Biomedical Engineering Reference
In-Depth Information
the nasal cavities (hollow spaces within the bones of the skull that warm, moisten,
and filter the air). There are three bony projections inside the nasal cavity, the supe-
rior, middle, and inferior nasal conchae. Air passes between these conchae via the
nasal meatuses. Air then travels past the nasopharynx, oropharynx, and laryngophar-
ynx, the three portions that make up the pharynx, a funnel-shaped tube that connects
nasal and oral cavities to the larynx. The tonsils, which are part of the lymphatic sys-
tem, form a ring at the junction of the oral cavity and the pharynx, protecting against
the invasion of foreign antigens. Therefore, through this protection the respiratory
tract aids the immune system. Then, the air travels through the larynx, which closes at
the epiglottis to prevent the passage of food or drink to the trachea and lungs. The lar-
ynx is the voice box containing the vocal cords, which produce sound when air passes
through them. The trachea is lined with ciliated cells and mucus-secreting cells, and
is held open by C-shaped cartilage rings. Like the larynx and nasal cavity, the trachea
protects against dust and other particles. Dust adheres to the sticky mucus, and the
cilia helps to propel it back up the trachea, where it is either swallowed or coughed
out. The mucociliary escalator extends from the top of the trachea down to the bron-
chioles. Once particles have been sidelined by the mucus, they must be removed. This
is carried out by cilia on the epithelial cells, which move the mucus continually up or
down the tract toward the nose and mouth (those in the nose beat downward, whereas
the ones in the trachea and below thrash upward). The mucus and its trapped particles
are then swallowed into the stomach. The trachea extends from the neck into the tho-
rax, where it divides into the right and left main bronchi entering the right and left
lung, respectively. This is called the carina, which is the keel-like cartilage plate at the
division point. The bronchial tree is named so because it has a series of respiratory
tubes that branch off into smaller and smaller tubes as they run throughout the lungs.
9.2.2 Physiology of the Respiratory System
The main processes of respiration are breathing or ventilation, exchange of gases and
cellular respiration, ciliary escalator action for defense against airborne infections,
and maintenance of sterility by producing mucus-containing antimicrobial com-
pounds like glycoproteins, for example, mucins, lactoferrin, lysozyme, and lactoper-
oxidase. In addition to these main processes, the respiratory system serves to regulate
blood pH, which occurs in coordination with the kidneys; as a defense mechanism
against microbes; and for controlling body temperature.
9.3 Biophysical Issues in Peptide Drug Delivery
9.3.1 Physiological and Biomechanical Factors Relevant to
Inhaled Drug Delivery
Site-specific targeted drug delivery negotiates an exclusive delivery to specific tissue
with maximum intrinsic activity of drugs and simultaneously reduces access of the
drug to nontargeted cells. A number of strategies are followed to target various body
Search WWH ::
Custom Search