PATELLA: osteology, myology,side determination, clinical anatomy

Bone:patella

Features

• Also called knee cap.
• Patella is a sesamoid bone in the tendon of quadriceps femoris muscle.
• It is the largest sesamoid bone in the body.

Side determination

• The patella is shaped like a disc .
• It has a process that projects inferiorly .
• The anterior surface is rough with several vertical striations.
• The posterior surface has a large articular fascet which is subdivided into large lateral and small medial areas.

Osteology

• Roughly triangular in outline.
• It has anterior and posterior surface that are separated by three borders (superior, medial and lateral).
• The superior border is also called the base .
• The medial and lateral borders are the medial and lateral margins of the bone.
• The inferior part of the bone shows the downward projection called the apex.
• The anterior surface is rough and can be felt through  the overlying skin.
• It is slightly convex and is vertically striated by the fibres which run over it.
• Posterior surface is articular . It articulates with the patellar surface on the anterior aspect of the condyle of the femur.
• It consists of a large lateral part and a smaller medial part, the two parts are separated by a ridge.
• The lateral and medial parts are further subdivided by faint ridges into superior, middle and inferior fascet.

Myology

• The superior border gives attachment to the quadriceps femoris.
• The apex and the adjacent part of posterior surface gives attachment to the ligamentum patellae.
• The medial and lateral borders receive fibres of vastus medialis and lateralis respectively and also fibres of fascia lata.
• The collected fibres of the concerned muscle and the fascia Lata together  forms the medial and lateral patellar retinaculum respectively.

Ossification

• The patella ossifies from several center that appear between 3rd and 6th year of life . The  centres soon fuse with each other.

FEMUR: osteology,myology, ossification, clinical anatomy.

Bone: femur.


Features

• Longest and the strongest bone of the body .
• Extends from the hip to the knee.

• It is a long bone with a shaft ,an upper end and a lower end.

Side determination

• Upper end has a pounded head that is joined to the neck by an elongated neck.
• The head is directed medially .
• Shaft is convex forwards.
• Anterior aspect of the shaft is smooth and posterior aspect is marked by a prominent vertical ridge called the Linea aspera.

Osteology

Upper end

• The upper end consist of head,neck and two there projections called the greater and lesser trochanteric.

Head

• Directed medially, upwards and forwards.
• Round in shape (make more than half of a sphere).
• Near its centre there is a pit or fovea .

Neck

• Connects the head and the shaft.
• It is separated from the shaft by the intertrochanteric line in front and the intertrochanteric crest behind.

Greater trochanter

• Large quadrangular projection on the lateral aspect of the upper end .
• On the medial surface is a small depression called the trochanteric fossa.
• The greater trochanter also has an anterior,a lateral and a posterior surface .
• The projecting conical point of the upper part is called the tip of the trochanter.

Lesser trochanter

• Is a conical projection attached to the shaft where the lower border of the neck meets the shaft. It points medially and backwards.

Intertrochanteric crest

• The posterior part of the greater and lesser trochanter are joined together by a prominent ridge called the intertrochanteric crest.

Quadrate tubercle

• A little above its middle , the crest bears a rounded elevation called quadrate tubercle.

Intertrochanteric line

• The junction of the neck and the shaft is marked by a much less prominent intertrochanteric line.
• Below the lesser trochanter, the intertrochanteric line becomes continuous with the spiral line.

Shaft

• It is smooth anteriorly but it's posterior aspect is marked by a rough vertical ridge called the linea aspera.
• It has three borders (lateral,medial, posterior) and three surfaces  (anterior, lateral and medial).
• The lateral and medial border are rounded . The posterior border corresponds to the Linea aspera.
• The anterior surface is very smooth .
• The Linea aspera has distinct medial and lateral lips.
• When traced upward  to the upward 1/3rd of the shaft, the lips diverge. The medial lip become continues with the spiral line. The lateral lip becomes continuous with a broad rough area called the gluteal tuberosity.
• The area between the gluteal tuberosity and the spiral line constitute a fourth surface.
• The two lips of the Linea aspera diverge from each other over the lower 1/3rd of the shaft to become continues with the ridges called the medial and lateral supracondylar lines.
• Popliteal surface is an additional surface between medial and lateral supracondylar lines.

