The Respiratory System

System Overview• Includes tubes that remove

particles from incoming air and transport air in and out of the lungs

• Microscopic air sacs for gas exchange

• Organs include:– Nose, nasal cavity, and

paranasal sinuses– Pharynx– Larynx– Trachea– Bronchial tree– Lungs

Steps of Respiration

• Respiration = the process of gas exchange between the atmosphere and body cells

1. Ventilation2. Gas exchange between blood and air in

lungs3. Gas transport between lungs and body

cells4. Gas exchange between blood and body

cells

Upper and Lower Respiratory Tracts

• Upper Respiratory Tract– Organs located outside

the thorax

• Lower Respiratory Tract– Organs located within

the thorax

The Nose• Supported by bone and

cartilage• Nostrils• Nasal cavity• Nasal septum• Nasal conchae

– Support mucous membranes

– Pseudostratified columnar epithelium and goblet cells

– Extensive network of blood vessels to warm air

Paranasal Sinuses

• Air-filled spaces within:– Maxillary bones

– Frontal bone

– Ethmoid bone

– Sphenoid bone

• Reduce skull weight • Resonance chambers

Pharynx

• Behind the oral cavity and between the nasal cavity and the larynx

• Passageway for food and air

• Helps produce speech

Larynx

• Enlargement at the top of the trachea and below the pharynx

• Conducts air in and out of the trachea

• Prevents foreign objects from entering trachea

• Houses vocal cords• Epiglottis

Vocal Cords• Horizontal folds of muscle and

CT with a mucous membrane covering

• False vocal cords• True vocal cords• Speech is formed by changing

the shape of the pharynx and oral cavity– Words formed by the tongue and

lips– Loudness– Pitch

• Glottis

Trachea • AKA windpipe• Extends in front of the

esophagus and into the thoracic cavity

• Splits into left and right bronchi

• Ciliated epithelium and goblet cells– Filters incoming air– Sweeps particles out into

pharynx

• 20 hyaline cartilage rings• Soft tissue on posterior

esophagus can expand as food is swallowed

Bronchial Tree

• Branched airways leading from trachea to lungs

• Structurally similar to trachea with less cartilage

• Mucous membranes filter incoming air and distribute air to alveoli

Passage of Air Though the Bronchial Tree

• Primary bronchi secondary bronchi bronchioles alveolar ducts alveoli

Lungs• Soft, spongy, cone-shaped

organs in thoracic cavity• Lungs separated by the

heart• Enclosed by thoracic cage

and diaphragm• Suspended from bronchi

and some large blood vessels

• Right lung (3 lobes) is larger than left (2 lobes)

• Visceral pleura

Alveoli• Microscopic air sacs• Clustered at distal ends of

alveolar ducts• Consist of tiny spaces

within simple squamous epithelium walls

• Dense capillary network• Large surface area for gas

exchange• Surfactant

Breathing

• Breathing consists of 2 processes:1. Inspiration (inhalation)2. Expiration (exhalation)

• Air moves into the lungs because of atmospheric pressure.

• When lung pressure is lower than atmospheric pressure because of diaphragm and intercostal muscle contractions inspiration

• When muscles relax and lungs and thoracic cage return to normal size expiration

Control of Breathing• Controlled by the

respiratory center of the medulla oblongata and the pons

• May also be affected by – Chemicals in body fluids

(CO2, H+, O2)– Degree to which lung tissue

stretches– Emotional state– Hyperventilation