External Spinal Cord (Surface, Segments, Spinal Nerve, Enlargements, Reflex Arch) - Anatomy

Content:
0:00 Introduction
1:07 Topography of Spinal Cord
2:44 External Surface of Spinal Cord
3:41 Spinal Segments
5:15 Spinal Nerve and Vertebral Canal
7:33 Enlargements of the Spinal Cord
8:27 Spinal Nerve Anatomy
14:13 Reflex Arch

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Topography of Spinal Cord (Medulla Spinalis)
- Vertebral Canal (Canalis Vertebralis)
- Covered by:
○ Pia Mater
○ Arachnoid Mater
○ Dura Mater
- Foramen Magnus to L1/L2
- 40-45 cm long
- Medullary Cone (Conus Medullaris)
- Filum Terminale (Terminal Thread)
- Cauda Equina

External Surface of Spinal Cord:
- Anterior Surface
○ Anterior Median Fissure (Fissura Mediana Anterior)
○ Right Anteriolateral Sulcus (Sulcus Anterolateralis Dexter)
○ Left Anterolateral Sulcus (Sulcus Anterolateralis Sinister)
- Posterior Surface
○ Posterior Median Sulcus (Sulcus Medianus Posterior)
○ Right Posterolateral Sulcus (Sulcus Posterolateralis Dexter)
○ Left Posterolateral Sulcus (Sulcus Posterolateralis Sinister)

Segments of the Spinal Cord
- 8 cervical segments
- 12 thoracic segments
- 5 lumbar segments
- 5 sacral segemnts
- 1 coccygeal segments
- Spinal nerves going out throguh Intervertebral Openings (Foramina Intervertebralis)

Relationship between the spinal cord and the vertebra:
- Spinous processes of cranial cervical vertebrae
Correspond to same segment
- Spinous processes of caudal cervical vertebrae
- Segment +1
(e.g. vertebra C7 = spinal segment C8)
- Spinous processes of cranial thoracic vertebrae
– segment + 2
(e.g. vertebra T3 = spinal segment T5)
- Spinous processes of caudal thoracic vertebrae
– segment + 3
- Vertebrae T10–T12
– lumbar segments L1–L4
- Vertebrae T12–L1 (epiconus)
– lumbar and sacral segments L5–S2
- Vertebrae L1–L2 (conus)
– sacral and single coccygeal segments S3–S5 and Co

Enlargements of the Spinal Cord
- Cervical Enlargement (Intumenencia Cervicalis)
○ Brachial Plexus
- Lumbosacral Enlargement (Intumenencia Lumbosacralis)
○ Sacral and Lumbar Plexuses

Anatomy of the Spinal Nerve:
- Spinal Nerves synapse with nuclei in gray matter of spinal cord
- Posterior Root / Sensory Root (Radix Sensoria)
○ Enter through the posterolateral sulci
○ Spinal Ganglion / Dorsal Root Ganglion (Ganglion sensorium nervi spinalis)
○ Pseudounipolar neurons
- Anterior Root / Motor Root (Radix Motoria)
○ Enter throguh the anterolateral sulci
- Spinal Nerve contain:
○ Sensory Fibers
○ Motor Fibers
○ Sympathetic Fibers (Between C8-L2)
○ Parasympathetic Fibers (Between S2-S4)
- Branches of the Spinal Nerve
○ Ventral Branch
§ Cervical Plexus
§ Brachial Plexus
§ Lumbar Plexus
§ Sacral Plexus
○ Dorsal Branch
○ White Ramus Communicans
○ Meningeal Branch

Reflex Arch
- Mono-Synaptic Reflex
○ Patellar Tendon Reflex
- Multi-Synaptic Reflex
○ Withdrawal Reflex

Sources used in this video:
- Memorix Anatomy 2nd Edition by Hudák Radovan (Author), Kachlík David (Author), Volný Ondřej (Author)
- Biorender
- University notes and lectures