Vertebrae and muscles of the back

Lecturer: Dr. M. SamsamUniv. of Central Florida

Pictures from: K. Moore Human anatomy and Platzer atlas and text book of human anatomy

Vertebral column

Vertebral column forms the basic structure of the trunk. It consists of 33-34 vertebrae and intervertebral disks. There are 7 cervical, 12 thoracic, 5 lumbar, 5 sacral and 4-5 coccygeal vertebrae in human.

Intervertebral disks (fibrocartilage) between the vertebrae, absorb shock, assure no friction between the bones and facilitate the movements of the vertebral column.

Curvatures of the vertebral column:

Lordotic curveKyphotic curveScoliosis

Different parts of a vertebra

*Content of the vertebral canal:

Spinal cord and its blood vesselsplus the meninges and the CSF.

Cervical Vertebrae:First cervical vertebra is called Atlas, the 2nd is called Axis.

The 7th is called: Vertebra Prominens.3rd, 4th,5th and 6th are similar.

*Characteristics of cervical vertebrae:

A- transverse foramen. B- bifid spinous process. C- small vertebral body. D- large and triangular vertebral canal.

*Contents of the transverse foramen: Vertebral artery

(C3-C7)

Vertebral arteries:

pass through the transverse foramen of the 6 upper Cervical Vertebrae.

They enter the skull through the Foramen Magnum

Vertebral artery

Atlas (1st cervical V., C1)Has: no spinous process, no body, small anterior arch and a larger

posterior arch. Anterior tubercle, Posterior tubercle, Large vertebral foramen, 2 lateral masses.

Each mass has a superior and an inferior articular facet.Atlanto-occipital joint (between atlas and occipital bone).

Axis (2nd cervical V., C2)Has an Odontoid process (dens) with an anterior articular facet to articulate with

atlas, and a posterior articular facet for transverse ligament of atlas.

*Hangman Fracture in the arch of axis pushes the dens posteriorly and compresses the brain stem, leading to death.

*Fracture of the dens is a typical fracture of C2.

Atlanto-occipital articulation (upper head joint):Between superior articular facet of Atlas and Occipital condylesAtlanto-Axial articulation (lower head joint):Consists of median and lateral atlanto-axial articulations.

Securing ligaments: Transverse ligament of atlas (between the two lateral masses).Apical ligament of the dens (attaches to anterior margin of foramen magnum).Alar ligaments (from dens to lateral margin of foramen magnum.Etc…

Clinical tips:

*cervical rib (20): when the costal element ispreserved independently. Usually bilateral,if one sided, usually on the left side

*The presence of a cervical rib may cause a triad of disorders:A- Ischemic muscle pain due to compression of the subclavian artery.B- pain in the ulnar side of the forearm & hand.C- palpable mass over the clavicle.

Thoracic Vertebrae:There are 12 thoracic vertebrae in human.

Important characteristics:Have 2 articular facets (2 and 17) on theirlateral side (one on the body and the otheron the transverse process).

Spinous process is long and slopes posteroinferiorly.

Costo-vertebral joints:The head of each rib articulates with 2 adjacentvertebrae and the disk between them

Costo-transverse joints: between the tubercleof the rib and the transverse process of it’s own vertebra

Lumbar vertebrae:

There are 5 lumbar vertebrae in human.Characteristics: Large body (1), kidney shape.Long transverse process (5).Relatively small vertebral foramen (15).

*Lumbar puncture:Is done at L3-L5 region.The intercrestal line (iliac crests) is at the level of L4 approximately (safe region).

Ribs: 12 ribs

1-7 are the true ribsThe last 5 are false ribs11 and 12th ribs are floating ribs

1- head, 2- neck, 3- body4- tubercle

*Costal groove: contains the intercostal nerve and vessels. Head and the tubercle have articular surfaces to articulate with the vertebrae

Sternum: Consist of:

1- Manubrium, 2- body, 3- Xiphoid process4- Sternal angle T4, 5- jugular (suprasternal)notch, 6- clavicular notch, 8- notch forarticulation with 2nd rib, Sex differences: Body is longer, narrowerand slimmer in males than in females

*Sternal puncture: Bone marrow needle biopsy for transplantation orcytologic analysis:In the midline in the body of sternum between2-3 ribs attachmentsNever try in the lower 2/3 of the sternal body.

Median Sternotomy: in coronary bypass surgery

Congenital anomalies: *Complete sternal cleft: associated with ectopia cordis.*Pectus excavatum (funnel chest) *Pigeon chest *Congenital sternal (10) fissure (sternal foramen).*Aneurysm of the Aorta: pulsatile mass at suprasternal notch (T2); arch is behind the manubrium.

Joints of the vertebral column:

*Zygapophysial joints (A-B)These are the small vertebral joints betweenthe articular processes.

Uncovertebral joints:Between cervical vertebrae. They developby age and may become pathologic and permit disk herniation especially in C5 region.

Intervertebral disks:

Fibrocartilage tissue.They consist of an outer tense part, the Anulus Fibrosus (1) and a soft jelly-like nucleuscalled the Nucleus Pulposus (remnant of theNotochord, embryonic tissue).

