Respiratory System Medicine Update PDF

Respiratory System S. THEMISTOCLEOUS, MSc. BSc Medicine Program Medical School Anatomical Division Functions of the Respiratory System Conduct & Filtrate Air Gas Exchange/ Respiratory portion Production of Sound Olfactory System Re...

Respiratory System S. THEMISTOCLEOUS, MSc. BSc Medicine Program Medical School Anatomical Division Functions of the Respiratory System Conduct & Filtrate Air Gas Exchange/ Respiratory portion Production of Sound Olfactory System Respiratory Epithelium- Structure Respiratory epithelium of most of the surfaces of the Nasal cavities and conducting portion of the respiratory system are lined with a ciliated pseudostratified columnar epithelium. 5 major cell types: 1. 250-300 Cilia on the surface of columnar epithelium 2. Goblet cells (basal nucleus and mucin producing granules in apical end) 3. Brush cells (microvilli)- short, blunt microvilli on their apical surface, giving them a "brush-like" appearance under a microscope. These are chemosensory cells, triggering protective reflexes, such as coughing or sneezing. 4. Kulchitsky cells- part of the diffuse neuroendocrine system 5. Basal cells – progenitor cells that give rise to other epithelial cells types  Respiratory Epithelium- Structure Brush cells Columnar cells with microvilli on apical side. A synaptic connection with a nerve ending-receptor Basal Cells Stem cells/progenitor cells Kulchitsky cells Part of diffuse neuroendocrine system 5  Nasal Cavity Nares (nostrils) of nose and vestibule present keratinized stratified squamous epithelium sweat glands sebaceous glands vibrissae (hairs) Nasal Cavity  Nasal Cavity Pseudostratified columnar epithelium R DOI: 10.1126/sciadv.abc5801 Respiratory Epithelium- Function Air Filtration: The nasal cavity is lined with tiny hairs (cilia) and mucus, which trap dust, pollen, and other particles, filtering the air before it enters the lungs Humidification: The mucous membrane within the nasal cavity secretes mucus and provides moisture, humidifying the incoming air to prevent dryness in the respiratory tract. Nasal Cavity: Olfactory Epithelium Olfactory Epithelium - Function Olfaction (Smell): The nasal cavity contains the olfactory epithelium, a specialized tissue with sensory receptors that detect odor molecules, transmitting signals to the brain for smell recognition. 1. Odor come in contact with olfactory receptors located in the roof of the nasal cavity 2. Binding of odor to O.R triggers a biochemical signal in the olfactory neuron 3. An electrical signal is generated that travels to the olfactory bulb where they are processed and analyzed 4. Signal from bulb to brain, olfactory cortex and limbic system in particular 5. The brain interprets the signal and generates the perception of smell  The lamina propria of the olfactory epithelium possesses large serous glands, the olfactory glands (of Bowman), which produce a constant flow of fluid surrounding the olfactory cilia and facilitate the access of new odoriferous substances. Olfactory Neurons Olfactory Neurons  Serous Glands Bowman’s Gland Olfactory Nerves Bowman’s glands Goblet cells Tubuloaveolar shape Synthesize and secrete mucus Secrete a serous fluid (proteins such as create a protective mucus layer lactoferrin, lysozyme, amylase and IgA) Gel-forming mucin protein Involved in immunoregulation Act as odorant transporters, Paranasal Sinuses Fewer goblet cells Lined by thinner respiratory epithelium (pseudostratified columnar ciliated) Mucus produced here is moved into the nasal passages by ciliated epithelial cells 19  Two Functional Sections Conducting Portion- passages where air is conditioned before reaching the lungs (nasopharynx, larynx, trachea, paired bronchi and finally bronchioles) Respiratory Portion- anatomical structures where gas exchange occurs ( respiratory bronchioles, alveolar ducts, alveoli)  Respiratory Epithelium The respiratory tract mucosa is characterised by a Pseudostratified Columnar Ciliated epithelium Carrying 5 main cell types: 1. Goblet cells 2. Ciliated cells (motile) 3. Brush cells 4. Kulchitsky cells (small granule cells) 5. Basal cells https://doi.org/10.3390/ijms21238907 Respiratory Epithelium Lamina Propria Thin layer of connective tissue found beneath the epithelial lining. It is composed of a rich, vascular network involved in warming inhaled air. Also contain sero-mucus glands Basement membrane Thin lining of tissue which separates any surface form the connective tissue which underlines it 22  Mucosa-Associated Lymphoid Tissue Mucosa associated lymphoid tissue- small concentrations of lymphoid tissue found in the submucosa layer and contain multiple immune protective cells. They are located in such a way so as to encounter antigens passing through the mucosal epithelium.  