Block 3 Respitory Histology Part 1

The primary role of Type II pneumocytes (also called Type II alveolar cells or foam cells) is the production of surfactant. In addition, Type II pneumocytes divide to produce daughter cells which can differentiate into either Type I pneumocytes or Type II pneumocytes.

Type II pneumocytes do divide and give rise to daughter cells, some of which can differentiate into the very squamous Type I pneumocytes that line most of the lumenal surface of alveoli.

Respiratory epithelium is found in the nasal cavities, in the trachea and in both the extrapulmonary and intrapulmonary bronchi. It is not found in alveoli, where it is necessary to minimize diffusion distances by the use of simple squamous epithelia.

Goblet cells and ciliated epithelial cells are both absent from the simple squamous epithelia associated with the alveoli. Hence, this is the correct answer for this EXCEPT question.

All macrophages in the human body, including alveolar macrophages, are derived from circulating blood monocytes.

Simple squamous epithelia would be the best type of epithelium for minimizing diffusional distances for oxygen and CO2. Indeed, this is the type of epithelium associated with alveolar septa. Type I pneumocytes are highly flattened cells and the capillary endothelium is a highly flattened simple squamous epithelium.

A: This is a major function of "respiratory" epithelium, which is a ciliated, pseudostratified columnar epithelium, containing goblet cells. The goblet cells release mucus onto the epithelium, This mucus can trapmparticulate materials in inhaled air. The coordinated activity of the cilia on the epithelium sweeps the mucis layer (with its trapped material) up the respirarory airways to the oropharynx, where it can be swallowed.

The trachealis muscle contracts during coughing and during exhalation. During inhalation, one wants the airways to expand and increase in volume and hence would not want the smooth muscle in the trachealis muscle to contract at that time.

The lumenal surfaces of alveoli are coated with surfactant, which has been secreted by Type II pneumocytes. Surfactant contains proteins and phospholipids. The phospholipids reduce the surface tension and allow the alveoli to be easily inflated. Phospholipids have detergent-like properties (amphipathic compounds containing both hydrophilic and hydrophobic groups).

This is the correct order of airways through which air passes during inhalation.

The larynx possesses both skeletal muscle (vocalis muscle) and cartilage (cricoid and thyroid cartilages) and hence this is a correct answer to this question.

This is an incorrect statement and hence is the correct answer for this EXCEPT question. Surfactant is not produced by any of the cell types in the respiratory epithelium that covers the lumenal surface of the bronchi. Surfactant is produced by Type II pneumocytes associated with the alveoli.

XTRA---Bronchioles differ from bronchi in two very important ways. First, they usually lack the cartilage plates that support the walls of the bronchi. Second, the bronchioles have a relatively greater amount of Smooth Muscle in their walls than bronchi. These two distinct microanatomic features allow the bronchiole's walls to constrict, thereby providing a mechanism for controlling the flow of air to the more distal portion of the lung

The recoil of longitudinally oriented elastic fibers (which are stretched during inhalation) contributes to the shortening of the airways during exhalation. Shortening the airways helps to decrease the total air volume of the respiratory tract.

The heat for warming the inspired air comes from thin walled venous vessels in the connectives under the epithelium and is not derived from the cells of the epithelium.

Both bronchi and bronchioles possess smooth muscle and hence this is the correct answer

REMEMBER----Bronchioles differ from bronchi in two very important ways. First, they usually lack the cartilage plates that support the walls of the bronchi. Second, the bronchioles have a-- relatively greater amount of Smooth Muscle -- in their walls than bronchi. These two distinct microanatomic features allow the bronchiole's walls to constrict, thereby providing a mechanism for controlling the flow of air to the more distal portion of the lung

The correct answer is B. The larynx contains striated (skeletal) muscle in the vocalis muscles. Hence, this is not a true statement and hence is the correct answer to this EXCEPT question.

Bronchioles do not contain cartilage in their walls. Arterial branches follow the bronchioles and hence this is a correct answer for this question

C: This is true. The volume of the alveolar spaces (individually and collectively) changes during each cycle of inspiration and exhalation. The reduction of alveolar volume during exhalation is due to passive recoil of elastic fibers located in the alveolar septa.

Type of epithelium - not correct--Intrapulmonary bronchi are lined by respiratory epithelium (ciliated pseudostratified columnar epithelium) while bronchioles are lined by a simple epithelium (simple cuboidal or simple columnar). Hence, this is an incorrect answer.

The correct answer is: Association with pulmonary arteries
Pulomary arteries follow and branch with the intrapulmonary airways, both the intrapulmonary bronchi and the bronchioles. Hence, this is the correct answer.

This is correct. Alveolar capillaries tend to be larger in diameter than capillaries elsewhere in the body. This most likely reflects the fact that blood flow in the pulmonary system is designed for high flow but low pressure and low resistance.