Beaks are innovative structures characterizing numerous tetrapod lineages, including birds, but little is known about how developmental processes influenced the macroevolution of these important structures. Here we provide evidence of ontogenetic vestigialization of alveoli in two lineages of theropod dinosaurs and show that these are transitional phenotypes in the evolution of beaks. One of th...

➥ normal inspiration and expiration. In adults it is about 700 ml (10 ml/kg). Expiratory reserve volume (ERV) is the gas volume additionally exhaled during forced expiration and inspiratory reserve volume (IRV) is that after a forced inspiration. The sum of VT and IRV is the inspiratory capacity (IC). Even after a maximum expiratory effort, some air is left in the lung; no lung region normally ...

In a healthy lung, the inside surface of respiratory airways is coated with a thin film of lipids and proteins called lung surfactants (LS) which dynamically alter the surface tension and stabilize airways and reduce the work of breathing. Certain clinical events, such as gastric content aspiration, pneumonia, near-drowning, toxic gas inhalation, or chest/lung trauma will trigger lung surfactan...

Some adult eusocial bees have a pair of cephalic salivary glands (CSG) in addition to the thoracic labial or salivary gland pairs. This paper deals with variations in morphological features and secretion production of the CSG of females and males of Apis mellifera Linnaeus, 1758 and Scaptotrigona postica Latreille, 1807. The following life stages were studied: newly emerged, nurse, and forager ...

ONE of the classic descriptions of the insemination process is that of F. R. Lillie (1911) in the egg of the annelid, Nereis. According to Lillie, there exists beneath the vitelline membrane of the unfertilized Nereis egg a wide cortical layer. He describes it as "a coarsely alveolar layer with homogeneous alveolar contents. The walls of the alveoli are continuous internally with the protoplasm...

In 11 isolated dog lung lobes, we studied the size distribution of recruited alveolar volumes that become available for gas exchange during inflation from the collapsed state. Three catheters were wedged into 2-mm-diameter airways at total lung capacity. Small-amplitude pseudorandom pressure oscillations between 1 and 47 Hz were led into the catheters, and the input impedances of the regions su...

Alveolarization in humans and nonhuman primates begins during prenatal development. Advances in stereological counting techniques allow accurate assessment of alveolar number; however, these techniques have not been applied to the developing human lung. Based on the recent American Thoracic Society guidelines for stereology, lungs from human autopsies, ages 2 mo to 15 yr, were fractionated and ...

Postnatal developmental stages of lung parenchyma in rhesus monkeys is about one-third that of humans. Alveoli in humans are reported to be formed up to 8 yr of age. We used design-based stereological methods to estimate the number of alveoli (N(alv)) in male and female rhesus monkeys over the first 7 yr of life. Twenty-six rhesus monkeys (13 males ranging in age from 4 to 1,920 days and lung v...

A quantitative study is here reported on the lungs of a child of 9 months with unilateral emphysema associated with hypoplasia, and with compensatory emphysema in the contralateral lung. The left lung was judged to show congenital hypoplasia because of the reduced number of bronchi and arteries, its small volume, and a total alveolar number less than that normally found at birth. This last was ...

Massaro, Gloria D., and Donald Massaro. Retinoic acid treatment partially rescues failed septation in rats and in mice. Am J Physiol Lung Cell Mol Physiol 278: L955–L960, 2000.—Pulmonary alveoli are formed in part by subdivision (septation) of the gas-exchange saccules of the immature lung. Septation results in smaller, more numerous structures (alveoli) and is developmentally regulated in mamm...