Respiratory System - Lung L19

Question 1

The flow of air through the lungs

Answer 1

Trachea -> bronchi -> bronchioles -> alveoli

Question 2

Function of the trachea

Answer 2

Also known as the windpipe, it serves as the main passage for air to move in and out of the lungs.

Question 3

Bronchi

Answer 3

The trachea splits into two main bronchi (right and left), each leading to one lung, where they further divide into smaller branches.

Question 4

Bronchioles (looks like roots)

Answer 4

These are smaller branches of the bronchi that lead air deeper into the lungs. They continue to branch and become narrower as they distribute air throughout the lung.

Question 5

Alveoli

Answer 5

These are tiny, balloon-like structures at the end of the bronchioles where oxygen and carbon dioxide are exchanged with the blood.

Question 6

What does the lung look like? Label lobal bronchi, bronchioles, larnyx, tracheae, main bronchi

Answer 6

Question 7

Why do the branches get narrower and narrower?

Answer 7

The primary goal is to get down to the very thin blood air barrier, with all the little air sacs also known as alveoli

Question 8

Which lung is bigger and how many lobes does it have?

Answer 8

The right lung is bigger - it has three lobes while the left lung only has two.

Question 9

Beyond which branch of the airways indivates less defence mechanisms?

Answer 9

16-17, the higher, the more critical

Question 10

Main principle of the trachea

Answer 10

Needs to stay open, because if it collapses or damages, then there is no air going into your lungs.

Question 11

The main feature of the trachea that keeps airways open

Answer 11

C - shaped rings of cartilage - free ends of the cartilage are connected by the trachealis muscle (smooth), and contract narrows the diameter of the trachea.

Question 12

What is the trachea lined with? What type of cell?

Answer 12

Ciliated epithelium (pseudostratified columnar)
Cilia transport a mucous sheet upwards to the nasopharynx.

Question 13

Where does the esophagus sit to the trachea?

Answer 13

Posterior - it lies in the shallow groove formed by the trachealis muscle

Question 14

What is the order of the wall of a bronchus

Answer 14

Air lumen -> mucosa (columnar ciliated epithelium, goblet cells) -> lamnia propria -> submucosa (mucus glands) -> cartilage -> adventitia

Question 15

Air lumen

Answer 15

the open space within the bronchus where air passes through.

Question 16

Mucosa with columnar Ciliated Epithelium

Answer 16

Many of these cells have cilia, tiny hair-like structures that beat rhythmically to help move mucus and trapped particles out of the respiratory tract.
Interspersed among the ciliated cells, goblet cells secrete mucus, which moistens the lining of the airway and traps dust, pathogens, and other particulate matter.

Question 17

Function of the wall of a bronchus

Answer 17

• Keep the airways open
• Conduction
• Saturated H2O
• Mucus defence (trapping particles like pathogens and ciliary escalator

Question 18

If the air lumen is all about conditioning and travelling with the air, what is the wall of a bronchiole about?

Answer 18

Controlling the flow of air

Question 19

What cells are in the wall of a bronchiole?

Answer 19

Ciliated cuboidal

Question 20

What cells are found on the uppermost layer?

Answer 20

Club cells are non-ciliated, dome-shaped cells found in the epithelium of bronchioles. It is watery and contain anti-microbial properties.
They are most numerous in the terminal and respiratory bronchioles.
Club cells secrete a variety of substances, including club cell secretory protein (CCSP), which has anti-inflammatory and immunomodulatory properties. This protein is thought to play a role in protecting the bronchiolar epithelium from oxidative stress and inflammation.

Question 21

What is a condition that causes restriction to air flow?

Answer 21

Asthma

Question 22

What happens when you get asthma attack?

Answer 22

You get bronchoconstriction

Question 23

Function of inhalers

Answer 23

Beta-agonists in inhalers are commonly used to relax the smooth muscles in the airways, helping to open up the airways and make breathing easier.

Question 24

When is there no gas exchange?

Answer 24

At the terminal bronchiole

Question 25

What are alveolar ducts made of?

Answer 25

Alveoli

Question 26

Structure of the alveoli

Answer 26

Each alveolus is surrounded by a dense network of capillaries. The capillary walls, like the alveolar walls, are also very thin. This proximity and the thin barrier allow oxygen and carbon dioxide to diffuse efficiently between the blood and the alveoli.

Question 27

Type I pneumocytes

Answer 27

Type I alveolar cells - thin and flat is crucial for efficient gas exchange.
Large Surface Area: These cells are squamous epithelium (plate-like) and have large surface areas relative to their volume, which enhances their ability to facilitate gas diffusion.

