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I. ANATOMY AND PHYSIOLOGYRespiration is necessary because all l iving cells of the bodyrequireoxygen and produce carbon dioxide. The respirationsystem assists in gasexchange and performs other formation

as well our body needs ac o n s t a n t s u p p l y o f o x y g e n t o s u p p o r t m e t a b o l i s m . T h e r esp i r a t or y s ys te m br in gs oxygen through the a irways of lungsinto the alveoli, where it diffuses intothe blood for transport tothe tissue, this process is so vi tal that diff icul t i nbreathing isexpected as a threat to life in self. The respiratory system allows oxygenfrom the air to enter the blood and carbon dioxide to leave the bloodandenter the air. The cardiovascular system transport oxygen from the lungstothe cells of the body and carbon dioxide. Without healthy respiratoryandcardiovascular system, the capacity to carry out normal activity is

reduced,and without adequate respiratory and cardiovascular system fr ic ti on , li fe itself is possible.

Nose-The term nose refers to the visible str ucture that forms aprominentfeature of the face. Most of the nose is composed of cartilage,although thebridge of the nose consists of bone the bone andcart il age and covered by connective tissue and shin.

Nasal cavity-The nasal extends from the noses to the choane the nares

orn o s t r i l s a r e t h e e x t e r n a l o p e n i n g o f t h e n o s e an d t h e c h o a n e a r e t h e openings to the pharynx. The noseis formed from both bone and cart il age. The nasal bone forms thebridge and the remainder of the nose is composedof cartilage andconnective tissue. Each opening of the nose to the face leadsto the cavity.The vestibule is lined anteriorly to the skin and hair that filterforeignobjects and prevent from being inhaled. The posterior vestibuleislined with a mucous membrane, composed of columnar epithelial cellsand,g o b l e t s c e l l s t h a t s e c r e t e m u c o u s . T h em u c o u s m e m b r a n e e x t e n d s t h r o u g h o u t t h e a i

r w a y s a n d c i l i a p r o p e l m u c o u s t o t h e p h a r yn x f o r elimination by swallowing or coughing. The portion of mucous membrane thatislocated at the top of the nasal cavity, just beneath thecribriform plateof t h e e t h m o i d b o n e , i s s p e c i a l i z e d e p i t h e l i u m ; w i t c h p r ov id es th e se ns e o f smell.

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Along the side of the vestibule are turbinate, mucousmembrane coveredprojections that contain a rich blood supplyfrom the in ternal and exte rnal carotid arteries. They warmand humidify inspired air.

Paranasal sinuses- open areas within the skull are named for the bones inwi tch they l ie:frontal, ethmoid, sphenoid and maxillary. Passagewayfromparanasal sinuses drain into the nasal cavity. Thenasolac rima l duc t, wi tch drain tears from the surface of the eyes, alsodrains the nasal cavity.

Pharynx-it is a funnel-shaped tube that extends from the nose to the larynx.It isthe common passageway of both the respiratory and digestive system.Itcan be divided into three regions:a.Nasopharynx- is loca ted above

the marg in of the soft pala te andreceives air from the nasal cavity.From the ear, the Eustachiantubes open in to the nasopharynx.The pharyngeal tonsils arelocated on the posterior wall of thenasopharynx.b .Oropharynx- serves both resp i ra t ion andd i g e s t i o n . I t r e c e i v e s air from the nasopharynx and food from theoral cavity. Palatinetonsils are located along the sides of theposterior mouth, andthe lingual tonsils are located at the base of thetongue.

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c . L a r y n g o p h a r y n x - l o c a t e d b e l o w t h e b a s e o f t h et o n g u e , i s t h e most infer ior port ion of the pharynx. I t connectsto the larynxand serves both the respiration and digestion.

Larynx-

i s c o m m o n l y c a l l e d t h e v o i c e b o x . I t c o n n e c t s t h eu p p e r a n d lower airway. It lies just anterior to the upper esophagus. Ninecartilagesfo r m t he l a r yn x : ep i g l o t t i s , t h y ro id , c r i c o id , a r y th en o i d, c o rn i c u l at e, cuneiform. The cart i lage are attach tothe hyoid bone above and belowthe trachea by muscles andligaments. The slit the vocal cords forms theglottis. The epiglottis, a leafshaped structure immediately posterior to thebase of the tongue. Thethyroid cartilage protrudes in front of the larynxforming the Adams apple.

