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• Chapter 14 - Respiratory System
• Ensures O2 gets to cells & CO2 removed from cells, helps maintain a constant environment in the body
• Organs - designed to perform 2 basic functions:
• Air Distributor - Gas Exchanger -
• Also -filters, warms, humidifies air
• Sinuses - speech, sound, smell (olfaction)
• Structural Plan -• Basic structure is like a many branched tube
(respiratory tree) - nose, pharynx, larynx, trachea, bronchi, lungs
• Alveoli - thin-walled sacs at end of tubes where gas is exchanged– Millions in each lung - > surface area
– Each is covered with a network of capillaries (like a hairnet), also, wall is single layer thick
– Gases (O2 & CO2) are exchanged by passive diffusion through the respiratory membrane (very thin - 1 micron thick)
• Respiratory Tract -
• Divided to assist in description of symptoms associated w/ problems
• Upper - nose, pharynx, larynx (URI - head cold)– Located outside thoracic cavity
• Lower - trachea, all parts of the bronchial tree, & lungs (LRI - chest cold)– Located inside thoracic cavity
• Respiratory Mucosa -– Membranes that lines most of the distribution tubes
– Air entering nose - contaminated w/ irritants (insects, dust, pollens, bacteria)
– Mucous acts as most important air purification mechanism, traps almost everything < air to alveoli
– 125ml mucous / day
• Mucous blanket - continuous sheet– Moved upward to pharynx by cilia that cover
epithelial cells (beat one way) [smoking-paralyze]
• Nose -• External nares (nostrils) air enters & moves to
R & L nasal cavities (lined w/ mucosa), parititioned by nasal septum– Surface - moist (mucous), warm (many blood
vessels), olfactory receptors that are nerve endings (sense of smell)
• Paranasal sinuses - continuous mucosa (4- frontal, maxillary, sphenoidal, ethmodial) all drain into the nasal cavities, hollow help lighten skull & serve as resonant chambers for production of sound
• Lacrimal sacs - two ducts located inner
aspect of eyes, drain tears into nasal cavity
• Conchae (KONG-kee) - three shelf-like structures that protrude into the nasal cavity (both sides)– Mucosa-covered
– > Surface area to warm and humidify
• Supplemental O2 - bubbled thur water to humidify (if not dries & irritates resp. tract)
• Pharynx - • Called the throat - about 5 inches long• 3 portions -
– Nasopharynx - upper part, behind nose - contain auditory (eustachian) tubes which connect to middle ear (equalizes air pressure between middle & exterior ear), continuous mucosa (infections)
– Oropharynx -behind mouth– Laryngopharynx - lowest portion
• Serves as passage of air (shared w/ GI)
• Tonsils -
– Masses of lympathic tissue in pharynx
– Pharyngeal tonsils - nasopharynx• Called adenoids if swollen, make
breathing thru nose difficult
– Palatine tonsils - oropharynx
– Tonsillectomy - removal of tonsils
– Tonsillitis - inflammation
• Larynx - voice box (just below pharynx)– Made of cartilage (largest - thyroid cartilage -
Adam’s apple)
• Vocal cords - 2 fibrous bands, stretch across interior of larynx– Muscles cause them to tense (high pitched) &
relax (low pitched)
• Glottis - space between vocal cords
• Epiglottis - cartilage, partially covers the opening of larynx (trapdoor), closed when swallowing
• Trachea -
• Windpipe - 4 1/2 inches long– From larynx to bronchi– Lined with mucous membrane
• Vital function - furnishes open airway
• Considerable force to squeeze closed– Almost Noncollapsible material - 15 to 20 C-shaped
cartilage, stacked (soft tissue between)– Obstructed by: tumors, enlarged lymph nodes,
aspirate food (choking-5th leading cause of accidental death in US)- Heimlich Maneuver - open windpipe that is suddenly obstructed
• Bronchi, Bronchioles, & Alveoli -
• Upside down tree (bronchial tree)
• Larger tubes are ringed with cartilage
• Primary bronchi -R & L >R & L lungs
• Secondary bronchi - branches in each lung
• Divide into smaller & smaller tubes - ultimately into tiny tubes made of smooth muscle - bronchioles > divide into microscopic tubes - alveolar ducts end in several alveolar sacs (cluster of grapes)
• Alveolar sacs - (cluster of grapes) - each
cluster made up of numerous alveoli (single grape)
• Alveoli - very effective in gas exchange– Thin walled, each in contact w/ blood
capillary– Surfactant - substance that covers the resp.
membrane in the alveoli• Helps reduce surface tension > keeps
alveoli from collapsing as air moves in & out
• IRDS (Infant resp. distress syndrome) -
– Premature infants (< 37 weeks gestation or wt. < 5 lbs. at birth), sacs collapse during expiration - inspiration requires more force to reinflate > labored breathing
• Lungs & Pleura –
• R - three lobes L - two lobes
• Apex - upper end toward collarbone
• Base - of lungs rest on diaphragm
• Pleura - serous membrane linings, thin, moist, slippery– Parietal pleura - lines walls of thorax
– Visceral pleura - covers the lungs
– Intrapleural space - between , small amt. fluid
• Pleurisy - inflammation of parietal pleural– Difficulty breathing, stabbing pain (rubs)
– Caused by infection, tumors, etc.
