ANATOMY OF THE CRANIAL BONES

The skull consists of 8 cranial bones and 14 facial bones. The eight bones of the cranium articulate firmly with one another to enclose and protect the brain and sensory organs. The 14 facial bones form the framework for the facial region and support the teeth.The facial bones,with the exception of the mandible (“jawbone”),are also firmly interlocked with one another and the cranial bones.The skull has several cavities. The cranial cavity is the largest. The nasal cavity is formed by both cranial and facial bones and is partitioned into two chambers, or nasal fossae, by a nasal septum of bone and cartilage. Four sets of paranasal sinuses, located within the bones surrounding the nasal area, communicate via ducts into the nasal cavity. Middle- and inner-ear cavities are positioned inferior to the cranial cavity and house the organs of

hearing and balance. The two orbits for the eyeballs are formed by facial and cranial bones. The oral, or buccal cavity (mouth), which is only partially formed by bone, is completely within the facial region.

 During fetal development and infancy, the bones of the cranium are separated by fibrous unions. There are also six large areas of connective tissue membrane that cover the gaps between the developing bones. These membranous sheets are called fontanelles, meaning “little fountains.” The name derives from the fact that a baby’s pulse can be felt surging in these “soft spots” on the skull. The fontanelles permit the skull to undergo changes in shape, called molding, during parturition (childbirth), and they accommodate the rapid growth of the brain during infancy. Ossification of the fontanelles is normally complete by 20 to 24 months of age. The following fontanelles are present:

1. Anterior (frontal) fontanelle,fonticulus anterior. The anterior fontanel is diamond-shaped and is the most prominent. It is located

on the anteromedian portion of the skull.

2. Posterior (occipital) fontanelle,fonticulus posterior. The posterior fontanel is positioned at the back of the skull on the median line. It is also diamond-shaped, but smaller than the anterior

fontanelle.

3. Anterolateral (sphenoid) fontanelles,fonticulus sphenoidalis. The paired anterolateral fontanels are found on both sides of the skull, directly lateral to the anterior fontanelle. They are relatively small and irregularly shaped.

4. Posterolateral (mastoid) fontanelles,fonticulus mastoideus. The paired posterolateral fontanelles, also irregularly shaped, are located on the posterolateral sides of the skull.

    A prominent sagittal suture extends the anteroposterior median length of the skull between the anterior and posterior fontanelles. A coronal suture extends from the anterior fontanel to the anterolateral fontanel. A lambdoid suture extends from the posterior fontanel to the posterolateral fontanelle. A squamous suture connects the posterolateral fontanelle to the anterolateral fontanelle.

Clinical application:During normal childbirth, the fetal skull comes under tremendous pressure. Bones may even shift, altering the shape of the skull. A common occurrence during molding of the fetal skull is for the occipital bone to be repositioned under the two parietal bones. In addition, one parietal bone may shift so as to overlap the other. This makes delivery easier for the mother. If a baby is born breech (buttocks first), these shifts do not occur. Delivery becomes much more difficult, often requiring the use of forceps.

                             CRANIAL BONES

 The cranial bones enclose and protect the brain and associated sensory organs. They consist of one frontal, two parietals, two temporals, one occipital, one sphenoid, and one ethmoid.

                             THE FRONTAL BONE

 The frontal bone forms the anterior roof of the cranium,the forehead,the roof of the nasal cavity and the superior arches of the orbits,which contain the eyeballs.  The frontal bone develops in two halves that grow together.

Generally,they are completely fused by age 5 or 6. A suture sometimes persists between these two portions and is referred to as a metopic suture.This makes them unpaired.

   The frontal bone has three parts:

1.Squamous part,squama frontalis:a vertical convex part of the bone,which consists of the external,internal and temporal surfaces. The squamous part bears the following structures:

• Frontal tuber,tuber frontale: a paired,most prominent elevation of the squamous part.
• Superciliary arch,arcus: a paired, prominent, rounded arch situated below and medial to the frontal tuber.
• Glabella,glabella: an unpaired area between the superciliary arches and above the base of the nose.
• Supra-orbital margin,margo supraorbitalis: a paired,prominent area on the border with the orbital part.
• Supra-orbital notch,incisura supraorbitalis:resides medially on the supra-orbital margin .
• The frontal notch,incisura frontalis:a shallow notch that resides medially from the supra-orbital notch.
• Zygomatic process,processus zygomaticus: a directed downward,lateral portion of the supra-orbital margin.
• Temporal line,linea temporalis: arches upward and backward from the zygomatic process.
• Frontal crest,crista frontalis: unpaired, located in the middle of the of the inferior portion of the bone.

2.Orbital part,pars orbitalis:o horizontal part,which contains the orbital and cerebral surfaces.It bears the following parts:

• Fossa for lacrimal gland,fossa glandulae lacrimalis:resides near the zygomatic process in the upper,lateral angle of the orbit.
• Trochlear fovea,fovea trochlearis:a small depression located medially.
• Trochlear spine,spina trochlearis:lies near the trochlear fovea.
• Cerebral yokes,juga cerebralia:also reside on the cerebral surface between the impressions for cerebral gyri.

