Vertebral Column Anatomy

Vertebral Column

• 33 bones, 24 separate, 9 fuse (sacrum & coccyx)
• Approximately 70cm long in an adult of average height
• 7 cervical, 12 thoracic, 5 lumbar, 5 sacral and 3-4 coccygeal
• Functions: weight-bearing, anchor for muscles & ligaments, protection of spinal cord
• Normal curvatures: cervical and lumbar are concave, thoracic and sacral are convex

Supporting Elements of Vertebral Column

• Ligaments: strap-like, support the column of bones to stay upright; major are anterior & posterior longitudinal ligaments
• Intervertebral discs: cushioning between bony vertebral bodies; shock absorbers; 25% length of the vertebral column
  • Nucleus pulposus: acts like a rubber ball within the disc, providing elasticity and compressibility
  • Annulus fibrosus: holds together successive vertebrae & resists tension in the spine

A Typical Vertebra

• Gets larger as you descend the column
• Weight-bearing body + vertebral arch
• Vertebral arch: 2 pedicles + 2 laminae
• Arch + body enclose a vertebral foramen
• Pedicles: have notches on superior & inferior surfaces → intervertebral foramina
• 7 processes from each vertebral arch:
  • Spinous process: muscle attachment
  • Transverse processes (2): muscle attachment
  • Paired superior & inferior articular processes: link vertebrae above & below

Cervical Vertebrae

• 7 total, #1 & 2 have unusual structures and no intervertebral disc
• #3-7 are considered typical:
  • Body is oval, broader side-to-side than front-to-back
  • Spinous process is short and spilt at the end
  • Vertebral foramen is large -Each transverse process contains a transverse foramen for passage of the vertebral artery to the brain

Atlas (Cervical Vertebra #1)

• No body or spinous process
• Posterior & anterior neural arches
• Superior articular facets articulate with occipital condyles allowing the head to nod “yes”

Axis (Cervical Vertebra #2)

• Similar to C3-C7, except for dens or odontoid process which allows the head to rotate “no”
• Dens is the “missing” body of the atlas

Thoracic Vertebrae

• 12 total, all have ribs attached
• Increase in size from the first to the last
• Features:
  • Body is roughly heart-shaped and bears facets for ribs
  • Vertebral foramen is circular
  • Spinous process is long and points down
  • Transverse processes have facets for articulation with tubercles of ribs

Lumbar Vertebrae

• Lower back, major weight-bearing function
• Bodies are kidney-shaped and increase in size from top to bottom
• Features:
  • Pedicles & laminae are shorter & thicker than those of other vertebrae
  • Spinous processes are flat & short
  • Vertebral foramen is triangular
  • Inferior & superior facets are unique - curved

Sacral Vertebrae

• Starts as 5 separate vertebrae, fuse in adolescents = sacrum
• Articulates with 5th lumbar and laterally with hip bones (sacroiliac joint)
• Note: sacral promontory, transverse lines and sacral foramina
• Note: median sacral crest, sacral canal and sacral hiatus

Coccygeal Vertebrae

• Tailbone = 3 or 4 fused coccygeal vertebrae
• Attachment area for some pelvic ligaments, but otherwise useless

Bony Thorax

• Thoracic vertebrae + ribs + costal cartilages + sternum
• Protective cage around heart, lungs & major blood vessels
• Supports shoulder girdle & upper limbs
• Provides area of muscle attachment for back, chest & shoulders

Sternum

• Anterior midline of thorax
• Fusion of 3 bones: Manubrium, body & xiphoid process
• Manubrium articulates with clavicles via clavicular notches and with the first pair of ribs
• Body has notches for articulation with the 2nd to 7th ribs
• Xiphoid process is the attachment of some abdominal muscles

Ribs

• 12 per side, all attach to the vertebral column at the back
• Curve inferior-anteriorly
• 7 true ribs attach directly to the sternum
• False ribs: Ribs 8-10 attach indirectly to the sternum via costal cartilage and rib 7
• Floating ribs: ribs 11 & 12 are not attached anteriorly
• Features of a typical rib: shaft, head, neck, tubercle
• Note: the costal groove, 2 facets on the head (one articulates with the same-numbered vertebra and the other with the superior vertebra), tubercle articulates with the same-numbered thoracic vertebrae

