LUNGS.
1.INTRODUCTION:
These
are pair of airfilled structure in the respiratory system.
2.SITUATION :
Two lungs
lying on each side of the midline in the thoracic cavity.
3.MEASURMENTS
SHAPE: CONE
REGIONS
:
APEX
BASE
COSTAL SURFACE
MEDIAL SURFACE
4.ORGANS
ASSOSCIATED WITH LUNGS:
APEX:
v
It is rounded and rises into the root of the
neck.
v
About 25 mm above the level of the middle third
of the clavicle
v
It lies close to the first rib and blood vessels
and nerves in the root of the neck.
THE BASE:
v
This is concave and semilunar in shape.
v
Lies on the thoracic surface of the diaphragm.
THE COSTAL SURFACE:
v
This surface is convex in shape.
v
Lies against the costal cartilages, the ribs and
the intercostals muscles.
THE MEDIAL SURFACE:
v
This surface is concave and roughly
triangular-shaped area called “HILUM”.
v
It lies at the level of the 5th,6th
and 7th thoracic vertebrae.
v
Structures forming the root of the lung enter
and leave at the hilum.
v
The area between the lungs is called “MEDIASTINUM”.
v
It is occupied by the
heart,greatvessels,trachea,right and left bronchi,oesophagus,lymph nodes,lymph
vessels and nerves.
v
The right
lung is divided into three distinct lobes
·
SUPERIOR
LOBE
·
MIDDLE
LOBE
·
INFERIOR
LOBE
v
The left lung is smaller because the heart
occupies space left of the midline.
v
It is divided into two lobes
SUPERIOR And INFERIOR LOBE.
5.GROSS
STRUCTURE :
PLEURA AND PLEURAL CAVITY:
v
The
pleura consists of a closed sac of serous membrane(one for each lung) which
contains a small amount of serous fluid.
v
The lung is invaginated (pushed into) this sac
so that it forms two layers: one adhers to the lung and the other to the wall
of the thoracic cavity.
v
THE
VISCERAL PLEURA: This is adherent to the lung, covering each lobe and
passing into the fissures that separate them.
v
THE
PARIETAL PLEURA: This is adherent to the inside of the chest wall and the
thoracic surface of the diaphragm.
v
It remains detached from the adjacent structures
in the mediastinum and continous with the visceral pleura round the edges of
the hilum.
v
THE
PLEURAL CAVITY: This is only a potential space.
v
The two layers of pleura are separated by a thin
film of serous fluid which allows them to glide over each other.
v
It prevents friction between them during breathing.
v
The serous fluid is secreted by the epithelial
cells of the membrane.
The two layers
of pleura, with serous fluid between,behave in the same way as two pieces of
glass separated by a thin film of water.
They glide over each
other easily but can be pulled apart only with difficulty,because of the
surface tension between the membranes and the fluid.
If either layer of pleura is punctured,the underlying lung
collapses owing to its inherent property of elastic recoil.
INFERIOR OF THE LUNGS:
The lungs are composed of the bronchi and smaller air
passages,alveoli, connective tissue,blood vessels,lymphvessels and nerves, all
embeddednin an elastic connective tissue matrix.
6.BLOOD SUPPLY:
ARTERIAL SUPPLY :
The pulmonary
trunk divides into the right and left pulmonary arteries,it carries pure blood
.
VENOUS DRIANAGE :
two pulmonary bronchial veins carry the de-oxygenated blood.
7.NERVE SUPPLY:
PARASYMPATHETIC
NERVE SUPPLY:
The vagus nerves stimulate contraction of
smooth muscle in the bronchial tree causing BRONCHOCONSTRUCTION.
SYMPATHETIC
NERVE SUPPLY: Stimulation causes BRONCHODILATATION.
8.LYMPHATIC
SUPPLY :
Lymph
is drained from the walls of the air passages in a network of lymph vessels.
It passes through
lymph nodes situated around the trachea and bronchial tree then into the thoracic duct on the left side
and right lymphtic duct on the other.
9.FUNCTIONS:
v
Control of air entry.
v
Warming and humidifying
v
Support and patency.
v
Cough reflex.
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