3.Nasal part,pars nasalis:an unpaired part located in the middle between two orbital parts surrounding the ethmoidal notch.It also has the following parts:

• Nasal spine,spina nasalis which lies in the middle.
• opening of the frontal sinus,apertura sinus frontalis: a paired orifice leading into the frontal sinus.
• Ethmoidal notch,incisura ethmoidalis resides in the middle and separates orbital parts.
• Frontal sinus,sinus frontalis: a sizeable air cavity within the lower portion of the squamous part.The frontal sinus is separated by a bony septum into two cavities, which communicate with the nasal cavity.
  

                                                     


                                                        THE PARIETAL BONE

 The two parietal bones form the upper sides and roof of the cranium.The coronal suture separates the 
frontal bone from the parietal bones, and the sagittal suture along the superior midline separates the right and left parietals from each other.

                  Borders of parietal bone

• sagittal border,margo sagittalis: the upper margin of the bone,which articulates with the opposite parietal bone to form the sagittal suture.
• Frontal border,margo frontalis: a directed forward border,which articulates with frontal bone to form the coronal suture.
• Occipital border,margo occipitalis: a directed backward border, which articulates with the occipital bone forming the lambdoid suture.
• Squamous border,margo squamosus: the fourth,oblique,directed downward border of the parietal bone. It overlaps with the squamous part of the temporal bone.

                            Angles of the parietal bone

• Frontal angle,angulus frontalis the anterior,upper,straight angle,which articulates with the frontal bone.
• Sphenoidal angle,angulus sphenoidalis the anterior,lower,sharper angle,which articulates with the greater wing of the sphenoid bone.
• Occipital angle,angulus occipitalis the posterior,lower,rounded angle,which articulates with the occipital bone.
• Mastoid angle,angulus mastoideus: the posterior,upper,blunt angle,which articulates with the mastoid process of the temporal bone.
  

                          

                               TEMPORAL BONE

The two temporal bones form the lower sides of the cranium. Each temporal bone is joined to its adjacent parietal bone by the squamous suture. Structurally, each temporal bone has four parts.

1. Squamous part,pars squamosa. The squamous part is the flattened plate of bone at the sides of the skull. Projecting forward is a zygomatic  process that forms the posterior portion of the zygomatic arch. On the inferior surface of the squamous part is the cuplike mandibular fossa, which forms a joint with the condyle of the mandible. This articulation is the temporomandibular joint.

2.Tympanic part,pars tympanica. The tympanic part of the temporal bone contains the external acoustic meatus, or ear canal, which is posterior to the mandibular fossa. A thin, pointed styloid process projects inferiorly from the tympanic part.External acoustic opening which resides in the centre where the parts of the temporal bone articulate.A tympanosquamous fissure separates the tympanic part from the squamous part.It is split into two parts by the plate of the petrous part:petrosquamous fissure and petrotympanic fissure.The tympanomastoid fissure separates the tympanic part from the mastoid process.

                  The Tympanic Cavity,cavitas tympani

The tympanic cavity is the air filled cavity of irregular shape situated within the petrous part of the temporal bone.It is invested with the mucous membrane.

   walls of the tympanic cavity:The tympanic cavity has six walls,namely;

• The tegmental wall,paries tegmentalis is the wall related tot he tegmen tympani.
• The jugular wall,paries jugularies related to the jugular fossa.
• The labyrinthine wall,paries labyrinthicum is the medial wall related to the bony labyrinth.
• The membranous wall,paries membranaceus is a small lateral wall scaled with the tympanic membrane.
• The carotid wall,paries caroticus is the wall related to the carotid canal.The tympanic opening of the auditory tube and the opening of the caroticotympanic caniculi can be distinguished on this wall.
• The mastoid wall,paries mastoideus is the posterior wall related to the mastoid process of the temporal bone.
  

3. Mastoid part,pars mastoidea. The mastoid process, a rounded projection posterior to the external acoustic meatus, accounts for the mass of the mastoid part. The mastoid foramen  is directly posterior to the mastoid process. The stylomastoid foramen, located between the mastoid and styloid processes , provides the passage for part of the facial nerve.

4. Petrous part(pyramid),pars tetrosa. The petrous part can be seen in the floor of the cranium. The structures of the middle ear and inner ear are housed in this dense part of the temporal bone. The carotid canal and the jugular foramen border on the medial side of the petrous part at the junction of the temporal and occipital bones. The carotid canal allows blood into the brain via the internal carotid artery, and the jugular foramen lets blood drain from the brain via the internal jugular vein. Three cranial nerves also pass through the jugular foramen.The following surfaces are distinguished in the pyramid:

• Anterior surface,facies anterior: faces forward,upward and laterally.
• Posterior surface,facies posterior:faces backward and medially.
• Inferior surface,facies inferior:faces downward towards the area of the external surface of the cranial base.

