Illustrated Encyclopedia of Human Anatomic Variation: Opus IV: Organ Systems: Endocrine System

Thyroid Gland

Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD
Peer Review Status: Internally Peer Reviewed

Most of the variations in the thyroid gland are due to a partial persistence of the median or thyroglossal duct. The most obvious example of this persistence is the lobus pyramidalis. In one study, it was found in 104 of 153 cases (nearly 68%) while in another study it was found in only 24 of 60 cases (40%). It is usually attached to the isthmus on the left side of the median plane, but it may join either of the lateral lobes. It is usually connected above the hyoid bone. Of the 104 specimens in which the pyramidal process was found to be present, 55 were glandular up to the hyoid bone; in 12 the process was connected to the hyoid by fibrous tissue, and in two, by muscle.

Accessory thyroid tissue above the gland proper is dervived from the thyroglossal tract. Accessory nodules of thyroid tissue may be found at the embryologic origin of the thyroid gland, at the foramen caecum, on the lingual duct and thyroglossal tract within the tongue; these are the so-called Glandulae Accessoriae Linguales. Accessory glandulae have been found in the suprahyoid, praehyoidea and intrahyoidea regioins of the duct. Various nodules are also found in the praethyroid area of the duct, these are named Glandula Accessoria Praethyroidea. Finally, some glands have a lobus pyramidalis projecting from the thyroid gland proper, and is the terminal portion of the thyroglossal tract. The first authenticated case of lingual thyroid was reported by Bernays in 1888. Montgomery reported 144 authenticated cases of lingual thyroid and two cases in the body of the tongue.

The muscular fasciculi, which are occasionally found to descend from the hyoid bone to the thyroid gland or its pyramidal process, are known as the levator glandulae thyroidea. The fibers are most frequently derived from the thyrohyoid muscle, but occasionally they are independent. In one case, there were two pyramidal processes; in another, a single process divided into an inverted Y, with the two processes joining each lateral lobe.

Accessory thyroids may be formed by transverse division of the pyramidal process into several separate masses; more rarely they are associated with the lateral lobes.

Small glandular masses that resemble the thyroid in structure are frequently found in front or above the hyoid bone, and are derived from the upper part of the thyroglossal duct. The isthmus of the gland may be joined to the hyoid bone above the organ by a fibrous cord, a remnant of the embryologic thyroglossal duct.

Thyroid tissue may also be found in the thorax in association with the aortic arch, and in the tongue around the foramen cecum three cases (3/800,000) of thyroid disease, and in the pharynx. Ovarian tumors of thyroid tissue have been reported.

As a rule, the two lateral lobes are almost equally well-developed, but occasionally they are very unequal in size, and in rare cases one lobe may be absent. The isthmus varies greatly in size and is frequently absent.

The thyoid gland may be absent.

The presence of thyroid tissue within the tracheal lumen is an unusual cause of upper respiratory obstruction. It may be life threatening. Thyroid tissue in this location may be true ectopic thyroid tissue or may be caused by invastion of the trachea by a malignant process (Donegan and Wood). True ectopic thyroid tissue in the trachea is a rare, but well described abnormality, accounting for 6 to 7% of all primary endotracheal tumors. The first case of intratracheal goiter was described by Ziemssen in 1875. Many cases have been reported since this time, in regions where goiters are endemic, which may account for the high number of cases reported in European literature. According to Donegan and Wood, Falk, in 1936, performed 21 autopsies on new born infants and in two cases found thyroid tissue extending into the trachea through the cricotracheal ligament.

In an article on the history of the thyroid gland, by Noehren and Noehren, the earliest treatment for goiter may be traced to China as far back as 1600 B.C. The Chinese used burnt sponges and seaweed to cure goiter; this being the first empirical use of iodine-containing substances. The first authenticated reference of their use in China can be found in the Pen Tsao written by Li His Chin in 1596 A.D. It is interesting that Chilean use of seaweed for goiter occurred independently of eastern civilization. The inhabitants of South America chewed the stems of seaweed, named Palo-coto (defined as "goiter-stick") to reduce iodine deficiency.

