Histology Notes PDF 2024

3 Baree Abu ghanam. Mohammad kiswani Ghada abu alghanam.  ‫بما انه اجت بعض االستفسارات عن مواضيع بالشيت‬ ‫الماضي رح نحطهم هون ون...

3 Baree Abu ghanam. Mohammad kiswani Ghada abu alghanam.  ‫بما انه اجت بعض االستفسارات عن مواضيع بالشيت‬ ‫الماضي رح نحطهم هون ونوضح افكارهم‬ ‫‪Why does the action potential start from the apex of the heart? If it started from base, the‬‬ ‫‪contraction would begin from the top and close the valves, causing blood to remain in the heart.‬‬ ‫‪Therefore, it needs to start at the apex to squeeze all the blood upward toward the major‬‬ ‫‪openings and major blood vessels.‬‬ ‫الفكرة ببساطة انه بحكيلنا ‪ AP‬ببلش من ال ‪ SA node‬الي موجود باألذين ببعث اإلشارات لينقبض االذين وبنفس الوقت ببعث إشارات‬ ‫للبطين بنقل ال ‪AP‬عبر ال ‪ junction‬ليوصل لل ‪ventricles‬هناك بس يوصل ال ‪ AP‬بكون اتجاه االنقباض من ال ‪ apex‬ليطلع‬ ‫الدم منه عبر الشرايين ألجزاء الجسم الي خربطتو فيها انه طيب بصير عندي انقباض لل ‪ atria‬وين اتجاهه همه الثنين منفصلين ال تنسوا‬ ‫ف االذين أصال بنقبض قبل البطين‪.‬‬ ‫فكرة بسيطة ركزوا عليها انه ال ‪ capillary‬ما فيها ‪smooth muscle‬‬ ‫ألنه همه مواقع تبادل الغازات والغذاء فهذول اذا كانوا موجودين بتكوينها‬ ‫بعيقوا عملية التبادل تبعهم‪.‬‬ ‫‪Structures that they are subject to low pressure, you will see relatively thicker walls, you will see‬‬ ‫‪smooth muscles, when structures with less pressure, you will see bigger lumens, thinner walls,‬‬ ‫‪ ( some smooth muscles.‬تنسوش انه السماكة مرتبطة بكمية العضالت بالوعاء)‬ ‫هون كان يحكي عن عالقة الضغط مع األوعية الدموية‪ ،‬يمكن خربطتو بين انه كاتب ‪ low and less‬فالمفهوم انه الثنين ضغط قليل بس‬ ‫ال هو قصده انه ال ‪ low‬يعتبر ‪ high‬مقارنة بال ‪less‬‬ ‫هسا لما بدنا نفهم عالقة توسع وتضيق األوعية احنا لما يرتفع الضغط الي سبب شو ما كان الجسم بعمل رد فعل بحيث انه يعمل انقباض‬ ‫للوعاء الدموي ليحسس الجسم انه فيه اشي غلط قاعد بصير وبعدها بعمل على توسيع الوعاء الدموي عشان يقل الضغط والحكي نفسه‬ ‫النخفاض الضغط مع عكس الرياكشن الي بعمله‬ ‫مثال حكته الدكتورة انه في الشتا بتحس العروق مبينه ليه؟ من البرد بصير توسع لالوعيه عشان تعوض الدم وتزيد الحرارة وتنبه الجسم‬ ‫انه فيه اشي غلط تحرك بما انه الضغط منخفض فبعدها بصير تضيق لألوعية عشان يزيد الضغط وليحافط عالحرارة كمان‪.‬‬ ‫هسا بدنا نفهم شغله انه الضغط يعني قوه دفع الدم لجدران الوعاء الدموي إذا ضيقنا الوعاء زاد الضغط وإذا وسعناه قل الضغط‬ ‫اما تدفق الدم ملوش دخل بالضغط يعني إذا وسعنا الوعاء زاد التدفق ولما نضيقه بقل التدفق (كمية الدم الي بتمشي بالوعاء)‬ ‫لتفهموا قصة الضغط فرقو بين السبب ورد الفعل يعني هو زاد الضغط ألنه ضيقت الوعاء بس رد الفعل تبعه توسيع الوعاء طولت شوي‬ ‫بالقصه بس النه الدكتورة ركزت عالقصة حبتين‪.‬‬ ‫‪Note:‬‬ ‫ال ‪ endothelium‬كتير مهم مش بس لل ‪ lining‬وال ‪ covering‬بل اله دور ف تصلب الشرايين مثال عندي شخصين طبيعة غذائهم‬ ‫نفس الغذاء ما بفرقو عن بعض وبعملو رياضه وبشرب مي يعني حياتهم صحيه ولكن واحد منهم ال ‪ endothelium‬عنده بجمع الدهون‬ ‫وبراكينها على شكل أشياء كبيره بحيث بتعيق وصول الدم لباقي األجزاء األخرى من الوعاء الدموي ففي دم بوصل فبنشف الوعاء‬ ‫وبتصلب وبصير عندي ‪.atherosclerosis‬‬ ‫أهمية ال ‪ elastic fibers‬أنه لما اشد الوعاء الي بتكونه رح يرجع لنفس الشكل‪.‬‬  Capillaries The capillaries are the smallest vasculature. And when we say the smallest vasculature, you would expect the thinnest walls. That means you're not going to see a typical intima, media, adventitia, everything is shrunking down to as small as possible, why is that? Because the capillaries are the sites where exchange will occur between them or between the blood inside and the external environment (surrounding tissue). So, simply what is the capillary made of? *Endothelium, and deep in the endothelium, we're not going to have the typical connective tissue that we said, which is the most connective tissue. Instead, we're going to have the basement membrane, Basement membrane, that's the structure we see