Page 19 - Science Focus (issue20)

A New Body Part to Keep One SALIVATING

令人「垂涎」的新發現

Anatomy is one of the oldest fields in biology. Ever urethra, named the Skene’s gland, which is the female 現的新唾腺位於頭部中央，靠近鼻子的位置​
since ancient Egypt, people have been dissecting the version of the prostate and can also develop cancer. [1,​2]。
human body to understand how it works. Along the Therefore, the scientists could obtain such a scan for
millennia, the understanding of our own bodies has their investigation. 雖然聽起來似乎不太可能，這對新
gone from the primitive sketches by ancient Egyptians By now, you are probably wondering why people 結構是在前列腺癌掃描中被發現的。
and Greeks, to the detailed drawings by Leonardo could miss a 4-cm tissue right in the middle of the 為了篩查前列腺癌患者的癌細胞擴散，
da Vinci, and to the famous reference book Gray’s head despite millennia of dissection. While the gland 這組荷蘭醫生為病人進行了從大腿到
Anatomy. However, in the past two centuries, nothing is impossible to miss if exposed, it is not very accessible. 顱 骨 的 PSMA 正 電子電 腦 斷 層 掃 描
much has changed in the field of anatomy. Just when Endoscopy is needed to reach that deep into the head. （PSMA​PET/CT​scan）[2]。PSMA 是 前
everyone, including medical professionals, is convinced Also, the gland does not show up in MRI or CT scan, but 列腺特異性膜抗原（prostate-specific​
that we have fully mapped out all the body structures, only PET scan [2].
a team of Dutch scientists discovered a new pair of The discovery of the new pair of salivary glands membrane​antigen），一 種 存 在 於
salivary glands. does not just change the textbook description of 幾乎所有前列腺癌細胞表面的蛋白質​
Salivary glands, as the name implies, secrete saliva, the glands, but may also change the way doctors [3]。在掃描過程中，醫生會使用放射性
which contains enzymes to break down starch and treat head and neck cancer. The salivary glands are 染料標記 PSMA 以檢測癌細胞，但令他
acts as a lubricant to help us swallow food. Before this important for swallowing and speaking, so doctors 們感到困惑的是染料亦使頭部中央的
groundbreaking discovery, it was known that humans always try to avoid damaging them in radiotherapy. 結構在掃描中亮起來​[1]。
have three pairs of major salivary glands, one in However, many head and neck cancer patients still 儘管醫生們最初相信這只是一
front of the ears (parotid glands), one under the jaw experience mouth dryness after the treatment. The 種誤差，但還是決定對其進行研究。
(submandibular glands), and one under the tongue new pair of salivary glands that used to be unnoticed
(sublingual glands); and around 1000 minor glands in and possibly damaged in radiotherapy might explain 通過閱讀一些較詳細的解剖學參考
the head and neck region. This new pair of salivary the phenomenon. In a cohort of over 700 patients, 書，他們發現顯示異常信號的區域的
glands are located right in the middle of the head, the doctors discovered a correlation between the 確由唾腺組織組成，但在文獻中從未被
near the nose [1, 2]. dose applied to the newly discovered glands and the 如此標記​[2]。他們還查看了其他前列腺
As unlikely as it sounds, the discovery of these complaint of dry feeling in the mouth, suggesting the 癌患者的掃描結果，令他們驚訝的是，其餘 100
new structures in the head began with some prostate new pair of salivary glands are still functional [1]. From 張掃描結果都顯示出一個靠近鼻子的區域有相同的信號，其平均
