Download Function of the Respiratory System

Function of the Respiratory
System
• Oversees gas exchanges between the
blood and external environment
• Exchange of gasses takes place within the
lungs in the alveoli
• Passageways to the lungs purify, warm,
and humidify the incoming air
Upper Respiratory Tract
Figure 13.2
The Nose
• Air enters the nose through the external
nares (nostrils). The openings are
guarded by hairs that prevent the entrance
of large particles.
• The interior of the nose consists of a nasal
cavity divided into right and left portions by
a nasal septum.
Anatomy of the Nasal Cavity
• Lateral walls have projections called conchae
– Increases surface area
– Increases air turbulence within the nasal cavity
• The nasal cavity is lined with Pseudostratified
Columnar Epithelium that is rich in Goblet
Cells. It functions to:
– Moisten and Warm the air
– Mucous traps incoming foreign particles. Cilia
move the entrapped particles toward the pharynx
and are swallowed.
Paranasal Sinuses
• Cavities within bones surrounding the
nasal cavity
– Frontal bone
– Sphenoid bone
– Ethmoid bone
– Maxillary bone
Paranasal Sinuses
• Function of the sinuses
– Lighten the skull
– Act as resonance chambers for speech
– Produce mucus that drains into the nasal
cavity
Larynx
• Enlargement in the airway at the top of the
trachea. Serves as a passageway for air
and houses the vocal cords.
•Vocal Cords
• Composed of muscle and elastic fibers.
Create vocal sounds when air is forced
between them causing vibrations in the air
column above.
Trachea
• The windpipe is about 12.5 cm in length and
about 2.5 cm in diameter.
• It extends from the larynx downward until it
divides into the right and left bronchi.
• It is supported by C-Shaped cartilage rings
to keep it from collapsing under negative
pressure.
• The trachea divides at the level of the 5th
thoracic vertebrae into the Right and Left
Primary Bronchi.
• Each primary bronchus soon divides into
Secondary Bronchi.
• These secondary bronchi divide again and
again into smaller and smaller branches.
The smallest are bronchioles.
• Bronchioles give rise to thin tubes called
Alveolar Ducts which terminate in groups
of microscopic chambers called Alveoli.
Bronchioles
• Terminal
bronchioles
end in alveoli
Figure 13.5a
Alveoli
• Each alveoli is surrounded by a capillary
network and is the site of oxygen and
carbon dioxide exchange with the blood.
• There are about 300 million alveoli in each
lung.
Lungs
• Soft, spongy, cone-shaped organs located in
the thoracic cavity. Covered by two serous
membranes, the Pleura.
• Visceral Pleura attached to the surface of
each lung.
• Parietal Pleura attached to the wall of the
thoracic cavity.
• Pleural Cavity. Space between the pleural
layers contains serous fluid that lubricates the
lungs when breathing.
Breathing (Pulmonary Ventilation)
• Movement of air from outside of the body
into (Inspiration) and out of (Expiration)
of the lungs.
• Inspiration – The diaphragm contracts
increasing the volume of the thoracic
cavity. This reduces the air pressure in the
lungs below atmospheric pressure. Air is
forced into the lungs.
• Expiration – Diaphragm relaxes. Recoil
of elastic tissues in and around the lungs
returns lung volume to normal. This raises
the air pressure inside the lungs above
atmospheric pressure forcing air out of the
lungs.
Respiratory Volumes and Capacities
• Tidal Volume – Air that enters the lungs
during a normal quiet inspiration. (500 cc)
• Inspiratory Reserve Volume – Quantity that
enters the lungs in addition to tidal volume
during forced inspiration. (3100 cc)
• Expiratory Reserve Volume – Quantity in
addition to tidal volume that is expelled out of
the lungs during forced expiration. (1200 cc)
• Residual Volume – Volume that remains
in the lungs at all times even after forced
expiration. (1200 cc)
• Vital Capacity – Maximum volume of air
that can be exhaled after taking the
deepest breath possible. Equal to TV +
IRV + ERV. (4800 cc)
• Total Lung Capacity – Total volume of air
that the lungs can hold. Equal to VC + RV.
(6000 cc)
Respiratory Capacities
Figure 13.9
Control of Breathing
• Breathing is controlled by a group of
neurons in the pons and medulla called
the Respiratory Center.
• Neurons in these areas emit impulses that
contract the diaphragm, increase the force
of breathing and control the rate of
breathing.
Rate and Depth Stimuli
• High concentrations of CO2 and H+ ions
stimulate chemoreceptors in the medulla to
increase breathing rate.
• Low O2 concentration stimulate chemoreceptors
in the Aorta and Carotid arteries to stimulate the
medulla to increase breathing rate.
• Fear and pain increase breathing rate.
• Stimulation of stretch receptors when the lungs
are overstretched will cause the depth of
breathing to decrease.
• Rate and depth of breathing can be consciously
controlled.
Exchange of Gases
• In order for Oxygen and Carbon Dioxide to
be exchanged between the atmosphere
and blood, they must diffuse across the
Respiratory Membrane.
• The respiratory membrane consists of the
wall of the alveolus (simple squamous
epithelium), the wall of the capillary
(simple squamous epithelium), and a
common basement membrane between
them.
Respiratory Membrane
(Air-Blood Barrier)
Figure 13.6
Gas Transport in the Blood
• Oxygen transport in the blood
– Inside red blood cells attached to hemoglobin
(oxyhemoglobin [HbO2])
– A small amount is carried dissolved in the
plasma. (1.5%)
Gas Transport in the Blood
• Carbon dioxide transport in the blood
– Most is transported in the plasma as
bicarbonate ion (HCO3–). (70%)
– A small amount is carried inside red blood
cells on hemoglobin, but at different binding
sites than those of oxygen. (23%)
– The rest (7%) as a gas dissolved in the
plasma
Internal Respiration
• Exchange of gases between blood and
body cells
• An opposite reaction to what occurs in the
lungs
– Carbon dioxide diffuses out of tissue to blood
– Oxygen diffuses from blood into tissue
Internal Respiration
Figure 13.11