Page-by-Page Anatomy Notes: Back Muscles, Erector Spinae, Transversospinalis Group, and Lower Limb Plexuses

Page 1

• Muscles of the Back – Trapezius m.
  • Origin: Occipital bone, EOP (inion), Superior nuchal line; Ligamentum nuchae; SPs $C7, T1{-}T12$
  • Insertion: Lateral 1/3 of clavicle; Acromion; Spine of scapula
  • Nerve Supply: Spinal Accessory nerve; $C3, C4$
  • Action: Retracts shoulders
  • Blood Supply: Descending scapular a.; A descending branch of either the superficial cervical a. or [text truncated]

Page 2

• Latissimus Dorsi in. (muscle)
  • Origin: SPs of $T7{-}T12$ & $L1{-}L5$; Sacral tubercles; Iliac crest; Lower 3 or 4 ribs; Inferior angle of scapula
  • Insertion: Medial lip of bicipital groove of humerus
  • Nerve Supply: Thoracodorsal n.
  • Action: Extends, adducts, and medially rotates arm
  • Blood Supply: Descending scapular a.

Page 3

• Layer II. Levator Scapulae m.
  • Origin: TP's $C1{-}C4$; posterior tubercle
  • Insertion: Vertebral border of scapula between medial angle and root of spine
  • Nerve Supply: Dorsal Scapular n.
  • Action: Elevates scapula
  • Blood Supply: Descending Scapular A.

Page 4

• Rhomboid Minor m.
  • Origin: Ligamentum nuchae; SPs $C7, T1$
  • Insertion: Root of spine of scapula
  • Nerve Supply: Dorsal Scapular n.
  • Action: Adducts, and medially rotates scapula
  • Blood Supply: Descending scapular A.

Page 5

• (No content provided in transcript for Page 5; notes incomplete.)

Page 6

• Rhomboid Major m.
  • Origin: TP's of $T2{-}T5$
  • Insertion: Vertebral border of scapula between root of spine and inferior angle
  • Nerve Supply: Dorsal Scapular n.
  • Action: Adducts and medially rotates scapula
  • Blood Supply: Descending scapular a

Page 7

• Layer III. Posterior Serratus Superior m.
  • Origin: Ligamentum Nuchae; SPs $C7, T1, T2$
  • Insertion: 2nd, 3rd, and 4th rib just posterior to the angle of the rib
  • Nerve Supply: $T13$ VPR, $C8{-}T3$ VPR
  • Action: Elevates ribs (inspiration)
  • Blood Supply: Posterior intercostal aa.

Page 8

• Posterior Serratus Inferior m.
  • Origin: SPs $T11, T12, L1, L2$; Lumbar Fascia
  • Insertion: Lower 4 ribs
  • Nerve Supply: VPR $T9{-}T11$
  • Action: Depresses ribs (expiration)
  • Blood Supply: Posterior intercostal aa.

Page 9

• Levatores Costarum m. (12 Pairs)
  • Origin: TP's $C7, T1{-}T11$
  • Insertion: On rib below origin, between tubercle and angle of rib
  • Nerve Supply: C8{-}T11 DPR
  • Action: Rotates and laterally flexes vertebral column; elevates ribs (inspiration)
  • Blood Supply: Posterior intercostal aa.

Page 10

• (No content provided in transcript for Page 10; notes incomplete.)

Page 11

• Laver IV. Erector Spinae Group
  • Origin: Common origin (common tendon mass); Thoracolumbar fascia
  • 1) Posterior surface of sacrum and iliac bones
  • 2) Sacrospinalogic? posterior sacroiliac
  • 3) SPs $T11, T12, L5$
  • Nerve Supply: DPR
  • Action: Bilaterally extend the spine; Unilaterally rotate and lateral flex the spine
  • Blood Supply: Subcostal aa.; Lumbar aa.

Page 12

• Common tendon Mass
• Sacrotuberous Lig.

Page 13

• Erector Spinae Group (continued) – Iliocostalis Lumborum m.
  • Origin: Common tendon mass
  • Insertion: Lower 6 or 7 ribs
  • Nerve Supply: DPR
  • Action: Bilaterally extension of spine; Unilaterally rotation and lateral flexion
  • Blood Supply: Subcostal aa.; Lumbar aa.

Page 14

• Iliocostalis Thoracis m.
  • Origin: Lower 6 or 7 ribs
  • Insertion: Upper 6 ribs
  • Nerve Supply: DPR
  • Action: Bilaterally extension of spine; Unilaterally rotation and lateral flexion
  • Blood Supply: Subcostal, lumbar, and posterior intercostal aa.
• Iliocostalis Cervicis m.
  • Origin: angle of the upper 3{-}6 ribs
  • Insertion: TP's $C4, C5, C6$
  • Nerve Supply: DPR
  • Action: extension of spine
  • Blood Supply: branches of subclavian artery

Page 15

• (No content provided in transcript for Page 15; notes incomplete.)

