Respiratory Sytem

7/23/2019 Respiratory Sytem

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RESPIRATORY SYTEM


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Mammals breathe through an organ calledLungs. Air enters the lungs in a system of

passageways that arborize, branching like atrunk, branches and twigs of a decidous tree.At the end of the smallest passageways alveolilined by a respiratory epithelium are the sites

of gaseous exchange. Oxygen depleted andcarbon dioxide-enriched air, along withmetabolic water is exhaled via the same pathby which the air entered. [Video]
http://breathing%20respiration%20animation-part%202%203d-makemegenius.com%20series%20of%20education%20videos%20-%20youtube.flv/http://breathing%20respiration%20animation-part%202%203d-makemegenius.com%20series%20of%20education%20videos%20-%20youtube.flv/


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Usually exhibit

several lobes,asymmetrically,

with one more

on the right.


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However the lungs of a

number of aquatic and

terrestrial mammals are

not lobed.

Ex. Sirenians (sea cow/

dugong)


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And some are lobed on

the right side only

-are mammals that lay eggs.

Among the living mammals theyinclude the platypus and four

species of echidnas (or spiny

anteaters)

Ex. Monotremes


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Platypus


the right side only

Ex. Monotremes




anteaters)


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spiny anteaters


the right side only

Ex. Monotremes




anteaters)


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Left and right lung occupy separate pleural

cavities separated completely in the midline

by the mediastinum, a septum consisting of

loose (areolar) connective tissue that serves as

packing for all the organs of the thorax except

the lungs, and including principally the

esophagus, the heart within the pericardialsac, thymus, major descending and ascending

vessels, nerves and lymphatics, and the lower

end of the trachea.


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Mediastinum

Anterior

Middle

Posterior


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The trachea divides into two primary bronchi,

each of which penetrates a lung at the hilus and

divides into one secondary bronchus for eachlobe, when lobe is present. These gives rise to

tertiary bronchi that branch and rebranch into

smaller and smaller passageway, the last of

which opens into several to a dozen thin walled

alveolar ducts.


12/37*highlight the primary b.


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The walls of the bronchi and larger

bronchioles contain:

Smooth muscle fibers Connective tissue

Irregular cartilaginous plates

and lined with a ciliated pseudostratified

columnar epithelium cells


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As the branches becomes smaller, the cilia arelost, the epithelium becomes flatter, the

cartilage disappears, and then, in some

mammals atleast, the smooth muscle cells

disappear.


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The walls of the ducts are evaginated to form

clusters ofalveoli, or respiratory pockets,

estimated to number over 300 million eachhuman lung. It is these alveoli that gaseous

exchange takes place.

Alveoli are lined by a simple squamousepithelium(pavement cells) beneath which

is a rich plexus of capillaries held together by a

close network ofreticular connective tissue

fibers.


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Alveolar sacs consist of two or more alveoli

that share a common opening.


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Red blood cells in the capillaries take an

oxygen to form oxyhemoglobin, and carbondioxide and some metabolic water pass from

the blood plasma into the alveoli to be

exhaled


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The parietal peritoneum of each pleural

cavity lines the chest wall as the parietalpleura and covers the cephalic surface of

the diaphragm as the diaphragmatic

pleura.


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At the root of each lung, where the

primary bronchus and pulmonaryvessels enter and leave, the parietal

pleura is continuous with the

visceral pleura that lies on the

surface of the lung.


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The space between the parietal and visceral

pleurae is the actual pleural cavity. It

surrounds the lung except at the hilus. A

subatmospheric pressure exists in the pleuralcavity , and the higher normal atmospheric

pressure exerted via the passageway from

nares to alveoli keeps highly elastic wall of thelung in intimate contact with the thoracic wall

at all times, with only a thin layer of serous

lubricant intervening.


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The lubricant is a product of the pleural

mesothelium. The fluid minimizes friction

between lungs and chest walls as the latter

rises and falls with each inhalation andexhalation.

Inflammation of the pleura causes an increase

of fluid in the cavity, a condition known aspleurisy. Perforation of the thoracic wall and

the parietal pleura from a gunshot for

example allows atmospheric air to enter the


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The pleural cavity, resulting in deflation of the

lung on that side , a condition known as

pneumothorax.


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Lets listen to an explanation


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accomplished primarily by a

dome-shaped muscular

diaphragm (unique in

mammals) that functions as

a suction pump.

Anchored to the

xiphoid process of the

sternum ventrally

to a half dozen or so of thecaudalmost ribs and their

costal cartilages laterally

And to several of the more

anterior lumbar vertebrae

dorsally

The dome bulges

cephalad into the

thoracic cavity when

not under tension. Contraction of the

diaphragmatic muscles

flattens the diaphragm,

this further decreasesthe already

subatmospheric

pressure within the

pleural cavity.


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Consequently, normal

atmospheric pressure,

continually exerted via

the nares andrespiratory tract,

pushes more air into

the lungs to fill the

vacuum.

The diaphragm acts as a

suction pump because

it creates a vacuum that

causes air to be suckedinto the duct system.


