THE RESPIRATORY SYSTEM

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THE RESPIRATORY SYSTEM

• Chapter 36

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• What is respiration?
• External respiration - exchange of O2 CO2
  between respiratory surfaces the blood
  breathing.
• Internal respiration - exchange of O2 CO2
  between the blood cells.
• Cellular respiration - process by which cells use
  O2 to produce ATP.

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• A. Types of Respiratory Surfaces
• All respiratory surfaces MUST be
• moist
• thin
• large enough to meet metabolic needs of organism
• Challenges
• Aquatic organisms - H2O contains only 1/30 the O2
  present in air.
• Terrestrial organisms - must prevent desiccation
  of respiratory surface.

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• 1. Body surface
• simplest gas exchange mechanism
• adapted to moist environment
• may be associated with circulatory system

• protista
• cnidaria
• flatworms
• earthworms
• amphibians

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• 2. Tracheae - highly branched system of internal
  tubules.
• adapted to terrestrial environment
• NOT associated with a circulatory system

• terrestrial arthropods
• Large, active arthropods use abdominal flight
  muscles to ventilate tubules.

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• 3. Gills - featherlike extensions of the body
  surface.
• adapted to aquatic environment
• may be external or internal

• some echinoderms
• some annelids
• aquatic mollusks
• crustaceans
• amphibian larvae some adult salamanders

• fish

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• In fish
• operculum protects gills pumps water over their
  surfaces
• water flow is countercurrent to blood flow

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• 4. Lungs - paired internal sacs lined with moist
  epithelium.
• adapted to terrestrial environment
• interact with circulatory system

• vertebrates

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• B. Human Respiratory System
• 1. Nose
• lining is ciliated secretes mucus
• filters, warms moistens air

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• 2. Pharynx Larynx

nasal cavity

• Pharynx (throat)
• muscular tube
• conducts air food

pharynx
larynx

• Larynx (Adams apple)
• cartilaginous structure
• contains vocal cords conducts air

What prevents food from entering
larynx? epiglottis What causes deepening of
male voice during puberty?
testosterone
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• 3. Trachea, Bronchi Bronchioles

larynx

• Trachea (windpipe)
• tube supported by C-shaped cartilages
• lining is ciliated secretes mucus

trachea
bronchi
bronchioles

• Bronchi (sing. bronchus)
• pair of tubes that branch from trachea enter
  lungs have cartilage plates
• lining is ciliated secretes mucus

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• Bronchioles
• tiny tubes lacking cartilage cilia
• possess smooth muscle

bronchiole
smooth muscle

• Autonomic nervous system regulates diameter of
  bronchioles.
• Sympathetic division dilates bronchioles
• Parasympathetic division constricts bronchioles

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• 4. Alveoli (sing. alveolus)

• grape-like clusters of tiny, thin-walled sacs
• surrounded by capillaries
• sites of external respiration

• contain surfactant
• Surfactant keeps alveoli from collapsing.

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• Path of air flow in external respiration
• nose ?
• pharynx ?
• larynx ?
• trachea ?
• bronchi ?
• bronchioles ?
• alveoli

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• C. Breathing
• Occurs in response to pressure differences
  between lungs atmosphere.
• Inhalation (active process)

• diaphragm external intercostal muscles contract
• thoracic cavity volume ? air pressure ?
• air pulled inward lungs expand

External intercostal muscles
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• Exhalation (passive process)

• diaphragm external intercostal (rib) muscles
  relax lungs recoil
• thoracic cavity volume ? air pressure ?
• air pushed outward lungs deflate

Forced exhalation is active - caused by
contraction of internal intercostal muscles
abdominal muscles. Can you force ALL air out of
your lungs?
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• D. Gas Transport in Blood
• Carbon dioxide
• 70 as bicarbonate ion (HCO3-) dissolved in
  plasma
• 23 bound to hemoglobin
• 7 as CO2 dissolved in plasma
• Oxygen
• 99 bound to hemoglobin
• 1 as O2 dissolved in plasma
• Carbon monoxide poisoning occurs because CO binds
  to hemoglobin more readily than O2.

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Amount of O2 picked up by blood is affected by
altitude.
Amount of O2 released to tissues is affected by
requirements of cells.
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• E. Control of Breathing
• Breathing is regulated by the rhythmicity center
  in the medulla of brain.

rhytmicity center
Medulla stimulates inspiratory muscles (diaphragm
external intercostal muscles).
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• The most important factor affecting the
  rhythmicity center is CO2.

• ? in arterial CO2 causes ? in acidity of
  cerebrospinal fluid (CSF).
• ? in CSF acidity is detected by pH sensors in
  medulla.

• medulla ? rate depth of breathing.

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• Oxygen level does not regulate breathing unless
  arterial O2 falls dangerously low.

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• F. Respiratory System Disorders
• Asthma - muscles of bronchioles constrict,
  drastically reducing ventilation.
• Emphysema - destruction of alveoli.
• Tuberculosis - highly contagious bacterial
  infection.

• Lung cancer - gt 90 of lung cancer victims have a
  history of smoking.