Gas Exchange and Gas Exchange and BreathingBreathing

Characteristics of a Gas Exchange SurfaceCharacteristics of a Gas Exchange Surface

Structure and Functioning of the Gas Structure and Functioning of the Gas Exchange SystemExchange System

The Need for Gas Exchange and VentilationThe Need for Gas Exchange and Ventilation In humans OIn humans O22 is used in cell respiration (in cytoplasm and is used in cell respiration (in cytoplasm and

mitochondria) and COmitochondria) and CO22 is released is released

Gas exchange happens in the alveoli of human lungs: OGas exchange happens in the alveoli of human lungs: O22 diffuses from the air into the alveoli to blood capillaries, diffuses from the air into the alveoli to blood capillaries, COCO22 diffuses in opposite direction diffuses in opposite direction

A ventilation system maintains a high conc. Of O2 in the A ventilation system maintains a high conc. Of O2 in the alveolialveoli

Ventilation in humans is produced by changes in pressure Ventilation in humans is produced by changes in pressure in the chest cavity. Changes in pressure are carried out by in the chest cavity. Changes in pressure are carried out by the action of two sets of muscles in the breathing the action of two sets of muscles in the breathing apparatus: diaphragm and the intercostal musclesapparatus: diaphragm and the intercostal muscles

How are alveoli adapted to gas How are alveoli adapted to gas exchange?exchange?

Adaptations of the alveoli to gas exchangeAdaptations of the alveoli to gas exchange Alveoli are small (~100 um in diameter) but the Alveoli are small (~100 um in diameter) but the lungs contain lungs contain

hundreds of millions of alveolihundreds of millions of alveoli (huge overall surface area for (huge overall surface area for gas exchange)gas exchange)

Walls of the alveoli and capillaries consist of a single layerWalls of the alveoli and capillaries consist of a single layer The The capillariescapillaries surrounding the alveoli contain high CO surrounding the alveoli contain high CO22 and and

low Olow O22 concentration concentration Cells in the alveolus secrete a fluid which helps keep the walls Cells in the alveolus secrete a fluid which helps keep the walls

moist facilitating gas diffusionmoist facilitating gas diffusion The walls of the alveoli produce a natural detergent that The walls of the alveoli produce a natural detergent that

prevents the walls from sticking together. Certain alveolar prevents the walls from sticking together. Certain alveolar cells synthesize a mixture of lipoproteins called surfactant cells synthesize a mixture of lipoproteins called surfactant (secreted into alveolar air spaces continuously, reduces surface (secreted into alveolar air spaces continuously, reduces surface tension thus decreasing tendency of alveoli to collapsetension thus decreasing tendency of alveoli to collapse

Ventilation of the LungsVentilation of the Lungs Air is inhaled into the lungs Air is inhaled into the lungs

through trachea, bronchi through trachea, bronchi and bronchiolesand bronchioles

Air is exhaled via the same Air is exhaled via the same routeroute

What are the structures What are the structures involved in gas involved in gas exchange???exchange???

Gas Exchange StructuresGas Exchange Structures StructureStructure DescriptionDescription FunctionFunction

Nostrils/Nasal Nostrils/Nasal cavitycavity

Internally supported by bone Internally supported by bone and cartilage. w/numerous and cartilage. w/numerous internal hairsinternal hairs

Entrance to the nasal Entrance to the nasal cavity; warms-up air; cavity; warms-up air; remove particles from airremove particles from air

LarynxLarynxGlottis/epiglottisGlottis/epiglottis

Top of trachea.. Composed of Top of trachea.. Composed of muscles, cartilage and elastic muscles, cartilage and elastic tissuetissue

Houses vocal cordsHouses vocal cords

Prevents foreign objects Prevents foreign objects from entering tracheafrom entering trachea

PharynxPharynx Cavity line-up by Cavity line-up by mucous epitheliummucous epithelium

Passageway of food. Passageway of food. Aids in producing Aids in producing soundssounds

TracheaTrachea Cartilage (25 c-shaped). Cartilage (25 c-shaped). Flexible, cylindrical. 2.5 cm Flexible, cylindrical. 2.5 cm dia. 12.5 cm length. In front dia. 12.5 cm length. In front of esophagus. Line-up with of esophagus. Line-up with ciliated mucusciliated mucus

Passageway of air. Passageway of air. Continues to remove Continues to remove particle of airparticle of air

Structures of the Gas Exchange Structures of the Gas Exchange System (cont…)System (cont…)

Bronchi Bronchi (bronchus)(bronchus)

Branched cartilaginous Branched cartilaginous tube. Lined-up by tube. Lined-up by mucous epitheliummucous epithelium

Conducts air form Conducts air form trachea to trachea to bronchiolesbronchioles

BronchiolusBronchiolus Branched cartilaginous Branched cartilaginous tube. Lined-up by tube. Lined-up by mucous epitheliummucous epithelium

Conducts air from Conducts air from bronchioles to alveolibronchioles to alveoli

DiaphragmDiaphragm Muscle tissue. Muscle tissue.

Dome-shapedDome-shapedInhalation and Inhalation and ExhalationExhalation

LungsLungs Contain alveoli, blood Contain alveoli, blood vessels, lymphatic vessels, lymphatic vessels and nerves of the vessels and nerves of the lower resp. tractlower resp. tract

Gas exchange Gas exchange (diffusion of gases)(diffusion of gases)

Ventilation of the LungsVentilation of the LungsINHALINGINHALINGThe external intercostal muscles The external intercostal muscles

contract, raising the ribs and contract, raising the ribs and elevating sternum elevating sternum

The diaphragm contracts becoming The diaphragm contracts becoming flatter and moving downwardsflatter and moving downwards

The muscle movements increase the The muscle movements increase the volume of the thorax. Lungs volume of the thorax. Lungs expand, partial lung pressure expand, partial lung pressure decreasesdecreases

The pressure inside the thorax The pressure inside the thorax therefore drops below therefore drops below atmospheric pressureatmospheric pressure

Air flows into the lungs from outside Air flows into the lungs from outside the body until the pressure inside the body until the pressure inside the lungs rises to atmospheric the lungs rises to atmospheric pressurepressure

EXHALINGEXHALINGThe internal intercostal muscles relax The internal intercostal muscles relax

following inhalation. Abdominal following inhalation. Abdominal organs spring back to original organs spring back to original shape, moving the ribcage down shape, moving the ribcage down and inand in

The diaphragm pushes up into a The diaphragm pushes up into a dome shapedome shape

The muscle movement decrease the The muscle movement decrease the volume of the thorax. Lungs volume of the thorax. Lungs contract, partial lung pressure contract, partial lung pressure increasesincreases

Therefore pressure inside the thorax Therefore pressure inside the thorax rises above atmospheric pressurerises above atmospheric pressure

Air flows out from lungs to outside Air flows out from lungs to outside of the body. Lung pressure falls of the body. Lung pressure falls below atmospheric pressurebelow atmospheric pressure

Self-planned laboratorySelf-planned laboratory

How does exercise affect the functioning of How does exercise affect the functioning of the heart and lungsthe heart and lungs Exercise increases cardiac outputExercise increases cardiac output

Cardiac output = stroke volume X heartrateCardiac output = stroke volume X heartrate Stroke volume = volume of blood ejected by the Stroke volume = volume of blood ejected by the

ventricles in one beatventricles in one beat