Spinal Nerves.pdf
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Spinal Nerves Peripheral Nervous System (PNS) connects the CNS to the body, conducting impulses. Comprises 31 pairs of nerves: o 8 cervical nerves o 12 thoracic nerves o 5 lumbar nerves o 5 sacral nerves Voluntary & Involuntary Actio...
Spinal Nerves Peripheral Nervous System (PNS) connects the CNS to the body, conducting impulses. Comprises 31 pairs of nerves: o 8 cervical nerves o 12 thoracic nerves o 5 lumbar nerves o 5 sacral nerves Voluntary & Involuntary Actions Voluntary (somatic): Actions like picking up objects. The somatic nervous system consists of afferent nerves or sensory nerves and efferent nerves or motor nerves Involuntary (autonomic): Includes bodily functions such as heart rate and digestion. Sympathetic Nervous System: Responsible for 'fight or flight' response, increasing blood flow to muscles, heart rate, and blood pressure. Parasympathetic Nervous System: Promotes 'rest and digest' functions, directing blood flow to digestion and maintaining lower heart rates. Also maintains and restores the energy Plexuses Cervical plexus: Nerve connections to head, neck, and shoulder. Brachial plexus: Supplies skin and musculature of upper limbs, forearm and hands Lumbar plexus: Supplies the back, abdomen, and lower limbs, abdomen, groins, knees Sacral plexus: Innervates pelvis, buttocks, and lower legs, calves, feet Cervical Nerves 7 cervical vertebrae but 8 cervical nerves (C1-C8); C8 emerges below C7. Cervical plexus (C1-C4) consists of: o Motor branches: Innervate neck and diaphragm muscles. § Phrenic nerve (C3-C5): Crucial for diaphragm innervation. o Sensory branches: Provide sensation to neck, upper thorax, scalp, and ear. Posterior distribution: suboccipital nerve (C1) Greater occipital nerve (C2) Third occipital nerve (C3) Anterior distribution: Cervical plexus (C1-C4) Branchial plexus (C5-T1) Cervical Nerves 7 Cervical vertebrae (C1-C7) BUT 8 Cervical nerves (C1-C8) C8 – emerges below C7 vertebrae Cervical Plexus (C1-C4) 2 groups – Muscular and sensory Cervical Plexus (C1-C4) – Motor branches Motor branches Located deeper than sensory branches Supply muscle of neck, back and diaphragm Phrenic nerve Arises from C3-C5 Motor innervation for the diaphragm https://www.sciencedirect.com/topics/engineering/phrenic-nerve C1. C2 and C3 Innovate: Sternohyoid muscle Sternothyroid muscle Omohyoid muscle (Via Ansa Cervicallis) Ansa Cervicallis Loop of nerves Part of the cervical plexus https://teachmeanatomy.info/neck/muscles/infrahyoid/ Sternohyoid - The hyoid bone is located below the mandible, or lower jaw, and is a 'U' shaped bone that is partially responsible for tongue movement and the action of swallowing. Sternothyroid - The main function of the sternothyroid is to depress the larynx. This is important for mastication, or chewing, as well as swallowing. This raising and lowering of the larynx can also affect vocal range, the ability to control pitch, and volume. Omohyoid muscle – depresses the hyoid bone (in conjunction with Sternohyoid muscle) The ansa cervicalis (or ansa hypoglossi in older literature) is a loop of nerves that are part of the cervical plexus. Its name means "handle of the neck" in Latin. Branches from the ansa cervicalis innervate most of the infrahyoid muscles, including the sternothyroid muscle, sternohyoid muscle, and the omohyoid muscle. Other minor branches Supply muscle of neck and back C2-C3: Prevertebral muscles and sternocleidomastoid C3-C4: Levator scapulae, trapezius and scalenus mediu Cervical Plexus (C1-C4) – sensory branches Enter skin at posterior boarder of the sternocleidomastoid (Erb’s point) Supply the skin of the neck, upper thorax, scalp and ear Erb’s point – utilised when performing a cervical plexus nerve block Usually for surgery to the neck region ie thyroidectomy or cervical lymph node excision Warning: close to the phrenic nerve so can affect it and respiration! Greater Auricular nerve (C2,C3) Sensation to external ear Sensation over parotid gland Transverse Cervical nerve (C2.C3) Sensation to anterior neck Lessor Occipital nerve (C2) Sensation to posterosuperior scalp Supraclavicular nerves (C3,C4) Sensation over supraclavicular fossa Sensation upper thoracic region and stenoclavicular joint https://neupsykey.com/plexuses/ Brachial plexus (C5-T1) Network supplies skin and musculature of upper limb Begin in the neck, passes through axilla to the upper extremities Divided into 5 parts Roots, Trunks, Divisions, Cords, Branches Read That Damn Cadaver Book Brachial Plexus Comprises