HIST AA Resp Lecture 2024.pdf

Form and Function141: HISTOLOGY Respiratory system Airways Dr Mandi Alblas...

Form and Function141: HISTOLOGY Respiratory system Airways Dr Mandi Alblas [email protected] Medicine and Health Sciences | EyeNzululwazi ngezoNyango neMpilo | Geneeskunde en Gesondheidswetenskappe  4 Primary tissues All tissues consist of cells & extracellular matrix (ECM) A. Epithelial tissue B. Connective tissue D. Muscle tissue D. Nerve tissue  Outcomes: Airways 1. Describe the general building plan (basic tissue components) of a respiratory airway with a bronchus as example. 2. List the basic components of the conducting and respiratory portions of the system and describe distinctive structural features of each component related to particular functions in respiration. 3. Identify the trachea, bronchi, terminal bronchioles, respiratory bronchioles, alveolar ducts and alveoli of respiratory tract on the basis of: a. epithelial cell types present, and b. relative amounts of glands, cartilage, smooth muscles & connective tissue fibres present in the wall of tubes 4. Name the cellular and structural elements that form the blood-air barrier. 5. Identify the histological difference between an active and inactive breast 6. Annotate simple sketches (see class notes) and understand the photomicrographs of bone Material which is made available by way of an electronic database may be subject to certain licensing conditions. These conditions normally entail that you may only use the material for your own private study and research at the University and not for any other purpose. It is expected of you to adhere to these conditions at all times. Printed material is also only made available for class discussion, private study and research purposes. Further reproduction of such material is prohibited  Structure of respiratory tract 2 structural groups 1. Extrapulmonary 2. Intrapulmonary airways airways 1. Tertiary bronchus 2. 6. (segmental) 1. Nasal cavity 3. 7. Bronchiole 2. Pharynx 4. 8. Respiratory bronchiole 3. Larynx 5. 9. Alveolar duct 4. Trachea 6. 7. 10 Alveolar sac 5. Bronchi 7. 8. Main (primary) 9. https://doi.org/10.15347/wjm/2014.010 Lobar (secondary) 10. https://opentextbc.ca/anatomyandphysiology/chapter/22-1- organs-and-structures-of-the-respiratory-system/  Functions of respiratory tracts 2 functional groups 1. Conducting 2. Respiratory airways airways 1. 1. Nasal cavity 6. Respiratory bronchiole 2. 7. 2. Upper airways Alveolar duct 3. 3. Extrapulmonary airways 8. Alveolar sac 4. 4. Intrapulmonary airways Function: 6. 5. 5. where gas exchange takes Terminal place (contributes to bronchioles homeostasis by exchanging 7. Function: O2 & CO2 between https://doi.org/10.15347/wjm/2014.010 Conducts (transports) air from outside to deeper parts of atmosphere & blood). lungs. Air is cleaned, moistened, & warmed in these airways.. https://opentextbc.ca/anatomyandphysiology/chapter/22-1- 8. organs-and-structures-of-the-respiratory-system/ ©SUN. For educational purposes only  Pathway of air through airways 1. Nasal cavity Here inhaled air is “cleaned” by 1. Extrapulmonary airways removal of particulate matter, 2. Pharynx warmed and moistened. respiratory 3. Larynx 1. 2. system Upper 4. Trachea 3. 5. Bronchi 4. respiratory 6. Tertiary bronchus (segmental) 2. Intrapulmonary airways system Lower 5. 7. Bronchiole 6. 7. 8. Respiratory bronchiole 8. 9. Alveolar duct 10 9. Here gas exchange 10 Alveolar sac take place  General building plan of a typical airway Mucosa F: (epithelium) removes mucus secretion (cilia) i. Respiratory and keeps airways clean (filtering out foreign material epithelium (viruses/bacteria) in trachea & bronchi to not reach alveoli) i. Lamina propria ii. F: (connective tissue) ‘glue’ that attaches ii. epithelium to muscle layer. Have rich plexus of thin-walled veins (venous sinuses) iii. Muscularis Gland duct mucosa iii. F: (smooth muscle) muscle contraction (is not always present) iv. gland Submucosa iv. F: (dense connective tissue). Not always present. May have glands which produce mucus v. F: (connective tissue). Not always present. Keep Hyaline airway open when negative pressure is v. cartilage introduced during inspiration Adventitia vi. F: (connective tissue). Deepest layer, ‘glue’ to vi. *F: Function outside organs  Covering epithelium Large part of resp syst. is lined with RESPIRATORY EPITHELIUM  Covering epithelium: Respiratory epithelium Also known as: Pseudostratified ciliated cylindrical epithelium with goblet cells Pseudo = look stratified (nuclei form 2 rows), BUT all touch basal membrane ciliated cylindrical cell intermediate cell basal cell basal lamina goblet cell endocrine cell  Respiratory epithelium consists of: 1. Ciliated cylindrical epithelial cells F: cilia = transport (remove) mucus secretion & keep airways clean F: epithelium = secrete watery saline for humidity 2. Basal cells on b.m. but not in contact with lumen F: stem cells (reserve cells) - undergo mitosis to replace other cell types (replace dead/damaged cells). 