Anatomy and Physiology - Respiratory System

Basic functions of the respiratory system

• Breathing: intake of O₂ into blood, elimination of CO₂ out of blood

• Maintenance of homeostasis: regulates blood pH/acidity by speeding up / slowing down the rate of respiration

• Sensory information: contains receptors for sense of smell in the nasal passages

• Filters/warms/moistens air that enters the body

• Produces sounds: air moves over vocal cords in the larynx (voicebox)

Conduction zone

air/gases enter and exit through passageways of the respiratory system

Respiratory zone

location of gas exchange between the respiratory and circulatory system

Structures of the conduction zone

• Nostrils

• Mouth

• Trachea

• Primary bronchus

• Secondary bronchus

• Tertiary bronchus

• Bronchioles

Structures of the respiratory zone

• Alveoli

• Alveolar ducts

• Capillaries

Inhalation / Inspiration

act of drawing air into the lungs

Exhalation / expiration

act of expelling air from the lungs

Inhalation thoracic cavity size

• Diaphragm contracted / moves downward

• Rib cage moves up / out; intercostal muscles contract

• Pressure within thoracic cavity decreases, volume increases

• Lungs expand due to decreased pressure

Exhalation thoracic cavity size

• Diaphragm relaxed / moves up

• Rib cage moves down / in; intercostal muscles relax

• Pressure within thoracic cavity increases as volume decreases

• Lungs squeezed and air forced out

Alveoli

• Sac-like structures with single-cell layer thick walls

• Found in clusters at the end of alveolar ducts

• Encased in a network of capillaries

• Alveoli are the site of gas exchange between the lungs and the blood

Purpose of gas exchange

Aerobic cellular respiration

• Tissues/cells take in oxygen for cellular respiration

• Tissues make carbon dioxide as a product of cellular respiration

Factors affecting gas exchange at respiratory membrane

• Thickness of membrane: increased thickness results in decreased rate of gas exchange (scar tissue build up in alveoli)

• Surface area: decrease in surface area results in decrease in gas exchange (surface area decreases when thickness increases)

• Gas pressure gradients: must have the correct pressure gradient in order to exchange gas properly

What happens when carbon dioxide enters the blood?

It is converted into carbonic acid/bicarbonate and dissolved in blood

What happens when oxygen enters the blood?

It binds to hemoglobin in red blood cells.

Hemoglobin

an iron containing molecule found in red blood cells that binds to oxygen gas so it can be transported in the bloodstream

Ventilation level too low (blood pH too low = acidic)

triggers central chemoreceptors in medulla to speed up ventilation rate by increasing stimulation of respiratory muscles

Ventilation level too high (blood pH too high = basic)

triggers central chemoreceptors in medulla to slow down ventilation rate by decreasing stimulation of respiratory muscles

Baroreceptors

sense air pressure changes and can lead to ventilation rate changes as well

Spirometry

the process of measuring volumes of air that move into and out of the respiratory system

Spirometer

device used to measure pulmonary volumes and assist in diagnosing pulmonary disorders

Tidal volume

air inspired/expired during a normal breath

Inspiratory reserve

air that can be forcefully inspired after a normal inspiration

Expiratory reserve

air expelled forcefully after expiration of normal tidal volume

Residual volume

volume of air still remaining in lungs after a maximum expiration

Vital capacity

• Inspiratory reserve volume + tidal volume + expiratory volume

• Maximum amount of air a person can expel after a maximum inspiration

• Depends on height, age, health, biological sex

Effects of aging on respiratory system

• Alveoli, respiratory tract and chest wall become more rigid and less elastic

• Results in decreased lung capacity; reduced vital capacity

• More susceptible to pulmonary disorders

Hypoxia

insufficient oxygen for cellular respiration

Apnea

absence of ventilatory movements

Dyspnea

painful or labored breathing

Hyperventilation

• Increased rate of breathing in excess of metabolic needs

• Results in excessive intake of O₂ and increased elimination of CO₂ leading to disturbance of acid-base balance

• Causes dizziness, tingling in extremities, and may cause faintin

Hypoventilation

• Reduced rate of breathing inadequate to meet metabolic needs

• Decreased levels of O₂ and increased levels in CO₂ in the blood

• Causes cyanosis

• Decreased ventilatory activity is associated with overdose of drugs and SIDS