Lower end

• Consists of the two large condyles called the medial and lateral condyles.
• Anteriorly the two condyles are joined together and lie in the same plane as the lower part of the shaft.
• Posteriorly they project much beyond the plane of the shaft .
• Posteriorly they project much beyond the plane of the shaft and are separated by a deep intercondylar notch or fossa.
• Lateral condyles are more or less flat . A little behind the middle it is marked by a prominence called the lateral epicondyle.
• When viewed from the medial aspect , the medial condyle is seen to be convex. The most prominent point on it is the medial epicondyle.
• The uppermost part of the medial condyle is marked by a sharp prominence called the adductor tubercle.

Myology
Muscular insertion

Greater Trochanter

• Gluteus minimus: inserted into the anterior aspect of the greater trochanter.
• Gluteus medius: is inserted into the oblique strip running downwards and forwards  across the lateral surface of the greater trochanter.
• Piriformis: inserted into the upper border of the greater trochanter.
• Obturator internus and Gemelli: inserted into the anterior part of the medial surface of greater trochanter.
• Obturator externus: inserted into the trochanteric fossa on the medial surface of the greater trochanter.

Lesser trochanter 

• Psoas major : inserted into the medial part of the anterior surface of the lesser trochanter.
• Iliacus : inserted  into the medial side of the base of the lesser trochanter and into a smaller area below latter.
• Pectineus inserted along a line descending from the root of the upper end of the lineaaspera .

• Quadratus femoris: inserted into the quadrate tubercle.
• Gluteus maximus: inserted into gluteal tuberosity.
• Adductor brevis: inserted between the insertions of the pectineus and adductor Magnus. Lower part of the muscle inserted to the Linea aspera.
• Adductor longus: inserted into the middle 1/3rd of the Linea aspera.
• Adductor Magnus: inserted into the medial margin of the gluteal tuberosity, the Linea aspera and the medial supracondylar line.

Muscular origin

• Vastus lateralis: has long linear origin. The line begins at the upper end of the intertrochanteric line. It passes along the anterior and lower borders of the greater trochanter, the lateral margin of the gluteal tuberosity and the lateral lip of the Linea aspera.
• Vastus medialis: originates from the lower part of the intertrochanteric line , the spiral line ,the medial lip if the Linea aspera and the medial supracondylar line up to the adductor tubercle.
• Vastus inermedius : arises from small areas on the anterior surface of the shaft. 
• Articularis genu: arises from small areas on the anterior surface of the shaft below the origin of the vastus intermedius.
• Biceps femoris : (short head ) arise from the Linea aspera and from the upper part of the lateral supracondylar line.
• Popliteus : arises from the lower part of the lateral supracondyle.

Ossification

• Second long bone to start ossifying .
• The primary centres appears in the shaft during the 7th foetal week.
• The secondary centres appear at the upper end of the bone ; one each for the head , the greater trochanter and the lesser trochanter.
• Each of these centres fuses independently with the shaft in the reverse order of appearance.
• The lesser trochanter fuses at about 13 years.
• The greater trochanter fuses at about 14 years of age.
• The head fuses around 16 years of age.
• One secondary centre for the distal end appears before birth in the 9th  month of the foetal life. It fuses with the shaft between 16th and 18th year.

Clinical anatomy

• Congenital dislocation:occurs as a result of imperfectly formed bone ends.
• Avascular necrosis: caused due to insufficient blood supply to the to the head of the femur. The head collapses and the hip joint becomes disorganised.
• Arthroplasty : repairing of the joints using artificial components.

HIP BONE: osteology, myology, ossification, clinical anatomy.

Bone: hip bone.

Features

• Also called os coxa.
• Large irregular bone with three parts ilium, ishium,pubis.
• These three parts meet at the acetabulum (large deep cavity placed on the lateral aspect of the bone).
• Below and medial to the acetabulum is a large oval or triangular aperture called the obturator foramen.

Side determination.

• Acetabulum faces laterally.
• Ilium directed upward.
• Triangular shaped pubis placed anteriorly.

