Microscopic Structure of Lungs 2024-2025 Lecture Notes PDF

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These lecture notes cover the microscopic structure of the lungs, focusing on the respiratory system, conducting passages, and respiratory histology. The document includes learning objectives, key information, and diagrams.

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Block 1.3 lectures 2024-2025 lecture Highlighter key Writer Reviewer...

Block 1.3 lectures 2024-2025 lecture Highlighter key Writer Reviewer Doctor explanation Abbreviation Key information Book >> >> Musa Al-Ali Amirah Alhassan Lein Al-Shafei Student explaintion 221-222-223 notes References Deleted Learning objectives Identify and describe the histological structure of: upper & lower respiratory zones The respiratory epithelium in the upper airways The bronchial tree at the level of bronchi Respiratory system : to Clean, Conduct & Condition air Conducting & respiratory passages Respiratory system is divided depending on 2 types of classification -Anatomical -physiological and histological the anatomical classification Upper RT Lower RT The remaining part of Until the level of the larynx. respiratory tract. The functional and histological classification Conducting passages Respiratory passages Conduct the air: Facilitate the movement of air to and from the lungs Responsible for the process of the respiratoin (gas exchang) Clean the air: Remove dust, debris, and other particles. the Fictional zone of this zone is AlVEOLI Counditing the air: to make the air warm and humidified to Protect the air from the delicate structure of RT humidified= ‫مرطب‬ Note:gas exchange occurs in this zone Start from the nose and end at the terminal bronchiole Note: No gas exchange in this zone and No alveoli in this zone Respiratory portion 221- notes: Terminal bronchiole vs Involved in gaseous exchange Respiratory bronchiole: They are structurally the same, but respiratory bronchiole has alveoli that are not in terminal Terminal bronchiole. bronchiole Respiratory bronchioles: continue with alveolar respiratory ducts; ducts consist of bronchiole alveoli (Linear arrangement of alveoli) Alveolar duct These ducts end in alveolar sacs which are alveoli arranged in a circular manner and alveoli open in a loose sac, that is why we called them Alveolar sac alveolar sacs. Like grape. Respiratory system Whenever you see the terminal bronchiole, remember: It is the last station of the conducting zone. ‫فيما سبق‬: why we called it pseudostatified? Cells have different heights but all rest on the basement membrane. The nuclei appear at multiple levels, giving a false appearance of stratification. and we called it columnar because the major cells are coulmnar ,,and ciliated because Most cells have an apical surface with cilia. The cilia help in moving mucus and trapped particles out of the respiratory tract. it lines the respiratory tract. It starts from the nose and ends at the large bronchiole. 221- notes The respiratory epithelium covers all the conducting zone EXCEPT the Terminal Bronchiole Respiratory epithelium-Trachea Seromucous glands (G): mixed secretion Lamina propria hyaline cartilage presents in How can we distinguish the esophagus and trachea in a cross-section? In the respiratory system, dozen and in all respiratory the trachea stays open (patent) whether the person is alive or deceased. This is because the passages trachea is supported by cartilage rings, which prevent it from collapsing. In contrast, the esophagus is usually collapsed unless the person is swallowing. 221- notes: The tracheal wall consists of: Respiratory epithelium-Trachea ▪ Mucosa is lined with pseudostratified columnar ciliated epithelium with goblet cell Lamina Propria of the mucosa is present below the epithelium and there is no demarcation between it and the submucosa Unlike the GIT, there is no muscularis layer separating the lamina propria in the trachea. Students explanation(in simple way) The trachea has C-shaped rings made of hyaline cartilage. Under the epithelium in the trachea, we have the lamina propria: These rings keep the trachea open (patent) so air can pass easily. It provides support and nutrients to the epithelium. The rings are not complete at the back (posteriorly). Instead, the open part is replaced by the trachealis muscle and fibroelastic tissue. It contains Seromucous Glands (G) ( produce Why are the rings open at the back? serous secretion ”protein” and mucus secretion that go to the lumen