Xiv / 18B01 / 17A11 – Anatomy of Tracheostomy

18B01: Exam Report

Describe the surface anatomy of the anterior neck (30% of marks) and the underlying structures relevant to performing a tracheostomy (70% of marks)

79% of candidates passed this question.

Answers required a description of the surface anatomy outlining the midline structures including the hyoid bone and cartilages. The tissue layers should have been mentioned as should the relevant tracheal anatomy.

The anterior, posterior and lateral relations of the trachea should also have been included along with the relevant nerves and blood vessels. Diagrams were not essential but could have been included.

Candidates should note that marks were not awarded for a description of how to perform a tracheostomy.

17A11: Exam Report

Outline the anatomical relations of the trachea relevant to performing a percutaneous tracheostomy

44% of candidates passed this question.

Many candidates described how to perform a tracheostomy or the structure of the trachea rather than the relevant anatomical relations.

It was expected that answers include anterior, posterior and lateral relations at the correct tracheal level including relevant vascular structures.

Xiv / 18B01 / 17A11: Anatomy of Tracheostomy

Definition

Tracheostomy = I/O a tube through the anterior neck tissue into the trachea to facilitate ventilation

Trachea

  • From Cricoid Cartilage to Level of 1° Bronchi
  • 11cm long
  • Anterior → C-shaped cartilaginous rings
  • Posterior → trachealis m.
  • 16 – 20 tracheal rings
  • 4 layers:
    1. Mucosa → ciliated pseudostratified columnar epithelium
    2. Submucosa → dense connective tissue, mucous glands
    3. Cartilaginous layer → hyaline C-shaped cart.
    4. Adventia
  • Nervous: vagus + recurrent laryngeal n.
  • Arterial: inf. thyroid arts & veins + bronchial a.

Surface Anatomy

Hyoid bone (C3)
↓
Thyroid cartilage
↓
Cricothyroid membrane
↓
Cricoid (C6)
↓
Thyroid gland (tracheal rings 2 – 4)

Relationships

Anterior

  • Skin → subcut. tissue → fat → sup. + deep fascia
  • Rings 2 – 4 covered by isthmus of thyroid gland
  • Sternohyoid + sternothyroid muscles overlap trachea
  • Superior thyroid a.
    • Arises from external carotid a. @ level of the hyoid bone
    • Passes down & ends on the thyroid gland superiorly, which overlies trachea
  • Superior, Inferior & middle thyroid v.
    • drain thyroid also & overlies trachea

Lateral

  • Sternohyoid muscles → either side
  • Anterior ∆ of neck → enclosed in carotid sheath
    • Carotid a.
    • Internal jugular v.
    • Vagus (X) n.
  • Thyroid gland
    • R & L lobes lateral to trachea
    • Isthmus over rings 2 – 4
    • Vascular supply of thyroid:
      • Inferior + superior thyroid a.
      • Inferior, superior & middle thyroid v.
    • Recurrent laryngeal n. & superior laryngeal n.
      • Comes off vagus n (CN X)
    • ⇒ Recurrent laryngeal n. → all intrinsic m. of larynx except cricothyroid muscle
    • ⇒ Superior laryngeal n. → divides into external & internal laryngeal n.

Posterior

  • Oesophagus
  • Vertebrae C6 → T4

Dissection

Skin
↓
Subcut. tissue
↓
Fat
↓
Superficial & deep fascia
↓
Fibroelastic tissue b/w tracheal rings
↓
Trachea