CP Acute Renal Failure chap5

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CHAPTER V

ANATOMY AND PHYSIOLOGY

This chapter will discuss the anatomy and physiology of the

digestive system which it is the affected system of the disease.

URINARY SYSTEM

The kidneys are essentially regulatory organs which maintain the

volume and composition of body fluid by filtration of the blood and

selective reabsorption or secretion of filtered solutes.

The kidneys are retroperitoneal organs (ie located behind the

peritoneum) situated on the posterior wall of the abdomen on each side of

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the vertebral column, at about the level of the twelfth rib. The left kidney is

slightly higher in the abdomen than the right, due to the presence of the

liver pushing the right kidney down.

The kidneys take their blood supply directly from the aorta via the renal

arteries; blood is returned to the inferior vena cava via the renal veins.

Urine (the filtered product containing waste materials and water) excreted

from the kidneys passes down the fibromuscular ureters and collects in

the bladder. The bladder muscle (the detrusor muscle) is capable of

distending to accept urine without increasing the pressure inside; this

means that large volumes can be collected (!!"#!!!ml) without high"

pressure damage to the renal system occuring.

$hen urine is passed, the urethral sphincter at the base of the bladder

relaxes, the detrusor contracts, and urine is voided via the urethra.

Function of the Kidne!

The kidneys form urine to excrete waste products such as urea,

ammonia, and creatinine before they could accumulate to toxic levels. %t

also functions to regulate the volume of blood by either excreting or

conserving water, controlling electrolyte balances by regulating the

minerals, regulating acid"base balance and also regulation of the blood

volume, electrolytes and acid"base balance in the tissue fluids.

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St"uctu"e of the #idne

The kidneys are a pair of bean"shaped, brownish red structures

located in the upper abdominal cavity on either side of the vertebral

column, behind the peritoneum (retroperitoneal). The average adult kidney

weighs approximately ##& to #! g (about '. o) am dos #! to #* cm

long, + cm wide, and *. thick. The right kidney is slightly lower than the

left due to the location of the liver. The upper portions of the kidneys rest

on the lower surface of the diaphragm and are enclosed by the lower rib

cage. The kidneys are embedded in adipose tissue that acts as a cushion

and is in turn covered by a fibrous connective tissue membrane called the

renal fascia, which helps to hold the kidneys in place.

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renal pyramids into the calyses, then to the renal pelvis and out into the

ureter.

St"uctu"e of the ne&h"on

%t is the structural and functional unit of the kidney. ach kidney

contains approximately # million nephrons. %t is in nephrons, with their

associated blood vessels, that urine is formed. ach nephron has two

ma0or portions1 renal corpuscle and renal tubule.

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Ren$% co"&u!c%e

%t consists of a glomerulus surrounded by a 2owman3s capsule. The

glumerulus is a capillary network that arises from an afferent arteriole and

empties into an efferent arteriole. The diameter of the efferent arteriole is

smaller than that of the afferent arteriole, which helps maintain a fairly high

blood pressure in the glumerulus.

2owman3s capsule (or glumerular capsule) is the expanded end of

the renal tubule; it encloses the glomerulus. The inner layer of the

2owman3s capsule is made pf podocytes; the name means 4foot cells5 and

the 4feet5 of the podocytes are on the surface of the glumerular capillaries.

The arrangement of podocytes creates pores, spaces between ad0acent

4feet5, which make this layer very permeable. The outer layer of the

2owman3s capsule has no pores and is not permeable. The space

between the inner and outer layers of the 2owman3s capsule contains

renal filtrate, the fluid that is formed from the blood in the glomerulus and

will eventually become urine.

Ren$% Tu'u%e

The renal tubule continues from 2owman3s capsule and consists of

the following parts1 proximal convoluted tubule (in the renal cortex), loop of

enle (or the loop of nephron, in the renal medulla) and the distal

convoluted tubules from several nephrons empty into a collecting tubule.

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6everal collecting tubules then unite to form a papillary duct that empties

urine into calyx of the renal pelvis.

-ll parts of the renal tubule are surrounded by the peritubular

capillaries, which arise from the efferent arteriole. The peritubular

capillaries will receive the materials reabsorbed by the renal tubules.

(%ood )e!!e%! of the #idne

The pathway of blood flow through the kidney is an essential part of

the process of urine formation. 2lood from the abdominal aorta enters the

renal artery, which branches extensively within the kidney into smaller

arteries. The smallest arteries give rise to afferent arterioles in the renal

cortex. /rom the different arterioles, blood flows into the glomeruli

(capillaries), to efferent arterioles, to peritubular capillaries, to veins within

the kidney, to the renal vein, and finally to the inferior vena cave.