The three surfaces of the petrous part are bounded by three borders:

• Anterior border of the petrous part,margo anterior partis pertrosae:the shortest border,which connects the squama with the apex of the pyramid.
• Superior border of the petrous part,margo superior patris pertrosae:saparates the anterior and posterior surfaces of the pyramid.
• Posterior border of the petrous part,margo posterior patris petrosae:separates the posterior and inferior surfaces of the pyramid.
  

              Canals of the temporal bone

• Facial canal,canalis nervi facialis:It transmits the facial nerve.The facial canal begins at the bottom of the internal acoustic meatus and ends in the stylomastoiss foramen.
• Canal for chorda tympani,canaliculis chordae tympani: It gives passage to a thin nerve(chorda tympani).
• Carotid canal,canalis caroticus: It transmits the internal carotid artery.The carotid canal begins on the inferior surface of the pyramid.
• Caroticotympanic canal,canaliculus caroticotympanici:begin on the posterior of the carotid canal and enter the tympanic cavity penetrating its anterior wall.Its gives passage to the corresponding nerves and vessels.
• Musculotubal canal,canalis musculotubarius:It exits the tympanic cavity.The musculotubal canal resides in the angle between the anterior margin of the pyramid and the squamous part of the temporal bone. A horizontal septum divides the musculotubal canal into two:
• Canal for tensor tympani,semicanalis m. tensor tympani,situated above.
• Canal for auditory tube,semicanalis tubae auditivae,resides below the previous canal and transmits the auditory(Eustachian) tube,which establishes the communication between the tympanic cavity and the nasal part of the pharynx. 
• Tympanic canal,canaliculis tympanicus:begins on the inferior surface of the pyramid in the petrous fossula and runs vertically upward penetrating the inferior wall of the tympanic cavity.It houses the tympanic nerve.
• Mastoid canal,canaliculis mastoideus:begins at the bottom of the jugular fossa,crosses the facial canal in its lower portion and opens into the tympanomastoid fissure.It gives passage to the auricular branch of the vagus nerve.

    Clinical application:The mastoid process of the temporal bone can be easily palpated as a bony knob immediately behind the earlobe. This process contains a number of small air-filled spaces called mastoid cells that can become infected in mastoiditis, as a result, for example,of a prolonged middle-ear infection.

                               OCCIPITAL BONE

The occipital bone forms the posterior and most of the base of the skull. It articulates with the parietal bones at the lambdoid suture. The foramen magnum is the large hole in the occipital bone through which the spinal cord passes to attach to the brain stem. On each side of the foramen magnum are the occipital condyles, which articulate with the first vertebra (the atlas) of the vertebral column.  At the anterolateral edge of the occipital condyle is the hypoglossal canal, through which the hypoglossal nerve passes. A condyloid  canal lies posterior to the occipital condyle . The external occipital protuberance is a prominent posterior projection on the occipital bone that can be felt as a definite bump just under the skin. The superior nuchal  line is a ridge of bone extending laterally from the occipital protuberance to the mastoid part of the temporal bone. Sutural bones are small clusters of irregularly shaped bones that frequently occur along the lambdoid suture.

 The occipital bone has the following parts:

• Basilar part,pars basilaris, an unpaired portion located in front of the foramen magnum.
• Lateral part,pars lateralis, a paired part situated on each side of the foramen magnum.
• Squamous part,squama occipitalis, an unpaired larger portion of the bone located the foramen.

 

                                     

                                        SPHENOID BONE

 The sphenoid bone forms part of the anterior base of the cranium. This bone has a somewhat mothlike shape. It consists of a body and laterally projecting greater and lesser wings that form part of the orbit. The wedgelike body contains the sphenoidal sinuses and a prominent saddlelike depression, the sella turcica. Commonly called “Turk’s saddle,” the sella turcica houses the pituitary gland. A pair of pterygoid processes project inferiorly from the sphenoid bone and help form the lateral walls of the nasal cavity.

Several foramina are associated with the sphenoid bone:

1. The optic canal is a large opening through the lesser wing into the back of the orbit that provides passage for the optic nerve and the ophthalmic artery.

2. The superior orbital fissure is a triangular opening between the wings of the sphenoid bone that provides passage for the ophthalmic nerve, a branch of the trigeminal nerve, and for the oculomotor, trochlear, and abducens nerves.

3. The foramen ovale is an opening at the base of the lateral pterygoid plate,through which the mandibular nerve passes.

4. The foramen spinosum is a small opening at the posterior angle of the sphenoid bone that provides passage for the middle meningeal vessels.

5. The foramen lacerum is an opening between the sphenoid and the petrous part of the temporal bone, through which the internal carotid artery and the meningeal branch of the ascending pharyngeal artery pass.

6. The foramen rotundum is an opening just posterior to the superior orbital fissure, at the junction of the anterior and medial portions of the sphenoid bone. The maxillary nerve passes through this foramen.

Clinical application:Located on the inferior side of the cranium, the sphenoid bone would seem to be well protected from trauma. Actually, just the opposite is true—and in fact the sphenoid is the most frequently fractured bone of the cranium. It has several broad, thin, platelike extensions that are perforated by numerous foramina. A blow to almost any portion of the skull causes the buoyed, fluid-filled brain to rebound against the vulnerable sphenoid bone, often causing it to fracture.