Ciliated Columnar Epithelium ❑ Cover most of the respiratory epithelium ❑ Short, hair-like proctiles on apical surface ❑ Act as a mucociliary escalator moving mucus in an opposite direction to the incoming flow of air ❑ Help wash-out microbes, pathogens etc from entering the lungs 26  Mucus Cells ❑ Same as goblet cells in the intestines ❑ Interspersed along epithelium ❑ Merocrine secretion (apocrine under stress) ❑ Granules of mucin at apical side ❑ Basal nuclei 27 Lamina Propria of Respiratory Mucosa Complex vasculature crucial in conditioning inhaled air Humidifies air by secreting water from seromucous glands  Pharynx Nasopharynx Respiratory type epithelium Oropharynx Stratified squamous non- keratinised epithelium Laryngopharynx Stratified squamous non- keratinised epithelium 29  Epiglottis ❑ Passageway between oropharynx and trachea (Larynx) ❑ Hyaline and elastic cartilage ❑ Movement by skeletal muscle allows these cartilages to be involved in sound production ❑ Epiglottis projects from the larynx which serves to prevent food or fluid from entering the trachea ❑ The epiglottis transitions from Stratified squamous epithelium →Ciliated pseudostratified epithelium  Lingual Epithelial Non-keratinized stratified Surface squamous epithelium Seromucous glands Laryngeal Elastic Cartilage Epithelial Surface Ciliated pseudostratified columnar http://www.histologyguide.com/slideview/MH-038-039-epiglottis/17-slide-1.html?x=21098&y=25400&z=2.5&page=1 Stratified squamous non-keratinised Pseudostratified Columnar Ciliated  False Cord Vocal cords False Vocal Cords It is an immovable lined with a respiratory epithelium and a lamina propria containing seromucous glands & lymphoid nodules Vocal Ventricle True Vocal Cords Movable party of the vocal cords with non-keratinised stratified squamous epithelium. The lamina propria contains vocal ligaments and seromucous glands True The entire vocalis muscle→ skeletal Vocal Cord muscle 35  Trachea ❑ Short ❑ Flexible ❑ Extends from larynx to about the middle of the thorax →bronchi ❑ Supported by cartilaginous rings ❑ The wall of this organ consists of I. Mucosa II. Submucosa III. Cartilaginous layer IV. Adventitia I. Mucosa lined with pseudostratified ciliated columnar epithelium with goblet cells II. Lamina Propria Elastic fibers and immune cells III. Submucosa seromucous glands that help produce mucus to humidify and trap foreign particles from the air. The is also cartilage and the trachealis muscle IV. Adventitia connective tissue that binds the trachea to surrounding structures.  Trachea Respiratory epithelium Lamina Propria: o Sero-mucous glands Cartilage: o Hyaline cartilage o C-shaped ring Where the cartilage opening lays → smooth muscle it found along with fibroelastic tissue Respiratory Secrete serum and mucus on surface of epithelia to add epithelium moisture to air & help trap contaminants respectively Hyaline Cartilage Trachealis Muscle  Bronchial Tree 1. Primary bronchi Right bronchus is wider and significantly shorter than the left 2. Once inside lung hilum→Secondary bronchi Tertiary Bronchi 3. Bronchi terminate where bronchioles begin 4. Each bronchiole branches into 5-7 bronchioles  Bronchi Pseudostratified columnar ciliated epithelium Identifiable by its distinct lamina propria: ❑ Circular layer of smooth muscle ❑ Mucosal glands ❑ Cartilage plates/islands ❑ MALT tissue As we move deeper towards the alveoli the cartilage plates become smaller…. 42  Respiratory Bronchiole Simple columnar ciliated or simple cuboidal epithelium Lamina propria ❑ No cartilage ❑ No mucosal glands ❑ Some smooth muscle Acinii ciliated Terminal Bronchioles Last stage of conduction Epithelium ❑ simple cuboidal Lamina Propria ❑ Smooth muscle ❑ Elastic fibers Autonomous nervous system 45  Apart from the standard respiratory cells ….. Club cells or bronchiolar exocrine cells: ❑ Non-ciliated, have microvilli ❑ No mucous ❑ Dome-shaped Secrete Surfactants Secrete mucin Repair after injury Anti-inflammatory Synthesize and secrete antimicrobial peptides, such as lysozyme, and cytokines Engulf & detoxify proteins Alveoli  Alveoli Surrounded by a dense network of capillaries Where gas exchange occurs Macrophages Two types of pneumocyte cells ❑ Type I ❑ Type II  Alveoli Type I Pneymocytes Type II Pneymocytes ❑ Dome-shaped ❑ 95% of alveolar lining ❑ Cuboidal cells ❑ Simple squamous ❑ Contains secretory granules ❑ Thin (lamellar bodies) that ❑ Gas-exchange point secrete surfactant- ❑ Desmosomes & other exocytosis occluding junctions prevent ❑ Act as stem cells (of TYPE I leakage into air space & TYPE II ❑ Part of blood-brain barrier ❑ Usually give way for pores of Kohn 49 Blood Circulation within the lungs Bronchial arteries—travel parallel to the airways and supply oxygenated blood. They are the source of nutrition of the bronchioles and lungs Pulmonary arteries - travel parallel to airways and supply deoxygenated blood Pulmonary veins drain oxygenated blood 51  Diaphragm ❑ Internal skeletal muscle ❑ Separates thoracic region from abdominal ❑ Controls volume of the cavity→ aid in air being drawn into lungs Pleura ❑ Membranous cavity ❑ Folds back on itself forming a two-layer membrane Are these the same? 53 Microphages/Dust cells