%n this pathway there are two sets of capillaries and that it is in

capillaries that exchanges take place between blood and the surrounding

tissues. Therefore, in the kidneys there are two sites of exchange. The

exchanges that take place between the nephrons and the capillaries of the

kidneys will form urine from blood plasma.

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U"ete"!

ach ureter extends from the hilus of a kidney to the lower,

posterior side of the urinary bladder. 7ike the kidneys. The ureters are

retroperitoneal, that is behind the peritoneum of the dorsal abdominal

cavity.

The wall of the ureter is composed of smooth muscles which

contracts in peristaltic waves to propel urine toward the urinary bladder. -s

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the bladder fills, it expands and compresses the lower ends of the ureters

to prevent backflow of urine.

U"in$" '%$dde"

%t is a muscular sac below the peritoneum and behind the pubic

bones. %n women, the bladder is inferior to the uterus; in men, the bladder

is superior to the prostate gland. The bladder is a reservoir for

accumulating urine, and it contracts to eliminate urine.

The mucosa of the bladder is transitional epithelium, which permits

expansion without tearing the lining. $hen the bladder is empty, the

mucosa appears wrinkled; these folds are rugae, which also permit

expansion. 8n the floor of the bladder is a triangular area called trigone,

which has no rugae and does no expand. The points of the triangle are the

openings of the two ureters and that of the urethra.

The smooth muscle layer in the wall of the bladder is called

detrusor muscle. %t is a muscle in the form of sphere; when it contracts it

becomes a smaller sphere, and its volume diminishes. -round the opening

of the urethra the muscle fibers of the detrusor form the opening of the

internal urethral sphincter (or sphincter of the bladder), which is

involuntary.

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U"in$" Fo"+$tion

The healthy human body is composed of approximately +!: of

water. $ater balance is regulated by the kidneys and results in the

formation of urine. Urine is formed in the nephrons through a complex

three"step process1 glomerular filtration, tubular reabsorption and tubular

secretion. The various substances normally filtered by the glomerulus,

reabsorbed by the tubules, and excreted in the urine include sodium,

chloride, bicarbonate, potassium, glucose, urea, creatinine, and uric acid.

$ithin the tubule, some of these substances are selectively reabsorbed

into the blood into the filtrate as it travels down the tubule.

G%o+e"u%$" Fi%t"$tion

The normal blood flow through the kidneys is about #*!! mlmin.

-s blood flows into the glomerulus from an afferent arteriole, filtration

occurs. The filtrated fluid, also known as filtrate or ultrafiltrate, then enters

the renal tubules. Under normal condition, about *!: of the blood passing

through the glomeruli is filtered into the nephron, amounting to about #9!

7day of filtrate. The filtrate normally consists of water, electrolytes, and

other small molecules are allowed to pass, whereas larger molecules stay

in the bloodstream.


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The second and third steps of urine formation occur in the renal

tubules. %n tubular reabsorption, a substance moves from the filtrate back

into the peritubular capillaries or vasa recta. %n tubular secretion, a

substance moves from the peritubular capillaries or vasa recta into tubular

filtrate. 8f the #9! 7 of filtrate that the kidneys produce each day, ==: is

reabsorbed into the bloodstream, resulting the formation of # 7 to * 7 of

urine each day. -lthough most reabsorption occurs in proximal tubules,

reabsorption occurs along the entire tubule. >eabsorption and secretion in

the tubule fre?uently involve passive and active transport and may re?uire

the use of energy. /iltrate becomes concentrated in the distal tubule and

collecting ducts under hormonal influence and becomes urine, which then

enters the renal pelvis.

THE HUMAN DIGESTIVE SYSTEM

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The digestive system consists of the digestive tract, a tube

extending from the mouth to anus. The functions of the @% tract include

secretion, digestion, absorption, motility, and elimination. /oods and fluids

are ingested, swallowed, and propelled along the lumen of the @% tract to

the anus for elimination.

O"$% c$)it

The

mouth or oral cavity is the first part of the digestive tract. %t includes the

buccal mucosa, lips, tongue, hard palate, soft palate, teeth and salivary

glands.

The different types of teeth function to prepare for digestion by

cutting, tearing, crushing, or grinding the food. 6wallowing begins after

food is taken into the mouth and chewed. 6aliva secreted in response to

the presence of food in the mouth and begins to soften the food. 6aliva

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contains mucin and an enyme called salivary amylase, which begins the

breakdown of carbohydrates.

Ph$"n,

The pharynx or throat, which connects the mouth with the

esophagus, consists of three parts1 the nasopharynx, oropharynx, and

laryngopharynx.

E!o&h$*u!