                                 THE ETHMOID BONE

The ethmoid bone is located in the anterior portion of the floor of the cranium between the orbits, where it forms the roof of

the nasal cavity. An inferior projection of the ethmoid bone, called the perpendicular plate, forms the superior part of the nasal septum that separates the nasal cavity into two chambers. Each chamber of the nasal cavity is referred to as a nasal fossa. Flanking the perpendicular plate on each side is a large but delicate mass of bone riddled with ethmoidal air cells, collectively constituting the ethmoid sinus. A spine of the perpendicular plate, the crista galli,projects superiorly into the cranial cavity and serves as an attachment for the meninges covering the brain. On both lateral walls of the nasal cavity are two scroll-shaped plates of the ethmoid

bone, the superior and middle nasal conchae,also known as turbinates. At right angles to the perpendicular plate, within the floor of the cranium, is the cribriform plate, which has numerous cribriform foramina for the passage of olfactory nerves from the epithelial lining of the nasal cavity. 

Clinical application:The moist,warm vascular lining within the nasal cavity is susceptible to infections,particularly if a person is not in good health. Infections of the nasal cavity can spread to several surrounding areas. The paranasal sinuses connect to the nasal cavity and are especially prone to infection. The eyes may become reddened and swollen during a nasal infection because of the connection of the nasolacrimal duct,through which tears drain from the anterior surface of the eye to the nasal cavity. Organisms may spread via the auditory tube from the nasopharynx to the middle ear. With prolonged nasal infections,organisms may even ascend to the meninges covering the brain via the sheaths of the olfactory nerves and pass through the cribriform plate to cause meningitis.

                                   Kamal Umar Labaran

                     Donetsk National Medical University.

THE SKELETON OF THE LOWER LIMB

  The skeleton of the lower limb is divided  into two parts; the pelvic girdle and the free part of the lower limb. The pelvic girdle consists of the hip bone(os coxae). The free part of the lower limb is further divided into the thigh(femur), foreleg(crus) and the skeleton of the foot(ossa pedis).

                                                                        PELVIC GIRDLE

   The Hip Bone:  The hip bone,os coxae  actually consists of three separate bones: the ilium, the ischium, and the pubis.These bones are fused together in the adult. On the lateral surface of the os coxae, where the three bones ossify, is a large circular depression, the acetabulum  which receives the head of the femur. Although both ossa coxae are single bones in the adult, the three components of each one are considered separately for descriptive purpose.

                                    The Ilium

 The ilium is the uppermost and largest of the three pelvic bones.

It has a crest and four angles, or spines—important surface landmarks that serve for muscle attachment.The body of ilium,corpus ossis ilii which is the lower expanded portion,which belongs to the acetabulum.Wing of ilium,ala ossis ilii is the upper,flat,expanded portion of the bone. The iliac crest,crista iliaca forms the prominence of the hip. This crest terminates anteriorly as the anterior superior iliac spine,spina iliaca anterior superior. Just below this spine is the anterior inferior iliac spine,spina iliaca anterior inferior. The posterior termination of the iliac crest is the posterior superior iliac spine,spina iliaca posterior superior and just below this is the posterior inferior iliac spine,spina iliaca posterior inferior. Below the posterior inferior iliac spine is the greater sciatic notch,incisura ischiadicum major through which the sciatic nerve passes. On the medial surface of the ilium is the roughened auricular surface,facies auricularies which articulates with the sacrum. The iliac fossa,fossa iliaca is the smooth, concave surface on the anterior portion of the ilium. The iliacus muscle originates from this fossa. The iliac tuberosity,tuberositas iliaca for the attachment of the sacroiliac ligament, is positioned posterior to the iliac fossa. Three roughened ridges are present on the gluteal surface of the posterior aspect of the ilium. These ridges, which serve to attach the gluteal muscles, are the inferior, anterior, and posterior gluteal lines(lineae gluteae inferior,anterior et posterior).

                             

                                     The Ischium

  The ischium is the posteroinferior bone of the os coxae. This bone has several distinguishing features:The body of ischium,corpus ossis ischii is the upper thick segment of the bone,which reaches the acetabulum;the body lies posterior to the obturator foramen,foramen obturatum. The spine of the ischium,spina ischiadica is the projection immediately posterior and inferior to the greater sciatic notch of the ilium. Inferior to this spine is the lesser sciatic notch,incisura ischiadica minor. The ischial tuberosity,tuber ischiadicum is the bony projection that supports the weight of the body in the sitting position. A deep acetabular notch,incisura acetabuli is present on the inferior portion of the acetabulum. The large obturator foramen is formed by the inferior ramus of the ischium,ramus ossis ischii inferior, together with the pubis. The obturator foramen is covered by the obturator membrane, to which several muscles attach.

