Why a respiratory system?

• Need O2 in

– for cellular respiration– make ATP

• Need CO2 out

– waste product

O2

food

ATP

CO2

Passageways and Lungs• Respiratory system consists of a pair of lungs & a

system of tubes that carry air to them• Breathing is just one of the functions that the

respiratory system carries out

The path air takes• Air enters

through the nasal cavity – It passes

through the pharynx and larynx into the trachea

The path air takes– The trachea

forks to form two bronchi

– Each bronchus branches into numerous bronchioles

• The bronchioles end in clusters of tiny sacs called alveoli- 1 cell layer thick wall

Lungs• Structure

spongy texture • high surface area• more absorption of O2

– alveoli • small air sacs

– moist lining• mucus traps dust,

pollen, particles– covered by cilia

• hair-like extensions of cells• move mucus upward to

clear out lungs

Moving gases into bloodstream• Inhale

– O2 passes from alveoli to blood

– by diffusion• Exhale

– CO2 passes from blood to alveoli

– by diffusion

capillaries(circulatory system)

Gas exchange: Diffusion of gases• Gases move by diffusion from high to low

concentration– capillaries are thin-walled tubes of circulatory

system– alveoli are thin-walled sacs of respiratory system

blood lungs

CO2

O2

CO2

O2

blood body

CO2

O2

CO2

O2

capillaries in lungs capillaries in muscle

External respiration: exchange of gases between alveoli and blood

Internal respiration: exchange of gases between blood and cells

The Mechanics of Breathing• Breathing ventilates the lungs• The action of your diaphragm and the muscles between

your ribs enable you to breathe in and breathe out• Breathing is the alternation of inhalation (active) and

exhalation (passive)

Control of Respiration

• Breathing is usually an involuntary process

• Partially controlled by an internal feedback mechanism that involves signals being sent to the medulla oblongata about the chemistry of your blood

– measure blood pH• CO2 = pH (acid)

Control of Respiration

– coordinate breathing, heart rate & body’s need for energy

• Will send nerve signals to the rib muscles and diaphragm

• Nerve signals cause these muscles to contract, and you inhale

Breathing and Homeostasis

• Homeostasis– keeping the internal environment

of the body balanced– need to balance O2 in and CO2 out

– need to balance energy (ATP) production O2

ATP

CO2

Breathing and Homeostasis

• Exercise– breathe faster

• need more ATP• bring in more O2 & remove more

CO2

• Disease– poor lung or heart function =

breathe faster• need to work harder to bring in

O2 & remove CO2

O2

ATP

CO2

Cleaning dirty air

• To prevent foreign material from reaching the respiratory system is lined with ciliated (hair) cells that secrete mucus

• The cilia constantly beat upward in the direction of your throat, where foreign material can be swallowed or expelled by coughing or sneezing