Where do the branches of the bronchial tree ultimately end? 2. list the steps of the pulmonary circuit of the cardiovascular system starting with the left atrium. include all valves of the heart. 3. distinguish between arteries and veins. 4. how are the cardiovascular and respiratory systems connected? explain your answer. 5. what is the purpose of the cartilage rings of the trachea? 6. list the functions of the larynx. 7. list the structures that make up the pathway of air through the respiratory system starting with the external nares?

1. The branches of the bronchial tree ultimately ends at the alveoli.
Bronchial tree consist of bronchi, bronchioles, and alveoli. Bronchi are formed as the lower part of the trachea divides into two tubes. Bronchioles are smaller tube divisions of the bronchi. It walls contain smooth muscle and no cartilage. Alveoli are tiny ends of the alveolar ducts, which functions as the site for gaseous exchange. 

2. Blood flows from the left atrium; mitral (bicuspid valves), the left ventricle, aortic valve, aorta, veins and heart, right side of the heart, superior and inferior vena cavae, right atrium, tricuspid valve, right ventricle, pulmonary valve, pulmonary trunk, pulmonary artery, lungs, pulmonary veins, then back to the heart...

3. Arteries and the veins differ in structures and they way they functions; Arteries carry oxygenated blood away from the heart to the body (except pulmonary artery) while veins carry deoxygenated blood back from the body to the heart (except pulmonary veins). A structural differences includes; the veins contain valves while arteries lack. Arteries have narrow lumen while veins have wide lumen. Lastly, blood carried by veins has higher pressure compared to blood carried in vessels.

4. The circulatory and respiratory systems work together to circulate blood and oxygen throughout the body. Air moves in and out of the lungs through the trachea, bronchi, and the bronchioles. Blood moves in and out of the lungs throgh the pulmonary arteries and veins that connect to the heart.

5. The cartilage rings of the trachea
They are strong but flexible tissues which support the trachea or the windpipe while still allowing it to move and flex during breathing. Additionally these cartilage rings are C-shaped to provide room for the esophagus, which lies along the back side of the trachea.

6. Functions of the larynx includes;
To protect the airway from choking on material in the throat
to regulate the flow of air into our lungs
The production of sounds used for speech 
Larynx is part of the respiratory system and is located between the pharynx and the trachea. Humans use larynx to breathe, talk and swallow. 

7. Structures that make up the pathway of air through the respiratory system starting with the external nares; We start with; External nares, nasal cavity, internal nares, nasopharynx, laryngopharynx,oropharynx, larynx, trachea, primary bronchus, secondary bronchus, tertiary bronchus, bronchiole, terminal bronchiole, respiratory bronchiole, alveolar duct, alveolar sac and alveolus.