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Skeletal system

Skeletal system:

The skeletal system is that in which is related with the different bones present in our body and the gives protection of the internal organs of the body, movement of the body and attachment of different muscles of the body.

Skeletal system

The skeletal system is of two types:

  1. Appendicular skeletal system
  2. Axial skeletal system

Axial skeletal system: It contains bones of ribs, skull, vertebral column, sternum, scapula, clavicle and hyoid bone.

Appendicular skeletal system: It contains bones of upper and lower limbs and pelvis.

Hyoid bone:

Hyoid bone is also included in skeletal system total number of bones in body are 212 (3 of each middle ear). There is no muscle attachment with these six bones of middle ears that’s why they are not taken in skeletal system.

Bone system

Skull-22 (8 cranial and 14 facial)

Vertebral column-33





Bones of upper limb-60

Bones of lower limb-60


Total – 206

Longest bone of body is femur (Thigh bone)

Shortest bone of body is stapes (Present in middle ear)

Classification of bones:

Bones can be classifies according to their shape and the formation. There are different types of bones:

  1. Long bones: The long bones are present mainly in the upper and lower limbs. The long bones contain a long shaft and upper and lower head.

Example: Humerus, radio-ulna of upper limb and femur, tibia-fibula of lower limb.

The long bones functions as the lever in the body.

  1. Short bones: The short bones are present in upper and lower limbs.

Example: Tarsals and carpals

They give strength and support example: Wrist and ankle.

  1. Flat bones: These bones contain the two layers of dense bones with a layer of spongy bone. These bones are present in the bones of skull, ribs and scapula.
  2. Irregular bones: These bones are irregular in shape.

Example: Bones of vertebral column and some bones of face.

  1. Sesamoid bones: These bones develop in the tendon of the muscles.


1. Patella bone (present in knee joint)

2. Pisiform

3. Flabella

Function of skeletal system:

  1. The skeletal system gives the definite shape and size to the body.
  2. It protects the internal soft parts of the body.
  3. The bone of the skeletal system helps in movement of body.
  4. Bones are the surface for the attachment of the muscles.
  5. The bone helps in the storage of calcium and phosphorus.
  6. Bone narrow manufacture RBCs
  7. It transmits the body weight

Classification of joints:

Joint: The joint is a point where two or more bone unites.

Types of joints:

  1. Fibrous joints: In these joints the bones are joins firmly with each other. These joints are called sutures. There is no movement in these joints.

Example: Joints of skull

  1. Cartilaginous joints: These are present in the long bones and in the vertebral column in these joints little movement is possible.
  2. Synovial joints: Maximum joints present in the bodies are the synovial joints. Maximum movement is present in these joints.

Example: Shoulder joint, elbow joint, wrist joint, hip etc.

The ankle, knee and elbow joints are hinge joint (movement in single direction)

Structure and functions of bones - Online Science Notes

Structure of bone

Skull: The skull is bony frame work of the head arranged in two parts:

  1. Cranium: It is the upper part of skull and contains 8 bones.
  2. Facial: It contains 14 bones, so the skull contains total 22 bones.

The bones of skull are paired and unpaired. The bones of skull are present as under.

Cranial bones: Frontal (1), sphenoid (1), ethmoid (1), occipital (1), perital (2), temporal (2)

Facial bones: Nasal (2), Lacrimal (2), inferior nasal concha (2), maxilla (2), palatine (2), zygomatic (2), mandible (1), vomer (1)


Cranial and facial bone

Structure of skull:

  • Skull contains 22 bones upper part contains 8 bones called cranium.
  • Lower part contains 14 bones called facial part.
  • Some bones are paired and some are unpaired.
  • The only bone of skull which can move is mandible (lower jaw)
  • Rest all of the bones of the skull are firmly joined with each other with the help of the sutures.
  • When the skull is seen from the top. It takes oral. The frontal view with eye orbits similarly it looks different tattle laterally from the below.
  • The internal part of the skull can be seen by removing the top of the skull cap.
  • The important bones of the skull are as mentioned above.

Vertebral column (Backbone): The backbone contains 33 bones it starts from the base of the skull and ends at the pelvis bone. It contains the following bones.