Trachea-extends from the larynx to the level of the seventh

thoracicvertebrae, where it divides into two main bronchi. The point atwitch thetrachea divides is called carina. The trachea is a flexible,muscular, 12cmlong air passage with C-shaped cartilaginous ring.

Lungs-it l ie within the thorac ic cavity on either side of the heart.Theyare cone-shaped, with the apex above the first rib and the baseresting onthe diaphragm. Each lung is divided into superior and inferiorlobes by anoblique fissure. The r ight lung is f urther divide by ahorizontal f issure ,witch bounds a middle lobe. The right lung therefore

has three lobes. Thelung contains gas, blood, and thin alveolar walland support structure. Thealveolar walls contain elastic and collagen fibers.These fibers are capableof stretching when the pulling force is exerted onthen from outside of thebody or whey they are inflated from within.

Alveoli-the lungs parenchyma, consists of mill ions of alveolar units,isthe working area of the lung tissue it birth a person has approximately24million alveol i, by the age 8 yrs a person 300 mill ion. Thetotal workingalveolar surface are is the approximately 750 to 860 squarefeet. Oxygenand CO

2are exchange through the respiratory membrane about 0.2mmt h i c k ( T h e a v e r a g e d i a m e t e r o f t h e p u l m o n a r y c a p i l lary only about 5mins).

Thorax

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- provides protection for the l ungs, heart and great vessels.Theouter shell of the thorax is made up of 12 pairs of ribs. The ribsconnectspos te r i o r t o t he t r an sve rs e p roc ess es o f t h e t hor a c i c v e r t e b r a e o f t h e

Respiratory System, in anatomy and physiology, comprises of organs that

deliver oxygen to the circulatory system for transport to all body

ce l ls. Ox yge n is es sen ti al fo r cells, which use this vital substance to liberate

the energy needed for cellular activities. Inaddition to supplying oxygen, the

respiratory system aids in removing of carbon dioxide, preventing

the lethal buildup of this waste product in body tissues. Day-in and

day-out,w i t h o u t t h e p r o m p t o f c o n s c i o u s t h o u g h t , t h e

r e s p i r a t o r y s y s t e m c a r r i e s o u t i t s l i f e - sustaining activities. If the

respiratory systems tasks are interrupted for more than a fewminutes, serious,

irreversible damage to tissues occurs, followed by the failure of all bodysystems,

and ultimately, death.

W h i l e t h e i n t a k e o f o x y g e n a n d r e m o v a l o f c a r b o n d i o x i d ea r e t h e p r i m a r y f u n c t i o n s o f t h e r e s p i r a t o r y s y s t e m , i t p l a y

s o t h e r i mp o r t a n t r o l e s i n t h e b o d y . Th e respiratory system helpsregulate the balance of acid and base in tissues, a process crucialfor the normal

functioning of cells. It protects the body against disease-causing organismsandtoxic substances inhaled with air. The respiratory system also

houses the cells thatdetect smell, and assists in the production of sounds forspeech.The respiratory and circulatory systems work together to deliver oxygen to

cellsand remov e carbo n dioxid e in a two -phase p rocess c alledre sp irat ion. The fi rs t phas e of respiration begins with breathing in, or

inhalation. Inhalation brings air from outside the body into the lungs. Oxygen inthe air moves from the lungs through blood vessels to theheart, which pump s

the oxygen-rich blood to all parts of the body. Oxygen then

movesfrom the bloodstream into cells, which completes the firstphase of respiration. In thecells , oxygen is used in a separateenergy-producing process called cellular respiration,which produces

carbon dioxide as a byproduct. The second phase of respirationbeginswith the movement of carbon dioxide from the cells to the bloodstream.

