The Respiratory System

Section 1

5 Functions

1. Respiration

Exchange of gases: O2 & CO2 O2 is needed for cellular respiration (ATP)

2. Regulates blood pH

3. Contains receptors for smell

4. Filters inspired air

5. Sound Production

3 Stages of Respiration

1. Pulmonary Ventilation

Gas exchange between atmosphere and lungs

2. External Respiration

Gas exchange between lungs and pulmonary

capillaries

3. Internal Respiration

Gas exchange between systemic capillaries and

body cells

Structures of the Respiratory System

The Nose

Warms, moistens & filters air

Detects odor

Modifies speech vibrations

Conchae & meatuses

increase surface area

trap exhaled water droplets

prevent dehydration

Nasal Membranes

Goblet cells secrete mucus:

Moistens air

Traps debris

Cilia: tiny hairs trap debris

Blood capillaries: warm inhaled air

Sneezing:

Stimulus irritates nasal mucosa

Spasmodic contraction of respiratory

muscles occurs

Air forcefully expelled out nose & mouth

Sneezes can travel up to 200 mph

Sputum can spread 2-3 meters

The Pharynx

part of both GI Tract & Respiratory Tract

passageway for air & food

resonating chamber for speech sounds

houses the tonsils

3 regions of Pharynx:

1. Nasopharynx

2. Oropharynx

3. Laryngopharynx

Larygopharynx contains epiglottis:

flap of cartilage, covers glottis during

swallowing

glottis: opening to larynx/trachea

The Larynx

“Voice Box”

anterior to C4-C6

composed of cartilage

air passing across vocal folds & the vibration of

folds creates sound

pharynx, mouth, nasal cavity:

act as resonating chambers to give sound

human quality

muscles of face, mouth & tongue allow for

enunciation

Pitch of voice controlled by

tension on vocal cords:

Tension = Pitch

Tension = Pitch

Men have longer, thicker vocal cords:

- Vibrate more slowly: creates lower pitch

- d/t testosterone

The Trachea

“windpipe”

12 cm in length, 2.5 cm in diameter

Anterior to the esophagus

Contain 16-20 arcs of cartilage – prevents

collapse

Divides at Carina (T-5) into right & left

bronchi

Respiratory Tract

Nose

Nasal Cavity

Pharynx

Trachea

Primary Bronchi

Secondary Bronchi

Tertiary Bronchi

Lungs

Bronchioles

Terminal Bronchioles

Respiratory Bronchioles

Alveolar Ducts

Alveoli

Lungs

The Lungs Right lung: 3 lobes

Left lung: 2 lobes

Pleural membrane (2 layers) covers each lung

Pleural cavity: space between layers, contains lubricating fluid

Hilus: region where primary bronchi, blood & lymph vessels, & nerves enter or exit lung

Alveoli

Tiny air sacs

300 million!

Very thin tissue - 0.5 µm

Diffusion of gases occurs here

Contain macrophages – cells that remove

dust/debris

Alveoli secrete fluid for moisture

Contains Surfactant: lowers surface tension

of alveolar fluid to prevent alveolar collapse

Blood Supply to Lungs

Pulmonary arteries

Bring O2–poor blood to lungs from body (via heart)

Pulmonary veins

Bring O2-rich blood to heart from lungs

Bronchial arteries

Bring O2-rich blood from heart to lungs (feeds

lung tissue)

Section 2

PULMONARY VENTILATION

gases are exchanged between atmosphere

& lung alveoli

O2 in or CO

2 out

due to differences in pressure

Boyle’s Law explains how this occurs

BOYLE’S LAW

pressure of a gas varies inversely with volume

If pressure then volume

If pressure then volume

Boyle's Law at Work:

1. Diaphragm contracts (flattens)

2. Volume of lungs increases

3. Pressure in the lungs decreases

4. Air moves into lungs

After inhalation occurs...

1. Diaphragm relaxes - returns to dome shape

2. Volume of lungs decreases

3. Pressure in the lungs increases

4. Air moves out of lungs

Inhalation is an active process:

It requires muscle contraction & ATP

Exhalation is a passive process:

It does not require muscle contraction & ATP

External Respiration

exchange of O2 and CO2 between alveoli

and blood in pulmonary capillaries

occurs by passive diffusion

controlled by 2 gas laws:

1. Dalton’s Law

2. Henry’s Law

Dalton’s Law

each gas in a mixture of gases exerts its own pressure as if all the other gases were not present

This is its partial pressure (Px)

ex: atmospheric air is made of N2, O2, H2O, CO2, & other gases

PN2 + PO2 + PH2O + PCO2 + Pother = 760 mm Hg

760 mm Hg = total atmospheric pressure

How does this relate to respiration?

**The gases will diffuse from the area of higher

pressure to the area of lower pressure

ex: if O2 is in alveoli & in blood:

O2 will diffuse across the alveoli and into

the blood

Henry’s Law

the quantity of a gas that will dissolve in a liquid is

proportional to the partial pressure of the gas and its

solubility coefficient

partial pressure, solubility = gas in solution

How does this relate to respiration?

Oxygen crosses into blood because:

PO2 (alveolar air) = 105 mmHg

PO2 (deoxygenated blood in pulmonary capillaries) = 40 mmHg

So O2 moves from alveoli to blood

Carbon Dioxide crosses into alveoli because:

PCO2 (deoxygenated blood in pulmonary capillaries) = 45 mm Hg

PCO2 of alveolar air is 40 mm Hg

So CO2 moves from blood to the alveoli

The RATE of Gas Exchange depends on:

1. Partial pressures of gases

2. Surface area for gas exchange

area = rate of exchange

3. Diffusion distance

distance = rate of exchange

INTERNAL RESPIRATION

exchange of gases at the cellular level

(Dalton’s Law applies)

O2 leaves blood and diffuses into cell

CO2 leaves cells and diffuses into blood

O2 Transport

O2 does not dissolve well in water

Transportation requires Hemoglobin

Hemoglobin = iron-rich protein that turns

bright red when combined w/ O2

1 Hemoglobin + 4 O2 = Oxyhemoglobin

CO2 Transport Dissolves well in water

most found in blood as bicarbonate ions

blood detects this & transports it to lungs to be

exhaled

controls rate of breathing:

ions = resp. rate

ions = resp. rate

Medulla oblongata – part of brain that controls

respiratory rate

Lung Volumes

Adult = 12 breaths/min

Tidal volume: volume of one breath, ~ 500 ml

Spirometer: device used to measure volume of

respiration

Residual Volume: air that remains in lungs after maximum exhalation (~1200 ml)

Prevents lung collapse

Can’t be measured w/ spirometer