Question

2. Respiratory System: Identify: lungs, trachea, diaphragm Questions to answer: -what type of tissue makes up the respiratory system?

-why is the trachea made of cartilage?

-what is the anatomical location of the lungs and trachea?

-what structures are part of the bronchial tree?

-where does gas exchange occur in the lung?

-what gases are involved in gas exchange?

-describe the pressure and volume changes during inspiration and expiration

Answer 1

Respiratory system starts from nasopharynx to alveoli.

Nasopharynx , trachea and bronchioles is lined by ciliated pseudostratified columnar epithelium along with goblet cells , the goblet cells are responsible for mucus production. Whereas alveoli which is responsible for gaseous exchange is lined with simple squamous epithelium. The lung is covered by pleural membrane made of mesothelium . The bronchi , trachea are also made up of cartilage . The larynx , trachea , bronchi , pulmonary epithelium starts to occur at 4th week of gestation . They are endo dermal in origin . The splancnic mesoderm surrounding the foregut will give rise to connective tissue, cartilage and smooth muscle cells in lower respiratory tract .

Trachea is made of cartilage because cartilage is a flexible tissue . So while breathing it can extend and also provide stability to trachea preventing collapse . They are c shaped and have 20 rings which are stacked upon one another .

The lungs are located in thorax on either side of mediastinum, they are enclosed within the rib cage . They rest on the diaphgram . Lung consists of apex , base , 2 or 3 lobes , 3 surface and 3 border .

The trachea begins below the larynx and ends at carina the last tracheal ring where it bifurcates into 2 primary bronchi . It runs behind the sternum and posteriorly esophagus seen the verebral level of trachea is begins at c6 and ends at T4 .

Bronchial tree is starting from trachea which divides into 2 main primary bronchi one to right and one to left . Rt primary bronchi divides to supply 3 lobes of rt lung . Left bronchi divides to form 2 lobes of left lung . They further terminate as secondary bronchi , tertiary bronchi and bronchioles making up the bdonchial tree.

Gas exchange occurs in the alveoli. Which is called as air sac , they are arranged as clusters and are present at the termination of respiratory tree. The type 1 pneumocytes take part in gaseous exchange , wwhereas type 2 take part in remodelling of damaged alveoli.

Oxygen and carbon dioxide are involved , oxygen rich air reaches alveoli during inspiration, which diffuses along alveolar membrane and binds with hemoglobin . The co2 in the deoxygenated blood diffuses back from the vessels into alveoli and during expiration it is expired out .

During inspiration due to contraction of diaphragm and external intercostal muscles the volume of thoracic cavity increases and intrapleural pressure is decreased . While in expiration diaphgram attains its dome shape and relaxes thus the volume of thoracic cavity decreases and pressure increases.