Tag: human skeleton system

The appendicular skeleton (126 bones) is formed by the pectoral girdles, the upper limbs, the pelvic girdle or pelvis, and the lower limbs. Their functions are to make locomotion possible and to protect the major organs of digestion, excretion and reproduction.

The external or internal framework which provides support to the body is called skeleton. It is of two types exoskeleton and endoskeleton. The lower group and animals possesses only exoskeleton for protection e.g. Cockroach while higher animals possess both e.g. Fish.

• A joint or articulation (or articular surface) is the connection made between bones in the body which link the skeletal system into a functional whole. They are constructed to allow for different degrees and types of movement.
• Ball and socket joint is a type of freely movable joint. For example, shoulder and hip joints.
• Ball and socket are different from the others in the following because ball and socket is a type of joint which is an articulation between two or more bones whereas the clavicle, skull, and femur are individual bones present in the body.
• So, the correct answer is 'Ball and socket'.

The clavicle is the constituent of pectoral griddle or shoulder gridle. It is called as collar bone which serves as a rigid support from which the scapula and free limb suspended. It is an arrangement that keeps the upper limb away from the thorax so that the arm has maximum range of movement. So, the correct answer is 'pectoral gridle'.

Os Innominatum is a large irregular bone that forms the bony pelvis. Os-innominatum is also called as hip bone. Each pelvic girdle is made of a pair of hip bones which are identical with each other and each made of pubis, ilium and ischium. So, the correct answer is 'os innominatum'.

• Pelvic girdle consists of two coxal bones. Each coxal bone is formed by the fusion of three bones i.e each half of pelvic girdle is made up of ilium, ischium, and pubis.
  
•  At the point of fusion of the ilium, ischium and pubis bones there is a cavity called acetabulum to which the thigh bone (femur) articulates. Hence ilium is the part of pelvic girdle.
• So,the correct answer is 'Pelvic girdle'.

The pelvic girdle is formed by a pair of bone which is the hip bone or coxal bone. The large opening in the anteroinferior hip bone between the ischium and pubis is the obturator foramen through which nerves and blood vessels pass. So, the correct answer is 'Pelvic girdle'.

Each pelvic girdle is composed of two hip bones. Pubic symphasis is a specialized joint where the pubis of one hip bone joins with the pubis of opposite hip bone. So the two halves of pelvic girdle are joined together by pubic symphasis. So, the correct answer is 'Pectoral girdle'. 

• The bones of the limbs(forelimb and hindlimb) along with their girdles (pectoral and pelvic) constitute the appendicular skeleton.
  
• The bones of the hind limb are femur (thigh bone – the longest bone), tibia and fibula, tarsals (ankle bones – 7 in number), metatarsals (5 in number) and phalanges (digits – 14 in number). Hence number of bones in the hind limb of human is 30.
• So, the correct answer is '30'.