What is blood supply of heart? bot what is given sup from Knous bold in Lungo! CO2 What is laseen up? to what is this aue! Diffusion. whar in bed. carries O. ? Staemoglobi what is origin of the ling? Dicitie ulum from Alimentary caval Have the 2 Essential parts to the ling? I Conducting portion secretory portion (-) Bronchisate I of the cavities;) Dearby Ling of News & Frog In news is no ce sac like porucation which correspore do to the is.

fundibuli

ли

huwan lung,

What's the structure of

in the

lungs?

The septa

Epi. Cells bon

Сармана

trave Enclosing capillarie Describe the Brouchus beguner

with trachea &

& going to End.

tracked, Rh & L. Bronchia the Interlobular B, the Intra

Lobular, the Infrandibulent

Alveoli

What is the struc.

ture

78 Infrastebur Consists of Con. ter with capillarie but the Infor dibula

Describe tracked.

In perpe Describe Brouchiol.

точе

disappear. Elastic

rugs

What in purpose of Rugs?

where are

he Aymphatics of the lungs ?

In the con his underneath the Epi.

thelin. Where are the glands of the tracked. In submucous wat what secreting alles? Goblets withe Episkelin self.

What is the mere supply?

What in dig. brt. action of ragus in hing in wart? de lung istrell Cause increased resp. & in Hart A Ca inhibits.

H

are composed of the ultimate ramifications of the bronchial tubes, within. which are contained the air vesicles or cells. The walls of the air vesicles, exceedingly thin and delicate, are lined internally by a layer of tessellated epithelium, externally covered by elastic fibers, which give the lungs their elasticity and distensibility.

The Venous Blood is distributed to the lungs for aeration by the pulmonary artery, the terminal branches of which form a rich plexus of capillary vessels surrounding the air cells; the air and blood are thus brought into intimate relationship, being separ

ated only by the delicate walls of the air cells and capillaries.

The thoracic cavity in which the respiratory organs are lodged is of a conical shape, having its apex directed upward, its base downward. Its framework is formed posteriorly by the spinal column, anteriorly by the sternum, and laterally by the ribs and costal cartilages. Between and over the ribs lie muscles, fascia and skin; above the thorax is completely closed by the structures passing into it and by the cervical fascia, and skin; below it is closed by the diaphragm. It is therefore an air-tight cavity.

FIG. 12.

The Pleura.-Each lung is surrounded by a closed serous membrane, the pleura, one layer of which, the visceral, is reflected over the lung, the other, the parietal, reflected over the wall of the thorax; between the two layers is a small amount of fluid which prevents friction during the play of the lungs in respiration.

The windpipe leading down from the larynx is seen to branch into two large bronchi, which subdivide after they enter their respective lungs.

Owing to the elastic tissue which is present in the lungs, they are very readily distensible, so much so, indeed, that the pressure of the air inside the trachea and lungs is sufficient to distend them until they completely fill all parts of the thoracic cavity not occupied by the heart and great vessels. The elastic tissue endows them not only with distensibility, but also with the power of elastic recoil, by which they are enabled to accommodate themselves to all variations in the size of the thoracic cavity.

When the chest walls recede, the air within the lungs expands and presses them against the ribs; when the chest walls contract, the air being driven out, the elastic tissue recoils and the lungs return to their original condition. The movements of the lungs are therefore entirely passive.

As the capacity of the chest in a state of rest is greater than the volume of the lungs after they are collapsed, it is quite evident that in the living condition the lungs are distended and in a state of elastic tension, which is greater or less in proportion as the thoracic cavity is increased or diminished in size. The elastic tissue, always on the stretch, is endeavoring to pull the visceral layer of the pleura away from the parietal layer, but is antagonized by the pressure of the air within the air passages. This condition of things persists as long as the thoracic cavity remains air tight; but if an opening be made in the thoracic wall, the pressure of the external air which was previously supported by the practically rigid walls of the thorax now presses upon the lung with as much force as the air within the lung. The two pressures being neutralized, there is nothing to prevent the elastic tissue from recoiling, driving the air out, and collapsing. The elastic tension of the lungs can be readily measured in man after death by inserting a manometer into the trachea. Upon opening the thorax and allowing the tissue to recoil, the air presses upon the mercury and elevates it, the extent to which it is raised being the index of the pressure. Hutchinson calculated the pressure to be one-half pound to the square inch of the lung surface.

Respiratory Movements.-The movements of respiration are two, and consist of an alternate dilatation and contraction of the chest, known as inspiration and expiration.

1. Inspiration is an active process, the result of the expansion of the thorax, whereby air is introduced into the lungs.

2. Expiration is a partially passive process, the result of the recoil of the elastic walls of the thorax, and the recoil of the elastic tissue of the lungs, whereby the carbonic acid is expelled.

In Inspiration the chest is enlarged by an increase in all its diameters, viz. :

1. The vertical is increased by the contraction and descent of the diaphragm when it approximates a straight line.

2. The antero posterior and transverse diameters are increased by the elevation and rotation of the ribs upon their axes.

In ordinary tranquil inspiration the muscles which elevate the ribs and

Why does the diaphragm petat? descendre respiration ? What is dif. bet. male of smaller breaching? How is labored inspiration produced? In labourd Rx. how init produced?

What changes in air itself taxes place in respiration? How in the air acted upon in the

M

lungs? Is Expired our saturated? In Expired. air whorn ratio of 0. tothar Inspired?

Where is CO2 most

plintful?

How much CO2 par ordniary air? _04 7%. How about N?

How much CO2 given off arrach

than

breath. Why
is less air experis
that inspired? What else braide
Con is going? What gives

breath? In 100vols

o dor to the

of air blood (urs) how much Q. ! 207 Venous ? Sch 12%

To 3657