Respiratory System

Function of the respiratory system

Transport air into and out of the lungs

Allow O2 to diffuse from the lungs into the bloodstream

Remove CO2 from the bloodstream and expel it from the body

Non-vital function

Detecting odours

Speech production

Respiration system

Respiration system can be divided into 2 zones

• Conducting zone

• Respiratory zone

Conducting zone

Includes the organs and structures that transport air to the lungs but are not directly involved in gas exchange

Respiratory zone

Where gas exchange occurs

Includes:

• Respiratory bronchioles

• Alveolar ducts

• Alveoli

These structures allow O2 and CO2 to diffuse between the lungs and the bloodsteam

The journey of air

Nasal cavity → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli

Each structure has specialised features that help prepare air for gas exchange

Nasal cavity

Air usually enters the respiratory system through the nostrils, which lead into the nasal cavity

Nasal cavity functions

• Filters the air

• warm the air

• Moistens the air

These processes protect the delicate tissues of the lungs

Structure of the nasal cavity

Divided into 2 chambers by nasal septum

Inside the nasal cavity are thre curved bony structures called nasal conchae ( turbinates )

These structures:

• Increase the surface area

• Create turbulence in airflow

• Allow air to contact the lining of the nasal cavity

This improves the filtering, warming, and moistening of air

The nasal cavity also contains paranasal sinuses, which are air-filled spaces within the surrounding bones that help warm and misten incoming air

Nasal cavity lining

Lined with a mucous membrane containing specialised calls.

Goblet cells produce mucus, which traps:

• Dust

• Pollen

• Microorganisms

Cilia which are hair-like projections that beat continously, moving mucus and trapped particles toward the throat where they can be swallowed

Blood supply

A dense network of capillaries beneath the lining helps warm incoming air

Oral cavity ( mounth )

Air can also enter through mouth:

• Not filtered as effectively

• Not warmed as efficiently

• Not moistened as well

Pharynx ( throat )

A muscular passageway that connects the nasal cavity to the larynx

It allows the passage of:

• Air

• Food

• Liquids

Nasopharynx ( region of the pharynx )

Located behind the nasal cavity

Lined with ciliated mucous membrane

Cilia move mucus and trapped particles toward the throat

Oropharynx ( region of the pharynx )

Located behind the nasal cavity

Lined with ciliated mucous membrane

Cilia move mucucs and trapped particles toward the throat

Laryngopharynx ( region of the pharynx )

The lowest region of the pharynx

Directs air toward the larynx

Directs food and liquids toward the oesophagus

Larynx ( voice box )

Made of 9 cartilages

Epiglottis is one of the cartilages and is composed of elastic cartilage

Epiglottis is a flap of elastic cartilage:

• Closes over the larynx during swallowing

• Prevents food and liquid from entering the airway

The lining of the larynx contains cilia and mucus- secreting goblet ells, which trap and remove debris

Larynx functions

• Keeps the airway open

• Produces sound

Trachea ( windpipe )

Carries air from the larynx to the bronchi

It is supported by 18-20 C-shaped rings of cartilage

These rings:

• keep the airway open

• prevent the trachea from collapsing

The open side of the cartilage rings contains smooth muscle, which allows the trachea to slightly change diameter

The lining of the trachea contains:

• Goblet cells that produce mucus

• Cilia that move mucus upward toward the pharynx

→ Remove dust and pathogens

Bronchi

Lower end of the trachea, it divides into 2 tubes called the bronchi

The right bronchus enters the right lung

The left bronchus enters the left lung

Contain:

• Cartilage for structural support

• Ciliated epithelium

• Mucus-producing goblet cells

Bronchial tree

Once inside the lungs, the bronchi divide repeatedly into smaller branches, forming the bronchial free

The main bronchi branch into lobar bronchi, each supplying a lobe of the lung

The right lung has 3 lobes

The left lung has 2 lobes

The left lung has fewer lobes due to the position of the heart

Bronchioles

The bronchi continue to divide into smaller tubes called bronchioles:

• Approximately 1mm in diameter

• Branch into smaller terminal bronchioles

• Don’t contain cartilage

• Have smooth muscle in their walls

Can contract, relax, controlling airflow through the lungs