Long Bone
1. Features Of Long Bone
Table of Contents
1. It is placed vertically in the body or in the long axis of the body.
2. Its length is more than breadth.
3. It has
- Shaft with two expanded ends,
- Three surfaces and three borders
- One diaphysis and more than two epiphyses, and
- Medullary cavity.
Skeletal System Parts
Read And Learn More: Anatomy Notes And Important Question And Answers
4. It
- Serves as a lever for muscular actions.
- Transmits weight, from axial to the appendicular skeleton.
- Develops in cartilage.
- Forms joints with upper and lower ends and with interosseous border.
5. Surfaces of long bones are covered by periosteum except articular surfaces.
Skeletal System Parts
2. Sub-Classification of Long Bone
1. Typical long bone: It has all the features of long bone.
1. Examples of typical long bones
- Humerus,
- Radius,
- Ulna,
- Femur,
- Tibia, and
- Fibula.
2. Modified Long Bone: Some of the characters of typical long bones are modified.
- It does not have medullary cavity.
- It ossifies in membrane or cartilage or both.
- The clavicle transmits the weight from the appendicular skeleton to axial skeleton. The body of the vertebra transmits the weight from axial to the appendicular skeleton.
Example
1. Clavicle
2. Body of vertebra
3. Miniature long bone (mockery of long bone): It is smaller in all dimensions, namely, length, breadth, weight and diameter and has only 1 epiphysis,
- Metacarpals,
- Metatarsals, and
- Phalanges.
Short Bones
Short Bones Introduction: The bones which are not long called short bones. They are cubical in shape and present six surfaces.
Skeletal System Parts
1. Short Bones Features: Out of six surfaces
- Four are articular, and
- Two are non-articular.
2. Articular surfaces give attachment to muscles and ligaments.
3. They are pierced by blood vessels.
4. Short Bones Examples
1. Carpal bones:
2. Tarsal bones:
3. Sesamoid
5. Ossification
- They ossify in cartilage.
- They ossify after birth except talus, calcaneus and cuboid which ossify in intrauterine life.
Skeletal System Parts – Pneumatic Bone
Introduction: The pneumatic bone has outer and inner tables. It is lined by mucoperiosteum and contains air.
1. Site: Bones lining the respiratory passage, e.g.
1. Paired: Maxilla
2. Unpaired
- Frontal,
- Ethmoid,
- Sphenoid.
2. Features: In the pneumatic bone, the spongy substance is replaced by the air-filled paranasal sinuses.
3. Functions:
1. It acts as Air conditioning chamber.
- It changes humidity and temperature of the inspired air.
- It makes the air free from foreign particles.
2. It acts as Resonance (prolongation and intensification of sound) of the voice.
3. It improves the Timbre (quality of musical sound) of the voice.
4. It provides Insulation.
5. They reduce the weight of the bone by 200 to 300 g.
4. Development
- They develop in the membrane due to differential growth of 2 tables.
- The inner table breaks up and penetrates into neighbouring mucosa and forms the pneumatic bone.
Sesamoid Bone
Sesamoid Bone Introduction: It is oval-shaped nodules, a few mm in diameter varying in shape and size which develops in tendons or/and joint capsule.
1. Sesamoid Bone Nomenclature: Arabic term Sesameseed-like, oidresemblance.
2. Sesamoid Bone Evolution: Phylogenetically it is part of skeleton.
3. Sesamoid Bone Structure: It is formed by fibrous tissue, cartilage or bone which develops in tendon. It exerts a considerable amount of pressure on bony structure.
4. Sesamoid Bone Ossification: It ossifies in 2nd decade except patella which ossifies in the 1st decade.
Skeletal System Parts
5. Sesamoid Bone Characters: NO
1. It does not have:
- Medullary cavity,
- Primary centre,
- Haversian system, and
- Periosteum.
2. It has articular or non-articular surface.
3. The articular surface is covered by hyaline cartilage.
4. It is lubricated by bursa or synovial fluid.
6. Sesamoid Bone Functions: The exact function is not definitely known. However, the following functions are attributed.
SESAMOID
- Serves as a mechanical advantage to the tendon.
- Ensures (makes certain) the prevention of wear and tear of the tendon.
