Momwe Chiwindi Chimapangira Ndudu
Chiwindi ndi chimodzi mwa ziwalo zotanganidwa kwambiri m'thupi la munthu. Kuwonjezera pa ntchito yake yochotsa poizoni m'thupi, kusunga mphamvu, ndi kusintha kagayidwe kachakudya m'thupi, chiwindi chimagwiranso ntchito yofunika kwambiri, yomwe nthawi zambiri imanyalanyazidwa: kupanga ndulu. Ndulu ndi madzi ofunikira m'mimba kuti athandize thupi kugaya mafuta ndi kuyamwa mavitamini ena. Njira yopangira ndulu si njira yosavuta; imaphatikizapo njira zingapo zovuta zamoyo, kuyambira pamlingo wa maselo mpaka dongosolo la ndulu. Nkhaniyi ikufotokoza momwe chiwindi chimapangidwira ndulu, zigawo zake, momwe chimayendera m'matumbo, komanso chifukwa chake njirayi ndi yofunika kwambiri pa thanzi.
Kodi ndulu ndi chiyani ndipo n'chifukwa chiyani ili yofunika?
Ndulu ndi madzi obiriwira ngati achikasu omwe amapangidwa nthawi zonse ndi chiwindi . Ntchito yake yayikulu ndikugawa mafuta m'madontho ang'onoang'ono kuti ma enzymes ogaya chakudya (lipases) agwire ntchito bwino. Popanda ndulu, kugaya mafuta sikokwanira, zomwe zimapangitsa kuti thupi lizitha kuyamwa mafuta acids ndi mavitamini osungunuka mafuta monga mavitamini A, D, E, ndi K.
Kupatula kuthandiza kugaya chakudya, ndulu imagwiranso ntchito ngati njira yochotsera zinyalala zina. Mwachitsanzo, bilirubin (chopangidwa ndi hemoglobin yosweka), cholesterol yochulukirapo, ndi zinthu zina za kagayidwe kachakudya ndi mankhwala zimatha kutuluka kudzera mu ndulu. Chifukwa chake, ndulu sikuti imangogwira ntchito pakugaya chakudya komanso "ukhondo" wa thupi.
Zigawo zazikulu za ndulu
Manyowa si "madzi ogaya chakudya" okha, koma ndi chisakanizo chovuta chomwe chili ndi:
1. Mchere wa bile: umachokera ku ma asidi a bile opangidwa kuchokera ku cholesterol. Ndi gawo lofunika kwambiri pakupanga mafuta.
2. Ma phospholipids (makamaka lecithin): amathandiza kupanga ma micelles okhala ndi mchere wa ndulu, zomwe zimathandiza kuyamwa mafuta.
3. Cholesterol: Cholesterol ina imatuluka mu ndulu. Kuchuluka kwambiri kungayambitse kupanga miyala ya ndulu.
4. Bilirubin: utoto womwe umachokera ku kusweka kwa maselo ofiira a magazi, zomwe zimapangitsa kuti ndulu ikhale ndi mtundu wake.
5. Ma electrolyte ndi madzi: zimapangitsa kuti ndulu ikhale yamadzimadzi kwambiri kuti iyende mosavuta kudzera mu duct ya ndulu.
6. Mapuloteni ndi zinthu zina: kuphatikizapo zinyalala zina za kagayidwe kachakudya ndi mankhwala omwe amafunika kutulutsidwa.
Kapangidwe ka ndulu kamasintha malinga ndi momwe thupi lilili, zakudya, komanso momwe mahomoni ogaya chakudya amagwirira ntchito.
Ndani "amapanga" ndulu m'chiwindi?
Ma ndulu amapangidwa ndi maselo a chiwindi otchedwa ma hepatocytes. Ma hepatocytes amapanga minofu yambiri ya chiwindi ndipo amagwira ntchito ngati mafakitale a biochemical. Amatenga zinthu zopangira kuchokera m'magazi, kuzikonza, kenako amapanga ndulu, yomwe imatengedwa kudzera m'mitsempha yaying'ono mkati mwa chiwindi.