when we look at it at a light microscope, and when we look at this structure by electron microscope, we will see lamina (basal lamina), and sometimes scattered pericytes. basal lamina ‫ وطبقة داخلية‬reticular lamina ‫ بتكون من طبقتين خارجية اسمها‬basement membrane ‫ ال‬:‫توضيح‬ Sometimes you're going to see scattered cells that are called pericytes (mesenchymal cells\ progenitor), They are quite important, more precisely, in the brain tissues, and usually, they have their own basement membrane, fuse with the basement membrane of the endothelium. What are progenitor cells? Stem cells, cells haven't reached their destination. Simply, sometimes those cells could differentiate into smooth muscle cells. They can give us stem cells. Can we use them interchangeably, progenitor and stem cells? Not much. Because the stem cells, they are way behind in the differentiation. They are a bit more advanced. ‫ وللي انقسمت‬fertilised oval ‫ اللي هي ال‬one stem cell ‫باالمبريو كان في عنا‬ 2 cells then 4 then 8 then 16 cells but that division doesn't continue endlessly we have to reach the bilaminar stage then the trilaminar stage ‫ ب‬trilaminar stage ‫ بنسميهم بال‬layers ‫هذول ال‬ 1. endoderm 2. Mesoderm 3. ectoderm. ‫ اللي بالجسم‬tissues ‫ طبقات بطلع عندي كل ال‬٣‫من هذول ال‬ Now why are these cells differentiating? Because there is a final target that they need to reach (muscle cells, liver cell, etc...) but few steps before that there was no final differentiation there was progenitor (stem cells)how close them to their ancestors that determines how progenitor they are how stem they are and the pericytes in one of them.  The average diameter of capillaries varies from 4 to 10 µm (those are quite tiny in diameter), and this corresponds to the diameter of the blood cells. Two cells cannot pass at the same time. Two RBCs or two WBCs can't pass through the capillary at the same time. These minute vessels make up over 90% of the body’s vasculature. Permit and regulate metabolic exchange between blood and surrounding tissues. They allow the passage of the nutrients and the gases. and they allow the travel back of the waste products to the blood. So, it can be brought back to the heart one more time and sent to the filtration sites the kidneys, and the liver..‫الصورة مهمة جدا‬ Arteriole is the smallest vessel in the arterial end, the tunica media of them 1 to 2 smooth muscle layers. We have the endothelium resting on an extremely tiny amount of sub-endothelial tissue, and another extremely thin adventitious, we did say that those are the determinants of the blood pressure in the human circulation. Now, the arterioles mark the microvasculature of the human body. Remember, this is quite important. They are the beginning of the microvasculature. At the end of the arterioles, we have a tiny vessel in the metarterioles. Now, from the metarterioles, the blood will flow toward the capillaries. We have what we call Precapillary sphincters its smooth muscles, So the contraction of these will allow or not allow the blood to flow from the metarterioles toward the capillaries, if these are constricted, the capillaries will not receive the blood. So, what will happen? Will the blood retain in the metarterioles? No, it will not. It will pass it through what we call the thoroughfare channel, and then it will be delivered to the venous end that we call postcapillary venule. The capillaries usually, they don't appear as one single structure. Usually, they make this network of capillaries that called capillary bed.  