Page 16

• Longissimus Thoracis m.
  • Origin: Common tendon mass
  • Insertion: Lower 9 or 10 ribs and their corresponding vertebrae (TP) (double attachment)
  • Nerve Supply: DPR
  • Action: Bilaterally extension of spine; Unilaterally rotation and lateral flexion
  • Blood Supply: Posterior intercostal aa.
• Longissimus Cervicis m.
  • Origin: TP's $T1{-}T4$(5)
  • Insertion: TP's $C2{-}C6$
  • Nerve Supply: DPR
  • Action: Bilaterally extends the spine; Unilaterally rotation and lateral flexion
  • Blood Supply: branches of the subclavian art.

Page 17

• Longissimus Capitis m.
  • Origin: TP's $T1{-}T4(5)$; Purportedly TP's $T1{-}T4/5$
  • Insertion: Mastoid process
  • Nerve Supply: DPR
  • Action: Bilaterally extension of spine; Unilaterally rotation and lateral flexion of spine
  • Blood Supply: branches of the subclavian art.
• Spinalis Thoracis m.
  • Origin: SPs $T11, T12, L1, L2$
  • Insertion: SPs $T1{-}T4/8$
  • Nerve Supply: DPR
  • Action: Bilaterally extension of spine; Unilaterally rotation and lateral flexion
  • Blood Supply: post intercostal aa.

Page 18

• Spinalis Cervicis m.
  • Origin: SPs $C7, T1, T2$; lower part of ligamentum nuchae
  • Insertion: SPs $C2$ (or $C3, C4$)
  • Nerve Supply: DPR
  • Action: Bilaterally extension of spine; Unilaterally rotation and lateral flexion
  • Blood Supply: branches of the subclavian art.

Page 19

• (No content provided in transcript for Page 19; notes incomplete.)

Page 20

• Layer V. Transversospinalis Group
  • Rotatores mm. (short, deep to multifidi)
  • Multifidi mm.
  • S = semispinalis mm.

Page 21

• Semispinalis Thoracis m.
  • Origin: TP's $T6{-}T12$
  • Insertion: SPs $C6, C7, T1{-}T4$
  • Nerve Supply: DPR
  • Action: Lateral flexion of spine; Extension of head; Extension of ribs
  • Blood Supply: post intercostal aa.
• Semispinalis Cervicis m.
  • Origin: TP's $T1{-}T6$
  • Insertion: SPs $C2{-}C5$
  • Nerve Supply: DPR
  • Action: Lateral flexion of spine; Extension of head; Extension of ribs
  • Blood Supply: branches of the subclavian art.

Page 22

• Semispinalis Capitis m. (Strongest muscle in back of neck)
  • Origin: AP's $C4, C5, C6$; TP's $C7, T1{-}T6$
  • Insertion: Occipital bone
  • Nerve Supply: DPR
  • Action: Lateral flexion of spine; Extension of head; Extension of ribs
  • Blood Supply: branches of the subclavian art.

Page 23

• (No content provided in transcript for Page 23; notes incomplete.)

Page 24

• Multifidi mm. (Prominent in L/S area)
  • Origin: Posterior sacrum; Posterior sacroiliac ligament; Mammillary processes in lumbar spine; TP's in thoracic spine; AP's $C4{-}C7$
  • Insertion: SP of vertebra above origin
  • Nerve Supply: DPR
  • Action: Aids in extension, rotation, and lateral flexion of vertebral column
  • Blood Supply: see earlier blood supplies for each region
• Rotatores mm. (11 small pairs; deep to multifidi)
  • Origin: TP's of thoracic vertebrae
  • Insertion: Lamina of vertebra above origin (short rotators) or lamina of 2 vertebrae above (long rotators)
  • Nerve Supply: DPR
  • Action: Rotation of spinal column
  • Blood Supply: see earlier blood supply (prominent in thoracic area)

Page 25

• Layer VI. Intersegmental mm.
  • Interspinalis mm. Cervical: 6 pairs; Lumbar: 4 pairs
  • SP
  • Origin: SP of vertebra
  • Insertion: SP of adjacent vertebra
  • Nerve Supply: DPR or VPR or both
  • Action: Extension of spine
  • Blood Supply: See earlier blood supplies
• Intertransversarii mm.
  • TP to TP
  • Origin: TP of vertebrae
  • Insertion: Ipsilateral TP of adjacent vertebrae
  • Nerve Supply: DPR or VPR or both
  • Action: Lateral flexion of spine
  • Blood Supply: See earlier blood supplies
• Note: Longissimus forms the bulk of the erector spinae.