• Atelectasis - collapse of the lung > effective breathing due to < ventilation
• Pneumothorax - Hemothorax
• Respiration - – Exchange of gases between living organism &
environment - Pair of lungs - place where air & circulating fluids (blood) can exchange gases
– Pulmonary ventilation - (breathing) air in & out of lungs (external respiration- exchange gases)
– Internal respiration - exchange gases between blood & cells
– Cellular respiration - use of O2 by cells
• Mechanisms of Breathing - Pulmonary Ventilation - 2 phases (inspiration - expiration)– Changes in pressure cause movement of air in-out
– Lungs inside thoracic cavity - changes in shape &
size of cavity (by muscles)- changes air pressure w/in cavity
– Air moves from area of high pressure to area of low pressure
• Inspiration - occurs when chest cavity enlarges > lungs expand > air rushes in & down to alveoli
• Inspiratory muscles - Diaphragm & external intercostals– When these muscles contract > ^ volume in cavity >
which < pressure - draws air in
• Diaphragm -
– Most important muscle of inspiration
– Dome-shaped muscle
– Flattens (contract) during inspiration > cavity elongate (top to bottom)
– Phrenic nerve - stimulates to contract
• External Intercostal -– Between the ribs
– When contract > enlarge cavity (front to back) ( side to side) > < pressure (air rushes in)
• Expiration - ordinarily passive process (quiet expiration)– Begins as inspiratory muscles relax
– Cavity returns to smaller size
– Lungs recoil - elastic nature < in size as air leaves
• Expiratory muscles - used when speaking, sing, do heavy work– Need more forceful expiration to > depth & rate of
ventilation
– Internal intercostals & abdominal muscles
– Cavity size < & pressure w/in > & air flows out
• Internal Intercostals Muscles-
– Depress the rib cage < cavity size front - back
• Abdominal Muscles - – Contract & push abd. organs against underside of
diaphragm(^ dome-shape)
– Shortens top to bottom thoracic size
• Exchange of Gases in Lungs -– Blood from R ventricle into pulmonary artery to
lungs > tiny capillary beds close to alveoli
– Diffusion occurs between tiny capillaries & alveoli (O2 & CO2)
• Movement of substances from high concentration to area of low concentration
– Oxyhemoglobin - O2 & hemoglobin combination in RBCs (to be carried to cells)
– Most CO2 carried to lungs as bicarbonate ion (HCO3) , some carried in RBCs as carbaminohemoglobin
• Exchange of Gases in Tissues -– Internal respiration - diffusion
– Oxyhemoglobin breaks down > O2 into cells (used) - CO2 out of cells
• Volumes of Air Exchanged in Pulmonary Ventilation -
• Spirometer - device used to measure amt. air exchanged in breathing
• Tidal Volume (TV) - (like ocean tides) amt. of air that comes & goes regularly– Normal Inspiration - 500 ml (one pint)– Normal Expiration - equal amt.
• Vital Capacity (VC) - largest amt. air we can breathe out in one expiration– Normal young adult = 4800 ml
• Expiratory Reserve Volume (ERV) -– Amount of air forcibly exhaled after tidal
volume
• Inspiratory Reserve Volume (IRV) -– Amount of air forcibly inspired over & above a
normal resp.
• As TV (normal breath) >, ERV & IRV < (reserve spaces)
• VC = TV + IRV + ERV
• Residual Volume (RV) - Air that remains in lungs after most forceful expiration
• Regulation of Respiration -– Need for O2 > as activity > (make more waste
products > removed)– Take more breaths (^ rate) & > tidal volume (depth)– Automatic adjustments - in resp. & circulation
(heart pumps faster & harder)
• Respiratory control centers - medulla & pons of brain - they stimulate resp. muscles– Receptors sense: Changes in O2 & CO2 levels in
blood, Acid levels, Amt. stretch in lungs > change resp. rate & depth
• Cerebral Cortex - – Modifying effect on inspiratory &
expiratory centers of the medulla
– Voluntarily change pattern of breathing
– Hold breath (swimming, speaking, eating)
– As limits - resume breathing when our bodies need O2 or has too much CO2
• Receptors Influencing Respiration -
• Chemoreceptors -in carotid & aortic bodies– Sense > CO2, < O2, acid levels in blood– Send nerve impulses to resp. regulation centers
• Pulmonary Stretch Receptors -– Located in lungs - throughout airways &
alveoli– Impulses influence normal breathing pattern to
protect from excess stretching (overinhalation) – When TV reached - stimulus sent to inhibit
more inspiration
• Types of Breathing -
– Eupnea - normal resp. rate, unaware of breathing
– Hypoventilation - slow & shallow
– Hyperventilation - rapid & deep
– Dyspnea - labored or difficult
– Orthopnea - upright position
– Apnea - breathing stops
– Cheyne-Stokes Resp. -apnea & hyperventilation
– Respiratory Arrest - failure to resume breathing after period of apnea