The esophagus is a muscular tube, lined with moist stratified

s?uamous epithelium that extends from the pharynx to the stomach. %t

transports food from the pharynx to the stomach. -t the upper end of the

esophagus is a sphincter referred to as the upper esophageal sphincter.

$hen at rest, the U6 is closed to prevent air into the esophagus during

respiration. The portion of the esophagus proximal to the

gastroesophageal 0unction is referred to as the lower esophageal

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sphincter. $hen at rest, the 76 is normally closed to prevent reflux of

gastric contents to the esophagus.

Sto+$ch

The stomach is a glandular digestive and endocrine organ located

in the midline and left upper ?uadrant of the abdomen. The surface of the

stomach is covered with rugae, or folds of mucosa and submucosa that

extend longitudinally. 6mooth muscle cells that line the stomach are

responsible for gastric motility. Aarietal cells lining the wall of the stomach

secrete hydrochloric acid, whereas chief cells secret pepsinogen.

The stomach performs several functions. /ollowing the ingestion of

the food, the stomach functions as a food reservoir. The primary function

of the stomach is to begin the digestive process by using both mechanical

movements and chemical secretions. The stomach also mixes or churns

the food, breaking apart the large molecules and mixing them with gastric

secretions to form chimes which the empties into the duodenum.

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wall of the gallbladder, which forces bile into the cystic duct then into the

common bile duct, and on into the duodenum.

S+$%% inte!tine

The small intestine is the site where most of the chemical and

mechanical digestion is carried out, and where virtually all of the

absorption of useful materials is carried out. The whole of the small

intestine is lined with an absorptive mucosal type, with certain

modifications for each section. The intestine also has a smooth muscle

wall with two layers of muscle; rhythmical contractions force products of

digestion through the intestine (peristalisis). There are three main sections

to the small intestine;

The duodenum forms a BCB shape around the head of the pancreas.

%ts main function is to neutralie the acidic gastric contents (called

BchymeB) and to initiate further digestion; Brunners glandsin the

submucosa secrete alkaline mucus which neutralises the chyme

and protects the surface of the duodenum.

The 0e0unum and the ileum. The 0e0unum and the ileum are the

greatly coiled parts of the small intestine, and together are about '"

+ metres long; the 0unction between the two sections is not well"

defined. The mucosa of these sections is highly folded (the folds

are calledplicae), increasing the surface area available for

absorption dramatically.

L$"*e inte!tine

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2y the time digestive products reach the large intestine, almost all

of the nutritionally useful products have been removed. The large intestine

removes water from the remainder, passing semi"solid feces into the

rectum to be expelled from the body through the anus. The mucosa (


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The rectum has little shelves in it called transverse folds. These

folds help keep stool in place until you3re ready to go to the bathroom.

$hen you3re ready, stool enters the lower rectum, moves into the anal

canal, and then passes through the anus on its way out. The rectum

intestine acts as a temporary storage facility for feces. -s the rectal walls

expand due to the materials filling it from within, stretch receptors from the

nervous system located in the rectal walls stimulate the desire to defecate.

%f the urge is not acted upon, the material in the rectum is often returned to

the colon where more water is absorbed. %f defecation is delayed for a

prolonged period of time constipationand hardened feces results. $hen

the rectum becomes full, the increase in intrarectal pressure forces the

walls of the anal canal apart, allowing the fecal matter to enter the canal.

The rectum shortens as material is forced into the anal canal and

peristaltic waves propel the feces out of the rectum. The internal and

external sphincter allows the feces to be passed by muscles pulling the

anus up over the exiting feces.

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CARDIOVASCULAR SYSTEM

-de?uate perfusion oxygenates and nourishes body tissues and

depends in part on a properly functioning cardiovascular system.

-de?uate blood flow depends on the efficient pumping action of the heart,

patent and responsive blood vessels and ade?uate circulating blood

volume. The cardiovascular system involves the heart, blood vessels and

blood.

HEART

The heart is a hollow muscular organ located in the center of the

thorax, where it occupies the space between the lungs and the rests on

the diaphragm. The heart is composed of three layers; the inner layer or

endocardium, consists of endothelial tissue and lines the inside of the

heart and valves. The middle layer or myocardium is made up of muscle

fibers and is responsible for the pumping action. The exterior layer of the

heart is the epicardium.

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The heart pumps blood to the tissues, supplying them with oxygen

and other nutrients. The pumping action of the heart is accomplished by

the rhythmic contraction and relaxation of its muscular wall. During systole

(contraction of the muscle). The chambers of the heart become smaller as

the blood is e0ected. During diastole (relaxation of the muscle), the heart

chambers fill with blood in preparation of subse?uent e0ection. ach

ventricle e0ects approximately ! m7 of blood per beat and has an output

of approximately 7 per minute.

