Basic Medical Sciences

There are different basis on which bones can be classified. The bones might be classified on the basis of shape or on the basis of development or on the basis of the region where they exist or finally on the basis of structure. In order to get adequate knowledge of classification of bones it is good to understand all the basis of classification and the corresponding types of bones.

Classification of bones on the basis of shape: On the base of shape the bones can be classified into the following types;

Long bones: These bones are long in composure and are of further three types that are typical long bones, miniature long bones and the modified long bones. The typical long bones are represented by bones of the limbs such as humerus, ulna, radius etc. The miniature long bones are represented by the bones of the phalanges. The modified long bones are represented by the clavicle.

Short bones: These bones are of short composure and usually have specified shapes according to which they are named. The examples are the scaphoid, lunate, pisiform etc which are all carpal bones.

Flat bones: These bones have a flat composure resembling shallow plates. Example is the scapula bone.

Irregular bones: These bones are irregular in shape such as the vertebral bones.

Pneumatic bones: These are the bones which contain air spaces in them such as the maxilla bone.

Classification on the basis of development: On the basis of development the bones are classified into the following types;

Dermal bones: They are also known as membrane bones. These bones ossify in membrane (mesenchymal ossification). Examples of this category of bones are facial bones.

Cartilaginous bones: Cartilaginous bones ossify from an already present cartilage model (endochondral ossification). The examples of this category of bones are bones of the limbs.

Membro-cartilaginous bones: These bones ossify partly in membrane and partly in cartilage. Example of this type of bone is clavicle.

Classification on the basis of region: On the basis of region the bones are of the following types;

Bones of axial skeleton: These are the bones forming the parts of the axial skeleton of the body. Examples are the bones of skull and vertebral column.

Bones of the appendicular skeleton: These are the bone which forms the appendages for example bones of the upper limb.

Classification on the basis of structure: On the basis of structure on which the bones are made, there are the following types;

Compact bone: The type of bone or the part of bone where the bone substance to bone spaces ratio is large is known as the compact bone.

Spongy bone: The type of bone of the part of bone where the bone substance to bone spaces ration is small is known as the spongy bone

 The human scapula bone or the shoulder bone is a flat bone present in the dorsal aspect of the shoulder. The bone has two surfaces, three angles, three borders and three processes. Each of these parts of the scapula bone will now be described in some detail;

The borders of the human scapula bone: As described above the human scapula bone have three borders. These borders are named as Medial border, lateral border and superior border.

Medial border: This is the border of the scapula lying towards the medial side that is towards the back bone. This border is a prominent one and can be traced completely from the top of the bone to the bottom.

Lateral border: This border lies at the lateral side that is towards the shoulder. This border includes the glenoid fossa at which the humerus (arm bone) forms the shoulder joint. The border is also prominent down to the base of the bone.

Superior border: This border is present at the superior aspect but is not as prominent as the other two borders because of the presence of the processes of the scapula bone.

The surfaces of the human scapula bone: The human scapula has two surfaces as described in the top of this article. These surfaces are;

Costal surface: This is the anterior surface of the scapula. It is rather a concave one and forms a fossa called the subscapular fossa. This surface is marked by three longitudinal ridges and a thick lateral ridge adjoining the lateral border.

Dorsal surface: The dorsa surface of the scapula possesses the spine of the scapula which subdivides the dorsal surface into the supraspinous fossa and the infraspinous fossa. The supraspinous fossa is smaller as the spine is towards the superior side and the infraspinous fossa is larger. The two fossae are interconnected with each other by the spinoglenoid notch.

The angles of the human scapula bone: The scapula as described in the start of the article has three angles that are the superior angle, the inferior angle and the lateral angle;

Superior angle: The sides of this angle are formed by the medial border and the superior border.

Inferior angle: The sides of this angle are formed by the medial and the lateral border.

Lateral angle: The sides of this angle are formed by the lateral and the superior border. This angle also includes the glenoid fossa which is directed laterally and upwards.

The processes of the human scapula bone: As described in the start of the article, the scapula has three processes that are spine of the scapula, the coracoid process and the acromion process.

The spine of the scapula: It is present of the dorsal side traversing the dorsal surface of the scapula transversely. It is a thick process and has two surfaces (superior and inferior) and three borders (posterior, superior and inferior). The posterior border is thick and is called the crest of the spine.

The coracoid process: The coracoid process directs forwards and laterally and it arises from the superior aspect of the scapula

The acromion process: The acromion process presents the attachment point for the clavicle bone. It has two borders (medial and lateral) and two surfaces (superior and inferior).

The humerus bone is the bone of the arm of human beings. It is the longest bone of the upper limb of human beings. The humerus is classified as a typical long bone with a diaphysis and two metaphyses. Anatomically the humerus consists of a shaft, an upper end and a lower end.

Upper end of the humerus: The upper end of the humerus consists of the following parts;

Head: It is the articular part of the upper end forming the glenohumeral joint (shoulder joint) with the glenoid cavity of the scapula. The head is rounded and forms a big sphere as compared to the glenoid cavity.

