Chapter 13 The Respiratory System

Biology 112 Tri-County Technical College Pendleton, SC

System Essentials

Supply cells with oxygen Pick up carbon dioxide from the body Eliminate carbon dioxide from the body Organs of respiratory system include: Nose, pharynx, larynx, trachea, bronchi and its branches, and the alveoli of the lungs

Respiratory System Visual

A nose for this…or that

Only externally visible part of system Air enters nose through external nares (nostrils) Interior consists of

nasal cavity

by midline

nasal septum

divided

Olfactory receptors

in mucosa in superior part of cavity just below ethmoid bone

Nose, cont.

Rest of mucosa lining called respiratory mucosa rests on network of thin-walled veins that warms air flowing past  Mucosa moistens inhaled air & traps incoming debris Ciliated cells move contaminated mucus posteriorly toward throat (pharynx)  swallowed & digested by stomach acid

Nose, cont.

Three mucosa-covered lobes called nasal conchae increase surface area exposed to air  Also increase turbulence in nasal cavity Nasal cavity separated from oral cavity by partition called the

palate

Anterior palate supported by hard bone = hard palate Posterior palate is unsupported by bone = soft palate

Paranasal Sinuses

Nasal cavity surrounded by paranasal sinuses located in

frontal, sphenoid, ethmoid, and maxillary bones

 Lighten the skull   Resonance chambers for speech Produce mucus that drains into nasal cavity Nasal mucosa continuous throughout RT  Nasal infections can spread throughout mucosa Sinusitis difficult to treat & can cause marked change in voice quality

Pharynx

Muscular passageway for food and air commonly called throat Naso-; Oro-; and laryngopharynx Air enters superior portion (naso) from nasal cavity anteriorly Air descends through oropharynx and laryngopharynx to enter larynx below Food from mouth travels with air through oro and laryngopharynx but directed posteriorly to esophagus instead of entering larynx

Pharynx, cont.

Auditory tubes that drain middle ear open into nasopharynx

otitis media

(ear infection) may follow sore throat/pharyngeal infections Clusters of lymphatic tissue called

tonsils

found in pharynx Pharyngeal: (adenoids) located high in naso Palatine: oropharynx at end of soft palate Lingual: at base of tongue

Respiratory Visual

Larynx and Associated Structures

Larynx (voicebox) routes air/food into proper channels and plays role in speech Formed by 8 rigid hyaline cartilages and elastic cartilage called

epiglottis

Largest of hyaline cartilages is THYROID cartilage (Adam’s apple) Epiglottis protects superior opening of larynx

Larynx, cont.

Not swallowing, epiglottis does not restrict passage of air into respiratory passages Swallowing, larynx pulls forward and epiglottis tips forming lid over opening of larynx Routes food/drink into esophagus posteriorly Cough reflex  unconscious person

Larynx, cont.

Part of mucous membrane of larynx forms pair of folds called vocal folds (true vocal cords) which vibrate with expelled air Allows speech Slitlike passages between folds called

glottis

Larynx leads to

trachea

(windpipe)

Trachea

Extends from larynx to level of 5 th thoracic vertebra (~ midchest) Lined with ciliated mucosa Walls reinforced with C-shaped rings of hyaline cartilage Open parts of rings abut esophagus and allow it to expand anteriorly when one swallows

Trachea, cont.

Solid portions support walls and keep it

patent

(or open) in spite of pressure changes during breathing Tracheal obstructions are LIFE-threatening Heimlich maneuver can unclog trachea  It works or my side would be gone…for good Sometimes emergency trachesostomy is required

Bronchi Divisions

Trachea divides into right and left primary bronchi Each primary bronchi plunges into medial depression (the hilus-depressed area where vessels enter/leave an organ) of lung Right pulmonary bronchus is wider, shorter, and straighter than left Smaller subdivisons of primary bronchi within lung deliver air to alveoli

Bronchi Visual

Lungs and more…

Occupy most of thoracic cavity except for

mediastinum

(houses heart, great blood vessels, bronchi, esophagus, thymus, and trachea) Narrow superior portion is APEX; located just deep to clavicle Broad area resting on diaphragm is BASE Each lung divided into LOBES by fissures Left lung = 2 lobes; right lung = 3 lobes

Lungs, cont.

Surface covered by visceral (pulmonary) pleura and walls of thoracic cavity lined by parietal pleura Membranes produce pleural fluid which allows lungs to glide easily over thorax wall during breathing  Also causes 2 pleural layers to cling together Glide easily but resist being pulling apart  Absolutely essential for normal breathing

Lungs, cont.

PLEURISY (inflammation of pleura) can be caused by decreased secretion of pleural fluid  Surfaces become dry and rough  friction and stabbing pain with each breath  Another kind of pleurisy results in excess fluid and pressure on the lungs Primary bronchi  secondary & tertiary bronchi  bronchioles  terminal bronchioles (conducing zone structures)  respiratory zone structures

Lungs, cont.

RZ structures include respiratory bronchioles  alveolar ducts  alveolar sacs  alveoli and is ONLY site of gas exchange

Exchange of Gases

Alveoli composed largely of single layer of layer of squamous epithelial cells External surface of alveoli covered with cobweb of pulmonary capillaries Alveolar and capillary walls construct

respiratory membrane

(air-blood barrier) Blood flowing on one side; air on the other Gases diffuse across air-blood barrier by simple diffusion

Gas Exchange, cont.

