The Respiratory System

Respiratory System Functions

• Ventilation

• Air filtration

• Gas exchange (blood ⇔ lungs)

• Cellular respiration:

• CH2O + O2 → CO2 + H2O

Respiratory System Anatomy

• External nares, nasal septum, nasal cavity w/ mucous and hairs

• Three nasal conche

• Hard and soft palate

• Paranasal sinuses

• Muscular passageway for food, water and air.

• Tonsils:

• Immune system functions

Larynx

• Surrounded by cartilage

• Epiglottis

• Cough reflex

• Vocal cords

• Glottis

Trachea and Bronchi

• Trachea is supported by C-shaped rings of hyaline cartilage

• Lined w/ ciliated mucosa

• Right and left bronchi inferiorly

• Bronchioles branch repeatedly until they reach alveoli

The Lungs

• Fill most of the thoracic cavity

• Lobes

• Spongy and elastic

Pleural Cavities

• Lungs are covered by serous membranes:

• Visceral pleura

• Parietal pleura

Alveoli

• Gas exchange units

• Simple squamous epithelia

• Increase surface area for gas exchange

• Produce surfactants

• Phagocytes migrate around alveoli

Properties of the Lung

• Elasticity vs. Compliance (what’s the difference?)

• The lungs are compliant and elastic

• Surface tension reduces compliance (it’s a problem!!)

Gerridae is a family of true bugs in the order Hemiptera, AKA water striders, water bugs, magic bugs, pond

skaters, skimmers, water scooters, water skaters, water skippers, or Jesus bugs.

Properties of the Lung

• Surfactants decrease surface tension and increase compliance because they disrupt the cohesive forces between water molecules

• Respiratory Distress Syndrome

Properties of the Lung

• Question: What happens if you get a knife through the thoracic cavity and it penetrates the lung?

• Does the lung explode?

• Does the lung collapse?

• Does the lung remain the same?

• Intrapleural pressure is always negative (so what?)

• Negative pressure created by:

• Surface tension of alveolar fluid

• Elasticity of lungs

• Elasticity of the thoracic wall

Properties of the Lung

edge of collapsed lung

Respiratory Physiology

1. Pulmonary Ventilation (air exchange with the environment)

2. Gas Exchange (between blood and alveoli and between blood and systemic cells)

3. Respiratory Gas Transport (movement of O2 and CO2 throughout the body)

4. Cellular respiration (aerobic respiration requires O2 and produces CO2 - these reactions are what makes a respiratory system necessary, but they are not covered in this course)

1. Pulmonary Ventilation

Air flow is similar to blood flow

Play with me

Pressure and Volume Relationships

• Gasses move from areas of high pressure to areas of low pressure until equilibrium is reached

• Boyle's Law: Pressure of a gas is inversely proportional to it's volume

• P1V1 = P2V2Robert Boyle from Ireland

(1622 - 1691)Began college at age 8

when he was already fluent in Latin, Greek and French

1.0 atm 1.5 atm0.5 atm

ambient pressure = 1.0 atm

Mechanics of Breathing: Application of Boyle’s Law

Intrapulmonary p < atmospheric p Intrapulmonary p = atmospheric p Intrapulmonary p > atmospheric p

Mechanics of Breathing

• What causes the intrapulmonary pressure to change?

• There’s a difference between WHAT YOU DO and WHAT HAPPENS

• (True in all things, not just respiration!)

Mechanics of Breathing

• Quiet Inspiration:

• Diaphragm contracts and flattens

• External intercostals and scalene contract to elevate ribs and push sternum anteriorly

• What happens to thoracic volume? Which direction will air move?

• Quiet Exhalation:

• Diaphragm relaxes, external intercostals relax. This is passive.

• What happens to thoracic volume? Which way will air move?

Mechanics of Breathing

Deep Inhalation and Exhalation

• Forceful contraction of diaphragm and external intercostals

• Also, sternocleidomastoid and scalene muscles contract, lifting the ribs higher

• Contraction of internal and external intercostals, external oblique, rectus abdominis, transverse abdominis, internal oblique

• Active

2. Gas ExchangeIt’s all about diffusion gradients!

More Gas Laws

• Dalton's Law of Partial Pressure

• Total pressure of a gas mixture = sum of partial pressures of each gas in the mixture

• Partial pressure is written as P, subscripts designate which gas we are talking about

• Ex: P O2

• It’s like [ ] in a solution

Partial Pressures of Gas in the Blood

• Henry's Law: the volume of a gas that will dissolve in a liquid at a given temperature is dependent on

• The surface area

• The temperature

• The gas solubility

• The partial pressure of the gas

3. Gas TransportHow does oxygen and carbon dioxide actually move through the body?

• Henry's Law: the volume of a gas that will dissolve in a liquid at a given temperature is dependent on

• The surface area

• The temperature

• The gas solubility (VERY high for CO2 but very low for O2)

• The partial pressure of the gas

3a. Hemoglobin and Oxygen Transport

Hb Can Load or Unload Oxygen

• How does Hb “know” what to do?

• What factors influence Hb-O2 loading / unloading? (this makes a GREAT essay question!)

Hb + O2 HbO2deoxyhemoglobin oxyhemoglogin

Hb Can Load or Unload Oxygen

• PO2 (how much oxygen is available)

• Hb-O2 affinity (how much Hb wants to bind to oxygen molecules)

Hb + O2 HbO2deoxyhemoglobin oxyhemoglogin

3b. Carbon Dioxide Transport

• There are three ways CO2 moves from the cells to the lungs.

• as a dissolved gas (depends on PCO2) (about 7% of CO2 )

• bound to Hb (accounts for about 23% of the CO2 )

Carbon Dioxide Transport

• 70% of the CO2 is converted to carbonic acid (H2CO3) when it comes into contact w/ water:

CO2 + H2O → H2CO3

H2CO3 → H+ + HCO3-

• Given this, how does the level of CO2 affect Hb-O2 affinity?

Regulation of Breathing

• Involuntary; controlled by rhythmicity centers in the medulla oblongata and the pons.

• Activity of inspiration and expiration neurons are cyclic

• Chemoreceptors in the periphery taste the blood

So What?

UCSD HyperbaricChamber

Categories of Respiratory Disease

• Inflammatory lung disease is characterized by a high neutrophil count

• cystic fibrosis, emphysema, chronic obstructive pulmonary disease or acute respiratory distress syndrome

• Obstructive lung disease occurs when the bronchial tubes are narrowed

• chronic obstructive pulmonary disease

• asthma

• Restrictive lung diseases are due to reduced lung compliance, such as Infant Respiratory Distress Syndrome

• Respiratory Infections

• Upper: a cold, sinusitis, tonsillitis, pharyngitis, laryngitis

• Lower: pneumonia most common

Categories of Respiratory Disease

• Lung tumors (benign or malignant)

• Pleural cavity diseases (emphysema, pleurisy, pneumothorax)

• Pleural vascular disease (pulmonary embolism, pulmonary arterial hypertension, pulmonary edema)

Categories of Respiratory Disease

Smoking causes the following cancers:

• Acute myeloid leukemia• Bladder cancer• Cervical cancer• Esophageal cancer• Renal cancer• Cancer of the larynx (voice box)• Lung cancer• Cancer of the oral cavity (mouth)• Cancer of the pharynx (throat)• Stomach cancer• Uterine cancer

Smoking and Other Health Effects

Smoking is associated with the following adverse health effects:

• infertility• preterm delivery• stillbirth• low birth weight• sudden infant death syndrome (SIDS)