1) The pleural space is located between the lungs and chest wall, containing a thin layer of fluid. Fluid enters and leaves the space constantly through the parietal and visceral pleura. 2) Fluid accumulates in the pleural space when the rate of fluid formation exceeds the rate of lymphatic drainage. Transudative effusions result from systemic factors altering fluid movement, while exudative effusions occur when the pleura are inflamed. 3) Many diseases can cause pleural effusions by increasing pleural capillary pressure, permeability, or decreasing serum oncotic pressure. Inflammation of the pleura is a common cause of exudative effusions.

1. PLEURAL EFFUSIONS
BY: Jehad Abdullah Ali
1

2. Contents2
Anatomy and Mechanism of pleural fluids
turnover
Etiology and pathogenesis of pleural
effusions

3. The pleural space is not really a space but
rather a potential space between the lung and
chest wall.
It is a crucial feature of
the breathing apparatus
since pleurae serves as
a coupling system between
the lung and chest wall.
Introduction3

4. Introduction
4
There is normally a very thin layer of fluid (from
2 to 10 m thick) between the two pleural
surfaces, the parietal pleura and visceral
pleura. The pleural space and the fluid within it
are not under static conditions.
During each respiratory cycle the pleural
pressures and the geometry of the pleural
space fluctuate widely. Fluid enters and leaves
the pleural space constantly .
(-2) (-8)

5. Anatomy of the Pleural Space
The serous membrane
covering the lung
parenchyma is called the
visceral pleura.
The remainder of the lining of
the pleural cavity is
designated the parietal
pleura.
The parietal pleura receives
its blood supply from the
systemic capillaries.
The visceral pleura is
supplied predominantly by
branches of the bronchial
artery in humans.
SC: Systemic capillaries PC: Pulmonary capillaries

6. Anatomy of the Pleural
Space
The lymphatic vessels in the
parietal pleura are in direct
communication with the
pleural space by means of
stomas.
These stomas are the only
route through which cells
and large particles can leave
the pleural space.
Although there are abundant
lymphatics in the visceral
pleura, these lymphatics do
not appear to participate in
the removal of particulate
matter from the pleural
space.
6
SC: Systemic capillaries PC: Pulmonary capillaries

7. Figure 1. Anatomy of the pleural space
SC: Systemic capillaries PC: Pulmonary
capillaries
7
stomas
stomas
electronic microscopy

8. Figure 2. pleural fluids turnover
PF enter the pleural space through parietal & visceral pleurae,
And leave pleural space through lymphatics in parietal pleura

9. Mechanism of pleural fluids turnover
 The passage of protein-free liquid across the pleural
membranes is dependent on the hydrostatic and
oncotic pressures across them.
 When the capillaries in the parietal pleura are
considered, it can be seen that the net hydrostatic
pressure favoring the movement of fluid from these
capillaries to the pleural space is the systemic
capillary pressure (30cm H2O) minus the negative
pleural pressure (-5cm H2O) or 35cm H2O.

10.  Opposing this is the oncotic pressure in the
blood (34cm H2O) minus the oncotic
pressure in the pleural fluid (5 cm H2O), or
29cm H2O.
 The resulting net pressure differences of 6
cm H2O (35-29) favors movement of fluid from
the parietal pleura into the pleural space.
10
Count's

11. Mechanism of pleural fluids turnover
 The net rate of pleural fluid formation in animals with
thick pleura is approximately 0.01 ml/kg/hr or 15 ml
per 24 hr.
 Normally, the pleural space is maintained nearly fluid
free because the filtered fluid is removed from the
pleural space by the pleural lymphatics, which can
remove remove over 0.20 ml/kg/hr . or 300 mL/day.

12. Pathophysiology
13
 Pleural fluid will accumulate when the rate
of pleural fluid formation is greater than the
rate of pleural fluid removal by the
lymphatics.
Pleural effusions have classically been
divided into
Transudative
exudative

13. Pathophysiology
14
A transudative pleural effusion
occurs when alterations in the
systemic factors that influence
pleural fluid movement result in a
pleural effusion. Examples are
elevated visceral pleural capillary
pressure with left heart failure,
elevated parietal pleural capillary
pressure with right heart failure, and
decreased serum oncotic pressure
with the nephrotic syndrome, hepatic
cirrhosis.

14. Dr. Canmao xie
15
 In contrast, exudative pleural
effusions occur when the pleural
surfaces themselves are altered.
Inflammation of the pleura, leading to
increased protein in the pleural
space, is the most common cause of
exudative pleural effusions.

15. Etiology and Pathogenesis
Many diseases can cause pleural effusions
Elevated pleural capillary pressure, such as
congestive heart failure, pericardial disease,
increased blood volume, et al
Elevated pleural permeability, such as pleural
inflammation, neoplastic pleural disease
(metastatic disease or mesotheliomas),
pulmonary emboli, systemic lupus erythematosus
(SLE), et al

16. cont
17
Decreased serum oncotic
pressure, such as cirrhosis,
nephrotic syndrome, myxedema,
et al
Dysfunction of parietal pleura
lymphatics drainage

17. Thank you for attention!
18