The Respiratory SystemThe Respiratory System

General Functions of the General Functions of the SystemSystem• Ventilation (breathing) – the entrance and Ventilation (breathing) – the entrance and

exit of air into and out of the lungsexit of air into and out of the lungs• External respiration – the exchange of External respiration – the exchange of

gases (carbon dioxide and oxygen) gases (carbon dioxide and oxygen) between the air and bloodbetween the air and blood

• Internal respiration – the exchange of Internal respiration – the exchange of gases between the blood and tissue fluidgases between the blood and tissue fluid

• Transport – of gases to and from the lungs Transport – of gases to and from the lungs and the tissuesand the tissues

Anatomy and the flow of air:Anatomy and the flow of air:

• The Nose / Nasal passages begin to cleanse the The Nose / Nasal passages begin to cleanse the air with course hairs inside the nostrils and air with course hairs inside the nostrils and continue to do so with cilia and mucus in the continue to do so with cilia and mucus in the nasal cavities.nasal cavities.

• Air warmed by the blood vessels lying close to the Air warmed by the blood vessels lying close to the surface of the lining of the airways.surface of the lining of the airways.

• Air is moistened by the mucus epithelium that Air is moistened by the mucus epithelium that lines most of the air passages.lines most of the air passages.

• Conversely, as air leaves the body it deposits its Conversely, as air leaves the body it deposits its moisture along the way. This can cause the nose moisture along the way. This can cause the nose to drip and is what is responsible for you being to drip and is what is responsible for you being able to see your breathe on a cold day.able to see your breathe on a cold day.

Nose and Nasal CavityNose and Nasal Cavity

• 2 Nostrils2 Nostrils• 2 Nasal cavities separated by a septum 2 Nasal cavities separated by a septum

composed of bone and cartilage.composed of bone and cartilage.• Conchae are bony ridges that project out Conchae are bony ridges that project out

laterally trapping air and increasing laterally trapping air and increasing surface area for moistening and warming.surface area for moistening and warming.

• Lacrimal glands (tear) drain into the nasal Lacrimal glands (tear) drain into the nasal cavity which is why your nose runs when cavity which is why your nose runs when you cry.you cry.

• Nasal cavity is separated from the oral Nasal cavity is separated from the oral cavity by the hard and soft palate.cavity by the hard and soft palate.

PharynxPharynx

• Broken into three parts: nasopharynx, Broken into three parts: nasopharynx, oropharynx, and laryngopharynx.oropharynx, and laryngopharynx.

• The tonsils form a protective ring around The tonsils form a protective ring around the pharynx – this is lymphatic tissue that the pharynx – this is lymphatic tissue that protects against the invasion of inhaled protects against the invasion of inhaled pathogens.pathogens.

• It is the junction of air and food passage. It is the junction of air and food passage. The esophagus remains closed by the The esophagus remains closed by the epiglottis unless a person is swallowing.epiglottis unless a person is swallowing.

LarynxLarynx

• A cartilaginous structureA cartilaginous structure• Contains the Adam’s AppleContains the Adam’s Apple• Called the voice box because it contains Called the voice box because it contains

the vocal cords.the vocal cords.• The vocal cords are mucosal folds The vocal cords are mucosal folds

supported by elastic ligaments, and the supported by elastic ligaments, and the opening between them is the glottis. opening between them is the glottis.

• When air is expelled past the vocal cords When air is expelled past the vocal cords through the glottis the cords vibrate through the glottis the cords vibrate producing sound. The greater the tension producing sound. The greater the tension on the cords and the narrower the glottis, on the cords and the narrower the glottis, the higher the pitch.the higher the pitch.

TracheaTrachea

• Tube with c-rings of cartilage. The open Tube with c-rings of cartilage. The open part of the c is facing the esophagus – why part of the c is facing the esophagus – why do you think this is?do you think this is?

• Lined with pseudostratified ciliated Lined with pseudostratified ciliated columnar epithelium. Cilia beat upward columnar epithelium. Cilia beat upward moving the particles out of the system. moving the particles out of the system. Goblet cells produce mucus to trap debris.Goblet cells produce mucus to trap debris.

• Smoking destroys the cilia causing soot Smoking destroys the cilia causing soot from smoking to get caught in the lungs.from smoking to get caught in the lungs.

Bronchial TreeBronchial Tree

• Contains the same histology as the trachea. Contains the same histology as the trachea. Divides trachea into right and left primary Divides trachea into right and left primary bronchi.bronchi.

• Branches into a large number of secondary Branches into a large number of secondary bronchi that eventually lead to bronchioles – bronchi that eventually lead to bronchioles – rings of cartilage are no longer present.rings of cartilage are no longer present.