Kuwonjezera pa ma hepatocytes, palinso maselo a epithelial mu ducts ya bile otchedwa cholangiocytes. Ma cholangiocytes sapanga ndulu kuyambira pachiyambi monga ma hepatocytes, koma "amasintha" ndulu—monga kuwonjezera madzi ndi bicarbonate—kuti kuchuluka ndi mawonekedwe a ndulu athe kusinthidwa kuti akwaniritse zosowa za m'mimba.
Magawo a chiwindi omwe amapanga ndulu
1. Kupanga asidi ndulu yochokera ku cholesterol
Gawo lofunika kwambiri pakupanga bile ndi kupanga ma bile acid. Ma bile acid amapangidwa kuchokera ku cholesterol kudzera mu ma enzyme osiyanasiyana mu hepatocytes. Enzyme imodzi yofunika kwambiri panjira imeneyi ndi cholesterol 7α-hydroxylase (CYP7A1), yomwe imayang'anira kuchuluka kwa bile acid yomwe imapangidwa.
Ma asidi a bile omwe apangidwa kumene amatha kusakanikirana (kuphatikiza) ndi ma amino acid monga glycine kapena taurine. Njira yolumikizirana iyi imapangitsa kuti ma asidi a bile asungunuke kwambiri m'madzi komanso akhale othandiza kwambiri pothandiza kugaya mafuta. Pambuyo polumikizana, ma asidi a bile omwe amapezeka nthawi zambiri amatchedwa mchere wa bile.
2. Kutulutsa kwa zigawo za ndulu mu ndulu canaliculi
Zigawo za ndulu zikapangidwa, ma hepatocyte amawatulutsa m'njira zazing'ono kwambiri zotchedwa bile canaliculi. Ma canaliculi awa ndi "ma ngalande" ang'onoang'ono omwe ali pakati pa ma hepatocyte. Apa ndi pomwe ndulu imayamba kuyenda.
Kuyenda kwa bile kumafuna kuti zinthu zosiyanasiyana zonyamula (mapuloteni osamutsa) zigwire ntchito pa nembanemba ya maselo a hepatocyte. Mchere wa bile, conjugated bilirubin, phospholipids, ndi zinthu zina zimapopedwa mu canaliculi. Kuyenda kwa zinthuzi kumakopa madzi ndi ma electrolyte, kuonjezera kuchuluka kwa bile ndikuchepetsa mokwanira kuti iyende.
3. Kusintha kwa ndulu ndi maselo a ndulu
Ndulu yomwe poyamba imapangidwa ndi ma hepatocytes imatchedwa ndulu yoyambirira. Pamene imadutsa m'mitsempha ya ndulu ya intrahepatic (mitsempha ya ndulu mkati mwa chiwindi), ma cholangiocytes amatha kuwonjezera bicarbonate (HCO₃⁻) ndi madzi. Kuwonjezera bicarbonate kumathandiza kuchepetsa asidi m'mimba pamene zomwe zili m'mimba zimalowa m'matumbo ang'onoang'ono, zomwe zimapangitsa kuti matumbo azikhala abwino kwambiri kuti ma enzyme a m'mimba azigwira ntchito.
Kulamulira kumeneku kumakhudzidwa ndi mahomoni monga secretin, omwe amalimbikitsa njira za bile kupanga madzi okhala ndi bicarbonate.
4. Kusunga ndi kuyika kwambiri mu ndulu
Ngakhale kuti ndulu imapangidwa mosalekeza, si nthawi zonse imapita mwachindunji m'matumbo. Ngati palibe chakudya, makamaka zakudya zamafuta, ndulu nthawi zambiri imasamutsidwira ku ndulu kuti ikasungidwe. Mu ndulu, ndulu imakhala yowunjikana: madzi ndi ma electrolyte ena amayamwanso, zomwe zimapangitsa ndulu kukhala yokhuthala komanso yamphamvu kwambiri ikafunika.
5. Kutuluka kwa ndulu m'matumbo ang'onoang'ono panthawi yodya
Mukadya, makamaka zakudya zokhala ndi mafuta, matumbo anu ang'onoang'ono amatulutsa mahomoni otchedwa cholecystokinin (CCK). Mankhwalawa amachititsa kuti ndulu igwire ntchito ndikutulutsa bile mu duct yayikulu ya bile, yomwe imalowa mu duodenum (gawo loyamba la matumbo ang'onoang'ono). Nthawi yomweyo, CCK imathandizanso kumasula sphincter ya Oddi, "valve" yomwe imalamulira kuyenda kwa bile ndi madzi a kapamba m'matumbo.
