Human Bones, Joints and Muscles

By | April 2, 2015

1. Bones

The Skeleton System:

  • The human endoskeleton is made up of bones and cartilage of various types.
  • Bone is a hard connective tissue in which the ground substance is very hard and contains calcium salts.
  • The marrow of the long bones is the site for the haemopoiesis, i.e. formation of blood and blood cells.
  • Human skeleton consists of 206 pieces of bones.
  • The skeleton system is categorized into axial skeleton and appendicular skeleton.

1.1) Axial Skeleton (80 bones):

  • Axial Skeleton consists of skull, vertebral column, ribs and sternum, i.e. the skull skeletal elements which are present along the longitudinal axis of the body. There are 80 bones in axial skeletal system.
  • Mandible is the only movable bone in the skull of man.
  • In human beings, 26 vertebrates are present serially along the length of the trunk starting behind the occipital bone of the skull. The vertebral column is the main axis of the body, which articulates with skull, pectoral girdle, pelvic girdle and the ribs. Each vertebra is centrally hollow.
  • Vertebral column gives support to the trunk and provides places for the attachment of the ribs and bones of pelvis as well as it permits movement and projects the spinal cord.
  • There are 29 bones in human skull.
    Cranial bones:

    1. Frontal bone
    2. Parietal bone (2)
    3. Temporal bone (2)
    4. Occipital bone
    5. Sphenoid bone
    6. Ethmoid bone

    Facial bones:

    1. Zygomatic bone (2)
    2. Superior and inferior maxilla
    3. Nasal bone (2)
    4. Mandible
    5. Palatine bone (2)
    6. Lacrimal bone (2)
    7. Vomer bone
    8. Inferior nasal conchae (2)
  • There are six bones in ears.
    1. Malleus (2)
    2. incus (2)
    3. Stapes (2)
  • There is one bone in the throat i.e. hypoid bone.
  • There are 25 bones in the thorax.
    1. Sternum
    2. Ribs (2*12)
  • There are 26 bones in the vertebral column.
    1. Cervical vertebrae (7) including atlas & axis.
    2. Thoracic vertebrae (12)
    3. Lumunar vertebrae (5)
    4. Sacrum
    5. Coccyx

1.2) Appendicular skeleton (126 bones):

  • The appendicular skeleton is made up of bones of the arms and legs and their supports.
  • The shoulder gridle consists of the scapula (shoulder blade) and the calvice (collar bone).
  • The skeleton of the arm is divided into the humerus (upper arm), radius and ulna (forearm); carpals (wrist bones); metacarplals (palm) and phalanges (fingers). Ulna is situated towards the little finger side, whereas radius towards the thumb side.
  • The thumb has two bones, whereas the other fingers have three bones i.e. proximal, middle and distal.
  • The bones of leg consist of the femur (thigh), tiba and fibula (leg), tarsals (back of the foot), metatarsals (forefoot) and phanlanges (toes).
  • The leg is attached to the trunk by a pevlic gridle made up of two hip bones. each consists of three bones are fused in adults.
  • Femur is the longest and heaviest bone of the human body. Femur, tibia and fibula bones together support the shank of the leg. tibia is larger than fibula and bears major body weight.
  • Exoskeletons; The hard material is formed mainly on the outside of the body and is often called an exoskeleton. Insects such as beetles or dragonflies and crustaceans like crabs or lobsters have a hard covering to their bodies called a cuticle.

