THE LUNGS

An alveolus is composed of several types of 3 different cells:

*Type I alveolar cells, Type II alveolar cells, & Alveolar macrophages*

Every alveolus is surrounded by

*blood capillaries*, and by *elastic fibers* that stretch during inhalation & recoil during expiration

Each lobe is divided into several

*bronchiopulmonary segments*

The respiratory airways are distinguishable by two tissues:

*hyaline cartilage & epithelium*

Both lungs have fissures that create

*lung lobes*.

bronchiopulmonary segments, in turn, are divided into many small

*lung lobules*, served by a bronchiole

The inner walls of the thorax are covered with

*parietal pleura*

In between the visceral and parietal pleura is which cavity?

*pleural cavity*

Together, the walls of an alveolus and the adjacent capillary walls are called the -

*respiratory membrane*

Two types of bronchioles:

*terminal bronchioles and respiratory bronchioles*

The cilia in the trachea (& bronchi) move mucus

*upward* toward the pharynx. The mucous moves as a sheet over the surface of the respiratory airways

The lungs are covered by a serous membrane called

*visceral pleura*

There are 3 progressively smaller sets of bronchi:

2 primary bronchi 5 secondary bronchi 20 tertiary bronchi As the bronchi get smaller, the cartilage changes from complete rings to mosaic tile-like plates

Purpose of *20 tertiary bronchi*

Bring air to bronchiopulmonary segments. The 10 tertiary bronchi in each lung have cartilage *plates* & are the smallest respiratory structures with cartilage.

Purpose of the *2 primary bronchi*

Bring air to lungs. Cartilage forms *complete rings*

What kind of cartilage does the trachea have? What is the purpose of the cartilage?

C-shaped rings of cartilage, keeps the airway open allowing expansion of the esophagus during swallowing

What do the *bronchioles* serve?

Lung lobules.

*Type I alveolar cells*

Make up most of the walls of an alveolus. Are simple squamous epithelium. Very thin, allowing rapid diffusion of respiratory gases which facilitates quick & thorough gas exchange

*Alveolar macrophages* (aka dust cells) are resident -

Phagocytes. They consume tiny debris from the air.

Purpose of *5 secondary bronchi*

Serves lobes of lung (3 in right, 2 in left lung). These have cartilage *plates*

*Terminal bronchioles* have walls of

Simple columnar ET. *Terminal bronchioles are the last structures in the conducting zone*

The walls of the *respiratory bronchioles* are made of

Simple cuboidal ET. Some alveoli branch directly off respiratory bronchioles.

Bronchioles do not have cartilage in their walls. Instead, they have -

Smooth muscles. These muscles are acted upon by the autonomic nervous system to increase/decrease the depth of breathing

*Type II alveolar cells* produce

Surfactant; This prevents the moist inside surfaces of the alveolus from sticking together.

*Alveolar ducts*, which follow respiratory bronchioles, terminate in

Terminate in alveolar sacs. *Alveolar ducts* are linear tubes of alveoli.

What kind of epithelium is in the walls of the *bronchi*?

The bronchi has pseudostratified columnar ET & cartilage in their walls

How many lobes are in the right lung & the left lung? What is each lobe served by?

There are *three lobes in the right lung* & *two lobes in the left lung*. Each lobe is served by a secondary bronchus.

How many bronchiopulmonary segments are in each lung? What is each served by?

There are a *total of 10 in each lung*. Each bronchiopulmonary segment is served by a tertiary bronchus.

What happens when alveolar macrophages are overworked (as happens with smoking)?

They rupture & release enzymes from their lysosomes. This breaks down nearby alveolar walls & interstitial elastic tissue, reducing alveolar surface area & elasticity.

Further, each type of respiratory airway serves (moves air to)

a different area in the thorax

*Alveolar sacs* are clusters of -

alveoli

*Alveoli* are functional units of the lung and are -

microscopic gas exchange chamber

The pleural cavity contains lubricating fluid so the outer surface of the lungs can -

move along inner surface of the thorax without friction during breathing

The lumen of the *trachea* is lines with -

pseudostratified columnar epithelium with cilia & goblet cells

Epithelium varies between -

pseudostratified columnar, simple columnar, & simple cuboidal

Purpose of the *respiratory bronchioles* is to

send air to alveolar ducts. *The respiratory bronchioles are the first structures in the respiratory zone*

*Respiratory airways*, the second group of respiratory system structures, are all tubes, including 3 structures -

trachea, bronchi & terminal bronchioles