Respiratory System

Functions: 1. Deliver oxygen to the circulatory system 2. Remove carbon dioxide from the circulatory system

3 types of respiration: 1. External respiration – exchange of gases between the atmosphere and the blood

2. Internal respiration – exchange of gases between the blood and the cells of the body

3. Cellular respiration – the process by which glucose is broken down in cells to produce ATP

A. The Lungs The lungs are the sites of external respiration right lung has 3 lobes left lung has 2 lobes

Lungs are located in the thoracic cavity, encased in a protective cage of bone made up of the sternum, vertebral column, and ribs

they sit on top of the muscle called the diaphragm, with the heart sandwiched between them

Both lungs are surrounded by a double-layered membrane called the pleural membrane

the outer pleural membrane is attached to the wall of the thoracic cavity the inner pleural membrane is attached to the surface of the lungs

Between the two membranes is pleural fluid this fluid reduces friction between the membrane as you breathe

Pleurisy – inflamed membranes very painful, hurts every time you breathe it is like having sand in your eye, it rubs with every breath normal pleurisy

B. Respiratory Passageways 1. Nose – air is filtered of large particles (dust, pollen) by nose hairs 2. Nasal cavity – lined with cilia and mucus

air is warmed, moistened, and filtered as it moves through the nasal cavity

3. Pharynx (upper throat) – passageway for both food and air 4. Larynx (voice box) – houses the vocal cords

loudness of sounds is controlled by amount of air passing over cords, while pitch is controlled by how tight the vocal cords are stretched breathing talking high pitch

food is prevented from entering the larynx by a small flap of cartilage called the epiglottis. the epiglottis will close over the opening of the larynx when you swallow

5. Trachea (windpipe) – a 10 to 12 inch tube lined with cilia and mucus mucus traps particles that are moved by cilia up to pharynx and then swallowed

the trachea is kept open by C-shaped pieces of cartilage cartilage rings

6. Bronchi – the inferior end of the trachea that divides to form two branches that enter each lung bronchus

the right and left bronchi divide in the lungs to form smaller branches that eventually connect to very tiny air passages called bronchioles

7. Bronchioles – the smallest respiratory passageways lined with cilia and mucus, no cartilage supports in their walls extending from bronchioles like clusters of grapes are tiny air sacs called alveoli

8. Alveoli – one cell layer thick, and they are surrounded by capillaries location of external respiration – exchange of gases between the atmosphere and the bloodstream

You have approximately 300 million alveoli in each lung

alveoli increase the surface area of your lungs (you need a large surface area to exchange large amounts of gases if you were to spread out all your alveoli, they would cover a tennis court

Bronchioles and alveoli do not have cartilage in their walls they have a soapy-like fluid called surfactant surfactant keeps the alveoli and bronchioles open by reducing the surface tension within them

C. The Mechanism of Breathing Breathing is the result of volume and pressure changes that occur in the lungs involves 2 processes: inspiration expiration

1. Inspiration – taking air into the lungs occurs when the diaphragm and intercostal muscles contract contraction of the diaphragm causes it to flatten, contraction of the intercostal muscles causes the rib cage to expand upward and outward

Contraction of these 2 groups of muscles increase the volume of chest cavity As a result, the pressure within the chest cavity is now less than atmospheric pressure – air rushes into the lungs

Summary of inspiration: a. Diaphragm and intercostal muscles contract, causing b. Volume of chest cavity to , c. Pressure within the chest cavity to , resulting in d. inhalation

2. Expiration – expelling air from the lungs occurs when the diaphragm and intercostal muscles relax relaxation of the diaphragm allows it to return to its normal dome shape

relaxation of the intercostal muscles cause the rib cage to move downward and inward Relaxation of these 2 groups of muscles decreases the volume of the chest cavity.

As a result, the pressure within the chest cavity is now greater than atmospheric pressure – air rushes out of the lungs

Summary of expiration: a. diaphragm and intercostal muscles relax, causing b. volume of chest cavity to , causing c. Pressure within chest cavity to , resulting in d. expiration

Two important facts to remember about respiration: 1. Volume and pressure are inversely related to each other This means that when V, P and when V , P

2. Inspiration is an active process (muscles contract), while expiration is a passive process (muscles relax)

One respiratory cycle = 1 inhalation + 1 exhalation most adults have 16 – 24 respiratory cycles per minute when they are at rest

Can you consciously control the number of respiratory cycles you have? Up to a point by hyperventilation (rapid breathing) and hypoventilation (slow breathing)

Eventually you have to breathe when you hold your breath the CO2 levels in your blood increase, causing the blood to become acidic the more acidic, the stronger the urge to breathe

D. Gas Exchange and Transport To understand gas exchange you must remember that gases move across a membrane by diffusion Diffusion – movement of substances from a higher to a lower concentration

When you inhale, the air you take into your lungs is high in O2 and low in CO2 blood entering the lungs is high in CO2 and low in O2 O2 diffuses from the alveoli into the bloodstream, while CO2 diffuses from the bloodstream into the alveoli

When blood reaches the cells of your body, O2 will diffuse from the RBCs into your body cells. Oxygen is transported in the bloodstream in 2 ways: 1. Dissolved in the plasma (3%) 2. Bound to hemoglobin of RBCs (97%)

Carbon dioxide is transported in the bloodstream in 3 ways: 1. As CO2 dissolved in plasma (8%) 2. Bound to the globin portion of hemoglobin (25%) 3. As bicarbonate ions (HCO3-) dissolved in plasma (67%)

Carbon dioxide is converted to bicarbonate ions within the RBCs with the help of a special enzyme called carbonic anhydrase CO2 + H2O  H2CO3 HCO3- + H+

When blood rich in bicarbonate ions returns to the lungs, the reverse reaction occurs and CO2 is released

E. Regulation of Breathing Your normal rate and rhythm of breathing is controlled by a region of your brain called the respiratory control center

it is important to realize that high levels of CO2increase your breathing rate, NOT low levels of O2

F. Respiratory System Abnormalities 1. Atelectasis – collapsed lung

2. Bronchitis – inflammation of the bronchi

3. Cystic fibrosis – excessive mucus production in lungs Most lethal genetic disease in U.S.

4. Emphysema – walls of alveoli rupture leaving less area for the exchange of gases

5. Lung cancer – malignant growth of cells in lungs Fewer than 10% of individuals diagnosed with lung cancer live more than 5 years

6. Asthma – bronchioles of the lungs become constricted

7. Pleurisy – inflammation of the pleura