roots (C5-T1), trunks, divisions, cords, and branches. Superior trunk: C5-C6; Middle trunk: C7; Inferior trunk: C8-T1. Major branches include: o Musculocutaneous Nerve: Innervates biceps and brachialis. o Axillary Nerve: Innervates deltoid and teres minor. o Median Nerve: Innervates flexor muscles and sensation to lateral palm. o Radial Nerve: Innervates triceps and sensory to posterior arm. o Ulnar Nerve: Innervates hand muscles and provides sensation to medial fingers. Roots Each pair leave the spinal cord via intervertebral foramina Each pair divides in to posterior and anterior ramus Posterior innervate the skin and muscle of the back https://teachmeanatomy.info/upper-limb/nerves/brachial-plexus/ Trunks and divisions At the base of the neck the roots converge to form 3 trunks Superior trunk – C5 and C6 roots Middle trunk – C7 roots Inferior trunk – C8 and T1 roots Within the posterior triangle of the neck, each trunk divides into 2 branches 1 anteriorly, 1 posteriorly Each passes through the axilla Cords Once in the axilla they recombine to make 3 cords Named due to their position to the axillary artery The lateral cord is formed by: The anterior division of the superior trunk The anterior division of the middle trunk The posterior cord is formed by: The posterior division of the superior trunk The posterior division of the middle trunk The posterior division of the inferior trunk The medial cord is formed by: The anterior division of the inferior trunk. Branches 5 major branches Musculocutaneous Nerve (C5, C6, C7) innervates: brachialis, biceps brachii Sensory functions: lateral half of anterior forearm, small portion of posterior forearm Axillary Nerve (C5, C6) innervates: Teres minor and deltoid muscles Sensory functions: inferior region of deltoid £regimental badge” Median Nerve (C6, C7, C8, T1) innervates: Flexor muscles in forearm, thenar muscle, index and middle fingers Sensory functions: lateral part of palm, lateral 3 ½ fingers on palmer surface of hand Radial Nerve (C5, C6, C7, C8, T1) innervates: Triceps brachii, extensors wrist and fingers Sensory functions: posterior aspect of arm and forearm, posterolateral aspect of hand Ulna Nerve (C8, T1) innervates: muscle of the hand Sensory functions: Anterior and posterior surface of medial 1 ½ fingers and associated palm area (in an exam it may give a problem of a injury site; and have to name which nerve it has been impacted) https://teachmeanatomy.info/upper-limb/nerves/brachial-plexus/ Injuries Upper brachial plexus injury (Erb's Palsy): Affects C5-C6, impairing shoulder and arm movements. Klumpke Palsy: Involves T1 root, causing hand muscle paralysis and sensory loss on medial arm. Muscles paralysed: Supraspinatus, infraspinatus, subclavius, biceps brachii, brachialis, coracobrachialis, deltoid and teres minor. Motor functions: Movements that are lost or greatly weakened include abduction at shoulder, lateral rotation of arm, supination of forearm, and flexion at shoulder. Sensory functions: Loss of sensation down lateral aspect of arm, which covers the sensory innervation of the axillary and musculocutaneous nerves. Erb’s palsy commonly occurs where there is an excessive increase in the angle between the neck and shoulder, which stretches (or even tears) the nerve roots of C5 and C6. It can occur as a result of result of a difficult birth or shoulder trauma. The affected limb hangs limply, medially rotated by the unopposed action of pectoralis major. The forearm is pronated due to the loss of biceps brachii. The wrist is weakly flexed due to the normal increased tone of the wrist flexors relative to the wrist extensors. This is position is known as ‘waiter’s tip’, and is characteristic of Erb’s palsy. A lower brachial plexus injury results from excessive abduction of the arm (e.g. person catching a branch as they fall from a tree). It has a much lower incidence than Erb’s palsy. Thoracic Nerves 12 spinal nerves (T1-T12) control upper chest, mid-back, and abdomen. Anterior division: Intercostal nerves for rib control. Posterior division: Medial branches innervate upper back skin. Thoracic Nerves 12 spinal nerves – emerge from Thoracic vertebrea (T1-T12) Branches also go direct to paravertebral ganglia of the ANS Anterior division Intercostal nerves (T1-T11) T2 and T3 – branch to intercostobrachial nerve Subcostal nerve (T12) Posterior division Medial branches (Upper 6 thoracic nerves) Pierce the rhomboid and trapezious muscle to reach the skin Called medial cutaneous ramus Function of thoracic nerves T1-T5 Affect: muscles of upper