1. The Respiratory System

2. The Respiratory System
Functions to exchange gases (CO2 and O2) with the cardiovascular system
Mostly occurs in the lungs
Two types of respiration:
External Respiration: the exchange of gases between the atmosphere and the blood
Internal Respiration: the exchange of gases between the blood and the cells of the body
O2 is needed to make ATP in cellular respiration.
CO2 is a waste byproduct of cellular respiration and is toxic to cells. It needs to be removed.

3. Lungs The site of gas exchange between the atmosphere & blood
The right lung has 3 lobes, the left has 2
Surrounded by the ribs
The diaphragm is a muscle just below the ribs that aides breathing
It is located in the thoracic cavity
The thoracic cavity is lined with Pleura:
They are membranes that line the thoracic cavity and cover the lungs.
They decrease friction.

4. The Path of Air
Step 1
External respiration starts at the mouth and nose
Hairs in the nose filter out bigger particles (turn them into boogers)
Walls of the nasal cavity have mucus membranes
They warm and moisten the air, which prevents damage to delicate nasal tissues
Walls of the nasal cavity also have cilia
The cilia trap smaller particles and sweep them into the throat, where they are swallowed.

5. The Path of Air Continued
Step 2
Moistened, filtered air heads into the pharynx (throat)
It’s a tube at the back of the nasal cavities and mouth
It is a passageway for food and air
Step 3
The epiglottis allows air to head into the trachea (windpipe)
More cilia cover its walls, sweeping more particles and mucus toward the throat
The epiglottis is flap of tissue to cover airway when swallowing food down esophagus - It is made of cartilage

6. The Path of Air Continued
Step 4
The larynx (voice box) is at the upper end of the trachea
Sound is produced when air is forced past 2 ligaments called vocal cords, causing them to vibrate and create sounds

7. The Path of Air Continued
Trachea branches into 2 bronchi, each of which lead into a separate lung
They are lined with more cilia and mucus for more filtration.
Inside the lung, bronchi branch into smaller bronchioles
Bronchioles end in clusters of tiny air sacs called alveoli
Capillaries surround each alveolus
ALL exchange of gases in the lungs occur in the alveoli.
The large number of capillaries and alveoli give the lung a huge surface area with which to exchange gases.
300 million alveoli have a total surface area of 70 m2.

8. Gas Exchange at the Lungs
When air enters lungs, O2 crosses alveolar membranes & capillary walls and enters blood
CO2 moves in opposite direction
O2 is carried by hemoglobin on red blood cells.
When oxygenated blood reaches areas of low oxygen concentration, hemoglobin releases oxygen to cells.
crossing from capillary through alveolar membrane and is released from lungs out to the world
Substances move from area of high concentration to areas of low concentration!

9. Movement of CO2 Concentration of CO2 is higher in cells
CO2 moves from cells (high concentration) to blood (low concentration)
Video: Every Breath You Take
It is a waste product of cellular respiration
Some is carried in plasma.
Some binds to hemoglobin.
70% is carried as bicarbonate.
A chemical reaction occurs between CO2 & water forming carbonic acid which breaks down into bicarbonate.
In lungs reaction is reversed: bicarbonate combines with H+ to form carbonic acid which forms water and CO2 is exhaled.

10. How to Breathe Inspiration: inhaling air Chest expands
Muscles contract to move ribs up and out
Diaphragm flattens and pushes DOWN, on abdomen
Volume of lungs increases
Air pressure in lungs decreased
Air moves into lungs
Air pressure in lungs is lower than outside

11. How to Breathe Expiration: releasing air
Ribs and diaphragm muscles relax
Diaphragm pushes UP on lungs
Elastic lung tissues recoil
Lungs deflate
Volume decreases
Air pressure inside is greater than air pressure outside
Forces air out of lungs until pressures are equal

12. Regulation of Breathing
Rate of oxygen use depends on cell activity
More activity = more oxygen = more breathing
Rate of breathing controlled by brain.
Monitors concentration of CO2 in blood
Increased activity, increased CO2 in blood stimulates nerve cells in brain
Brain tells diaphragm to increase breathing rate and depth
When CO2concentration returns to normal, breathing slows
This whole process is autonomic