Anatomical neck: It is the line separating the head of the humerus from the rest of the upper end.

Lesser tubercle: It is a bony elevation in the form a tubercle present in the anterior aspect of the head of the humerus. It is called lesser tubercle because it is comparatively smaller than the other tubercle present lateral to it that is the greater tubercle.

Greater tubercle: It is also a bony elevation in the form of a tubercle but it is a larger than the lesser tubercle and is directed laterally and posteriorly. The posterior side of the tubercle is marked by three impressions namely upper impression, middle impression and lower impression.

Bicipital groove: It is also known as the inter-tubercular sulcus. It is a sulcus present in between the greater tubercle. The medial border of the bicipital groove is formed by the lateral side of the lesser tubercle and the lateral border by the medial side of the greater tubercle.

Surgical neck: It is the line where the upper end of the humerus joins with the shaft of the humerus. It is the most common site of fracture in humerus.

Shaft of the humerus: The shaft of the humerus is the long part of the bone. It is rounded superiorly and triangular inferiorly. It has three borders and three surfaces.

Borders: The borders are anterior border, lateral border and medial border. The anterior border forms the lateral part of the bicipital groove and continues downward. The medial border forms the medial part of the bicipital groove and continues downward to the medial supracondylar ridge. The lateral border forms the lateral supra condylar ridge in the lower aspect of the bone.

Surfaces: The surfaces are anteromedial surface (lying between the anterior and the medial border) the anterolateral surface (lying between the anterior and lateral border) and the posterior surface (lying between the medial and lateral border).

Lower end of the humerus: The lower end is the widest part of the humerus. It has both articular and non articular surfaces. The articular surfaces include a rounded capitulum which articulates with the radius bone and a pulley shaped trochlea which articulates with the ulna bone.

The non-articular surfaces include the medial epicondyle and the lateral epicondyle both of which are the bony projections on their respective sides. There are three fossae namely the coronoid fossa (where the coronoid process of the ulna is accommodated in flexed condition), radial fossa (where the head of the radius is accommodated in flexed condition) and olecranon fossa on the posterior side (where the olecranon process of the ulna is accommodated in extended condition).

The human ulna bone is one of the two bones of the forearm (the other being the radius bone). Classification wise it is a typical long bone with two epiphyses and one diaphysis. The ulna has an upper end, a shaft and a lower end.

Upper end of the human ulna bone: The upper end of the human ulna bone includes two processes of the bone namely olecranon process and the coronoid process. The olecranon process is towards the superior aspect and the coronoid process is towards the anterior aspect. The olecranon process of the ulna has five surfaces that are anterior, posterior, medial, lateral and superior. The anterior surface is articulatory. The posterior surface forms a triangle and the superior aspect of this triangle is the subcutaneous part of the elbow. The medial surface continues with the medial surface of the shaft of the bone, the lateral surface continues with the posterior surface of the shaft of the bone and the superior surface is quadrangular in shape providing the space for attachment of the triceps muscle.

The coronoid process has four surfaces that are superior, anterior, medial and lateral. The superior surface is articulatory forming the lower part of the trochlear notch of ulna. The anterior surface is rough and triangular in shape. It also contains the tuberosity of ulna. The medial surface continues with the medial surface of the shaft of the bone. The lateral surface provides a ridge known as the supinator crest.

Shaft of the human ulna bone: Shaft of the human ulna bone includes three borders namely interosseus border, the anterior border and the posterior border and three surfaces namely the anterior surface, the posterior surface and the medial surface.

Borders: The interosseus border is the lateral border of the bone directing towards similar border of the radius bone. This border is sharpest in its middle two third and it provides attachment for the interosseus membrane of the ulna and radius. The anterior border is a bit rounded one and it starts from the medial aspect of the tuberosity of the ulna. Inferiorly it goes down to the styloid process of the ulna. The posterior border starts from the apex of the triangular space present in the posterior aspect of the olecranon process. The border is clearly visible up to the middle of the bone and then it fades away.

Surfaces: The anterior surface is present between the anterior and interosseus border. The medial surface is present between the anterior and posterior border and the posterior surface is present between the posterior and interosseus border. One thing to be remembered about the posterior surface is that it is divided into three compartments by two lines. An oblique line divides it into two compartments and then the lower compartment is divided by a vertical line into two.

Lower end of the human ulna bone: The lower end of the human ulna bone includes the articulating surface for the inferior radio-ulnar joint. It also includes a styloid process. Between the head and the styloid process, there is a groove for the tendon of the extensor Carpi Ulnaris.

The attachment of the muscle might be the origin of the muscle or the insertion of the muscle. On this basis there are two types of muscles attached to the clavicle;

These include;

Pectoralis major muscle

Deltoid muscle

Sternohyoid muscle

Sternocleidomastoid muscle

These include;

Trapezius muscle

Subclavius muscle

For complete article visit http://www.helium.com/items/1755759-muscles-attached-to-human-clavicle