Pambuyo poti ndulu yalowa m'matumbo ang'onoang'ono, mchere wa ndulu umagwira ntchito yawo: kupanga ma micelles, kumangiriza mafuta ndi mavitamini osungunuka m'mafuta, kenako kunyamula zinthu zogaya chakudya pamwamba pa matumbo kuti zilowe.
Kuzungulira kwa magazi m'thupi: ndulu "imagwiritsidwanso ntchito"
Chochititsa chidwi n'chakuti thupi silitulutsa mchere wonse wa ndulu mutagwiritsa ntchito. Ambiri mwa iwo amatengedwanso m'gawo lomaliza la matumbo ang'onoang'ono (ileum) ndikubwereranso ku chiwindi kudzera mu mtsempha wa portal. Njira imeneyi imatchedwa enterohepatic circulation.
Njira imeneyi ndi yothandiza kwambiri. Mchere wa m'matumbo ukhoza kugwiritsidwanso ntchito kangapo patsiku. Chiwindi chimangofunika kupanga ma asidi atsopano a m'matumbo kuti chilowe m'malo mwa omwe atayika m'ndowe. Njira yobwezeretsanso imeneyi imathandiza thupi kusunga mphamvu ndikusunga mchere wa m'matumbo womwe ulipo kuti ugaye chakudya.
Kodi chimachitika ndi chiyani ngati kupanga kapena kuyenda kwa ndulu kwasokonekera?
Kusokonezeka kwa kupanga kapena kuyenda kwa ndulu kungayambitse mavuto osiyanasiyana azaumoyo, mwachitsanzo:
– Cholestasis (kutseka kutuluka kwa bile): kungayambitse kuchuluka kwa bilirubin ndi mchere wa bile m'magazi, zomwe zimayambitsa kuyabwa pakhungu, mkodzo wakuda, ndowe zotumbululuka, ndi jaundice.
– Miyala ya m'matumbo: nthawi zambiri imachitika pamene ndulu yadzaza kwambiri ndi cholesterol kapena pali kusalinganika kwa kapangidwe ka ndulu.
– Kulephera kuyamwa mafuta: kusowa kwa ndulu kungayambitse ndowe zamafuta (steatorrhea) komanso kusowa kwa mavitamini A, D, E, K.
– Kuwonongeka kwa chiwindi kapena ndulu: monga chiwindi cha chiwindi, matenda a chiwindi, kapena kutupa kwa ndulu kungakhudze kupanga/kunyamula ndulu.
Popeza ndulu imagwira ntchito m'kugaya chakudya ndi kuchotsa zinyalala, matenda a ndulu nthawi zambiri amakhudza kwambiri, osati m'mimba mokha komanso pakhungu, mphamvu, ndi kagayidwe kachakudya.
Kutseka
Kupanga ndulu ndi chiwindi ndi njira yogwirizana kwambiri. Ma hepatocytes amapanga ma asidi a ndulu kuchokera ku cholesterol, amatulutsa mchere wa ndulu ndi zinthu zina zosiyanasiyana mu bile canaliculi, kenako amasintha nduluyo m'mitsempha ya ndulu isanasungidwe ndikuyiyika mu ndulu. Zakudya zamafuta zikamezedwa, ndulu imatulutsidwa m'matumbo ang'onoang'ono kuti ithandize kugaya mafuta ndi kuyamwa mavitamini. Pambuyo pogwiritsidwa ntchito, mchere wambiri wa ndulu umabwezeretsedwanso kudzera mu enterohepatic circulation.
Kumvetsetsa momwe chiwindi chimapangira ndulu kumatithandiza kuona kuti chiwalochi si "fyuluta ya poizoni" chabe, koma ndi chinthu chofunikira kwambiri chowongolera kagayidwe kachakudya ndi kugaya chakudya. Kusunga thanzi la chiwindi kudzera mu zakudya zoyenera, kuchita masewera olimbitsa thupi, komanso kuyezetsa thanzi lanu mukakumana ndi vuto la kugaya chakudya kapena zizindikiro za jaundice ndi njira zofunika kwambiri kuti ndulu igwire bwino ntchito.