Function:Acts as a shock absorber, is compressible andpermits slight degree of movement of the vertebrae over each other.They build up approximately 20% of the lengthof the vertebral column (taller in the mornings).

*Herniation:Mostly posterolaterally where the Anulus Fibrosus is thinner.

Disc herniation

Disc herniation

Ligaments of the vertebral column:

Many, among them,Anterior longitudinal lig (1)Post. Longitudinal lig (2)Ligamentum flavum (5) , yellowish in color due to Elastic fibers, facilitates movementsIntertransverse ligs (7)Interspinous lig (8)Supraspinal lig (10).

Sacrum:

Consists of 5 sacral vertebrae and the intervertebral disks that lie between them.It has a concave anterior surface (A) and aconvex dorsal surface (B).

Females: sacrum is wider, shorter, more concave.Males: sacrum is longer and less wide.

*Sacral hiatus, Sacral horns (cornua)

*Epidural anesthesia is given through sacral hiatus to block the pelvic nerves.

Epidural anesthesia

Coccyx:

Four vertebrae (rudimentary).

6- Cornua or horns of coccyx facing sacrum.

Injury to coccygeal vertebrae:Falling on buttocks, specially in females,Painful delivery. Coccydyna: pain in coccyx

Abnormal fusion and defects of the vertebrae:

Sacralization of L5 Lumbarization of S1

*Spina Bifida:Failure of vertebral arches to form or fuse. Usually In lumbar or sacral vertebraeLeading to meningocele (just meninges bulge out of the vertebral canal) ormeningomyelocele (meninges plus spinal cord bulge out).

Spina bifida Occulta:

*Folic acid substitution in conception and during pregnancy decreases the risk ofspina bifida.

Congenital anomalies (continued):

Muscles of the back:Cranial muscle inserted on the Shoulder girdle:

1- Trapezius M: has 3 parts: 2- Descending part 3- Transverse part 4- Ascending part

Descending part:Origin: from external occipital protuberance,superior nuchal line, and Ligamentum nuchaeInsertion: lateral third of the clavicleTransverse part: from C7-T3 spinous processInserted to: clavicle and scapula (acromion)Ascending part: from T3-T12 spinous processInsertion: spine of the scapula

*Function: elevation, retraction and rotation of scapula.Helps in adduction and slight elevation of arm**Innervation: spinal root of Accessory nerve(CNXI) and C3-C4 (propioception and pain).

Back muscles inserting on the shoulder girdle

Rhomboid Minor (1):Origin: spinous precess of C6 and C7 (2).Insertion: medial margin of scapula (3).

Rhomboid Major (4): caudal to Rh. minorOrigin: spinous process of T1-T4 (5)Insertion: medial margin of scapula (3)*Function of both muscles: press the scapula to the thoracic wall, retraction of scapula medially.Nerve supply: dorsal scapular nerve (C4-C5)

Levator Scapulae(6):Origin: transverse process of C1-C4Insertion: superior angle of scapulaFunction: elevates the scapulaInnervation: dorsal scapular nerve (C4-C5)

12- Latissimus dorsi M: (coughing M)Has many parts:Origin: 13:vertebral part T7-T12 spinous process 14:thoracolumbar part (from fascia)15:iliac part (from iliac crest) 16:costal part: 10-12th rib17- inferior angle of scapula

Insertion: crest of the lesser tubercle of humerus (18).*Function:Adduction and lowering the arm, medial rotation and extension of the arm (humerus).Raises the body toward the arm when climbing.*Innervation:Thoracodorsal N. (C6, C7, C8).

5- Serratus post. InferiorInnervation: intercostal nerves (T9-T12).

12- Serratus post. SuperiorFunction: rib elevation

*Both may function as accessory muscles of respiration (in COPD).

Intrinsic muscles of the back (erector Spinae)2 groups:Lateral (superficial) group Medial deep group.

**Lateral group:Iliocostalis (1,2,3), lumborum, thoracis, cervicisLongissimus (4,5,6) thoracis, cervicis, capitisSplenius crvicis (11) and capitis (12)

*Innervation: all by primary spinal dorsal rami

*Function: for erect posture of the body and the two splenii rotate the head.Extensors when both sides contract and flexion when one side contracts.

Medial group

Interspinales Muscles (1,2,3)Intertransverse muscle (4) cervicis and lumbar (5).

Spinalis Thoracis (6) and Cervicis (7) andperhaps capitis as well.

Rotator brevis (8) and longus (9) thoracis

Multifidus (10)

Semispinalis cervicis (11) and capitis (12)

All innervated by various primary dorsal rami.Function: Extensors when both sides contract and flexion when one side contracts. Some stabilize and some rotate the vertebral column.

1- rectus capitis posterior minor muscle

**Suboccipital triangle2- rectus capitis post. Major3- Oblique capitis superior4- Oblique capitis inferior

**Content: A- 3rd part of vertebral artery, B- Suboccipital nerve (C1) innervating all 3 musclesC- Suboccipital plexus of veins

Function: turning the head backward orlaterally.

**Vertebrobasilar syndrome

Sensory innervation of the region:Greater occipital nerve (C2)

Suboccipital triangle content

Atlas