Lungs anatomy

Anatomic and Technical Considerations 335 Normal Lung Anatomy 335 CT Technique 336... 

MR imaging by hyperpolarized noble gas, He-3 (helium) or Xe-129 (xenon), has become a promising approach for visualizing lung anatomy and function. It has been theoretically predicted that low field strengths and low frequencies (0.05-0.2T 1.62-6.5 MHz for He-3 and 0.59-2.35 MHz for Xe-129) may provide optimal signal-to-noise ratio and spatial resolution for clinical HNG(Hyperporalized Nobel Gas) MR imaging. 

Micro-CT imaging not only allows study of lung anatomy down to the alveolar level, but also it provides a testing ground for improved cone-beam algorithms which can then be translated up to future clinical scanners. Micro-CT imaging has seen a rapid transition from one-of-a-kind laboratory instruments to commercially developed systems which have moved from use in the study of high contrast static structures (such as postmortem specimens of bone) towards... 

Histologically, NSIP can be categorized into one of three patterns cellular, fibrotic, or mixed. The hallmark of NSIP is homogeneity of the cellular of fibrosing process with gradual transition from normal lung anatomy to severe involvement (Fig. 2) (15). 

Despite recent developments, effectiveness of chemotherapy is still rather limited for most types of cancer, including tumors of the colon, lung, kidney, pancreas, and liver. Why some cancers respond better than others may be explained by factors relating to the anatomy and physiology of the cancer-ridden organ or... 

Fig. 1 The anatomy of the lungs showing the major airway subdivisions.

Nitrogen oxides combustion appliances cooking ETS. irritation of respiratory system and eyes decreased in pulmonary function in asthmatics decreased immune capacily, changes in anatomy and function of lung. 

The underpressure created in the respiratory tract is the driving force for the airflow through an inhalation device. The attainable underpressure and the rate of the airflow both depend on the total resistance in the airways and inhaler. The pressure drop achieved during inhalation is furthermore a function of the anatomy of the lungs, the effort made by the patient, pathological factors and the presence of exacerbations (e.g. in case of asthma). 

The complex functions of the lung and pulmonary system are accomplished through a series of specialized cells (more than forty types have been identified), tissues, and structures. Standard medical texts such as Gray s Anatomy (Warwick and Williams, 1973) and Functional Anatomy erf the Lung (Nagaishi, 1972) should be consulted for details, but for our purposes, we describe four features that ensure optimum lung function, before discussing the diseases that affect the system. 

Fig. 3.1 Schematic diagram of the human respiratory system. The gross anatomy of the lung, the covering membranes (pleura), airways and air sacs (alveoli) are shown. The average diameter of portions of the air flow system are indicated trachea, 20 mm bronchus, 8 mm terminal and respiratory bronchioles, 0.5 mnn alveolar duct, 0.2 mm alveolar sacs, 0.3 mm.

For more detailed information on the respiratory tract, the pleura, and the lymphatic system, consult Gray s Anatomy or other standard medical texts. A comprehensive review of the lung and its structure and function is presented in Nagaishi (1972). 

We outlined the gross and cellular anatomy of the lung as background for summarizing the mechanisms of disease induction associated with exposure to fibrous materials. Such an exercise is a bit premature, as even the normal biologic processes of fibrosis and cell differentiation or action are not fully understood (Gee and Lwebuga-Mukasa, 1984). We can briefly outline some of the experimental approaches that are yielding information at this time. It should be reiterated that the experimental approach received a tremendous impetus when UICC samples were made available in 1965. 

Nagaishi, C. (1972). Functional Anatomy and Histology of the Lung. University Park Press, Baltimore, MD, Igaku-Shoin, Ltd., Japan. 

Typically, uranium is present in limited eoneentrations in the air, and uranium partiele inhalation is minimal (ATSDR, 1999 Harley et al, 1999). Uranium particle deposition in the respiratory traet is governed by the physical forces that effeet partiele behavior in the air, as well as the anatomy of the respiratory traet (ATSDR, 1999 Bleise et al, 2003 Phalen and Oldham, 2006). The anatomy of the lungs is important as this affects the clearance mechanisms available to deal with deposited particles, and the degree of actual uranium absorption that will occur. In addition to the aerodynamic diameter (AD) of the particle, the solubility of the inhaled uranium is an important determinant as to how much uranium will be absorbed (Eidson, 1994 Lang et al, 1994). 

Lung cell cultures can provide mechanistic insights but they do not represent the complexity in the delivery and disposition of drugs in the human respiratory tract. Perfused lung organ studies provide the next level in complexity. Various animal models have been used with the view to predict quantitatively absorption of peptides and proteins from the human lungs. However, due to the major differences in the anatomy and physiology of respiration in primates, the predictive power of these models is quite limited as evidenced by the data in Fig. 2. (Animal models are, of course, essential in the assessment of safety and they can provide valuable mechanistic information.)... 

---