Every eukaryotic cell needs oxygen.

So the big question is...

Small Organisms (single or few cells)

• Single-celled organisms can simply absorb Oxygen from the environment through diffusion

• No circulatory or pulmonary system needed

Just a large surface area that is moist is all that is needed.

Complex Water Organisms• Water is a more efficient

exchange medium for Oxygen (than air)

• But Water has a lower percentage of Oxygen dissolved in it (than air)

• Gills develop to maximize surface area– Constant circulation of

water

– Water is difficult to move

• Bulk Flow now necessary

Complex Land Animals• Air is a less efficient means of

absorbing Oxygen than water

• Air has a higher percent of Oxygen than water

• Lungs evolve to maximize surface area– S.A. of tennis court

– Intercostal/diaphragm muscles allow periodic exchange

• Bulk Flow also necessary

The 4 steps of Respiration in Mammals1. Air or water, containing oxygen, is moved past a respiratory surface by bulk flow.

2. O2 and CO2 are exchanged through the respiratory surface by diffusion. O2 enters the capillaries and CO2 is removed.

3. Gases are transported between the respiratory system & the tissues by the bulk flow of blood (pumped by the heart)

4.Gas exchange between tissue and circulatory system. O2 diffuses out of capillaries and CO2 diffuses into them.

Diffusion = movement of particles from a region of high concentration to one of low

concentration.

Bulk flow = movement of many particles from an area of higher pressure to one of lower pressure

Diffusion of O2 and CO2

• When a cell carrying O2 nears another cell that is lacking in O2, diffusion will occur

• When a cell is lacking in O2 and nears an O2 rich region, diffusion will occur

• The same process happens with CO2

Summary of diffusion in the lungs and tissue

The next question is...

So now we understand how this diffusion works between neighboring cells

• A liquid conduit containing the liquid “blood”

• This Bulk Flow is necessary to bring O2 to every cell in the body

• Also necessary to protect and upkeep cells

• The liquid that is circulated around has a number of components...

Transporting O2 and other stuff(The Circulatory System)

The Components of Blood

• Red Blood Cells:– Transport O2

• White Blood Cells:– Protect the cells from

infection/invasion

• Platelets:– Clot the blood to prevent it from

spilling out when a rupture of the fluid conduit occurs

• Plasma:– Glucose, hormones, etc.

suspended in a viscous goo

Functions of Blood

1. Transportation: Blood transports oxygen, carbon dioxide, nutrients, hormones, heat, and wastes.

2. Regulation: Blood helps regulate pH, body temperature, and water content of cells.

3. Protection: Protects against blood loss through clotting, and against foreign microbes and toxins through the activities of phagocytic white blood cells and plasma proteins.

Red Blood Cells

• Have a protein called “Hemoglobin” which binds to O2

• Binds to CO much more strongly

• Contain no nucleus!• Recycled every week or so• Biconcave shape

Oxygen atoms bond to the heme

Each can hold 4 o

White Blood Cells• Slip in between cells• Recognize and destroy foreign matter

Platelets• Aid in blood clotting• Recognize micro tears in blood conduits and

bind together to form a clot

How blood is transported• Arteries:

– Structures that carry blood away from the heart

– Rigid to take pressure of blood right out of heart

• Veins:– Looser to expand more– Store great quantities of blood

• Capillaries:– Very narrow tubes between arteries

and veins where diffusion occurs

How Blood Flows:The Heart

The Heart

• Contraction of ventricles – Larger of heart chambers

– Takes blood in from the atria

– Pumps blood out to the body

• Contraction of atria– Smaller chambers

– Takes blood in from body

– Pumps blood into the ventricles

• Coordinated beating of one then the other