               

                                   The Pubis

The pubis is the anterior bone of the os coxae. It consists of a superior ramus,ramus superior and an inferior ramus,ramus inferior that support the body of the pubis. The body of the pubis ,corpus ossis pubis contributes to the formation of the symphysis pubis—the joint between the two ossa coxae. At the lateral end of the anterior border of the body is the pubic tubercle,tuberculum pubicum one of the attachments for the inguinal ligament.The symphysial surface,facies symphysialis resides medially in the area of fusion of the superior and inferior rami.

                                    
     Clinical application:The structure of the human pelvis, in its attachment to the vertebral column, permits an upright posture and locomotion on two appendages (bipedal locomotion). An upright posture may cause problems, however. The sacroiliac joint may weaken with age, causing lower back pains. The weight of the viscera may weaken the walls of the lower abdominal area and cause hernias. Some of the problems of childbirth are related to the structure of the mother’s pelvis. Finally, the hip joint tends to deteriorate with age, so that many elderly people suffer from degenerative arthritis (osteoarthrosis).
             Sex-Related Differences in the Pelvis
Structural differences between the pelvis of an adult male and
that of an adult female reflect the female’s role in pregnancy and parturition.In females, the pelvis is shorter and broader whiles in male,it is taller,heavier and thicker.In a vaginal delivery, a baby must pass through its mother’s lesser pelvis. Pelvimetry is the measurement of the dimensions of the pelvis—especially of the adult female pelvis—to determine whether a cesarean section might be necessary. Diameters may be determined by vaginal palpation or by sonographic images.The pelvic brim is wider in females than in males.The pubic angle in male is an average of 75 degrees and 80-100 in female.

How to know right or left  hip bone

• Place the iliac crest superiorly with the ischium placed  inferiorly.                                                                       
• The iliac fossa should be anteriorly placed.                   
•        position the auricular surface medially. These will help you know if the bone is left or right.                                   

FREE PART OF THE LOWER LIMB

The Femur: The “thighbone” is the longest, heaviest and strongest

bone in the body. The proximal rounded head,caput femoris of the

femur articulates with the acetabulum of the os coxae. A roughened shallow pit in the head of femur, the fovea capitis femoris, is present in the lower center of the head of the femur. The fovea capitis femoris provides the point of attachment for the ligamentum

capitis femoris, which helps to support the head of the femur against the acetabulum. It also provides the site for the entry of an artery into the head of the femur. The constricted region supporting the head is called the neck,collum femoris and is a common site for fractures in the elderly.The body of the femur has a slight medial curve to bring the knee joint in line with the body’s plane of gravity. The degree of curvature is greater in the female because of the wider pelvis. The body of the femur has several distinguishing features for muscle attachment. On the proximolateral side of the body is the greater trochanter,trochanter major and on the medial side is the lesser trochanter,trochanter minor. On the anterior side, between the trochanters, is the intertrochanteric line,linea intertrochanterica. On the posterior side, between the trochanters, is the intertrochanteric crest,crista intertrochanterica. The linea aspera is a roughened vertical ridge on the posterior surface of the body of the femur.

  The distal end(epiphysis) of the femur is expanded for articulation with the tibia. The medial and lateral condyles(condylus medialis et lateralis) are the articular processes for this joint. The shallow depression between the condyles on the posterior aspect is called the intercondylar fossa,fossa intercondylaris. The patellar surface(facies patellaris) is located between the condyles on the anterior side. Above the condyles on the lateral and medial sides are the epicondyles,epicondylus lateralis et medialis which serve for ligament and tendon attachment.

       To know left or right femur,

• Identify the head of the femur and place it medially.
• place the intercondylar fossa posteriorly. These will help to determine left and right femur.

  The Patella:The patella ( “kneecap”) is a large, triangular sesamoid bone positioned on the anterior side of the distal femur. It develops in response to strain in the patellar tendon. It has a broad base and an inferiorly pointed apex. Articular facets on the articular surface of the patella articulate with the medial and lateral condyles of the femur.

 The functions of the patella are to protect the knee joint

and to strengthen the patellar tendon. It also increases the leverage

of the quadriceps femoris muscle as it extends (straightens)

the knee joint.

   Clinical application: The patella can be fractured by a direct blow. It usually does not fragment, however, because it is confined within the patellar tendon. Dislocations of the patella may result from injury or from underdevelopment of the lateral condyle of the femur.

     The Tibia:The tibia ( “shinbone”) is situated on the medial side of the foreleg.It articulates proximally with the femur at the knee joint and distally with the talus of the ankle. It also articulates both proximally and distally with the fibula. Two slightly concave surfaces on the proximal end of the tibia, the medial and lateral condyles, condylus medialis et lateralis  articulate with the condyles of the femur. The condyles are separated by a slight upward projection called the intercondylar eminence,eminentia intercondylaris which provides attachment for the cruciate ligaments of the knee joint. The tibial tuberosity, for attachment of the patellar ligament, is located on the proximoanterior part of the

body of the tibia. The anterior border,margo anterior commonly called the “shin,” is a sharp ridge along the anterior surface of the body. The medial malleolus,malleolus medialis is a prominent medial knob of bone located on the distomedial end of the tibia. A fibular notch,incisura fibularis for articulation with the fibula, is located on the distolateral end. In that the tibia is the weight-bearing bone of the leg, it is much larger than the fibula.

