Respiratory System

2.17.10

Respiratory System

Mechanics of Breathing• Breath in…what muscle are you contracting or relaxing?

Mechanics of Breathing• Inspiration (breathing in):

– Diaphragm contracts downwards– Exterior intercostal muscles contract up, pulling ribs and sternum out– Both actions lower pressure in lungs by creating space in chest cavity– Air rushes in due to lower air pressure

Mechanics of Breathing

• Expriation (breathing out):– Diaphragm and other

associated muscles relax– Space inside chest cavity

decreases– Air rushes out due to rising

air pressure inside lungs

Air Pathway

• Air enters the pharynx, where a flap of skin known as the glottis blocks food and liquids

Air Pathway

• Trachea leads to two bronchi, which fork into many hundreds of bronchioles, leading to millions of alveoli

Alveoli

• ~600 million alveoli in human lungs

• Site of gas exchange• Single-cell walls allow

for O2 and CO2 to pass between blood and air inside alveoli

• Covered in capillaries

Respiration at a Glance

Blood Basics

• Plasma--fluid portion of the blood (55%)

• Cells (45%)– Erythrocytes--red blood cells; responsible for oxygen

distribution– Leukocytes--white blood cells; responsible for “cleaning”

the system of foreign invaders– Thrombocytes--platelets; responsible for blood clotting

• Serum--liquid that separates from the blood when a clot is formed

Human Blood

• Red blood cells - 5 to 6 million per mm3, no nucleus

• White blood cells - Larger but less numerous, 5 to 10,000 per mm3

• Platelets - Tiny, cellular fragments 350 to 500,000 per mm3

Animal Blood

• Animal blood has large red blood cells with nuclei

Circulation•Venules•Arteries•Capillaries•Arterioles•Veins

Circulation1. Arteries (blood

away from heart)2. Arterioles

(smaller, branched arteries)

3. Capillaries (smallest vessels, very thin to allow gas exchange)

4. Venules (collect blood from capillaries)

5. Veins (blood back towards the heart)