Physiology - Respiratory System

What are the Functions of respiration

ventilation (breathing), Gas exchange (between blood and lungs and blood and tissues), oxygen utilization (by tissues to make ATP)

External Respiration

ventilation and gas exchange in lungs

Internal respiration

oxygen and gas exchange in tissues

How does gas exchange between air and blood occur?

diffusion

where does O2 diffuse into and why

diffuses into blood because O2 concentration is higher in the lungs than in the blood

where does CO2 diffuse out of and why

diffuses out of the blood because CI2 concentration in the blood is higher than in the lungs

What are the results of gas exchange

inspired air contains more O2 than expired air and less CO2 than expired air. O2 levels are higher in the blood leaving the lungs via the pulmonary veins (both good things)

What zones are the respiratory system divided into

conduction zone and respiratory zone

Conduction zone

gets air to the respiratory zone

respiratory zone

site of gas exchange

what are Alveoli

air sacs in the lungs where gas exchange occurs (300 million of them)

Type I alveolar cells

95-97% total surface area where gas exchange occurs

Type II Alveolar cells

secrete pulmonary surfactant and reabsorb sodium and water, preventing fluid buildup

Total Pathway of airflow?

air travels through nasal cavity, pharynx, larynx (through the glottis and vocal cords), trachea, right and left primary bronchi, secondary bronchi, tertiary bronchi, terminal bronchioles, respiratory zone (respiratory bronchioles), terminal alveolar sac

Pathway of air flow (Conducting Zone)

air travels through nasal cavity, pharynx, larynx (through the glottis and vocal cords), trachea, right and left primary bronchi, secondary bronchi, tertiary bronchi, terminal bronchioles

Pathway of Air Flow (Respiratory Zone)

respiratory zone (respiratory bronchioles), terminal alveolar sac

Functions of the Conducting Zone?

transport air to lungs, warm, humidifies, filters, and cleans the air (via mucus traps small particles, and cilia move it away from the lungs), voice production in the larynx as air passes over the vocal folds

What does the thoracic cavity contain within the central mediastinum (central region)?

heart, trachea, esophagus, and thymus

What fills the rest of the thoracic cavity but is not in the central region

lungs

parietal pleura

lines thoracic wall

visceral pleura

covers lungs

intrapleural space

potential space between normally pushed together parietal and visceral pleura

Diaphragm

dome-shaped skeletal muscle of respiration that separates thoracic and abdominal cavity

Compliance

Lungs can expand when stretched, defined as the change in lung volume per change in transpulmonary pressure: deltaV/deltaP

Elasticity

lungs return to initial size after being stretched due to elastin fibers

surface tension

resists distension, exerted by fluid secreted in the alveoli

Physical properties of lungs

compliance, elasticity, and surface tension

Ventilation

air moves from higher to lower pressure

what causes the pressure differences between the two ends of the conducting zone

changing lung volumes

atmospheric pressure

pressure of air outside of the body

Intrapulmonary pressure

pressure in the lungs (-1 inspiration, +1 expiration)

Intrapleural pressure

pressure within the intrapleural space (between parietal and visceral pleural) (-8 inspiration, -5 expiration)

Transpulmonary (transmural) Pressure

difference across the wall of the lung (+7 inspiration, +6 expiration)

Inhalation

Intrapulmonary pressure is lower than atmospheric pressure, subatmospheric

subatmospheric or negative pressure

Pressure below that of the atmosphere

Exhalation

Intrapulmonary pressure is greater than atmospheric pressure

Boyle’s Law

that the pressure of a gas is inversely proportional to its volume

An increase in lung volume during inspiration causes what?

decreases intrapulmonary pressure to subatmospheric levels, so air goes in

A decrease in lung volume during exhalation

increases intrapulmonary pressure above atmospheric levels, so air goes out

Law of Laplace

Pressure is directly proportional to surface tension and inversely proportional to radius of alveolus (e.g. Small alveoli would be at greater risk of collapse without surfactant)

Surfactant is secreted by?

type II alveolar cells

what does surfactant consist of

hydrophobic protein and phospholipids

Function of surfactants

prevent collapse of alveoli, reduce surface tension between water molecules

are surfactants more concentrated in smaller or larger alveoli

smaller

Respiratory distress syndrome (RDS)

Production begins late in fetal life, so premature babies may be born with a high risk for alveolar collapse

Breathing

Pulmonary ventilation

Inspiration

breathe in

Expiration

breathe out

how is breathing accomplished

changing thoracic cavity/lung volume

what does the diaphragm do in inspiration and expiration

contracts/flattens in inspiration and relaxes/dome in expiration (both vertically)

Muscles involved in inspiration

parasternal and external intercostals (horizontally and raise ribs)

Muscles involved in expiration

interbal intercostals abs (horizontally and lower ribs)

Mechanism of inspiration

thoracic & lung volume increases causing the intrapulmonary pressure to decrease and let air in

Mechanism of expiration

thoracic & lung volume decreases causing intrapulmonary pressure to increase and let air out

Spirometry

pulmonary test where subject breathes into and out of a device that records volume and frequency of air movement on a spirogram

What does a spirometry test measure and diagnose?

measures lung volume and capacities and can diagnose restrictive and disruptive lung disorders

