Histology (pie for finals)

Question 1

List the functions of the respiratory system

Answer 1

• Supplies oxygen to the blood for delivery to cells throughout the body.
• Removes carbon dioxide that has been accumulated in the blood from the tissues of the body.
• Phonation.
• Olfaction (smell)
• Lungs function in blood pressure control via renin-angiotensin system

Question 2

The nasal cavity provides an extensive area for what to happen to the inspired air ?

Answer 2

1. Warming
2. Moistening
3. Filtering

Question 3

What is the roof of the nasal cavity lined by ?

Answer 3

Specialised olfactory epithelium

Question 4

Describe the linning of the nasal cavity

Answer 4

• The initial part (the vestibule) is lined by keratinised stratified squamous epithelium
• Deeper into the nasal cavity kertain is lost ==> lining becomes just stratified squamous epithelium
• Deeper still it changes again to the epithelium that lines nearly all of the rest of the conducting part of the respiratory system = Respiratory Epithelium (pseudostratified ciliated columnar epithelium with goblet cells)

Question 5

What is the lining of the oropharynx and anterior (lingual) surface and upper part of the posterior surface of the epiglottis?

Answer 5

Non-keratinized stratified squamous epithelium (Because the oropharynx transmits both air and swallowed food, it must resist abrasion)

Question 6

What is the lining of the larynx ?

Answer 6

• The walls of the larynx are lined by respiratory epithelium
• The vocal folds and adjacent structures, are covered with stratified squamous epithelium.

Question 7

The trachea is continuous with the larynx and terminates by dividing into the main bronchi. What does it contain ?

Answer 7

15-20 ‘C’ shaped rings of cartilage

Question 8

What is the lining of the trachea ?

Answer 8

Respiratory epithelium

Question 9

The trachea divides into 2 main (primary) bronchi, what is the lining of these bronchi ?

Answer 9

Respiratory epithelium

Question 10

As bronchi branch and become smaller the cartilage becomes more discontinuous and is finally lost. These smaller airways lacking cartilage are called what?

Answer 10

Bronchioles

Question 11

What is the name of the smallest bronchioles that lack respiratory function (lack gas exchange)

Answer 11

Terminal bronchioles (up until this point the bronchioles have not had respiratory function)

Question 12

What do the terminal bronchioles branch into and what is important about their function ?

Answer 12

They branch to give rise to the first part of the respiratory tree that has respiratory function, the respiratory bronchioles.

Question 13

Describe the lining of bronchioles up until terminal bronchioles

Answer 13

• The respiratory epithelium undergoes changes with the columnar component changing to cuboidal as you progress down the respiratory tree to the smallest bronchioles
• Terminal Bronchioles are lined with cuboidal ciliated epithelium

Question 14

The conducting portion of the airways extends from…

Answer 14

The trachea to the terminal bronchioles (No exchange of oxygen/CO2 with blood occurs in these airways)

Question 15

What marks the begining of the respiratory portion of the airways (where gas exchange occurs)

Answer 15

The respiratory bronchioles

Question 16

What interupts the coninuity of the respiratory bronchioles ?

Answer 16

The alveoli

Question 17

Describe the appearance of alveoli and state their main function

Answer 17

• The alveoli are the terminal portions of the bronchial tree and are responsible for the spongy nature of the lungs. They resemble thin-walled pockets similar to a honeycomb.
• Main function = within them oxygen and CO2 are exchanged

Question 18

What is the lining of alveoli ?

Answer 18

The alveoli are lined by an epithelium that consists of two cell types: Type I alveolar cells and Type II alveolar cells

Question 19

What are alveolar cells also called ?

Answer 19

Pneumocytes

Question 20

Describe the function of type I alveolar cells (pneumocytes) which line alveoli

Answer 20

• They are simple squamous epithelium that lines the alveolar surfaces covering over 90% of the alveolar surface.
• These cells provide a barrier of minimal thickness that is permeable to gases.

Question 21

Describe the function of type II alveolar cells (pneumocytes) which line alveoli

Answer 21

• They are polygonal in shape, the free surface is covered by microvilli and the cytoplasm displays dense membrane bound lamellar bodies which contain surfactant.
• The surfactant is released by exocytosis and spreads over the pulmonary surface to reduce the surface tension at the air-fluid interface. This reduces the tendency for the alveoli to collapse at the end of expiration.

Question 22

Alongside the 2 types of pneumocytes found in alveoli, what is the 3rd type of cell found here and its function ?

Answer 22

• Also present in the alveoli are alveolar macrophages (dust cells) = free cells either in the septa or migrating over the luminal surfaces of the alveoli
• They phagocytose inhaled particles that may have escaped entrapment by the mucous lining of the airway. They typically will migrate up the bronchial tree, transported by ciliary action, to the pharynx where they are swallowed

Question 23

What comprises the air-blood barrier ?

Answer 23

The air- blood barrier consists of the Type I alveolar cell, the endothelial cell and the basal lamina of each. It can be as thin as 200-600nm