Visual Anatomy 視覚解剖学

口蓋扁桃（こうがいへんとう、英：palatine tonsil ）

・イラストを掲載しているサイト

【概要】

「日本人体解剖学」には以下のような解説文が見られる。

口蓋扁桃は、個人によって形状が異なり、扁桃洞から咽頭腔にのびることがあり、ときには全く平らであり、あるいはその中央が陥凹して周辺部が提状に高くなることがある。


扁桃（口腔を前部より見て）	扁桃（縦断面）	舌（模式図)	舌とその周囲

・「内側面の粘膜は深い多数の円形陥凹すなわち扁桃小窩とそれにつづく扁桃陰窩が見られる。」（日本人体解剖学）


口蓋扁桃（内側面）

■ 周囲との関係 ■

以下は「日本人体解剖学」の解説文を箇条書きにしたものになる。

・口蓋扁桃の外側面は線維膜に覆われ、口蓋咽頭筋、上咽頭収縮筋に向かう.

・咽頭壁の外側には内側翼突筋がり、その後方部はリンパ様組織で満たされ、血管・神経を含む。

　（最も扁桃に近い重要な血管は顔面動脈で、とくにそれが迂回して走る際は関係が緊密である。）


口蓋咽頭筋	咽頭後部の筋群	内側翼突筋	舌とその周辺

【脈管/神経】

　以下が口蓋扁桃に関係する脈管や神経になる。

■動脈■

・顔面動脈からの上行口蓋動脈および扁桃枝

・からの上行咽頭動脈および舌動脈の舌背枝が分布する。

　⇒ 口蓋扁桃と動脈との関係を表したイラストを掲載しているサイト

以下は「日本人体解剖学」の解説文となる。

「最も扁桃に近い重要な血管は顔面動脈で、とくにそれが迂回して走る際は関係が緊密である。上行口蓋動脈および扁桃枝（ともに顔面動脈から）は関係が最も深く、内頚動脈および内頚静脈はかなり落ち込んで、後外側方（約1㎝弱）にみられ、また外頚動脈はさらに外側方に位置する。上行咽頭動脈は、扁桃の後方に見られる。」

なお上記の動脈に加えて「Wikipedia」では「小口蓋動脈」（下降口蓋動脈の枝）の名称も見られる。

「Wikipedia」には以下のような解説文が見られる。

Blood supply is provided by tonsillar branches of five arteries: the dorsal lingual artery (of the lingual artery), ascending palatine artery (of the facial artery), tonsillar branch (of the facial artery), ascending pharyngeal artery (of the external carotid artery), and the lesser palatine artery（小口蓋動脈） (of the descending palatine artery).


顔面・外頚動脈	舌動脈舌	下降口蓋動脈

・口蓋扁桃に血液供給をしている動脈のイラストを掲載しているサイト-1

・口蓋扁桃に血液供給をしている動脈のイラストを掲載しているサイト-2

・口蓋扁桃に血液供給をしている動脈のイラストを掲載しているサイト-3

■静脈■

顔面静脈に注ぎ、また咽頭静脈叢と連絡する。


顔面静脈	咽頭静脈叢

■リンパ管■

多数みられる。各小胞周囲のリンパ叢から始まり、扁桃の外側面を過ぎ、咽頭を貫き、下顎の後下方で舌骨の大角の近くにある深頚リンパ節に入る。

■神経■

・「咽頭神経叢（舌咽神経と迷走神経の枝よりなる）からの枝が来て、小さな扁桃神経叢を形成する。」（日本人体解剖学）

「Wikipedia」には以下のような解説文が見られる。

　The palatine tonsils receive afferent nervous innervation via the tonsillar plexus, which has contributions from general somatic afferent fibers (GSA) of the maxillary division of the trigeminal nerve via the lesser palatine nerves, and general visceral afferent fibers (GVA) from the tonsillar branches of the glossopharyngeal nerve (CN IX). The glossopharyngeal nerve continues past the palatine tonsil and innervates the tongue to provide general and taste sensation. This nerve is most likely to be damaged during a tonsillectomy, which leads to reduced or lost general sensation and taste sensation to the posterior third of the tongue.

