Week 5 - Respiratory system Flashcards
Respiratory system - functions
Process that provides body cells w/ OXYGEN & removes waste product CO2: PULMONARY VENTILATION (air in and out), GAS EXCHANGE (gas betw: lungs & blood), GAS TRANSPORT, TISSUE & GAS EXCHANGE (gas betw: blood & tissues) → serve to maintain homeostasis:
- speech & sound productions
- neurons for sense of smell
- pressure change, thoracic assist w/ flow of venous blood
- maintaining acid-base balance
- synthesize an enzyme involved w/ prod. of ANGIOTENSIN → MAINTAINS BP
respiratory system - classification
Upper: passageways from nasal cavity to larynx
Lower: trachea to respiratory tract’s terminal structures (LUNGS + ALVEOLI)
Conducting zone: air is filtered, warmed & moistened inc, structures from nose cavity to bronchioles
Respiratory zone: where gas exchange occurs: contain alveoli
The structure of the epithelium changes along the respiratory tract from quite rough to withstand abrasion to delicate & simple where gas exc occurs
Alveoli
TYPE I: 90% of cells in alveolar wall, very thin → allows for RAPID diffusion of gases → huge surface area; inc gas exc efficiency
TYPE II: 10% of the cells - synthesis of SURFACTANT → reduces surface tensions on alveoli
ALVEOLAR MACROPHAGES: mobile phagocutes derived from bone marrow; clean up & digest derbris that made its way into alveolus
Alveoli - surface tension
Creates surface tension at gas water boundary. greatest when alveoli are at smallest diametre during expiration
- SURFACTANT produced by type II, is a component of a liquid film coating cells of the alveolusl opposes surface tensions collapsing force →like a detergent
Lungs & pleura
- each lung is found within a PLEURAL CAVITY
- PARIETAL PLEURA: outer layer of serous membrane; fused to ribcage, diaphragm
- at hilum parietal pleura turns over on itself to create inner layer of membrane →VISCERAL PLEURA
- visceral layer is continuous w/ surface of lungs
- pleural membrane secrete a thin layer of SEROUS FLUID of 10 called PLEURAL FLUID → lubricates lungs
pulmonary ventilation
- BETWEEN BREATHS: lung pressure is equal to atm press. causes= no movement of air betw lungs & atmosphere
- INSPIRATION : DIAPHRAGM & INTERCOSTALS CONTRACT: inc lung vol = dec. lung pressure: pressure lower than atmos press → cause air to enter lungs
- EXPIRATION: DIAPHRAGM & INTERCOSTALS RELAX: dec. lung vol = dec,.lung press. pressure higher than atm press. causes air to leave lungs
inspiration
- volume changes rely on skeletal muscle of thoracic cavity called INSPIRATORY MUSCLES: diaphragm & intercostals
- as thoracic cavity expands →pulls of parietal pleura → pulls on visceral pleura →pulls lungs outward → inc.volume
- inflation aided by warming of inhaled air.
- 500ml of air flows w/ a quiet breath
expiration
- normal expiration is mostly passive
- RECOIL: of elastic tissues and diaphragm relaxation together dec, lung vol & raise INTERPULMONARY PRESSURE above atmospheric pressure → air flows out
- accessory muscles, intercostals & abdominal muscles →forceful
- HEIMLICH MANEUVER: delivering abdominal thrusts that push up diaphragm → for people choking
pulmonary ventilation - pressures
- ATM PRESS: generated by pull of gravity on air around us, at sealevel atm press is 760 mmHg
- INTRAPULMONARY PRESS: air pressure within ALVEOLI rises and falls w/ inspiration & expiration always equalise w/ atmospheric pressure @ equilibrium
- INTRAPLEURAL PRESS: pressure in pleural cavity; also rises & falls w/ in & expiration; NEVER equalises w/ atm press.