Osteology

• Consists of three parts ilium,ishium, pubis.

Ilium

• Also called os ilium or flank bone.
• Fan shaped.
• Consists of two borders anterior and posterior, two surfaces medial and lateral and a iliac  crest.

Iliac crest

• Extends from anterior superior iliac spine to posterior superior iliac spine.
• Iliac crest subdivided into ventral segment and the dorsal segment.
• Ventral segment consist of the anterior 2/3rd .
• The whole length of the ventral segment shows a broad intermediate area that is bounded by inner and outer lips.
• The outer lip is most prominent about 5cm behind anterior superior iliac spine,this prominence called tubercle of the iliac crest.
• The inner lip gets obliterated as traced posteriorly.
• The posterior 1/3rd of the iliac crest forms the dorsal segment. It has medial and lateral surface separated by a ridge.

Anterior border

• Extend downwards from the anterior superior iliac spine to the acetabulum.
• Its lowest part present a prominence called the anterior superior iliac spine.

Posterior border

• Extends from posterior superior iliac spine to the back of the acetabulum. Few centimetres below the posterior superior iliac spine the posterior borders presents another prominence called posterior superior iliac spine.
• The lower part of the posterior border curves down to form the boundary of a deep notch called the greater sciatic notch.
• The border joins the posterior border of ischium.

Lateral surface

• Also called gluteal surface.
• The surface contains three ridges called posterior, anterior, inferior gluteal lines.

Posterior gluteal line

• Vertical.
• Extend from the iliac crest above to the posterior inferior iliac spine below.

Anterior gluteal line

• Convex upward and backward.
• Extends from the greater sciatic notch to the iiac crest.

Inferior gluteal line

• Horizontal.
• Extends from anterior superior iliac spine to the posterior end of greater sciatic notch.

• The gluteal surface of the ilium bears a prominent groove just above the acetabulum.
• The lower part of the gluteal surface continues with ilium.

Medial surface

• Has two distinct areas iliac fossa and the sacropelvic surface.
• Iliac fossa : smooth,concave and forms the wall of the greater pelvic surface.
• Iliac fossa occupies anterior part of the medial surface.
• Sacropelvic surface : lies behind the iliac fossa .
• Subdivided into three parts                                                                  # the upper rough part constitute iliac tuberosity.                  # Middle part called auricular surface articulates with the lateral side of sacrum.                                                            #a smooth pelvic part forms the wall of the lesser pelvis.( Preauricular sulcus found in this area).

Medial border if ishium: superior iliac fossa and the sacropelvic surface.

• The border is sharp at the upper part .
• The lower part is rounded and forms the arcuate line.
• At the lower end of the arcuate line, iliopubic eminence can be seen.

Ischium

• L shaped part of the hip bone.
• Evens down from the acetabulum and then passes forward to join the pubis.

Body of the ischium

• The upper part of the body forms the inferior and posterior parts of the acetabulum.
• Ishium also has a projection called ramus surfaces.
• The lower part of the body has three surfaces dorsal,femoral, pelvic.

Dorsal surface

• The lower part of the dorsal surface has a large rough impression called ischial tuberosity.

Ischial tuberosity

• Divided into upper and lower parts by a transverse ridge.
• Each of these divided into medial and lateral parts.
• The upper lateral part gives attachment to semimembranosus muscle and is separated by an oblique line from the upper medial part which gives allachment to the semitendinosus and biceps femoris.
• The lower lateral part gives attachment to the hamstring part of the adductor Magnus.
• The lower medial part is covered by fibrous tissue and usually have an overlying bursa.

Femoral surface

• Directed downwards, foreward and laterally.
• Continuous with the external surface of the ramus of the ischium.

Pelvic surface

• Smooth and forms the wall of the pelvis.
• The ramus of the ischium has two surfaces anterior and posterior.
• The ramus of the ischium joins with the ramus of the pubis to form ischio pubis ramus.

Pubis

• Forms the antroinferior part of the hip bone near the midline.
• Consist of body superior ramus and inferior ramus.

Body of the pubis

• Forms anterior and medial parts.
• It has anterior surface and posterior surface .
• The upper border of the body forms a prominent ridge called pubic crest.

