254 ANATOMY IN A NUTSHELL. 



A< tii in. - Contracts the superior opening of the larynx. 



Nerve Supply. — Recurrent laryngeal nerve. 



Nerve Supply. — The Crico-thyroid muscles and mucous membrane of the 

 larynx receive the superior laryngeal nerves, all the remaining muscles receive 

 the inferior <>r recurrent laryngeal nerves. The Arytenoideus receives both 

 superior and inferior laryngeal nerves. 



1 ;;.oi in Supply. The laryngeal branches from the superior thyroid and 

 inferior thyroid arteries pass to the larynx. The veins, which accompany the 

 superior laryngeal artery, join the superior thyroid vein which empties into the 

 internal jugular vein. The veins which accompany the inferior laryngeal 

 artery join the interior thyroid vein which empties into the innominate vein. 

 The lymphatics pass into the deep cervical nodes. 



Trachea. (Plate CXX.) 



The word trachea comes from a Greek word which means rough. It is also 

 called the wind pipe and is the air passage of the body beginning at the larynx 

 and ending in the bronchial tubes. It is composed of sixteen to twenty car- 

 tilages or osseous rings. The first ring is called the cricoid cartilage, and the 

 last one is called the pessulus. This last one is situated at the forking of the 

 trachea into the right and left bronchial tubes. The trachea is a musculo- 

 membranous tube and it communicates with the mouth and nose through the 

 larynx, and with the lungs through the bronchial tubes. All vertebrates, which 

 breathe air with lungs, have a trachea which is subject to very little variation 

 in character. The human trachea is about four and one-half inches long, ex- 

 tending from the sixth cervical vertebra to the fourth dorsal vertebra where it 

 branches into the two bronchi. The oesophagus is between the trachea and the 

 spinal column. The average diameter of the trachea is about four-fifths of an 

 inch in the cadaver. The antero-posterior diameter is somewhat less. Dur- 

 ing life these dimensions are smaller. The rings of the trachea are incomplete 

 behind where they join the (esophagus. 



Blood Supply. —Inferior thyroid arteries. The veins terminate in the 

 thyroid venous plexus. 



Nerve Supply.— Pneumogastric and sympathetic. 



The right bronchus is about an inch in length and in direction is more hor- 

 izontal in its passage to the rool of the lung than the left bronchus. It is wider 

 than lie Nft and divi les into three branches to the lung. The left bronchus 

 is nearly tun inches in length and is smaller, longer, and more oblique than the 

 righl one. It enters the root of the lung opposite the sixth dorsal vertebra, 

 which is alioiii an inch lower than the point whe'e the right bronchus enters 

 i In lung. It divides into two branches. It has above it the arch of the aorta. 

 behind it the (esophagus, thoracic duct, and the descending aorta. The left 

 pulmonary artery is a1 first above, then in front of the left bronchus. 



LESSON LXX. 



Lungs. (Plates CXXI-CXXII-CXXIII.) 

 Tin word Lung comes from the Latin pulmones, from which comes pul- 



