lumbar sympathetic system : autonomic Nervous system

 Lumbar syspathetic system : include lumbar sympathetic ganglia, medial and lateral branches of lumbar sympathetic ganglia , collateral ganglia , plexus and target organ

Lumbar ganglion :

Numbar:

The lumbar part of each sympathetic trunk usually  contains four interconnected ganglia.

Relation :

They lying on the anterolateral aspects of body of the lumbar vertebra along the medial margin of the psoas major 

Superiorly , it is continuous with thoracic sympathetic ganglion posterior to the medial arcuate ligament

Inferiorly it passes posterior to the common iliac vessels  and continuous with sacral sympathetic ganglion

•       On the right side it is situated just posterior to the inferior vena cava

•       On the left posterior to the lateral aortic lymph nodes 

Branches of lumbar sympathetic ganglion

Two branches : lateral and medial branches

1.       Lateral branches :  1^st and 2^nd (occasionally 3) lumbar sympathetic ganglia are connected by ventral ramus of lumbar spinal nerves by  grey & white rami communicans .

            3^rd and 4^th lumbar ganglia are connected by ventral ramus of lumbar spinal nerve 

                      only by grey ramus communicans 

2.       Medial branches : Four lumbar splanchnic nerves pass as medial branches from the ganglia 

Lumbar splanchnic nerves

Lumbar splanchnic nerves  conveys two types of fibres

General visceral efferent fiber : Lumbar splanchnic nerve content sympathetic efferent fiber , It conveys pre-ganglionic sympathetic fiber .It innervates smooth muscle cells and glands

·         General visceral afferent fiber : Collect sensory information from the visceral 

Collateral ganglion related with lumbar splanchnic nerves 

  Preganglionic sympathetic fibres of Lumbar splanchnic nerves  are synapse with postganglionic neuron present within the inferior mesenteric ganglion . 

General visceral afferent fibres of lumbar splanchnic nerves are passes through the inferior mesenteric ganglion 

Autonomic plexuses related with lumbar splanchnic nerves

  1^st lumbar splanchnic nerve give fibers to the :

•       coeliac , renal , inter-mesenteric  and inferior mesenteric plexuses

2^nd  lumbar splanchnic nerve give fibers to the

•       Inferior mesenteric plexus

3^rd   lumbar splanchnic nerve give fibers to the

•       Inferior mesenteric plexus

•       Superior hypogastric plexus

4^th   lumbar splanchnic nerve give fibers to the

•       inferior mesenteric plexuses

•       Superior hypogastric plexus

 Lumbar sympathetic system innervates  :

Innervate pelvic viscera (ex: Bladder neck, Vas deferens,Prostate)  and vasculature.  

Clinical anatomy :

•       Damage to lumbar splanchnic nerves  during aortoiliac surgery can result in sexual dysfunction.

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Role of organizer in embryology

Organizer: a region of the embryo that is capable of determining the differentiation of other regions.

The term “organizer,” or “primary organizer,” was introduced by the German embryologist and 1935 Nobel laureate H. Spemann to designate the material of the dorsal lip of the blastopore—the prospective chordamesoderm—in the amphibian gastrula .

When transplanted to a remote site, for example, the ventral side of the embryo or the blastocoel, the material of the dorsal lip not only differentiates into organs that would normally arise had the transplant not taken place but also induces the development of neural and other structures in areas adjacent to the transplant site; this is an example of primary embryonal induction

 As a result of the action of the organizer, a new, more complex embryo forms in which the organs are situated roughly according to their future distribution.

•      Primary organizer: primitive streak (it induces the development of notochord)

•      Secondary organizer: notochord (it induces the development of neural tube)

•      Tertiary organizer: neural tube (it induces the development of somites of paraxial mesoderm)

Easy summary of Extrapyramidal system

Extrapyramidal system

The  extrapyramidal system is a part of the motor system network causing involuntary actions. The system is called extrapyramidal to distinguish it from the tracts of the motor cortex that reach their targets by traveling through the pyramids of the medulla.

Extrapyramidal tracts are chiefly found in the reticular formation of the pons and medulla.

The pyramidal tracts (corticospinal tract and corticobulbar tracts) may directly innervate motor neurons of the spinal cord or brainstem (anterior (ventral) horn cells or certain cranial nerve nuclei), whereas the extrapyramidal system centers on the modulation and regulation (indirect control) of anterior (ventral) horn cells that are involved in reflexes, locomotion, complex movements, and postural control.

These tracts are in turn modulated by various parts of the central nervous system, including the nigrostriatal pathway, the basal ganglia, the cerebellum, the vestibular nuclei, and different sensory areas of the cerebral cortex. All of these regulatory components can be considered part of the extrapyramidal system, in that they modulate motor activity without directly innervating motor neurons.

Compositions of extrapyramidal system :

Cortical area: premotor are (brodman’s area 6)

Subcortical areas : corpus striatum, globus pallidus , red nucleus , reticular formation , vestibular nucleus  and neocerebellum

Tracts of extra pyramidal system :

• rubrospinal tract
• pontine reticulospinal tract
• medullary reticulospinal tract
• lateral vestibulospinal tract
• tectospinal tract

Functions : 

1.      postural adjustments of the body to maintain balance

2.      gross synergistic voluntary movements in group of muscles affecting proximal joints of the limbs

3.      movement preformed unconsciously like swings of arms during walking

4.      regulatory influence over the reflex activities

Effects of lesion of extra-pyramidal system: muscle tone increased (spasticity)

Clinical relevance

Damage to the extrapyramidal system leads to different forms of movement and cognitive disorders. The majority of such movement disorders are classically described as dyskinesia. Different types of dyskinesia include myoclonus, tics, chorea, athetosis and tremors. Injury to the pyramidal system induces paralysis, whereas extrapyramidal tract disorders result in involuntary movements, muscle rigidity and immobility without paralysis. In some cases, both pyramidal and extrapyramidal systems are affected, such as spastic-athetoid cerebral palsy. Disorders which are seen with many types of extrapyramidal disease are:

• Parkinson’s disease, which is linked to dopamine deficiency in the striatum of basal ganglia. It is characterised by rigidity (increased muscle tone), bradykinesia (slowing of movements) and tremors.
• Non-spastic cerebral palsy, which could be dyskinetic or ataxic. It is caused by damage to the nerve cells outside the pyramidal tracts in the basal ganglia or in the cerebellum.
• Huntington’s disease, which is a choreiform disorder. It is caused by the degenerative process in the striatum.

Extrapyramidal symptoms including acute and tardive dyskinesias and dystonic reactions are sometimes serious side effects of antipsychotic and other drugs.

Clonus test : learn procedure with video

•      Clonus test

•      Test procedure:
With the patient supine or in a seated position, the examiner rapidly dorsiflexes the patient’s foot and holds it in that position for a few seconds.
This procedure can also be carried out at the quadriceps by stretching through the patella, and at the wrist flexors.

•      Test findings (Positive & Negative results):
The presence of clonus in a patient is a pathological finding, and warrants further investigations.
A clonus is characterised by rhythmic contractions of the muscle that is being stretched, sustained for a minimum of five seconds.

•      Considerations:
The presence of clonus is a sign of an upper motor neurone lesion, and can also appear after ingesting potent 

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