The Respiratory System

Chapter 10

• http://www.youtube.com/watch?v=HiT621PrrO0&feature=related

Introduction• Main job of respiratory system is to bring

oxygen (O2) into the body and to carry carbon dioxide (CO2) out of body.

• Body’s cells need a constant supply of oxygen to burn nutrients to produce energy.

• How does this take place in a simple, single celled animal?

• How does this differ from a complex animal such as a dog or cat?

Two types of Respiration• External Respiration

• Occurs in the lungs.• Is the exchange of oxygen and carbon dioxide

between the air that is inhaled into the lungs and the blood flowing through the pulmonary capillaries.

• Without which, there would be no oxygen in the blood to be transmitted to the system.

• Internal Respiration• Takes place between the body’s cells and the

blood.• Cells receive oxygen and dispose of their

carbon dioxide

External Respiration

Internal Respiration

The Respiratory System• Composed of:

• Lungs• Nostrils• Nasal passages• Pharynx• Larynx• Trachea• Bronchi• Bronchioles• Alveolar ducts• Alveoli

Functions of the Respiratory System• Primarily:

• Oxygen- carbon dioxide exchange.• Secondarily:

• Voice production• Body temperature regulation• Acid-base balance regulation• Sense of smell

Voice Production• Also called phonation.• Begins in the larynx (voice box).

• Two fibrous connective tissue bands called the vocal cords (or vocal folds) stretch across the lumen of the larynx and vibrate as air passes over them.

• Other structures such as thorax (chest cavity), nose, mouth, pharynx (throat), and sinuses may contribute resonance and other characteristics to the vocal sounds.

Body Temperature Regulation• Cold conditions:

• Superficial blood vessels just under the epithelium of the nasal passages helps warm inhaled air before it reaches the lungs.

• Keeps chilled air from circulating through the lungs.

• What could be the problem with this?• Hot Conditions:

• Aids in cooling through panting.• Rapid respiration movements caused during

panting cause increased evaporation of fluid from the lining of the respiratory passages and mouth, which helps to cool the blood just under the epithelium.

Acid Base Balance• Important homeostatic mechanism in the

body.• pH- unit used to measure relative acidity or

alkalinity.• Lower the pH, the more acidic the

environment• Higher the pH, the more alkaline the

environment.• A pH of 7 is neutral, neither acidic or

alkaline.• Normal pH of the blood is 7.4

(acceptable range of 7.35-7.45).

Acid-Base Balance Continued…• Respiratory system contributes to the process of acid-

base control by its ability to influence the amount of CO2 in the blood.

• Higher CO2, lower the blood pH, more acidic the blood.• Respiratory system can alter CO2 content in the blood

by adjusting how fast air is breathed in and out.

Sense of Smell• Also called the olfactory

sense.• Receptors are contained in

patches of sensory epithelium located up high in the nasal passages.

Structure of Respiratory System• Consists of lungs and system of tubes that

connects them with the external environment.

• Upper Respiratory Tract• All of the respiratory structures outside

the lungs.• Lower Respiratory Tract

• All of the respiratory structures within the lungs.

Upper Respiratory Tract• Includes: (all air that enters and leaves lungs does so through

the upper respiratory structures). • Nose• Pharynx (throat)• Larynx (voice box)• Trachea (wind pipe)

Nose• Begins with nostrils also known as nares.

• Are external openings of the respiratory tube that lead into the nasal passages.

Nasal Passages• Located between the nares and the

pharynx.• Nasal Septum- a wall that separates the

left nasal passage from the right.• Hard and Soft palates- separates the nasal

passages from the mouth.• Contain turbinates (nasal conchae)-thin,

scroll-like bones covered with nasal epithelium that occupy most of the lumen of the nasal passages.

Nasal Turbinates• Two sets are found in each nasal passage.

• Dorsal Turbinate• Ventral Turbinate

• These divide each nasal passage into 3 main passageways, each called a nasal meatus.

• Ventral nasal meatus is located between the ventral turbinate and the floor of the nasal passage

• Middle nasal meatus is located between the two turbinates.

• Dorsal nasal meatus is located between the dorsal turbinate and the roof of the nasal passage.

• Common nasal meatus is located on either side of the nasal septum, is continuous with other 3 meatuses.

Lining of the nasal passages• Consists of pseudostratified columnar

epithelium with cilia projecting from the cell surfaces up into a layer of mucus that is secreted by many mucous glands and goblet cells.

• Cilia project from the cell surfaces up into a layer of mucus

• Extensive complex of large blood vessels lies just beneath the nasal epithelium.

Functions of the Nasal Passages• Housing receptors for sense of smell.• Condition the inhaled air

• Warming• Warmed by blood flowing in blood vessels

• Humidifying• By the mucus and other fluids on the

epithelial surface• Filtering

• Helps to remove particulate matter before it reaches lungs.

