Respiratory II Histology and Development PDF

Respiratory II: Histology and Development Course Objectives Respiratory- Describe how gas is exchanged in the body by examining and identifying gross and microscopic anatomical structures in the respiratory system.  Lecture...

Respiratory II: Histology and Development Course Objectives Respiratory- Describe how gas is exchanged in the body by examining and identifying gross and microscopic anatomical structures in the respiratory system.  Lecture Learning Objectives 1. Recognize and describe respiratory 5. Explain how the left and right epithelium and the functional lungs differ during development significance of its structural features (recall their adult anatomical (e.g., nasal concha, epithelial type) organization) 2. Visually identify olfactory epithelium 6. Associate major events in the 3. Visually identify the trachea (and its development of the respiratory components) and parts of the system with weeks/periods bronchial tree, including bronchi, bronchioles, respiratory bronchioles, 7. List the requirements for normal alveolar duct, and alveoli lung development and explain 4. Describe the development for each fetal breathing segment of the lower respiratory 8. Describe tracheoesophageal system; be familiar with the structure fistulas including its anatomical terminology and location, tissue origins, and sequence of events cause, associated terminology, and symptoms  Respiratory System Organization Conducting portion Nasal cavity Larynx Trachea Bronchi Bronchioles Respiratory portion Lower respiratory Respiratory bronchioles tract Alveolar duct/sac Alveoli  Identifying Characteristics Conducting portion Nasal cavity Larynx Trachea What type of epithelium? Bronchi Is cartilage present? Is cartilage Bronchioles continuous? Respiratory portion Respiratory bronchioles Alveolar duct/sac Alveoli Upper Respiratory Tract Histology  LO 1 and 2 Nasal Cavity Structured to condition and filter air Nasal concha Increase rotational movement of air to warm and moisten Respiratory Epithelium Respiratory epithelium Pseudostratified ciliated columnar epithelium- filter air Goblet cells- mucin producing- moisture Overlies highly vascularized lamina propria – warmth Olfactory epithelium- special senses  LO 1 and 2 Nasal Cavity- Coronal section of guinea pig fetus 1. Nasal concha Olfactory epithelium Respiratory Epithelium 1 Nasal cavity 1 Tongue Mandible  LO 1 Nasal Cavity Respiratory Epithelium Pseudostratified ciliated columnar epithelium  LO 1 Nasal Cavity Olfactory epithelium  Trachea Conduction only Lined with respiratory mucosa Pseudostratified ciliated columnar epithelium Numerous goblet cells Numerous seromucous glands watery mucous producing glands in lamina propria C-shaped hyaline cartilaginous rings provide flexible structure  LO 3 Trachea A. Hyaline cartilage Note the continuous ring Seromucous glands A Lumen Lumen  LO 3 Pseudostratified ciliated Trachea columnar epithelium Goblet cells Lumen Lumen  LO 3 Bronchial Tree Histology Defining Characteristics Epithelium Cartilage Other Bronchi Pseudostratified ciliated columnar Hyaline, not Muscularis mucosa present epi. continuous deep to hyaline cartilage Continuous Goblet cells Bronchiole Simple ciliated columnar (ciliated None (most of the and non-ciliated simple columnar), time) to simple cuboidal Continuous walls Respiratory bronchiole Simple cuboidal None Not continuous- open to alveoli and alveolar ducts Alveolar duct Simple squamous None Not continuous- walls open to alveoli Alveoli Type I (simple squamous) and II None alveolar cells  1. Hyaline cartilage LO 3 Bronchi Note the segmented organization 2. Pseudostratified ciliated columnar epithelium 3. Muscularis mucosae Not found in trachea Lumen 3 2 1 3 1 3 Lumen 1 1  LO 3 Lumen Bronchi Lumen Pseudostratified ciliated columnar epithelium Goblet cells Lower Respiratory Tract Histology  LO 3 Bronchiole A. Bronchiole No cartilage, thick epithelia Continuous wall A B. Respiratory bronchiole No cartilage, thinner epithelia Has openings to aveoli in wall. Why? B  LO 3 Bronchiole A. Bronchiole B. Respiratory bronchiole A B No openings in wall, thick epithelium, but hyaline cartilage. What structure?  