal is called bones. The bones are meant to provide the support, protection of internal organs, moreover, serving as attachment points in muscles to enable movement. Notably, at the time of berth, human body is comprised of more than 250 bones, however as the time passes, most of the bones fuses with each other to form a single bone. As a result, in an adult human being, we witness 206 bones.

Human bones are the important part of human skeletal system, in-fact, majority portion of human skeletal is made up of bones only. Bone are basically made up of calcium, magnesium, phosphorous, sodium and Hydroxyapatite. However, these minerals are not behind the formation of bones. The rigid organ, that is the hum bone is formed by the action of bone cells. Bone cells like Osteoblasts and Osteocytes are behind its formation and maintenance, and Osteoclasts is responsible for destruction of bones to release tissues.

Classification of Bones

Bones are classified on the basis of shape, since each and every bone have similar functions as discussed above and somewhat similar in anatomy and morphology too. However, there is one more classification based on the density and arrangement of bone cells in bones.

On the Basis of density of bones, it sis classified as:

  • Compact Bone

  • Spongy Bone

On the basis of shape, bones are classified as:

  • Long Bone (Femur, Humerus)

  • Short Bone (Tarsals, Carpals)

  • Flat Bone (Cranium, Sternum)

  • Irregular Bone (Vertebrates)

On the Basis of density of bone, it is classified as

On the basis of histological structure, the human bones are classified as compact and spongy bones. This category focus on the difference in the composition of bone cells in a bone, which ultimately hinders its density.

Compact Bone

  • Structure: Compact bone is dense and solid, composed of tightly packed osteons (or Haversian systems).

  • Location: It forms the outer layer of most bones and the shafts (diaphysis) of long bones.

  • Function: Compact bone provides strength, support, and protection. It is well-suited for bearing weight and resisting mechanical stress.

Spongy Bone

  • Structure: Spongy bone has a porous and trabeculated structure, consisting of a network of thin bony plates (trabeculae) with spaces between them.

  • Location: Spongy bone is typically found at the ends of long bones (epiphyses), within flat bones (e.g., sternum, ribs), and in the interior of certain short and irregular bones.

  • Function: Spongy bone provides some structural support but is more involved in shock absorption and making bones lighter.

On the basis of shape, bone are classified as

The prime classification, or we can say the major classification of bones is done on the basis of shape only. On the basis of shape bones are classified as long bones, short bones, flat bone and irregular bones.

Long Bones

Those bones who possess the morphology worth representing long and wide are referred as long bones. They have a shaft with heads at both sides. Long bones fall into the category of compact bones, in other words, they are much denser and tougher as compared to other bones. The longest bone in a human body is femur. Example of other longs bones like-humerus, tibia, ulna, radial etc.

Anatomy of long bones

A long bone is divided into two parts, they are diaphysis and epiphysis.

Epiphysis- The head and shaft of the long bone is recognized as the epiphysis. epiphysis is further divided into proximal epiphysis and distal epiphysis. The head portion of long bone is called proximal epiphysis, whereas the shaft portion is called distal epiphysis. The proximal epiphysis (head) falls under the category of spongy bone, support the base of long bone as shock absorber.

Diaphysis- The middle portion of the long bone is called diaphysis. In other words, the portion between proximal epiphysis and distal epiphysis is called diaphysis. Diaphysis falls under the category of compact bone. The point where the spongy bone ends and compact bone starts in a long bone is called epiphysis seal line. Diaphysis consists of periosteum (a thin tissue covering bone) and medullary cavity (capillaries to provide nutrition to bone)

Structure of long bones

The long bone is comprised of periosteum, Sharpey's fibers and arteries (medullary cavity).

Periosteum: The thin fibrous layer functions as the outer covering of the diaphysis, is called periosteum. It serves as the connective tissue membrane.

Sharpey's fibers: The fibers present between periosteum and compact bone, is called Sharpey's fibers. These fibers secure periosteum to underlying bone.

Arteries: The arteries present in the medullary cavity inside the diaphysis serves as the network to transport the nutrients and blood for the maintenance of bones.

Short Bones

The bone that are smaller in size than that of long bones are referred as short bones. These bones are generally similar to shapes like cube and cuboids. Short bones are mostly spongy in nature, as they are meant for high mobility, therefore, they can't be too dense. Moreover, their prime function is a shock absorber. It's because of short bones only, that multiple fighting styles like martial arts, kung-fu, boxing, etc. have been evolved. As they need high mobility in fists and feets, and both are the amalgamation of short bones. carpals in fist and tarsals in feet, are the prime examples of short bones.

Flat Bones

Those bones whose surface is somewhat similar to the thin and flat surface are referred to as flat bones. They usually possess a curved structure. Just like long bones, flat bones too possess compact and spongy bones. They have a thin layer of compact bone all around the spongy bone. Flat bones are usually middle in size and p[rotects the vital organs of human body. Example- Cranium (protecting brain) and rib cage (ribs and sternum protecting heart and lungs)

Irregular Bones

Now the remaining bones, other than long, short and flat, are called irregular bones. Their shape is undefined; therefore, they fall under the category of bones with irregular shape. Moreover, they also don't fit into the classification of other bones. Example- the hip bone and vertebrates.

Function of Bones

As discussed above, human bone forms the crucial part of human skeletal system, so most of the function of bones are somewhat similar to the function of skeletal system. Therefore, it's often regarded as the function of human skeletal system too.

Support- The skeletal system provides a structural framework that supports the body's tissues and organs. It maintains the body's upright posture and prevents it from collapsing under the force of gravity.

Protection Bones protect vital internal organs from injury and damage. For example, the skull protects the brain, the ribcage shields the heart and lungs, and the spine guards the spinal cord.

Movement: Bones, in conjunction with muscles, enable body movements. Joints allow for various types of movement, such as flexion, extension, rotation, and more.

Mineral Storage: Bones act as a reservoir for minerals, particularly calcium and phosphorus. The release of these minerals from bones helps maintain the proper balance in the bloodstream and supports various physiological processes.

Blood Cell Formation: Bone marrow, found within certain bones (especially the long bones and flat bones), is the site of hematopoiesis, the production of blood cells. Red blood cells, white blood cells, and platelets are formed in the bone marrow.

Metabolic Regulation: Bones play a role in regulating calcium levels in the body, which is critical for various metabolic functions. Calcium is involved in muscle contraction, blood clotting, nerve transmission, and other cellular processes.

Storage of Fat: Yellow bone marrow, found in the shafts of long bones, serves as a storage site for fat. This fat can be used as an energy reserve in times of nutritional need.

Facilitation of Movement: The skeletal system, along with muscles and joints, facilitates bodily movements and locomotion. It provides a rigid framework that muscles can pull against, generating the force needed for movement.