Lung microanatomy

Question 1

Describe branching of the airway

Answer 1

larynx turns into the trachea which branches into the left and right primary bronchi > secondary/lobar bronchi go to each lob (3 in the right, 2 in the left) > segmental bronchi aerate segments of the lungs (10 in right, 8 in left)

Question 2

significance of lung segments

Answer 2

Each has its own air and blood supply, and functions separately from the others. Disease in one segment can be surgically resected

Question 3

What is the visceral pleura made of

Answer 3

elastic fibrocollagenous tissue embedded with small amounts
of smooth muscle, and contains nerves, lymphatics and blood vessels, covered by a surface layer of mesothelial cellselastic fibrocollagenous tissue embedded with small amounts
of smooth muscle, and contains nerves, lymphatics and blood vessels, covered by a surface layer of mesothelial cells

Question 4

Compare cartilage in the trachea and the primary bronchi

Answer 4

The trachea contains about 20 “c-shaped” cartilagenous rings along its length, connected posteriorly by the trachealis muscle, whereas primary bronchi have segmented cartilagenous
plates around their entire diameter. The trachea contains about 20 “c-shaped” cartilagenous rings along its length, connected posteriorly by the trachealis muscle, whereas primary bronchi have segmented cartilagenous
plates around their entire diameter.

Question 5

Histology of trachea and bronchi

Answer 5

Mucosa: inner pseudostratified epithelial layer and a lamina propria. Submucosa: connective tissue, the cartilagenous layer and an adventitia connecting them to surrounding tissues. Muscularis: Larger bronchi contain a circumferential layer of smooth muscle between the epithelial layer and the submucosa, which is not continuous in smaller bronchi or in the trachea. Epithelium: ciliated epithelial cells, goblet cells, and basal cells and some neuroendocrine cells

Question 6

Histology of bronchioles

Answer 6

smooth muscle underlies the lamina propria. They have ciliated cells and goblet cells in the epithelial layer

Question 7

What are Clara cells and where are they located

Answer 7

Secrete surface active substances in terminal bronchiole epithelium closer to the exchange system

Question 8

What is Cystic fibrosis

Answer 8

Homozygous recessive disease - chronic congestive disease associated with defect in control of chloride transport in epithelial cells. Patients have chronic infections and respiratory failure

Question 9

What is Kartageners syndrome

Answer 9

. severe genetic defect characterized by chronic respiratory congestion and infections. It results from immotile cilia, usually due to defects in dynein arms.

Question 10

Histological changes from smoking/pollution

Answer 10

leads to a progressive loss of ciliated cells, starting with a loss in synchrony of the cilia “wave”. Ciliated cells become gradually replaced with squamous cells as chronic coughing is used to clear congestion

Question 11

Histology of respiratory bronchioles

Answer 11

Smooth muscle layer, epithelial layer containing primarily Clara cells. Branch into alveolar ducts which end in alveolar saccules

Question 12

Histology of alveoli

Answer 12

Each alveoli is separated by interavleolar septa comprised of fibroelastic basal lamina and cells. Capillaries penetrate the septa

Question 13

What structures do dissolved gases pass through to get into the capillary

Answer 13

surfactant layer > plasma membranes and cytoplasm of type I cells > common basal lamina > capillary endothelial cell plasma membrane and cytoplasm > capillary lumen

Question 14

how many plasma membranes must an oxygen molecule pass through to reach the hemoglobin in an RBC

Answer 14

5: Both sides of the alveolar endothelial cells, both sides of a capillary endothelial cell then through one side of the RBC

Question 15

How are type I cells replenished

Answer 15

Type I cells are terminall differentiated and do not divide. They are replenished by division of type II cells (their progenitors)

Question 16

Function of surfactant

Answer 16

Coats inner type I cells exposed to air, lowers surface tension and prevents lung collapse/ drying.

Question 17

Describe alveolar defense

Answer 17

Monocytes, neutrophils and fibroblasts are located in the alveolar septa. Alveolar macrophages can enter the alveolar space where they ingest inhaled particles, then they can pass into lung lymphatics and function as antigen presenting cells.

Question 18

Disease that results in loss of elasticity

Answer 18

Emphasema: patients prone to this diease have an alpha1-antitrypsin deficiency which destroys elastin in alveolar septa. Fibrotic disease: fibroblasts produce excess collagen which impairs expansion and gas exchange

Question 19

Vasculature supplying the lungs

Answer 19

bronchial arteries from aorta and pulmonary arteries from right ventricle. Pulmonary arteries pick up blood from lungs, bronchial arteries supply oxygen to conduction system

Question 20

explain black lung and silicosis

Answer 20

Macrophages in the alveoli ingest coal or silicone in the lung but cant digest it and they die. Other macrophages ingest the dead macrophages and also die.