1314 THE SKIN, MAMMAH^Y GLANDS AND DUCTLESS GLANDS 



The pyramidal lobe is usually a narrow elongated flattened somewhat conical 

 process of thyreoid tissue representing the persistent portion of the median embry- 

 onic thyreoid (fig. 1069). Its base is attached ordinarily to the left side of the 



Fig. 1069. — Thyreoid Gland, -wt^th Pyramidal Lobe and Levator Muscle. 



Sterno-hyoid ligament W ^ Epiglottis 



- ^^v_->3_Body of hyoid bone 



Sterno-hyoid muscle 



Omo-hyoid 



Thyreo-hyoid 



Crico-thyreoid 



Sterno-thyreoid 



Isthmus 



Trachea 



j» ''ij^iwlp'f''— Hyo-thyreoid ligament 



Hyo-thyreoid membrane 



Levator glandulee thyreoideae 

 Thyreoid cartilage 



Pyramidal lobe of thyreoid gland 



— Left lateral lobe 



superior border of the isthmus and its apex which extends cephalically a variable 

 distance, often to the superior border of the thyreoid cartilage, is attached by a 

 fibrous cord, the thyreoid ligament. 



The pyramidal lobe is not always present. Some investigators have found it present in 

 only 40 per cent of all cases; others in as high as 90 per cent. The average is somewhere between 



Fig. 1070. — Cross-section of Neck Showing Relations of the Thyreoid Gland. 

 (After Braune, from Porier and Charpy.) 

 Sterno-hyoid 



-Sterno-thyroid 



--Platysma 



■ Sterno -mastoid 



.Lateral lobe of 

 thyreoid gland 



"V. jugularis int. 

 -A. carotis com. 



N. vagus 



A. thyreoidea sup. 



Sympathetic trunk 



A. thyreoidea inf. 

 A. vertebralis 



these extremes. It is closely adherent to the subjacent structures, usually at one side of 

 the median line, more often the left. The superficial relations of the pyramidal lobe are 

 similar to those of the isthmus. Its deep surface is in relation also with the cricoid and thyreoid 

 cartilages, the crico-thyreoid muscle arul the hyo-thyreoid ligament. 



