10. The epiglottis closes aditus into the larynx basic tissue of the organ is elastic cartilage i t is covered with a mucous coat: stratified squamous epithelium is on its lingual aspect while pseudostratified columnar epithelium is on the laryngeal surface t he mucosa contains mixed serous and mucous glands

19. Alveolar macrophages: occur w ithin the alveoli or in the septa e cells are movable and able to phagocyte inspired particles of dust etc. they form a part of phagocyte macrophages system

20. Blood-air barrier consists of: 1- respiratory epithelium with surfactant on the surface , 2- the basal laminae of closely apposed alveolar and endothelial cells, 3- endothelial cells of blood capillaries of continuous type t he total thickness of these layers varies from 0.1 to 1.5  m i nsufficient surfactant production causes difficulty in expanding alveoli and injury of the respiratory epithelium in premature new-borns t he disease - respiratory distress syndrome g lucocorticoids stimulate the synthesis of surfactant and are used in treatment of the Respiratory Distress Syndrome (RDS).

25. 4. The FOURTH – SIXTH. Cartilage – cartilages of larynx and trachea. Mesenchyme – cricothyroid, levator veli palatini, constrictors of pharynx, intrisic muscle from larynx. The 4th aortic arch – has the ultimate fate different on the left and right sides, On the left it forms a part of the arch of the aorta between the left common carotid artery and the left subclavian vein. On the right side the proximal segment of the right subclavian artery. The 5th aortic arch - is transient and soon obliterates. The 6th aortic arch – transform into pulmonary artery (their branches) Branchial nerves – Superior laryngeal branch of the vagus, recurrent laryngeal branch of the vagus.

30. Alveolar period - is characterized by differentiation of terminal sacs into the future alveolar ducts