Superior ramus

• Attached to upper and lateral part of the body.
• It's lateral extremity takes part in the formation of pubic part of the acetabulum.
• Triangular in cross section has 3 borders and 3 surfaces.
• Anterior border : also called obturator crest.
• Posterior border: sharp, forms pectineal line.
• Inferior border : sharp ; forms the upper margin of the obturator foramen.
• Pectineal surface: lies between obturator crest and pectineal line.
• Pelvic surface : lies between obturator crest and the inferior border.
• A groove runs foreward and downward across it and is called the obturator groove.

Inferior ramus

• Attached to the lower lateral part of the body of the pubis.
• Inferior ramus of the pubis and the ramus of the ischium together called ishiopubic ramus.
• The inferior ramus of the pubis has an anterior surface and a posterior surface.

Acetabulum

• Deep cup like cavity situated on the lateral aspect of the hip bone.
• It forms the hip joint with the head of the femur.
• Directed laterally, downwards and forwards.

• The floor of the acetabulum is partially articular and partially non articular.
• The articular area for the head of the femur is shaped like a horse shoe and is called lunate surface.
• The inner border of the lunate surface forms the margin of the non articular part of the floor which is called acetabular fossa .

Obturator foramen

• Triangular space surrounded by the bodies and Rami of the pubis and ishium.
• The intact body,the foramen is filled by a fibrous sheet called obturator membrane.

Myology
Muscle attached to iliac crest

• External oblique muscle: inserted into the anterior 2/3rd of the outer lip of the ventral segment of the iliac crest.
• Internal oblique muscle : arises from the intermediate area of the ventral segment of the iliac crest .
• Lattisimus dorsi : originates from the outer lip of the iliac crest just behind its highest point.
• Tensor fascia Lata : originates from the anterior part of the outer lip of the iliac crest.
• Transverse abdominis: arises from the anterior 2/3rd of the inner lip of the ventral segment of the iliac crest.
• Quadrature lumborum: arises from the posterior 1/3rd of the inner lip of the ventral segment of the iliac crest.
• Gluteus maximus: arises from the lateral surface of the dorsal segment of the iliac crest .
• Erector spinae: arises from the medial surface of the dorsal segment of the iliac crest.

Muscle attachment to the external aspect of the hip bone.

• Gluteus maximus :arises from the gluteal surface of the ilium behind the posterior gluteal line.
• Gluteus medius: arises from the posterior surface of the ilium between the anterior and posterior gluteal lines.
• Gluteus minimus: arises from the gluteal surface of the ilium behind the anterior and inferior gluteal line.

• Rectus femoris: arises from anterior inferior iliac spine .
• Piriformis : arises from the upper border of the greater sciatic notch near the posterior inferior iliac spine.
• Rectus abdominis: originates from pubic crest.
• Pyramidalis and adductor Longus : originates from the anterior surface of the body of the pubis.
• Gacilis: originates from the anterior surface of the body and the inferior ramus of the pubis and from the ramus of the ischum.
• Adductor brevis : originates from the anterior surface of the body of the pubis and it's inferior ramus, lateral to the origin of the gracilis.
• Obturator externus: originates from the superior and inferior rami of the pubis and forms the ramus of the ischum.
• Adductor Magnus: originates from the lower part of the ischial tuberosity and from the ramus of the ischum.
• Semitendinosus and biceps femoris : originates from the upper medial part of the ischial tuberosity.
• Semimembranosus : originates from the upper lateral part of the ischial tuberosity.
• Quadratus femoris: originates from the femoral surface of the ischum just lateral to the ischial tuberosity.
• Superior gemellus : arises from the dorsal surface of the ischial spine.
• Inferior gamellus: arises from the ischum just above the ischial tuberosity.

Muscle attached to the internal aspect of the hip bone.

• Psoas minor: inserted into pectineal line.
• Iliacus: arises from the upper 2/3rd of the iliac fossa.
• Obturator internus: arises from the pelvic surface of the superior and inferior rami of the pubis and ramus of the ischum , immediately adjoining the obturator foramen and from the pelvic surface of the ischum and of the ilium.
• Levator ani: arises from the pelvic surface of the ischial spine and its most anterior fibres form  the posterior surface of the body of the pubis.
• Coccygeus: arises from the pelvic surface of the ishial spine.