We have two types of electron microscopes. One we call transmission penetrates specimens and sees details, the second type we call scanning electron microscope, this is when we record the topography of the specimen. You don't see the interior. You see the surface in 3D images. But organelles, we cannot see them with a light microscope. We only use the transmission microscope if we want to see the interior. In this we use transmission electron microscope, This is simply a capillary. it's incorrect that I say basement membrane Because when we look at electron microscope, what does the abbreviation say here? BL stands for basal lamina. So that's the basal lamina of the endothelial cells. And this is a pericyte. we say it has its own basal lamina, which is usually fused with the one of the endothelia. Types of capillaries: Capillaries are generally grouped into three histologic types, depending on the continuity of the endothelial cells and their basement membrane. Usually, endothelial cells, they are quite adhered to each other. What helps endothelial cells adhere to each other? There is something extremely important, the junction complexes prevent the paracellular movement, anything that passes through must enter the cell by transcytosis, and then go to the venous end..‫إذا بقسمهم حسب قوة ارتباط الخاليا فبعض‬ 1. In the first type, it's tight, which is called continuous. This is the one we know that's the typical epithelial reast or basement membrane. Will adhere, contact, and diffuse endothelial cells with perfect, sound basement membrane, this is the most common type of capillary and is found in muscle, connective tissue, lungs, exocrine glands, skin, brain and nervous tissue. 2. In the second type, the junction should be less tight (sieve-like structure), slight modification we're going to make it leaky, those are called the fenestrated, the basement membrane is continuous and covers the fenestrations (A thin membrane of proteins material that will cover them), where exactly is this fenestrated? In the junction between the endothelial cells, It's slightly loose. Even the endothelial cells themselves have these pores. Fenestrated capillaries are found in organs with rapid interchange of substances between tissues and blood, such as kidneys, intestine, choroid plexus in the brain, and endocrine glands. Why do we need fenestrated capillaries in the kidneys? Blood reaches the kidney from one end then it will undergo filtration which needs to release some of the large molecules, if we have continuous capillary here the large molecules won’t be able to leave out, that’s why we need it..‫ خذ نفسا عميقا وحاول مرة أخرى‬،‫حلمك ليس له تاريخ انتهاء‬ Note:.‫معلش طويل شوي بس بخلص شدو حيلكم كم ساليد ضل بسيطين‬ We have two types of glands, one with ducts and one without ducts. The ones with ducts are called Exocrine glands. And the ones without ducts Endocrine. The exocrine gland has continuous capillary. 3. In the third type, that's the leakiest, the fenestrated huge. And the basement membrane, it's not continuous. Discontinuous capillaries (sinusoids), they are found in the liver, spleen, some endocrine organs, and bone marrow. Why do I have in the liver spleen with bigger sizes? Because there's a lot of cellular movements. Also, the bone marrow that will synthesize the new blood cells that they have to reach the blood, the capillaries in the bone marrow are of this type to allow the transfer, to allow the passage of these cells from the bone marrow to work the blood. Watch this video which summaries the three types we've talked about previously: https://youtu.be/hSkIG4MdKqU?feature=shared Special Capillaries structures Arterial end breaking into terminally. The arterioles will give what is called the metarterioles. At the end of the metarterioles, we will have the capillaries. At the venous end of the capillary, where the blood will flow back to the systemic circulation. Within the capillaries, we have another type regarding how the blood flows.  *Arteriovenous shunts: arterioles that can bypass capillary networks and connect directly to venules, thermoregulation by the skin Involves arterioles that can bypass capillary networks and connect directly to venules. The media and adventitia are thicker in these arteriovenous shunts richly innervated by sympathetic and parasympathetic nerve fibers. The autonomic fibers control the degree of vasoconstriction at the shunts, regulating blood flow through the capillary beds. High capillary blood flow (vasodilation) in the skin allows more heat dissipation from the body, while reduced capillary blood flow (vasoconstriction) conserves heat that’s important functions when the environmental temperature is hot or cold, respectively The temperature of the blood. It's the one that keeps us warm and keeps the internal organs intact. If we have hypothermia, this is quite serious If it stands for a longer period, this is good enough to kill you. This is what happens when you are in a real cold area. *Portal system: We see it in two locations, one of them is the liver. What happens in the liver? The first capillary bed located in the GI tract, Blood supply to the GI tract comes, and the drainage of the blood of the GI tract, it's not going to enter the systemic circulation. In the GI tract, I have absorbed a lot of food that I have ingested. Those materials cannot enter the systemic circulation directly. Where do they go? To the liver. The portal hepatic vein goes to the liver. Then it will break into sinusoidal capillaries (the second capillary bed), in the liver cells have hepatocytes on each side. They will work on the incoming blood from the GI tract. After they've done their work, the blood from the liver goes to the systemic circulation. It goes to the heart. The heart pumps it to the lungs to load it with more oxygen. It goes back to the heart again. Then we pump it, load it with nutrients and load it with oxygen. Note: What is the difference between infection and inflammation? Inflammation: Is the reaction of the immune system, for example: when you wear a jewelry made of material you have an allergic for, you'll have an inflammation. Infection: it's happened when bacterial causes take place.  Venules The first venule starts after the capillary, we call it postcapillary venule, their structure is like the capillary. But when it becomes bigger, it starts to show smooth muscle, Diameter is 15 -20 μm. What is special about the first step in the venous end, which is the postcapillary venules, is the site where the white blood cells can leave the circulation to deal with diseases If we have an inflammation or if we have an infection. Postcapillary venules converge into larger collecting venules that have more distinct contractile cells. With increasing size venules become surrounded by a recognizable tunica media with two or three smooth muscle layers and are called muscular venules. A characteristic feature of all venules is the large diameter of the lumen compared to the overall thinness of the wall. ‫ الي هيه الفتحة تبع‬lumen ‫العالقة عكسية بين سمك الجدار وحجم ال‬ ‫الوعاء‬ After muscular venules they start small, medium, large veins, the change in the structure will happen gradually. We talk about the blood, leave the arterial end of the capillary, then enter the post- capillary venules, from the post-capillary venules to the collecting venules and then muscular venules, then the small, medium, and the large. Vein Blood entering veins under very low pressure and moves toward the heart by contraction of the smooth muscle fibers in the media and by external compressions surrounding skeletal muscles and other organs. from In medium-sized veins we see Tunica Intima typical endothelial cells resting on a small amount of sub-endothelium connective tissue, in vein thinner than the artery. Also, the media at the artery is thicker than the veins. The external or adventitial is thick relative to the media.  