Transcript Introduction Of Respiratory Physiology By Prof Samia Jawed 02

Basics of the Respiratory System
Respiration
• What is respiration?
– Respiration = the series of exchanges that leads to
the uptake of oxygen by the cells, and the removal of
carbon dioxide from the body as a whole.
Step 1 = ventilation
– Inspiration & expiration
Step 2 = exchange between alveoli (lungs) and pulmonary
capillaries (blood)
– Referred to as External Respiration
Step 3 = transport of gases in blood
Step 4 = exchange between blood and cells
– Referred to as Internal Respiration
– Cellular respiration = use of oxygen in ATP
synthesis
Schematic View of Respiration
External Respiration
Internal Respiration
Respiratory physiology.
• At rest normal human breathes 12-15
times a minute.
• Each breath contains 500 ml of air.
• Which means 500×12=6L of air inspired
and expired each min.
• On average 250 ml of Oxygen enters the
body per min and 200 ml of carbon dioxide
is excreted.
The components of the respiratory
system
The upper respiratory tract.
The resp epithelium of nasal cavity and
conducting system
Basics of the Respiratory System
Functional Anatomy
• What structural aspects must be considered in the
process of respiration?
– The conduction portion
– The exchange portion
– The structures involved with
ventilation
• Skeletal & musculature
• Pleural membranes
• Neural pathways
• All divided into
– Upper respiratory tract
• Entrance to larynx
– Lower respiratory tract
• Larynx to alveoli (trachea
to lungs)
Ventilation
The relationship between minute volume (total pulmonary ventilation)
and alveolar ventilation & the subsequent “mixing” of air
Prominent cells in the adult human
alveolus.
Defense mechanisms of respiratory
system
• Physiological mechanisms
• 90% of particles>10 microns are removed
in nose and nasopharynx.
• Pollen grains are >20 micron
• Particles between 5-10 impact at the
tracheal bifurcation(carina).
Defense mechanisms of Respiratory
system.
• The removal is by mucociliary escalators.
• It is actually cilia in contact with the gel like
mucus (acid and polysaccharides) formin
a mucus blanket.
• Cilia beat at rate of 1000/min and move
the inhaled bactaria and particles at 1.5
cm/min toward larynx.
• Particles 1-5 microns reach the deep lungs
and are removed by PAM’s
smokers
• This ciliary motility is defective leading to
chronic sinusitis,recurrent lung
infections.bronchiectesis and prolonged
exposure to carcinogens.
Defense mechanism.
• Clara cells-non ciliated cuboidal secrete
defense markers and are progenitors
• Epithelial cells secrete IgA,SP-A,peptides
proteases,reactive oxygen and nitrogen
species.They all act directly as
antimicrobials.
• Epthelial cells also secrete cytokines and
chemokines that recruit the immune cells
to the site of infection.
Humoral and cellular defense
mechanisms.
• Pulmonary alveolar macrophages are actively
phagocytic and ingest small particles.
• IgA against antigens
• Surfactant protein A ---opsonization and
increase phagocytosis
• Complement from blood—cytotoxic
• Interferon—in response to viruses
• Lysozymes.—are the enzymes in the
granulocytes and are bactericidal
Cough and sneeze reflex.
Irritants.nasal passages.lower respiratory
passages.afferents pass in the 5th and 10th cranial nerves
to the medulla.uvula depreesed in sneeze to allow air to
pass through the nose.
First, up to 2.5 liters of air are rapidly inspired. Second, the
epiglottis closes, and the vocal cords shut tightly to entrap the air
within the lungs. Third, the abdominal muscles contract forcefully,
pushing against the diaphragm while other expiratory muscles,
such as the internal intercostals, also contract forcefully.
Consequently, the pressure in the lungs rises rapidly to as much
as 100 mm Hg or more. Fourth, the vocal cords and the epiglottis
suddenly open widely, so that air under this high pressure in the
lungs explodes outward. Indeed, sometimes this air is expelled at
velocities ranging from 75 to 100 miles per hour.
innervation of the bronchi and
bronchioles
The walls of the bronchi and bronchioles are innervatedby the
autonomic nervous system. Muscarinic receptors are abundant,
and cholinergic discharge causes bronchoconstriction. The
bronchial epithelium and smooth muscle containβ 2-adrenergic
receptors. Many of these are not innervated. Some may be
located on cholinergic endings, where they inhibit acetylcholine
release. The β2 receptors mediate bronchodilation. They increase
bronchial secretion , while α 1 adrenergic receptors inhibit
secretion. There is in addition a noncholinergic, nonadrenergic
innervation of the bronchioles that produces bronchodilation, and
evidence suggests that VIP is the mediator responsible for the
dilation.
Congenital central
hypoventilation syndrome
Recent
The pre-Bötzinger complex (preBötC) is a central pattern
generator within the ventrolateral medulla oblongata's ventral
respiratory group thatThe pre-Bötzinger complex (preBötC) is a
central pattern generator within the ventrolateral medulla
oblongata'sventral respiratory group that is important for the
generation of respiratory rhythm. biomedcentral.com
Explore: Medulla oblongata, Ventral respiratory group
is important for the generation of respiratory rhythm.
biomedcentral.com
Explore: Medulla oblongata, Ventral respiratory group