Respiratory System

functions:

• used to intake and expel air
• site of oxygen and carbon dioxide exchange with the blood
• maintains acid and base balance
• speech
• smell and taste senses
• traps and expel pathogens

nose and nasal cavities

• olfactory nerve - sense of smell

• palates- separate nasal and oral cavities

• nasal cavity-

  • warms and moistens inhaled air
  • uses mucus and cilia to trap dust and pathogens

  → removed by sneezing or swallowing

pharynx : throat; small muscular passageway

• three regions:
  • nasopharynx - air
  • orapharyx and laryngopharynx - both food water and air

larynx: 9 pieces of cartilage

• closes off the trachea when food is swallowed (epiglottis)
• produces sound (vocal cords)
• air passage between pharynx and trachea

lower respiratory tract:

• trachea

  • rigid tube supported by rings of cartilage (doesnt collapse)
  • brings air into lungs

• bronchi

  • at the end of trachea, right and left branches of bronchi enter each lung
  • each primary bronchi subdivides into smaller bronchi

• alveoli

  • bronchioles divide into structures called alveoli
  • gas exchange in blood occurs in the alveoli

  → each alveolus is encased by capillaries

  → to facilitate diffusion between alveoli and capillaries, both have thin walls

gas exchange: gasses diffuse from high to low concentration

lungs:

• large, spongy organs that have an opening for bronchi
• role is to expand and contract to facilitate breathing
• no muscle tissue
• depend on nearby muscle in ribs and diaphragm to expand and contract

respiratory muscle:

• intercostals
  • located between ribs
  • pull ribs up and out when contracted
• diaphragm
  • main breathing muscle
  • located under lungs
  • flattens and enlarges the thoracic cavity when contracted (relaxed=dome)

pulmonary ventilation = breathing

• inspiration (breathe in) and expiration (breathe out)

  • both depends on

  → respiratory muscles (lungs have no muscle tissue)

  → difference between air pressure within the lungs and outside the body

inspiration

• air is inhaled
• muscles contract ; diaphragm is flattened, muscles in ribs pull up and out
• this causes expansion in thoracic cavity (more space)
• as a result, low pressure in lungs and high pressure outside
• air flows from high to low pressure; fills lungs

expiration

• muscles relax
• diaphragm bulges upward; rib muscles stop pulling
• this causes a reduction in size in thoracic cavity (less space)
• as a result, high pressure in lungs and low pressure outside
• air flows from high to low pressure; lungs empty ; air is exhaled

pleura

• because lungs expand and contract, its important that friction is reduced
• therefore, lungs surrounded with a lining called pleura
• pleura is filled with serous fluid. this fluid
  • reduces friction
  • maintains pressure needed for breathing
• pleura consists of two linings with a fluid filled space between then

visceral pleura

• covers the surface of lungs

parietal pleura

• lines the thoracic cavity

pleural cavity

• filled with serous fluid, called pleural fluid
• lubricates to reduce friction
• maintains pressure for breathing
• the pressure in pleural cavity allows lung to expand

neural control of breathing

• stimulation to breathe comes from the autonomic nervous system

medulla oblongata

• contains a respiratory center that causes the intercostal and diaphragm to contract

pons

• contains two centers that can influence breathing rhythms

factors that influence breathing

• co2 (main regulator)- high levels signals medulla to high breathing
• oxygen levels- low oxygen signals medulla to high breathing
• hydrogen ions/ ph- low ph signals medulla to high breathing
• stretch- lungs stretching inhibits signals for inhalation
• pain and emotion- limbic system affects breathing in response to emotions

resistance and air flow- like blood flood, greater resistance means less airflow

diameter of bronchioles

• bronchiole dialation- larger diameter and more airflow
• bronchiole constriction- smaller diameter and less airflow

pulmonary compliance

• elasticity of lung tissue allows more airflow

measurement of ventilation

• breathing through a spirometer gives information about lung capacity
• if lungs showing increased resistance and decrease capacity, this can indicate disease

inspiratory reserve volume

• amount of air inhaled during max effort

vital capacity

• amount of air of that can be inhaled and exhaled with max effort

total lung capacity

• vital capacity + residual volume

tidal volume

• amount of air inhaled and exhaled during normal breathing; “quiet breathing”

expiratory reserve volume

• amount of air exhaled during max effort

residual volume

• amount of air that always remains in lungs after exhalation