Lesson 2: Lower Respiratory Tract

Question 1

Lower Respiratory
Tract

Answer 1

At the level of your armpit the trachea branches into two
smaller passageways called bronchi (singular; bronchus).
One bronchus enters each lung.

Inside the lung, each bronchus divides many times to
produce a network of finer and finer tubes called
bronchioles.

Like the trachea and nasal passages, the bronchi and
bronchioles are lined with a ciliated mucous
membrane.

Question 2

The Alveoli

Answer 2

Each bronchiole ends in a grape – like cluster of tiny sacs called alveoli (singular; alveolus).

It is in the alveoli that gas
exchange takes place.

The wall of each alveolus is only one cell thick and is adjacent to a network of capillaries. Most of the
gas exchange takes place through simple diffusion through the wall
of the alveolus and the wall of the capillary network surrounding it.
The entire arrangement of bronchioles and alveoli is kept in a
relatively permanent position by elastic connective tissue that fills
the spaces between the individual structures.

The alveoli are also lined with a lubricating lipoprotein film that keeps them from collapsing.

Question 3

The Lungs

Answer 3

Each lung is divided into lobes. The right lung has three lobes and the left
lung has only two (to accommodate the heart).

Each lobe is made up of lobules, each with its own bronchiole.

The lungs are enveloped in layers of tissue called pleura (singular; pleuron).
This flexible membrane contains the
ungs while allowing them to expand and contract during inspiration and expiration.

Each pleuron is made up of two layers separated by a thin film of fluid.