Julius Cassenius (1600) of Padua, was the first person to describe the thyroid as a single gland. In his "First Dissection of a Man" there is a drawing in which the gland appears as a single body lying across the top of the trachea and this is called the "Corpus Glandulosum ad Laryngeurn ipsum situm" . He was unable to find any duct from this gland and concluded that none existed. This led Cassenius to believe that the thyroid had an esthetic significance by filling out the sides of the neck. Thus he wrote: "And though it is only becoming that the soul, which is the noblest part of man, should have a splendid dwelling place, kind nature has especially beautified the gentle female with many sorts of ornaments, and not the least among them is this one, that the empty spaces which exist around the larynx, being filled up, they show to our eyes, to the great joy of our sight, a regular and roundish neck."

The idea of the goiter being beautiful continued, thus Sir Frednich Leighton, famous painter of the Pre-Raphaelite School, shows one of his masterpieces "Lucia" a woman with a marked diffuse goiter. In the Austrian Tyrol, too, a goiter was considered a thing of beauty and therefore, according to one surgeon, a goiter operation was seldom performed. Professor Rose, a biochemist who taught at the University of Illinois, Champaign-Urbana, in the 1950's, had been a graduate student in Switzerland, and reported that the young women in that country who were without goiters believed themselves unattractive but they were able to purchase undergarments to give their neck the appearance of a "beautiful," rounded goitrous neck.

According to Skolnik, et al. lingual thyroid may represent the only functioning thyroid tissue in the body in 70 to 80% of cases studied.

Thyroid Gland Variations

Thyroid Glands Without an Isthmus

Thyroid Glands Without an Isthmus

Accessory Thyroid Glands in Neck and Chest

Accessory Thyroid Gland

Accessory Thyroid Gland

Accessory Thyroid Bodies

Intratracheal Thyroid

Pyramidal lobe of Thyroid

Development of the Thyroid Gland

References

D'Ajutolo, G. (1889) Delle strume tiroidee accessorie ed in particolare di una mediastinica e di due cervicali nello stesso individuo. Mem. R. Accad. Sci. Istituto di Bologna S.4, 10:773-782.

Austoni, A. (1910) Sui tumori linguali di natura tireoidea. Clinica Chirurgica 18:1618-1646.

Bailey, H. (1924-25) Thyroglossal cysts and fistulae. Brit. J. Surg. 12:579-589.

Baker, A.E. (1896) Sequel of a case of cystic accessory thyroid body in which four operations for recurrence were performed in the course of six years. Trans. Path. Soc. Lond. 47:225-227.

Batson, O.V. (1946) The adult thyroglossal duct. Anat. Rec. 94:447-450.

Beach, F. (1876) Trachea, showing absence of thyroid gland, and fatty tumors, from a case of sporadic cretinism. Trans. Pathol. Soc. London 27:316-321.

Beck, J.S. (1960) Ectopic thyroid tissue in the mucosa of the trachea. The J. of Laryngol. and Otology 74:420-422.

Benjamins, C. E. (1899) Een struma op den wortel van de tong. Nederlandsch Tijdschrift voor Geneeskunde 2:194-211.

Bergman, Ronald A. (1953) Personal communication.

Bernays, A.C. (1888) The origin of the foramen caecum linguae, as shown by an operation on a rare tumor of the root of the tongue. St. Louis Med. & Surg. Journal 55:201-205.

Bill, A.H. (1956) Cysts and sinuses of the neck of thyroglossal and brachial origin. Surg. Clin. N. America 36:1599-1611.

Bishop, F.J. (1934) Lingual thyroid. Ann. Otol. Rhin. & Laryng. 43:294-298.

Bisi, H. (1930) Bocio aberrante de la base de la lengua. Asociaci6n Medica Argentina, Revista de especialidades; Craonica de sesiones. Sociedad de Oto-Rino-Laryngologia. 5:321-345.

Bloch, A et -. Lemoine. (1928) Tumeur de la base de [a langue. Annales des Maladies de I'Oreille, du Larynx, du nez et du pharynx. Société de Laryngologie des Hopitaux de Paris 47:311.

Bone, R.C., Biller, H.F. and T.M. Irwin. (1972) Intralaryngotracheal thyroid. Ann. of Otology, Rhinology and Laryngology 81:424-428.

Brown, J.M. (1935) Branchial and thyroglossal duct cysts and fistulas. Ann. Otol. Rhin. Laryng. 44:644-652.

Buckman, L.T. (1936) Lingual thyroid. The Laryngoscope. 46:765-784.