Question 28

As the wall of the alveoli is so thin, when they deflate they will stick to each other, then how do you pull them apart?

Answer 28

Reduce that natural sticking by secreting a substance called surfactant.

Question 29

Type II Pneumocytes

Answer 29

Type II pneumocytes synthesize and secrete pulmonary surfactant, a crucial substance that decreases surface tension within the alveoli. (between air and the liquid layer). This reduction in surface tension prevents the alveoli from collapsing during exhalation, facilitating easier breathing and gas exchange.

Question 30

What is the alveoli macrophage?

Answer 30

A type of immune cell found within the alveoli, the tiny air sacs in the lungs, ingesting any particles, viruses, blood cells, haemorrhage fluids.

Question 31

Components of the diffusion barrier

Answer 31

Alveolar Air Space: This is the area within the alveoli filled with air. It is where the oxygen enters the lung.

Squamous Pneumocyte: These are also known as type I alveolar cells. They make up the majority of the alveolar surface and are extremely thin to facilitate the exchange of gases (like oxygen and carbon dioxide) between the air and the blood.

Basement Membrane of Squamous Pneumocyte: This is a thin, fibrous, extracellular matrix that underlies the squamous pneumocytes, providing structural support and acting as a selective filter for substances moving to and from the blood.

Basement Membrane of Capillary Endothelium: This membrane is similar to that of the squamous pneumocytes but is associated with the capillaries. It supports the endothelial cells that line the blood vessels.

Capillary Endothelium: This layer comprises endothelial cells that line the capillaries running through the alveoli. These cells help manage the exchange of gases by allowing oxygen to enter the blood and carbon dioxide to be released into the alveolar air.

Blood Plasma: This is the liquid component of blood, through which gases, nutrients, and waste products are transported. Oxygen dissolves in the plasma before diffusing into red blood cells.

Red Blood Cell: These cells carry oxygen bound to hemoglobin, transporting it from the lungs to tissues throughout the body and returning carbon dioxide to the lungs for exhalation.

Question 32

Variations along the length of the airway

Answer 32

Higher we need to defend and prepare the air, lower we need to control air flow and at the bottom we need efficient gas exchange (1. surface area, 2. energy demand)

Question 33

Defense in the respiratory system

Answer 33

Macrophage: These are immune cells that reside in tissues and have the ability to ingest and destroy pathogens and debris. In the lungs, alveolar macrophages play a crucial role in defending against inhaled particles and microorganisms.

Mucus: This is a sticky, viscous substance produced by cells in the airways. It traps particles, bacteria, and viruses, preventing them from reaching the delicate tissues of the lungs.

Question 34

Flow

Answer 34

Cartilage (Cart): This refers to the rigid structures within the larger airways, like the trachea and bronchi, which keep these airways open and prevent them from collapsing. Cartilage is crucial for maintaining open air passages for airflow.

Smooth Muscle (Sm Muscle): Smooth muscle in the bronchi and bronchioles can contract or relax to adjust the diameter of the airways, thereby regulating airflow and resistance in the respiratory system.

Question 35

Liquids

Answer 35

Mucus: As mentioned above, mucus serves to trap and remove particles and pathogens from the airways.
Chloride Cells (Cl Cell): Although not typically a primary focus in basic respiratory physiology, chloride cells might refer to cells involved in ion transport, which can influence the hydration of airway surfaces and mucus viscosity.
Surfactant: This is a complex mixture of lipids and proteins secreted by type II alveolar cells. Surfactant reduces surface tension within the alveoli, preventing their collapse during exhalation and easing the work of breathing.

Question 36

Main points of the airways

Answer 36

• Cartilage supports the large airways during inspiration, but does not continue beyond the
  smallest bronchi. Mucous glands stop there too.
• Thickness of the epithelium decreases as airway diameter decreases.
• The epithelium of the conducting airways contains secretory cells. Goblet cells secrete
  mucus in the large airways, Club cells release a serous (watery) secretion in bronchioles.
• Small airways have more smooth muscle (in spiral orientation) in relation to their size than large ones, but the muscle coat does not continue beyond the smallest bronchioles.

Question 37

Subdivisions of the lung

Answer 37

• Primary bronchi (2) are right and left main stem bronchi supplying each lung
• Secondary bronchi are lobar bronchi supplying lobes ( 2 on the left, 3 on the right)
• Tertiary bronchi are segmental bronchi supplying segments of the lung (8 on the left, 10 on the right.)
  Each segment has its own air and blood supply. Thus when a localised tumour occurs in the lung, a surgeon who knows the approx boundaries can remove one of more segments containing the tumour without excessive leakage of air or blood from neighbouring segments,

Question 38

What is pleurae?

