Pleura Anatomy and Functions

Study Notes

Pleura is a serous membrane, originating from the medial side of the lung.
Visceral and parietal pleura are continuous.
Parietal pleura lines the thoracic wall, mediastinum, and diaphragm.
Visceral pleura covers the lungs.
The pleural cavity is a potential space between the visceral and parietal pleura.
There are recesses in the pleural cavity called costomediastinal and costodiaphragmatic recesses.

Costomediastinal recess: Located between costal and mediastinal pleura. Filled with the anterior border of the lung during deep inspiration.
Costodiaphragmatic recess: Located between costal and diaphragmatic pleura. Filled with the inferior border of the lung during deep inspiration. It's the lowest part of the pleural cavity and fluid collects there if found in the cavity.

Parietal pleura:
- Blood supply: Intercostal vessels, internal thoracic, and musculophrenic vessels.
- Nerve supply: Somatic (intercostal nerves for costal pleura and peripheral diaphragmatic pleura, phrenic nerves for mediastinal and central diaphragmatic pleura)
- Lymphatic drainage: Parasternal, intercostal and diaphragmatic lymph nodes.
Visceral pleura:
- Blood supply: Bronchial vessels.
- Nerve supply: Autonomic (nerves of pulmonary plexus, vagus and sympathetic).
- Lymphatic drainage: Bronchopulmonary lymph nodes.

Needle thoracostomy is the procedure used to aspirate pleural fluid.
Preferred insertion site is two spaces below the upper level of effusion.
Upper border of the rib is the insertion site to avoid injury to intercostal nerves.

Landmarks like mid-clavicular line, mid-axillary line, and paravertebral muscles are mentioned within the reference image.

Quiet inspiration: Increased vertical, transverse, and anteroposterior diameters of the thorax due to diaphragm and rib muscle contractions.
Types of inspiration: Quiet and forced inspiration
Quiet expiration: Elastic recoil of lungs and the relaxation of the diaphragm and intercostal muscles.
Forced expiration: Contraction of accessory muscles

Origin: Endodermal tissue from the floor of the pharynx, beginning around week 4 of gestation.
Laryngeal groove forms, and the edges fuse to form the laryngotracheal tube.
The laryngotracheal tube separates from the developing esophagus during development.
Larynx, trachea, and lungs develop from separate endodermal tissue of the laryngotracheal tube.
During development, the lower end of the laryngotracheal tube divides into two lung buds (right and left). The right bud divides into three, and the left bud divides into two, which give rise to bronchopulmonary segments.
Other coats develop from the adjacent splanchnic mesoderm.

Pseudo-glandular (1st-4th month): Bronchi and terminal bronchioles form.
Canalicular (4th-6th month): Terminal bronchioles divide into respiratory bronchioles and alveolar ducts. Primitive alveoli develop.
Terminal sac (6th month-birth): Many more terminal sacs develop, and capillaries bulge into their walls.
Alveolar (birth-8 years): Type I pneumocytes become very thin and form the alveo-capillary membrane for efficient gas exchange.

Pleura formation occurs when each lung bud invaginates the ipsilateral pericar-dioperitoneal canal.

Agenesis of the lung (failure of the primitive lung bud to develop).
Laryngeal web (failure of complete canalization of the laryngeal cavity).
Congenital subglottic stenosis (due to defect in cricoid cartilage canalization).
Esophageal atresia with or without tracheoesophageal fistula (TEF) (results from abnormal division of the tracheoesophageal septum). Neonates show vomiting or choking after breastfeeding.
Respiratory distress syndrome (failure of alveoli ventilation due to insufficient surfactant production).
Congenital cysts of the lung (formed by dilation of terminal or larger bronchi).
Accessory lung lobe (arises from trachea or esophagus).