Respiratory System

Human Respiratory SystemFunctions:

Works closely with circulatory system, exchanging gases between air and blood:

Takes up oxygen from air and supplies it to blood (for cellular respiration).

Removal and disposal of carbon dioxide from blood (waste product from cellular respiration).

Homeostatic Role: Regulates blood pH. Regulates blood oxygen and

carbon dioxide levels.

Blood Transports Gases Between Lungs and Tissues

Human Respiratory SystemComponents: Nasal cavity, throat (pharynx), larynx

(voice box), trachea, bronchi, alveoli, and lungs.

Pathway of Inhaled Air: Nasal cavity Pharynx (Throat) Larynx (Voice Box) Trachea (Windpipe) Bronchi Bronchioles Alveoli (Site of gas exchange)

Exhaled air follows reverse pathway.

Human Respiratory System1. Nasal cavity: Air enters nostrils, is

filtered by hairs, warmed, humidified, and sampled for odors as it flows through a maze of spaces.

2. Pharynx (Throat): Intersection where pathway for air and food cross. Most of the time, the pathway for air is open, except when we swallow.

3. Larynx (Voice Box): Reinforced with cartilage. Contains vocal cords, which allow us to make sounds by voluntarily tensing muscles. High pitched sounds: Vocal cords are

tense, vibrate fast. Low pitched sounds: Vocal cords are

relaxed, vibrate slowly. More prominent in males (Adam’s

apple).

Human Respiratory System4. Trachea (Windpipe): Rings of cartilage

maintain shape of trachea, to prevent it from closing. Forks into two bronchi.

5. Bronchi (Sing. Bronchus): Each bronchus leads into a lung and branches into smaller and smaller bronchioles, resembling an inverted tree.

6. Bronchioles: Fine tubes that allow passage of air. Muscle layer constricts bronchioles. Epithelium of bronchioles is covered with cilia and mucus. Mucus traps dust and other particles. Ciliary Escalator: Cilia beat upwards

and remove trapped particles from lower respiratory airways. Rate about 1 to 3 cm per hour.

Pulmonary Function Tests Assessed by spirometry. Subject breathes into a closed

system in which air is trapped within a bell floating in H20.

The bell moves up when the subject exhales and down when the subject inhales.

Spirogram Tidal volume: Amount of air expired with each breath. Vital capacity: The maximum amount of air that can be forcefully exhaled

after maximum inhalation.

Anatomical Dead Space Not all of the inspired air reached the

alveoli. As fresh air is inhaled it is mixed with

anatomical dead space.

Restrictive and Obstructive Disorders

Restrictive disorder: Vital

capacity is reduced.

FVC is normal.

Obstructive disorder: VC is

normal. FEV1 is

reduced.

Breathing Ventilates the LungsBreathing: Alternation of inhalation and

exhalation. Supplies our lungs with oxygen rich air, and expels excess carbon dioxide.

Inhalation: Diaphragm contracts, moving downward and causing rib cage, chest cavity, and lungs to expand. Air rushes in, due to decrease in internal lung pressure as lungs expand.

Exhalation: Diaphragm relaxes, moving upwards and causing rib cage, chest cavity, and lungs to contract. Air rushes out, due to the increase in internal lung pressure as lungs contract.Breathing is controlled by centers in the nervous system to keep up with body’s demands.

Hemoglobin helps transport CO2 and buffer blood

Hemoglobin is found in red blood cellsFunctions:

Transports oxygen Transport carbon dioxide Helps buffer blood

As carbon dioxide is picked up from tissues it is converted into carbonic acid:

CO2 + H2O <-----> H2CO3 <----> H+ + HCO3 -

Carbon Carbonic acid Carbonate iondioxide

Hemoglobin picks up most H + ions, so they don’t acidify the blood.

Hemoglobin Loading and Unloading of Oxygen

Respiratory Acid-Base Balance Ventilation normally adjusted

to keep pace with metabolic rate.

H2CO3 produced converted to CO2, and excreted by the lungs.

H20 + C02 H2C03 H+ + HC03

-

Respiratory Acidosis Hypoventilation. Accumulation of CO2 in the tissues. pH decreases. Plasma HCO3

- increases. Pc02 increases.

Respiratory Alkalosis Hyperventilation. Excessive loss of CO2. pH increases. Plasma HCO3

- decreases. Pc02 decreases.

Human Fetus Exchanges Gases with Mother’s Blood through the Placenta

Diseases of the Respiratory System Respiratory rate: 10 to 14 inhalations/minute. In one day, an average human:

Breathes 20,000 times Inhales 35 pounds of air

Most of us breathe in air that is heavily contaminated with solid particles, ozone, sulfur oxide, carbon monoxide, nitrogen oxides, and many other damaging chemicals.

Breathing contaminated air can cause a number of diseases including asthma, bronchitis, emphysema, and lung cancer.

Diseases of the Respiratory System Respiratory rate: 10 to 14 inhalations/minute. In one day, an average human:

Breathes 20,000 times Inhales 35 pounds of air

Most of us breathe in air that is heavily contaminated with solid particles, ozone, sulfur oxide, carbon monoxide, nitrogen oxides, and many other damaging chemicals.

Breathing contaminated air can cause a number of diseases including asthma, bronchitis, emphysema, and lung cancer.

Diseases of the Respiratory System Cigarette smoke is one of the worse air pollutants.

Over 1 million people start smoking every year.

Kills about 350,000 people every year in U.S.

Contains 4000 different chemicals. Each cigarette smoked subtracts about 5

minutes from life expectancy. Cigarette smoke paralyzes cilia in airways,

preventing them from removing debris and from protecting delicate alveoli.

Frequent coughing is the only way airways can clean themselves.

Cigarette smoke also causes fetal damage, which can result in miscarriage, premature birth, low birth weight, and poor development.

Diseases of the Respiratory System Lung Cancer: Cancerous growth that

invades and destroys lung tissue. Very high fatality rate. Symptoms include bloody sputum, persistent cough, difficulty breathing, chest pain, and repeated attacks of bronchitis or pneumonia.Causes: Smoking (50% of all cases) and pollution (radon, asbestos). Smokers are 10 times more likely to develop lung cancer than nonsmokers.Treatment: Surgery is most effective, but only 50% of all lung cancers are operable by time of detection. Other treatments include radiation and chemotherapy.