LUNGS (OX) |
Ox
- The lungs, the essential organs of respiration
are right and left and each occupy the greater part of
the thoracic cavity
- They are accurately adapted to the walls of the
cavity and the other organs contained in it. Each lung is soft, spongy and
highly elastic
- It crepitates when pressed and floats in water
- The colour varies according to the amount of
blood contained in the lung. During life, it is pink in colour
- In dissected bodies, it is light grey in colour
and slightly tinged with red. The average weight of lungs is 3.4 kg
- The right lung weighs about half as much as the
left one
- The fetal lung presents the following characters,
- It is much smaller
- It is firmer and does not crepitate
- It is pale grey in colour
- It sinks in water
- In form, the lungs are like the casts of the
cavities in which they are situated
- When well hardened in situ, their surfaces
present impressions and elevations corresponding exactly to the structures
with which they are in contact
- The right lung is larger than the left.
- Each lung presents for description two surfaces,
two borders, a base and an apex. The costal surface is convex and lies
against the lateral wall of the thorax, it presents impressions of the
ribs
- The mediastinal surface is less extensive
and molded on the mediastinum and its contents
- It presents a little in front of it middle, an
irregular depression -the hilus of the lung where the structure, which
compose the root of lung, enter or leave the organ
- In front of the root, each lung presents a large
cavity adapted to the heart -the cardiac impression. Behind
the hilus and slightly above it are two grooves -a dorsal one for the
aorta and a ventral for the oesophagus.
- The dorsal border is long, thick and rounded. The
ventral border is thin and presents two deep fissures, which divide the
lungs into a variable number of lobes
- The left lung presents a large quadrilateral
cardiac notch extending from the ventral end of the third intercostal
space to the fourth intercostal space and here the pericardium and heart
are in contact with the chest wall. Behind this notch there is a fissure
- The fissure and notch divide the left lung into
three lobes - the one in front of the cardiac notch is the apical
lobe, and behind it is the cardiac lobe and behind the fissure is
the diaphragmatic lobe. On the right lung, there
are two fissures on the ventral border dividing it into apical, cardiac
and diaphragmatic lobes
- The apical lobe is divided into two parts by a
deep fissure
- The apical lobe of the right lung is much larger
than that of the left lung and occupies the space in front of the
pericardium, pushing the mediastinum against the left wall
- The apical lobe of the right lung receives a
special bronchus from the trachea opposite the third rib or space and is
adherent to the trachea from here backward
- The mediastinal face presents a small mediastinal
or intermediate lobe.
- The base of the lung is oval in outline; its
surface (diaphragmatic surface) is deeply concave, in adaptation to
the thoracic surface of the diaphragm
- Laterally and dorsally it is limited by a thin
convex basal border, which fits into the narrow recess between the diaphragm
and lateral chest wall.
- The apex of the lung is prismatic, narrow and
flattened transversely. It curves downward, and is related deeply
to the cranial mediastinum and to the cranial part of the pericardium.
- The root of the lung is composed of the structures, which enter
or leave the lung at the hilus on the mediastinal surface. These are
- The bronchus
- The pulmonary artery
- The pulmonary veins
- The bronchial artery
- The pulmonary nerves and
- The pulmonary lymph vessels
- The bronchus is situated dorsally with the bronchial artery on
its upper surface and the pulmonary artery immediately below it
- The pulmonary veins lie chiefly below and behind the artery
Bronchi
- Each bronchus enters the hilus of the lung
- The left bronchus first gives off a branch, which supplies both
the apical and cardiac lobes and is then continued as the stem bronchus to
the diaphragmatic lobe
- The right bronchus gives off a branch, which supplies the
cardiac lobe and is continued as the stem bronchus to the diaphragmatic lobe
- A branch is detached from the medial face of the stem bronchus
to the mediastinal lobe
- The apical bronchus from the trachea supplies the apical lobe. The lobulation of lung is very evident on account of abundant interlobular tissue
Sheep and Goat
- It resembles those of ox but differ from them in shape. There
is a cardiac notch
- Lobulation is much less distinct than in the ox
Horse
- The lungs of the horse are not divided by deep fissures, as in case
of most mammals
- The left lung consists of a chief part -the body and an apex.
In addition to these, the right lung has an intermediate lobe
- The lobulation of the lung is not very evident
on account of the small amount of interlobular tissue
- The trachea is not adherent to the lung
- The cardiac notch is larger in the right lung
than the left
- Behind the root of the lung, the two lungs are
adherent to each other on the triangular area. Behind the area of adhesion
the mediastinal pleura forms a fold called the pulmonary ligament
(ligament of lung)
Pig
- The right lung has four lobes- apical, cardiac, diaphragmatic
and intermediate
- In some cases, apical lobe is divided into two parts. Sometimes
it is fused with cardiac lobe
- Lobulation is distinct
- The apical bronchus is present for the right apical lobe at the
level of 3 rd rib
Dog
- The costal surface of lungs is convex
- Lobulation is not distinct
- Interlobular fissures are deep and extend to the root
- The right lung has four lobes and left has three
- The cardiac notch is larger on the right side than on the left
Rabbit
- Right lung has 4 distinct lobes- apical, cardiac, diaphragmatic
and intermediate lobes
- The left lung has only two lobes; apico-cardio and
diaphragmatic lobes
Fowl
- They are small and occupy the dorsal part of the thorax. They
are intimately adherent to the ribs and the costal impressions are deeper
- The stem bronchus enters the ventral surface of the lung about
its middle. It continues backwards through the lungs and opens into the
abdominal air sacs
- Within the lungs, the stem bronchus gives off secondary
bronchi, which enter the cervical, clavicular and thoracic air sacs
- Numerous tertiary bronchi radiate towards the periphery
AIR SACS OF
FOWL |
- The air sacs are
thin walled sacs lined with mucous membrane and covered by serous membrane
- They all form a means of communication between a
bronchus and the interior of some of the pneumatic bones
- There are eleven sacs, cervical,
clavicular, axillary, cranial thoracic, caudal thoracic and abdominal. All are paired
except the clavicular, which is single
- The thoracic air sac does not communicate with pneumatic bones
- The primary function of the air sacs is to compensate for the
small total capacity of the bird’s lung with the aid of respiratory
muscles, they act as bellows to ventilate the lung in such a manner that a
continuous stream of air passes through the air capillaries both during
inspiration and expiration
- This function carried out mainly by caudal thoracic and
abdominal air sacs. All the air sacs together contribute to the reduction
of the specific gravity of the avian body
- It is playing vital role in the regulation of the body
temperature
- It also helps in even distribution of the body weight during
the flight and in voice production
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