Respiratory system

Function of the respiratory system

Primary function: obtaining O2 and removing CO2

Other functions: filter air, produce sound, sense smell

Respiration Respiration – the process of gas exchange between the atmosphere and body cells

Happens in 4 steps: 1. Movement of air into lungs (ventilation)2. Air-blood gas exchange (external respiration)3. Gas transport in blood4. Gas exchange between blood and body cells (internal respiration)

The “4U” respiration… Cellular respiration – the consumption of O2 and production of CO2 and energy at the cellular level

Pharynx

Larynx

Upper respiratory tract Nasal/oral cavity

◦ entry point for air passage

Nasal septum◦ divides the nose making 2 nostrils

Paranasal sinuses (‘sinuses’)◦ cavities within the face that reduce skull weight and

aid in voice resonation

Pharynx (‘throat’)◦ a space (not structure) where the nasal and oral

cavity meet

Epiglottis◦ flap that prevents food from entering the air passage

Lower respiratory tract Larynx

◦ top of trachea conducts air in/out of wind pipe, houses vocal chords and Adam’s apple)

Trachea (wind pipe)◦ flexible tube of cartilage (prevents collapse) that leads to

lungs

Bronchi & bronchioles◦ branched airways leading to alveoli in lungs

Alveoli◦ air sacs that form the end of bronchioles

Lungs◦ spongy organs, left (2 lobes) and right (3 lobes) contain

fluid to lubricate surfaces during breathing

Try this… Pg. 293, #1 – 6

Breathing Inspiration (inhalation):

1. Diaphragm moves downward, dropping pressure in the alveoli and forcing air into airways

2. Muscles in the chest expand, enlarging lungs even more

FYI: A newborn’s 1st breath is the hardest because its alveoli are only partially inflated

Breathing cont’d Expiration (exhalation):

1. Diaphragm relaxes, raising air pressure and forcing air out of lungs

2. Elastic recoil from alveolar surface tension purges air from sacs

3. For a deeper exhalation abdominal muscles can help squeeze lungs

Breathing is an involuntary act but the muscles are under voluntary control (eg. we can hold our breath)

Non-respiratory movements

NRMS are caused by reflexes and are used to…a) Purge airways (eg. coughing, sneezing)b) Express emotion (eg. laughter, crying)

Hiccups = sudden inhalation due to diaphragm spasms (air striking vocal folds make sound)

Yawns = we don’t know!

Respiratory measurements

Spirometry – measures the volume of air entering/exiting the lungs

4 distinct volumes1. Tidal volume

◦ volume of air entering the lungs per regular cycle

2. Inspiratory reserve volume◦ volume of air forcefully inhaled

3. Expiratory reserve volume◦ volume of air forcefully exhaled

4. Residual volume◦ volume of air remaining in lungs after forceful exhalation

Spirometer

Gas exchange◦ Gas exchange occurs in the alveoli

◦ Thin wall of alveoli separates air from a dense network of capillaries

◦ O2 and CO2 are exchanged via diffusion across this blood-air barrier

Gas exchange cont’d1. Red blood cells carrying CO2 from the

body reach alveolus

2. O2 in alveolus preferentially binds RBC, displacing CO2 which enters alveolus for exhalation

3. O2, now bound to iron-containing hemoglobin, rides RBC through body until diffusing into O2-poor cells

4. RBC now free to pick up excess CO2 for trip back to alveoli

Try this… Pg. 299, #2 – 5, 7