The pleura of the lung is very similar to the serous pericardium; it consists of visceral (shiny) and parietal layers, with nothing but serous fluid in between.
The parts of the pleura are named after the surfaces they face:
- Diaphragmatic part
- Costal part
- Pericardial (or medisatinal) part
- Cupula pleura (or cervical) part
Both visceral and parietal pleura are continuous with each other at the hilum — pulmonary ligament.
Thoracic wall and the pleura of the lungs — OpenStax — CC BY-SA 4.0
Pleura of the lungs — Copyright © Meddists.com
Medial surface of the right lung — Copyright © Meddists.com
Lines and projections4
Before we continue with the surface projections of the lungs and their pleurae, we’ll have to split the body into several longitudinal lines.
- There are 12 of these lines in total :
- 5 on each side plus 2 median lines — one anteriorly and one posteriorly, and they are all parallel to each other.
- The anterior median line is also called the sternal line, as it passes directly through the sternum.
- When lifting the arms and exposing the axillary fossae, these are the lines:
- Midclavicular line
- Parasternal line (between midclavicular and anterior median lines)
- Anterior axillary line (anterior axillary fold, lateral border of pectoralis major)
- Midaxillary line (apex of the axillary fossa)
- Posterior axillary line (posterior axillary fold, anterior part of latissimus dorsi and teres major)
- Paravertebral line (between scapular and posterior median lines)
- Scapular line (inferior angles of scapula)
Body lines — Copyright © Meddists.com
Anatomists and clinicians may use different terminologies to describe these lines — hence, some refrain from using the term parasternal line — they use “parasternal region” instead, which is the region between the sternal margin and the parasternal line.
A plane is a two-dimensional surface, opposed to a line — which is one-dimensional.
- The following planes are not that important for now, but you should be familiar with them and be able to find them
- Transpyloric plane (a horizontal plane passing through the pylorus of the stomach — located between the jugular notch and the superior border of the pubic symphysis, at the level of the L1 vertebral body and the costal cartilage of the 9th rib)
- Subcostal plane (a horizontal plane passing through the inferior borders the costal arches, at the level of the L3 vertebral body)
- Supracristal plane (a horizontal plane passing through the iliac crests, at the level of the L4 vertebral body)
- Transtubercular (or intertubercular) line (a horizontal passing through the iliac tubercles, at the level of the L5 vertebral body — also equals to one of the external diameters of the pelvis)
- Parasternal line — 2-4 ribs (L), 2-6 ribs (R)
- Midclavicular line — 7th rib
- Anterior axillary line — 10th rib
- Scapular mine — 11th rib
- Paravertebral line — 12th rib
There are three sinuses formed by the junction of the pleurae:
- Costomediastinal recess
- Costodiaphragmatic (or phrenicocostal) recess
- Phrenicomediastinal recess
Cross section at the level of T4 vertebra, the costomediastinal recess (sinus) is visible to the sides of the anterior mediastinum — Copyright © Meddists.com
Physiologically, these recesses are empty apart from the thin layer of serous fluid, allowing movement and expansion of the lungs (the lungs descend towards the costodiaphragmatic recess, being the biggest and most important).
In some cases, however, blood or pus can accumulate in the costodiaphragmatic recesses. We can collect the fluid and examine it via a needle.
In your practice, you might be asked to find the costodiaphragmatic recess. To do so, you should place your hand along the side of the ribs, above the diaphragm.
1. Moore, Keith L., et al. Clinically Oriented Anatomy. Wolters Kluwer, 2018.
2. Standring, Susan, and Henry Gray. Gray’s Anatomy: The Anatomical Basis of Clinical Practice. Elsevier, 2016.
3. Bertalan, Csillik, et al. Regional Anatomy. Medicina, 2008.
4. T. Hajdú, M. Harangi, Z. Hegyi and V. Szegeczki, et al. Surface projections of thoracic viscera. Department of Anatomy, Histology & Embryology, University of Debrecen, 2019.