The bloodstreamcarries carbon dioxide to the heart, which pumps the

carbon dioxide-laden blood to thelungs. In the lungs, breathing out,

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or exha lation, remove s carbon dioxi de from the body, thus completing

the respiration cycle.II. StructureThe organs of the respiratory system extend from the nose to the

lungs and aredivided into the upper and lower respiratory tracts. The upperrespiratory tract consists of the nose and the pharynx, or throat. The

lower resp ira tor y tra ct inc lud es the lar ynx , or voice box; the trachea, orwindpipe, which splits into two main branches called bronchi

tiny branches of the bronchi called bronchioles; and the lungs, a pair

of saclike, spongyorgans. The nose, pharynx, larynx, trachea,

bronchi, and bronchioles conduct air to andfrom the lungs. Thelungs interact with the circulatory system to deliver oxygen

andremove carbon dioxide.

A. Nasal PassagesAnatomy of the NoseThe uppermost portion of the human respiratory system, thenose is a hollow air passage that functions in breathing and in the sense of smell.

The nasal cavity moistensand warms incoming air, while small hairs and mucus

filter out harmful particles andmicroorganisms.The flow of air from outside of thebody to the lungs begins with the nose, whichi s d i v i d e d i n t o t h e l e f t

a n d r i g h t n a s a l p a s s a g e s . T h e n a s a l p a s s a g e s a r e l i n e d w i t h

a membrane composed primarily of one layer of flat, closely packed cells calledepithelialc e l l s . E a c h e p i t h e l i a l c e l l i s d e n s e l y f r i n g e d w i t h t h

o u s a n d s o f m i c r o s c o p i c c i l i a

fingerlike extensions of the cells. Interspersed among the epithelial cells are goblet

cells,specialized cells that produce mucus, a sticky, thick, moist fluid that coats theepithelialc e l l s a n d t h e c i l i a . N u m e r o u s t i n y b l o o d v e s s e l s

c a l l e d c a p i l l a r i e s l i e j u s t u n d e r t h e mu co us me mb ra ne , ne ar th e

surface of the nasal passages. While transporting air to

the p h a r y n x , t h e n a s a l p a s s a g e s p l a y t w o c r i t i c a l r ol e s : t h e y f i l t e r t h e a i r t o r e m o v e potentially disease-

causing particles; and they moisten and warm the air to protect

thestructures in the respiratorysystem.Filtering prevents airborne bacteria, viruses, other potentially

disease-

causings u b s t a n c e s f r o m e n t e r i n g t h e l u n g s , w h e r e t h e y m a yc a u s e i n f e c t i o n . F i l t e r i n g a l s o e l i m i n a t e s s m o g a n d d u s t p a r

t i c l e s , w h i c h m a y c l o g t h e n a r r o w a i r p a s s a g e s i n t h e smallestbronchioles. Coarse hairs found just inside the nostrils of the nose trap

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airborne particles as they are inhaled. The particles drop down onto the mucous

membraneliningt h e n a s a l p a s s a g e s . T h e c i l i a e m b e d d e d i n t h e m u c o u s

m e m b r a n e w a v e c o n s t a n t l y , creating a current of mucus that propels the

particles out of the nose or downward to the p harynx. In the pharynx, themucus is swallowed and passed to the stomach, where the particles

are destroyed by stomach acid. If more particles are in the nasalpassages thant h e c i l i a c a n h a n d l e , t h e p a r t i c l e s b u i l d u p o n

t h e m u c u s a n d i r r i t a t e t h e m e m b r a n e beneath it. This irritationtriggers a reflex that produces a sneeze to get rid of the pollutedair.The nasal

passages also moisten and warm air to prevent it from damaging

thedelicate membranes of the lung. The mucous membranes of thenasal passages releasewater vapor, which moistens the air as

it pass es over the membra nes. As a ir moves over the extensive

capillaries in the nasal passages, it is warmed by the blood in the capillaries.

