Pankreasın Histolojik Yapısı ve Fizyolojisi
Özet
Pankreas, karın üst kadranda midenin arkasında yer alan, hem ekzokrin hem de endokrin fonksiyonlara sahip karmaşık, ikincil bir retroperitoneal organdır. Fibröz bir kapsülü bulunmayan bu organ; kafa, boyun, gövde ve kuyruk olmak üzere dört makroskopik bölüme ayrılır. Pankreas kütlesinin %95'inden fazlasını oluşturan ekzokrin bileşen; duodenuma salgılanmak üzere su, bikarbonat ve tripsinojen, amilaz, lipaz gibi sindirim enzimlerini içeren pankreas öz suyunu üretir. Bu salgı, Wirsung kanalı vasıtasıyla duodenuma ulaştırılır. Kütlenin %1-2'sini oluşturan endokrin bileşen ise Langerhans adacıkları olarak adlandırılan hücre kümelerinden meydana gelir. Bu adacıklarda bulunan alfa hücreleri glukagon, beta hücreleri insülin, delta hücreleri ise somatostatin hormonlarını sentezleyerek doğrudan kana salgılar ve enerji metabolizmasını kontrol eder. Embriyolojik olarak duodenum endodermal epitelyumundan ventral ve dorsal iki tomurcuk halinde gelişen bez, gebeliğin yedinci haftasında birleşir. Bu birleşmenin gerçekleşmemesi en yaygın konjenital varyant olan pankreas divisumuna yol açar. Hücresel Ca2+ hemostazı, asiner hücrelerin uyarılması ve ekzositoz yoluyla enzim salgılanmasında anahtar rol oynarken; patolojik durumlarda aşırı Ca2+ yüklenmesi hücre hasarına ve pankreatit gelişimine neden olabilmektedir.
The pancreas is a complex, secondary retroperitoneal organ located behind the stomach in the upper abdomen, exhibiting both exocrine and endocrine functions. Lacking a fibrous capsule, the organ is macroscopically divided into four parts: head, neck, body, and tail. The exocrine component, comprising over 95% of the pancreatic mass, synthesizes pancreatic juice rich in water, bicarbonate ions, and digestive enzymes such as trypsinogen, amylase, and lipase, which are delivered to the duodenum via the Wirsung duct. Conversely, the endocrine component accounts for 1-2% of the mass and consists of clusters known as the islets of Langerhans. Within these islets, alpha cells secrete glucagon, beta cells secrete insulin, and delta cells secrete somatostatin directly into the bloodstream to regulate energy metabolism. Embryonically, the pancreas develops from the endodermal epithelium of the duodenum as ventral and dorsal buds that fuse during the seventh week of gestation; failure of this fusion results in pancreas divisum, the most common congenital variant. Cellular Ca2+ homeostasis plays a pivotal role in acinar cell stimulation and enzyme secretion through exocytosis, whereas pathological Ca2+ overload poses a risk of cellular damage and pancreatitis development.
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