Greater and lesser sciatic foramen.

The greater sciatic foramen transmitted the following structures.

• Piriformis
• The superior and inferior gluteal nerves and vessels.
• Internal pudendal vessels.
• The pudendal and sciatic nerves.
• Posterior cutaneous nerve of the thigh.
• The nerves to obturator internus and quadratus femoris.

Ossification

• Ossifies before birth from three primary centres each for ilium, ishium and pubis.
• The centres appearing in intrauterine life are as follows :.  *For ilium- above the greater sciatic notch in the 8th week.                                                                                              *For ischum- below the acetabulum in the 4th month.

       *For pubis - In the superior ramus in the 4th or 5th month.

• At birth ilium, ishium and pubis are separated by a Y-shaped cartilage present in the region of the acetabulum.
• The three parts fuse completely only after the age of 18 years.
• The inferior ramus of pubis and the ramus of the ischium are at first fused at the age of 7 years.
• The secondary centres appear at the age of 20-25 years.
• Two of them appear at the iliac crest and two if them at acetabular cartilage and occasional centres in the anterior inferior iliac spine and lower part of the acetabulum, the pubic tubercle and the pubic crest.                              

SCAPULA: osteology,myology, ossification, clinical anatomy.

Bone: scapula

• Also called shoulder blade , blade bone.
• Triangular plate of bone lying over the upper ribs in the back. It partly covers the 2nd to 7th rib.

Side determination

• The body of the scapula is flat triangular in shape.
• The upper part of the body is broad(inferior of the triangle).
• The lower part of the body is pointed(apex of the triangle).
• The body has two surfaces the anterior surface is smooth and the posterior surface is rough.
• The posterior surface contain a larger projection called spine.
• The lateral angle is enlarged and bears a large shallow depression called glenoid cavity.

Osteology 

• Scapula consist of

1. Body 
2. Processes
3. Glenoid cavity

Body 

• It is triangular in shape .
• It has two surfaces three borders and three angles.
• The two surfaces are anterior surface and posterior surface.
• The anterior surface also called costal surface is smooth and consist of a fossa called subscapular fossa(fossa gives attachment to subscapular muscle).
• The posterior or dorsal surface of the bone is rough .
• It gives off a large projection called spine of the scapula.
• The spine of the scapula divides the dorsal surface of the scapula into two supraspinous fossa and infraspinous fossa.
• The supraspinous fossa and infraspinous fossa communicate with each other through spinoglenoid notch(located on the lateral side of the notch).
• The three angles of the scapula are superior, interior and lateral angle.
• The superior angle is at the junction between the superior and medial border.
• The inferior angle is at the junction of the medial and lateral borders.
• The lateral angle is at the junction of the medial and the lateral borders.
• It is also called glenoid angle since it carries glenoid fossa .

• The superior border extends between superior angle and the lateral angle .
• It is thin and sharp.
• It is separated from glenoid fossa by the root of the coracoid process.
• A deep suprascapular notch is seen close to the lateral end of the superior border.
• The medial border also called vertebral border.
• It extends from the superior angle to inferior angle.
• It is arched and thicker than the superior border.
• The lateral border also called axillary border.
• It runs from the lateral angle to the inferior angle.
• The part of the body adjoining the lateral border is thickened to form a longitudinal bar of bone  called the strengthening bar.

Glenoid cavity

• Shallow articular socket of the head of the humerus present at the lateral angle of the scapula.
• Below the cavity the lateral border shows  shows a rough riders area called the supraglenoid tubercle.
• The slightly constructed area immediately medial to it constitutes the neck.

Process of scapula

Scapula contains three process

1. Spinous process:

• Large triangular projection from the posterior surface of the body.
• The spine consist of two borders anterior and posterior border.
• The anterior border of the spine is attached to the dorsal surface of the body.
• The posterior border is free and greatly thickened to form crest of the spine.
• It is broad and flat ,has upper lips and lower lips.
• The medial end of the spine lies near the medial border of the scapula and is often referred to as the root of the spine.
• The lateral border is free,broad and forms the medial boundary of the spinoglenoid notch .