HEART CHAMBERS

The four chambers of the heart constitute the right and left side

pumping systems. The right side of the heart, made up of the right atrium

and right ventricle, distributes venous blood (deoxygenated blood) to the

lungs via the pulmonary artery (pulmonary circulation) for oxygenation.

The right atrium receives blood returning from the superior vena cava,

inferior vena cava and coronary sinus.

The left side of the heart, composed of the left atrium and ventricle,

distributes oxygenated blood to the remainder of the body via the aorta

(systemic circulation). The left atrium receives oxygenated blood from the

pulmonary circulation via the pulmonary veins.

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HEART VALVES

The four valves in the heart permit blood to flow in only one

direction. The valves which are composed of thin leaflets of fibrous tissue,

open and close in response to the movement of blood and pressure

changes within the chambers.

-trioventricular valves separate the atria from the ventricles; there

are * atrioventricular valves which are the tricuspid and bicuspid valves.

Tricuspid valve is composed of three cusps or leaflets, separates the right

atrium from the right ventricle. The mitral or bicuspid valve, lies between

the left atrium and left ventricle.

6emilunar valves are composed of three half"moon"like leaflets.

The valve between the right ventricle and the pulmonary artery is called

the pulmonic valve; while the valve between the left ventricle and the aorta

is called the aortic valve.

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ARTERIES AND ARTERIOLES

-rteries are thick"walled structures that carry blood from the heart

to the tissues. The aorta, which has a diameter of approximately *mm (%

inch), gives rise to numerous branches which divide into smaller arteries

that are about ' mm in diameter. The walls of the arteries and arterioles

are composed of three layers1 the intima, an inner endothelial cell layer,

the media, a middle layer of smooth elastic tissue; and the adventitia, an

outer layer of connective tissue.

-rteries distribute oxygenated blood from the left side of the heart

to the tissues, whereas the veins carry deoxygenated blood from the

tissues to the right side of the heart.

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CAPILLARIES

Capillaries are composed of a single layer of endothelial cells. This

thin"walled structure permits rapid and efficient transport of nutrients to the

cells and removal of metabolic wastes. Capillary vessels, located within

the tissues, connect the arterial and venous systems and are the site of

exchange of nutrients and metabolic wastes between the circulatory

system and the tissues.

VEINS AND VENULES

Capillaries 0oin to form larger vessels called venules, which 0oin to

form veins. The venous system is therefore structurally analogous to the

arterial system; venous correspond to arterioles. The walls of the veins, in

contrast to those of the arteries are thinner and considerably less

muscular.

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LYMPHATIC VESSELS

7ymphatic vessels are a complex network of thin"walled vessels

similar to the blood capillaries. This network collects lymphatic fluid from

tissues and organs and transports the fluid to the venous circulation. The

lymphatic system complements the function of the circulatory system.

7ymphatic vessels transport lymph and tissue fluids from the interstitial

space to systemic veins.

BLOOD

The cellular component of blood consists of three primary cell

types1 >2C3s, $2C3s and platelets. Circulating through the vascular

system and serving as a link between body organs, the blood carries

oxygen absorbed from the lungs and nutrients absorbed from the

gastrointestinal tract to the body cells for cellular metabolism. 2lood also

carries waste products produced by cellular metabolism to the lungs, skin,

liver and kidneys, where they are transformed and eliminated from the

body. 2lood also carries hormones, antibodies and other substances to

their sites of action or use.

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An$to+ of Re!&i"$to" S!te+

The >espiratory 6ystem is crucial to every human being. $ithout it, we

would cease to live outside of the womb.

>espiration is the act of breathing1

inhaling (inspiration) " taking in oxygen

exhaling (expiration) " giving off carbon dioxide

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The respiratory system is made up of the organs involved in breathing and

consists of the1

nose

pharynx

larynx

trachea

bronchi

lungs

The upper respiratory tract includes the1

nose

nasal cavity

ethmoidal air cells

frontal sinuses

maxillary sinus

larynx

trachea

The lower respiratory tract includes the1

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lungs

bronchi

alveoli

The lungs take in oxygen, which all cells throughout the body need to

live and carry out their normal functions. The lungs also get rid of carbon

dioxide, a waste product of the bodyBs cells.

The lungs are a pair of cone"shaped organs made up of spongy,

pinkish"gray tissue. They take up most of the space in the chest, or the

thorax (the part of the body between the base of the neck and diaphragm).

The lungs are inside in a membrane called the &%eu"$.