   

      Fibula: The fibula is a long, slender bone that is more important

for muscle attachment than for support. The head,caput fibulae of the fibula articulates with the proximolateral end of the tibia.The apex of head,apex capitis fibulae is directed upward.The distal end (distal epiphysis)has a prominent knob called the lateral malleolus, malleolus lateralis.It bears the articular surface for the talus.

  Clinical application: The lateral and medial malleoli are positioned on either side of the talus and help to stabilize the ankle joint. Both processes can be seen as prominent surface features and are easily palpated. Fractures to the fibula above the lateral malleolus are common in skiers. Clinically referred to as Pott’s fracture, it is caused by a shearing force acting at a vulnerable spot on the leg.

                                  BONES OF THE FOOT

   The foot contains 26 bones, grouped into the tarsus, metatarsus,

and phalanges. Although similar to the bones of the

hand, the bones of the foot have distinct structural differences in

order to support the weight of the body and provide leverage and

mobility during walking.

   

  Tarsus:There are seven tarsal bones. The most superior in position is the talus, which articulates with the tibia and fibula to form the

ankle joint. The calcaneus is the largest of the tarsal bones and provides skeletal support for the heel of the foot. It has a large posterior extension, called the tuberosity of the calcaneus, for the attachment of the calf muscles. Anterior to the talus is the block-shaped navicular bone. The remaining four tarsal bones form a distal series that articulate with the metatarsal bones. They are, from the medial to the lateral side, the medial, intermediate, and lateral cuneiform bones and the cuboid bone.

 Metatarsus:The metatarsal bones and phalanges are similar in name and number to the metacarpals and phalanges of the hand. They differ in shape, however, because of their load-bearing role.

The metatarsal bones are numbered I to V, starting with the

medial (great toe) side of the foot. The first metatarsal bone is

larger than the others because of its major role in supporting

body weight.

 The metatarsal bones each have a base, body, and head. The proximal bases of the first, second, and third metatarsals articulate proximally with the cuneiform bones. The heads of the metatarsals articulate distally with the proximal phalanges. The proximal joints are called tarsometatarsal joints, and the distal joints are called metatarsophalangeal joints. The ball of the foot is formed by the heads of the first two metatarsal bones.

   The phalanges:The 14 phalanges are the skeletal elements of the toes. As with the fingers of the hand, the phalanges of the toes are arranged in a proximal row, a middle row, and a distal row. The great toe, or hallux (adjective, hallucis) has only a proximal and a distal phalanx.The 14 phalanges are the skeletal elements of the toes. As with the fingers of the hand, the phalanges of the toes are arranged in a proximal row, a middle row, and a distal row. The great toe, or hallux (adjective, hallucis) has only a proximal and a distal phalanx.

Arches of the Foot

The foot has two arches. They are formed by the structure and arrangement of the bones and maintained by ligaments and tendons. The arches are not rigid; they “give” when weight is placed on the foot, and they spring back as the weight is lifted.

 The longitudinal arch is divided into medial and lateral parts. The medial part is the more elevated of the two. The talus is keystone of the medial part, which originates at the calcaneus, rises at the talus, and descends to the first three metatarsal bones. The shallower lateral part consists of the calcaneus, cuboid, and fourth and fifth metatarsal bones. The cuboid is the keystone bone of this arch.

 The transverse arch extends across the width of the foot and is formed by the calcaneus, navicular, and cuboid bones posteriorly and the bases of all five metatarsal bones anteriorly. A weakening of the ligaments and tendons of the foot may cause the arches to “fall”—a condition known as pes planus, or, more commonly, “flatfoot.

Kamal Umar Labaran(med)

Donetsk National Medical University.

THE SKELETON OF THE UPPER LIMB

  The skeleton of the upper limb is divided into two parts - the pectoral girdle and the freely movable part of the upper limb: pectoral girdle, includes the clavicle and the scapula, with the help of which the free part of the upper limb articulates with the torso. free part of the upper limb,includes bones of the arm (ossa brachii), bones of the forearm (ossa antebrachii) and bones of the hand(ossa manus). 

                                       PECTORAL GIRDLE

 The scapula:The scapula (“shoulder blade”) is a large, triangular flat bone on the posterior side of the rib cage, overlying ribs 2 through 7. The spine of the scapula,spina scapulae is a prominent diagonal bony ridge seen on the posterior surface. The spine strengthens the scapula, making it more resistant to bending. Above the spine is the supraspinous fossa,fossa supraspinata and below the spine is the infraspinous fossa,fossa infraspinata. The spine broadens toward the shoulder as the acromion. This process serves for the attachment of several muscles, as well as for articulation with the clavicle. Inferior to the acromion is a shallow depression, the glenoid cavity,cavitas glenoidalis into which the head of the humerus fits. The coracoid process,processus coracoideus is a thick upward projection lying superior and anterior to the glenoid cavity. The scapula has anterior(costal surface) and posterior surfaces.The anterior surface faces the ribs.On the anterior surface of the scapula is a slightly concave area known as the subscapular fossa. The posterior surface faces the skin of the back.

