mature tracheary elements are dead cells, made up of only their cell walls and with neither cytoplasm nor nuclei. Why is it necessary for these cells to be dead in order to function properly?

Which of these is NOT true of pseudostratified ciliated columnar epithelium? It produces mucus to trap particles in the respiratory tract It appears to be more than one layer of cells but is actually only one layer. It is used to sweep small particles away from the lungs It is used in the respiratory system as a protective barrier in areas with increased friction.

The structure in the lungs known as the respiratory membrane is where gases are exchanged- oxygen leaves the lungs and enters the blood, and carbon dioxide leaves the blood and enters the lungs. The respiratory membrane is composed of two extremely thin layers of simple squamous epithelium. Explain how the structure of the respiratory membrane follows its function.

Following is a list of tissues that have specialized functions and demonstrate corresponding specialization of subcellular structure. Match the tissue with the letter of the cell structures and organelles listed to the right that would be abundant in these cells.  Tissues -Enzyme (protein)-secreting cells of the pancreas -Insect flight muscles -Cells lining the respiatory passages -White blood cells that engulf and destroy invading bacteria -Leaf cells of cacti   Cell Structures and Organelles: a. plasma membrane b. mitochondria c. Golgi apparatus d. chloroplast e. endoplasmic reticulum f. cilia and flagella g. vacuole h. ribosome i. lysosome

5) cells that reach the stratum Corneum are dead and contain which of the following? a) keratin  b) lamellae c) collagen  d) water

The epithelium of the respiratory tract is mostly of the pseudostratified columnar ciliated type, but in the alveoli, the tiny sacs where oxygen and carbon dioxide are exchanged between the blood and inhaled air, the epithelium is simple squamous. Explain the functional significance of this histological difference. That is, why do the alveoli not have the same kind of epithelium as the rest of the respiratory tract? Explain your answer in 4 to 5 sentences. Indicate the reference/s of your answer.

A 10-year-old boy undergoes an appendectomy. Granulation tissue develops normally at the incision site. Tissue remodeling begins at this site with degradation of collagen in the extracellular matrix by which of the following proteins? (A) Cytokines (B) Lipoxygenases C Metalloproteinase (D) Nitric oxide (E) Plasminogen activator