The lungs are separated from each other by the +edi$!tinu+, an area

that contains the following1

heart and its large vessels

trachea (windpipe)

esophagus

thymus

lymph nodes

The right lung has three sections, called %o'e!. The left lung has two

lobes. $hen you breathe, the air1

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enters the body through the nose or the mouth

travels down the throat through the %$"n,(voice box) and t"$che$

(windpipe)

goes into the lungs through tubes called main"stem '"onchi

o one main"stem bronchus leads to the right lung and one to

the left lung

o in the lungs, the main"stem bronchi divide into !+$%%e"

'"onchi

o and then into even smaller tubes called '"onchio%e!

o bronchioles end in tiny air sacs called $%)eo%i

Ph!io%o* of Re!&i"$to" S!te+

Function!

The function of the respiratory system is to give us a surface area for

exchanging gases between the air and our circulating blood. %t moves that

air to and from the surfaces of the lungs while it protects the lungs from

dehydration, temperature changes and unwelcome pathogens. %t also

plays a part in making sounds such as talking, singing, other nonverbal

sounds and works with the central nervous system for the ability to smell.

The four processes of respiration1

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#. (REATHINGor ventilation

*. E-TERNAL RESPIRATION, which is the exchange of gases

(oxygen and carbon dioxide) between inhaled air and the blood.

&. INTERNAL RESPIRATION, which is the exchange of gases

between the blood and tissue fluids.

./ CELLULAR RESPIRATION

The main processes, the respiratory system serves for1

REGULATION OF (LOOD &H, which occurs in coordination with

the kidneys, and as a

D/E6 -@-%E6T 826

Cont"o% of 'od te+&e"$tu"e due to loss of evaporate during

expiration

("e$thin* $nd Lun* Mech$nic!

Venti%$tionis the exchange of air between the external environment and

the alveoli. -ir moves by bulk flow from an area of high pressure to low

pressure. -ll pressures in the respiratory system are relative to

atmospheric pressure (+!mmg at sea level). -ir will move in or out of

the lungs depending on the pressure in the alveoli. The body changes the

pressure in the alveoli by changing the volume of the lungs. -s volume

increases pressure decreases and as volume decreases pressure

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increases. There are two phases of ventilation; inspiration and expiration.

During each phase the body changes the lung dimensions to produce a

flow of air either in or out of the lungs.

The body is able to stay at the dimensions of the lungs because of the

relationship of the lungs to the thoracic wall. ach lung is completely

enclosed in a sac called the pleural sac. Two structures contribute to the

formation of this sac. The parietal pleura is attached to the thoracic wall

where as the visceral pleura is attached to the lung itself. %n"between

these two membranes is a thin layer of intrapleural fluid. The intrapleural

fluid completely surrounds the lungs and lubricates the two surfaces so

that they can slide across each other. Changing the pressure of this fluid

also allows the lungs and the thoracic wall to move together during normal

breathing.


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>elaxed exhalation occurs between impulses when the muscles relax.

Eormal adults have a breathing rate of #*"*! respirations per minute.

The P$th0$ of Ai"

$hen one breathes air in at sea level, the inhalation is composed of

different gases. These gases and their ?uantities are 8xygen which

makes up *#:, Eitrogen which is 9:, Carbon Dioxide with !.!': and

others with significantly smaller portions.

Diagram of the Ph$"n,.

%n the process of breathing, air enters into the nasal cavity through the

nostrils and is filtered by coarse hairs ()i'"i!!$e) and mucous that are

found there. The vibrissae filter macroparticles, which are particles of large

sie. Dust, pollen, smoke, and fine particles are trapped in the mucous

that lines the n$!$% c$)itie!(hollow spaces within the bones of the skull

that warm, moisten, and filter the air). There are three bony pro0ections

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inside the nasal cavity. The !u&e"io"1 +idd%e1 $nd infe"io" n$!$%

conch$e. -ir passes between these conchae via the nasal meatuses.

-ir then travels past the nasopharynx, oropharynx, and laryngopharynx,

which are the three portions that make up the pharynx. The &h$"n,is a

funnel"shaped tube that connects our nasal and oral cavities to the larynx.

The ton!i%!which are part of the lymphatic system, form a ring at the

connection of the oral cavity and the pharynx. ere, they protect against

foreign invasion of antigens. Therefore the respiratory tract aids the

immune system through this protection. Then the air travels through the

%$"n,. The larynx closes at the epiglottis to prevent the passage of food

or drink as a protection to our trachea and lungs. The larynx is also our

voicebox; it contains vocal cords, in which it produces sound. 6ound is

produced from the vibration of the vocal cords when air passes through

them.

