The Skeleton

Dr. Ali Ebneshahidi

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Axial Skeleton • Skull 22 bones

• 8 cranial bones

– Frontal 1

– Parietal 2

– Occipital 1

– Temporal 2

– Sphenoid 1

– Ethmoid 1

• 14 facial bones

– Maxilla 2

– Palatine 2

– Zygomatic 2

– Lacrimal 2

– Nasal 2

– Vomer 1

– Inferior nasal concha 2

– 1 mandible

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• Middle ear bones

Malleus 2 6 bones

Incus 2

Stapes 2

• Hyoid bone

Hyoid 1 1 bones

• Vertebral column 26 bones

Cervical vertebra 7

Thoracic vertebra 12

Lumbar vertebra 5

Sacrum 1

Coccyx 1

• Thoracic cage 25 bones

Ribs 24

Sternum 1

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The Appendicular Skeleton

• Pectoral girdle

Scapula 2 4 bones

Clavicle 2

• Upper limbs 60 bones

Humerus 2

Radius 2

Ulna 2

Carpal 16

Metacarpal 10

Phalanx 28

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• Pelvic girdle 2 bones

Coxal bone 2

• Lower limbs 60 bones

Femur 2

Tibia 2

Fibula 2

Patella 2

Tarsal 14

Metatarsal 10

Phalanx 28

Total 206 bones

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Skull (Cranium)

• Skull Skull: protect brain (brain

case).

Facial bones:

- Contains cavities for sense

organ (eyes, smell).

- Frame of the face.

- Attachment sites for muscles of

mastication & facial expression.

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The Eight bones of the cranium

a) Frontal bone (forehead):

• Frontal sinuses

• Forms superior part of orbits

• Forms roof of nasal cavity

• b) Parietal bones and major

sutures:

• Curved, rectangular bone.

• Forms the bulging sides and

roof of cranium.

• The 4 largest sutures occur

where parietal bone.

articulates with other bones.

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• Coronal suture: where

parietal bones meet the

frontal bone anteriorly.

• Lambdoid suture: where

parietal bones meet the

occipital bone posteriorly.

• Squamous suture: where

parietal and temporal bone

meet on the lateral aspect

of the skull.

• Sagittal suture: where

the 2 parietal bones meet

superiorly at the cranial

midline.

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• C) Occipital bone:

• Forms the back (posterior) of skull.

• Foramen magnum: a large opening on its lower surface houses nerve

fibers that pass through and enter the vertebral canal to become the

spinal cord.

• Occipital condyles: articulates with the first vertebra (atlas).

• Hypoglossal canals: for passage of hypoglossal nerves.

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• d) Temporal bones:

– Lateral sides of skull.

– Contains the external auditory meatus (external ear).

– Mandibular fossa – receive condyles of mandible (lower

jaw).

– Zygomatic arch (process) – projects interiorly from the

temporal bone.

– Mastoid process – attachment for muscles of neck.

– Styloid process – attachment for muscles of tongue and

pharynx.

– Jugular foramen – at the junction of occipital and petrous

temporal bone, allows passage of the internal jugular vein.

– Carotid canal – transmit internal carotid artery.

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• e) Sphenoid bone (butterfly - shaped):

– Sella turcica – indentition of a part of sphenoid;

in the depression lies the pituitary gland.

–Contains 2 sphenoid sinuses.

– It has greater and lesser wings.

–Optic foramina – allows passage of the optic

nerve.

–Superior orbital fissure – a long slit between the

greater and lesser wing allows passage of the

cranial nerves that control eye movements (III,

IV, VI) to enter the orbit.

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• F) Ethmoid bone:

– Olfactory foramina – passage for the olfactory nerve.

– Middle and superior nasal concha (nasal plates), also known as

turbinates.

– Ethmoid sinuses.

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Facial Skeleton • Maxillary bones (upper jaw):

• All facial bones except mandible articulate with maxilla.

• Forms roof of mouth (anterior 2/3 of hard palate).

• Contains upper teeth .

• Maxillary sinuses (largest sinuses).

• Zygomatic process of maxilla articulate with zygomatic

bone.

• Infraorbital foramen – allows passage of infraorbital nerve.

• Infraorbital fissure – at junction of maxilla with the greater

wing of sphenoid allows passage of zygomatic nerve,

maxillary nerve (a branch of cranial nerve V), and blood

vessels.

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• Palatine bones:

– L shaped.

– Forms post 1/3 of hard plate.

• Zygomatic bones (cheek bones):

– Temporal process, which extends posteriorly to join the

zygomatic process of temporal bone. Together these

processes form the zygomatic arch.

• Lacrimal bones:

–A groove in its anterior portion forms the lacrimal fossa

(tear channel).

• Nasal bones:

– Forms bridge of nose medially.

–Attachment of cartilaginous tissues that form the shape of

the nose.

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• Vomer bone: unpaired, forms the nasal septum along with

ethmoid bone.

• Inferior nasal conches (largest): Support mucous

membranes within nasal cavity.

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• Mandible (lower jaw):

–Unpaired.

–Horseshoe – shaped (u-shaped).

–Largest bone of the face.