• Due to twists and turns of turbinates.• Respiratory infections cut down on this

filtering. Why?

Paranasal Sinuses• Usually just called sinuses• Outpouchings of the nasal passages that are

contained within spaces in certain skull bones. • Each sinus is named after the skull bone that

houses it.• Most animals have two frontal sinuses and

maxillary sinuses.• Some animals (including humans) have two more.• Sinuses have same ciliated lining as the nasal

passages. Cilia keep fluid and debris from accumulating in sinuses and obstructing the openings of the nasal passages.

Sinusitis• Inflammation of the sinuses. Due to infection,

tumors, etc. • Build up of pressure can be very uncomfortable for

the animal. • Can be treated with medication but if ineffective,

hole may need to be drilled into the sinus to allow drainage.

Pharynx (Throat)• Common passageway for both respiratory

and digestive systems.• Rostral end is divided into:

• Nasopharynx (respiratory passageway)• Oropharynx (digestive passageway)

• Caudal end is divided into:• Esophagus (digestive passageway)• Larynx (respiratory passageway)

Breathing and Swallowing• Pharynx has to stay open to allow airflow.• Larynx and pharynx work together to prevent

swallowing from interfering with breathing and vice versa.

• Swallowing requires:• stopping the process of breathing,• covering the opening of the larynx,• moving material to rear of pharynx,• open the esophagus, • move material into it, • open covering to larynx, • breathing resumes.

G=OropharynxH=LarynxJ=Nasopharynx

K=EsophagusI=Trachea

Larynx• Commonly called the “voice box” .

• Short, irregular tube that connects the pharynx with the trachea.

• Made of segments of cartilage that are connected to each other and the surrounding tissues by muscles.

• Supported in place by the hyoid bone.

Cartilage components of the Larynx

• Epiglottis• single, leaf-shaped; projects forward from the ventral

portion of the larynx• During swallowing, the epiglottis is pulled back to

cover the opening of the larynx• Arytenoid cartilages

• paired; attachment site of the vocal cords• Muscles adjust the tension of the vocal cords by

moving the cartilages. • Arytenoid cartilages and the vocal cords form the

boundaries of the glottis-the opening into the larynx. • Thyroid cartilages

• Shaped as a V that forms and supports the ventral portion of the larynx.

• Cricoid cartilage• Ring-shaped, helps from and support the caudal

portion of the larynx.

Larynx continued• Vestibular folds (false vocal cords) - are

found in nonruminant animals. Are a second set of connective tissue bands.

• Not involved in voice production.• Each side of larynx, blind pouches called

lateral ventricles project laterally into the space between the vocal cords and the vestibular folds. • These lateral ventricles are often

involved in the treatment of a condition in horses called roaring (laryngeal hemiplegia).

Laryngeal Hemiplegia (Roaring) or Laryngeal paralysis• Occurs when muscles that tighten

cartilage are paralyzed.• At rest usually does not cause a problem• When animal exercises , may result in

obstruction of the glottis.• Surgery may remove ventricle to allow

scar tissue to tighten cartilage.

Laryngeal Intubation• Process in which an endotracheal

tube is placed through the glottis to the trachea.

• May be helped by the use of a laryngoscope- an instrument that helps to hold down epiglottis.

• Laryngospasms –sometimes seen in cats, when glottis is touched, larynx slams shut. Is reflex.

Aspiration Pneumonia

• Inflammation of the lungs produced by inhalation of a foreign material.

• Use caution when administering liquids to animals (remember the swallowing process).

• May see during anesthesia.• May potentially be fatal.

Laryngeal Functions• 1. Voice Production

• Originates at vocal cords in the larynx.• Vocal cords are attached to arytenoid cartilages

and stretch across the lumen of the larynx. • As air passes over vocal cords, they vibrate

and produce sounds.• Muscles attached to arytenoid cartilages control

the tension of the vocal cords. • Lessening tension of the vocal cords allows for

lower pitched sounds.• Tightening of the vocal cords allows for higher

pitched sounds.

Laryngeal Functions • 2. Prevention of Foreign material being

inhaled.• Accomplished by trapdoor action of the

epiglottis.• The moving up and down of the adam’s

apple is part of this process. • 3. Control of airflow to and from lungs.

• Partially through epiglottis action when swallowing occurs but also through adjustments in the size of the glottis.

• Adjustments in the size of the glottis.• May even be helpful in straining.

Coughing• Cough is generated behind a closed

glottis. • Breathing muscles contract, compressing

the thorax.• Builds pressure behind the closed glottis.• When glottis suddenly opens, the forceful

release of air results in a cough.• Purpose of coughing is to clear mucus and

other matter from lower respiratory passages.

Trachea• Windpipe- short, wide

tube that extends from the larynx down through the neck region into the thorax.

• Lined with ciliated epithelium.