Girdles:

  • There are four bones in the shoulder girdle.
    1. Clavicle or collarbone (2).
    2. Scapula or shoulder blade (2).
  • There are two bones in the pelvic girdle.
    1. Private area(2)

Limb bones:

  • There are 6 bones in the arms.
    • Humerus (2)
    • Ulna (2)
    • Radius (2)
  • There are 54 bones in the hands.
    Wrist (carpal bones):

    1. Scaphoid bone (2)
    2. Lunate bone (2)
    3. Triquetrum bone (2)
    4. Pisiform bone (2)
    5. Trapezium bone (2)
    6. Trapezoid bone (2)
    7. Capitate bone (2)
    8. Hamate bone (2)

    Palm or metacarpal bones:

    1. Metacarpal bones (5*2)

    Finger bones or phalanges:

    1. Proximal phalanges (5*2)
    2. Intermediate phalanges (4*2)
    3. Distal phalanges (5*2)
  • There are eight bones in the legs:
    1. Femur (2)
    2. Patella (2)
    3. Tibia (2)
    4. Fibula (2).
  • There are 52 bones in feet.
    Ankle (tarsal) bones:
    1. Calcaneus (heel bone (2)
    2. Talus (2)
    3. Navicular bone (2)
    4. Medical Cuneiform bone (2)
    5. Intermediate cuneiform bone (2)
    6. Lateral cuneiform bone (2)
    7. Cuboidal bone (2)

    Instep (metatarsal) bones:

    1. Metatarsal bone (5*2)

    Toe bones:

    1. Proximal phalanges (5*2)
    2. Intermediate phalanges (4*2)
    3. Distal phalanges (5*2)

Human skeleton system

2. Joints:

Joints are the place of articulation between two or more bones or between a bone and a cartilage.
Types of Joints:

  1. Fixed or immovable or Fibrous Joints: there is no space between the bones and sutures present between the skull bones and the articulation of the roots of teeth with sockets of maxillae and mandible. Sockets of maxillae are the two examples of such a joint.
  2. slightly Movable or Catilaginous Joints: In such joints, the opposing surfaces are connected by fibrocartilage. Joints between adjacent vertebrae are examples of such joints.
  3. Freely Movable or Synovial Joints: In such joints a space between the bones is present, called synovial cavity. This cavity remains filled with a viscous and slippery synovial fluid. The examples of synovial joints are 1. Ball and socket joints, 2 Hinge joints, 3. Pivot Joints, 4. Gliding joints and 5. Ellipsoidal joints.

3. Muscles:

  • The muscles itself is made up of bundles of hair-thin muscle fibre, which contain even thinner microscopic myofibrils. In turn, each muscle fibril contain bundles of long chain like substances. these are muscle protein actin and myosin.
  • Human muscles constitute nearly 40 – 50 % of total body weight.
  • Muscle tissue is composed of 75% water, 20% protein and 5% non-protein organic material and minerals.
  • A muscle is a body part designed to get shorten or contract.
  • The muscles that act together to produce a movement are called synergists. As the record of heart is known as Electro-Cardiogram (ECG), the record of electrical activity of muscle is called as Electro-mygogram (EMG).
  • Muscles are broadly divided into three categories:
    • 1. Skeletal Muscles: Skeletal muscles are straited muscle attached to the bones by tendons and help in the movement of parts of skeleton. skeleton muscles are responsible for movement to facilitate locomotion as these muscles are controlled by conscious mind and they can move on their free will. Hence they are also known as voluntary muscles.
    • 2. Cardiac Muscles: Cardiac muscles are striated muscles and occur exclusively in heart and these are involuntary muscles.
    • 3. Smooth Muscles; Smooth Muscles are found inside the wall of the hollow internal organs, like alimentary canal, reproductive track, blood vessels, etc.
  • The cardiac muscles and smooth muscles are such muscles whose action is not under the control of will power hence they are known as involuntary muscles.
  • The muscles that act in opposition to each other are called antagonists.
  • The muscles that act most powerfully during any given movements are called prime movers.
  • The largest muscle is the stapedius, deep inside the ear. It is just a few millimeters long and thinner than cotton thread.
  • A muscle can only pull on a bone not push it.
  • Each muscle is linked by nerves to the brain.
  • On the basis of the presence or absence of a red pigment called myoglobin, the skeletal muscles are classified into red and white muscles.

Human anterior and posterior views of the muscular system