Tag: our skeletal system and the skin

The bones of the limbs along with their girdles constitute the appendicular skeleton. Each limb is made of 30 bones. The bones of the hand (forelimb) are humerus, radius and ulna, carpals (wrist bones 8 in number), metacarpals (palm bones 5 in number) and phalanges (digits 14 in number).

The salts of magnesium and calcium forms an integral part of the skeletal system. Magnesium combines with phosphates, to form magnesium phosphate which contributes to the bone density. It forms major part of dry matter of bones. Osteoporosis is caused, due to the decrease in the density of calcium and magnesium salts in the body. It also helps in muscle contraction. 60% of the total magnesium are present in the bones.
So, the correct option is D.

2 muscles namely flexor and extensor are involved in the movement of the bone. This is because a muscle cannot work in 2 directions. It can only pull a bone, but cannot push it. So, option B is the correct answer. 

The human shoulder is made up of three bones: the clavicle also known as collarbone, the scapula also known as shoulder blade, and the humerus.

Cervical = 7
Thoracic = 12
Lumbar = 5
Sacrum = (1) 5
Coccyx = (1) 4
Total No. of bones 33

The tarsals are the cluster of seven articulating bones in each foot situated between the lower end of tibia and fibula and the metatarsus. These tarsal bones are calcaneus, talus, cuboid, navicular and 3 cuneiform bones. So, the correct answer is '7'.

• The forelimb comprises of humerus, radius, ulna, carpals, metacarpals, and phalanges.
  
• The humerus is the long bone in the upper arm. It is located between the shoulder and the elbow joint. At the shoulder, the humerus connects to the frame of the body via the glenoid fossa of the scapula. Hence humerus is a bone of forelimb.
  
• So, the correct answer is 'Humerus'.
  

The number of phalanges in animals is often expressed as a "phalangeal formula" that indicates the numbers of phalanges in digits. Most land mammals including humans have a 2-3-3-3-3 formula in both the hands and feet which means that the thumb has two phalanges and the other fingers each have three. So the correct answer is '2,3,3,3,3'.

There are two bones in the shank area which are the tibia and fibula. The fibula is smaller and thinner than the tibia. These two bones connect the ankle to the knee and work together to stabilize the ankle and provide support to the muscles of the lower leg. So, the correct answer is 'Tibia-fibula'.

In the human arm, the trochlea of the humerus is the medial portion of the articular surface of the elbow joint which articulates with the trochlear notch or sigmoid notch on the ulna in the forearm.