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السلام عليكم قبل فترة طلابنا سووا كروب لـحفظ القران الكريم خلال ٣ سنوات ، يعني مشروع يضمن انكم تتخرجون كأطباء وحفظة للقران الكريم لذلك لو حبيتوا تجون ، كل يوم نص ساعة فيعني الموضوع مراح ياخذ هواية من وكتكم بس متأكدد انه راح يفيدكم بآخرتكم والله https://t.me/amenaalmutawakelwn هذا رابط الكروب ، اذا تحبون انضموا او شاركوه الاصدقائكم أو على قنواتكم لان كل شخص حيشارك حيكون الكم اجره اليوم راح تكون بداية هالمشروع ان شاء الله ♥️ ، وموفقين يارب ♥️

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stem cell : is undifferentiated cell can replicate itself and generate offsprings of functional cell types differentiated There is 200 cell kind in body Most specilized Cells of : Liver /hepatocyte Heart/cardiomyocyte Brain/neuron The unique properties of stem cells 1. Stem cells are undifferentiated (unspecialized): One of the fundamental properties Has no specific tissue structure to perform function ماعدها شي (مركب) يميزها عن الانسجه الاخرى حتى تقوم بوظيفه خاصه لها cannot work with its neighbors to •pump blood through the body (like a heart muscle cell); •carry molecules of oxygen through the bloodstream (like RBC) •fire electrochemical signals to other cells that allow the body to move or speak (like a nerve cell 2. Stem cells are capable of dividing and renewing themselves for long periods: If cell replicate itself many times this process called proliferation 3. Stem cells can give rise to differentiated (specialized) cells: when unspecilized cell gives rise to specilized cell this process called DIFFERNTIATION Diffe. under control of: Internal signals controled by cell genes through trancription factors External signals including : ▪︎chemicals secreted by oher cells ■physical contact with neighboring cells, ■certain molecules in the microenvironment ... Cell potency is a cell's ability to differentiate into other cell types. The more cell types a cell can differentiate into, the greater its potency Unipotency Cell gives rise to only one cell type EX:myogenic stem cell Totipotency Cell develop to total organism Ex:zygote(fertilized egg) Multipotency Cell gives rise to small cell types EX.mesenchymal stem cell Pluripotency Cell gives rise to all cell types but not supporting structures(chorion.amnion.placenta) which are important for development Ex:embryonic stem cell . Asymmetric cell division Mechanism in stem cells to maintains their populations(similar to stem cell) and generating differentiated cells (have function) Occur when two daughter cells produced and differ in fate يحدث عندما خليتين تنتج وتختلف في التخصص (وحده تبقى stemواخرى تتخصص) one of mecanisms is [cell polarity] In which depends on certain proteins called cell fate determinate proteins (Ex.numb) and external signals transmitted by seven transmembrane receptors are involved in process ... Tissue culture Means growing of cells outside body in tubes ,dishes ,flaskes filled with nutrients liquid Under teperature controlled by incubators ,nourished by complex artificial media,exposed to concentrations of oxygen and carbondioxide Temperature -196c° in liquid nitrogen Vitro (in glass retrevant container made og glass) Vivo (inside living body) هاي كلمات لاتينيه Tissue cultur used for *Industrial production of hormones,growth factors ,therapy * growing cells under conditions . Renewal Stem cell has mechanism to prevents differentiation and promoting prolferation Studies on mouse embryonic stem cells result to mechanisms 1/TRANSCRIPTION FACTORS stem cell has self orgnized transcription factors network Which prevent differentiation and promotes proliferation this by proteins which their function on other effector proteins forming signal pathway for maintain ▪︎Cell survival ▪︎Cell entry to cell cycle Facilitate cell division هذه العمليه عن طريق بروتينتات وظيفتها تعمل على بروتينات مؤثره اخرىحتى يتم تفعيل مسار اشارات للحفاظ على بقائها ودخول الخليه الى cycle cell لتسهيل الانقسام Ex of transcription factors Nanog Oct-4 oct-3 Stat-3 Sox 2 2/Epigenetic mechanisms these mechanisms involve epigenetic modification of DNA, histones, or the chromatin structure in such a way that it changes the accessibility of the DNA to transcription factors Ex.proteins that silence genome by modifying histones(polycomb group of proteins) When stem cell differentiate ●Nucleus /stinking ●Chromatine/less relaxed than that of undiff cells ●allows the low-level expression of several genes that is characteristic of pluripotential cells ●open structure allows for the rapid regulation that is necessary for stem cells to respond to the needs of the organism.

Stem cell committent Cell commited to be differentiated to specific type this include intermediate cells Stem cell>progenitor cell>transit amplifying cell>precursor cell(blast)>differentiated mature cell Ex.HSCs Many steps beacause of gene expression process in which some genes on and other off by transcription factors ..... Stem cell niche The stem cell to be remains as stem cell and not differentiated into specific type there is menchanism called (Stem cell niche) Includes Extrinsic signsls Intrinsic signals

ملخص Stem cell part 1:

In histo. Sections .The lipid stored in adipocyte is lost by organic solvents as xylene...thin strand of meshwork seperates adjacent adopocyte represent ecm and cytoplasm In silver stains...show reticular fibers at angles which secreted by adipocytes Brown adipose tissue constiute 5% of newborn body in Back Shoulder Upper half spine But when grow decreased the tissue but remains in regions: Mediastinal Cervical Axillary Prevertebral Abdominal In adults disappear except from Kidney Mediastinal Adrenal glands Aorta Neck Intrascapular Prevertebral

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🛑 simple acinar gland طبعا هنا الterminal portion يكون بشكل Sephrical or elongated sac ⭕️ simple stright acinar gland تتكون من acinous وحدة بس مرتبطة بexcretory duct ⭕️ simple branched acinar gland تتكون من acinous متفرعة الى عدة تفرعات