Classification of bones and human skeleton

Classification of bones

Bones may be classified by different ways which are
 
1. Classification of bone by shape
2. Developmental classification of bones
3. Regional classification of bone
4. Structural classification of bones

 

skeleton

1. Classification of bones by Shape

a. Long

Long bones have an elongated shaft and two epiphyses which are smooth and articular.
Long bones have 3 types
Typical
Miniature
Modified
 
Examples    Radius, ulna, femur, tibia, fibula, humerus, metacarpals, and phalanges

b. Short

The shape of short bones is usually cuboid or scaphoid.
 
Examples
Tarsal
Carpal

c. Flat

They resemble a shallow plate and form boundaries of the cavities.
 
Examples

Sternum

ribs

scapula

d.Irregular

These bones are irregular in shape.
 
Examples
Hip bones
sphenoid
first and 2nd cervical vertebrae.

e. Pneumatic

They contain large air spaces and these air spaces are lined by epithelium.
 
Examples
Maxilla
Sphenoid
ethmoid

f. Sesamoid

They are found embedded in the tendon or joints capsules. They have no periosteum and their ossification occurs after birth.
 
Example                 Patella

g. Accessory

They are not always present but may be developed from the extra centers of ossification.
 
Examples
Sutural bones of the skull
Cervical ribs
lumbar ribs

2. Developmental Classification of Bones

a. Dermal

They ossify in the membrane and thus derived from mesenchymal condensations.
 
Examples
Frontal
parietal
maxilla

b. Cartilaginous

These ossify in cartilages and thus derived from cartilaginous models.
 
Examples
Humerus
femur
vertebral column
thoracic cage

c. Membrano-cartilaginous

These ossify partly in membranes and partly in cartilages.
 
Examples
Clavicle
Mandible
occipital
temporal
sphenoid

d. Visceral

These bones developed from pharyngeal arches. These are few.
 
Example
Hyoid
part of mandible
ear ossicles

3. Regional Classification

Regionally bones may be classified into two classes which are

a. Axial Skeleton

The axial skeleton includes bone of
Skull
vertebral column
thoracic cage

b. Appendicular Skeleton

The appendicular skeleton includes bone of
Pectoral girdles
upper limbs
pelvic girdles
lower limbs.

4. Structural Classification of Bones

Structurally bones may be classified into two classes which are

a. Compact

These are dense and extremely porous bones.

b. Spongy

These are open in texture and is made up of a meshwork of rods and plates.

c. Lamellar

Both spongy and compact bones consist of lamellae and hence they are lamellar bones.

d. Woven Bones

The collagen fibers and crystals are randomly arranged in this type of bones.
 
Examples
Fetal bones

e. Fibrous

These are found in young fetal bones.

f. Dentine

Present in teeth.

g. Cement

present in teeth.

Human skeleton

It is the framework of the bod. An adult human consists of two hundred and six bones. The bone mass reaches its maximum level at the age of twenty-one. The human skeleton can be divided into two subdivisions that are 1.axial and 2. Appendicular skeleton. The axial skeleton consists of a vertebral column, ribs, skull, and associated bones. The Appendicular skeleton is formed by the shoulder girdle, pelvic girdle, upper limb, and lower limb. The human skeleton performs various functions such as support, movement, protection, etc.

Functions

The human skeleton performs six major functions that are
1. Support
2.  Movement
3.  Protection
4.  Production of blood cells
5.  Storage of mineral
6.   Endocrine regulation

Support

The skeleton makes the internal framework of the body that supports the body and also maintains the shape of the body. Skeleton provides a floor for the structures of the body. For example pelvis,  associated ligaments provide floor to the pelvic structure. Another example is ribcage because without it the intercostal muscles and lungs will collapse.

Movement

There are joints that are present between the bones. These joints allow the movement. Some joints allow a wider range of movement while some have restricted movement. For example, a ball and socket joint allows a greater range of movement while the pivot joint of the neck allows less movement. The movement of the bones is lowered by the skeletal muscles that are attached to the skeleton. Muscles, bones, and joints produce movement and are coordinated by the nervous system of the body.

Protection

Another important function of the human skeleton is the protection of vital internal organs from being damaged.
For example

1.  Skull protects the brain
2.  Vertebrae protect the spinal cord
3.   Ribcage, sternum protects the lungs, heart, and major blood vessels

Blood cell production

Bone marrow is present in the bones in which the development of blood cells takes place. In children, the development of blood cells occurs in the long bones such as the femur while in adults it occurs mainly in the pelvis and sternum.

Storage

The bone matrix is capable to store calcium ions and marrow has the ability to store iron.

Endocrine regulation

Osteocalcin is a hormone released by the bone that regulates blood sugar and fat deposition. This hormone increase insulin secretion and sensitivity.

Clinical significances

There are many disorders related to the human skeleton but here we will discuss only two of them that are arthritis and osteoporosis.

Arthritis

Arthritis is a disorder of joints on which inflammation occurs in one or more joints. Joints that are affected by arthritis may be painful to move or may move in the wrong direction, or become immobile. The symptoms of arthritis are different in person because of the type of arthritis the person has. The most common type of arthritis is osteoarthritis. There are over 100 types of arthritis.

Symptoms

1. Inability to walk
2.  Stiffness
3.  Malaise
4.  Fatigue
5.  Weight loss
6.   Poor sleep
7.   Muscle aches
8.   Tenderness
9.    Difficult to move joint
10.   Muscle weakness
11.   Loss of flexibility
12.   Decreased aerobic fitness

Treatment

The cure for rheumatoid arthritis and osteoarthritis is not known. Treatment can be done according to the type of arthritis that also includes physical therapy, lifestyle changes, orthopedic bracing, and medications. Medication can help to reduce inflammation in the joints that decrease the pain and it also slowed the process of inflammation.

Osteoporosis

Osteoporosis is a condition in which bone mineral density is reduced that increases the chances of fracture. Osteoporosis is more commonly found in females after menopause. Osteoporosis that occurs after the menopause is known as postmenopausal osteoporosis.

Treatment of osteoporosis includes
1. Stop smoking
2.  Decrease alcohol consumption
3.  Exercise regularly
4.  Healthy diet.

Diagnosis
Bone mineral density and conventional radiography are used to diagnose osteoporosis. The popular method of measuring the bone mental density is dual energy X-rays absorptiometry.