【語句】

・afferent：求心性の・tonsillar plexus：・contributions：寄与、貢献・general somatic afferent fibers：一般体性求心性繊維・maxillary vision of the trigeminal nerve：三叉神経の上顎神経・lesser palatine nerves：小口蓋神経・general visceral afferent fibers：一般内蔵求心性繊維・glossopharyngeal nerve：舌咽神経・tonsillectomy：・tonsillectomy：扁桃摘出術


咽頭神経叢

以下は「Wikipedia」の解説文となる。

Palatine tonsils, occasionally called the faucial tonsils,[2] are the tonsils on the left and right sides at the back of the throat which can often be seen as white lumps.
Tonsillitis is an inflammation of the tonsils and will often, but not necessarily, cause a sore throat and fever. In chronic cases tonsillectomy may be indicated.[3]
Functions of palatine tonsils[edit]
Local immunity[edit]
Tonsillar (relating to palatine tonsil) B cells can mature to produce all the five major Immunoglobulin (Ig, aka antibody) classes. Furthermore, when incubated in vitro with either mitogens or specific antigens, they produce specific antibodies against diphtheria toxoid, poliovirus, Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, and the lipopolysaccharide of E. coli. Most Immunoglobulin A produced by tonsillar B cells in vitro appears to be 7S monomers, although a significant proportion may be l0S dimeric IgA.
In addition to humoral immunity elicited by tonsillar and adenoidal B cells following antigenic stimulation, there is considerable T-cell response in palatine tonsils. Thus, natural infection or intranasal immunization with live, attenuated rubella virus vaccine has been reported to prime tonsillar lymphocytes much better than subcutaneous vaccination. Also, natural infection with varicella zoster virus has been found to stimulate tonsillar lymphocytes better than lymphocytes from peripheral blood.
Combined tonsillectomy and adenoidectomy had a profound detrimental effect on the local IgA response in the nasopharyngeal fluid against poliovirus. These immunological observations paralleled the increased incidence of paralytic poliomyelitis after this operation. Thus, it is obvious that the tonsils have an important role to play in the defense of the host against bacterial and viral infections, and the success of regional mucosal immunity induced by intranasal vaccines most likely depends on these immunocompetent tissues in the oropharynx and nasopharynx.
Altogether, therefore, several pieces of direct and indirect evidence indicate that the palatine tonsils are continuously engaged in local immune responses to microorganisms. If the tonsillar lymphocytes became overwhelmed with this persistent stimulation they may be unable to respond to other antigens; the immunological response, particularly in recurrent tonsillitis, may then be impaired. Once this immunological impairment occurs, the tonsil is no longer able to function adequately in local protection nor can it appropriately reinforce the secretory immune system of the upper respiratory tract.
Cytokine action[edit]
Cytokines are humoral immunomodulatory proteins or glycoproteins which control or modulate the activities of target cells, resulting in gene activation, leading to mitotic division, growth and differentiation, migration, or apoptosis. They are produced by wide range of cell types upon antigen-specific and non-antigen specific stimuli. It has been reported by many studies that the clinic outcome of many infectious, autoimmune, or malignant diseases appears to be influenced by the overall balance of production (profiles) of pro-inflammatory and anti-inflammatory cytokines. Therefore, determination of cytokine profiles in tonsil study will provide key information for further in-depth analysis of the cause and underlying mechanisms of these disorders, as well as the role and possible interactions between the T- and B-lymphocytes and other immunocompetent cells. [4]
The cytokine network represents a very sophisticated and versatile regulatory system that is essential to the immune system for overcoming the various defense strategies of microorganisms. Through several studies, the Th1 and Th2 cytokines and cytokine mRNA are both detectable in tonsillar hypertrophy (or obstructive sleep apnea, OSA) and recurrent tonsillitis groups. It showed that human palatine tonsil is an active immunological organ containing a wide range of cytokine-producing cells. Both Th1 and Th2 cells are involved in the pathophysiology of TH and RT conditions. Indeed, human tonsils persistently harbor microbial antigens even when the subject is asymptomatic of ongoing infection. It could also be an effect of ontogeny of the immune system.
Anatomy
【Blood supply and innervation】
The palatine tonsils are located in the isthmus faucium, the anterior being the palatoglossal arch, and the posterior being the palatopharyngeal arch. Collectively they are referred to as the fauces. Between these arches is the tonsillar bed, within which lie the palatine tonsils and the nervous and arterial structures that supply them.
　The palatine tonsils receive afferent nervous innervation via the tonsillar plexus, which has contributions from general somatic afferent fibers (GSA) of the maxillary division of the trigeminal nerve via the lesser palatine nerves, and general visceral afferent fibers (GVA) from the tonsillar branches of the glossopharyngeal nerve (CN IX). The glossopharyngeal nerve continues past the palatine tonsil and innervates the tongue to provide general and taste sensation. This nerve is most likely to be damaged during a tonsillectomy, which leads to reduced or lost general sensation and taste sensation to the posterior third of the tongue.
　Blood supply is provided by tonsillar branches of five arteries: the dorsal lingual artery (of the lingual artery), ascending palatine artery (of the facial artery), tonsillar branch (of the facial artery), ascending pharyngeal artery (of the external carotid artery), and the lesser palatine artery (of the descending palatine artery).