If the nose is blocked or stuf fy due to a cold or allergies, a pe rson

is fo rced to breaththrough the mouth. This can be potentially harmful to the

respiratory system membranes,since the mouth does not filter, warm, or moistenair.In addition to their role in the respir atory system, the nasal

passages house cellscalled olfactory receptors, which are involved

in the sense of smell . When chemic al senter the nasal passages, they contactthe olfactory receptors. This triggers the receptorsto send a signal to the brain,

which creates the perception of smell.B. PharynxAir leaves the nasal passages and flows to the pharynx, a short,

funnel-shapedtube about 13 cm (5 in) long that transports air to the larynx. Likethe nasal passages, the p h a r y n x i s l i n e d w i t h a p r o t e c t i v e mu c o u s

m e m b r a n e a n d c i l i a t e d c e l l s t h a t r e m o v e i mp uri ti es fro m t he

air. In addition to serving as an air passage, the pharynx houses

thetonsils, lymphatic tissues that contain white blood cells. The white blood cellsattack anydisease- causi ng o rgani sms th at es cape the hairs , cili a, an d

mucus of the nasal

passagesa n d p h a r y n x . T h e t o n s i l s a r e s t r a t e g i c a l l y l o c a t e d to p r ev en t t h e s e o r ga n i s m s f r om movi ng fu rt he r i nt o t he body.

One tonsil , called the adenoids, is found high in the rear wall of the

pharynx. A pair of tonsils, the palatine tonsils , is located at the backof the pharynx on either side of the tongue. Another pair , the lingual

tonsil s, is found de ep in the pharynx at the base of the tongue. In their battleswith disease-causing organisms, thetonsils sometimes

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become swollen with infection. When the adenoids are swollen,

they block the flow of air from the nasal passages to the pharynx,and a pe rso n mus t br eathe through the mouth

C. LarynxA i r m o v e s f r o m t h e p h a r y n x t o t h e l a r y n x , a s t r u c t u r e

a b o u t 5 c m ( 2 i n ) l o n g located approximately in the middle of the neck.Several layers of cartilage, a tough andf l e x i b l e t i s s u e , c o m p r i s e m o s t

o f t h e l a r y n x . A p r o t r u s i o n i n t h e c a r t i l a g e c a l l e dt h e Adams apple sometimes enlarges in males during puberty,

cre ati ng a promi nent bu lg evisible on the neck.While the primary role of the

larynx is to transport air to the trachea, it also servesother functions. It plays aprimary role in producing sound; it prevents food and fluidfrom

entering the air passage to cause choking; and its mucous

membranes and cilia- bearing cells help fil ter air . The cilia in thela rynx waf t airborne par tic les up toward the pharynx to be swallowedFood and fluids from the pharynx usually are prevented from entering the

larynxby the epiglottis, a thin, leaflike tissue. The stem ofthe leaf attaches to the

front and topof the larynx. When a person is breathing, the epiglottis is held in avertical position, likean open trap door. When a person swallows, however, a

reflex causes the larynx and theepig lo tt is to move toward each ot he r,

formi ng a p rotec tive seal , and food and fluid s a re routed to thees ophagus . I f a pe r s on i s ea t i ng o r d r i nk i ng t oo r ap i d l y , o r

l a ug hs wh i l e s w a l l o wi ng , t h e s wa ll owing re fl ex may not work ,

and food or fluid can enter the larynx. Food, fluid, or othersubstances in the larynx initiate a cough reflex as the body attempts

to clear thelarynx of the obstruction. If the cough reflex does notwork, a person can choke, a life-30

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t h r e a t e n i n g s i t u a t i o n . T h e H e i m l i c h m a n e u v e r i s a

t e ch n i qu e u s ed t o c l ea r a b l oc ke d l ar ynx ( see F ir st Ai d) . Asurgical procedure c alled a tracheotomy i s used to bypass thelarynx

and get air to the trachea in extreme cases of chokin

t h r e a t e n i n g s i t u a t i o n . T h e H e i m l i c h m a n e u v e r i s at e ch n i qu e u s ed t o c l ea r a b l oc ke d l ar ynx ( see F ir st Ai d) . A

surgical procedure c alled a tracheotomy i s used to bypass the larynxand get air to the trachea in extreme cases of choking.D. Trachea, Bronchi, and BronchiolesAir passes from the larynx into the trachea, a tube about 12 to 15 cm (about 5 to

6in) long located just below the larynx. The trachea is formed of 15 to 20 C-shapedringsof cartilage. The sturdy cartilage rings hold the trachea open, enabling air to

pass freely atall times. The open part of the C-shaped cartilage lies at the back ofthe trachea, and theends of the C are connected by muscle tissue.The base of the

trachea is located a little below where the neck meets the trunk of th e body.

