L14 & L15. Histology - Microanatomy of the Respiratory System

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Questions and Answers

What is the lifespan of olfactory sensory neurons?

3-6 months

10-20 days

30-60 days (correct)

1 year

What type of cells are responsible for olfactory transduction?

Sustentacular cells

Brush cells

Bipolar neurons (correct)

Basal cells

Where do the apical processes of the sensory cells terminate?

In the olfactory vesicle or knob (correct)

In sustentacular cells

At the basal layer of epithelial cells

In the lamina propria

What structure contains cilia with approximately 350 types of odorant receptors?

Olfactory vesicle Signup and view all the answers

What is the primary function of brush cells in the olfactory system?

General sensation Signup and view all the answers

Which component is involved in the activation of G-protein-linked receptors for odor perception?

Second messenger transduction Signup and view all the answers

How do olfactory sensory neurons compare to other types of neurons?

They are continuously replaced Signup and view all the answers

What characteristic distinguishes the axons of olfactory sensory neurons?

They form unmyelinated bundles Signup and view all the answers

What is the primary function of goblet cells in the respiratory system?

Trapping particulate matter through mucus Signup and view all the answers

Which type of cell in the olfactory epithelium provides metabolic and physical support?

Supporting (sustentacular) cells Signup and view all the answers

Which cells are precursors of other cell types in the respiratory epithelium?

Basal cells Signup and view all the answers

What distinguishes small granule cells from basal cells?

Contain secretory granules Signup and view all the answers

What is the main role of the capillary loops in the lamina propria of the respiratory system?

Warm incoming air Signup and view all the answers

Which type of epithelium is primarily found in the olfactory mucosa?

Pseudostratified columnar epithelium Signup and view all the answers

What is a notable characteristic of the epithelium lining the paranasal sinuses?

Continuous with the nasal cavity and slightly thinner Signup and view all the answers

What role do brush cells play in the respiratory system?

Supporting epithelial structure Signup and view all the answers

What is the fundamental composition of the lamina propria in the respiratory system?

Contains both mucus and serous glands Signup and view all the answers

What is the primary consequence of respiratory epithelium changing to stratified squamous epithelium?

Loss of cilia leading to impaired mucus removal. Signup and view all the answers

What function do goblet cells perform in the respiratory epithelium?

Trap inhaled dust and particles. Signup and view all the answers

Which characteristic is unique to neuroendocrine (small granule) cells in the respiratory system?

Basal granules released into connective tissue. Signup and view all the answers

What role do non-ciliated columnar cells, or brush cells, primarily serve?

General sensation. Signup and view all the answers

What structure separates the submucosa from the mucosa in the respiratory system?

Elastic tissue band. Signup and view all the answers

How do basel cells contribute to the epithelial lining of the respiratory system?

They serve as a reserve for stem cells. Signup and view all the answers

What happens to ciliated cells over time in the respiratory epithelium under pathological conditions?

Their numbers decrease significantly. Signup and view all the answers

What is the purpose of increased mucus secretion by goblet cells in response to irritation?

To trap and expel foreign particles. Signup and view all the answers

What type of connective tissue primarily composes the submucosa in the respiratory system?

Loose connective tissue with mixed glands. Signup and view all the answers

What marker can be used to visualize some small granule neuroendocrine cells?

Silver or dichromate salts. Signup and view all the answers

What is the primary function of Type II alveolar cells?

Produce surfactant to reduce surface tension Signup and view all the answers

Which component of surfactant is essential for maintaining the patency of the alveoli?

Phosphatidyl-choline Signup and view all the answers

What is the role of alveolar macrophages in the respiratory system?

Engage in the phagocytosis of pathogens Signup and view all the answers

Which statement about Type II alveolar cells is true?

They can proliferate into both Type I and Type II cells. Signup and view all the answers

What type of epithelium is initially present in the respiratory system?

Pseudostratified ciliated columnar epithelium Signup and view all the answers

Which cell type is involved in mucus secretion within the epithelial lining of the lungs?

Goblet cells Signup and view all the answers

What is the primary function of ciliated cells in the respiratory epithelium?

Transporting materials upward Signup and view all the answers

Which layer of the bronchial wall contains interlacing bundles of smooth muscle?

Mucosa Signup and view all the answers

As airways branch into smaller bronchi, which change occurs regarding cartilage?

Replacement by irregular plates of hyaline cartilage Signup and view all the answers

Which component is NOT part of the bronchial wall layers?

Epithelial membrane Signup and view all the answers

What might excess secretion from goblet cells lead to within the respiratory system?

Blockage of airways Signup and view all the answers

What defines the transition of the epithelium from pseudostratified ciliated columnar to ciliated columnar?

Continuous branching of airways Signup and view all the answers

What is the role of basal cells in the respiratory epithelium?