  1. Cervical-7(Neck)
  2. Thoracic-12(chest)
  3. Lumbar-5
  4. Sacrum-5
  5. coccyx-4(fused)

The single bone is called as vertebra. Length of the vertebral column in male is about 70 cm in female 60 cm.

  • The first cervical vertebra is ATLAS
  • The Second Cervical vertebra is AXIS

The ATLAS rotates like a white around the axis.

Thoracic vertebrae:

Divided into two groups:

  1. Typical: They are similar from T2-T8
  2. Atypical: They are different basically in function T1, T9-T12

Features: The body is heart shaped; vertebra foramen is small and circular

Lumber vertebra: Size of the vertebra increase from top to bottom. Upper four are typical and 5th is atypical features. Kidney shaped body.

Sacrum: This is a large flat triangular bone formed by the fusion of the five bones. The upper part is broad and lower part is narrow. The sacrum articulates with the hip bone.

Features: Divide into base and apex and four surfaces.

Coccyx formed by fusion of lowers four bones of the back bone. This is broader upward and pointed in lower direction.


  • It has a base
  • Pelvic surface
  • Dorsal surface
  • Lateral surface
  • Apex

Ribs: There are 12 pairs of ribs in the body each rib articulates with the sternum. The anterior ends of the last two ribs are free-posteriorly each rib articulates with the thoracic vertebrae.

Upper 7 ribs are called as true ribs the next 3 are called as false ribs and 11th and 12th are called as floating ribs.


Sternum: Single bone present in thoracic region and makes the thoracic cage.

The sternum contains the following parts:

  1. Manubrium
  2. Body
  3. Xiphoid process

Clavicle (collar bone): These are 2 in number

  • Right and left
  • This is the long curved bone one part is joined with the scapula
  • The other end helps to makes the shoulder joint.

The clavicle bone helps to attract the some of the muscles of head and neck and shoulder.

  • Scapula: These are also 2 in number
  • One on right side one on the left side
  • They help to make the shoulder joint. It contains the three borders.
  1. Superior
  2. Vertebral
  3. Axillary

Bones of upper limb

Easy Notes On 【Bones of the Upper Limb】Learn in Just 3 Minutes ...

  1. Humerus: The humerus is the largest bone of upper limb. The most important part is the head, which helps to make the shoulder joint. The lower end of the bone is triangular and flat from front to back. The shaft is the long part of bone. On the shaft there is a rough surface on attachment of dentoid muscles.
  2. Radio ulna: These are two bones radius and ulna.

The radius is the lateral and long bone present towards the thumb.

The ulna is present just opposite to the radius bone. It is wide from the upper side and rounded from lower side the upper ends of the radius and ulna helps to makes the elbow joint

  1. Carpals: There are present the 8 carpals bones there are the example of short bones. They help to make the wrist joint.
  2. Metacarpals: These are 5 in number and make the skeleton of palm.
  3. Phalanges: There are present 14 small bones, which make the skeleton of the fingers and thumbs. There are total 30 bones present in the single upper limb.(Proximal, middle, digital)

Bones of lower limb: There are present 30 bones in lower limbs which are as following:

Lower Limb: Bones, Muscles, Joints & Nerves (With images ...

  1. Femur/Thigh bone: Longest bone of our body the most important feature is the long anatomical neck in upper part.

The upper head of the femur makes the hip joint. There are maximum important muscles of the thigh are attached on the femur bone.

The lower and is joined with the upper ends of tibia fibula and makes the knee joint.

  1. Tibia fibula: These are the two bones present below the femur. The tibia bone is present towards the toe of the lower limb just opposite to this there is fibula present.

The lower ends of these bones are joints with the 7 short bones (Tarsals)

  1. Tarsals: These bones are seven in number and make the ankle joint.
  2. Meta tarsals: There are 5 Meta tarsals present which may be sole of the foot.
  3. Phalanges: They are 14 in number 3 for each finger and 2 for the thumb (toe).

Patella: The patella bone is present in the knee joint.

Patellar Fractures (Broken Kneecap) - OrthoInfo - AAOS

  • It is present in front of lower head of femur and upper head of tibia fibula
  • This is the example of sesamoid bone
  • It is developed in tendons of quadriceps muscles
  • The lower part is rounded and called base.
  • The lower part is pointed and called apex
  • The internal surface is smooth and outer surface is rough.
  • There is presence of synovial fluid in the knee joint.