Here the trachea branches into two tubes, the left and right bronchi,

whichdeliver air to the left and right lungs, respectively. Within

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the lungs, the bronchi branchinto smaller tubes called bronchioles. The

trachea, bronchi, and the first few bronchiolesontribute to the cleansing function of the respiratory system, for they, too, are lined

withmucous membranes and ciliated cells that move mucus upward to the pharynx.E. AlveoliThe bronchioles divide many more times in the lungs to create an impressive

treewith smalle r and s maller bran ches, some no la rger than 0.5 mm(0.02 in) in diameter.These branches dead-end into tiny air sacs

called alveoli. The alveoli deliver oxygen tothe circulatory systemand remove carbon dioxide. Interspersed among the alveoli

arenumerous macrophages, large white blood cells that patrol the alveoli and

remove foreignsubstances that have not been filtered out earlier. Themacrophages are the last line

of d e f e n s e o f t h e r e s p i r a t o r y s y s t e m ; t h e i r p r e s e n c e h e l p s e

n s u r e t h a t t h e a l v e o l i a r e protected from infection so that they can carryout their vital role

Human LungsThough the right lung has three lobes, the left lung, with a cleft to

accommodatethe heart, has only two. The two branches of the trachea, called

bronchi, subdivide withinhe lobes into smaller and smaller air vessels. They

terminate in alveoli, tiny air sacssurrounded by capillaries. When the alveoli inflate

with inhaled air, oxygen diffuses intothe blood in the capillaries to be pumped by

the heart to the tissues of the body, andcarbon dioxide diffuses out of the blood

into the lungs, where it is exhaled.The alveol i nu mber abou t 150 mi ll ionper lung and comprise most of the lung tissue. Alveoli resemble tiny,

collapsed balloons with thin elastic walls that expand as air flows into them

and collapse when the air is exhaled. Alveoli are arranged in

grapelikeclusters, and each cluster is surrounded by a dense hairnet of tiny, thin-

walled capillaries.The alveoli and capillaries are arranged in such a way that air in

the wall of the alveoli isonly about 0.1 to 0.2 microns from the blood in the

capillary. Since the concentration of oxygen is much higher in the alveoli than in

the capillaries, the oxygen diffuses from thealveo li to th e cap il la ri es. The

oxygen flows t hrough the capi llari es to larger vesse ls, which carry the

oxygenated blood to the heart, where it is pumped to the rest of the body.Carbon

dioxide that has been dumped into the bloodstream as a waste

productfrom cells throughout the body flows through the

bloodstream to the heart, and then tothe alveolar capillaries. The

concentration of carbon dioxide in the capillaries is muchhigher

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than in the alveoli , causing carbon dioxide to diffuse into th e

alveoli . Exhalat ionforces the carbon dioxide back through the respiratory

passages and then to the outside of the body.

III. RegulationThe flow of air in and out of the lungs is controlled by the nervous system,whichensures that humans breathe in a regular pattern and at a regular rate.

Breathing is carried33

out day and night by an unconscious process. It begins with a cluster of nerve cells

in the brain stem ca lled t he respi ratory cen ter. These cell s send

simultan eous signals to th ediaphragm and rib muscles, the muscles involvedin inhalation. The diaphragm is a large,dome-shaped muscle that lies just under the

lungs. When the diaphragm is stimulated bya nervous impulse, it flattens.

The downward movement of the diaphragm expands thevolume ofthe cavity that contains the lungs, the thoracic cavity. When the rib

musclesare stimulated, they also contract, pulling the rib cage up and out like thehandle of a pail.Thi s movement a lso expand s th e thor aci c cavi ty. The

increased volume of the thoraciccavity causes air to rush into thelungs. The nervous stimulation is brief, and when

itc e a s e s , t h e d i a p h r a g m a n d r i bm u s c l e s r e l a x a n d e x h a l a t i o n o c c u r s . U n d e r n o r m a l conditions,

the respiratory center emits signals 12 to 20 times a minute, causing a personto

t a k e 1 2 t o 2 0 b r e a t h s a m i n u t e . N e w b o r n s b r e a t h e a t af a s t e r r a t e , a b o u t 3 0 t o 5 0 breaths a minute.The rhythm set by therespiratory center can be altered by conscious control. The breathing pattern

changes when a person sings or wh istles, for example. A personalsocan alter the breathing pattern by holding the breath.

