Respiratory system Histology

Question 1

Describe the histology of the trachea

Answer 1

3 layers: mucosa, submucosa and adventitia.
C-shaped hyaline cartilage is in the adventitia
Open ends are connected by smooth muscle called trachealis muscle
Contraction of trachealis muscle decreases diameter of lumen during inhalation leading to an increased air flow

Question 2

Describe the mucosa of the trachea

Answer 2

Composed of respiratory epithelium (composed of ciliated columnar cells, goblet cells, basal cells, brush cells, DNES) lamina propria and elastic fibres

Question 3

Describe the submucosa of the trachea

Answer 3

Made of dense, irregular fibroelastic connective tissue housing numerous mucous and seromucous glands
Blood vessels and lymphoid elements

Question 4

Describe the adventitia of the trachea

Answer 4

Houses the c-shaped hyaline cartilage
Contains fibroelastic connective tissue

Question 5

Describe the structure of the main bronchus

Answer 5

Smaller diameter and thinner walls
Each bronchus has a pulmonary artery and vein

Question 6

Describe the structure of secondary bronchi

Answer 6

Left lung has 2 secondary bronchi
Right lung has 3 lobes so 3 secondary bronchi
Secondary bronchi are round
Has smooth muscle located at interface between lamina propria and submucosa
Thinner walls, less hyaline cartilage plates and short epithelial lining cells

Question 7

Describe the structure of bronchioles

Answer 7

No cartilage
Smaller diameter
Club cells in epithelial lining

Question 8

What are the functions of club cells

Answer 8

Produce surfactant like material to reduce ST of bronchioles
Divide to regenerate the bronchiolar epithelium

Question 9

Describe the structure of terminal bronchioles

Answer 9

Narrow lamina propria consist of fibroelastic connective tissue and coated with smooth muscle

Question 10

Describe the structure of respiratory bronchioles

Answer 10

Has simple cuboidal epithelium with club cells and ciliated cells
Has alveoli and ends with alveolar duct
Narrow in diameter

Question 11

Describe the histology of alveolar duct

Answer 11

A continuous sequence of alveoli

Question 12

Describe the histology of alveoli

Answer 12

They are air sacs containing type 1 & 2 pneumocytes
Alveolar macrophages on epithelial lining to maintain a sterile environment within the lungs by phagocytosing dust and other inhaled particles

Question 13

What is the air-blood interface

Answer 13

Part of the internalveolar septum transversed by oxygen and co2
In lung = oxygen exchanged for co2 carried by blood
In tissues of body = co2 exchanged for oxygen carried by blood

Question 14

Name the defence mechanisms of the respiratory system and its functions

Answer 14

Mucus layer: traps pathogens and other particles from reaching lungs

Alveolar macrophages: type of white blood cell and eliminate any deposited particle and digest them

Alveolar epithelial cells: type 1 & 2 pneumocytes which recruit inflammatory cells by releasing arachidonic acid deviates

Secretory IgAs: neutralise toxins and bacteria. block entry of bacteria across epithelium