Page 26

• (No content provided in transcript for Page 26; notes incomplete.)

Page 27

• LOWER EXTREMITY – LUMBAR PLEXUS
  • T12, L1–L4; VENTRAL PRIMARY RAMI ONLY; L2 is also included in sacral plexus
  • Supplies anterior & medial thigh; posterior abdominal wall muscles
  • Muscles included: Psoas, Iliacus, Quadratus Lumborum
  • (1) Subcostal Nerve – Motor: to abdominal muscles (especially transversus abdominis m.); Sensory: from T12 dermatome (directly above inguinal ligament)

Page 28

• (No content provided in transcript for Page 28; notes incomplete.)

Page 29

• (2) Iliohypogastric Nerve – Motor: internal oblique m.; Sensory: $L1$ dermatome
• (3) Ilioinguinal Nerve – Sensory: from inguinal canal within spermatic cord; $L1$ dermatome

Page 30

• (No content provided in transcript for Page 30; notes incomplete.)

Page 31

• (4) Genitofemoral Nerve – Pierces psoas muscle and runs on top of it
  • A) Femoral Part: Sensory to anterior thigh
  • B) Genito Part (within the spermatic cord) to the cremaster muscle
  • Commentary: This is the middle covering of the spermatic cord; this nerve is responsible for the cremasteric reflex in males (cremasteric muscle contracts when the skin of thigh/navel is stimulated, causing the testes to ascend). In females there is a homologous reflex called the Geigle's reflex (scratch thigh/navel)

Page 32

• (No content provided in transcript for Page 32; notes incomplete.)

Page 33

• (5) Lateral Femoral Cutaneous N. – Sensory: Lateral thigh; Superior gluteal region
• (6) Femoral Nerve – Largest nerve in lumbar plexus
  • Motor: Anterior thigh; Posterior abdominal muscles
  • Sensory: Anterior thigh; Medial & anterior leg (Saphenous nerve)
• (7) Obturator Nerve – Passes through obturator foramen
  • Motor: Adductors of hip
  • Sensory: Medial thigh
• (8) Accessory Obturator Nerve – (Often absent)
  • Motor: Adductors of hip
  • Sensory: Medial thigh

Page 34

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Page 35

• Sacral Plexus – Largest plexus of all the plexi
  • Ventral primary rami (VPR): $L4{-}S4$
  • Innervates pelvis & lower extremities (PS S234)

Page 36

• Posterior view of right leg
  • Structures: Sciatic nerve, Knee, Leg; Piriformis m (key muscle)
  • Why? Sciatica – inflammation of sciatic nerve due to irritation of nerve roots
  • Branches: Common Peroneal nerve, Tibial nerve; Fibula; Superficial peroneal n.; Deep peroneal nerve

Page 37

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Page 38

• (1) Sciatic Nerve
  • Motor: to hamstrings
  • Sensory: to posterior thigh
  • Nerve divides into:
  • Tibial Nerve (most medial)
    • Motor: posterior leg; plantar muscles of foot
    • Sensory: posterior leg; plantar surface of foot
  • Common Peroneal Nerve (more lateral)
    • Superficial Branch → Superficial Peroneal Nerve: Motor: lateral leg muscles; Sensory: lateral leg
    • Deep Peroneal Nerve: Motor: anterior leg muscles; Sensory: anterior leg

Page 39

• (No content provided in transcript for Page 39; notes incomplete.)

Page 40

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Page 41

• (2) Superior Gluteal Nerve – Motor: Gluteus Medius; Gluteus Minimus; Tensor Fascia Lata (abduction of leg & thigh)
• (3) Inferior Gluteal Nerve – Motor: Gluteus Maximus
• (4) Posterior Femoral Cutaneous Nerve – Sensory: skin of buttocks & posterior thigh

Page 42

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Page 43

• (5) Nerve to the Obturator Internus & Superior Gemellus M.
• (6) Nerve to the Inferior Gemellus & Quadratus Femoris M.
• (7) Nerve to the Piriformis M.
• Pudendal Nerve – Innervates skeletal muscle
  • A) Inferior Rectal Nerve (Inferior Hemorrhoidal Nerve) – Motor: Anal sphincter, lining of anal canal; Sensory: skin around anus
  • B) Perineal Nerve – Motor: to superficial perineal space (urogenital diaphragm); Controls micturition and defecation; Sensory: posterior scrotum, labia majora

Page 44

• C) Dorsal Nerve of the Penis (Clitoris) – Innervates glans penis and glans clitoridis; Responds to mechanical stimulation
• Dorsal nerve of penis – mechanical stimulation; PS S2-4; Erection; Orgasm
• Pelvic Splanchnic Nerve (Nervi Erigentes) – PS S2-3-4; Controls bladder, rectum, external genitalia, rectum