Appendicular Skeleton

• Pectoral girdle: clavicles & scapulae
• Pelvic girdle: hip bones (coxal bones) plus upper & lower limbs

Pectoral Girdle

• Clavicle: S-shaped, slightly curved, acts as a brace to push the arms laterally
• Scapulae: thin, triangular flat bones, dorsally, between ribs 2 & 7
• Note: superior, medial & lateral borders, spine, acromion, coracoid process

Upper Limb

• 30 separate bones: arm, forearm, wrist and hand

Humerus

• Longest bone of the upper limb, the only bone of the "arm"
• Articulates with the scapula proximally, radius + ulna distally
• Note: head, anatomical neck, greater tubercle, lesser tubercle, intertubercular sulcus, surgical neck
• Note: 2 condyles + 2 epicondyles
  • Trochlea: articulates with ulna
  • Capitulum: articulates with radius
  • Ulnar nerve runs behind the medial epicondyle

Forearm

• 2 parallel long bones: radius & ulna
• Articulates with humerus & wrist bones, also articulate with each other proximally and distally
  • Interosseous membrane is a strong fibrous sheet between the radius & ulna
• Ulna (elbow joint): slightly longer than radius, olecranon & coronoid process, radial notch on coronoid process, styloid process
• Radius (wrist joint): head at proximal end, distal end is the wider end
  • Distal end: medial ulnar notch & lateral styloid process

Hand

• 27 bones total: carpus, metacarpus & phalanges

Carpus (wrist)

• 8 carpal bones - only scaphoid & lunate articulate with radius
• “So Long To Pittsburgh” (scaphoid, lunate, triquetrum, pisiform)
• “Time To Call Home” (trapezium, trapezoid, capitate, hamate)
• “Sally Left The Party To Take Cathy Home”

Metacarpus

• 5 long bones, distal ends are knuckles
• Numbered 1-5 from the thumb to the little finger

Phalanges

• 3/finger & 2/thumb = miniature long bones
• Numbered 1-5 from thumb to little finger
• Proximal, middle & distal except for thumb which has only proximal & distal

Pelvic Girdle

• Attaches lower limbs, transmits weight of upper body to lower limbs, supports visceral organs of pelvis
• Forms a complete circle
• Left & right hip bones (coxal bones) unite anteriorly & with sacrum at back
• Each os coxa consists of 3 bones that fuse at puberty: ilium, ischium, pubis
  • Acetabulum is the area where all 3 bones join and forms the socket of the hip joint

Ilium

• Large flaring bone that forms most of the os coxa
• Note: iliac crest, iliac spines, pelvic brim

Ischium

• Postero-inferior part of the hip bone
• Note: ischial tuberosity

Pubis

• Anterior part of the ox cosa
• 2 pubic bones unite at pubis symphysis
• Note: pubic crest, obturator foramen

Lower Limb

• Thigh, leg & foot

Thigh

• Femur: largest, longest and strongest bone
  • Major parts: head, fovia capitis, neck, linea aspera, lat & med condyles, lat & med epicondyles, patellar surface
  • Greater & lesser trochanters: attachment for muscles

Patella

• Sesamoid bone, embedded in the tendon of the quadriceps muscles

Leg

• 2 parallel bones: tibia & fibula
• Interosseus membrane + proximal & distal tibiofibular joints (rigid)
• Fibula does not contribute to the knee joint
• Tibia: transfers weight from the femur to the foot, next largest & strongest bone
  • Note: med & lat condyles, anterior border, tibial tuberosity
• Fibula: note head & lateral malleolus

Foot

• 26 bones: tarsus (ankle bone), metatarsus & phalanges

Tarsus

• 7 tarsal bones: largest is the calcaneus (heel bone), second largest is the talus (part of the ankle joint)

Metatarsus

• 5 miniature long bones numbered 1-5 (medial great toe = +1)

Phalanges (foot)

• Big toe (hallux) has two & remaining toes have 3 each - proximal, middle & distal