　The tonsils venous drainage is by the peritonsillar plexus, which drain into the lingual and pharyngeal veins, which in turn drain into the internal jugular vein.
The palatine tonsil is one of the mucosa-associated lymphoid tissues (MALT), located at the entrance to the upper respiratory and gastrointestinal tracts to protect the body from the entry of exogenous material through mucosal sites. In consequence it is a site of, and potential focus for, infections, and is one of the chief immunocompetent tissues in the oropharynx. It forms part of the Waldeyer's ring, which comprises the nasopharyngeal tonsil or adenoid (NT), the paired tubal tonsils (TT), the paired palatine tonsils (PT) and the lingual tonsil (LT). From the pharyngeal side, they are covered with a stratified squamous epithelium, whereas a fibrous capsule links them to the wall of the pharynx. Through the capsule pass trabecules that contain small blood vessels, nerves and lymphatic vessels. These trabecules divide the tonsil into lobules.
In children, the tonsils are common sites of infections that may give rise to acute or chronic tonsillitis. However, it is still an open question whether tonsillar hypertrophy is also caused by a persistent infection. Tonsillectomy is one of the most common major operations performed on children. The indications for the operation have been complicated by the controversy over the benefits of removing a chronically infected tissue and the possible harm caused by eliminating an important immune inductive tissue.
The information that is necessary to make a rational decision to resolve this controversy can be obtained by understanding the immunological potential of the normal palatine tonsils and comparing these functions with the changes that occur in the chronically diseased counterparts.
Tonsillar crypts
Main article: tonsillar crypts

Low-power microscope magnification of a cross-section through one of the tonsillar crypts (running diagonally) as it opens onto the surface of the throat (at the top). Stratified epithelium (e) covers the throat's surface and continues as a lining of the crypt. Beneath the surface are numerous nodules (f) of lymphoid tissue. Many lymph cells (dark-colored region) pass from the nodules toward the surface and will eventually mix with the saliva as salivary corpuscles (s).
Palatine tonsils consist of approximately 15 crypts, which result in a large internal surface. The tonsils contain four lymphoid compartments that influence immune functions, namely the reticular crypt epithelium, the extrafollicular area, the mantle zones of lymphoid follicles, and the follicular germinal centers. In human palatine tonsils, the very first part exposed to the outside environment is tonsillar epithelium.