–It has a body –anchors the lower teeth.

–2 ramus.

–Coronoid process – site of attachment of

temporalis muscle that elevates jaw

during chewing.

–Mandibular condyle – articulates with

mandibular fossa of temporal bone to

form T.M.J.

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• The orbits:

• Bony cavities within which the eyes are encased. The walls of each

orbit are formed by parts of seven bones (the frontal, sphenoid,

zygomatic, maxilla, palatine, lacrimal, and ethmoid bones).

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Infantile skull

• At birth, skull is

incompletely developed,

with fibrous membranes

connecting the cranial

bones. These membranes

are called fontanels (soft

spots).

• Allow brain growth by

allowing skull to expand.

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The vertebral Column

• The vertebral column (the spine):

• Cervical spine (C1-C7)

• Thoracic spine (T1-T12)

• Lumbar spine (L1-L5)

• Sacrum (5 vertebra fused into one bone)

• Coccyx (4 vertebra fused)

Curvatures of spine:

• Cervical & Lumbar are concave posteriorly.

• Thoracic & sacral curvature are convex

posteriorly.

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Abnormal Curvatures:

• Scoliosis: abnormal

lateral curvature of

spine.

• Kyphosis (hunch

back): exaggerated

T- spine dorsally.

• Lordosis:

exaggerated Lumbar

curvature.

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Intervertebral Disc • Intervertebral discs: cushion like pads located between

vertebrae. It is composed of 2 parts.

• Nucleus pulposus – act like a rubber ball which gives disc

elasticity and compressibility.

• Annulus fibrosus – a strong collar of collagen fibers and fibro-

cartilage, holds the nucleus pulposus in place and resists

tension in spine. Rupture of annulus fibrosus causes protrusion

of nucleus resulting in herniated disc.

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General structure of vertebrae

• Body: weight bearing

portion, located anteriorly.

• Vertebral arch: located

posteriorly. Seven

processes project form

this arch.

• Vertebral foramen: opening

enclosed by the body and

vertebral arch, through

which the spinal cord

passes.

• Pedicle: project posteriorly

from the vertebral body.

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• Lamina: flattened plates that

fuse posteriorly to close the

arch.

• Spinous process: posterior

projection arising from the

junction of 2 lamina

(posterior projection of the

arch).

• Transverse process: extends

laterally from each side of

the arch.

• Intervertebral foramina: the

spinal nerves arising from

the spinal cord pass through

these holes.

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Vertebral Characteristics

• Cervical vertebrae: (C1-C7)

• C1= known as atlas.

• C2= known as axis.

• C7= known as vertebra prominens.

• C1 – has no body and no spinous process.

• C2 – has a knob like structure called dens or odontoid process

projecting superiorly. Odontoid allows rotation of atlas.

• C3- C7 have the following characteristics:

• The body is oval shaped.

• The spinous processes are short (except for C7 that is long).

• Vertebral foramen is triangular & large.

• Each transverse process contains a transverse foramen through

which the vertebral blood vessels pass to service the brain.

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• Thoracic vertebrae: (T1-T12)

• The body is heart shaped.

• Vertebral foramen is circular.

• Sp is long and points sharply inferiorly.

• With exception of T11 and T12 ,they articulate

with ribs.

• Lumbar vertebrae: (L1-L5)

• The body is massive and kidney shaped

(support body weight).

• Vertebral foramen is triangular.

• Sp's are short.

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• Sacrum: Triangular shaped structure. Formed by fusion of 5 vertebrae.

It strengthen and stabilize the pelvis.

• Coccyx (Tail bone): Formed by fusion of 4 vertebrae.

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The bony Thorax (Thoracic Cage )

• Includes the ribs, thoracic vertebrae, the sternum, and the

costal cartilages.

• Sternum: (breast bone) - lies in anterior mid – line of the

thorax. It results from the fusion of 3 bones:

Manubruin, body, and xiphoid process.

• Ribs:

• 12 pairs.

• 1-7 ribs are true ribs because they join the sternum

directly.

• Reaming 5 ribs are false ribs (8 -12) they do not have

sternal attachment, directly.

• Ribs 11-12 are floating ribs – no anterior attachment.

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• The pectoral girdle (shoulder girdle ): 4 parts.

• 2 clavicles (collar bones) & 2 scapulae (shoulder blades)

• Clavicle: has a sternal (medial end) & an acrominal (lateral end).

• Scapula:

– glenoid cavity: articulates with the humerus of the arm, forming

the shoulder joint (glenohumeral joint).

– Spine: divides the scapula into unequal portions called the supra-

spinous and infraspinous fossa.

– the Acromion: the spine ends laterally in an enlarged anterior

projection, articulates with clavicle to form A-C joint.

– coracoids process: site of attachment of biceps muscle and other

upper limb muscles.

– subscapulars fossa (cavity): concavity of the entire anterior

scapular surface.

The Appendicular Skeleton

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The upper Limb

• Humerus: single bone of

the arm.

• Head – fits into the glenoid

cavity of scapula.

• It has a greater tubercle & a

lesser tubercle which are

sites of attachment of

muscles that move the upper

limb, at shoulder.

