Transcript The Respiratory System

The Respiratory System
Respiratory System
Respiratory System
Organs of the Respiratory System
• Upper respiratory system
– Nose, nasal cavity, pharynx, glottis and larynx
• Lower respiratory system
– Trachea, bronchus, bronchioles, and lungs
– Diaphragm-skeletal muscle; functions in ventilation
All airways that carry air to lungs:
• Nose, pharynx, larynx, trachea bronchi, bronchioles, and terminal
bronchioles
Sites within lungs where gas exchange occurs
• Respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli
Nose
• Structure
– External nares  nasal cavity  internal nares
– Nasal septum divides nose into two sides
– Nasal conchae covered by mucous membrane
• Functions
– Warm, humidify, filter/trap dust and microbes
• Mucus and cilia of epithelial cells lining nose
– Detect olfactory stimuli
– Modify vocal sounds
Large stiff Hairs
Nose
Sinuses
Nasal Cavity
Olfactory Receptors
Pharynx
Pharynx
• Known as the “throat”
• Structure
– Funnel-shaped tube from internal nares to larynx
• Three regions (with tonsils in the upper two)
– Upper: nasopharynx; posterior to nose
• Adenoids and openings of auditory (Eustachian) tubes
– Middle: oropharynx; posterior to mouth
• Palatine and lingual tonsils are here
– Lower: laryngopharynx
• Connects with both esophagus and larynx: food and air
larynx
• “Voice box”
• Made largely of cartilage
– Thyroid cartilage: V-shaped
• “Adam's apple”: projects more anteriorly in males
• Vocal cords “mucoso folds
– Epiglottis: leaf-shaped piece; covers airway
• During swallowing, larynx moves up so epiglottis
covers opening into trachea-glottis
– Cricoid cartilage: inferior most portion
– Arytenoids (paired, small) superior to cricoid
Larynx
Vocal Cords: mucosal folds
Lower Respiratory System:
Larynx
Trachea
• “Windpipe”
• Location
– Anterior to esophagus and thoracic vertebrae
– Extends from end of larynx to primary bronchi
• Structure
– Lined with pseudostratified ciliated columnar mucous
membrane: traps and moves dust upward
– C-shaped rings of cartilage support trachea, keep
lumen open during exhalation
• Tracheostomy: opening in trachea for tube
Trachea
• The methods outlined above, coughing,
backblows, and abdominal thrusts
(Heimlich maneuver) have a very high rate
of success. In the event, however, that
these methods fail to dislodge the
obstructing material from the air pipe
(trachea), a tracheotomy must be
considered.
Larynx
tracheotomy
Cricoid Cartilage
Lungs
• Two lungs: left and right
– Right lung has 3 lobes
– Left lung has 2 lobes
• Lungs surrounded by pleural membrane
– Parietal pleura attached to diaphragm and
lining thoracic wall
– Visceral pleura attached to lungs
– Pleural cavity with little fluid between pleurae
Lung Lobes
Bronchi
• Structure of bronchial tree
– Bronchi contain cartilage rings
– Primary bronchi enter the right and left lungs
– In lungs, branching secondary bronchi
• One for each lobe of lung: 3 in right, 2 in
left
– Tertiary bronchi    terminal bronchioles
• These smaller airways
– Have less cartilage, more smooth muscle.
– In asthma, these airways can close.
Bronchioles
•  Respiratory bronchioles
– Lined with nonciliated epithelium
 Alveolar ducts
 Alveolar sacs
 Surrounded by alveoli
Terminal Alveolar
Alveoli
• Cup-shaped
• Alveoli: composed of three types of cells
– Lined with thin alveolar cells (simple squamous); sites
of gas exchange
– Surfactant-secreting cells. Surfactant:
• Lowers surface tension (keeps alveoli from collapsing)
• Humidifies (keeps alveoli from drying out)
– Alveolar macrophages: “cleaners”
• alveoli + capillary
– Gases diffuse across these thin epithelial layers: air
 blood
Alveolar Sac
Surfactants
Air
• Mixture of gases (N2, O2,, CO2, H2O, and
others)
• Each gas has own partial pressure, such
as PO2 or PN2
• Sum of all partial pressures = atmospheric
pressure
• Each gas diffuses down its partial
pressure
Diffusion
• Diffusion across alveolar-capillary membrane
– O2 diffuses from air (PO2 ~105 mm Hg) to pulmonary
artery (“blue”) blood (PO2 ~40 mm Hg).
(Partial pressure gradient = 65 mm Hg)
• Continues until equilibrium (PO2 ~100-105 mm Hg)
– Meanwhile “blue” blood (PCO2 ~45) diffuses to alveolar
air (PCO2 ~40) (Partial pressure gradient = 5 mm Hg)
• Occurs throughout body
• O2 diffuses from blood to cells: down
partial pressure gradient
• PO2 lower in cells than in blood because
O2 used in cellular metabolism
• Meanwhile CO2 diffuses in opposite
direction: cells  blood
Internal
and
External
Respiration
Transport of Carbon Dioxide
• CO2 diffuses from tissues into blood 
• CO2 carried in blood:
– Some dissolved in plasma (7%)
– Bound to proteins including hemoglobin (23%)
– Mostly as part of bicarbonate ions (70%)
• CO2 + H2O  H+ + HCO3-
• Process reverses in lungs as CO2 diffuses
from blood into alveolar air  exhaled
Transport of
Oxygen and
Carbon
Dioxide
External Respiration
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Bicarbonate ions
Carbonic ahydrase
Acidosis
Alkalosis
Carbaminohemoglobin
Oxyhemoglobin
deoxyhemoglobin
Control of Respiration
• Nervous Control of Breathing is located in the
medulla oblongata of brain
• Chemical control are sensory receptors in the
body that are sensitive to chemical
composition of body fluids
• Two sets of chemoreceptors sensitive to pH
can cause breathing to speed up.
Location: medulla oblongata and in the carotid
arteries and aortic bodies .
These chemoreceptors are stimulated by the
Carbon dioxide concentration.
Regulation of Respiratory
Center
• Chemoreceptor input to  increase
ventilation
– Central receptors in medulla: sensitive to  H+
or PCO2
– Peripheral receptors in arch of aorta +
common carotids: respond to  PO2 as well
as  H+ or PCO2 in blood
• Blood and brain pH can be maintained by
these negative feedback mechanisms
Mechanism of Breathing
• Inspiration: rib cage moves up and out
• External intercostal muscles pull the ribs
outward
• Diaphragm contracts and move down
• When pressure in lungs decreases, air
comes rushing in.
Expiration
• Rib cage moves down and in
• Internal intercostal muscles pull the ribs
inward during forced expiration
• Diaphragm relaxes and move up
• When pressure in lungs increases, air is
pushed out