• During an asthma attack, the smooth muscle During an asthma attack, the smooth muscle of the bronchioles contracts, causing of the bronchioles contracts, causing constriction and wheezing.constriction and wheezing.

• Each bronchiole leads to an elongated space Each bronchiole leads to an elongated space enclosed by a bunch of air pockets called enclosed by a bunch of air pockets called alveoli.alveoli.

LungsLungs

• Paired, cone-shaped structures.Paired, cone-shaped structures.• The right lung has 3 lobes and the left, The right lung has 3 lobes and the left,

2. The lobes are divided further into 2. The lobes are divided further into lobules which each have a bronchiole lobules which each have a bronchiole serving many alveolar sacs.serving many alveolar sacs.

• Diaphragm sits inferiorly to the lungs.Diaphragm sits inferiorly to the lungs.• Each lung is enclosed by a pleural sac Each lung is enclosed by a pleural sac

(serous membrane).(serous membrane).

AlveoliAlveoli

• Composed of simple squamous epithelium Composed of simple squamous epithelium and is surrounded by capillaries which are and is surrounded by capillaries which are also composed of simple squamous. What also composed of simple squamous. What major function does the structure of major function does the structure of simple squamous allow?simple squamous allow?

• Alveoli are covered in surfactant, a Alveoli are covered in surfactant, a lipoprotein that allows them not to lipoprotein that allows them not to collapse under the pressure of water collapse under the pressure of water surface tension.surface tension.

Breathing MechanismBreathing Mechanism

• Air into the lungs is called inspiration or Air into the lungs is called inspiration or inhalation. Air leaving the lungs is inhalation. Air leaving the lungs is expiration or exhalation.expiration or exhalation.

• When we are relaxed only a small amount When we are relaxed only a small amount of air moves into and out of the lungs with of air moves into and out of the lungs with each breath = tidal volume (about 500ml).each breath = tidal volume (about 500ml).

• Deep breathing = vital capacity (max in Deep breathing = vital capacity (max in and max out).and max out).

• About 70% never reaches the alveoli, it About 70% never reaches the alveoli, it fills the rest of the air passages (dead air fills the rest of the air passages (dead air space).space).

VentilationVentilation

• Things to recall: location of Things to recall: location of intercostals, location of diaphragm, intercostals, location of diaphragm, lungs adhere to thoracic wall lungs adhere to thoracic wall because of the pleura, a continuous because of the pleura, a continuous column of air extends from the column of air extends from the pharynx to the alveoli.pharynx to the alveoli.

InspirationInspiration

• Diaphragm contracts and lowers. Internal Diaphragm contracts and lowers. Internal intercostals contract and lift the rib cage intercostals contract and lift the rib cage up and out – this increases the volume of up and out – this increases the volume of the thoracic cavity.the thoracic cavity.

• Air pressure in the alveoli decreases due Air pressure in the alveoli decreases due to the above and causes a partial vacuum.to the above and causes a partial vacuum.

• Difference in alveolar compared to Difference in alveolar compared to atmospheric pressure allows the lungs to atmospheric pressure allows the lungs to fill.fill.

ExpirationExpiration

• Passive phase – diaphragm and Passive phase – diaphragm and intercostals relax. intercostals relax.

• The volume of the thoracic cavity The volume of the thoracic cavity decreases to less than the decreases to less than the atmospheric pressure allowing the atmospheric pressure allowing the air to leave the alveolar sacs.air to leave the alveolar sacs.

Cough Reflex – dislodge Cough Reflex – dislodge foreign material from the lower foreign material from the lower respiratory passages.respiratory passages.• Initiated when the sensory receptors detect Initiated when the sensory receptors detect

substances and initiate action potentials that pass substances and initiate action potentials that pass along the vagus nerves to the medulla oblongata.along the vagus nerves to the medulla oblongata.

• 2.5L of air is inspired 2.5L of air is inspired the epiglottis closes the epiglottis closes the the vestibular folds close tightly to trap the air in the vestibular folds close tightly to trap the air in the lungs lungs the abdominal muscles contract to force the abdominal muscles contract to force the abdominal contents up against the diaphragm the abdominal contents up against the diaphragm the muscles of expiration contract forcefully. the muscles of expiration contract forcefully.

• As a result the pressure in the lungs increases to As a result the pressure in the lungs increases to 100 mm Hg then the vestibular folds and epiglottis 100 mm Hg then the vestibular folds and epiglottis open suddenly and air rushes at a high velocity open suddenly and air rushes at a high velocity carrying the particles with it.carrying the particles with it.

Sneeze Reflex – dislodges Sneeze Reflex – dislodges foreign material from the foreign material from the upper respiratory passages.upper respiratory passages.• Similar to cough reflex.Similar to cough reflex.

