Breathing Mechanics Overview

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Questions and Answers

What is the primary role of ribs 11 and 12 during respiration?

They are responsible for upward movement of the sternum.

They contribute to a major change in lung volume.

They participate in a minor change to the chest contour. (correct)

They primarily assist in deep inhalation.

What is the function of the intrapleural space?

It directly facilitates the movement of air in and out of the lungs.

It houses the serous membrane.

It contains lung tissue.

It holds intrapleural fluid and maintains negative pressure. (correct)

What is true about the pleurae in relation to the lungs?

The parietal pleura directly covers the surface of the lung.

The visceral pleura is the outer layer of the lung. (correct)

The pleurae are composed of muscle tissue.

The visceral pleura lines the thoracic cavity.

What happens to the thoracic diameter during the backward movement of the lower sternum?

It decreases slightly. Signup and view all the answers

Which statement accurately describes the 'caliper' motion of the ribs?

It involves the ribs being pulled upward and outward. Signup and view all the answers

What is a key feature of the right lung compared to the left lung?

The right lung has 3 lobes. Signup and view all the answers

Which fissures are found in the right lung?

Oblique and horizontal fissures. Signup and view all the answers

What anatomical structure is located in the mediastinum?

Esophagus Signup and view all the answers

What name is given to the part of the lung where the mainstem bronchi enter?

Hilum Signup and view all the answers

Why is the left lung smaller than the right lung?

It is smaller to accommodate the heart's apex. Signup and view all the answers

What is the relationship between alveolar radius and internal pressure according to Laplace's Law?

As the radius decreases, internal pressure increases. Signup and view all the answers

How does surfactant affect surface tension (ST) in the alveoli?

Surfactant decreases ST to stabilize the alveoli. Signup and view all the answers

What happens to surface tension (ST) during exhalation?

ST increases as alveolar size decreases. Signup and view all the answers

What is the formula represented by Laplace’s Law?

P = 2(ST) / r Signup and view all the answers

Which statement accurately describes airway resistance (RAW)?

RAW increases the force necessary to maintain airflow. Signup and view all the answers

What is the primary muscle of inspiration?

Diaphragm Signup and view all the answers

What does elastance measure in the context of lung mechanics?

The ability to return to original shape Signup and view all the answers

What defines compliance in lung mechanics?

The ease of lung distention Signup and view all the answers

What does a more negative intra-thoracic pressure indicate?

Increased lung expansion Signup and view all the answers

Which factor does NOT influence lung/chest wall elasticity?

Intra-thoracic pressure Signup and view all the answers

What is the formula used to calculate compliance?

C = ∆V / ∆P Signup and view all the answers

Which of the following best describes the thoracic cavity?

Contains the heart and lungs Signup and view all the answers

How is elastance calculated in the context of lung mechanics?

E = ∆P / ∆V Signup and view all the answers

What happens to the driving pressure if the viscosity of a fluid increases, according to Poiseuille's Law?

The driving pressure increases. Signup and view all the answers

Which factor contributes to increased airway resistance (RAW)?

Decreased diameter of the airways Signup and view all the answers

How is conductance (G) related to resistance (R) in the respiratory system?

Inversely related Signup and view all the answers

Which type of gas flow is characterized by orderly, parallel layers of fluid?

Laminar gas flow Signup and view all the answers

What does Reynolds' number (RN) indicate in terms of gas flow?

Whether gas flow is laminar or turbulent Signup and view all the answers

What is the relationship between the radius of a tube and the resistance according to the equation R = 8nl / πr^4?

Resistance decreases with increasing radius. Signup and view all the answers

Which of the following variables are inversely related to flow (GAW)?

Resistance (R) and conductance (G) Signup and view all the answers

What effect does branching of the airways have on airway resistance (RAW)?

Increases airway resistance. Signup and view all the answers

Study Notes

Rib Movement

Ribs 11-12 are termed "floating" ribs and contribute minimally to chest contour changes.
These ribs are moved in a "caliper" motion, involving upward and outward movement.

Pleurae

Comprises a serous membrane lining the lungs and thorax, with two layers:
- Visceral pleura (inner lining covering lung surfaces)
- Parietal pleura (outer layer lining the thoracic cavity)
The intrapleural space contains intrapleural fluid and has negative pressure.

Gross Anatomy of the Lungs

Right lung is larger and shorter (due to the liver), has three lobes and two fissures (horizontal and oblique).
Left lung is smaller (due to the heart's apex), has two lobes, one oblique fissure, and a lingula that represents the middle lobe.

Thoracic Cavity

Contains the mediastinum, which holds the heart, trachea, major blood vessels, and nerves.
The hilum is where the mainstem bronchi enter the lungs.
Consists of two pleural cavities and has a negative intra-thoracic (pleural) pressure compared to atmospheric pressure.

Diaphragm

Dome-shaped muscle dividing the thoracic and abdominal cavities.
Serves as the primary muscle for inspiration, innervated by the phrenic nerve.

Lung Mechanics

Elastance (E): The lung's ability to return to original shape after distortion, calculated as ΔP/ΔV.
Compliance (C): The ease of lung distension, calculated as ΔV/ΔP; inversely related to elastance.

Lung/Chest Wall Elasticity

Composed of tissues beneath the diaphragm, ligaments, cartilages, elastic fibers, and surfactant.
Surfactant decreases surface tension (ST) and pressure, thereby increasing compliance.

Surface Tension (ST)

Results from forces at liquid-gas interfaces, promoting alveolar collapse during exhalation.
Laplace’s Law shows that pressure increases with smaller alveoli (P = 2(ST)/r).

Airway Resistance (RAW)

Represents the force needed to maintain airflow in the respiratory system, calculated as ΔP/flow.
Increased RAW factors include decreased airway diameter and directional changes in airways.

Gas Flows and Airway Resistance

Poiseuille’s Law describes that driving pressure increases with fluid viscosity, tube length, or flow, particularly when tube radius decreases (R = 8nl/πr^4).
Conductance (G) relates to airflow capabilities and is inversely related to resistance: GAW = Flow/ΔP.

Types of Gas Flows

Different patterns exist:
- Laminar Flow: smooth and orderly.
- Turbulent Flow: chaotic and irregular.
- Transitional Flow: a mix of laminar and turbulent flow.
Reynold’s number (RN) indicates the flow type, determining whether it is laminar or turbulent.

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Description

This quiz explores the mechanics of breathing, focusing on the backward movement of the lower sternum during inhalation. It examines how these actions lead to changes in thoracic dimensions. Gain insights into the physiological processes involved in quiet breathing.