                 Angles of the scapula 

•  Acromial angle,angulus acromialis; sharp bend at the site where the spine of the scapula becomes continuous with the lateral margin of the acromion. 
• Inferior angle,angulus inferior; lower angle of the scapula.
•  Lateral angle,angulus lateralis; lateral angle of the scapula bearing the glenoid cavity. 
• Superior angle,angulus superior ;upper medial angle of the scapula . 

                   Margins of the scapula 

•  Medial margin,margo medialis; border of the scapula facing the vertebral column. 
• Lateral margin,margo lateralis; border of the scapula facing the humerus. 
• Superior margin,margo superior; upper border of the scapula. 

  

  DonNMU.

  Clinical application: The scapula has numerous surface features because 15 muscles attach to it. Clinically, the pectoral girdle is significant becausethe clavicle and acromion of the scapula are frequentlybroken in trying to break a fall. The acromion is used as a landmark for identifying the site for an injection in the arm. This site is chosen because the musculature of the shoulder is quite thick and contains few nerves.

                         HOW TO KNOW LEFT OR RIGHT SCAPULA 

•   Identify the glenoid cavity and place it laterally. 
•   Place the spine of the scapula posteriorly.In this way you can be able to identify the position of the scapula easily. 

           The clavicle:The slender S-shaped clavicle(“collarbone”) connects the upper extremity to the axial skeleton and holds the shoulder joint away from the trunk to permit freedom of movement. The articulation of the medial sternal extremity of the clavicle to the manubrium of the sternum is referred to as the sternoclavicular joint. The lateral acromial extremity of the clavicle articulates with the acromion of the scapula.This articulation is referred to as the acromioclavicular joint. A conoid tubercle is present on the acromial extremity of the clavicle, and a costal tuberosity is present on the inferior surface of the sternal extremity. Both processes serve as attachments for ligaments. 

 Clinical application:The long, delicate clavicle is the most commonly broken bone in the body. When a person receives a blow to the shoulder, or attempts to break a fall with an outstretched hand, the force is transmitted to the clavicle, possibly causing it to fracture. The most vulnerable part of this bone is through its center, immediately proximal to the conoid tubercle. Because the clavicle is directly beneath the skin and is not covered with muscle, a fracture can easily be palpated, and frequently seen. 

                         FREE PART OF THE UPPER LIMB 

The humerus:The humerus is the longest bone of the upper extremity.It consists of a proximal head(proximal epiphyses), which articulates with the glenoidcavity of the scapula; a body (“shaft”); and a distal end(distal epiphysis), which is modified to articulate with the two bones of the forearm. Surrounding the margin of the head is a slightly indented groove denoting the anatomical neck. The surgical neck, the constriction just below the head, is a frequent fracture site. The greater tubercle is a large knob on the lateral proximal portion of the humerus. The lesser tubercle is slightly anterior to the greater tubercle and is separated from the greater by an intertubercular groove. The tendon of the long head of the biceps brachii muscle passes through this groove. Along the lateral midregion of the body of the humerus is a roughened area, the deltoid tuberosity, for the attachment of the deltoid muscle. Small openings in the body are called nutrient foramina. The humeral condyle on the distal end of the humerus has two articular surfaces. The capitulum is the lateral rounded part that articulates with the radius. The trochlea is the pulleylike medial part that articulates with the ulna. On either side above the condyle are the lateral and medial epicondyles. The large medial epicondyle protects the ulnar nerve that passes posteriorly through the ulnar sulcus. It is popularly known as the “funny bone” because striking the elbow on the edge of a table, for example, stimulates the ulnar nerve and produces a tingling sensation. The coronoid fossa is a depression above the trochlea on the anterior surface. The olecranon fossa is a depression on the distal posterior surface. Both fossae are adapted to work with the ulna during movement of the forearm. 

              Margins(borders): 

• Medial margin,margo medialis: inner margin of the humerus continuous distally with the medial supracondylar ridge.
•  Lateral margin,margo lateralis: outer margin of the humerus continuous distally with the lateral supracondylar ridge. 

                Surfaces: 

•  Anteromedial surface,facies anteromedialis: surface of the humerus lying medial to the prolongation of the crest of the greater tubercle. 
•  Anterolateral surface,facies anterolateralis: surface of the humerus located lateral to the prolongation of the crest of the greater tubercle. 
• posterior surface,facies posterior. 
  

   clinical application:The medical term for tennis elbow is lateral epicondylitis, which means inflammation of the tissues surrounding the lateral epicondyle of the humerus. At least six muscles that control backward (extension) movement of the wrist and finger joints originate on the lateral epicondyle. Repeated strenuous contractions of these muscles, as in stroking with a tennis racket, may strain the periosteum and muscle attachments, resulting in swelling, tenderness, and pain around the epicondyle. Binding usually eases the pain, but only rest can eliminate the causative factor, and recovery generally follows. 