LO 3 Conducting to E Respiratory Transition A. Bronchiole B. Respiratory bronchiole E B C C. Alveolar duct D. Alveolar sac A A E. Alveoli D E B A B C E D  LO 3 Respiratory Portion 1. Respiratory bronchiole Note the openings in the wall but thicker epithelium 1 2. Alveolar duct Open spaces within thin walls 3. Alveolar sac 4 4 2 4. Alveolus 3 Border may be continuous or open 3 1 2 2 1 4 4 4 1 2 3  LO 3 Respiratory Portion 2 3 1. Respiratory bronchiole Note the openings in the wall but thicker epithelium 2. Alveolar duct 1 Open spaces with thin 4 4 walls 4 3. Alveolar sac 1 1 4. Alveolus Border may be continuous 4 or open Respiratory Embryology  LO 4 Respiratory Embryology The respiratory system begins to develop between weeks 3 and 4 from the 4th and 6th pharyngeal arches of foregut Foregut endoderm- forms epithelial lining and glands of lower respiratory tract Foregut mesoderm- forms connective tissue, cartilage, lamina propria, and smooth muscle Laryngotracheal groove- groove that appears on ventral wall of foregut adjacent to 4th and Anterior view of foregut with 6th pharyngeal arches (5th arch regresses laryngotracheal diverticulum shortly after forming) developing Outpouching occurs, becomes the laryngotracheal diverticulum Proximal portion- larynx Middle portion- trachea Distal portion- lungs Formation and growth of laryngotracheal diverticulum from anterior foregut; Moore et al., 2020, Before We are Born  LO 4 Larynx Proximal portion of laryngotracheal diverticulum becomes larynx; laryngeal inlet is former laryngotracheal groove Swellings in arches 4 and 6 at entrance of laryngotracheal diverticulum become epiglottis (superior swelling) and other cartilage of larynx (inferior swelling) Folds of mucous membrane (epithelium) in diverticulum become vocal and vestibular folds, form laryngeal ventricles Laryngeal muscles will develop from myoblasts from 4th and 6th pharyngeal arches Posterior section, view of anterior pharyngeal arches/gut tube; Moore et al., 2020, Before We are Born First Aid: Organ Systems  LO 4 and 5 Trachea, Bronchi, and Bronchioles Middle portion of laryngotracheal diverticulum becomes trachea Respiratory buds will develop at caudal end, divide into two primary bronchial bud outpouchings Buds are asymmetrical, with left bud smaller and more laterally oriented, reflecting adult anatomy Bronchial buds, with surrounding mesoderm, will branch and differentiate into primary, secondary, and tertiary bronchi Development of trachea and lungs; Moore et al., 2020, Before We are Born  LO 4 Pleura As lungs grow, they penetrate the intraembryonic coelom, or body cavity All pleura is derived from lateral plate mesoderm Visceral pleura is derived from splanchnic mesoderm Parietal pleura is derived from somatic mesoderm https://www.youtube.com/watch?v=wq8PMQyHNas  LO 4 Pleura As lungs grow, they penetrate the intraembryonic coelom, or body cavity All pleura is derived from lateral plate mesoderm Visceral pleura is derived from splanchnic mesoderm Parietal pleura is derived from somatic mesoderm 3rd Week of Development Development of trachea and lungs; Moore et al., 2020, Before We are Born  Lungs LO 6 Relatively late to mature Bronchi and bronchial tree form between 2-7 months gestation Pseudoglandular period (wk 5*-16) All portions of bronchi and bronchial tree are formed EXCEPT respiratory bronchioles and alveoli (i.e., the respiratory portion) Canalicular period (wk 16-26) Airways increase in diameter and vasculature develops Primitive versions of respiratory portion develop * Begins at week 6 in pre-class activity video  LO 6 Lungs Portions necessary for survival outside the uterus do not begin form until week 26+ Saccular Period (Wk 26/4- birth) Terminal sacs develop with Type I cells (simple squamous epi) and Type II cells (surfactant production) Alveolar (Prenatal*- Childhood) “Breathing” of amniotic fluid occurs in utero Alveoli mature from 0- 3 years; alveoli increase in number 3-8 years *Begins at week 32 in pre-class activity video  LO 7 Respiratory Embryology Requirements for normal lung development A. Adequate thoracic space B. Adequate amniotic fluid volume C. Fetal breathing movements Fetal breathing movement occurs in utero Stimulate lung development Fetal lungs are ½ filled with fluid from amnion and pulmonary glands At birth, fluid leaves though nose and mouth and into pulmonary arteries, veins, or lymphatic vessels Development of trachea and lungs; Moore et al., 2020, Before We are Born  LO 8 Clinical Relevance- The four main varieties of tracheoesophageal fistula (TEF) are shown Tracheoesophageal Fistula to the left. Directions of content flow are indicated by arrows. A) Esophageal atresia (TEF) (~85% of cases). B) Tracheoesophageal fistula (4% of cases) C, Atresia of the Fistula = abnormal communication between proximal esophagus with tracheoesophageal body cavities; Atresia = absence or abnormal fistula, distal esophagus having a blind narrowing of opening pouch. D) Atresia of the proximal esophagus TEF = Abnormal passage between trachea and with fistulas between the trachea and esophagus proximal and distal segments of the esophagus. Occurs in 1/3000 to 1/4500 live births and predominately affects males Most commonly associated with esophageal Tracheoesophageal atresia fistula in a 17 week fetus. Esophageal Due to incomplete division of cranial part of segment ends blindly foregut into respiratory and esophageal parts in (arrow) 4th week Symptoms: chocking, coughing, regurgitation, reflux; may result in pneumonia or pneumonitis (inflammation of the lungs) Moore et al., 2020, Before We are Born