• Bifurcation of the Trachea- occurs at about the level of the heart.

Trachea• Structurally, trachea is a tube of fibrous

tissue and smooth muscle held open by hyaline cartilage rings and lined by the same ciliated epithelium that is present in the nasal passages.

• Hyaline cartilage rings are C shaped.

Trachea continued• Ciliated lining of the trachea is similar to

the nasal passages. • The mucous layer on its surface traps tiny

particles of debris that have made it down this far into the respiratory tube.

• Eventually reaches pharynx and is swallowed.

Collapsing Trachea• Pushing down of the cartilage

area, obstructs air flow.• Causes dry, honking cough.

Lower Respiratory Tract• Consists of:

• Bronchi• Bronchioles• Alveolar ducts• Alveoli

Bronchial Tree• Air passageways that lead from the

bronchi to the alveoli. • Divide into smaller and smaller

passageways.• After enters the lung, each main bronchus

divide into smaller bronchi, which divide into smaller bronchi, eventually getting to bronchioles. • Bronchioles continue to subdivide down

to alveolar ducts.• Alveolar ducts end in alveolar sacs.

Bronchial Tree continued• Bronchial tree are not just rigid tubes.• Diameter of each can be adjusted by smooth

muscle fibers in the wall. • What kind of smooth muscle is this?

• Autonomic Nervous system controls this smooth muscle.

• During times of intense physical activity, bronchial smooth muscle relaxes, allowing air passageways to dilate to their maximum. Called Bronchodilation

• During relaxed time, smooth muscle partially contracts, reducing size of air passageway. Called Bronchoconstriction.

Asthma• Bronchioles are sometimes overly Bronchioles are sometimes overly

sensitive to certain irritantssensitive to certain irritants• Results in bronchoconstriction Results in bronchoconstriction

• Can range from mild and annoying Can range from mild and annoying to life-threateningto life-threatening

• More common in humansMore common in humans• Occurs most commonly in cats in the Occurs most commonly in cats in the

summersummer

Alveoli• Where external respiration takes place. • Where oxygen and carbon dioxide are

exchanged.• All respiratory structures exist to move air

in and out of alveoli.• Tiny, thin walled sacs surrounded by

capillaries. • Walls are composed of simple squamous

epithelium.• These thin layers allow for easy movement

of oxygen and carbon dioxide.

Alveoli Continued• Each alveolus is lined with surfactant – a

fluid that helps reduce surface tension of the fluid.

• This prevents the alveoli from collapsing as air moves in and out during breathing.

Lungs• Two lungs form a shape like a cone. • Base of lungs are on the diaphragm.• Apex of the lung is near the top (pointed like area). • Mediastinum- area between the two lungs, also called

what??

Lobes of the Lungs• Left Lung

• Cranial lobe• Caudal lobe

• Right Lung• Cranial lobe• Middle lobe• Caudal lobe• Accessory lobe

Horse lung is different… How?

Lungs continued• Hilus- where air, blood, lymph, and nerves

enter and leave the lung. • Only area of lung that is fastened in

place.

1. Oblique fissure2. Vertebral part3. Hilum of lung4. Cardiac impression5. Diaphragmatic surface

Lungs Continued

Circulation through the lungs• Blood supply to and from the lungs is

called pulmonary circulation• Blood enters via pulmonary artery• Blood reenters heart via pulmonary vein

Consistency of Lungs• Light and have a spongy consistency• Fetal lungs have a solid consistency.

Why??• Testing used to determine if a breath was

taken.

Thorax• Also known as the thoracic cavity – chest cavity.

• Bound by thoracic vertebrae dorsally, ribs and intercostal muscles laterally, and the sternum ventrally.

• Contains:• Lungs• Heart• Large blood vessels• Nerves• Trachea• Esophagus• Lymphatic vessels• Lymph nodes

Thorax Continued• Pleura- thin membrane that covers the organs and structures in the

thorax and lines the inside of the thoracic cavity. • Visceral layer of pleura- covers the thoracic organs and structures.• Parietal layer of pleura- lines the cavity• Between pleural layers is a lubricating fluid.

Diaphragm• Dome shaped.• Thin sheet of skeletal muscle

that forms caudal boundary of the thorax.

• When diaphragm contracts, dome flattens out and enlarges thorax.

• Helps with inspiration

Respiration• Process requires effective movement of air

into and out of lungs at an appropriate rate and in sufficient volume to meet the body’s needs at any particular time.

• Pressure within the thorax is negative with respect to atmospheric pressure.• Pulls lungs tight against the thoracic

wall• Flexible nature of lungs allows them to

conform with shape of the thoracic wall.• Pleural fluid provides lubrication.• Lungs follow thoracic wall.