chest, mid-back and abdomen Function: Control rib cage, lungs, diaphragm T6-T12 Affect: Abdominal and back muscles Function: assist with balance, posture. Help with coughing and expel F/B from airways Injury to thoracic nerves Injury T1-T5 – usually affects, abdominal, lower back and legs Paraplegia Hands and arm function usually normal Injury T6-T12 – usually result in paraplegia Little or no control to bowel and bladder Thoracic Area of Body Affected Nerve Section T-1 Hands and fingers T-2 – T-5 Chest muscles T-6 – T-8 Chest and abdominal muscles T-9 – T-12 Abdominal muscles Lumbar Nerves 5 spinal nerves (L1-L5) form the lumbar plexus. Contains nerves like: o Iliohypogastric and Ilioinguinal: Innervate abdominal muscles and skin in the pelvic regions. o Genitofemoral: Innervates the cremasteric muscle and skin of the thigh. o Femoral: Supplies quadriceps and provides sensation to the anterior thigh. Lumbar plexus Iliohypogastric Nerve (L1, with contribution from T12) Motor Functions: Innervates the internal oblique and transversus abdominis. Sensory Functions: Innervates the posterolateral gluteal skin in the pubic region. Ilioinguinal Nerve (L1) Motor Functions: Innervates the internal oblique and transversus abdominis. Sensory Functions: Innervates the skin on the upper middle thigh. In males, it also supplies the skin over the root of the penis and anterior scrotum. In females, it supplies the skin over mons pubis and labia majora. Genitofemoral Nerve (L1, L2) Motor Functions: The genital branch innervates the cremasteric muscle. Sensory Functions: The genital branch innervates the skin of the anterior scrotum (in males) or the skin over mons pubis and labia majora (in females). The femoral branch innervates the skin on the upper anterior thigh. Lateral Cutaneous Nerve of the Thigh (L2, L3) Motor Functions: None. Sensory Functions: Innervates the anterior and lateral thigh down to the level of the knee. Obturator Nerve (L2, L3, L4) Motor Functions: Innervates the muscles: obturator externus, pectineus, adductor longus, adductor brevis, adductor magnus, gracilis. Sensory Functions: Innervates the skin over the medial thigh. Femoral Nerve (L2, L3, L4) Motor Functions: Innervates the muscles: Illiacus, pectineus, sartorius, all the muscles of quadriceps femoris. Sensory Functions: Innervates the skin on the anterior thigh and the medial leg. Sacral Nerves 5 pairs of nerves, including the sciatic nerve, which is crucial for lower limb movement and sensation. Major branches include: o Superior Gluteal Nerve: Innervates gluteus minimus and medius. o Sciatic Nerve: Tibial portion innervates posterior thigh muscles, while the common fibular portion innervates lateral and anterior leg muscles. Sacral Nerves 5 pairs of nerves Begining at cuada equina – descending into sacrum Sacral plexus and lumbosacral plexus Supply much of Hip, thigh, leg and foot Efferent and afferent fibres Sensory perception and movements of lower body ‘Some Irish Sailor Pesters Polly’. Superior Gluteal, Inferior Gluteal, Sciatic, Posterior cutaneous nerve of thigh, Pudendal Sacral plexus Superior Gluteal Nerve (L4, L5, S1) Motor Functions: Innervates the gluteus minimus, gluteus medius and tensor fascia lata. Sensory Functions: None. Inferior Gluteal Nerve (L5. S1, S2) Motor Functions: Innervates gluteus maximus. Sensory Functions: None. Sciatic Nerve (L4, L5, S1, S2, S3) Motor Functions: Tibial portion – Innervates the muscles in the posterior compartment of the thigh (apart from the short head of the biceps femoris), and the hamstring component of adductor magnus. Innervates all the muscles in the posterior compartment of the leg and sole of the foot. Common fibular portion – Short head of biceps femoris, all muscles in the anterior and lateral compartments of the leg and extensor digitorum brevis. Sensory Functions: Tibial portion: Innervates the skin on the posterolateral and medial surfaces of the foot as well as the sole of the foot. Common fibular portion: Innervates the skin on the anterolateral surface of the leg and the dorsal aspect of the foot. Sciatica – disorder to sciatic nerve Posterior Femoral Cutaneous (S1, S2, S3) Motor Functions: None Sensory Functions: Innervates the skin on the posterior surface of the thigh and leg. Also innervates the skin of the perineum. Pudendal Nerve (S2, S3, S4) Motor Functions: Innervates the skeletal muscles in the perineum, the external urethral sphincter, the external anal sphincter, levator ani. Sensory Functions: Innervates the penis and the clitoris and most of the skin of the perineum.
