Chapter 22: Respiration

• moist membrane
• opened pathway- trachea so gas can come in whenever it wants
• lots of surface area for gas exchange
• very thin membrane for diffusion
• elastic response- to both empty & fill the lungs
• highly vasculated- large amounts of capillaries

• walls are made of simple squamous epithelial cells
• macrophages clean up particles that enter lungs

• make surfactant
• -surfactant decreases natural surface tension in a water film

• the capillary cells are "fused" to alveoli walls by an elastic basement membrane
• entire thickness is 0.5 microns
• BP is low so that osmotic pressure wins

outter tissue of the lungs, very thin membrane

lining under the rib cage, gives good surface tension

• really not meant to be a "space"
• -pleural cavity does have less pressure than in lungs
• -surface tension b/w 2 tissue layers: "pulls" on lungs when ribs are raised

is active; need to create an internal pressure that is less than atmospheric pressure

at rest is passive

if you increase volume of a contained area you decrease pressure of gases w/in that area (inversely proportional)

gas volume will expand as temp. rises (directly proportional)

• In a mixture of gases, each gas component exerts its own pressure
• -partial pressures: oxygen and carbon dioxide

• atmospheric= 760 mm Hg
• intrapulmonary pressure= inside expanded lungs: 757
• intrapleural pressure= between ribs & visceral pleura 756-754

• pressure by raising ribs (intercostal muscles) and lowering diaphragm
• - as ribs move, they pull on lungs and aid in expansion due to surface tension b/w tissue

differences in pressures allow air flow into lungs

• ease of inhalation; little resistance to lung expansion
• Need: lungs easily expanded, muscles easily working ribs. alveoli easily open

• elastic tissue in lungs
• residual air volume
• cartilage of ribs to be flexible
• surfactant to decrease surface tension b/w alveoli
• surface tension b/w viseral pleura and rib covering
• for exhalation: ease of recoil and fast relaxation of muscles

• increased pressure in pleural cavity
• -may lead to atelectasis: collapsed lung

HAVE TO READ NOTES!!!

amount of air entering specific parts of lungs

amount of blood entering the capillaries of the same part of the lungs

• PO₂ levels: higher pO₂ means greater afinity
• -as the first O₂ adds, this increases the affinity for more to add
• pH: increased acidity decreases affinity -H+ ions ling ot the Hgb; discourage affinity of O₂
• -most significant in tissues where there is low pO₂
• Temp: increased in temp decreases affinity
• -metabolically active tissues generate heat and need more O₂

• very soluble in water
• -most will form carbonic acid
• -small percent stays as CO₂ in the blood
• -small percent is carried around by the protein regions of Hgb

HAVE TO READ NOTES!!!

• Shifting of H+ effects affinity of oxygen for Hgb
• -H+ shifts due to action of carbonic buffer system
• -H+ influences Hgb's affintiy for oxygen
• -Note systemic gas exchange details
• -Note alveolar gas exchange details
• Shifting of Cl ions encourages the buffer system in the tissue to shift to the R and stay there

• leads to acidosis
• EX: reduced breathing rate due to coma
• CO₂ levels and the buffer system go up and shift to the right

• alkalosis
• EX: hyperventilation
• CO₂ levels and the buffer system go down and shift left

• involuntary act over which you have voluntary control
• -chemoreceptors- in aorta & carotids closerly monitor blood pH
• -medulla oblongata- VRG & DRG
• - Pons- PRG

• has the inspiratory neurons
• -controls rhythm of breathing
• -at rest pace in about 12 breaths/min
• -inhalation take about 2 seconds
• -innervation from this region goes to diaphragm & external intercostals
• -absence of signal is expiration which takes about 3 seconds

• used for heavy group
• ex: forced exhalation: active event
• can constrict the intercostals and abdominal muscles to force air out
• integrates messages coming from various areas inside and outside CNS

• controls neurons in VRG
• needed to limit length and degree of inhalation
• impulses from VRG can be set at every 1/2 sec. (panting) to every 7 sec (prolonged inhalation)

• CC has some voluntary control; you can decide to alter breathing rate or hold your breath
• Chemoreptors for pH, also CO₂ and oxygen levels
• stretch receptors in thoracic cavity send signals if you try to breath in too much! cant over inflate lungs
• changes in blood pressure and heart rate also have input

• Chronic obstructive pulmonary disease
• Really 2 conditions combined: chronic bronchitis and emphysema

caused by: allergies & asthma, smoking damage, repeated infections, pollution

• pulmonary fibrosis
• loss of alveoli; replace w/ fibrous connective tissue
• extreme increase in residual air volume
• lungs can not recoil enough to get old air out
• barrel chest results as patient struggles to expel air
• causes: smoking, genetic factors

• prolonged irritation from smoke means constantly replacing cells that line tubes
• increased rate of mitosis: increased rish of mutation; smoke is known carcinogen
• loss of cells impairs ability to clear lungs; smokers cugh and emphysema result
• mucous membrane of the large bronchial tubes are the most freguent sources of cancer cells
• spreads rapidly; poor prognosis

• premature infants have not produced surfactant
• -lungs close up after an exhale and infant can't re-inflate lungs
• treatment: man- made surfactant and high oxygen levels

• msot common lethal genetic disease of Caucasians
• Two problems:
• 1.mucous produced in bronchial tubes is too thick
• -genetic flaw in ion transport
• -affects amount of fluid being put into mucous
• 2. Pancreas digestive enzymes don't reach the small intestine due to block duct