The Respiratory System - Class Webpage · 2019. 8. 31. · • Larynx • Trachea • Bronchi •...

The Respiratory System

Why do we need oxygen?

Answer: We need it to obtain energy through aerobic respiration!

Organs of the Respiratory System

• Nose • Pharynx • Larynx • Trachea • Bronchi • Bronchioles • Lungs –

alveoli

Functions of the Respiratory System

1. Gas exchange between the blood and external environment

2. Purification, warming, and humidifying of incoming air

3. Provides olfactory sensations to the brain for sense of smell

4. Produces sounds for communication

Divisions of the Respiratory Tract

1. Conduction portion: nasal cavity ! larger bronchioles (cleans and warms the air)

2. Respiratory portion: smallest bronchioles ! alveoli (permits gas exchange)

Upper Respiratory Tract

Nose• Olfactory receptors are located on the

superior surface • Mucosa: lines the nasal cavity; moistens

air and traps incoming foreign particles • Conchae: projections of the nasal cavity;

increases air turbulence within the nasal cavity

• Sinuses: cavities within bones surrounding the nasal cavity; lighten the skull, resonate sounds for speech, and produce mucus

Pharynx (Throat)

• Muscular passage from nasal cavity to larynx

• Common passageway for air and food • Contains tonsils • Auditory tubes enter here (equalize

pressure and drain mucus)

Larynx (Voice Box)• Routes air and food into proper channels • Made of eight rigid cartilages and a spoon-

shaped flap of elastic cartilage (epiglottis) •Epiglottis: routes food to the esophagus

and air toward the trachea • Contains vocal cords (folds) that vibrate

with expelled air to create sound (speech) •Glottis: opening between vocal cords

Trachea (Windpipe)• Connects larynx with bronchi • Lined with ciliated mucosa that: •Beat continuously in the opposite direction of

incoming air •Expel mucus loaded with dust and other

debris away from lungs

• Walls are reinforced with C-shaped firm cartilage (open posteriorly)

Primary Bronchi

• Trachea divides into right and left bronchi

• Right bronchus is wider, shorter, and straighter than left

• Bronchi then subdivide into smaller and smaller branches

Lungs• Occupy most of the thoracic cavity • Apex is near the clavicle (collar bone) and

base rests on the diaphragm • Each lung is divided into lobes by fissures:

a. Left lung – two lobes b. Right lung – three lobes

Coverings of the Lungs

• Visceral (pulmonary) pleura covers the lung surface

• Parietal pleura lines the walls of the thoracic cavity

• Serous (pleural) fluid fills the area between layers of pleura to reduce friction, allow gliding, and keep organs lubricated

Lungs

Bronchioles

• Smallest branches of the bronchi • All but the smallest branches have

reinforcing cartilage • Terminal bronchioles end in alveoli

Alveoli• Consist of a duct and the alveolus • Gas exchange takes place within the

alveoli in the respiratory membrane • Respiratory membrane (air-blood barrier) •Thin epithelium lines alveolar walls •Pulmonary capillaries cover external

surfaces of alveoli

Bronchioles and Alveoli

Gas Exchange in the Alveoli• Gas crosses the respiratory membrane

by diffusion •Oxygen enters the blood •Carbon dioxide enters the alveoli

• Macrophages protect against infectious microorganisms

• Surfactant coats gas-exposed alveolar surfaces to keep alveoli inflated

Respiratory Membrane of Alveoli

Events of Respiration• Pulmonary ventilation: moving air in and out

of the lungs • External respiration: gas exchange between

pulmonary capillaries and alveoli • Internal respiration: gas exchange between

blood and tissue cells in systemic capillaries

Mechanics of Breathing (Pulmonary Ventilation)

• Two phases: 1. Inspiration/inhalation – flow of air into lung 2. Expiration/exhalation – air leaving lung

Inspiration/inhalation

• Diaphragm contracts (flattens), external intercostals contract raising the rib cage

• Volume of the thoracic cavity increases • Pressure in thoracic cavity decreases • Air is pulled into the lungs (from high to

low pressure)

Inspiration/inhalation

Expiration/exhalation• Largely a passive process which depends

on natural lung elasticity • Diaphragm relaxes (pushes up), external

intercostals relax depressing the rib cage • Air is pushed out of the lungs • Forced expiration can occur mostly by

contracting internal intercostal muscles to depress the rib cage further

Expiration/exhalation

Breathing Animation

Respiratory Volumes and Capacities• Tidal volume (TV) is normal breathing and

moves about 500 mL of air with each breath • Many factors affect respiratory capacity:

1. A person’s size 2. Sex 3. Age 4. Physical condition

• Residual volume (RV) of air: amount of air remaining in the lungs after normal exhalation (~1200 mL)

Respiratory Volumes and Capacities

• Inspiratory reserve volume (IRV): amount of air that can be taken in forcibly over the tidal volume (5x TV)

• Expiratory reserve volume (ERV): amount of air that can be forcibly exhaled (approx. = to RV)

Respiratory Volumes and Capacities• Vital capacity (VC): the total amount of

exchangeable air •Vital capacity = TV + IRV + ERV

• Dead space volume: air that remains in conducting zone and never reaches alveoli (150 mL)

• Functional volume: air that actually reaches the respiratory zone (350 mL)

Respiratory Volumes and Capacities

Gas Transport in the Blood1. Oxygen transport in the blood

• Inside red blood cells attached to hemoglobin • A small amount is carried dissolved in the plasma

2. Carbon dioxide transport in the blood • Most is transported in the plasma as bicarbonate

ion (HCO3–)

• A small amount is carried inside red blood cells on hemoglobin, but at different binding sites than those of oxygen

Respiration

Neural Regulation of Respiration

• Activity of respiratory muscles is transmitted to the brain by the phrenic and intercostal nerves •Phrenic nerve controls the diaphragm

• Neural centers that control rate and depth are located in the medulla

• The pons appears to smooth out respiratory rate

• Normal respiratory rate is 12–16 respirations per minute

Neural Regulation of Respiration

Chemical Regulation of Respiration1. Carbon dioxide levels

• Level of carbon dioxide in the blood is the main regulatory chemical for respiration

• Increased carbon dioxide increases respiration • Changes in carbon dioxide act directly on the medulla oblongata

2. Oxygen levels • Changes in oxygen concentration in the blood are detected by

chemoreceptors in the aorta and carotid artery • Information is sent to the medulla oblongata

Other Factors Influencing Respiratory Rate and Depth

• Physical factors: 1. Increased body temperature 2. Exercise 3. Talking 4. Coughing

• Volition (conscious control) • Emotional factors

Effects of Aging on the Respiratory System• Elasticity of lungs decreases • Vital capacity decreases • Blood oxygen levels decrease • Respiratory rate often increases • Stimulating effects of carbon dioxide

decreases • More risks of respiratory tract infection

Diagnostic Tests for the Respiratory System

• Spirometry: measures how much and how quickly a person can move air out of the lungs

• Pulse-oximetry: non-invasive measure of the oxygen saturation of the blood

• Arterial blood gas: measures the amount of oxygen and carbon dioxide in a blood sample

• Stress test: lung function is measured during exercise

• Chest x-ray: x-ray of the thorax while holding breath