Question

List and explain different types of Bones.

Answer 1

Hint: The hard parts that are present inside the animal body constitute bones. Bones are of different types and of different structures. Their main function is to protect the internal organs of the body like the brain, lungs, heart, etc. Human skeletal system is the whole structural form of the human body that is made up of bones. The human skeletal system is of two types, i.e., exoskeleton which is externally present, e.g., nails, hairs, etc., and endoskeleton which is internally present and consists of bones.

Complete answer:
The endoskeleton is divisible into two parts on the basis of the position of the skeletal structures in the body. These are:
Axial skeleton: It consists of skull, vertebral column, sternum and ribs and it is present on the median longitudinal axis of the body.
Appendicular skeleton: It constitutes the bones of pectoral (shoulder bones) and pelvic (hip bone) girdles and bones of arms and legs. It is present at the lateral sides of the body, which actually extends outward from the principal axis.
Our skull consists of total \[22\] bones that include two sets of bones named as cranial and facial bones. Cranial bones are \[8\] in number and they form the hard, outer protective covering for the brain, known as cranium. The facial region forms the front part of the skull and is made up of \[14\] skeletal elements. One more U-shaped bone called hyoid is also included in the skull and is present at the base of the buccal cavity. The middle ear contains three tiny bones named- Malleus, Incus and Stapes. They are collectively known as Ear Ossicles. The skull region joints with the superior region of the vertebral column. And this joint is formed with the help of two occipital condyles (dicondylic skull).
The vertebral column is formed of \[26\] bones which are serially arranged units named as vertebrae and is dorsally placed. It constitutes the main framework of the trunk. Vertebral column is extended from the base of the skull. Each vertebrae have a central hollow portion which is known as the neural canal via which the spinal cord passes. Atlas is the first vertebra and it articulates with the occipital condyles. Starting from the skull the vertebral column is differentiated into \[7\] cervical, \[12\] thoracic, \[5\] lumbar, \[1\]-fused sacral and \[1\]-fused coccygeal regions. Function of the vertebral column is to protect the spinal cord, supports the head and serves as a point of attachment for the ribs and forms the musculature of the back. A flat bone is present on the ventral midline of the thorax named as breastbone or Sternum.
There are \[12\] pairs of ribs. Each rib is a thin flat bone which is connected to the vertebral column and to the sternum dorsally and ventrally respectively. On its dorsal ends, it has two articulation surfaces and is hence known as bicephalic. First \[7\] pairs of ribs are known as true ribs and are connected with sternum and thoracic vertebrae with the help of hyaline cartilage. The \[{8^{th}}\], \[{9^{th}}\], and \[{10^{th}}\] pair of ribs join the seventh rib with the help of hyaline cartilage and they do not articulate directly with the sternum and so they are called false (vertebrochondral) ribs. \[{11^{th}}\] and \[{12^{th}}\], the last two pairs of ribs are not connected ventrally and are known as floating ribs. The rib cage constitutes thoracic vertebrae, ribs and sternum together.
Each limb is made up of \[30\] bones which constitutes the bones of hands (fore limb) and legs (hind limb). Bones of hands are humerus, ulna and radius, carpals, metacarpals and phalanges. Bones of legs are femur, tibia and fibula, tarsals, metatarsals and phalanges.
The pelvic and pectoral girdle help in the articulation of upper and lower limbs respectively with the axial skeleton. Both girdles are made up of two halves each. Each half of the pectoral girdle is formed of a scapula and a clavicle. Each pelvic girdle is composed of two coxal bones. Each coxal bone is formed by the fusion of three bones named- ilium, ischium and pubis.

Note:
Femur (thigh bone) is the longest bone in the human body. Patella, a cup shaped bone covers the knee ventrally and is also known as knee cap. The main function of the skeleton includes support, protection, muscle attachment, movement, body formation, blood cell formation, mineral reservation and helps in breathing and hearing. According to the shape and size, bones are classified into four types which include:
Long bones: e.g., femur, tibia and fibula. Humerus, radius and ulna.
Short bones: e.g., metacarpals, metatarsals and phalanges.
Flat bones: e.g., scapula, sternum and cranial bones.
Irregular bones: e.g., vertebrae, carpals and tarsals.