Pelvis bone (Hip bone)

This is also called as the hip bone. The hip bone is large irregular bone made of three parts.

  1. Ileum
  2. Pubis
  3. Ischium

These parts fuse at a depressed area which is acetabulum.

There are two hip bones in our body.

  1. Ileum: Forms the upper expanded plate like part of hip bone. It contains the upper and lower ends three borders and three surface
  2. Pubis: It forms the anterior and inferior part of the hip bone. The pubis contains a body and two Rami.
  3. Ischium: It forms the posterior and inferior part of hip bone. Ischium has a body and a ramus.
Pelvis bone


Male PelvisFemale pelvis
There are following differences between male and female pelvis bones.The obdurate foramen is oval shaped with more diameters.
The pelvic inlet is triangular. The obdurate foramen is triangular in male with short diameter, The pelvic cavity is narrow and funnel shapedThe pelvis cavity is milder and the side walls are parallel.
The male pelvis is narrow with the public arch (75-80)The public arch is 90 or more
  • Joints: The joint is a point where two or more than two bones white.

Joints of upper limb:

  1. Shoulder joint: It is synovial joint. This is of the ball and socket type.

Shoulder Injuries From Trauma – Scapula Nonunion | HOPE TBI

  • The shoulder joint is formed by upper head of numerous and the glenoid cavity of spatula.
  • The cartilage is thin in the centre and thick at the periphery.
  • The joint is surrounded by a number of the bursae.
  • They help in movement of the joint.
  • The blood supply is by humeral and supra-scapular artery.
  • Nerve Supply – Axillary pectoral nerves.
  1. Elbow joint: It is also synovial joint and compound joint because it is formed by more than two bones.

It is formed by the lower head of the humerus and upper heads of radius and ulna.

  • The elbow joint is of the hinge type.
  • The blood supply is by the anastomoses artery

Nerve supply – Radial and ulnar nerves

  1. Wrist joint: Synovial joint and compound joint this joint is formed by lower head of radius and ulna and the carpal bones. This is a compound joint. The blood supply is by the radial colmar arteries.

Nerve supply – anterosseus and interosseus nerves

  • Joint of lower limb:

Hip joint: This is the synovial joint of ball and rocket variety. It is very simple joint. The hip joint is formed by the upper head of femur and the acetabulum of the pelvis bone.

It is much similar to shoulder joint it can also move in different direction. This is more stable as compare to shoulder joint. The head of the femur is thickest in the center and thin at the periphery.

The hip joint transmits the body weight in the lower direction of body.

Blood supply – Branches from the superior obturator and femoral, gluteal arteries

Nerve supply – Femoral obtutrator and superior gluteal nerve

Knee joint: It is synovial joint of hinge variety, compound joint formed by the lower ends of the femur and upper ends of the tibia fibula.

Patella bane is present in front of 3 tones. The synovial membrane covers all the structures within the joints

Blood supply – Branches of descending genicular, popliteal and tibial artery.

Nerve supply – Obturator femoral and tibia nerves

Ankle joint: This is also the synovial joint of hinge variety movement is in single direction. This joint is formed by the lower ends of tibia fibula and talus bone (bore of heels)

Blood supply – anterior tibial and perineal arteries.

Nerve supplyPerineal and tibia nerves

  • Classification of synovial joints according to their movement:
  1. Plane joint: In this joint the opposite articular surface are plane, this permits movement of bones on each other.

Example: Sternoclavicular joint.

  1. Hinge joints: The hinge joints resemble to the hinge on a door.

Example: Elbow, knee and ankle joints.

  1. Pivot joints: In this joint a central bony pivot is surrounded by a bony ligamentous ring and the rotation is that only movement.

Example: Superior radio-ulnar joint.

  1. Condylar joints: In this joint there are two convex surfaces that articulate with two concave.

Example: Meta carpo-phalangial.

  1. Ellipsoid joints: The flexion, extension can take place but no rotation.

Example: Wrist joint

  1. Saddle joints: These joints permit the flexion extension and rotation.

Example: Carpo metacarpal joint of thumb

  1. Ball and socket joints: The movement is maximum

Example: Shoulder and hip joint.

  • Sutures: The sutures membrane between the edges of two growing bones contains the estrogenic and fibrous membrane periostium covering the outer and inner surface of the bones.
  • Function of sutures: The sutures provide the growth and bind together the opposite margins of the bones.