3. Intermediate cells: basal cells - differentiating to form cylindrical cell/ goblet cells. 4. Goblet cells in epithelium – secrete mucus: F: keeps epithelium moist F: moisturises inspired air F: traps inspired particles (dust, bacteria, pathogens, etc) 5. Endocrine cells in trachea and bronchi: neuroendocrine cells (Kulchitsky cells) F: secrete various hormones & bioactive substances (e.g. serotonin) play role in regulating airway function/immune responses/local control of blood flow.  Submucosa consists of: 1. Connective tissue layer Layer for nerve, blood- & lymph vessels Holding place for glands 2. Glands in connective tissue secrete mucus/serous: keeps airway surfaces moist moisturises inspired air traps inspired particles (dust, bacteria, etc) 3. Venous sinuses in CT warm air to body temperature Warming air to prevent changes in core body temperature-body heat Adding water vapour to 100% humidity, preventing drying out of moist exchange epithelium (water evaporating from airway mucosal lining) - 100% humidity and 37°C by time reaches trachea  Airways structural changes 1. Nasal cavity 1. Extrapulmonary airways 2. Pharynx 3. Larynx 4. Trachea 5. Bronchi 6. Tertiary bronchus (segmental) 2. Intrapulmonary airways 7. Bronchiole 8. Respiratory bronchiole 9. Alveolar duct 10 Alveolar sac  Airways structural changes Anterior nasal cavity Skin with short hairs/vibrissae = stratified squamous epithelium. Filter – picks up dust particles Rest of the nasal cavity (nasal mucosa) Nasal cavities and sinuses are covered by respiratory epithelium Roof of nasal cavity Olfactory epithelium: Pseudostratified columnar epithelium (olfactory cells between epithelial cells). Modified neurons for identifying scents  Airways structural changes cont Nasopharynx Lined by respiratory epithelium =have patches of squamous epithelium occur with increasing age =lamina propria contains serous & mucous glands & large masses of lymphoid tissue (prominent in children and young adults) Oropharynx Lined by unkeratinized stratified squamous epithelium Larynx Lined by respiratory epithelium https://thancguide.org/cancer-types/throat/pharyngeal/nasopharyngeal/anatomy/  Nasal mucosa Mucosa (Ep) Respiratory epithelium (L) Lamina propria (SM) Submucosa (with glands) (A) Adventitia  Trachea Mucosa (Ep) Respiratory epithelium Muscle layer only posterior (L) Lamina propria oesophagus Gland acini Trachealis (SM) Submucosa muscle (with glands) Ep perichondrium L (C) Hyaline cartilage SM (A) Adventitia C A  Posterior Mudfix? What is this structure? lumen What is this structure? lumen Anterior  Bronchus Mucosa (Ep) Respiratory epithelium (L) Lamina propria Muscle layer surrounding (Mm) Muscularis Gland acini mucosa Ep (SM) Submucosa (with glands) perichondrium L (C) Hyaline cartilage Mm SM (A) Adventitia C A  Mudfix? Histological structure of primary & secondary bronchi are same as trachea (except for muscularis mucosa) Trachea branches into 2 main bronchi (1 in each lung) Branches in 2 again – secondary bronchi Branches in 2 again - tertiary etc. Dichotomous branching = into 2 Total diameter of each 2 branches is larger than original airway diameter How will this type of branching influence the flow of air? Slow it down Airway diameters become progressively smaller, Silverthorn, CH17, p573 but parallel increase in number of airways & cross-sectional area  Airways structural changes 1. Nasal cavity 1. Extrapulmonary airways 2. Pharynx 3. Larynx 4. Trachea 5. Bronchi 6. Tertiary bronchus (segmental) 2. Intrapulmonary airways 7. Bronchiole 8. Respiratory bronchiole 9. Alveolar duct 10 Alveolar sac  Intrapulmonary airways NOT lined by respiratory epithelium trachea Smaller airways: Simple epithelium (cuboidal to squamous), no basal cells; different airways have different epithelia. a. tertiary (segmental) bronchi Conducting b. smaller bronchi portion c. Bronchioles (large to small) d. terminal bronchioles smallest conducting airways - less than 0.5mm diameter e. respiratory bronchiole Respiratory f. alveolar ducts portion g. alveolar sacs  (smaller) Bronchus Mucosa (Ep) Respiratory epithelium (L) Lamina propria Mm = Muscle layer surrounding (Mm) Muscularis Gland acini mucosa Ep (SM) Submucosa (glands become less) perichondrium L (C) Hyaline cartilage Mm (plates become less) SM (A) Adventitia C A  Mudfix c.s of trachea c.s of large intrapulmonary c.s of small bronchus intrapulmonary bronchus Ep Ep trachealis A SM E L C Mm L L E C Gl Mm Mm L E C SM Gl SM L SM C C A Mm A A A As bronchi branch & become smaller, cartilage and glands are reduced. BALT disappears. Epithelium becomes lower & goblet cells fewer.  Bronchiole Clara cell Mucosa (Ep) Respiratory epithelium (L) Lamina propria Muscle layer surrounding (Mm) Muscularis mucosa Ep (A) Adventitia L Branching smaller=