Respiratory System Chapter 19 Functions Exchange of gases

Respiratory System Chapter 19

Functions • Exchange of gases- O 2 in, CO 2 out • Regulation of p. H- retain or excrete CO 2 • Protect from inhaled pathogens/substances • Vocalization

Structure of the respiratory system • Assists in ventilation- inspiration/expiration • Muscles of thorax and abdomen • Upper/lower respiratory tract • Alveoli

Muscles • Creates the force to move air during breathing • Diaphragm- responsible for 45% of air that enters into the lungs

Upper respiratory system • Mouth, nasal cavity, pharynx, larynx

Lower respiratory system • Trachea, bronchi and branches, lungs • Bronchi, bronchioles, supported by cartilage rings

Lower respiratory system • Trachea, bronchi and branches, lungs • Lungs- spongy tissue, occupied by alveoli • Two lungs, surrounded by double walled pleural sac

Upper and parts of lower- functions • Warming air- maintain core body temp • Adding water vapor- epithelium doesn’t dry out • Filter out particles- foreign material doesn’t get to alveoli, mucus

Filtering out particles • Need two parts- water and mucus • Mucus is secreted by goblet cells

Alveoli • Hollow sacs, site of gas exchange • Surrounded by capillaries • 100 m 2

Ventilation • Bulk flow of air between the atmosphere and the alveoli • One respiratory cycle = inspiration followed by expiration (12 -20 per minute)

Properties of gases • Move down concentration gradient (higher to lower concentration) • Boyle’s law:

Air flow during ventilation • Due to pressure gradients – Must decrease pressure in lungs (air moves from high to lower pressure)

Involves: - contraction of diaphragm draws lungs down - -muscles contract and pull ribs up and out

Adequate ventilation • Requires compliance and elastance • Compliance- amount of force exerted to expand lungs, ability to stretch (high compliance = less force to stretch) • Elastance- resistance to being deformed

Compliance and elastance • If either are compromised, it affects air flow • Decrease in elastance- elastin fibers

Emphysema • Destroys elastin • Compliance? Elastance?

Compliance and elastance • If either are compromised, it affects air flow • Decrease in compliance • More work to stretch a stiff lung • Restrictive lung diseases

Pulmonary fibrosis • Decrease in compliance • Macrophages ingest particles, cannot be digested • Macrophages stimulate production of inelastic collagen (out of control wound healing) • Scarring of lung tissue, irreversible

It’s not just elastin the resists stretch… • Surface tension! • Alveoli have thin fluid layer between cells and air, creates surface tension which resists stretch

Adequate ventilation • Also determined by other factors: – Length of tubes – Viscosity – Diameter of tubes

Adequate ventilation • Length is constant • Viscosity

Adequate ventilation • Diameter of tubes

Measuring ventilation • Assess pulmonary function • Spirometer- volume of air moved per breath

Measuring ventilation • Four volumes – Tidal volume (quiet breathing) – Inspiratory reserve volume (forced inspiration) – Expiratory reserve volume (forced expiration) – Residual volume (air that doesn’t escape, can’t measure)

Dead space • Doesn’t take part in gas exchange

Gas Exchange and Transport

How does oxygen enter the bloodstream (and CO 2 leave)?

Concentration gradients • Gases diffuse down concentration gradients

Concentration gradients • • Gases diffuse down concentration gradients From air to water, depends on solubility too Oxygen isn’t very soluble At equilibrium, same partial pressure, concentration differs

Oxygen needs some help because of low solubility

Carbon dioxide does a bit better • More soluble in water • But, body produces more than can be dissolved in plasma • Can bind to hemoglobin too, released at lungs

CO 2 obeys same laws as O 2

Why remove CO 2? • Elevated CO 2 causes p. H disturbance (acidosis) • Can depress CNS function • Toxic to the body, so must be removed

What happens at the interface of the capillaries and the cells? • Same thing as the lungs

Chemoreceptors in arterial system monitor CO 2, and p. H levels

Non-respiratory air movements • Movement of air for something other than breathing • Clear air passages (cough/sneeze) • Vocalization and express emotion (laughing/crying)