2. Acromion process

• Foreward directed lateral end of the spine.
• It has two borders medial and lateral borders and two surfaces upper surface and lower surface.
• The medial border shows the presence of small oval faster for the articulation with the lateral end of the clavicle.

3.coracoid process

• Bent finger shape.
• The root of this process attached to the body of the scapula just above the glenoid cavity.
• The lower part of the process is marked by supraglenoid tubercle.
• The tip of the coracoid process is directed foreward, laterally and little downward.

Myology

Costal surface of the scapula:
Origin:

• Subscapularis arises from the subscapular fossa.

Insertion:

• The serratus anterior is inserted into the costal surface along the medial border.

Dorsal surface of the scapula:
Origin:

• Supraspinatus muscle originates from the supraspinous fossa.
• Infraspinous muscle arise from the infraspinous fossa.
• Triceps (long head) arise from the infraglenoid tubercle.
• Teres minor arise from the upper 2/3rd of the dorsal aspect of lateral border.
• Teres major arise from the lower 1/3rd of the dorsal aspect of the lateral border.
• The lattisimus dorsi arise from the dorsal surface of the inferior angle.

Insertion:

• The levator scapulae is inserted into a narrow strip extending from the superior angle to the level of the root of the spine in the dorsal aspect of the medial border.
• The rhomboideus minor is inserted opposite the root of the spine at the dorsal aspect of the medial border.
• The rhomboideus major is inserted from the root of the spine to the inferior angle in the dorsal aspect of the medial.

Coracoid process:

Origin:

• Biceps brachii (short head) arises from the lateral part of the tip of the coracoid process.
• Biceps brachii(long head) arise from the long head from the supra glenoid tubercle.
• The coracobrachialis arises from the medial part of the tip of the coracoid process.

• The inferior belly of the omohyoid arises from the infraglenoid tubercle.
• The trapezius gets inserted into the upper border of the crest of the spine and into the medial border of the acromion.

Ossification

• Scapula has 1 primary center and 7 seven secondary centres.
• The primary centres appear in the region of the body during 8th week of foetal life.
• Spine: ossified by an extension from the primary center.
• Coracoid process: ossified from a secondary centre that appears in the 1st year.
• The remaining secondary centres appear at puberty ;one for the subcoracoid area including the glenoid,two for the acromion,one for medial border and one for inferior angle.
• All the secondary centres fuse between the age of 18th and 22nd .

Clinical anatomy

• Sprengel's shoulder: condition in which scapula is placed higher than normal (elevated scapula)
• Winging of scapula:(scapula alata) condition in which the medial border of the scapula is lifted off the chest wall; caused due to the paralysis of the serratus anterior muscle.
• Non union of epiphysis: usually involves one of the acromial centres.

BLOOD SUPPLY OF BONE

• A bone receives blood supply from several arteries in the periosteum.
• The shaft of the long bone contains a nutrient foramen through which a large nutrient artery enters the bone.
• The nutrient artery are usually directed away from the growing end of the bone.
• In bones where both ends are growing the nutrient canal is directed away from the actively growing end.

'to the elbow I go , from the knee I flee'

• The shoulder end of the humerus and the wrist end of the radious and ulna grow more than the elbow end.
• So elbow is less growing in nature,thus nutrient artery directed towards the elbow.
• In the lower limb the knee end of both the femur and tibia grow more than hip and ankle.
• Thus knee is actively growing end and the nutrient artery is directed away from knee end.

Main artaries and branches that supply long bones.

• Periosteal branches: 
• enters the shaft at multiple points and supply the compact bone.
• Nutrient artery:
• main artery of the shaft.
• they are the medullary artery that enters the medullary cavity through the nutrient canal and divides into proximal and distal branch .
• Each proximal and distal branch gives out several branches which supply the marrow,the compact bone and the metaphyseal area.
• Branches from adjacent articular arteries: 
• Arteries which anastomose around the joint gives out smaller twigs;these twigs are epiphyseal twigs and metaphyseal twigs and supply to the epiphysis and metaphysis .

