Lecture 5 (1) PDF - Pleura

Pleura  ILOS Enumerate parts of the pleura and its recesses. Outline the surface anatomy of pleurae. Mention the blood and nerve supply and lymphatic drainage of pleura.  Pleura Definition: a serous membrane invaginated from its medial side by the lung Parts...

Pleura  ILOS Enumerate parts of the pleura and its recesses. Outline the surface anatomy of pleurae. Mention the blood and nerve supply and lymphatic drainage of pleura.  Pleura Definition: a serous membrane invaginated from its medial side by the lung Parts of parietal pleura 1- Cervical pleura: covers the apex of the lung. 2- Costal pleura: lines thoracic wall. 3- Mediastinal pleura: lines mediastinum. 4- Diaphragmatic pleura: lines diaphragm  Pleural recesses - Definition: Narrow extensions of the pleural cavity. - Function: Allows the lungs to expand during deep inspiration. - Parts: 1- Costomediastinal 2- Costodiaphragmatic 1. Costomediastinal recess: - lies between costal and mediastinal pleura. - filled with the anterior border of the lung in deep inspiration. 2. Costodiaphragmatic recess: - lies between costal and diaphragmatic pleura. - filled with the inferior border of the lung in deep inspiration. - It is the most dependent part of pleura. If fluid appears in pleural cavity, it collects in this recess.  Blood supply, nerve supply and lymphatic drainage Parietal pleura Visceral pleura Blood supply Intercostal vessels, Bronchial vessels internal thoracic, musculophrenic vessels. Nerve supply Somatic Autonomic. Intercostal nerves: for costal pleura and peripheral diaphragmatic. Phrenic nerves: for mediastinal pleura and central diaphragmatic. (So it is sensitive to pain). Lymph Parasternal, intercostal and diaphragmatic lymph Bronchopulmonary lymph drainage nodes. nodes. Blood supply and lymphatic drainage of parietal pleura Nerve supply of pleura Clinical importance: - Pleural Pain and radiation: ❖The lower part of the costal parietal pleura receives its sensory innervation from the lower five intercostal nerves, which also innervate the skin of the anterior abdominal wall, pleurisy (inflammation of pleura) in this area commonly produces pain that is referred to the abdomen. Clinical importance: ❖Pleurisy of the central part of the diaphragmatic pleura, which receives sensory innervation from the phrenic nerve (C3, 4, and 5), can lead to referred pain over the shoulder because the skin of this region is supplied by the supraclavicular nerves (C3 and 4). Clinical importance: -The pleural cavity may be filled with: - Air: pneumothorax. - Fluid: hydrothorax (pleural effusion). - Blood: haemothorax. - Lymph: chylothorax. - Pus: pyothorax (empyema).  Aspiration of pleural fluid: - needle thoracostomy. - The preferred insertion site for a needle is the 2 spaces below the upper level of effusion. Needle inserted at the upper border of the rib to avoid: Injury of intercostal nerve and vessels in the subcostal groove. Surface anatomy of pleura Mechanism of respiration  Mechanism of respiration 1- Quiet inspiration: Increase of vertical diameter: due to contraction of diaphragm. Increase of transverse diameter: bucket handle mechanism: the ribs are raised in lateral direction during inspiration because the shafts are lower than two ends. Increase of anteroposterior diameter :Pump handle mechanism: anterior ends of the ribs are raised pushing the sternum forwards during inspiration because they are lower than the posterior ends. 2- Forced inspiration: contraction of accessory muscles (sternomastoid, scalecus anterior, serratus anterior and pectoral muscles). 3- Quiet expiration: by elastic recoil of the lungs & relaxation of intercostal muscles and diaphragm. 4- Forced expiration: by contraction of accessory muscles (latissimus dorsi, quadratus lumborum and anterior abdominal wall muscles). Development of respiratory system  ILOS Describe the development of the respiratory tract Enumerate the congenital anomalies of the respiratory tract ❑ Endodermal in origin. ❑ Arises from the floor of the pharynx. ❑ Begins at about week 4th of gestation.  laryngeotracheal groove: a longitudinal groove in the floor of the developing pharynx. The edges of this groove are fused to form laryngeotracheal tube The tube separated from the developing esophagus by development trachea-oseophageal septum. Larynx, trachea and lung develop from separated endodermal laryngotracheal tube.  Upper part of laryngotracheal tube forms the larynx and trachea. Lower end of laryngotracheal tube is divided into 2 lung buds, the right one divided into 3 parts giving rise to 10 bronchopulmonary segments but the left one is divided into 2 parts giving rise to 9-10 bronchopulmonary segments. The other coats develop from the adjacent splanchnic mesoderm.  Stages of lung maturation: 1.Pseudo-glandular stage: From the 1st to the 4th month of development. Only bronchi and terminal bronchioles are formed so, the lung resembles exocrine gland. 2. Canalicular stage: From the 4th to the 6th month. Each terminal bronchiole divides into 2 respiratory bronchioles, each of which divides into 4 alveolar ducts. Some terminal sacs (primitive alveoli) begin to develop. There is increased vascularity of the developing lung. 3.Terminal sac stage: From the 6th month till birth. Many more terminal sacs develop and capillaries begin to bulge into their walls.  The terminal sacs have two types of cells: 1.Type I pneumocytes: squamous epithelial cells that represent the main lining of the alveoli. 2.Type II pneumocytes: ✓scattered between type I pneumocytes. ✓secrete pulmonary surfactant, which forms a thin film over the internal wall of the alveoli that prevents their collapse after birth. Deficiency of surfactant leads to respiratory distress syndrome. 4.Alveolar stage: From birth to 8 years. Type I pneumocytes become very thin and with their adjacent capillaries form alveo-capillary membrane, which allows very efficient gas exchange.  Development of pleura - formed when each lung bud invaginated the ipslateral pericardio-peritoneal canal.  Congenital anomalies - Agenesis of the lung: failure of the primitive lung bud to develop. - Laryngeal web: failure of complete canalization of laryngeal cavity. - Congenital subglottic stenosis: due to defect canalization of cricoid cartilage.  Esophageal atresia with or without Tracheo- esophageal fistula (TEF): TEFs results from abnormal division of tracheoesophageal septum. Neonates come with vomiting and chocking after breast feeding. Respiratory distress syndrome: failure of the alveoli to ventilate adequately due to deficient production of the surfactant. - Congenital cysts of the lung: formed by dilation of terminal or larger bronchi. - Accessory lung lobe: Arising from the trachea or esophagus.