Who is thicker in the Medium-sized muscular artery? The medium. The media has small bundles of smooth muscle cells mixed with reticular /elastic fibers, the adventitia rich with collagen, some smooth muscles and vasa vasorum. large veins: venous trunks, paired with elastic arteries well-developed intima thicker than the medium size, thin media and a thicker adventitia, Internal elastic lamina may be present Large and medium veins have valves: thin, paired folds of tunica intima projecting across the lumen, rich in elastic fibers. We also have valves that control the passage of the blood, why is it important in the veins? Precisely in the lower part of the body, I am trying to allow the blood to pass upwards and not to go backwards. It prevents it from a back flow. The thickness of the veins is quite thin. Smooth muscles can be too small. The contraction of the veins is not strong enough to contract and pull them up. But how do we move blood upward? In the lower part. Of course, the upper part is easy. The contraction of the skeletal muscles. When it contracts, it squeezes the blood up. What prevents it from going back? The valves. ‫( الصمام تبعه بكون مش شغال فبعمل انه الدم‬Varicose veins( ‫الناس الي عندها دوالي‬.‫يضل متجمع تحت بالوريد وبتمدد وبطول وبزيد القطر تبعه‬ ‫ للقلب بساعد على انه الدم ما يضل تحت ويطلع بالوريد ميرجعش‬relaxation ‫باإلضافة إنه‬.‫يضل ماشي باتجاه واحد‬  LYMPHATIC VASCULAR SYSTEM It is like a parallel type of vasculature, cause not all the fluid go back to the postcapillary venules. A system of very thin-walled channels, collect excess interstitial fluid from the tissue spaces and return it to the blood. Lymph is rich in lightly staining proteins but does not contain RBCs. Most tissues contain lymphatics (exceptions: bone marrow and most of the CNS) Lymphatics originate locally as tubes of very thin endothelial cells which lack tight junctions and rest on a discontinuous basal lamina, anchored by collagen to the surrounding CT (prevent collapse). Lymphatics converge into larger vessels with thin walls and increasing amounts of connective tissue and smooth muscle (no clearly distinct outer tunics). Have valves comprised of complete intimal folds. ‫هسا هاذ النظام هو عبارة عن حويصالت بتجمع السوائل الي ما بوخذها الدم فهو جداره كثير رفيع وفيو صمامات عشان يقدر يخليهم يفوتوا‬ ‫جواته‬ ‫ انها‬back flow ‫ بخليهم فاتحين ألنهم لو كانوا مسكرين بصير مش سهل للسوائل اللي بتعمل‬collagen fibers ‫ تبع ال‬anchoring ‫ال‬ going forward ‫تكمل وتضل‬ ‫ النه ما في عنا‬fluid running forward ‫ وال ال‬patency ‫ ما بقدروا يحافظوا على ال‬extremely thin walls ‫وعشان عندهم‬ muscles And that's why we need the valves which help us guarantee the flow of the lymphatic towards the venous end ‫ فيه كبير كثير‬capillaries ‫ النه ال‬bone marrow ‫ بال‬lymphqtics‫وكمان شغلة انه ما بنحتاج ال‬ and the bone marro has a good amount of interstitial fluid and this just not gonna break what it's going on, the lymphatics doesn't contain any RBCs (it's a clear yellowish fluid) ‫الصبغة مهم اسمها‪ +‬انه بميز ال ‪ LV‬عن ال ‪ venule or Arteriors‬من وجود ال ‪.RBCs‬‬ ‫الدكتورة شرحت الكونسبت هاذ ب خمس دقايق‪.‬‬ ‫شوية أسئلة حطتهم الدكتورة بأخر‬ ‫المحاضرة وحكت اغلب اسئلتها خيارات‬ ‫اإلجابة بتيجي طويلة‪.‬‬  ‫وإن كان األمر معقد فلطف هللا ممتد‪.‬‬ ‫يعطيكم العافية معلش طويل حبتين بس ان شاء‬ ‫هللا يكون ساعدهم وفهمتوا بالتوفيق دفعة‪.‬‬ ‫جدول مهم الدكتورة حكت بلخص الي اخذناه المحاضرة الماضية ‪ +‬القطر(األرقام) مش المطلوب‬ ‫والترتيب من األكبر لألصغر حجم بالجدول (من فوق لتحت)‬  ‫ملخص موجود بأخر الكتاب ممكن يفيدكم‪:‬‬ ‫تمت كتابة هذا الشيت صدقة جارية عن روح والدة زميلنا عمرو رائد من دفعة تيجان‬ ‫دعواتكم لها بالرحمة والمغفرة‬ ‫‪Thank you‬‬