Lecture 9 & 10: Anterior Triangle Flashcards
- Superior thyroid vein
- Middle thyroid vein
(both drain to int. jugular)
- Inferior thyroid vein (drains to brachiocephalic)
A: Region V
B: Region III
C: Region VI
D: Region IV
E: Region II
F: Region I
What are the four reasons for knowing the anterior triangle?
- Thyroid examination
- Central vein catheterisation
- Penetrating trauma
- Cricothyroidotomy / Tracheastomy
Define the ant. triangle:
The region beyond the ant. border of sternocleidomastoid to the midline.
Top: Inf border of mandible
Post: Ant. border of sternocleidomastoid(s)
Imaginary midline defines left and right.
Describe the superifical veins of the ant. triangle:
Many many superficial veins branch out of the anterior triangle.
What are the infrahyoid muscles of the ant. triangle?
Superficial:
- Sternohyoid + Omohyoid
- Thyrohyoid + Sternothyroid
Deep??
What provides innervation to the anterior triangle muscles?
Ansa cervicalis (comes off the cervical plexus), consists of:
- Superior root of ansa cervicalis (C1)
- Inferior root of ansa cervicalis (C2+C3)
These provide motor innervation to all muscles in ant. triangle EXCEPT: Thyrohyoid (C1+C12 do this)
What provides cutaneous innervation of the cervical plexus?
- Transverse cervical n.
- Supraclavicular nerve
- Lesser occipital n.
- Great auricular n.
Describe how you can examine the thyroid:
- Exists actually above jugular notch. People often mistake thyroid cartilage
- Sitting on 2+3rd cartilage rings
- (If short neck then they need to extend neck)
- lateral lobes might come up to thyroid cartilage
Describe the arterial supply of the thyroid:
Dual supply.
- Subclavian (inf. thyroid art.)
- Ext. carotid (sup. thyroid art)
Describe the lymphatic drainage of the thyroid and internal triangle:
Paratracheal nodes drain to deep cervical nodes. (posteroinf. group)
But part of thyroid drains directly into cervical lymph nodes
Describe the innervation of the thyroid:
SNS: Middle cervical ganglion (runs with vertebral art)
PNS: Vagus (Recurrent laryngeal n. (sits betweem trachea and oesophagus in recurrent laryngeal groove once comes of vagus)
[Central lobe sits close to cartoid sheath]
Whats found in the carotid sheath?
Int jugular, internal carotid, vagus nerve
Whats important when it comes to the embryology of the thymus?
Formed in the foramen cecum and migrates through the tract of thyroglossal duct to its normal postion
It can leave behind residual tissue as it migrates. Patent duct can trap food and cause bad breath
Describe the midline to lateral and superficial to deep suprahyoid muscles:
Midline ——————–> Lateral
Superficial: Ant belly digastric -> Post belly digastric
Mylohyoid muscle -> Stylohyoid muscle
Deep: Geniohyoid muscle…………………..
Where does the mylohoid originate and insert?
L+R meet @ midline (Raphe // Tendinous sheath)
Attatches along mylohyoid line (mandible)
What contributes to formation of the carotid sheath:
3 contributions (deep fascia)
- Investing
- Pre-vertebral
- Pre-tracheal
Describe the venous structure of the face:
All vessels drain back to the external or internal jugular via retromandibular or facial vein.
Describe the pathway of the vagus nerve:
Exits the skull : Jugular foramen
Travels through the: Carotid sheath
At the root of neck: Crosses ant. scalene close to midline (phrenic follows ant. scalene close to vagus)
Gives off branches: Carotid body branch, cardiac branch, laryngeal nerve (int and ext. branches). Pharyngeal branch.
Describe the pathway of the CN (IX):
Exits the skull : Jugular foramen
Travels through: Carotid sheath (but exits after ~2cm b/c goes to post. aspect of tongue) (Sits deep to belly of digastric and stylohyoid) (Runs between int and ext. carotid)
Gives off branches: Carotid sinus branch, pharyngeal breanch
Describe the pathway of the accessory nerve:
Exits the skull: Jugular foramen
Travels through: Carotid sheath ( Exits post. aspect, runs under sternocleidomastoid through the post. triangle b.c headding to trap)
Gives off branches to: Sternocleidomastid, Trapzius
Describe the pathway of the hypoglossal nerve:
Exits the skull : Hypoglossal canal
Travels through;
- Sits deep to post. belly of digastric
- Stylohyoid
- Hooks AROUND occipital art.
- Superficial to int/ext carotid
Gives off:
- C1 branch (Innervates thyrohyoid m.) & sends branch to ansa cervalis (deep to carotid sheath)
- Branch to tongue
Where does central vein cathierisation typically occur?
B/w clavicular and sternal heads of sternocleidomastoid
Avoids post. triangle which is filled with nerves.
- Hyoid bone
- Thyroid cartilage
- Thyroid