of the The esophagus is located behind the trachea. trachea for immunity and protection) If the rings were complete, they would block or interfere with swallowing. which are present in bronchi also. The open part allows the esophagus to expand into the trachea when swallowing food The trachealis muscle is very important during the cough reflex: The adventitia is the outermost layer of the trachea. It contracts to make the trachea narrower. It means there is no peritoneal (mesothelium) because the This increases the speed of airflow, helping to expel mucus or any adherent trachea is not in the peritoneal cavity. particles stuck in the airways. Cells of respiratory epithelium There are 5 cells in the respiratory epithelium: (goblet cell, ciliated cell, basal cell, brush cell, and small granule cell) Two of them are considered major cells 1- Ciliated columnar cells: For sweeping the particles(toxins) in order to be swallowed or to be coughed. 2- Goblet cells:Mucus secretion to trap any foreign bodies. People with a immobile cilia syndrome will have recurrent infections due to impaired movement of cilia, leading to poor clearance of mucus and pathogens from the airways.” Ciliated Goblet cells columnar cells 221- notes: 1- Ciliated Cell: tall columnar cell, major cell. It’s the most common cell Cells of respiratory epithelium Ciliated cell consists of : Remember………5 types Cilia: movable tall projection with microtubules in the core that help in it is movement they are present at The apical border and have Basal bodies: the roots of small granule cell the cilia in the apical cytoplasm (Basel bodies structure looks like centrioles) Abundant mitochondria in the apical cytoplasm to provide energy for the movement of cilia. 2- Goblet Cell: columnar cell that has narrow basal part and broad apical part. Nucleus: present at the narrow basal part either oval or irregular. Function: Mucus secretion to trap any foreign bodies. Goblet cell consists of : Abundant Well developed Rough ER Well developed Golgi apparatus A lot of apical mucinogen granules that are released from the cell by exocytosis These granules are produced by rER and Golgi apparatus. 221- notes: Cells of respiratory epithelium 3- Brush Cell : columnar cell. 3% or less of the total Remember………5 types cells number. Apical border is covered with brush border “microvilli”. Basal border of this cell contact with nerve ending. Act as chemosensory receptor for sensation and small granule cell senses the chemical environment of the inspired air. Have a role in sneezing. 4- Small Granule Cell “ also called neuroendocrine cell or K cell “: columnar cell which is a part of diffuse neuroendocrine cells. Its cytoplasm is filled with small dense cored granules. It is an endocrine cell that produce hormones such as serotonin by exocytosis. 3% or less of the total cells number. 5- Basal Cell: short and it acts as stem cell. It differentiates and gives rise to different cells. Free Ribosomes are found in basal cell cytoplasm. Resulting in a Basophilic cytoplasm. ? goblet ciliated Small basal brush granule 221- notes: Bronchial tree: Bronchial tree and lung lobules ▪ Starts from the Trachea (in the neck) it is branched into right primary bronchi and left primary bronchi. ▪ When the Primary Bronchi enter the lung Pulmonary lobe from the hilum, they are branched into Bronchopulmonary secondary bronchi ”lobar segment bronchi”. Pulmonary ▪ Each secondary bronchus only supplies one lobule lung lobe “ the pulmonary lobes”. Number of secondary bronchi = Number of pulmonary lobes. (Right lung has 3 lobes.) (Left lung has 2 lobes “to give space to the heart) ▪ secondary bronchus branch into Tertiary Bronchi. ▪ Tertiary Bronchi and surrounding lung tissue form Bronchopulmonary segment. -Bronchopulmonary segment have surgical importance Each segment is functionally and anatomically discrete allowing a single segment to be surgically resected without affecting any healthy lung tissue. Bronchial tree and lung lobules 221- notes: Continue Bronchial tree: ▪ Tertiary bronchi is branched into smaller bronchi then bronchioles. Pulmonary lobe Note: bronchiole is the last station of the Bronchopulmonary respiratory epithelium. segment ▪ The bronchiole and the surrounding lung tissue Pulmonary forms the pulmonary lobule (triangle or lobule pyramidally in shape with a base toward the pleura and apex toward the hilum) Note: Lobule are not apparent after birth only in fetal life. ▪ bronchiole branch into terminal bronchiole. (no alveoli, the end of the conducting zone) ▪ terminal bronchiole branch into respiratory bronchioles that branch into alveolar duct. ▪ the alveolar ducts lead to the alveolar sacs, which have alveolus(The functional unit ) in clusters. ? Bronchial tree 1ry bronchi Alveolar duct alveoli 2ry Respiratory bronchi bronchiole 3ry bronchi bronchiole Alveolar sac Terminal bronchiole Bronchial tree -Bronchi The smooth muscle is what causes the folds in bronchus the bronchi and is not trachea found in the trachea. 