Human Gas Exchange System

What is the human gas exchange system

The lungs and air passages that allow oxygen into blood and carbon dioxide out of blood

What is the function of gas exchange system

To exchange oxygen and carbon dioxide between air and blood

Where are the lungs located

In the thoracic cavity inside the rib cage

Why are lungs inside the body

To protect them and reduce water loss

What is the pathway of air in the respiratory system

Trachea bronchi bronchioles alveoli

What is the function of the trachea

To carry air to the lungs

What is the function of bronchi

To carry air into each lung

What is the function of bronchioles

To carry air to alveoli

What are alveoli

Small air sacs where gas exchange occurs

What is ciliated epithelium

Airway lining containing cilia and goblet cells

What is the function of goblet cells

To produce mucus

What is the function of mucus in airways

Traps dust and microbes

What is the function of cilia

To move mucus towards throat

What is meant by cilia action

Beating movement that wafts mucus upwards

What happens to mucus after it is moved up airways

It is swallowed

Why are goblet cells important

They trap pathogens and particles

Where is ciliated epithelium found

Trachea bronchi and larger bronchioles

What is the structure of the trachea

Tube with cartilage rings smooth muscle elastic tissue and ciliated epithelium

What is the function of cartilage in trachea

Prevents airway collapse

What is the shape of cartilage in trachea

C shaped rings

Why are tracheal cartilage rings incomplete

To allow food to pass through oesophagus

What is the function of smooth muscle in airways

Controls airway diameter

What does contraction of smooth muscle do

Reduces airway diameter

What does relaxation of smooth muscle do

Increases airway diameter

What is elastic tissue function in airways

Allows stretching and recoiling during breathing

What is the structure of bronchi

Two main branches of trachea with cartilage smooth muscle and ciliated epithelium

What is the function of bronchi

Carry air into each lung

What is the structure of bronchioles

Small airways with smooth muscle and elastic tissue

Why do bronchioles have no cartilage

So they can change shape and control airflow

What is the epithelium in bronchioles

Simple squamous epithelium in small bronchioles

Why is squamous epithelium thin

To reduce diffusion distance

What are alveoli

Clusters of air sacs at ends of bronchioles

What is the function of alveoli

Gas exchange between air and blood

What gas moves into blood in alveoli

Oxygen

What gas moves out of blood in alveoli

Carbon dioxide

What is alveolar wall made of

One layer of squamous epithelial cells

Why are alveoli walls thin

To reduce diffusion distance

What is the role of capillaries around alveoli

Bring blood for gas exchange

What is pulmonary artery function

Brings deoxygenated blood to lungs

What is pulmonary vein function

Brings oxygenated blood to heart

What is pulmonary capillary function

Site of gas exchange

What is diffusion direction of oxygen

Oxygen from alveoli to blood

What is diffusion direction of carbon dioxide

from blood to alveoli

What maintains diffusion gradient in alveoli

Ventilation and blood flow

Why is ventilation important in alveoli

Replaces air to maintain concentration gradient

What is the surface area adaptation of alveoli

Many alveoli increase total surface area

Why do alveoli have large surface area

To increase rate of gas exchange

What is the role of elastic fibres in alveoli

Allow stretching and recoil during breathing

What is the role of collagen in alveoli

Prevents over stretching and bursting

Why are alveoli moist

To allow gases to dissolve before diffusion

What is surfactant function

Helps keep alveoli inflated and reduces surface tension

What is capillary wall thickness

One endothelial cell thick

Why are capillary walls thin

To reduce diffusion distance

How are red blood cells adapted in capillaries

Pressed close to capillary wall to reduce diffusion distance

Why is slow blood flow important in lungs

Allows more time for gas exchange

What is haemoglobin role in lungs

Binds oxygen to form oxyhaemoglobin

What happens to carbon dioxide in lungs

It diffuses from blood into alveoli

What is the main adaptation of alveoli

Large surface area thin walls good blood supply and ventilation

What is the function of respiratory system overall

Gas exchange between air and blood

What is the role of thorax in breathing

Protects lungs and supports breathing movement

What is squamous epithelium

Thin flat cells forming exchange surface

Why are alveoli not open to air directly

To protect them and maintain internal conditions

What is the order of airway structures

Trachea bronchi bronchioles alveoli

What is the role of mucus in infection defence

Traps pathogens before they reach lungs

What is the role of cilia in infection defence

Remove mucus containing pathogens

What is meant by diffusion in lungs

Movement of gases from high to low concentration

What is partial pressure gradient

Difference in gas concentration driving diffusion

What is key requirement for gas exchange surfaces

Large surface area thin barrier and steep gradient

What is the role of rib cage

Protects lungs and assists ventilation

What is the role of diaphragm

Changes volume of thorax for breathing