70 PRACTICAL ANATOMY. 



1. Locate tlie thyroid gland. 



It is in the third layer of deep cervical fascia. It embraces the cricoid car- 

 tilage of the larynx and the upper part of the trachea. 



2. From illicit source docs the tJiyroid gland receive its blood / 



From the superior thyroid artery, a branch of the external carotid, and from 

 the inferior thyroid, a branch of the thyroid axis of the subclavian artery. 



3. Does anastomosis occur between tlie right and left thvroid arteries / 

 Yes ; this occurs, but very scantily, in the isthmus. 



4. Does the thyroid ever receive blood from any other source / 



Yes ; it may receive an artery either from the arch of the aorta or from the 

 innominate artery, called the thyroidea ima. 



5. From what source does the thyroid gland derive its nerve-stepply ? 

 From the middle cervical ganglion of the sympathetic. 



6. By ivhat structures is the thyroid gland covered ? 



By the skin, superficial fascia, first and second layers of deep fascia, the latter 

 containing the depressor muscles of the hyoid bone. 



7. Give contents of the carotid sheath and locate the same. 



It contains the common carotid artery, the pneumogastric or vagus nerve, and 

 the internal jugular vein. On the sheath lies the ansa-hypoglossal loop, from 

 which the depressor muscles of the hyoid bone are innervated. The sheath is 

 in the third layer of deep cervical fascia, and crossed near its middle third by the 

 omo-hyoid muscle. 



8. Explain the common carotid artery. 



It lies to the inner side of the sheath, very near the larynx and trachea. To 

 its outer side is the internal jugular vein. It is crossed by the ansa-hypoglossal 

 loop and omo-hyoid muscle. On the right side it begins at the bifurcation of the 

 innominate artery, behind the sterno-clavicular joint ; on the left side it begins 

 at the arch of the aorta. The common carotid arteries end near the hyoid bone 

 by dividing into the external and internal carotids, having given off no branches 

 in their course. 



9. Describe the internal carotid artery. 



It begins at the bifurcation of the common carotid, and has four stages : 



(1) The cervical stage to the base of the skull, where it enters the temporal bone ; 



(2) the petrosal stage, where it passes through the carotid canal in the petrosal 

 part of the temporal bone ; (3) the cavernous stage, where it lies in the caver- 

 nous sinus of the dura mater, by the side of the body of the sphenoid bone ; 

 (4) the cerebral stage, where it comes through the dura mater to give off its 

 terminal branches to the brain. 



10. Name the branches given off from tJie intracranial portion of tJie internal 

 carotid. 



(i) It contributes the anterior cerebral, the middle cerebral, and the posterior 

 communicating to the circle of Willis. (2) It gives off the ophthalmic artery 

 for the supply of the orbit and its contents, the ethmoidal cells and the inner and 

 outer nose in part. (3) It gives off the anterior meningeal arteries to the dura 

 of the anterior fossa of the base of the skull. (4) It supplies the Gasserian 

 ganglion. 



1 1. \Vliat brandies are given off from the petrosal stage ? 



(i) The Vidian, which is said to anastomose with the Vidian branch of the 

 internal maxillary. (2) The tympanic, which goes to the middle ear and anas- 

 tomoses with the tympanic branches of the internal maxillary and stylo-mastoid 

 arteries. 



12. Name all the structures between the sh'/i and the internal carotid one-half 

 of an incJi below flic base of tlie skull. 



(i) The parotid gland ; (2) posterior belly of the digastric muscle ; (3) stylo- 



