Neck: Posterior triangle and the related fascia

Neck: Posterior triangle and the related fascia
Curricular Objectives
By the end of this session students are expected to:

Theory
1. Define the Langer’s lines of the skin and outline its orientation in the neck
2. Describe the superficial fascia of the neck and acknowledge its content
3. Describe the location, attachment, nerve supply & clinical importance of platysma
4. Outline the formation, course and termination of the two superficial veins of neck
5. Summarize the surface markings and clinical importance of external jugular vein
6. Review the boundaries of the posterior triangle and its subdivisions
7. Name the fascia forming the roof of the triangle and summarize its attachment
8. List the content of the triangle and define the nerve point of the neck
9. Review the cutaneous branches of the cervical plexus and their courses
10. Outline the course and the structures supplied by the spinal accessory nerve
11. Name the structures forming the floor of the triangle
12. Describe the lower and lateral extension of the fascial carpet of triangle

Practical
1. Mark the dermatomal areas of the cervical skin
2. Identify the platysma muscle, recall its nerve supply and the fascia enclosing it
3. Trace the two superficial veins of the neck (from formation to termination)
4. Follow the boundaries of the posterior triangles and recognize its fascial roof
5. Locate the occipital & subclavian triangles & the inferior belly of omohyoid muscle
6. Trace the 4 cutaneuos branches of the cervical plexus and the accessory nerve
7. Locate the nerve point of the neck and its surface marking
8. Identify the brachial plexus and the subclavian artery
9. Distinguish the muscles forming the floor of the triangle
Selected references and suggested resources
? Clinical Anatomy by Regions, Richard S. Snell, 9th edition
? Grant s Atlas of Anatomy, 13th Edition
? McMinn s Clinical Atlas of Human Anatomy, 7th Edition
? Anatomy for Babylon medical students (facebook page)
? Human Anatomy Education (facebook page)
? Human anatomy education (you tube channel)

Session check list
? Clinical highlights
? The most common cause of swelling in the posterior triangle is supraclavicular lymph nodes enlargement
? Examination of jugular venous pressure is commonly required during physical examination of cardiac patient

? Skin
? What is the direction of tension lines (Langer’s lines) of the neck?
? What is the clinical importance of these lines?

? Superficial Fascia
? Thin layer, encircling the neck
? Although thin, it contains a number of important structures.
1. Platysma muscle
2. Superficial veins of the neck
3. Superficial cervical lymph nodes
4. Cutaneous nerves of the neck

? Platysma
? Shape: thin broad sheet
? Task 1: Use lab facilities to respond to the followings
? The muscle is attached to ___________________
? It covers parts of the two main triangles of neck. identify them

? Superficial Veins
? There are only two veins, External jugular, and Anterior jugular
1. External Jugular Vein (EJV)
? Task 2: Use lab facilities to respond to the followings
? Where and how the vein begins?
? What is the relation between the vein and the sternocleidomastoid muscle?
? After piercing the deep fascia of neck, it terminates into __________________ vein

2. Anterior jugular vein
? Is a tributary of the EJV
? Right and left veins run in a vertical course near to midline
? Task 3: Use lab facilities to respond to the followings
? Where and how the vein begins?
Answer: It begins just below the chin, by the union of several small veins.
? Right and left veins are joined together by which vein?
Answer: jugular arch
? Notice the lateral turn of the vein and indicate which surface marking lies near to it?
Answer: suprasternal notch
? When approaching the EJV it passes _____________ to sternomastoid. (superficial/deep)

? Investing layer of deep cervical fascia
? This layer of deep cervical fascia surrounds the neck
? It covers (roof) the anterior and posterior triangles
? It split to enclose two muscles. Name them






? Posterior Triangle
? Location: side of the neck
? Boundaries:
1. Trapezius (anterior border)
2. Sternocleidomastoid (posterior border)
3. Clavicle (middle third)
? Subdivisions: the inferior belly of omo-hyoid muscle divides the triangle into
1. Occipital triangle above
2. Supraclavicular triangle below
? Floor:
• The floor is covered by the prevertebral fascia (fascial carpet)
• Structures covered by the prevertebral fascia include (form above down):
1. Semispinalis capitis (may be seen)
2. Splenius capitis
3. Levator scapulae
4. Scalenus medius / posterior
5. Trunks of brachial plexus
6. Subclavian artery (3rd part)
7. Scalenus anterior
• The prevertebral fascia continues with the brachial plexus and the 3rd part of subclavian artery as they are entering the axilla to form the axillary sheath
? Content:
• Most important contents:
1. Spinal accessory nerve
2. Third part of subclavian artery
3. Brachial plexus (cervical part)
4. Lymph nodes (group of deep cervical LNs)
• All the structures lie deep to the fascial carpet of the triangle except the accessory N.

? Task 4: Use lab facilities to respond to the followings
1. Identify the inferior belly of omohyoid muscle and follow it to its attachment
2. Trace the boundaries of the two subdivisions of the posterior triangle
3. Distinguish the structures forming the floor of the triangle

? Spinal accessory nerve (within posterior triangle)
? Run from the posterior border of sternomastoid to the anterior border of trapezius
? It is closely related to deep cervical lymph nodes.
? It is adherent to the deep aspect of the fascial roof of this triangle

? Subclavian artery
? Just behind the scalenus anterior
? Closely related to the lower trunk of the brachial plexus

? Nerve point of the neck
? At the junction of the upper & middle third of posterior border of sternomastoid muscle
? The four cutaneous nerves of the cervical plexus and the spinal accessory nerve emerge
Lab Check List
A- Fascia of the neck
? Superficial Fascia
• Platysma
• External Jugular Vein/ Anterior Jugular Vein
? Deep fascia of the neck
• Investing layer/ Prevertebral layer (strong)/ Axillary Sheath
B- Posterior triangle of the neck
1. Cutaneous branches of the cervical plexus
• Lesser occipital nerve (C2) : run up along the posterior border of …….
• Great auricular nerve (C2, 3, mostly 2)
• Transverse cervical nerve (C2, 3): cross transversely superficial to….….. muscle
• Supraclavicular nerve (C3, 4, mostly 4) : to the chest by crossing superficial to … bone
2. Inferior belly of omohyoid
3. Occipital triangle/Supraclavicular triangle
4. Accessory nerve
5. Subclavian artery (3rd part)
6. Brachial plexus
7. Semispinalis capitis/ Splenius capitis/ Levator scapula/ Scalene muscles

Review questions:
1. What area of skin supplied by C1 spinal nerve?
2. In operations on the posterior triangle, if the fascial carpet is left intact, all the important contents are safe except the accessory nerve. Explain why?
3. Superficial veins of the neck lie ____________________ to platysma. (superficial/deep)

Homework 1:
Surgical incisions of the neck may involve cutting the platysma muscle. Considering the direction of the fibers and the attachment of the muscle, what will be the consequences of not suturing the muscle ends when closing the wound?

Homework 2:
A fourth year medical student is required to examine a patient with distended neck vessel. He has to decide if the vessel is the EJV.
? What surface landmarks he can choose to indicate the course of the external jugular vein?
? What can the patient do to make the vein more visible?
? If distended, this vein can be easily seen on the neck. Why?
? In some people the vein is not easily seen. Who are they?

Homework 3:
While you are attending a surgical operation on the posterior triangle of the neck, the surgeon asked you few questions to check you knowledge about the anatomy of the region.
? Which part of the triangle is NOT covered by the platysma muscle?
? What are the roof layers incised to expose the content of the triangle?
? Which layer needs to be incised before the brachial plexus can be seen?
? What is the consequence of injuring the accessory nerve during this operation?