cancer scans. To screen for metastasis in prostate now on, doctors may try to avoid those salivary glands 長度為四厘米 [1]。
cancer patients, the Dutch doctors performed a PSMA in radiotherapy. 更有趣的是，從一個女性患者的掃描結果中，科學家們證實相同的結構
PET/CT scan from the upper leg to the skull [2]. PSMA While the discovery may not change the way most
stands for prostate-specific membrane antigen, a people live, there is a takeaway message for everyone 也出現在女性身體內​[2]。儘管女性沒有前列腺，但在尿道附近有一個名為斯
protein presents on the surface of almost all prostate – keep an open mind when you encounter something 基恩氏腺（Skene’s​gland）的小組織，它是雌性版本的前列腺，而那裡也可以
cancer cells [3]. A radioactive dye was used to label unexpected. It might turn out to be a groundbreaking 生癌。這正是科學家能獲得女性掃描結果作調查的原因。
PSMA during the scan to detect cancer cells, but the discovery. 讀到這裡，你可能不明白為什麼經過了數千年的解剖，人們還是會遺漏在頭 References 參考資料：
dye also unexpectedly lit up a structure in the middle of 部中間長達四厘米的組織。若腺體暴露在外頭那就很容易會被發現，但因為這腺 [1] Valstar MH, de Bakker BS,
the head, an observation that perplexed the doctors [1]. 解剖學是生物學中歷史最悠久的領域之一。自古埃及以 體位於頭部深處，要深入到頭部中央一般需要使用內窺鏡檢查。另外，磁力共振 Steenbakkers RJHM, et al. The
Although they were initially convinced that it was 來，人們就開始解剖人體以了解其運作方式。幾千年來，我們 （MRI）或電腦斷層（CT）掃描不能偵測到這對腺體，僅在正電子掃描（PET）掃 tubarial salivary glands: A potential
just an aberration, they decided to look into it. Reading 對自己身體結構的理解日益加深，從古埃及人和古希臘人原 描中才能被發現​[2]。 new organ at risk for radiotherapy.
Radiother Oncol. In press.
through some more detailed anatomy textbooks, they 始的素描，到達文西詳細的圖紙，再進化到著名的參考書《格 doi:10.1016/j.radonc.2020.09.034
saw that the region that showed abnormal signals 雷氏解剖學》，都可以使我們對這個進程略知一二。但是，在 這對新唾腺的發現不僅改變了教科書中有關腺體的描述，而且還可能改變醫生 [2] Chesterton M. A new saliva gland,
is made up of salivary gland tissues but was never 過去的兩個世紀，解剖學領域的知識並沒有發生太大的變化。 治療頭頸癌的方法。唾腺對於吞嚥和說話很重要，因此醫生總是試圖避免在放射 Bill Bryson on the Human Body, and
labeled as such [2]. They also looked at scans from 當所有人，包括醫學專業人士，都相信我們已經完全了解所有 治療中對其造成損害，但是許多頭頸癌患者在治療後仍會感到口乾。這對曾經不為 the return of the Dust Bowl. BBC
other prostate cancer patients. To their surprise, all the 身體結構時，一組荷蘭科學家卻發現了一對新的唾腺。 人知的唾腺可能就是箇中原因，因為它們很可能在我們不知道其存在的情況下在 Inside Science. Updated October 29,
2020.
other 100 scans they examined displayed an area that 放射治療中被破壞。在一個超過 700 名患者參與的研究中，醫生發現在治療中對
lit up near the nose, with an average length of 4 cm [1]. 唾腺，顧名思義，功能是分泌唾液。唾液含有分解澱粉的 該唾腺使用的放射劑量與口乾感有關聯，說明這對新唾腺仍然有分泌唾液的功能​ [3] Bouchelouche K, Choyke PL, Capala
J. Prostate Specific Membrane
More interestingly, the scientists confirmed that 酶，而唾液本身可以作為潤滑劑幫助我們吞嚥食物。在這個 [1]。從現在開始，醫生可能會嘗試避免在放射治療中損害到這對唾腺。 Antigen—A Target for Imaging and
the same structure can also be observed in females, 突破性發現之前，人類已知有三對主要的唾腺，一對在耳朵 Therapy with Radionuclides. Discov
Med. 2010;9(44):55-61.
from the scan of a female patient [2]. While females 前面（腮腺），一對在下顎底下（頜下腺），另一對在舌頭底下 雖然這項發現可能不會改變大多數人的生活方式，但它提醒了我們在遇到出乎
do not have a prostate, there is a small tissue near the （舌下腺）；頭部和頸部周圍大約有 1000 個小腺體。這次發 意料的事情時要保持開放的態度，因為這說不定會帶來開創性的發現。
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