Gas Exchange in Vertebrates

• Gas exchange refers to the physical methods that organisms have for obtaining oxygen from their surroundings and removing excess carbon dioxide.

Gas Exchange

• Why must organisms carryout gas exchange?

• Organisms that carry out the process of aerobic respiration require oxygen to break down and obtain energy from nutrients like glucose.

C6H12O6 +O2 (g) CO2 (g) + H2O(l) + Energy

Respiratory Surfaces

• In order for oxygen to enter an organism it must first pass through a respiratory surface. Respiratory surfaces have several characteristics:

1. The surface must be very thin

2. The surface must be moist. This is due to the fact both oxygen and carbon dioxide must be dissolved in water.

Respiratory Surfaces

3. It must be in contact with a source of oxygen in the environment

4. In large multicellular organisms such as humans, the surface, must be in contact with a transport system that will be able to carry these gases to and from the cells.

5. Land living, air breathing organisms such as humans, have their respiratory surfaces inside the body. This internal surface is important for protection and the reduction of evaporation of the moist surface.

Respiratory Surfaces

• How do gases cross the respiratory surfaces?

– The external side of the respiratory surface has a high concentration of oxygen compared to the internal side. Therefore Oxygen will diffuse across the surface and into the transport system. The opposite is true of carbon dioxide.

– The larger the surface area of the respiratory surface, the faster the rate of diffusion of gases across it.

The Human Respiratory System

• The human respiratory system consists of the lungs and the systems of air tubes that carry air to and from the lungs.

Air Pathway

Nose Pharynx Larynx Trachea Bronchi Bronchiole Tubes Bronchioles Alveoli

Nose

• Air normally enters the respiratory tract through the nostrils, it then enters spaces called the nasal passages.

The Nose

The nose has three main functions:

1. Filters the air - hair at the opening of the nasal passages

traps foreign particles.

- nasal passages are lined with mucus producing cells and cilia that work to trap foreign particles.

Nose

2. Moistens the air - Mucous works to moisten the air (moist air will diffuse faster

into the blood stream than colder air

3. Warms the Air - Just below the mucous membranes of the nasal passages are

many tiny capillaries. The blood flow through the capillaries works to warm the air.

- Warm air diffuses across the surface of the lungs at a faster rate than cold air

Pharynx and the Larynx

Pharynx and the Larynx

• From the nasal passages the air enters the pharynx which is also called the throat.

• air leaving the pharynx enters the larynx (also called the voice box). The larynx contains the vocal cords. The vocal cords are membranes stretched over the pharynx that vibrate as air passes over them.

• The epiglottis prevents food from entering the larynx when we swallow

Trachea

Trachea

• Also called the windpipe • 12 cm long, 2.5 cm in diameter • composed of rings of cartilage that ensure that

the windpipe always remains open.

• Lined with ciliated mucous membrane. The sweeping action of the cilia move debris upwards into the pharynx, here they are either swallowed or coughed out.

Bronchi

Bronchi

• Two bronchi branch from the trachea

• Composed or cartilage rings and are lined with ciliated mucous membranes

• Branch in a tree-like fashion into numerous bronchiole tubes located with in the lungs

Bronchioles

• Bronchi tubes branch into increasingly smaller and thinner tubes called bronchioles

Alveoli

Alveoli

• Each bronchiole ends in tiny air sacs called alveoli

• There are thought to be 300 million alveoli in the lungs

• Alveoli are one cell thick and surrounded by many capillaries

• The alveoli are the structures through which gases are exchanged between the lungs and the blood

• Tremendous surface area = tennis court

Lungs

• The gas exchange organs in humans and other vertebrate animals.

Lungs

• Fill a large part of the chest cavity and are separated from the chest cavity by a large muscle called the diaphragm.

• Surrounded by a two layer membrane called the pleura.