Skeletal system , Appendicular skeleton structure and importance
Skeletal system consists of Axial skeleton & Appendicular skeleton , Appendicular skeleton consists of pectoral girdle and the upper limbs , The pelvic girdle and the lower limbs , The pectoral girdle is connected to the upper limbs of the appendicular skeleton while the pelvic girdle is connected to lower limbs of the appendicular skeleton .
Pectoral girdle and the upper limbs
The pectoral girdle
The pectoral girdle consists of two identical halves , where each half consists of ( scapula and clavicle ) , the scapula is triangular dorsal bone whose inner end is broad , while the outer end is pointed and has a process to which the clavicle is attached .
The clavicle is ventral thin bone that is attached to the sternum anteriorly and to the scapula laterally , There is a cavity at the outer end of scapula which called the glenoid cavity through which the articulation with the fore-limb ( head of humerus ) takes place , forming the shoulder joint .
Each upper limb consists of Upper arm , Forearm and Hand bones , Upper arm that is supported by one bone called humerus , Forearm consists of two bones which are :
- Radius : It is small in size and can rotate around the fixed ulna .
- Ulna : its upper part has a depression where the inner projection of humerus fits into it .
Hand bones consists of :
- Wrist consists of two rows of 8 bones called carpals and their upper ends are attached to the lower part of radius ( is not attached to the ulna ) , while their lower ends are attached to the bones of hand palm .
- Hand palm consists of five long thin bones called metacarpals that are followed by the bones of five digits ( fingers ) .
- Hand digits : five digits , where each one of them consists of three bones called phalanges , except the thumb which consists of two phalanges only .
The pelvic girdle and the lower limbs
The pelvic girdle consists of two identical halves that are fused at the ventral side at a region called the pubic symphysis and each half consists of ( dorsal ilium , pubis and ischium ) , where the dorsal ilium is attached .
- Anteriorly and ventrally to the pubis .
- Posteriorly and ventrally to the ischium .
At the position of attachment of ilium and ischium bones , there is a deep depression called acetabulum into which the head of thigh bone ( femur ) fits , forming the hip joint , The public symphysis is the region at which the identical halves of pelvic girdle are fused at the ventral side .
Each lower limb consists of Femur , Shank bones and Foot bones .
- Femur is the thigh bone and at its lower end , there are two big processes that articulate with the shank at the knee joint that has a patella in front of it , Patella is a small rounded bone that found in front of the knee joint .
- Shank bones consists of two bones which are the inner tibia , the outer fibula .
- Foot bones consists of Ankle , Foot and Food toes .
Ankle consists of seven bones that are irregular in shape called tarsals and the largest one is that at the back which forms the heel .
Foot consist of five bones called metatarsls which are long , thin and ended with the bones of five toes .
Food toes : Five toes , where each of them consists of three bones called phalanges , except the big toe which has two phalanges only .