Butlin, -. (1890) Tumeurs glandulaires de la racine de la langue. La Sémaine Méd. 10:87.

Cassenius, J. (1600) De Vocis Auditusque Organis Historia Anatomica, Fen-ania.

Cooper, T.V. (1950) A case of aberrant thyroid tissue in the trachea. J. Clin. Pathol. 3:48-50.

Crispell, K.R. and W. Parson. (1950) Lingual thyroid. South. Med. J. 43:945-946.

Culing, T.B. (1850) Two cases of absence of the thyroid body, and symmetrical swellings of fat tissue at the sides of the neck, connected with defective cerebral development. Medico-Chirurg. Trans. 33:303-306.

Dalgaard, J.B. and P. Wetteland. (1956) Lateral cervical thyroid metastases. A follow-up study of 39 cases (Aberrant thyroid tissue I). Acta Chir. Scand. 111:431-443.

Dalgaard, J.B. and P. Wetteland. (1956) Thyroglossal anomalies. A follow-up of 58 cases (Aberrant thyroid tissue II). Acta Chir. Scand. 111:444-455.

Dimson, S.B. (1956) Juvenile myxedema due to removal of ectopic thyroid. Proc. Roy. Soc. Med. 49:941.

Donegan, J.O. and M.D.Wood. (1985) Intratracheal thyroid - Familial occurrence. The Laryngoscope 95:6-9.

Donagan, J.O. and M.D. Wood. (1985) Intratracheal thyroid--Familial occurrence. laryngoscope 95(2):66-8.

Dowling, E.A., Johnson, I.M., Collier, F.C.D. Collier and R.A. Dillard (1962) Intratracheal Goiter: A cifflico - pathologic review. Ann. Surgery 156:258-267.

Edmunds, W. (1896) Cystic accessory thyroid body. Trans. Path. Soc. London. 47:223-224.

Else, J.E. (1930) Anatomical variations in the thyroid as a cause of recurrent goiter. Am. J. Surg. 8:92-96.

Falk, P. (1936) Ueber ortsfremde gutartige gewebsbildungen. Thymus -undthyroidea gewebe. Arch. f. Ohren-, Nasen- und KehIkopfheilkunde, Berlin 141:118-132.

Fish, J. and R.M. Moore. (1963) Ectopic thyroid tissue and ectopic thyroid carcinoma. Review of the literature and report of a case. Ann. Surgery 157:212-222.

Gnieve, J. (1958) A subhyoid median ectopic thyroid. Arch. Dis. Childhood 34:18-19.

Goetsch, E. (1948) Lingual goiter: Report of three cases. Ann. Surg. 127:291-316.

Gow, W.J. (1884) Total absence of the left lobe of the thyroid body. J. Anat. Physiol. 18:118.

Grace, R.V. and C. Weeks. (1932) Lingual thyroid. Ann. Surg. 96:973-978.

Gruber, W. (1868) über das Zungenbein-Schildknorpel-Hilfsband (Ligamentum hypothyreoideum accessorium) Arch. Anat. Physiol. Wissen Med. 1868:633-634.

Gruber, W. (1876) über die Glandula thyreoidea ohne Isthmus beim Menschen. Arch. Anat. Physiol. Wissenschaftliche Med. 1876:208-220.

Gruber, W. (1876) über die Glandula thyreoidea accessoria. Arch. Pathol. Anat. Physiol. Klin. Med. 66:447-454.

Gruber, W. (1876) Eine Glandula thyreoides bipartita bei Anwesenheit eines rudimentären Isthmus. Arch. Pathol. Anat. Physiol. Klin. Med. 66:454-455.

Haddad, A., Frenkiel, S., Costom, B., Shapirs, R. and T. Tewfik. (1986) Management of the undescended thyroid. The Journal of Otolaryngology (Le Journal d'Oto-Rhino-Laryngologie) 15(6):373-376.

Haffly, G.N. (1976) The spectacular lingual thyroid and midline anterior cervical ectopic thyroid. Trans. Pac. Coast Oto. Ophthalmol. Soc. 57:137-143.

Hammar, J.A. (1901) Notiz Uber die Entwickelung der Zunge und der Mundspeceicheldrüsen beim Menschen. Anat. Ariz. 19:570-575.

