lateralization

Examples of lateralization in the following topics:

• Chewing Muscles

  • Mastication, or chewing, involves the adduction and lateral motions of the jaw bone.
  • Lateral Pterygoid - The lateral pterygoid muscle has a triangular shape with two head, superior and inferior.
  • Actions - Together, the lateral pterygoids protract the jaw, working independently to produce lateral movement.
  • It is located inferior to the lateral pterygoid.
  • Actions: Elevates the jaw and assists in the production of lateral movement.

• Hemispheric Lateralization

  • But although measurable lateral dominance occurs, most functions are present in both hemispheres.
  • While many functions are lateralized, this is only a tendency.
  • While language production is left-lateralized in up to 90% of right-handed subjects, it is more bilateral or even right-lateralized in approximately 50% of left-handers.
  • The evolutionary advantage of lateralization comes from the capacity to perform separate parallel tasks in each hemisphere of the brain.
  • In a 2011 study published in the journal of Brain Behavioral Research, lateralization of a few specific functions as opposed to overall brain lateralization was correlated with parallel tasks efficiency.

• Ventricles

  • The cavities of the cerebral hemispheres are called lateral ventricles or first and second ventricles.
  • CSF flows from the lateral ventricles via the foramina of Monro into the third ventricle, and then into the fourth ventricle via the cerebral aqueduct in the brainstem.
  • This means they can be easily blocked, causing high pressure in the lateral ventricles.
  • As the future brain stem aspect of the primitive neural tube develops, the neural canal expands dorsally and laterally, creating the fourth ventricle.  
  • Lateral and anterior views of the brain ventricles, including the third and fourth ventricle, lateral ventricles, interventricular foramen, cerebral aqueduct, and central canal.

• Abducens (VI) Nerve

  • The abducens nerve (cranial nerve VI) controls the lateral movement of the eye through innervation of the lateral rectus muscle.
  • The abducens nerve (cranial nerve VI) is a somatic efferent nerve that, in humans, controls the movement of a single muscle: the lateral rectus muscle of the eye that moves the eye horizontally.
  • It then enters the orbit through the superior orbital fissure and innervates the lateral rectus muscle of the eye.

• Muscles that Cause Movement at the Hip Joint

  • The muscles of the lateral rotator group are deeply located and as the name suggests, act to laterally rotate the thigh at the hip.
  • Actions - Lateral rotation and abduction of the thigh at the hip.
  • Actions - Lateral rotation and abduction of the thigh at the hip.
  • Actions - Lateral rotation and abduction of the thigh at the hip.
  • Actions: Extends and laterally rotates at the hip.

• Carpals, Metacarpals, and Phalanges (The Hand)

  • The carpals are often split into two rows, the proximal row containing the scaphoid, lunate, triquetrum, and pisiform, moving lateral to medial.
  • The distal row contains the trapezium, trapezoid, capitate, and hamate, moving lateral to medial.
  • They are numbered moving lateral to medial, and start with the thumb, which is metacarpal I, and end with metacarpal V, the little finger.
  • Each metacarpal consists of a base, shaft, and head, with the concave lateral and medial borders of the shaft allowing attachment of the interossei muscles.
  • The digits are named in a similar fashion to the metacarpals, moving lateral to medial, and starting at the thumb.

• Femur (The Thigh)

  • Immediately lateral to the head is the neck that connects the head with the shaft.
  • Located superiorly on the main shaft, lateral to the joining of the neck, the greater trochanter is a projection to which the abductor and lateral rotator muscles of the leg attach.
  • Two rounded regions, termed the medial and lateral condyles, articulate with the tibia at the most anterior projection of the patella.
  • Finally, the two epicondyles, the medial and lateral, lie immediately proximal to the condyles; they are also regions where key internal knee ligaments attach.

• Oculomotor (III) Nerve

  • The muscles it controls are the striated muscle in the levator palpebrae superioris and all extraocular muscles, except for the superior oblique muscle and the lateral rectus muscle.
  • It passes between the superior cerebellar and posterior cerebral arteries, and then pierces the dura mater anterior and lateral to the posterior clinoid process (to give attachment to the tectorium cerebella), passing between the free and attached borders of the tentorium cerebelli.
  • It then runs along the lateral wall of the cavernous sinus, above the other orbital nerves, receiving in its course one or two filaments from the cavernous plexus of the sympathetic nervous system, and a communicating branch from the ophthalmic division of the trigeminal nerve.
  • It then divides into two branches that enter the orbit through the superior orbital fissure, between the two heads of the lateral rectus (a muscle on the lateral side of the eyeball in the orbit).

• Lumbar Plexus

  • Iliohypogastric nerve: Runs anterior to the psoas major on its proximal lateral border to run laterally and obliquely on the anterior side of the quadratus lumborum.
  • Lateral to this muscle, it pierces the transversus abdominis to run above the iliac crest between that muscle and the abdominal internal oblique.
  • It gives off several motor branches to these muscles and a sensory branch to the skin of the lateral hip.
  • Lateral cutaneous femoral nerve: Pierces the psoas major on its lateral side and runs obliquely downward below the iliac fascia.
  • Medial to the anterior superior iliac spine, it leaves the pelvic area through the lateral muscular lacuna and enters the thigh by passing behind the lateral end of the inguinal ligament.

• Organization of Motor Neuron Pathways

  • They then descend as the lateral corticospinal tract.
  • The function of lower motor neurons can be divided into two different groups: the lateral corticospinal tract and the anterior corticalspinal tract.
  • The lateral tract contains upper motor neuronal axons that synapse on the dorsal lateral lower motor neurons, which are involved in distal limb control.
  • These lower motor neurons, unlike those of the dorsal lateral, are located in the ventral horn throughout the spinal cord.
  • A deep dissection, lateral view of a brainstem.