- Stabilises the local circulation.
- Alters the direction of pull of the muscle.
- Maintains the local circulation.
- Overcomes the pressure.
- Insures (protects) the vessels and nerves.
- Diminishes the friction.
Site: Following are the sesamoid bones
7. Sesamoid Bone Applied Anatomy
Failure of ossification is mistaken for fracture of bone, e.g. patella.
Stress fracture occurs in ballet dancers and long-distance runners.
Skeletal System Parts
Periosteum
(Greek. Peri—around, osteon—bone)
1. Periosteum Definition: The surface of the shaft and part of the ends are covered by periosteum
1. Periosteum Features
1. At the ends of the bones, the periosteum blends with the fibrous capsule of the joints.
- The external surface of any bone is, as a rule, covered by a membrane called periosteum.
- In long bones, only the diaphysis is covered by periosteum. It is present as far as epiphyseal line. Here it is continuous with the capsule of the joint.
2. Periosteum is absent in
- Bones covered with articular cartilage,
- Epiphyses of long bones, and
- Sesamoid bone.
3. Variation of thickness: It is related to age. It is more vascular and thicker in children than adult.
4. Factors keeping the periosteum close to the bone.
- Sharpey’s fibres are very dense at the attachments of tendon and ligaments.
- Blood vessels: They run from the periosteum to the bone. They supply the bone substance and the marrow.
2. Structure of periosteum: It consists of 2 layers
1. Outer fibrous layer: It is made up of densely packed fibres with some connective tissue cells. It acts as a limiting membrane. It sends bundles of collagen fibres into the bone. These are perforating fibres of Sharpey.
- They anchor the periosteum.
- They are particularly strong at the attachments of tendons or ligaments.
- The ends of long bones are covered with the articular cartilage except distal end of terminal phalanges.
2. Deeper vascular layer: It contains
1. Blood vessels, and
2. Cells: They are
- Osteoblast cells: They are bone-forming cells. They lay down new bone on the surface of the shaft.
- Osteoclast cells: They are bone-destroying cells.
3. Variation of attachment of periosteum to bone: Attachment of periosteum varies with bone and age.
1. In relation to type of bone.
1. In long bones, it is more closely connected at the
- Extremities of long bones,
- Prominences,
- Pressure points, and
- Over the areas to which the tendinous attachments are present.
2. On flat bones, it is less adherent.
2. In relation to age: In early life, it invests loosely than in adult
4. Fate of periosteum
- At the ends of bone, it continues as fibrous capsule.
- The anterior longitudinal ligament blends with the periosteum and loses its identity in the middle of the sacrum.
5. Periosteum Blood supply: It is mainly supplied by periosteal vascular plexus. These are the branches of muscular arteries.
6. Periosteum Nerve supply: It has rich nerve supply through somatic nerves. They are sensory nerves. They carry pain fibres. This is the reason why fractures are extremely painful.
7. Periosteum Lymphatic: Lymphatic vessels are abundant in the periosteum.
2. Functions of periosteum
- Osteogenic,
- Protective,
- Nutritional,
- Growth of the bone, and
- Repair of bone.
3. Periosteum Applied anatomy
- If periosteum is removed, blood supply of the bone is lost. The bone underlying periosteum undergoes degeneration and death.
- The position of nutrient foramen of fibula is important clinically. When obtaining a graft surgically, the periosteum and nutrient artery are generally removed with the piece of bone. This helps graft to remain alive when transplanted to another site.
- When bone is fractured, the blood vessels and periosteum are damaged. These vessels bleed, and clot is formed between the broken ends of the fractured bone. It is called fracture haematoma.
- The periosteum is thick over the mandible. In a fracture of the mandible, the fractured bones are not displaced because of the thick periosteum.
- Pain in Paget’s disease is believed to result from the stretching of the periosteum.
- The inflammation of periosteum results in local pain and tenderness.
Epiphysis
(Epi—above, physis—growth)
Epiphysis Introduction: The segment of bone which develops from secondary centre is called epiphysis. Secondary centre is one which develops after birth.
1. Epiphysis Classification
1. Based on number of epiphysis (structurally).
- Simple: Ends of long bone develop from many epiphyses. They fuse independently with shaft, e.g. femur.