Hartley, J.M.J. (1922) Some errors in the development of the thyroid gland. Surg., Gynecol. Obstet. 35:543-552.

Haynes, I.S. (1912) Sublingual thyroid. Ann. Surgery 56:465-466.

Hickman, W. (1869) Congenital tumor of the base of the tongue passing down the epiglottis on the larynx and causing deart by suffocation sixteen hours after death (sic, birth). Trans. Pathological Soc. London 20:100-163.

Hilless, A.D. and J.E. Black. (1976) Lingual ectopia of the thyroid gland and autotransplantation. Br. J. Surg. 63:924-926.

Hubert, L. (1947) Thyroglossal cysts and sinuses: Analysis of forty-three cases. Arch. Otolaryng. 45:105-111.

Hung, W., Judson, G.R., Sabatini, D. and T. Winship. (1966) Lingual and sublingual thyroid glands in euthyroid children. Pediatrics 38(4):647-651.

Jacques, -. (1905) Deux cas d'ectopie thyroidienne. Soc. Biol. Comptes Rendus Hebdomadaires des Séances et Mémoires. 59:714-715.

Jain, S.N. (1969) Lingual thyroid. Internat. Surgery 52(l):320-325.

Jones, P. (1961) Autotransplantation in lingual ectopia of the thyroid gland. Arch. Disease in Childhood 36:164-170.

Jones, T. (1935) Lingual thyreoid gland in a cretin of 78 years. Anat. Rec. 63:315-316.

Jurasz, A. (1877) Eine seltene Anomalie des Schildknorpels und dessen Verbindung mit dem Zungenbeine. Arch. Anat. Physiol. Wissen. Med. 1877:399-400.

Kadyi, H. (1879) über accessorische Schilddrüsenlappchen in der Zungenbeingegend (Glandula praehyoides et suprahyoides). Arch. Anat. Physiol. Wissen. Med. 1879:312-320.

Kamat, M.R., Kulkarm, J.N., Desai, P.B. and D.J. Jussawalla. (1979) Lingual thyrold:a review of 12 cases. Br. J. Surg. 66:537-539.

Kanthack, A.A. (1891) The thyreo-glossal duct. J. Anat. Physiol. 25:155-165.

Kaplan, M., Kauli, R., Lubin,E., Grunebaum, M. and Z. Laron. (1978) Ectopic thyroid gland. The Journal of Pediatrics 92(2):205-209.

Katz, A.D. and W.J. Zager. (1971) The lingual thyroid: Its diagnosis and treatment. Arch. Surg. 102:582-585.

King, W.L.M. and J. deJ. Pembertin. (1942) So-called lateral aberrant thyroid tumors. Surg. Gynecol. Obstet. 74:991-1001.

Kingsbury, B.F. (1935) On the fate of the ultimobranchial body within the human thyroid gland. Anat. Rec. 61:155-173.

Kingsbury, B.F. (1939) The question of a lateral thyroid in mammals with special reference to man. Am. J. Anat. 65:333-358.

Krafka, Jr., J. (1937) Intratracheal thyroid occurring in a seven month human fetus. Ann. Surg. 106:457-459.

Lahey, F.H. and N.W. Swinton. (1934) Intrathoracic goiter. Surg. Gynecol. Obstet. 59:627-637.

von Lanz, T. und W. Wachsmuth (1955) Praktische Anatomie, Firstbook, 2nd part, Hals., Springer Verlag, Berlin, Göttingen, Heidelberg.

Larochelle, D., Arcand, P., Belzile, M. and N.B. Gagnon. (1979) Ectopic thyroid tissue - a review of the literature. The Journal of Otolaryngology (Le Journal d'Oto-Rhino-Laryngologie) 8(l):523-530.

Lemmon, W.T. and G.W. Paschal, Jr. (1941) Lingual thyroid. Am. J. Surg. 52:82-85.

Lewis, M.I. and W.M. Holleran (1968) Ectopic thyroid gland in children. Am. J. Surgery 115:686- 690.

Madelung, -. (1879) Anatomisches und Chirurgisches über die Glandula thyreoidea accessoria. Von Langenbeck's Arch. Klin. Chir. 24:71-107.

Marshall, C.F. (1892) Thyro-glossal duct or canal of His. J. Anat. Physiol. 26:94-99.