Normal, Quiet Breathing during inspiration

Diaphragm and external intercostal muscles contract, increasing thoracic and lung volume, decreasing intrapulmonary pressure to about -1 cm H2O

Normal, Quiet Breathing during expiration

Diaphragm and external intercostal muscles relax, decreasing thoracic and lung volume, increasing intrapulmonary pressure to about +1 cm H2O

Forced Ventilation during inspiration

Inspiration aided by contraction of accessory muscles (scalenes, sternocleidomastiod), decreases intrapulmonary pressure to -27 cmH2O or lower

Forced Ventilation during expiration

Expiration, aided by contraction of abdominal muscles and internal intercostal muscles, increases intrapulmonary pressure to +40 cmH2O or higher

Tidal Volume (Lung Volume Measurement)

amount of air expired or inspired in each breath of quiet breathing

Expiratory reserve volume (Lung Volume Measurement)

amount of air that can be forced out after tidal volume

Inspiratory reserve volume (Lung Volume Measurement)

amount of air that can be forced in after tidal volume

Residual volume (Lung Volume Measurement)

amount of air left in lungs after maximum expiration

Vital capacity (Lung Capacity Measurements)

maximum amount of air that can be forcefully exhaled after a maximum inhalation

Total lung capacity (Lung Capacity Measurements)

amount of gas in the lungs after a maximum inspiration

Inspiratory capacity (Lung Capacity Measurements)

amount of gas that can be inspired after a normal expiration

Functional residual capacity (Lung Capacity Measurements)

amount of air in lungs after a quiet expiration

Vital capacity (Relationship between Lung Volume and Capacity)

inspiratory reserve volume + expiratory reserve volume + tidal volume

Functional residual capacity (Relationship between Lung Volume and Capacity)

residual volume + expiratory reserve volume

Total minute volume (Relationship between Lung Volume and Capacity)

tidal volume × breaths per minute (~ 6L/min)

Asthma symptoms

dyspnea (shortness of breath) and wheezing

Asthma causes

inflammation, mucus secretion, and constriction of bronchioles

Allergic asthma

triggered by allergens stimulating T lymphocytes to secrete cytokines and recruit eosinophils and mast cells, which contribute to inflammation

asthma triggers

cold or dry air

asthma is reversible via what?

Albuterol (bronchodilator)

Chronic Obstructive Pulmonary Disease (COPD)

Chronic inflammation, narrowing of the airways, and alveolar destruction (emphysema and chronic obstructive bronchiolitis)

Is there a cure for COPD and where does it land in the causes of death

no and 5th leading cause of death

what is COPD accelerated by

decline in FEV

what does COPD inflammation involve

macrophages, neutrophils, and cytotoxic T cells

COPD and smoking

Smoking promotes the infiltration of obstructing fibrous tissue and muscle in the airways and remodeling of blood vessels in the lungs, leading to pulmonary hypertension (most people with COPD smoke).

what does smoking trigger

Excessive mucus production and inflammation

Emphysema

destruction of alveoli which reduces the surface area for gas exchange, w/fewer alveoli to put pressure on bronchioles, they collapse during expiration

Emphysema cause and triggers

smoking and triggers inflammation and destruction of alveoli by immune cells.

Atmospheric Pressure Measurement

measured using a barometer, 760 mmHg at sea level

Dalton’s Law

The total pressure of a gas mixture is equal to the sum of the pressure that each gas would exert independently

Partial Pressure of oxygen (PO2)

PO₂ = 0.2093 x 760 = 159 mmHg ( air is 20.93% oxygen and total pressure of air is 760 mmHg)

Henry’s Law

explains the amount of gas that can dissolve in liquid (Alveoli and blood capillaries quickly reach equilibrium for O₂ and CO₂ which helps maximize the amount of gas dissolved in fluid)

What does Henry’s Law depend on

Solubility of the gas in the liquid (constant), Temperature of the fluid (more gas can dissolve in cold liquid); doesn’t change for blood, and partial pressure of the gases, the determining factor

Partial Pressure of O2 and CO2 in the alveoli

partial pressure of O2 is 105 and partial pressure of CO2 is 40

Partial Pressure of O2 and CO2 from pulmonary artery

partial pressure of O2 is 40 and partial pressure of CO2 is 46

Partial Pressure of O2 and CO2 to pulmonary artery

partial pressure of O2 is 100 and partial pressure of CO2 is 40

Partial Pressure of O2 and CO2 in systemic veins

partial pressure of O2 is 40 and partial pressure of CO2 is 46

Partial Pressure of O2 and CO2 in systemic arteries

partial pressure of O2 is 100 and partial pressure of CO2 is 40

the rate of blood flow through the lungs is blank to that through the systemic circuit

equal (5.5 L/minute cardiac output)

what is the pressure difference between the left atrium and the pulmonary artery

10 mmHg

what makes vascular resistance low and why is it low

low pressure/low resistance pathway and reduces the possibility of pulmonary edema

When alveolar partial pressure O2 is low what happens to the pulmonary arterioles

constrict

When alveolar partial pressure O2 is high what happens to the pulmonary arterioles

dilate

T/F: Pulmonary arterioles are autoregulated

true