THE RESPIRATORY SYSTEM

Structure• Air enters the lungs through one of 2 passages

• The nose• The mouth

• After entering, air travels through the pharynx (throat), past the epiglottis (the structure that stops food entering the windpipe), and through the larynx (voice box)

• Next, it travels through the trachea (windpipe)

• The trachea leads to the bronchi • There are 2 branches, one leading to each lung

• Once in the lung, the air travels through bronchioles

• The bronchioles terminate at the alveoli

Function

• The internal respiratory structures are lined with ciliated cells that secrete mucous• The cilia “sweep” substances up and out of the respiratory tract

• They are expelled through sneezing/coughing or pushed past the epiglottis to enter the digestive tract

• The mucous traps the particles

• The alveoli exchange carbon dioxide and oxygen• Deoxygenated blood from the right ventricle is sent to the lungs from

the heart via the pulmonary artery• This blood passes through a series of capillaries in the alveoli, where carbon

dioxide diffuses out while oxygen defuses in• The oxygenated blood returns to the left ventricle of the heart via the pulmonary

vein • The oxygenated blood can then deliver the oxygen to the cells of the body

Cellular Respiration (Yep, it’s back)• Animals, including humans, need oxygen and sugars to make

energy (ATP) for the cells• As a byproduct of cellular respiration, cells produce carbon dioxide

• The actual number of ATP varies

Gas Exchange

•The carbon dioxide produced in cellular respiration is useless to you• It diffuses from the cells into blood• It binds to hemoglobin in the blood, and is transported back to the lungs• In the alveoli of the lungs, the carbon dioxide diffuses out

• When you exhale, the carbon dioxide is released

•When you inhale, air enters the lungs •Air is composed of 78% Nitrogen and 21% oxygen

• Oxygen is highly reactive, and so binds to hemoglobin• It enters the blood stream and goes back to the left atrium

• The nitrogen is nonreactive, so does not bind to hemoglobin • It is immediately breathed out

Breathing Process •Breathing is an involuntary process

•The Autonomic Nervous System (Parasymphetic Nervous System) controls it• The brain stem conducts an impulse across neurons to your

diaphragm when cells in your heart detect too much carbon dioxide or not enough oxygen in the lungs

•The diaphragm is a muscle beneath (inferior to) your lungs• It controls breathing by relaxing and contracting

Inhaling

• Inhalation is the result of the diaphragm contracting and moving downward

• This, along with contraction of muscles in your ribs, increases the area in your chest, allowing lungs to expand

•WARNING: PHYSICS AHEAD!•Boyle’s Law relates pressure and volume: •As the volume increases, the pressure decreases

• The atmospheric pressure is now greater than the pressure in the lungs• Gas moves to the area of lesser concentration (concentration gradient)

•This causes the lungs to fill up with air

•Your lungs do not “pull” air in

Exhaling

• Once your body senses that it has enough oxygen or too much carbon dioxide, the autonomic nervous system signals you to exhale• The diaphragm relaxes, moving up• The muscles in the ribs relax, pulling them closer

• These processes decrease the volume of the lungs, pushing the gas out

• You do forcefully expel gases during exhalation, but the lungs do not “push” it out

Hiccups

• Interestingly, everyone has a lifelong “hiccup pattern”• You usually do not deviate from it

• Irritation of the nerves that control the diaphragm can cause it to spasm• The spasm causes a quick intake of breath, followed by a quick closing of the

epiglottis • This causes the familiar hiccup sound

• Causes include:• Being too full, either from food or swallowing too much air

• A full stomach pushes on the nerves, putting pressure on them• Spicy foods which irate the nerves• Rapid temperature changes of the stomach (drinking a cold or hot beverage)• Emotions/stress can irritate the nerves

Smoking

• Smoking causes inhalation of nicotine, which diffuses from lungs into blood• Nicotine binds to hemoglobin even better than oxygen does• So does the carbon monoxide in cigarette smoke

• These limit the availability of hemoglobin molecules that are able to carry oxygen

• Blood also carries these dangerous chemicals throughout the body, harming the veins and arteries

• Additionally, smoking destroys the cilia in the respiratory tract (leads to smoker’s cough-trying to get debris out)

• Smoking damages the alveoli, limiting their ability to transfer gases

• Do not do it!!!!!!!!