Human Skeleton | Definition, Structure & Functions

Human Skeleton

Human Skeleton Definition:

Human Skeleton defines a framework of bone or other rigid material which supports and contains the body of human, animal, or plant. Skeleton defines as the structure of a framework which consists of all bones in the human body or animal. The structure of these bones helps the body of animals or humans in movement, walking, and performs different other tasks easily. The model of the body that contain bones other connective tissues or other rough hard material which protect the internal organs and supports the body. The Human Skeleton consists of 206 bones, out of these six bones are tiny bones of both ears. The largest bone of the Human Skeleton is the thigh bone (or femur). The tongue has no bone. An organ system is a group of organs that work together in order to perform many different tasks. Human Skeleton is an organ system in which a model of different bones and other rigid material work together for performing many functions.

Human Skeleton Diagram

Human Skeleton model is described below:

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Human Skeleton Labeled

Functions of the Skeleton:

There are many different functions performed by a Skeleton. Without a skeleton, the body is noting as it cannot perform even a single task. There are six main functions that are performed by the skeleton of the body, are structural support, locomotion, protection, blood cell production, storage, and endocrine regulation.

  • Structural Support:

The most important functions of the skeleton are the gross functions, which can be observed by vision. Support of Body Structure is one of a gross function and can be seen. Like the steel beam of the building gives a structure or shape to the building and supports its weight, the same function for the skeleton. The skeleton gives shape and made the structure of the body and supports its weight.

  • Locomotion:

Skeleton of the body also supports the locomotion of the body. Bones in skeleton attached to each other on the specific points known as Joints. With the help of these joints, bones facilitate the movement of the body. Some of the bones serve as the only support for muscles. The body cannot produce movement without a skeleton on its own.

  • Protection:

Bones also protects the internal organs from outer damage or any type of injury. All the internal organs of the body are covered by the skeleton. For example, ribs protect our lungs and heart from any external damage and bones of the cranium (skull) protects our brain from any internal injury.

  • Blood Cell Production:

Bones also serve as the production of blood cells. The softer connection of tissues that fill the most of the interior of bone referred to as bone marrow. There are two forms of bone marrow in our body; yellow marrow and red marrow. The yellow marrow has adipose tissue; these tissues serve as a source of energy. The red marrow contains hematopoiesis; in which the blood cells produce. Red marrow is responsible for the production of red blood cells, white blood cells, and platelets.

  • Storage:

Bones also perform the function of storage of fats and minerals. Bones also store calcium, and bone marrow stores iron in ferritin. Bones are not totally made up of calcium but the mixture of hydroxyapatite and chondroitin sulfate made 70% of bone.

  • Endocrine Regulation:

A hormone (called osteocalcin) released by bone cells, which contribute to the regulation of glucose and fat deposition. Osteocalcin causes the increment of sensitivity, secretion, and reducing stores of fat.

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Bones Type:

The bones of the Human Skeleton are classified differently by their shape. Bones are classified into five main categories; long bones, short bones, flat bones, irregular bones, sesamoid bones.

  • Long Bones:

The long bones are longer in length than its width. Long bones have a shaft and two rounded ends. The shaft (or Diaphysis) has to bone marrow, and the rounded ends (or Epiphyses) covered by articular cartilage and filled by the red bone marrow. The thigh bones (or femur), tibia, ulna, and radius are examples of long bones.

  • Short Bones:

The short bones also called cuboidal bones. These bones have the same width and length. Short bones have a cube-like shape. The bones of the wrist (carpals) and ankle (tarsals) are examples of short bones.

  • Flat Bones:

The flat bones are broad and thin bones that protect internal organs and attach a broad surface of muscles. Sternum (bones of the breast), ribs, the roof of the skull, the shoulder blades (scapulae) are examples of flat bones.

  • Irregular Bones:

The irregular bones have complex or irregular shapes and may have a ridge, long, short, or notched surfaces. Hip bones and many skull bones are examples of irregular bones.

  • Sesamoid Bones:

The sesamoid bones are flat and small bones. These bones have a similar shape to sesame seeds. Sesamoid bones are produced in tendons and may be present in the knees, hands and feet joints.

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Bone Structure:

The bone is structured by many types of tissues. These are explained below:

  • Compact Bone:

Compact bones also known as Cortical bones. The outer layer of bone is covered by dense and strong material. 80% of adult bone mass is made by compact bone.

  • Spongy Bone:

Spongy bone contains a network of rod-like or trabeculae structure. These bones are less dense, lighter and more flexible than cortical (compact) bones.

  • Articular Cartilage:

The bones have two forms; Diaphysis and Epiphysis. The width of the bone called epiphysis. Articular Cartilage is thin layers of cartilage which perform the function of reducing friction and acts as a shock absorber. Articular Cartilage covers the epiphyses.

  • Epiphyseal Plate or Epiphyseal Line:

Epiphyseal Plate also is known as the growth plate. In a growing bone, it is a layer of transparent cartilage. Epiphyseal Plate becomes an Epiphyseal Line and replaced by osseous tissue when in early adulthood, the bone stops the process of growing.

  • Red Bone Marrow:

Red Bone Marrow is the production of all red blood cells and platelets in adult humans. It also produces around 60 to 70 percent of lymphocytes. The red bone marrow also helps to get rid of old red blood cells.

  • Yellow Bone Marrow:

The yellow bone marrow works as a fats storage. It maintains the correct environment for functions of bone. In some conditions like fever or blood loss, it may remit to Red Bone Marrow.

  • Periosteum:

The periosteum consists of blood vessels, lymphatic vessels, and nerves that nourish the compact bones. The periosteum is a fibrous membrane that covers the outer surface of the bone.

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Nutrient Artery:

Nutrient Artery is also known as Medullary Artery. Nutrient Artery transfers the medullary cavity of all within along bone. One or two veins occupy the nutrient artery; it sends branches downward and upward to the bone marrow. The most apparent blood vessels of the bones are a nutrient artery.

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A thin vascular membrane of connective tissue is known as Endosteum. Endosteum lines the bony inner surface tissue which forms long bones medullary cavity. During the long period of malnutrition, this endosteal surface is commonly resorbed. As a result, cortical thickness becomes less.