        HOW TO KNOW IF A HUMERUS IS LEFT OR RIGHT. 
   clue I 
 1. Identify the head of the humerus and the medial epicondyle.               These two should be medially placed. 
 2.Identify the coronoid and radial fossae. These two should be               anteriorly placed with the olecranon fossa placed posteriorly. In        this position, we can determine if its left or right. 
 clue II 
      1. place the head of the humerus and the medial epicondyle at               the medial position. 
      2.the olecranon fossa should be posteriorly placed. 
      3.If the head of the humerus faces left,it means it is a right                  humerus and vice versa. 

   THE RADIUS:The radius consists of a body,corpus radii with a small proximal end, and a large distal end. A proximal disc-shaped head articulates with the capitulum of the humerus and the radial notch of the ulna. The prominent tuberosity of radius (radial tuberosity), for attachment of the biceps brachii muscle, is located on the medial side of the body, just below the head. On the distal end of the radius is a double-faceted surface for articulation with the proximal carpal bones. The distal end of the radius also has a styloid process on the lateral tip and an ulnar notch on the medial side that receives the distal end of the ulna. The styloid processes on the ulna and radius provide lateral and medial stability for articulation at the wrist. 
                                 Surfaces:

•  Anterior surface,facies anterior.
•  Posterior surface,facies posterior. 
•  Lateral surface, facies lateralis. 

                                 Borders: 

• Anterior border,margo anterior. 
• Posterior border,margo posterior. 
• Interosseous border,margo interosseous.

  Clinical application: When a person falls, the natural tendency is to extend the hand to break the fall. This reflexive movement frequently results in fractured bones. Common fractures of the radius include a fracture of the head, as it is driven forcefully against the capitulum; a fracture of the neck; or a fracture of the distal end (Colles’ fracture), caused by landing on an outstretched hand.

When falling, it is less traumatic to the body to withdraw the appendages,bend the knees, and let the entire body hit the surface.

Athletes learn that this is the safe way to fall.

                          how to know left and right radius

• The proximal end should face up and the distal end, down.
• Place the radial tuberosity medially.
• Identify the nutrient foramen and place it anteriorly.i.e away from you.
• The radial styloid process should also be at the lateral position.

   ULNA:The proximal end of the ulna articulates with the humerus and radius. A distinct depression, the trochlear notch, articulates with the trochlea of the humerus. The coronoid process forms the anterior lip of the trochlear notch, and the olecranon forms the posterior portion. Lateral and inferior to the coronoid process is the radial notch, which accommodates the head of the radius.

   On the tapered distal end of the ulna is a knobbed portion, the head, and a knoblike projection, the styloid process. The ulna articulates at both ends with the radius.In the forearm, it is located medially.

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                                          how to know left and right ulna

• The proximal and distal epiphysis should first of all be placed at the right position;proximal up, distal down.
• face the trochlear notch away from you and look at the olecranon.
• Check to see which side the radial notch is.
• If it is on the right, it a right ulna and vice versa.

                                     BONES OF THE HAND

The hand contains 27 bones, grouped into the carpus, metacarpus,

and phalanges.

   Carpus:The carpus, or wrist, or carpal bone contains eight bones arranged in two transverse rows of four bones each. 

  The proximal row, naming from the lateral (thumb) to the medial      side, consists of the: 

• scaphoid (navicular),os scaphoideum
• lunate,os lunatum
•  triquetrum,os triquetrum and 
• pisiform,os pisiforme.The pisiform forms in a tendon as a sesamoid bone. 

     The distal row, from lateral to medial, consists of the  

• trapezium,os trapezium (greater multangular), 
• trapezoid,os trapezoideum (lesser multangular), 
• capitate,os capitatum and 
• hamate,os hamatum. The scaphoid and lunate of the proximal row articulate with the distal end of the radius.

     Metacarpus:The metacarpus, or palm of the hand, contains five metacarpal bones. Each metacarpal bone consists of a proximal base, a body, and a distal head that is rounded for articulation with the base of each proximal phalanx. The heads of the metacarpal bones are distally located and form the knuckles of a clenched fist.

   The phalanges:The 14 phalanges are the bones of the digits. A single finger bone is called a phalanx (fa'langks). The phalanges of the fingers are arranged in a proximal row, a middle row, and a distal row.

  The thumb, or pollex (adjective, pollicis), lacks a middle phalanx.

The digits are sequentially numbered I to V starting with the

thumb—the lateral side, in reference to anatomical position.

   

   Clinical application: The hand is a marvel of structural complexity that can withstand considerable abuse. Other than sprained ligaments of the fingers and joint dislocations, the most common bone injury is a fracture to the scaphoid—a wrist bone that accounts for about 70% of carpal fractures. When immobilizing the wrist joint, the wrist is positioned in the plane of relaxed function. This is the position in which the hand is about to grasp an object between the thumb and index finger.

                                    Kamal Umar Labaran(Med)

                           Donetsk National Medical University.