pulmonary volume
- measuring volumes of air a person exchanges w/ each breath
- SPIROMETRE: produces a graph that records normal & forced in &exhilation
- TIDAL VOL (VT) amount of air in or expired during normal quiet ventilation (500ml)
- INSPIRATORY RESERVE VOL. (IRV): VOL OF AIR THAT CAN BE FORCIBLY INSPIRED AFTER NORMALirv (2100-3300Ml)
- expirature reserve
pulmonary capacity
Two or more pulmonary volumes can be combined to calculate four pulmonary capacities
- INSPIRATORY: TV +IRV
- FUNCTIONAL RISIDUAL VOL: ERV+RV → after tidal
- VITAL CAPACITY: TV+IRV+ ERV
- TOTAL LUNG CAPACITY (TLC): IRV+ TV+ ERv+ RV
minute ventilation
- VT x repiratory rate at rest (500x12-6/L/min), Max: 125 to 170L/min
Alveolar ventilation < minute ventilation
- some air never reaches alveoli
(VT - anatomic dead space) x respiratory rate
- (500-150) x 12 = 4200 mL/min or 4.2 L/min
FORCED EXPIRATORY VOL (FEV)
- % of vital capacity exhaled/ time
- healthy adult - 75 to 85% 1sec
- diagnostic tool
daltons law
LAW OF PARTIAL PRESSURE
- each gas in a mixture exerts its own pressure, called PARTIAL PRESSURE (Pgas), total press. of a gas mixture is sum of PP of all component gas
PN2+PO2+PCO2+Pothers = atm press.
henry’s law
Degree to which a gas dissolves in a liquid is proportional to both its partial press. & solubility in liquid explains behaviour of gases in air that come into contact w/ water in body
- NITROGEN: high Pgas solubility-low →little in blood plasma
- OXYGEN: low Pgas more solubule water than N
- CARBON DIOXIDE: lowest Pgas soluble in water (20x than O2)
gas exchange - pulmonary
- diffusion of gases betw. alveoli & blood in pulmonary capillaries
- O2 diffuses from alveoli to blood
- CO2 simultaneously diffuses in the opp. direction
- pulmonary gas exc. driven by pressure gradients
gas transport - oxygen
conc in arterial blood: 20ml of O2 in 100mil of bood when leaving alveolar capillaries
- 98.5% bound to haemoglobin
- 1.5% dissolved
haemoglobin saturation depends on Pgas of O2 in lungs & tissues. tightness (Affinity) w/ which Hb binds to O2
gas transport - carbon dioxide
Waste product, transported back into lungs in blood; dissolves in plasma, bound to Hb , as bicarbonate ions
- 7-10% of total CO2 dissolved in blood plasma
20% bound to Hb
70% as bicarbonate → important to blood pH homeostasis
- carries -ve charge counteracted by chloride shift REVERSE REACTION IN CAPILLARIES
- carbonic acid reformed in erythrocyte from H2CO2 into H2O& CO2
- CO2 is free to diffuse out of pulmonary capillary into alveoli along pressure gradient.
Factors changing affinity of Hb for oxygen by altering shape
- inc. TEMPERATURE decreases Hb’s affinity for O2
- BOHR EFFECT: when acidity & PCO2 inc → Hb binds oxygen less strongly so more oxygen is unloaded
- BPG (2,3-BISPHOSPHOGLYCERATE) made by erythrocytes as a side reaction of glycolysis →erythrocydes produce greater amounts of BPG when Hb is less saturated w/ O2
breathing control
- Neurons in MEDULLA OBLONGATA & PONS control unconcious breathing → repiratory rhythmicity centres in medulla
- central & peripheral chemoreceptors = specialised cells detect & monitor Co2 leves, H+ & O2 in body
- coluntary conc. produced by cerebral motor cortex
chemoreceptors
CENTRAL CHEMORECEPTORS - initiate a feedback loop cycle by detecting changes in CO2 & H+ conc by monitoring H+ levels in CSF
ALTERATIONS OF ARTERIAL PCO2 - most powerful stimulus that induces a classic negative FB loop recponses from the CC
- HIGH PCO2 or H+ conc trigger HYPERVENTILATION, lowers CO2 & H+ →restoring homeostasis
- LOW PCO2 & H+ conc. trigger HYPOVENTILATIONL inc CO2 & H+ →restoring homeostasis
