Respiratory System
-Cells need oxygen for production of ATP (cellular respiration)
-Cells need to get rid of carbon dioxide waste (excess CO2 causes acidity which is toxic)
-two systems supply O2 and get rid of CO2- respiratory and cardiovascular
-respiratory provides for gas exchange
3 processes
1. pulmonary ventilation (breathing)- inflow (inspiration) and outflow (expiration)
2. external (pulmonary) respiration- blood to lungs
3. internal (tissue) respiration- blood to cells
Organs:
Upper respiratory tract: nose, mouth, pharynx (throat)
Lower respiratory tract: larynx (voice box), trachea (windpipe), bronchi, lungs
Nose:
-air through nostrils or nares to large cavity called vestibule
- 3 functions:
1. warm, moisten and filter air
2. olfactory stimulation (smell)
3. hollow resonating chamber to modify speech
Pharynx:
-funnel shaped and 5” long
-also helps resonate
-three divisions
1. nasopharynx (superior)
2. oropharynx (middle)- 2 pairs of tonsils
3. laryngopharynx (inferior)
Larynx:
-walls of cartilage (Adam’s apple)- ring of hyaline
-voice production
-two pairs of folds (false and true vocal cords)
-air over cords causes vibrations- pitch controlled by tension (males thicker and
longer)
Trachea:
- 4.5” long and 1” diameter
-16-20 rings of cartilage (C’s)
Bronchi:
-right and left pulmonary bronchus (right shorter and wider)
-divide into secondary bronchi (lobar)- 3 for right, 2 for left
-tertiary bronchi to bronchioles to terminal bronchioles
Lungs:
-stretch from clavicle to diaphragm
-divided into lobes (3 right, 2 left)
-further divided into lobules
Alveolar- Capillary Membrane:
-diffusion and exchange of gases
-immense surface area (750 ft. 2)
Physiology of Respiration
Pulmonary Ventilation: exchange between atmosphere and lung alveoli
-pressure gradient produced
-inspiration (inhalation)- must make pressure low by increasing volume of lungs
-lungs expand by contraction of inspiratory muscles (diaphragm and external
intercostals)
-expiration (exhalation)- increase pressure in lungs
-muscles recoil and surface tension pulls alveoli
-labored breathing- muscles of abdomen and internal intercostals contract
-compliance- ease at which lungs and thoracic wall can be expanded
-depends on elasticity and surface tension
-decreases with lung tissue destruction or deficiency of surfactant (to decrease
tension)
-pulmonary air volumes and capacities (lab!!)- healthy adults about 12 respirations per
minute with 6 liters in and out (500 ml each respiration= tidal volume)
-exchange of O2 and CO2 depends on temperature, pressure, and solubility (CO2 high,
O2 low, N2 lower)
-nitrogen has little effect except under high pressure (nitrogen narcosis, the bends)
External respiration: alveoli to blood
1. partial pressure differences- can change with altitude (high altitude sickness)
2. surface area (emphysema)
3. diffusion distance- total thickness 0.5u
4. breathing rate and depth- some drugs slow rate (morphine)
Internal respiration: blood to cells
-diffuse through ECF
-only about 25% actually enters cells
Transport of O2 and CO2: function of blood
-oxygen does not dissolve in blood
-98.5% carried by hemoglobin
-affected by:
1. acidity- lower pH, lower O2
2. carbon dioxide- higher CO2, lower O2
3. temperature- higher temp, lower O2
4. age- fetal hemoglobin carries up to 30% more O2
-hypoxia- low level of oxygen available
-respiration controlled by nervous system- medulla oblongata and upper pons
Diseases and procedures:
Laryngitis, cancer, tracheostomy, intubation, nebulization, pneumothorax, hemothorax,
pleurisy, asthma, bronchitis, emphysema