CLAVICLE: osteology, myology, ossification, clinical anatomy.

Bone: clavicle.

Features:

• It is also called collar bone.
• It is a long bone that connects upper limb to the shaft.
• Parts:it has a shaft and two ends.
•  The medial end articulates with the sternum called sternal end and the lateral end which articulates with the acromion process is called acromial end.
• Location:anterosuperior aspect of thorax.
• The bone placed horizontally in the body thus it prevent shoulder from falling forward.

Side determination:

• The medial side of the shaft is round and lateral part is flattened.
•  Medial end of the clavicle is round and the lateral end is oval in shape.
•  Medial part of the shaft is convex forward and lateral part is concave forward.
• The inferior aspect of the shaft has a shallow groove and rough area on the medial end.

 Osteology:

• The clavicle consist of a shaft and two ends .
• The medial end of the clavicle is round in shape and articulates with the manubrium of the clavicle (sternoclavicular joint).
• The lateral end of the clavicle is oval in shape and articulates with the acromion process of the scapula (acromioclavicular joint).
• The shaft is divided into two medial 2/3rd and lateral 1/3rd.
• The medial 2/3rd of the clavicle is cylindrical in shape and is convex forward.
• It has four surfaces anterior, posterior, superior and inferior.
• The middle of the inferior surface present longitudinal groove called subclavian groove.
• The lateral 1/3rd is flat .
• It has two surfaces superior and inferior.
• The inferior surface shows a prominent thickening near posterior border called conoid tubercle.
• Lateral to the tubercle is a rough ridge that runs obliquely uptown the lateral end of the bone called trapezoid line.
• It has two borders anterior and posterior border.
• The anterior border is concave and shows a small thickened area called deltoid tubercle.

Myology:

• Medial 2/3rd of the shaft:
• Pectoralis major muscle arise from the anterior surface of medial happy of the shaft.
• The clavicular head of the sternocleidomastoid muscle arises from the medial part of the upper surface of the medial 2/3rd of the shaft.
• Lateral 1/3rd of the shaft:
• Trapezius is inserted into the posterior border of the lateral 1/3rd of the shaft.
• The lateral part of the sternohyoid arises from the lower part of posterior surface.
• Deltoid arise from the anterior border of the lateral 1/3rd of the shaft.
• Subclavius is inserted into the groove  on the inferior surface of the shaft.

Special features of the clavicle.

1. It is the first bone to ossify and last bone to complete ossification.
2. It is the only long bone which lies horizontally.
3. It doesn't possess a medullary cavity.
4. It is the only long bone that ossified in membrane .
5. It is the only bone that has two primary centres.

Ossification

• Clavicle is the first bone to start ossification.
• Most of the part of the clavicle formed by intramembraneous ossification.
• The sternal and acromial ends are performed in cartilage.
• During 5th-6th week of foetal life two primary centres appear in the shaft later they fuse.
• The sternal end ossified from the secondary centres that appears tween 15 and 20 years of age and fuses with the shaft at the age of 25.

Clinical anatomy

• Fracture of the clavicle:
• Caused by indirect violence.
• Affects the weakest point of the bone (between middle 1/3rd and lateral 1/3rd).
• The thin slender clavicle of the neonate can be fractured during birth  it is called greenstick fracture.

• Failure of fusion of ossification center:
• The medial and lateral part of the bone remain separate.
• It is a congenital deformity.

Special features of clavicle

• The right clavicle is usually shorter than the left clavicle.
• In animals whose upper limb are used for the weight bearing purpose eg:tiger , clavicle is absent or rudimentary.
• Clavicle helps in the transmittionof shock to the trunk from the upper limb.

Bone architecture: Terminologies

Compact bone

• They are found on the outer part (wall) of the shafts of long bones.
• They are also called dense bones or cortical bones.
• Trabeculae in compact bones are thick and densely packed.

Spongy bone

• They are also called cancellous bone .
• They can be found in the ends of the long bone.

• The spongy bone at the bone ends is covered by a thin layer of compact bone.
• The trabeculae are thin and spread out in a mesh work.