The t"$che$, which is also known as our windpipe, has ciliated cells and

mucous secreting cells lining it, and is held open by C"shaped cartilage

rings. 8ne of its functions is similar to the larynx and nasal cavity, by way

of protection from dust and other particles. The dust will adhere to the

sticky mucous and the cilia helps propel it back up the trachea, to where it

is either swallowed or coughed up. The +ucoci%i$" e!c$%$to" extends

from the top of the trachea all the way down to the '"onchio%e!, which we

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will discuss later. Through the trachea, the air is now able to pass into the

bronchi.

In!&i"$tion

In!&i"$tion i! initi$ted ' cont"$ction of the di$&h"$*+and in some

cases the intercostals muscles when they receive nervous impulses.

During normal ?uiet breathing, the &h"enic ne")e! !ti+u%$te the

di$&h"$*+ to cont"$ct $nd +o)e do0n0$"d into the $'do+en. This

downward movement of the diaphragm enlarges the thorax. $hen

necessary, the intercostal muscles also increase the thorax by contacting

and drawing the ribs upward and outward.

-s the diaphragm contracts inferiorly and thoracic muscles pull the chest

wall outwardly, the volume of the thoracic cavity increases. The lungs are

held to the thoracic wall by negative pressure in the pleural cavity, a very

thin space filled with a few milliliters of lubricating pleural fluid. The

negative pressure in the pleural cavity is enough to hold the lungs open in

spite of the inherent elasticity of the tissue. ence, as the thoracic cavity

increases in volume the lungs are pulled from all sides to expand, causing

a drop in the pressure (a partial vacuum) within the lung itself (but note

that this negative pressure is still not as great as the negative pressure

within the pleural cavity""otherwise the lungs would pull away from the

chest wall). -ssuming the airway is open, air from the external

environment then follows its pressure gradient down and expands the

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alveoli of the lungs, where gas exchange with the blood takes place. -s

long as pressure within the alveoli is lower than atmospheric pressure air

will continue to move inwardly, but as soon as the pressure is stabilied air

movement stops.

E,&i"$tion

During ?uiet breathing, expiration is normally a passive process and does

not re?uire muscles to work (rather it is the result of the muscles relaxing).

$hen the lungs are stretched and expanded, stretch receptors within the

alveoli send inhibitory nerve impulses to the medulla oblongata, causing it

to stop sending signals to the rib cage and diaphragm to contract. The

muscles of respiration and the lungs themselves are elastic, so when the

diaphragm and intercostal muscles relax there is an elastic recoil, which

creates a positive pressure (pressure in the lungs becomes greater than

atmospheric pressure), and air moves out of the lungs by flowing down its

pressure gradient.

-lthough the respiratory system is primarily under involuntary control, and

regulated by the medulla oblongata, we have some voluntary control over

it also. This is due to the higher brain function of the cerebral cortex.

$hen under physical or emotional stress, more fre?uent and deep

breathing is needed, and both inspiration and expiration will work as active

processes. -dditional muscles in the rib cage forcefully contract and push

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air ?uickly out of the lungs. %n addition to deeper breathing, when coughing

or sneeing we exhale forcibly. 8ur abdominal muscles will contract

suddenly (when there is an urge to cough or sneee), raising the

abdominal pressure. The rapid increase in pressure pushes the relaxed

diaphragm up against the pleural cavity. This causes air to be forced out of

the lungs.

-nother function of the respiratory system is to sing and to speak. 2y

exerting conscious control over our breathing and regulating flow of air

across the vocal cords we are able to create and modify sounds.

Lun* Co+&%i$nce

Lun* Co+&%i$nce is the magnitude of the change in lung volume

produced by a change in pulmonary pressure. Compliance can be

considered the opposite of stiffness. - low lung compliance would mean

that the lungs would need a greater than average change in intrapleural

pressure to change the volume of the lungs. - high lung compliance would

indicate that little pressure difference in intrapleural pressure is needed to

change the volume of the lungs.


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Dete"+in$tion of Lun* Co+&%i$nce Two ma0or things determine lung

compliance. The first is the elasticity of the lung tissue. -ny thickening of

lung tissues due to disease will decrease lung compliance. The second is

surface tensions at air water interfaces in the alveoli. The surface of the

alveoli cells is moist. The attractive force, between the water cells on the

alveoli, is called surface tension. Thus, energy is re?uired not only to

expand the tissues of the lung but also to overcome the surface tension of

the water that lines the alveoli.

To overcome the forces of surface tension, certain alveoli cells (Type %%

pneumocytes) secrete a protein and lipid complex called FF6urfactant55,

which acts like a detergent by disrupting the hydrogen bonding of water

that lines the alveoli, hence decreasing surface tension.