- Compound: The ends of bone develop from many centres and these centres unite to form a single epiphysis. The single epiphysis subsequently fuses with shaft, e.g. head of humerus.
2. Based on functions
- pressure epiphysis
- Traction epiphysis
3. Atavistic (a great grandfather’s grandfather) epiphysis: In the initial part of evolution, some part/s of bone/s were isolated bones. They were getting nutrition from the adjacent bones. In later part of evolution, such bone/s fuse/s with the adjacent bones and form part of the bone. Such bones are called atavistic bones.
- Coracoid process of scapula
- Ostrigonum: It is triangular bone present at the back of talus. Sometimes it occurs as independent bone.
4. Aberrant epiphysis (wandering, diverging from an accepted standard, away from normal): The miniature long bones have only one epiphysis. It is usually at distal end of the miniature long bone except for the 1st metacarpal which is present at proximal end. Sometimes, some of the metacarpals, metatarsals may have additional epiphysis/es which are called aberrant epiphysis/es. Examples are:
- Distal end of 1st metacarpal.
- The proximal end of 2nd metacarpal and 2nd metatarsal
- The proximal end of 5th metacarpal and 5th metatarsal
2. Epiphysis Applied anatomy
- The head of the femur receives blood supply from the epiphyseal artery. It pierces the epiphyseal cartilage. In the case of separation of the epiphyseal plate, from the neck of the femur, there is a necrosis of the head due to loss of blood supply.
- The artery supplying the upper end of the tibia does not pierce the epiphyseal plate. Hence, separation of the upper end will not result in loss of blood supply in the upper end.
Diaphysis
(Dia—in between, physis—growth)
Diaphysis Introduction: It is the elongated part of long bone present between two growing ends.
It develops from one primary centre. It forms the shaft of long bone.
1. Diaphysis Blood Supply is mainly by nutrient artery, a branch of reginal (of the respective region) artery. The direction of nutrient artery is opposite the direction of growing end.
2. Diaphysis Structure: It is described as:
- Periosteum: It is compact and strong. It is adherent only to the shaft of long bone. It is fibrous in nature.
- Inner: It is spongy and site of erythropoiesis.
3. Diaphysis Growth
1. Height by interstitial growth.
2. Thickness by appositional growth.
4. Diaphysis Applied Anatomy
Infection of the bone causes osteomyelitis.
Metaphysis
(Meta—end, physis—growth)
Metaphysis Introduction: It is the epiphyseal end of diaphysis. It is the peripheral part of the shaft which is in contact with epiphyseal plate of cartilage.
1. Metaphysis Characters
1. It is the most
- Active part of bone
- Vascular part of bone, flooded in the lake of blood.
2. It is the site of
- Attachment of tendons, ligaments,
- Maximum pull, stress, strain and tension, and
- Maximum growth.
2. Types of the metaphysis
1. Intracapsular
1. Metaphysis is present inside the capsule.
2. Examples: Upper and lower ends of
1. Humerus, and
2. Femur
2. Extracapsular
1. Metaphysis is present outside the capsule.
2. Examples: Upper and lower ends of
1. Radius, and
2. Tibia
3. Metaphysis Blood supply: It is by following arteries
1. Nutrient artery,
2. Periosteal artery, and
3. Juxtaepiphyseal artery.
4. Metaphysis Applied anatomy
- Metaphysis is susceptible to infection in the immature bone.
- Infection of long bone primarily affects metaphysis. The nutrient arteries in the region of metaphysis form hairpin bend. The constricted area of nutrient arteries may get blocked by thrombus. It results in necrosis. It is the common site of osteomyelitis in children.
- Infection can reach through the intracapsular metaphysis and cause septic arthritis.
- Since muscles, ligaments and joint capsules are attached close to metaphysis, this is likely to be damaged by sheering strain of the muscle.
- It is the region favouring haematogenous spread of infection.
Blood Supply of the Long Bone
1. The blood supply of long bone is by following arteries
1. Nutrient artery
1. Features
1. It is a branch of artery of the region.
2. Its direction is away from growing end.
3. The direction of the nutrient foramen is decided by the slogan.
“Towards the elbow I go, and away from the knee I flee.”