Fibrous joint - Wikipedia


  1. Coronal
  2. Sagittal
  3. Lambdoid
  4. Metopic
  5. Coronal suture: This suture is present between the frontal bone and the anterior margins of partial bone.
  6. Sagittal suture: This suture is present between the two parietal bones.
  7. Lambdoid suture: It is present between the occipital bone and the posterior margins of parietal bones.
  8. Metopic suture: It is present between the two holves of the frontal bones and is present in 3-8% of the cases.

Functions of periosteum:

  1. The muscles are attached with the periosteum and it maintains the shape of the bone.
  2. It provides the nutrition to outer 1/3rd of the cortex of medulla.
  3. It helps the blood supply to the bone by the periosteal arteries
  4. It helps to increase the width of the bone.
  5. It gives protection to the bone
  6. The periosteum is sensitive to pain it is important structure in healing the bone injuries.

Microscopic structure of bones:

The microscopic structure of compact bone is as following.

  1. Lamellae: This is the cylindrical layers of the calcified matrix.
  2. Lacunae: These are the small space containing the tissue fluid in which the bone cells are present in between the hard layers of lamellae.
  3. Canaliculi: These are ultra-small canals which are present in all direction from the tacunae and connecting them to each other to a larger canal the haversion canal.
  4. Haversion canal: It contain blood vessels and lymph vessels from the haversion canal the tissue fluid moves through the canaliculi to lacunac and their bone cells at a short distance about 0.1mm. 1000s of haversion canals make up the compact bone of a single bones diaphusics.
  5. Calcaneus bone (spongy bone): These are different in microscopic structures than the compact bone. The spongy bones don’t anatine the haversion canal. It contains the trabaculae filled with the bone marrow. There is blood supply in the bones by the periosteal arteries.

Development of bone:

The bone formation is called as the osteo-genesis by two different methods the formation of bone take place:

  1. Intramembranous: By three month often the fertilization of ovum, the skeletal system appears but not the bones most of the structure contains the hyaline cartilage. The formation of skill during pregnancy starts by fibrous membrane including the mandible.

The intramembranous ossification takes place within the connection tissue membrane.

The cement substances and the collagen fibers make the bone matrix after this the deposition of the calcium salt takes place.

  1. Endo-chondrial ossification: Most of the bones are form from the hyaline cartilage.

First of all periosteum is formed then the ring of bone is formed.

After this the calcification of the hyaline cartilage takes place.

The progress takes place from diaphysis to epiphysis and the bone grows.

Bone narrow:

The bone marrow is the vascular connective tissue present in the medullary cavity of the bone. At the birth the bone marrow is red with active haemopoises. The parts of the developing long bone:

  1. Epiphysis: This is the part of the bone which develops from the secondary center of ossification.

Example: The ends of the long bone.

  1. Diaphysis: This is the part of the bone which develops from the primary part of the ossification.

Example: Shaft of long bone.

  1. Metaphysis: This is the part of the bone where the active growth of the bone is seen. It is present at the junction of the epiphysis and diaphysis of the long bone.

Structurally the bones contain the outer covering periosteum just below this part there is compact bone present which is made up of lamellae which contains the bony plates of fibers.

  • The bone matrix contains the calcium and phosphate.
  • The osteoblasts are the immature cells present near the periosteum.
  • The oesteocytes are the mature cells.

Bone matrix:

  1. The bone matrix is very dense and contains the deposits of calcium salt. The bone matrix contains the bone cells or osteocytes within the pockets.
  2. The narrow passage through the matrix is called as the canaliculi. These are present between the lacunae and blood vessels.
  3. They form the branching network for the exchange of nutrition waste product and gases.
  4. Except the joints the periosteum covers the outer surface of the bones. The calcium phosphate is present about 2/3rd of the total weight of the bone. In the bone the collagen fibers provide the organic frame work for the formation of hydroxyapatite crystals.

Parts of a long bone, 2.2.2 human skeleton, By OpenStax (Page 4/4 ...

Skeletal system | Veterian Key

Blood supply of long bone image

Bone remolding:

It is also called as the bone metabolism. The bone metabolism is a lifelong process where the mature bone tissue is removed from the skeleton and the new bone tissue is formed. These processes are also controls the reshaping of the bone or the fractures

In 1st year of life 100% of skeleton is replaced.

