Lecture 2

Organization of the Respiratory System

The lungs and thoracic cavity

Nasal Cavity, Pharynx, Larynx (Vocal cords), Trachea, Bronchi, Bronchioles

Cartilaginous rings keep the larynx and trachea from collapsing


Primary bronchi branches about 24 times (brown parts are collapsible)
Branching of airways increases the number of branches, total cross sectional area, and decreases air flow velocity


Diaphragm is a skeletal muscle, contracts (flattens out), relaxes (curves)

Right lung has Superior, middle, and inferior lobe


Left lung only has superior and inferior lobe


Fissures allows lungs to move around


60% of total lung volume is found in right lung


Bottom of lungs are curved because that's the way the diaphragm shapes it.


Blood flow in upper region effected by pressure (at apex)

Pleural Sacs Enclose Lungs:

  1. Fluid Filled (25-30mL)
  2. Provide a slippery surface
  3. Holds the lungs tight against the thoracic wall due to the cohesiveness of water.

Physically connects lung to chest wall (Parietal membrane is glued to chest wall => fluid -> visceral membrane glued to lungs)


Cohesive nature of water molecules allows these layers to slide but they are inseperable.


Elastic Recoil -> lung collapses

Muscles used during breathing

Inspiration: diaphragm, external intercostals, scalenes, sternocleidomastoids (quiet restful breathing, elastic recoil lungs return to original)

Expiration: Internal intercostals, abdominal muslces, Ribcage rotates up creates more space

The Bronchi and Alveoli

Respiratory Tract= Conducting zone + Respiratory zone

Conducting Zone:
-Cartilaginous rings
-Non Collapsible airway
-Hyaline Cartilage
-No gas exchange

Conducting Bronchioles:

  • Terminal bronchiole
    -Collapsible airway

Respiratory Zone:
-Collapsible Airway
-Gas exchange
-Respiratory bronchiole

Terminal Bronchiole:
Has smooth muscle
No Alveoli

Respiratory Bronchiole:
Has Alveoli
Elastic fibers allow alveoli to return to normal size (elastic recoil) active inspiration/passive exhalation (resting)

Bronchiole circulation is a branch of systemic circulation
Bronchiole artery and vein
Bronchiole nerve (some control over this, central/local)


Lymphatic vessel: gets rid of fluid in lungs (interstitial space)

Type I alveolar cells:
Flattened out
Thin
Gas exchange
Air as close to blood as possible (capillary beds between each alveoli)
Single sheet of blood between the alveoli (not seen in any other part of the body)

Type II alveolar cells:
Secrete surfactant (creates mucus)
If a new type I cell is needed these can differentiate into one.


Equal # of type I and type II

Alveolar Macrophages:
protective mechanism
wander around surface of alveoli



Thin film where surfactant is on
Same gas pressures from alveoli to alveoli

Optimize gas exchange by making distance as short as possible, large surface area
Less than 1 micron = fast diffusion

COPD: progressive airflow obstruction, inflammation in the airways, and breakdown of the walls of alveoli- creating a large air space where there once were many smaller ones (lose septeum/wall between alveoli). This reduces the surface area of the lungs and decreases gas exchange with the blood.


  1. Emphysema
  2. Chronic bronchitis

Smoking is a major cause as well as air pollution, chemical fumes, or dust.

Emphysema

Smoking -> Increase Protease -> loss of elastic fibers -> Emphysema

The wall breaks down, decreases surface area, rate of diffusion decreases

Protease attacks proteins, breaks them down, can't function correctly, lose fibers, breaks down septum

Black lung disease or Coal Miners Disease:
Coal is being deposited in the alveoli, inflammatory response, stiff lungs
Hypertrophy: heart works harder, gets bigger

Mucociliary Clearance (elevator):
Airway Epithelium facilitate warming, humidifying, and filtering of air as it passes towards alveoli

Filtering: sticky mucus along surface of conducting airway, particles get stuck in mucus, elevated up and out of lung

Elevator: lining of airway, epithelial (separate compartments), made up of a single layer of cells. Goblet cells are between cilia, produce mucus.
Cilia at end of cells, motile system coordinates pushing fluid, surrounded by pericilliary saline fluid.

If we don't have normal function of the elevator, extremely likely to develop infections. Only one cell layer to outside environment

Active trans-epithelial chloride secretion produces the saline (pericilliary) layer Without this, mucus gets thick, infection is likely (occurs in people with CF)