They serve as progenitor cells Signup and view all the answers

Study Notes

Respiratory System

The respiratory system is responsible for gas exchange between the body and the environment
The system consists of the nose, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli
Primary functions of the respiratory system are:
- Gas exchange
- Filter air from environmental pathogens
- Warm and humidify air
- Smell
- Vocalization
The respiratory system is lined with a special type of epithelium, called respiratory epithelium, that is a pseudostratified ciliated columnar epithelium with goblet cells
Respiratory epithelium is located in the nasal cavity, pharynx, larynx, trachea, bronchi, and bronchioles
The respiratory epithelium changes to stratified squamous epithelium in the upper portion of the larynx

Olfactory Mucosa

Located in the roof of the nasal cavity
Responsible for smell
Contains four types of cells that contribute to smell:
- Supporting (sustentacular) cells: Provide metabolic and physical support for olfactory receptors. They are tall, cylindrical cells with apical microvilli.
- Basal cells: They are small, conical cells with dark ovoid nuclei. They act as a stem cell population, regenerating other cells.
- Sensory (olfactory) cells: Bipolar neurons. They are spindle-shaped cells with an apical dendrite that extends to the surface. The apical process ends in a bulbous expansion called the olfactory vesicle or knob, which contains 10-20 modified cilia. The proximal part of the cell extends into the lamina propria as an axon, which continues to the olfactory bulb of the brain.
- Brush cells: possess apical microvilli. They are thought to function in general sensation
The olfactory neurons are unusual in that they are continuously replaced and have only a 30-60 day life span
The olfactory transduction pathway begins with odorant binding to G-protein-linked receptors on the olfactory cilia which triggers a cascade of events ultimately leading to the generation of an action potential that is transmitted to the brain

Lamina Propria

Located beneath the epithelium
Contains a mix of connective tissue, blood vessels and glands
Important functions:
- Support for respiratory epithelium: Provides structural support for the epithelium.
- Defense: It houses immune cells that defend against pathogens.
- Warming and humidifying air: Capillary loops in the lamina propria warm the incoming air.

Submucosa

Located beneath the lamina propria
Contains loose connective tissue, glands, and lymphatic tissue
Provides additional support for the epithelium and provides a pathway for blood vessels and nerves.
Contains glands that secrete mucus which helps to trap inhaled particles

Trachea

Connects the larynx to the bronchi
It is a tube lined with respiratory epithelium and goblet cells
Contains C-shaped hyaline cartilage rings that provide structural support
The rings of cartilage allow the trachea to expand and contract during breathing.

Bronchi

Division of the trachea that leads into the lungs
Histologically similar to the trachea, lining is composed of respiratory epithelium, goblet cells, and hyaline cartilage rings

Bronchioles

Smaller branches of the bronchi
Lining epithelium gradually changes from pseudostratified columnar to simple cuboidal in the bronchioles
Contain less cartilage and more smooth muscle in their walls
Smooth muscle aids in controlling air flow into and out of the lungs

Alveoli

The functional unit of the lungs
Site of gas exchange between the lungs and blood
Thin-walled air sacs surrounded by capillaries
The walls of the alveoli are composed of two types of cells:
- Type I alveolar cells: Flattened cells that make up the majority of the alveolar surface. They are involved in gas exchange.
- Type II alveolar cells: Smaller, cuboidal cells that produce surfactant. Surfactant acts as a detergent, reducing the surface tension of the alveoli and preventing them from collapsing.

Alveolar Macrophages

Also called dust cells
Found within the interstitium of the alveolar walls and in the alveolar lumen.
Highly phagocytic cells
Remove inhaled pollutants, bacteria, and other debris from the alveoli.

Respiratory Epithelium

The lining of the trachea and bronchi is a pseudostratified ciliated columnar epithelium with goblet cells.
Ciliated cells: Move mucus, trapped particles, and debris upward towards the pharynx for removal (mucociliary escalator)
Goblet cells: Secrete mucus, which traps inhaled particles and pathogens.

Summary: Respiratory Epithelium

Ciliated cells move mucus and debris towards the pharynx
Goblet cells secrete mucus to trap pollutants
Basement membrane connects the epithelium to the underlying connective tissue

Pulmonary Blood Supply

The lungs receive blood from two sources:
Pulmonary arteries: Carry deoxygenated blood from the right ventricle of the heart to the lungs.
Bronchial arteries: Carry oxygenated blood from the aorta to the lungs to supply their tissues.

Other Key Concepts

APUD system: The amine precursor uptake and decarboxylation (APUD) system is a group of cells that produce and secrete hormones. Small granule cells in the respiratory system are part of this system.

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Description

This quiz focuses on the respiratory system, highlighting its structure, functions, and the role of the respiratory epithelium. It also covers the olfactory mucosa and its importance in the sense of smell. Test your knowledge on the anatomy and functions of this vital system!