Answer 38

A smooth membrane which covers each lung; and also lines the thoracic cavity in which the lung sits. The two membranes (pleurae) are continuous at the root of the lung (hilum).

Question 39

Structure of Pleurae

Answer 39

The pleurae are smooth membranes that cover each lung and also line the thoracic cavity where the lung sits. Each lung is enveloped by its pleural membrane.
There are two pleurae for each lung: the visceral pleura, which is attached directly to the lungs, and the parietal pleura, which lines the chest wall.
The space between the two pleurae is called the pleural cavity.

Question 40

Function and Importance of Pleural Fluid

Answer 40

A thin film of fluid separates the two pleurae. This fluid is crucial because it allows the pleurae to slide effortlessly over each other during respiratory movements such as breathing.
The fluid also prevents the two pleurae from being pulled apart or sticking together. This helps maintain smooth lung movement within the thoracic cavity.

Question 41

Mechanical Dynamics of the pleurae

Answer 41

The pleural fluid and its enclosing structures allow the lungs to follow the movements of the thoracic wall and diaphragm closely.
When the thoracic wall moves inward or outward (e.g., during breathing), the lungs follow these movements due to the cohesive action of the pleural fluid and membranes.
The diaphragm’s movements (upward or downward during breathing) also influence the lungs in a similar manner, ensuring the air movement that facilitates respiration.

Question 42

Role of Ribcage Movement

Answer 42

Role of Ribcage Movement:
About 25% of the air movement during breathing comes from the movement of the ribcage.

Inspiration (Breathing In):
Inspiration is an active process, meaning it requires muscular effort.
It involves the contraction of the external intercostal muscles, which run obliquely (diagonally) between the ribs. These muscles lift and expand the ribcage, creating more space in the thoracic cavity, allowing air to enter the lungs.

Expiration (Breathing Out):
Expiration during quiet breathing is passive, meaning no muscular effort is required.
The ribcage simply returns to its resting position after inspiration, allowing air to exit the lungs.

Question 43

Breathing During Exercise

Answer 43

Active Involvement of Intercostal Muscles:
During exercise, both the external and internal intercostal muscles are actively involved in breathing to meet the increased oxygen demand and carbon dioxide elimination.

Question 44

External Intercostal Muscles

Answer 44

Function: These muscles help in inspiration.
Action: They contract to lift the ribs upwards and outwards, increasing the volume of the thoracic cavity, which pulls air into the lungs.
Visual Analogy: The image uses the analogy of a bucket handle lifting, which is similar to how the ribs move when the external intercostal muscles contract.

Question 45

Internal Intercostal Muscles

Answer 45

Function: These muscles assist in expiration, which becomes an active process during exercise (as opposed to being passive during quiet breathing).
Action: They run at right angles to the external intercostal muscles and contract to pull the ribs downwards and inwards, decreasing the thoracic cavity’s volume and pushing air out of the lungs.
Visual Analogy: Not explicitly shown in the analogy but can be imagined as the opposite movement of the bucket handle, where force is applied to pull it downwards.

Question 46

Rib Pivots

Answer 46

The ribs pivot at their joints with the vertebral column, allowing this upward and outward movement during inspiration and downward and inward movement during expiration.

Question 47

Muscle Orientation and Action

Answer 47

The orientation of the intercostal muscles relative to the ribs is crucial as it determines their role in changing the volume of the thoracic cavity during the breathing cycle.

Question 48

Structure and Function of the Diaphragm

Answer 48

The diaphragm is a dome-shaped muscular and fibrous structure that separates the thoracic (chest) cavity from the abdominal cavity.
It is primarily composed of a central tendon and muscular portions. The central tendon is a thin sheet of connective tissue (aponeurosis), and the muscular portions are on the lateral margins. The muscle is fast-acting skeletal muscle, innervated by the phrenic nerve.

Question 49

Role in Breathing

Answer 49

Inspiration: During inhalation, the diaphragm contracts and flattens, pulling downward. This action increases the volume of the thoracic cavity and decreases the pressure inside, causing air to flow into the lungs.

Expiration: Exhalation involves the relaxation of the diaphragm, which allows it to rise back to its dome shape, reducing the volume of the thoracic cavity and expelling air from the lungs.

Question 50

Efficiency of the Diaphragm

Answer 50

The diaphragm is responsible for about 75% of the air movement during quiet breathing. Its efficiency may decrease during exercise when additional muscles come into play to assist with rapid and deep breathing.