2. Peculiarities: It is tortuous before it enters the nutrient foramen for following reasons
- For the uniform distribution of blood, and
- To avoid rupture during contracting and relaxation of the muscle.
3. Number: It is usually one except in femur which has two nutrient foramina which transmit arteries.
4. Course
- It enters the compact bone through nutrient foramen situated in the middle of shaft.
- It divides into ascending and descending branches into the medullary cavity.
- Each ascending and descending branch divides into many small branches which turn down to form a hairpin loop.
5. It anastomoses with
- Periosteal artery,
- Metaphyseal artery, and
- Epiphyseal artery.
6. Distribution: It supplies
- The inner two-thirds of compact bone,
- The spongy bone, and
- Haversian system of less than 2 mm diameter.
2. Metaphyseal artery
1. Arises from anastomosing arteries around joint.
2. Enters metaphysis through joint capsule.
3. It shows looping pattern during growth of bone.
3. Epiphyseal artery: Divides into two types—depending upon mode of blood supply.
4. Periosteal artery: It enters bone through Volkmann’s of haversian system. It supplies outer one-third of the compact bone. It is branch of muscular arteries.
5. Muscular artery: It is a branch of muscular artery supplying adjacent muscles.
6. Endosteal artery: It supplies the inner surface of the bone.
2. Applied anatomy
Osteomyelitis: The small embolus blocks the nutrient arteries at the site of hairpin bend. The distal part of the bone results into avascular necrosis. This condition is called osteomyelitis.
Shaft of long bone is affected in congenital syphilis.
Growing End
1. The active end of the long bone is called growing end. It is plate of cartilage between diaphysis and epiphysis. Examples: All long bones.
2. Growing End Features
1. The part of the bone which develops from secondary centre is called epiphysis. The epiphysis which appears first and fuses with the diaphysis (shaft) last is called growing end.
2. Each bone has two epiphyseal ends.
- Growing end
- Non-growing end
Growing end does
- More work,
- For longer time, and
- Faster.
The non-growing end does
- Less work,
- For shorter time, and
- Slow.
3. Bone increases in length at growing end.
4. The growing end grows longer time and more rapidly than the other end.
5. The growing end is opposite to the direction of nutrient foramen. The direction of nutrient foramen is decided by a slogan. “Towards the elbow I go, and away from the knee I flee”. shows the growing end of different long bones. shows the growing end of different long bones.
3. Growing End Applied anatomy
The knowledge of growing end of the concerned long bone is necessary for surgeons to manipulate the space. The situation arises when a boy/girl meets an accident. In a fracture of limbs, accompanied by severe infection, there are chances of rapid spread of infection. In rapidly and uncontrolled infection, amputation is advised to prevent the spread of infection. The lower end of the femur, being growing end, may continue to grow and pierce the skin and protrude out. To avoid such consequences, surgeon keeps extra space to accommodate the growth of bone.
Damage to the growing end during growth leads more deformity than the damage to the less growing end.
Primary Centre of Ossification
Primary Centre of Ossification Introduction: It is the centre from which the elongated shaft of the bone ossifies.
1. Primary Centre of Ossification Appearance: The primary centre appears before birth.
2. Primary Centre of Ossification Examples
- Shaft of all long bones, and
- Short bones like talus, calcaneus and cuboid.
3. Exception: Carpal and tarsal bones, the centre for which appears after birth.
Secondary Centre of Ossification
Secondary Centre of Ossification Introduction: The centre of the long bone which appears after birth is called secondary centre.
1. Secondary Centre of Ossification Example
- Ends of all long bones,
- Greater trochanter of femur, and
- Greater tubercle of humerus.
2. Secondary Centre of Ossification Gender variation: Secondary centres tend to appear earlier in females than males.
3. Secondary Centre of Ossification Exception
- Lower end of femur, and
- Upper end of tibia, the centre for these bones appear at birth.
4. Secondary Centre of Ossification Applied anatomy
The secondary centre for lower end of the femur or upper end of the tibia appears just after birth. This fact is used in determining the dead born child with a viable newborn. This is confirmed by taking an X-ray of the knee joint. The presence of centre at lower end of femur or upper end of tibia confirms the viability of child and excludes stillbirth. Please note, the absence of a secondary centre does not exclude viability.
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