Marshall, C.F. (1895) Variations in the form of the thyroid gland in man. J. Anat. Physiol. 29:234-239.

Marshall, S.F. and W.F. Becker. (1949) Thyroglossal cysts and sinuses. Ann. Surg. 129-642-651.

Mayo, C.M. (1911) Lingual, sublingual and other forms of aberrant thyroids. JAMA 57:784-786.

Montgomery, M.L. (1935) Lingual thyroid. Trans. Ameri. Assoc. for the Study of Goiter, page 135.

Montgomery, M.L. (1935) Lingual thyroid: A comprehensive review. Western J. Surgery 43:661-XXX.

Montgomery, M.L. (1936) Lingual thyroid: A comprehensive review. Western J. Surgery 44:54, 122, 189, 237, 303, 373, and 442.

Moseley, J.M. (1968) The ultimobranchial origin of calcitonen. The Lancet, London 1: 108-110.

Moses, D.C., Thompson, N.W., Nishiyama, R.H. and J.C. Sisson.(1976) Ectopic thyroid tissue in the neck: Benign or malignant? Cancer 38:361-365.

Myers, E.N. and I.P. Pantangco, Jr. (1975) Intratracheal thyroid. Laryngoscope 85:1833-1840.

Ngo, H-H., Frenkiel, S. and R. Satin. (1988) Thyroglossal duct cyst presenting as an anterior tongue fistula. The Journal of Otolaryngology (Le Journal d'Oto-Rhino-Laryngoloie) 17(5):227-228.

Noehren, A.H. and W.A. Noehren. (1936) The history of the thyroid gland. Western Journal of Surgery obstetrics and gynecology. 44(l):488-500.

Noritomi, S., Nakashima, Y., Oshibuchi, H., Furukawa, M., Kondo, N., Sugihara, Y., Koga, T. and T. Tsunoda. (1970) A case of subhyold median ectopic thyroid associated with lingual thyroid. Acta Medica Nagasakiensia 14~3-4):98-104.

Noyek, A.M. and J. Friedberg. (1981) Thyroglossal duct and ectopic thyroid disorders. Otolaryngologic Clinics of North America 14(l):187-201.

Odell, W.D., Stephenson, J.K. and R.H. Williams. (1959) Treatment of a lingual goiter with tniodothyronine. Journal of Clinical Endocrinology and Metabolism 19(3):363-368.

Ogle, C. (1896) Accessory thyroid body. Trans. Path. Soc. Lond. 47:224.

Orti, E., Castells, S., Quazi, Q.H. and S. Inamdar. (1971) Familial thyroid disease: lingual thyroid in two siblings and hypoplasia of a thyroid lobe in a third. Journal of Pediatrics 78:466-468.

Paltauf, R. (1892) Zur Kenntniss der Schilddrüsentumoren im Innern des Kelkopfs und der Luftröhre. Ziegler's Beiträge z. patholoischen Anatomie u. z. allgerneinen Pathologie 11:71-89.

Pemberton, J. deJ. and L.K. Stalker. (1940) Cysts, sinuses and fistuale of the thyroglassal duct. Results in two hundred and ninety-three surgical cases. Ann. Surg. 111:950-957.

Podar, G.G. and P.B. Desai. (1971) Carcinoma of the lingual thyroid. Laryngoscope 81:427-429.

Pool, E.H. and H.C. Falk. (1916) Concerning the surgical anatomy of the thyroid, with special reference to the parathyroid glands. Ann. Surg. 63:71-77.

Pôrto, G. (1960) Esophageal nodule of thyroid tissue. The Laryngoscope 70:1336-1338.

Quigley, W.F., Williams, L.F. and C.W. Hughes. (1962) Surgical management of subhyoid median ectopic thyroid. Annals of Surgery 155:305-308

Randolph, J., Grunt, J.A. and G.F. Vawter. (1963) The medical and surgical aspects of intratracheal goiter. The New England Journal of Medicine 268:457-461.

Ray, B.S. (1938) Lingual thyroid. Arch. Surg. 37:316-326.

Richardson, J.R. and M. Lineback. (1952) Radioactive iodine in the diagnosis and treatment of lingual thyroid adenoma. The Laryngoscope 62:934-943.

Roeder, C.A. (1932) Operations on the superior pole of the thyroid. Arch. Surg. 24:426-429.