• Intertubercular groove –

tendon of biceps brachii

muscle passes through this

groove.

• Deltoid tuberosity –

attachment site of deltoid

muscle.

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• Radial groove – radial nerve

passes through this groove.

• Trochlea – located medially at

distal end of humerus.

• Capitulum – located laterally

at distal end of humerus.

• Medial & lateral epicondyles –

for attachment of muscles.

Ulnar nerve passes behind the

medial epicondyle.

• Coronoid fossa – ant. surface,

receives the coronoid process

of ulna.

• Olecranon fossa – posterior

surface of humerus (distally) –

receives the olecranon process

of ulna.

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Forearm (Radius & Ulna) • Radius:

• located on thumb side of the

forearm.

• extends from elbow to wrist

and crosses over the ulna

when the hand is turned so

that the palm faces

backward.

• head – articulates with

capitulum of the humerus.

• radial tuberosity –

attachment point for biceps.

• styloid process – attachment

point for the ligaments of

the wrist.

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• Ulna:

• longer than radius.

• forms the elbow joint

with humerus.

• olecranon and coronoid

process fit into the

olecranon fossa and

coronoid fossa of the

humerus when the

elbow bends.

• head – located at distal

end of ulna.

• medial styloid process –

site of attachment of

ligaments of wrist.

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• hand: Wrist

Palm

5 fingers

• Wrist: consists of 8 short bones.

• Proximal row: (lateral to medial ) - scaphoid, lunate,

triquetral, pisiform.

• Distal row: (lateral to medial) – trapezium, trapezoid, capitate,

hamate.

• [Sally Left The Party To Take Cathy Home]. ebneshahidi

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Metacarpals & Phalanges of the hand

• 5 bones, one in line with each finger,

numbered 1-5 from thumb to little finger.

• Their base articulate with carpals and their

head with phalanges (are considered long

bones even though small).

• Phalanges (Fingers):

• Numbered 1-5

• Have proximal, middle and distal ends (thumb

lacks middle phalanx).

• So each hand has 14 finger bones.

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The Pelvic (Hip) Girdle

• Consists of 2 coaxal bones (hip bones).

• Transmits the weight of body to legs.

• Protects urinary bladder, distal end of large intestine, and

reproductive organs.

• Coaxal bones:

– Ilium

– Ischium

– pubis

• These 3 bones fuse in a region of cup–shaped cavity called

acetabulum.

• Ilium:

• largest and most superior portion of the coaxial bone, flares

outward.

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• posterioly it joins the sacrum to form the Sacroiliac joint.

• posterioly indents to form the greater sciatic notch.

• Ischium:

• forms the posteroinferior part of the hip bone, L – shaped.

• has an ischial tuberosity, that supports our weight when

seated, and is the strongest part of the hip bones.

• Pubis:

• forms the anterior portion of the coaxl bone, the 2 pubic

bones come together at midline to form the pubic

symphysis.

• V – shaped.

• Obturator foramen – largest foramen of body (skeleton), is

formed by both ischium + pubis bones.

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The Lower Limb

• Femur (thigh bone):

• Longest, strongest bone

of the body.

• Head of femur fits into

the acetabulum.

• Greater & lesser

trochanter – site of

attachment of muscles.

Greater trochanter is

superior and laterally

located. Lesser

trochanter is medially

located and is inferior

to greater trochanter.

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• Lateral and medial

condyles, located

distally and articulate

with tibia of the leg.

• Lateral and medial

epicondyles – provide

attachment for muscles

and ligaments.

• Patella (knee cap):

• Flat bone.

• Located anteriorly

over the knee.

• Important in knee

motion.

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• Tibia (shin bone):

• Largest of the 2 leg bones.

• Located on the medial side

of leg.

• Next strongest bone in body.

• Leteral & medial condyles.

• Tibial tuberosiy –

attachment point for patellar

ligament.

• Medial malleolus - distal

medial ankle.

• Fibula:

• Head- located proximally.

• Lat. Malleolus, distally

located.

• Forms the lat. ankle. ebneshahidi

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• Foot:

1) Tarsal bones

2) Metatarsals

3) Phalanges

• Tarsal bones – 7 tarsals

• Talus – can move freely

where it joins tibia and

fibula.

• Calcaneus – forms the

heel of foot. It is the site

of attachment of Achillis

tendon.

• The reaming tarsal are

the Cuboid, Navicular

and the Medial,

Intermediate, and Lat.

Cuneiforms.

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• Metatarsals:

numbered 1- 5,

beginning on the

medial side.

• Phalanges (toes):

14 phalanges.

• 3 phalanges in

each toe except

for great toe (the

hallux), which

has two.

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Clinical Terms

• Bunion – Deformity of great toe; lateral displacement

of great toe and medial displacement of metatarsal 1,

caused by thight shoes.

• Club foot – congenital disease in which the soles of

feet face medially and toes point inferiorly.

• Chiropractic – treating disease by manipulating the

spine.

• Podiatrists - a specialist in foot disorders.

• Orthopedists – surgeon who repair damaged bone and

joints.

• Prolapsed disc – herniated disc.

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