Cont"o% of "e!&i"$tion

Central control

Aeripheral control

C8*is converted to C8&; most C8*produced at the tissue cells is carried

to lungs in the form of C8&

C8*G *8 form carbonic acid (*C8&)

changes to C8&G H ions

result is H ions are buffered by plasma proteins

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Re!&i"$to" S!te+2 U&&e" $nd Lo0e" Re!&i"$to" T"$ct!

/or the sake of convenience, we will divide the respiratory system in to the

upper and lower respiratory tracts1

U&&e" Re!&i"$to" T"$ct

The upper respiratory tract consists of the nose and the pharynx. %ts

primary function is to receive the air from the external environment and

filter, warm, and humidify it before it reaches the delicate lungs where gas

exchange will occur.

-ir enters through the nostrils of the nose and is partially filtered by the

nose hairs, then flows into the nasal cavity. The nasal cavity is lined with

epithelial tissue, containing blood vessels, which help warm the air; and

secrete mucous, which further filters the air. The endothelial lining of the

nasal cavity also contains tiny hairlike pro0ections, called cilia. The cilia

serve to transport dust and other foreign particles, trapped in mucous, to

the back of the nasal cavity and to the pharynx. There the mucus is either

coughed out, or swallowed and digested by powerful stomach acids. -fter

passing through the nasal cavity, the air flows down the pharynx to the

larynx.

Lo0e" Re!&i"$to" T"$ct

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The lower respiratory tract starts with the larynx, and includes the trachea,

the two bronchi that branch from the trachea, and the lungs themselves.

This is where gas exchange actually takes place.

#. 7arynx

The larynx (plural larynges), collo?uially known as the voice box, is an

organ in our neck involved in protection of the trachea and sound

production. The larynx houses the vocal cords, and is situated 0ust below

where the tract of the pharynx splits into the trachea and the esophagus.

The larynx contains two important structures1 the epiglottis and the vocal

cords.

The epiglottis is a flap of cartilage located at the opening to the larynx.

During swallowing, the larynx (at the epiglottis and at the glottis) closes to

prevent swallowed material from entering the lungs; the larynx is also

pulled upwards to assist this process. 6timulation of the larynx by ingested

matter produces a strong cough reflex to protect the lungs. Eote1 choking

occurs when the epiglottis fails to cover the trachea, and food becomes

lodged in our windpipe.

The vocal cords consist of two folds of connective tissue that stretch and

vibrate when air passes through them, causing vocaliation. The length

the vocal cords are stretched determines what pitch the sound will have.

The strength of expiration from the lungs also contributes to the loudness

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of the sound. 8ur ability to have some voluntary control over the

respiratory system enables us to sing and to speak. %n order for the larynx

to function and produce sound, we need air. That is why we canBt talk

when weBre swallowing.

#. Trachea

*. 2ronchi

&. 7ungs

Ho+eo!t$!i! $nd G$! E,ch$n*e

@as exchange

omeostasis is maintained by the respiratory system in two ways1 gas

exchange and regulation of blood p. @as exchange is performed by the

lungs by eliminating carbon dioxide, a waste product given off by cellular

respiration. -s carbon dioxide exits the body, oxygen needed for cellular

respiration enters the body through the lungs. -TA, produced by cellular

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respiration, provides the energy for the body to perform many functions,

including nerve conduction and muscle contraction. 7ack of oxygen affects

brain function, sense of 0udgment, and a host of other problems.

G$! E,ch$n*e

@as exchange in the lungs and in the alveoli is between the alveolar air

and the blood in the pulmonary capillaries. This exchange is a result of

increased concentration of oxygen, and a decrease of C!*. This process

of exchange is done through diffusion.

E,te"n$% Re!&i"$tion

xternal respiration is the exchange of gas between the air in the alveoli

and the blood within the pulmonary capillaries. - normal rate of respiration

is #*"* breaths per minute. %n external respiration, gases diffuse in either

direction across the walls of the alveoli. 8xygen diffuses from the air into

the blood and carbon dioxide diffuses out of the blood into the air.


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Diagram of the %un*!

The Ri*ht P"i+$" ("onchu! is the first portion we come to, it then

branches off into the Lo'$" 4!econd$"5 ("onchi, Se*+ent$% 4te"ti$"5

("onchi, then to the ("onchio%e!which have little cartilage and are lined

by simple cuboidal epithelium (6ee fig. #). The bronchi are lined by

pseudostratified columnar epithelium. 8b0ects will likely lodge here at the

0unction of the Carina and the >ight Arimary 2ronchus because of the

vertical structure. %tems have a tendency to fall in it, where as the 7eft

Arimary 2ronchus has more of a curve to it which would make it hard to

have things lodge there.

The Left P"i+$" ("onchu!has the same setup as the right with the

lobar, segmental bronchi and the bronchioles.