The cerebra l cor tex, the par t o f the b ra in in vo lv ed in th in k i ng ,c a n s e n d s i g n a l s t o t h e d i a p h r a g m a n d r i b m u s c l e s

t h a t temporarily override the signals from the respiratory center.The ability to hold ones b r e a t h h a s s u r v i v a l v a l u e . I f a

p e r s o n e n c o u n t e r s n o x i o u s f u m e s , f o r e x a m p l e , i t i s possible

to avoid inhaling thefumes.A perso n c annot hold th e brea th in definitely, however. If exh alation does noto c c u r , c a r b o n d i o x i d e a c c u m u l a t e s i n t h e

b l o o d , w h i c h , i n t u r n , c a u s e s t h e b l o o dt o b e c o m e m o r e a c i d i c . I n c r e a s e d a c i d i t y i n t e r f e r e s w i t h t h

e a c t i o n o f e n z y m e s , t h e 34

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specialized proteins that participate in virtually all biochemical reaction in the

body. To prevent the blood from becoming too acidic, the blood is monitored byspecial receptorscalled chemoreceptors, located in the brainstem and in

the blood vessels of the neck. If acid builds up in the blood, the

chemoreceptor s send nervo us signal s t o t he respi rator ycenter, whichoverrides the signals from the cerebral cortex and causes a person to exhaleand

then resume breathing. These exhalations expel the carbon dioxideand br ing the blood acid level back to normal.A per son can exer t so me

degree of control over the amount of air inhaled, withsome limitations.To prevent the lungs from bursting from overinflation, specialized cellsin the

lungs called stretch receptors measure the volume of air in the

lungs. When thevolume reaches an unsafe threshold, the stretch receptors sendsignals to the respiratorycenter, which shuts down the muscles of inhalation and

halts the intake of air

As the diaphragm contracts and moves downward, the pectoralisminor and int ercostalmuscles pull the rib cage outward. The chest cavity

expands, and air rushes into the lungst h r o u g h t h e t r a c h e a t o f i l l t h e

r e s u l t i n g v a c u u m . W h e n t h e d i a p h r a g m r e l a x e s t o i t s normal,

upwardly curving position, the lungs contract, and air is forced out

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ANATOMY AND PHYSIOLOGY

Respiration is essential to all living things because all of the living cells in the body

need adequate oxygenation and produces carbon dioxide. Respiratory System, in

anatomy and physiology, comprises of organs that deliver oxygen to the

circulatory system for transport to all body cells. Oxygen is

essential for cells, which use this vital substance to liberate the energy needed

for cellular activities. T h e r e s p i r a t o r y s y s t e m b r i n g s oxygen

through the airways of lungs into the alveoli, where it diffuses into

the blood for transport to the tissue, this process is so vital that

diff icult inbreathing is expected as a threat to life in self. The respiratory system

allows oxygen from the air to enter the blood and carbon dioxide to leave the

blood and enter the air. The cardiovascular system transport oxygen from the

lungs to the cells of the body and carbon dioxide. Without healthy respiratory and

cardiovascular system, the capacity to carry out normal activity is

reduced,and without adequate respiratory and cardiovascular system

fr ic ti on , li fe itself is possible.

II. Structure

The organs of the respiratory system extend from the nose to the

lungs and are divided into the upper and lower respiratory tracts. The upper

respiratory tract consists of th e no se an d th e ph ar yn x, or th ro at . Th e

lower respiratory tract includes the larynx, or voice box; the trachea, or

windpipe, which splits into two main branches called bronchi, tiny branches ofthe bronchi called bronchioles; and the lungs, a pair of saclike,

spongy organs. The nose, pharynx, larynx, trachea, bronchi, and

bronchioles conduct air to and from the lungs. The lungs interact

with the circulatory system to deliver oxygen and remove carbon

dioxide.