Respiration continued• Negative pressure also aids in the return

of blood to the heart.• Helps to pull blood into the large veins of

the mediastinum.• Helps to draw blood from the midsize

veins and then dump these into the atria.

http://physiol.umin.jp/resp/resp_cycle/pic/fig0100.gif

Pneumothorax• Loss of air into thorax.• Disrupts the negative pressure.• Causes can be due to trauma or lung

disease.

Inspiration• Process of drawing air into the lungs.• Also called inhalation• Basic process is enlargement of the

volume of the thoracic cavity by the inspiratory muscles. • Main inspiratory muscles:

• Diaphragm• External Intercostal muscles.

• Located in the external portion of the spaces between the ribs (intercostal spaces).

Expiration• Process of pushing air out of the

lungs.• Also called exhalation.• Thoracic cavity is decreased in size,

compresses lungs and pushes air out through the respiratory passages.

• Main muscles are the internal intercostal muscles and the abdominal muscles.

• How do muscles work??• Does not require as much work as

inspiration

Respiratory Volumes• Tidal volume – volume of air inspired and expired

during one breath.• Varies according to body’s needs.• Smaller when animal is at rest and larger when

excited and active.• Minute volume – volume of air inspired and expired

during one minute.• Calculated by multiplying the tidal volume by

breaths per minute. • Measured in mL or Liters

• Residual volume – volume of air remaining in the lungs after maximum expiration.• Residual volume always remains.• Lungs will never be completely emptied of air.

Lung volumes continued• Measured with a spirometer.

Exchange of Gases in Alveoli• Simple diffusion process from areas of

high concentration to areas of low concentration.

• Atmospheric air contains 21 % oxygen and 0.03 % carbon dioxide.

• Blood in lungs is high in carbon dioxide and low in oxygen.

• Oxygen diffuses from alveolar air to blood, carbon dioxide diffuses to alveolus which is refreshed with oxygen from next breath.

Partial Pressure of Gases• Dalton’s law- states that the total pressure of a

mixture of gases is the sum of the pressure of each individual gas.

• Partial pressure- the pressure of each individual gas.

• Partial pressure is expressed with a P before chemical symbol for gas.

• Partial pressures of O2 and CO2 in the blood of alveolar capillaries is determined by the partial pressures of O2 and CO2 in alveolar air• the greater the amount of a gas in the air you

breath, the more concentrated it will be in the blood.

Control of Breathing• Breathing does not require conscious effort

although use skeletal muscles that are under voluntary control.

• Is controlled by an area in the medulla oblongata of the brain stem.• Known as the respiratory center.

• Houses control systems for inspiration, expiration, and breath holding.

• Subconsciously sends nerve impulses to the muscles to direct them how to contract.

• Usually can only control breathing consciously for a short period of time before autonomic system kicks back in.

Two systems to control breathing• 1. Mechanical system

• Sets routine inspiration and expiration limits.

• 2. Chemical system• Monitors that the levels of certain

substances in the blood and directs adjustments in breathing if they get out of balance.

Mechanical Control• Operates through stretch receptors in the

lungs that set limits on routine expiration and inspiration.

• When lungs inflate to a certain point, nerve impulse says that lungs are full and stops muscle contractions that allow lungs to fill.

• Then will notify muscles to contract to start expiration

Chemical Control• Monitors blood and affects breathing if something

gets out of balance.• Monitors:

• CO2 content• The pH• O2 content

• Blood level of CO2 and blood pH are linked. As CO2 rises, pH goes down. If this occurs, chemical control system signals to increase rate and depth of breathing to even it out.

• Vice versa if pH goes up.

Chemoreceptors• Peripheral- aortic bodies and carotid

bodies• Central- found in the medulla of the brain.

• Normal respiratory rates:• 10-30 breaths per minute in dog• 20-30 breaths per minute in cat.

Bagging a Patient• Term used to describe manual control of an

anesthetized patient’s breathing by squeezing and releasing the rebreathing bag.

• May cause more CO2 than normal to be removed from lungs, so may trigger that patient will not breathe once bagging stops.

• Hypoxia- Decrease in blood O2.• If this occurs, chemical control system signals

the respiratory center to increase rate and depth of breathing so more O2 will be taken in.

Terms• Sneeze- similar to a cough, but originates in the

nasal passages, burst of air is directed through the nose and mouth in effort to eliminate the irritant.

• Yawn- slow, deep breath taken through a wide-open mouth. May be stimulated by slight decrease in oxygen levels, drowsiness, fatigue, and boredom.

• Sigh- slightly deeper than normal breath. May serve to expand lungs more than normal. May hear “sighing” patient under anesthesia.

• Hiccups- spasmodic contractions of the diaphragm accompanied by sudden closure of the glottis. Usually self-limiting

• http://www.youtube.com/watch?v=sU_8juD3YzQ&NR=1&feature=fvwp

• http://www.med.ucla.edu/wilkes/lungintro.htm