Basics of the Respiratory SystemBasics of the Respiratory SystemRespirationRespiration

• 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 RespirationStep 3 = transport of gases in bloodStep 4 = exchange between blood and cells

– Referred to as Internal Respiration

– Cellular respiration = use of oxygen in ATP synthesis

External Respiration

Internal Respiration

Schematic View of Respiration

Respiratory physiology.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 The components of the respiratory systemsystem

The upper respiratory tract.The upper respiratory tract.

The resp epithelium of nasal cavity and The resp epithelium of nasal cavity and conducting systemconducting system

Basics of the Respiratory SystemBasics of the Respiratory SystemFunctional AnatomyFunctional 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)

VentilationVentilationThe relationship between minute volume (total pulmonary ventilation)

and alveolar ventilation & the subsequent “mixing” of air

Prominent cells in the adult human Prominent cells in the adult human alveolus.alveolus.

Defense mechanisms of respiratory Defense mechanisms of respiratory systemsystem

• 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 Defense mechanisms of Respiratory system.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

smokerssmokers

• This ciliary motility is defective leading to chronic sinusitis,recurrent lung infections.bronchiectesis and prolonged exposure to carcinogens.

Defense mechanism.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 Humoral and cellular defense mechanisms.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.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 innervation of the bronchi and bronchiolesbronchioles

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 Congenital central hypoventilation syndromehypoventilation syndrome

Recent 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.comExplore: Medulla oblongata, Ventral respiratory group

is important for the generation of respiratory rhythm. biomedcentral.com

Explore: Medulla oblongata, Ventral respiratory group