Repiratory System
4 Respiratory Functions
1. gas exchange
2. pH regulation
3. Pathogen Protection
4. Vocalization
Lungs Characteristics
- spongy tissue
- volume is mostly air-filled spaces
- airways connect to lung (trachea, bronchii)
Thoracic Cage Bones and Muscles
- ribs, sternum, vertebrae
- intercostals, sternocleidomastoid, scalenes
Pleural Membranes
- double-walled membranous sac around the lungs
- attached to lungs, ribs and muscles
- pleural fluid makes surfaces moist and slippery for breathing; ensures both layers stick
Cellular Respiration
- intracellular reaction of O2 with oraganic organic molecules to produce CO2 and ATP
External Respiration
- movement of gases between cells and environment
Upper Respiratory Tract Structure and Function
Structures involved:
- mouth, nasal cavity, pharynx, larynx
Functions:?
1. passageway of air
2. warms air
3. adds water vapour for dryness
4. filters foreing materials
Lower Respiratory Tract Structure and Functions
Structures Involved:
- trachea, brincioles, branches
Functions:
1. pulls air from URT
2. Absorbs O2
3. Releases CO2
LRT: Bronchial Tree
- series of tubes that carry air, starting with trachea
- mainstem bronchi branch 22 times, making smaller tubes and decreasing cartilage, increasing smooth muscle
(bronchi = cartilage) (bronchiles = no cartilage)
LRT: Trachea
- hyaline cartilage, smooth muscle
- pseudostratified ciliated columnar epithelium
- mucus prod by goblet cells and sermucus glands
- helps trap pathogens and move muscus out
LRT: Respiratory Bronchiole
- smooth muscle, elastic tissue
- thin musuc membrane
- divides further into alveolar ducts
Bronchoconstriction
- constriction of smooth muscle in bronchioles decreasing expansion
- more resistance to airflow
- parasympathetic input = muscarinic receptors
Bronchodilation
- relaxation of smooth muscle in bronchioles increasing expansion
- less resistance to airflow
- sympathetic B2 receptor activtion = NE
Lung lobule
- contains alveoli
- gas exhange
- singe layer cells line each alveolus
- close association with capillary network
Cells in Alveoli
Type 1 Alveolar Cells:
- 95% of surface
- very thin
- facolotates diffusion of gases
Type 2 Alveolar Cells:
- thick cells
- create surfactant
- removes excess fluid
Pulmonary Circulation
- high flow = low pressure
- low pressure = short length of pulm BV and large total cross-sectional area of BV
- 5L/min through lungs
Ideal Gas Law and Boyles Law
1. PV = nRT
2. P1V1 = P2V2
both express inverse relationship between V and P of air
Daltons Law
- total pressure exerted by a mix of gases = to the sum of pressures exerted by each individual gas
PPG= Patm x % gas in atmosphere
Mechanics of Breathing
- Air flow occurs with a pressure gradient
- flows from area of high pressure to one of low pressure
- Diffusion moves high pP to low pP
4 Pressures involved with Breathing
1. Atmospheric Pressure
2. Intrapulmonary pressure and Volume
3. Intrathoracic Presure and Volume
4. Intrapleural Pressure
Negative Pleural Pressure
- elastic recoil of lungs
- thoracic wall wants to expand
- pleura is pulled in opp directions
- intrapleural space is always negative pressure
Pleural Fluid
- contains water
- creates a hydrostatic force between pleural layers
- lungs and visceral pleura move with the thoracic wall
Insirapation
1.
- Diaphragm contracts and moves inferiorly
- External intercostals contract and move ribs up and out
2.
- Extra force from muscles pulling thoracic wall out
- overcomes elastic recoil force of lungs
3.
- thoracic wall expands
- increase VOL of cavity
4.
- extra muscular force pulls pleura, creating greater - plP
- ensures lungs stuck to moving cavity
- VOL increase
4 Lung Volumes In Ventilation
1. Tidal Volume
- air moves with normal inspiration.expiration
2. Inspiratory Reserve Volume
- additional vol that could be breathed in
3. Expiratory Reserve Volume
- Air that is forcefully exhaled after normal expiration
4. Residual Volume
- Volume left after max exhalation
3 Lung Capactiies
1. Total Lung Capacity
- sum of all volumes
2. Inspiratory Capacity
- tidal vol + inspiratory reserve vol
3. Vital Capacity
- tidal vol + Inspiratory reserve vol + expiratory reserve vol
Factors that Affect Ventilation
Compliance
- how easily the lungs can inflate
Elastance
- ability to resist being deformed
- lung has natural elastic fibres to allow this
Lung Compliance Determinance
1. Elastic Forces of the lung tissue
2. Surface tension of fluid lining walls
What Decreases Lung Compliance?
- fibrosis
- chronic infection/inflammation
- decreased prod of surfactant
LePlace's Law
- pressure inside of buble formed by thin fluid is a function of surface tension and radius of the bubble
Surface tension in Alveoli
- alveoli lined with thin layer of water
- water has high surface tension due to cohesive property
- smaller alveoli = high pressure (wont inflate)
Surface Tension Production in Alveoli
1. type 2 alveolar cells release surfactant
2. surfactant disrupt cohesive property of water reducing surface tension
3. this reduces pressure in alveolus
Surface Tension in Smaller Alveoli
- surfactant is more concentrated
- helps reduce surface tension of smaller alveoli more than large ones
- results in equalization of pressure across all alveoli
- alveoli inflate uniformly
Airway Radius (Poiseuille's Law)
- length and viscosity of the airways/air are essentially constant
- radius is determined by airway resistance in lungs
Obstructive Lung Disease
- resistive work is increased because airways are obstructed
- asthma, emphysema, chronic chronchitis, COPD
Restrictive Disease
- elastic work is increased because the lung is stiff and non-compliant
- insterstitial lung disease
- obesity hypoventilation syndrome
- scoliosis
- cystic fibrosis