The Respiratory System

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.

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.

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.

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

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

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.

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!

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.

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

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

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