Roman, R.M. (1985) The physiology of the thyroid gland. Ear, Nose and Throat Journal 64(7):334-350.

Rosen, I.B. and P.G. Walfish. (1967) The subhyold ectopic median thyroid. Canadian. Med. Assn. J. (Le Journal de I'Association Medicale Canadienne) 96:544-549.

Rosendale, R.S. (1936) Intralingual thyroid: Discussion with report of a large struma presenting in the anterior part of the tongue. Ann. Otol., Rhin., & Larygol. 45:1009-1018.

Sauk, J.J. (1970) Ectopic lingual thyroid. J. Pathology 102:239-243.

Seelye, W.K. (1916) Thyreoglossal tumor (aberrant thyroid). Northwest Med. 15:334.

Seldowitsch, J. (1897) Ein Fall von Struma accessoria baseos linguae: Entstehung emes myxodems rach entfernung derselben. Centralbl. f. Chir. 24:499-500.

Sharer, R.F. (1936) Substernal thyroid. Am. J. Surg. 32:56-62, 99, 107.

Skolnik, E.M., Newell, R., Rosenthal, I.M. and R.S. Webb. (1963) Autotransplantation in lingual ectopia of thyroid gland. Arch. Otolaryngol. 78:187-191.

Skolnik, E.M., Yee, K.F. and T.A. Golden. (1975) Transposition of the lingual thyroid. Laryngoscope 85(11):785-791.

Smith, C. (1939) Lingual thyroid. Archives of Otolaryngology 29:78-81.

Spencer, W.G. (1914) The thyroglossal tract. Lancet 1:522-524.

Springer, K.C. (1955) Lingual thyroid: 2 cases in siblings diagnosed and treated with radioactive iodine. A.M.A. Archives of Otolaryngology 61:386-393.

Stokke, D.B. and P. Andresen. (1970) Familial occurrence of "cryptothyoidism" with functioning ectopic thyroid tissue in solitary subhyoid localization. Danish Medical Bulletin 17(6):189-192.

Strickland, A.L., Macfie, J.A. and J.J. Van Wyk. (1969) Ectopic thyroid glands simulating thyreoglossal duct cysts. Journal of the American Medical Association (JAMA) 208:307-310.

Swan, H., Jenkins, D. and C. MacGregor. (1958) Autotransplantation of the lingual thyroid. A.M.A. Arch. Surg. 76:458-464.

Swan, H., Jenkins, D and J. Schemmel. (1967) Thyroid autograft.: A 12-year follow-up. Arch. Surg. 94:817-820.

Sweet, R.H. (1949) Intrathroacic goiter located in the posterior mediastinum. Surg., Gynecol. Obstet. 89:57-66.

Sweet, R.M. (1979) Lingual thyroid. Ear, Nose & Throat 58(12):515-519.

Trayna, J. (1967) Lingual thyroid. N.Y. State Journal of Medicine 67(Il):2980-2982.

Ulrich, H.F. (1932) Lingual tyroid. Ann. Surg. 95:503-507.

Waggoner, L.G. (1959) Intratracheal thyroid. Ann. Otol., Rhino & Lmyngol. 67:61-71.

Wapshaw, H. (1942-43) Lingual thyroid. Brit. J. Surg. 30:160-165.

Ward, G.E., Cantrell, J.R. and W.B. Allan. (1954) The surgical treatment of lingual thyroid. Ann. Surg. 139:536-546.

Warren, S. and J.D. Feldman. (1949) The nature of lateral "aberrant" thyroid tumors. Surg., Gynecol. Obstet. 88:31-44.

Wegelin, C. (1939) Zur Entstehung des intralaryngotrachealen Kropfes. Schweizerische Medizinische Wochenschrift (Journal Suisse de Medecine) 69:592-593.

Welder, D.J. and W. Parker. (1977) Lingual thyroid: review, case reports, and therapeutic guidelines. Ann. Otol., Rhino. & Laryngol. 86:841-848.

Wertz, M.L. (1974) Management of undescended lingual and subhyold thyroid glands. Laryngoscope 84(4):507-520.

Wolf, R. (1889) Fall von accessorischer Schildrüse in der Zunge. Dtsch. Med. Wochenschr. 15:638.

Section Top | Title Page

URL: http://www.anatomyatlases.org/