• Source of irritation is in the Source of irritation is in the trigeminal nerves in the nasal cavity.trigeminal nerves in the nasal cavity.

• The uvula and the soft palate are The uvula and the soft palate are depressed so that air is directed depressed so that air is directed primarily through the nasal primarily through the nasal passages.passages.

Respiration and Health - URIRespiration and Health - URI

• Many times caused by Many times caused by Streptococcus pyogenes.Streptococcus pyogenes.• Sinusitis – caused when nasal congestion blocks Sinusitis – caused when nasal congestion blocks

the openings between the nasal cavity and the the openings between the nasal cavity and the cranial sinuses.cranial sinuses.

• Otitis Media – bacterial infection in the middle ear – Otitis Media – bacterial infection in the middle ear – spreads from nasal congestion through the spreads from nasal congestion through the eustachian tubes from the nasopharynx to the eustachian tubes from the nasopharynx to the middle ear.middle ear.

• Tonsillitis – occurs when the (lymphatic) tissues in Tonsillitis – occurs when the (lymphatic) tissues in the pharynx become inflammed.the pharynx become inflammed.

• Laryngitis – infection of the larynx – usually Laryngitis – infection of the larynx – usually accompanies upper respiratory infection – if it accompanies upper respiratory infection – if it doesn’t it could mean there is cancer in the throat.doesn’t it could mean there is cancer in the throat.

Respiration and Health - LRIRespiration and Health - LRI

• Bronchitis – infection of the primary and Bronchitis – infection of the primary and secondary bronchi causes inflammation, secondary bronchi causes inflammation, mucus production, and usually results in mucus production, and usually results in coughing.coughing.

• Pneumonia – viral or bacterial infection of the Pneumonia – viral or bacterial infection of the lungs in which the bronchi and alveoli fill with lungs in which the bronchi and alveoli fill with a thick fluid.a thick fluid.

• Tuberculosis – caused by the bacteria Tuberculosis – caused by the bacteria Tubercle bacillus Tubercle bacillus – the bacteria invade the – the bacteria invade the lungs and cause the cells to isolate lungs and cause the cells to isolate themselves by building a capsule.themselves by building a capsule.

Respiration and Health – other Respiration and Health – other respiratory disorders.respiratory disorders.• Restrictive Pulmonary Disorders – vital capacity is Restrictive Pulmonary Disorders – vital capacity is

reduced due to loss of elasticity (results from a reduced due to loss of elasticity (results from a build up in fibrous connective tissue) this is build up in fibrous connective tissue) this is usually a result of inhaling asbestos or fiberglass.usually a result of inhaling asbestos or fiberglass.

• Obstructive Pulmonary Disorders – air does not Obstructive Pulmonary Disorders – air does not flow freely in the airways – includes things like flow freely in the airways – includes things like chronic bronchitis (airways inflamed and full of chronic bronchitis (airways inflamed and full of mucus – cilia lost), emphysema (alveoli are mucus – cilia lost), emphysema (alveoli are distended and the area available for gas exchange distended and the area available for gas exchange is reduced), and asthma (disease of the bronchi is reduced), and asthma (disease of the bronchi and bronchioles – exposure to irritants causes and bronchioles – exposure to irritants causes spasms in the smooth muscle of the bronchi).spasms in the smooth muscle of the bronchi).

Lung CancerLung Cancer

• Occurs in progressive steps:Occurs in progressive steps:• 11stst – thickening and callusing of the cells lining the – thickening and callusing of the cells lining the

primary bronchi.primary bronchi.• 22ndnd – cells with atypical nuclei appear in the callused – cells with atypical nuclei appear in the callused

lining.lining.• 33rdrd – a tumor made of these cells may occur in one – a tumor made of these cells may occur in one

areaarea• 44thth – some of these cells break loose and penetrate – some of these cells break loose and penetrate

other tissues a process called metastasis.other tissues a process called metastasis.• Tumors may continue to grow eventually blocking off Tumors may continue to grow eventually blocking off

the bronchi completely and causing the lung to the bronchi completely and causing the lung to collapse.collapse.

Aging and the Respiratory Aging and the Respiratory SystemSystem

• Maximum breathing capacities decline and Maximum breathing capacities decline and as a result fatigue increases.as a result fatigue increases.

• Weakened intercostal muscles and increased Weakened intercostal muscles and increased inelasticity of the rib cage reduce the inelasticity of the rib cage reduce the volume that the thoracic cavity can hold.volume that the thoracic cavity can hold.

• Changes in the lungs and capillaries result in Changes in the lungs and capillaries result in less efficient gas exchange.less efficient gas exchange.

• Risk of contracting respiratory disease Risk of contracting respiratory disease increases as the cells of the passages age increases as the cells of the passages age and lose cilia.and lose cilia.