Harvesian canal

• They are the microscopic canal seen in the cortical bones.
• These allows the blood vessels and nerves to travel through them.

Volkmann's canal

• They are also called perforating channels.
• They are small channels that runs between two harvesian canals thereby connects two osteon.
• They transmitted blood vessels from periosteum into bones.
• They provide energy and nourishing elements for osteon.

Osteoprogenital cells

• They are the stem cells that proliferate and convert into osteoblast.

Osteoblast

• They are the bone producing cells .

Osteocytes

• They are the cells of the mature bones.
• They are the osteoblast trapped in matrix that they secret.
• They are found in the lacunae.

Osteoclast

• These are the bone removing cells.

Lacunae

• Small cavity or gap between the two lamellae of the bone.
• It contains osteocytes.

Osteon

• Structural unit of compact bone.
• It is cylindrical in shape.
• Also called harvesian system.

Lamellae

• They are the layers of the compact bone tissue.
• The concentric layers of bone tissue that surrounds the harvesian canal is called concentric lamellae.
• They keeps the adjacent cells together.
• The irregular shaped bone tissue seen between the two osteons is called interstitial lamellae.
• The bone tissue that runs parallel to the periosteum is called circumferential lamellae.

Canaliculi

• Channels connecting the lacunae .
• Helps in the conduction of nutrients to osteocytes and waste products away from osteocytes.

BONES:basic information.

What is a bone?

• It is an osseous tissue (also called bone tissue)that later turns into bone.
• It is a type of dense connective tissue with great strength and resilience.
• It consists of cells,fibres and a matrix.
• Matrix is extra cellular and has a calcium deposition in it.
• The calcium salts forms 2/3rd of the bone and the remaining part forms 1/3rd of the connective tissue.
• The calcification provide strength to the bone tissue.
• The presence of fibre gives some amount of elasticity to the tissue.

What are the functions of the bone?

• Bone gives shape and support to the body and resist any form of stress.
• They provide surface for the attachment of muscle ,tendonand ligamens.
• They serve as lever for muscle action.
• The skull, vertebral column and thoracic cage protect brain, spinal cord,thorax and some abdominal viscera.
• Bone marrow inside the bones manufacturers blood cells.
• Bones store about 97% of body calcium and phosphorus.
• Bone marrow contains reticuloendothelial cells which are phagocytic in nature and take part in immune response of the body.
• The larger paranasal air sinuses example ethmoidal sinuses affect the timber of the voice.

Architecture of bones

• All bones have an outer layer of compact bone and the interior covered by cancellous bone.

Compact bone

• They are hard and forms the outer layer of bone.
• It consists of longitudinal running canal called harvesian canal.
• Harvesian canal surrounded by lamellae to form osteon or harvesian system.

Cancellous bone

• Meshwork of tiny rods or plates of bone and contain numerous spaces ; appearance resembles that of sponge.
• They are found on the interior of the bone.
• The spongy bone at the bone ends is covered by a thin layer of compact bone.
• Trabeculae are thin and spread out in a meshwork.

• The newly formed bones are usually cancellous bone and later they are converted into compact bone.
• The bone is covered by periosteum.
• The articular surface of the bone is covered by articular cartilage.
• The marrow cavity of the bone and space between the spongy bone are filled by highly vascular tissue called bone marrow.
• At both the ends the marrow is red in colour.
• The yellow marrow is found in the shaft of the bones in the adult.

Parts of a bone

   A young long bone consist of

• Diaphysis 
• Epiphysis
• Epiphyseal cartilage
• Metaphysis

Diaphysis

• It ossified from primary ossification center to form the shaft of the bone.
• Composed of thick compact bone that covers the thin spongy bone which encloses marrow cavity.

Epiphysis

• Part of the bone that ossified from secondary centres.
• It forms the ends of the long bone.

Epiphyseal cartilage

• Plate of cartilage seen between epiphysis and metaphysis of a young growing bone.
• When the bone achieves full length the epiphyseal cartilage replaced by the bone , thus further growth stops.

Metaphysis

• The end of the diaphysis adjuscent to the epiphyseal cartilage .
•  Actively growing area of the long bone.