In adults remolding is 10% per year only.


The cartilage is the special connection tissue present in the body. The cartilages are rigid structure; they are supportive and protective in function.

  • They can bear pressure.
  • They are present in the body where the elasticity and rigidity is required.
  • They are avascular (no direct blood supply)
  • The nourishment is by the different from the nearby tissue.
  • The repair of the cartilage takes time due to its vascularity.
  • They don’t contain nerves, so they are insensitive.

Blood supply to long bone: The long bone is supplied by four sets of long vessels.

  1. Nutrient artery: This artery supplies the blood to the bone narrow and inner 2/3rd of cortex
  2. Metaphysical artery: It is also known as juxta epiphyseal
  3. Epiphyseal artery: It is present just above the metaphysical artery.
  4. Periosteal artery: This supply the blood in outer 1/3rd of the cortex

There are three types of cartilages:

  1. Hyaline cartilage: This cartilage contains the homogeneous matrix and is glassy and transparent in appearance, it contains the collagen fibers and chondrocytes in groups called as the cells nest conditions. This type of cartilage is present in postal cartilages of the anterior ends of the ribs.

Skeletal frame work of larynx:

Example: Thyroid, cricoid and arytenoid cartilage. It is present in the tracheal rings.

  1. Elastic cartilages: These are made up of elastic fibers and the chondrocytes. It is more fibrous than the hyaline cartilage. This type of cartilage is present in the following structures.

1) Pinna of ear

2) Epiglottis of pharynx.

  1. Fibro cartilage: It contains mainly thick bundles of collagen fibers and a few chondrocytes. It has much strength and elasticity. This type of cartilage is present in the articular disc of the temporo-mandibular joint, vertebral disc of the backbone, glenoid cavity of shoulder joint and acetabulum of hip joint.

Important features of cartilage:

  1. The cartilage is avascular, it receive the nutrition through the diffusion from the nearby tissue.

Many cartilage masses are linked with cartilage canal which convey the blood vessel.

These cartilage canals supply the nutrition to the deepest part of the cartilage.

  1. The cartilages do not contain the nerves so they are insensitive.
  2. The cartilage is surrounded by the perichondrium.
  3. The growth is by the interstitial method.
  4. When the cartilage calcifies the chondrocytes die because the nutrition stops.
  5. The cartilages don’t contain the lymphaties
  6. The cartilage has the poor regeneration order

Synovial fluid: It is the fluid filled in the synovial cavity and helps in the movement of the joints.

Synovial membrane: This is a pink smooth shiny cellular connective tissue membrane which lines the fibrous capsule from outside.

Functions of synovial membrane:

  1. It secretes the synovial fluid
  2. It removes the harmful or extra matter from the synovial fluid.

Difference between newly born skill and adult skull:

Bumps, Ridges and Soft Spots on Baby's Head

  1. The skull of the new born has large size cranium as compare to facial skeleton. It is small and contains tiny bone collection.
  2. The mandible and maxilla are not fully developed as there are no teeth.
  3. The sinuses are also undeveloped (Air pockets present around the nose).
  4. The bony part of external lay is not developed. Therefore the eympanic membrane is nearer to the surface.
  5. The mastoid process is also absent. Therefore the facial nerve behind styloid process is also superficial.
  6. The skull at birth is partly ossified and the gaps or fontanels are present between the various bones. These gaps are filled with membranous structures. It helps in the growth of the brain during first year of life.

Clinical and applied aspects:

  1. Fracture: It is defined as the break in the continuity of a bone. The most common cause of the fracture is the trauma or injury.
  2. Osteomyelitis: The infection of bone is known as the osteomyelitis. The most common part affected is metaphysis of bone.
  3. Arthritis: It is the inflammation of the joint and the most common indication is by pain. Swelling and decreasing the movement/moiling of the joint.

Cause: The common cause is bacterial infection, gout, wear and tear of articular cartilage of joint due to age factor.

  1. Gout: It is the increase in uric acid level in the blood with the attacks of acute arthritis, the deposition of urate crystals in kidneys and joints.
  2. Dislocation of joint: The loss of contact of two articular surfaces of a joint due to injury.