The lungs are attached to the heart and trachea through structures that

are called the "oot! of the %un*!. The roots of the lungs are the bronchi,

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pulmonary vessels, bronchial vessels, lymphatic vessels, and nerves.

These structures enter and leave at the hi%u!of the lung which is Fthe

depression in the medial surface of a lung that forms the opening through

which the bronchus, blood vessels, and nerves passF (medlineplus.gov).

There are a number of te"+in$% '"onchio%e! connected to "e!&i"$to"

'"onchio%e! which then advance into the $%)eo%$" duct! that then

become $%)eo%$" !$c!. ach bronchiole terminates in an elongated space

enclosed by many air sacs called $%)eo%iwhich are surrounded by blood

capillaries. Aresent there as well, are A%)eo%$" M$c"o&h$*e!, they ingest

any microbes that reach the alveoli. The Pu%+on$" A%)eo%i are

+ic"o!co&ic, which means they can only be seen through a microscope,

membranous air sacs within the lungs. They are units of respiration and

the site of gas exchange between the respiratory and circulatory systems.

Ce%%u%$" Re!&i"$tion

/irst the oxygen must diffuse from the alveolus into the capillaries. %t is

able to do this because the capillaries are permeable to oxygen. -fter it is

in the capillary, about : will be dissolved in the blood plasma. The other

oxygen will bind to red blood cells. The red blood cells contain hemoglobin

that carries oxygen. 2lood with hemoglobin is able to transport *+ times

more oxygen than plasma without hemoglobin. 8ur bodies would have to

work much harder pumping more blood to supply our cells with oxygen

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without the help of hemoglobin. 8nce it diffuses by osmosis it combines

with the hemoglobin to form oxyhemoglobin.

Eow the blood carrying oxygen is pumped through the heart to the rest of

the body. 8xygen will travel in the blood into arteries, arterioles, and

eventually capillaries where it will be very close to body cells. Eow with

different conditions in temperature and p (warmer and more acidic than

in the lungs), and with pressure being exerted on the cells, the hemoglobin

will give up the oxygen where it will diffuse to the cells to be used for

cellular respiration, also called aerobic respiration. Cellular respiration is

the process of moving energy from one chemical form (glucose) into

another (-TA), since all cells use -TA for all metabolic reactions.

%t is in the mitochondria of the cells where oxygen is actually consumed

and carbon dioxide produced. 8xygen is produced as it combines with

hydrogen ions to form water at the end of the electron transport chain (see

chapter on cells). -s cells take apart the carbon molecules from glucose,

these get released as carbon dioxide. ach body cell releases carbon

dioxide into nearby capillaries by diffusion, because the level of carbon

dioxide is higher in the body cells than in the blood. %n the capillaries,

some of the carbon dioxide is dissolved in plasma and some is taken by

the hemoglobin, but most enters the red blood cells where it binds with

water to form carbonic acid. %t travels to the capillaries surrounding the

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lung where a water molecule leaves, causing it to turn back into carbon

dioxide. %t then enters the lungs where it is exhaled into the atmosphere.

Lun* C$&$cit

The normal volume moved in or out of the lungs during ?uiet breathing is

called tid$% )o%u+e. $hen we are in a relaxed state, only a small amount

of air is brought in and out, about !! m7. Jou can increase both the

amount you inhale, and the amount you exhale, by breathing deeply.

2reathing in very deeply is In!&i"$to" Re!e")e Vo%u+e and can

increase lung volume by *=!! m7, which is ?uite a bit more than the tidal

volume of !! m7. $e can also increase expiration by contracting our

thoracic and abdominal muscles. This is called e,&i"$to" "e!e")e

)o%u+eand is about #'!! ml of air. Vit$% c$&$cit is the total of tidal,

inspiratory reserve and expiratory reserve volumes; it is called vital

capacity because it is vital for life, and the more air you can move, the

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better off you are. There are a number of illnesses that we will discuss

later in the chapter that decrease vital capacity. Iital Capacity can vary a

little depending on how much we can increase inspiration by expanding

our chest and lungs. 6ome air that we breathe never even reaches the

lungsK %nstead it fills our nasal cavities, trachea, bronchi, and bronchioles.

These passages arenBt used in gas exchange so they are considered to be

de$d $i" !&$ce. To make sure that the inhaled air gets to the lungs, we

need to breathe slowly and deeply. ven when we exhale deeply some air

is still in the lungs,(about #!!! ml) and is called "e!idu$% )o%u+e. This air

isnBt useful for gas exchange. There are certain types of diseases of the

lung where residual volume builds up because the person cannot fully

empty the lungs. This means that the vital capacity is also reduced

because their lungs are filled with useless air.

CP Acute Renal Failure chap5

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