Surface area of lungs = size of racquetball court (70-80 sq. meters) Macrophages (

dust cells

) wander in and out of alveoli to pick up bacteria/debris Cuboidal epithelial cells scattered throughout alveolar walls secrete

surfactant

(lipid that coats gas-exchange alveolar surfaces and is important in lung function

Gas Exchange Visual

Events of Respiration

Pulmonary ventilation (breathing) External respiration (gas exchange between pulmonary blood and alveoli) Respiratory gas transport (gas must be transported to/from lungs and tissue cells via bloodstream Internal respiration (gas exchange between blood and tissue cells at systemic capillaries

Mechanics of Breathing

Pulmonary ventilation depends on volume changes in thoracic cavity Volume changes lead to pressure changes  flow of gases to equalize the pressure Gas always fills its container  Volume of container related to pressure of gas Inspiration = gas flowing into lungs Expiration = gas flowing out of lungs

Mechanics of Inspiration

Diaphragm & external intercostal muscles contract Size of thorax increases  lungs adhere tightly to thorax walls  stretched to new, larger size of thorax Lung volume increases producing partial vacuum (pressure less than atmospheric pressure) Air rushes in to fill space —inspiration is always an active process

Mechanics Visual

Mechanics of Expiration

Usually passive process that essentially reverse of inspiration Active expiration (forced) —internal intercostals activated and contracted to depress rib cage and abdominal muscles contract to help FORCE air from lungs  Asthma (spasms of bronchioles) or chronic bronchitis/pneumonia can narrow respiratory passageways

Mechanics, cont.

Actelectasis

(lung collapse) renders lung useless for ventilation  air enters pleural space through chest wound or rupture of visceral pleural (allows air to enter pleural space from respiratory tract)

Pneumothorax

is term given presence of air in intrapleural space (disrupts fluid bond between pleura)

Mechanics, cont.

RESPIRATORY SOUNDS: Bronchial sounds produced by air rushing through large respiratory passageways such as trachea and bronchi Vesicular breathing sounds occur as air fills alveoli  Soft and resemble muffled breeze

Modified Respiratory Movements

Situations other than breathing move air in and out of respiratory system Most “nonrespiratory air movements” are result of reflex activity Cough, sneeze, crying, laughing, hiccups, yawn, sighing….

External Respiration

Actual exchange of gases between alveoli and blood (pulmonary gas exchange) Oxygen leaves alveolus and enters blood capillary Carbon dioxide leaves blood capillary and enters alveolus Occurs by simple diffusion (movement occurs toward area of lower [ ] of diffusing substance)

Gas Transport

Very small amount of O 2 dissolved in blood Most transported as

oxyhemoglobin

 Hb + O 2  HbO 2 Most CO 2 transported as bicarbonate ion 20-30% carried inside RBCs bound to hemoglobin (at different site than oxygen) Very small amount transported in plasma CO 2 + H 2 O  H 2 CO 3  H + + HCO 3 For carbon dioxide to diffuse out of blood into alveoli, reaction must be reversed

Gas Exchange Visual

Internal Respiration

Gas exchange process that occurs between systemic capillaries and tissue cells Carbon dioxide leaves tissues and enters blood Oxygen leaves blood and enters tissues All gas exchanges made according to the laws of diffusion

Respiration Controls

Activity of respiratory muscles, diaphragm, and external intercostals regulated by brain impulses carried by

phrenic

and

intercostal nerves

Respiratory rhythm and depth control center located in medulla and pons Medulla contains self-exciting inspiratory and expiratory centers  Sets the rhythm of breathing

Controls, cont.

Pons contains apneustic and pneumotaxic centers  Smooth out basic rhythms of inspiration and expiration Work to maintain ~ 12-15 respirations/min.

EUPNEA= normal breathing rate Inspiratory center active = inspire Expiratory center active = expire Apneustic center in pons=keeps inspiratory center going Pneumontaxic center in pons=limits length of inspiration and promotes expiration

Rate/Depth Breathing Factors

PHYSICAL such as walking, coughing, and exercise  >body temp can > rate of breathing CONSCIOUS such as singing, swallowing, or holding breath while swimming  voluntary control limited then involuntary takes over EMOTIONAL such as fright, surprise, or “other”

Factors, cont.

CHEMICAL most important rate and depth factors  CO 2 and O 2 levels in blood Increased levels of CO 2 and decreased blood pH MOST important stimuli leading to increase in rate/depth of breathing Changes in CO 2 medulla centers [ ] in blood act directly on Changes in O 2 [ ] in blood detected by

chemoreceptors

in AORTIC ARCH and CAROTID body in carotid artery

Factors, cont.

Chemoreceptors send impulses to medulla when blood O 2 levels are dropping

Hypoventilation

=accumulation of CO 2 blood and >ed blood acidity in

Hyperventilation

=CO 2 and

Acidosis or alkalosis can result

Respiratory Related Terms

Apena

is cessation of breathing caused by hyperventilation

Dyspnea

is labored or difficult breathing

Emphysema

=alveoli enlarge as walls of adjacent chambers break through; chronic inflammation promotes fibrosis of lungs  Requires lots of energy to exhale

Chronic bronchitis=

mucosa of lower respiratory passages become severely inflamed and produces extra mucus

Terms, cont.

Chronic bronchitis impairs ventilation and gas exchange and increases risk of lung infections

Pneumonitis

=inflammation of alveoli of the lungs resulting in them becoming clogged with mucus and/or fluids

Volumes and Capacities

Tidal volume (TV) is amount of air moved in and out of lungs with each breath (500 ml) Inspiratory Reserve Volume (IRV) is amount of air that can be forcibly taken in over tidal volume (2100-3200 ml) Expiratory Reserve Volume (ERV) is amount of air that can be forcibly exhaled after tidal expiration (1200 ml)

Volumes, cont.

Residual Volume (RV) is amount of air left in lungs that cannot be voluntarily expelled Vital Capacity (VC) is sum of TV + IRV + ERV  Total amount of exchangeable air  about 4800 ml in healthy young males Dead space volume is air that remains in conducting zone

Volume Visual