1.Epithelium: respiratory epith(goblet cells ). 2.Lamina propria: Glands -elastic -smooth muscle -MALT Explanation in the next slide ⬇️ 3.Cartilage: plates 221- notes: The difference between bronchus and trachea: Bronchial tree -Bronchi The epithelium: 1.Epithelium: still present but as the bronchus brunch further into the lung the number of goblet cells decreases. respiratory epith(goblet cells ). Note: goblet cell decrease in number inside the lungs because its presence can cause accumulation of secretion 2.Lamina propria: which will cause infection because it help the growth of bacteria and microbes. Glands -elastic -smooth muscle -MALT Lamina propria and underlying submucosa: 1. Seromucous Glands: decrease to avoid abnormal 3.Cartilage: plates accumulation of secretion that cause infection and obstructions. 2. Elastic fibers: increase it is important to enhance the 4. MALT: increases because the function of the lung because it cause expansion of lung cilia decrease so MALT is needed (alveoli).”Adapt breathing” to provide protection inside the lungs. 3. Smooth muscle: in trachea there is smooth muscles only in Trachealis while in bronchus the smooth muscles cartilage: appears under the epithelium in Lamina propria and Bronchi have cartilage in the form of increase as you move down from the bronchus, they plates (help to keep it patent). provide support and maintain the wall patent and The folds of the bronchial mucosa is due to the presence of the smooth muscle. Note: Bronchiole have the most prominent smooth muscle. Bronchial tree -Bronchi The Smooth muscle in bronchus appear Crisscross. Crisscross smooth muscle Which factor keeps the bronchi patent? The cartilage keeps it open, and the bronchus smooth muscle plays a major role >> people with asthma, the smooth muscle causes bronchospasm 1.Epithelium: respiratory epith(goblet cells ). 2.Lamina propria: Glands -elastic -smooth muscle -MALT 3.Cartilage: plates Epithelium: - large Bronchial: at the beginning lined by normal respiratory epithelium Pspseudostratified columnar epithelium when it narrows the epithelium become simple columnar (main type) - Terminal: 1. start as simple columnar as it narrows it become simple cuboidal (main type) ‫ الدكتورة نبهت إذا جابت سؤال بالاختبار‬:Note )major( ‫تقولك شنو النوع تكتب النوع الأساسي‬ has also 5 types of cells but there are no goblet cells. Instead, it has clara cells also called “club or bronchiolar cells” , which are(cuboidal) apically dome-shaped and has cytoplasm filled with granules which secrete surfactant + smooth endoplasmic reticulum Clara cell functions 1. Secrete surfactant: A lipoprotein and phospholipid substance to keep the bronchioles patent (open) by reducing surface tension. 2. Detoxification: Metabolise and detoxify xenobiotics (hramful substance). 3. Secrete cytokines and immune components: The thickest portion of Contribute to antimicrobial action and support immune smooth muscle in the defense in the respiratory tract. bronchiole surfactant ‫مثال خارجي لتوضيح فكرة‬ Note: Clara cells secrete substances that Surfactant works like having a high-quality balloon. A cheap balloon is hard to blow up because it resists stretching. are more liquid-like compared to the A good balloon is easier because it stretches smoothly. thicker secretions of goblet cells. Q1) Which of the following lined by simple cuboidal ciliated epithelium ? A. Alveoli B. Terminal bronchiole C. Trachea Q2)in which one of the following structures gas exchanges does not take place A. alveolar sac B. respiratory bronchiole C. terminal bronchiole D. alveolar duct team Wishes you the best 1-B 2-C Q3) Which of the following cells in the respiratory epithelium has a chemosensory function? A. Goblet cells B. Brush cells C. Basal cells D. Small granule cell Q4)Which of the following is absent in the bronchioles? A. Smooth muscle B. Cartilage C. Elastic fibers D. Ciliated cells team Wishes you the best 1-B 2-B team Wishes you the best

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