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Is largely a passive phenomenon attributable

to the following:

1. Relaxation of the diaphragm, which returns it to

the domed position, decreasing the volume of thethorax and restoring (increasing) the pressure

around the lungs to the resting subatmospheric

level

2. the upward pressure exerted on the relaxing

diaphragm by the resuent abdominal viscera

which are under compression while the

diaphragm is flattened


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3. resilience of the abdominal wall, which bulges

when the abdominal viscera are compressed

4. return of the ribs to a resting position as the

intercostal and supracostal muscles relax 5. elasticity of the lungs, which enables them to

conform to these changes.


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As a result, air is squeezed out of the lungs.

During forceful expiration, a in panting,

roaring, coughing, or when a trained singer is

performing, the abdominal wall participatesactively in the expulsion of air.


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Marine mammals that seek their food in the

depths of the oceans have exceptionally

muscular diaphragms. The water spout of a

whale for instancethe sign that exhalation istaking place last 3-5 minutes.


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Also deep-sea foraging marine mammals do

not store oxygen in their lungs in anticipation

of a dive. While animal is breathing at the

surface, oxygen entering the lungs istransferred immidiately to rete mirabilia of the

blood stream. The animal then exhales before

comencing a dive and breathing may not takeplace again for as long as 2 hours. The lungs

collpase totally shortly after the dive gets

underway.


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END


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Some comparison

Lungs are like the gill of fishes, which extracts

oxygen. They have the same end product and

function, its just that the gill works on water

and the lungs does not.

Lungs differ from those of birds in that the

incoming air enters a system of passageways

that arborize, branching like a tree


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Mammalian lungs usually exhibit several

lobes, asymmetrically, with one more on the

right.

The


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why we couldn't breathe liquid unaided, as in

the film The Abyss; our lungs lack the power

needed to pump a dense fluid in and out

quickly enough by themselves.)

If you live in the sea, it makes sense to have

gills, right? Wrong. No. 1 on a recent list of

evolutionary mistakes was the fact thatwhales have blowholes, not gills.
http://www.newscientist.com/article/mg18925331.300-breathing-in-oceans-full-of-air.htmlhttp://www.imdb.com/title/tt0096754/http://www.wired.com/science/discoveries/magazine/17-08/st_besthttp://www.wired.com/science/discoveries/magazine/17-08/st_besthttp://www.wired.com/science/discoveries/magazine/17-08/st_besthttp://www.wired.com/science/discoveries/magazine/17-08/st_besthttp://www.imdb.com/title/tt0096754/http://www.newscientist.com/article/mg18925331.300-breathing-in-oceans-full-of-air.html


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How about mammals under water

Adaptations of the Respiratory SystemThe BlowholeUnlike other mammals who breathethrough their nostrils and mouth, dolphins breathe through the blowhole, which is situated on

the top on its head. A reason for this difference is that the blowhole will facilitate the breathing

at the surface of the water. Since the blowhole is at the top of the head, only a small region of

the head is required to break the surface of the water to inhale air.

The dolphin starts to exhale before reaching the surface and this helps to reduce the amount of

time spent breathing at the surface. Dolphins can catch a breath about five times in a minute

before diving again, without hindering the progress of their swim. Usually, a dolphin breathes

two to four times each minute when it is swimming near the surface. It can hold its breath for

seven minutes or more when it is diving.

The LungsThe lungs of dolphins are not significantly larger or smaller than the land mammals.

Obviously, the size of the lungs does not determine the amount of oxygen that can be stored

and utilized.

However, the dolphin lungs contain a lot more alveoli (air cells) than human lungs do. Dolphin

lungs are made up of two layers of capillaries, and this arrangement increases the efficiency of

gas exchange since most mammals have only one layer of capillary. Therefore, this means that

the surface area of the lungs have been greatly increased and gas exchange can occur more

quickly.

The pleurae of dolphins are thick and elastic. The pulmonary tissue proper contains a generous

supply of myoelastic fibers for better elasticity. The bronchial tubes are lined with muscular

tissue. Tiny bronchioles are found together with sphincters that cut off the alveoli from the rest

of the lung.

These anatomical mechanisms attribute to a more efficient exchange of gas. In dolphins,

residual air - the fixed volume of air that always remain inside the lungs - never exceeds 15

percent of total capacity, and their vital capacity - the volume of air that is exchanged

frequently - is over 85 percent. In some cases, the vital capacity can even reach 92 percent.Normally in human, only 10 to 20 percent of the air in the lungs are exchanged. But in dolphins,

about 80 to 90 percent is renewed, so that their body can get as much oxygen as possible.

The respiratory system of whales certainly has some unusual features, but they are adaptations

to prevent water entering the airways: the nasal passages are complex and convoluted, and the

larynx (the upper end of the respiratory tube) extends up into the nasal cavity rather than

opening into the throat. Powerful muscles form a special plug within the blowhole, preventing

water from entering the lungs when the dolphin is underwater.

Respiratory Sytem

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