CN 6: Abducens Nerve (Scheme, Pathway, Clinical Relevance)

Uploaded September 2023 | Updated September 2026, 2 weeks ago

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Content:
0:00 Introduction
00:41 Abducens Nerve Scheme
01:53 Abducens Nerve Nucleus
04:05 Abducens Nerve Course
05:04 Lateral Rectus Muscle Function
06:25 Clinical Relevance
07:06 Recap

Abducens nerve is purely a motor nerve supplying the lateral rectus muscle involved in abduction of the eye

Abducens/abducent nerve Nucleus:
- Nucleus of abducens nerve (nucleus nervi abducentis)
○ Facial nerve goes around this nucleus forming the facial colliculus (colliculus facialis)
○ A somatomotor nucleus that is located in the pons innervates the lateral rectus

Course:
- Emerges from the medullopontine sulcus between the pons and medulla oblongata
- Leaves the brainstem on the ventral side
- Runs on the base of the skull, penetrates the dura mater then enter the cavernous sinus
- Enters the orbit via the superior orbital fissure and common tendinous ring
- Then innervates the lateral rectus

Function of lateral rectus muscle:
- Abduction of the eye

Hering's Law of equal innervation:
- Coordinates both eyes together, so that the medial and the lateral rectus muscle contracts equally, while deactivating the contralateral muscle through the medial longitudinal fasciculus.

Clinical Relevance:
- Abducens nerve can get compressed by a lesion or rise in intracranial pressure.
- Compression causes paralysis of lateral rectus muscle, resulting in medial deviation of affected eye, giving a fully adducted eye at rest and an inability to abduct the eye.

Sources:
- Singh, I. (2017). Human neuroanatomy (10th ed.).
Helwany M, Bordoni B. Neuroanatomy, Cranial Nerve 1 (Olfactory) [Updated 2022 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-
- Kozlowski, T. (2017). Memorix Anatomy: The Complete Study Guide. 2nd ed. Thieme Medical Publishers.

Pictures and visuals:
- Complete Anatomy
- Biorender
- Powerpoint
- Camtasia 2021

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$The Clavicle (Collarbone): Parts, Joints, and Common Injuries | Clinical Anatomy 🌐 Website: https://taimtalksmed.com/ 🫀 Help keep this content free: youtube.com/channel/UCEr7pkSXVsHcBLLBcJAGV-Q/join 🔬 Get 10% off anatomy lab models (affiliate link): https://anatomywarehouse.com?aff=34 📲 Other Links: Instagram: https://www.instagram.com/taimtalksmed/ Discord: https://discord.com/invite/DENMUpS8ey Content: 00:00 Introduction & Content 01:20 Clavicle Anatomy 03:02 Joints of the Clavicle 03:19 Sternoclavicular Joint 04:06 Acromioclavicular Joint 05:29 Why do we have a Clavicle? 07:47 Clinical Relevance 08:42 Possible causes of pain in the Clavicle 09:53 Symptoms of Clavicle Injury 10:17 Clinical Tests of Clavicle Injuries 11:01 Treatment of Clavicle Injury Clavicle (Collarbone) Anatomy | Structure, Joints & Clinical Relevance Structures covered in this video: Clavicle Anatomy – Parts: • Sternal end (Extremitas sternalis) • Acromial end (Extremitas acromialis) • Body of the clavicle (Corpus claviculae) • Sternal facet (Facies articularis sternalis) • Acromial facet (Facies articularis acromialis) • Subclavian groove (Sulcus musculi subclavii) • Conoid tubercle (Tuberculum conoideum) • Trapezoid line (Linea trapezoidea) • Impression for costoclavicular ligament Joints Formed by the Clavicle: • Sternoclavicular joint (Articulatio sternoclavicularis) • Clavicular notch of manubrium (Incisura clavicularis) • Acromioclavicular joint (Articulatio acromioclavicularis) Ligaments of the Clavicle: • Costoclavicular ligament (Ligamentum costoclaviculare) • Interclavicular ligament (Ligamentum interclaviculare) • Anterior sternoclavicular ligament • Acromioclavicular ligament • Coracoclavicular ligament • Conoid ligament (Ligamentum conoideum) • Trapezoid ligament (Ligamentum trapezoideum) • Coracoacromial ligament (Ligamentum coracoacromiale) Associated Muscles: • Subclavius • Pectoralis major • Sternocleidomastoid • Trapezius • Deltoid Neurovascular Structures Protected by the Clavicle: • Brachial plexus • Subclavian artery • Subclavian vein Functional Anatomy: • Clavicle as a strut • Force transmission from upper limb to axial skeleton • S-shape acting as a shock absorber • Scapular suspension and positioning Clinical Anatomy and Conditions Discussed: • Clavicle fracture (Middle third most common) • Clavicle dislocation • Acromioclavicular joint injury • AC joint step-off • Cross-body adduction test • Piano key sign • OBrien’s test • Sternoclavicular joint dislocation or arthritis • Distal clavicular osteolysis (Weightlifter’s shoulder) • Cleidocranial dysplasia (Absence of clavicle) • Neurovascular injury signs (Pulse, cap refill, sensory loss) Imaging Techniques Mentioned: • AP clavicle X-ray • CT scan for subtle fractures or joint evaluation • MRI for osteolysis or soft tissue pathology • Chest X-ray to rule out associated rib fractures or pneumothorax Treatment Options: • Conservative management (sling, NSAIDs, physiotherapy) • Surgical fixation (for displaced or unstable fractures) • Grading of AC joint injuries (Type I–III) • Distal clavicle excision (arthroscopic or open) Sources: • Kozlowski, T. (2017). Memorix Anatomy, 2nd ed. • Standring S. (2020). Gray’s Anatomy, 42nd edition • Tubbs RS, Shoja MM, Loukas M. (2016). Bergman’s Encyclopedia of Human Anatomic Variation • White TD, Folkens PA. (2005). The Human Bone Manual Programs used: Complete Anatomy, Biorender, PowerPoint$

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