1. Chapter 19 – Respiratory System
Trachea, Bronchial Tree, Lungs

2. Trachea
Extends from larynx into the thoracic cavity where it splits into the left and right bronchial tree

3. Trachea Structure Lined with ciliated mucous membrane
Membrane filters out particles and moves them up to the pharynx where they can be swallowed

4. Trachea
Structure
Tracheal wall contains about twenty C-shaped pieces of hyaline cartilage with smooth muscle and connective tissues between them
The cartilage prevents the trachea from collapsing and preventing air flow while the soft tissues between allow the esophagus to expand when food passes through it

5. Bronchial Tree
Branched airways that lead from the trachea to microscopic air sacs in the lungs

6. Bronchial Tree Branches
Right and left primary bronchi arise from the trachea
These are separated by a ridge of cartilage called the carina
Secondary (or lobar) bronchi branch from the primary bronchi
Three branch on the right and two branch on the left
Tertiary (or segmental) bronchi split from the secondary bronchi
These supply a portion of the lung called the bronchopulmonary segment
Typically ten segments are in right lung and eight segments are in the left lung

8. Bronchial Tree Branches
Intralobular bronchioles branch from the tertiary bronchi
These enter the basic units of the lung (called lobules)
Terminal bronchioles branch from the intralobular bronchioles
There are fifty to eighty terminal bronchioles in a lobule of the lung
Respiratory bronchioles branch from each terminal bronchiole
These have air sacs that bud from their sides and allow them to participate in gas exchange
There are typically two or more that branch from each terminal bronchiole

10. Bronchial Tree Branches
Alveolar ducts branch from each respiratory bronchial
Alveolar sacs come off of the alveolar ducts
Alveoli (which are thin-walled microscopic air sacs) open to the alveolar sacs

12. Bronchial Tree Structure of respiratory tubes Bronchus
Structured similar to the trachea
C-shaped rings of cartilage are replaced by plates of cartilage that completely surround the bronchus (unlike the c-shaped rings which open posteriorly) when the bronchus enters the lung

13. Bronchial Tree Structure of respiratory tubes Smaller branches
As the branches of the respiratory tree become smaller:
The amount of cartilage decreases and the amount of smooth muscle becomes more prominent
Cartilage disappears completely in the bronchioles
The muscular layer remains prominent until the alveolar ducts which only have a few muscle fibers
The number of goblet cells and the amount of cilia decrease
The type of tissue in the walls also changes

14. Bronchial Tree Structure of respiratory tree
Elastic fibers are scattered throughout the smooth muscle and connective tissue that surround the respiratory tubes

15. Bronchial Tree Functions of the respiratory tubes and alveoli
Branches serve as passageways for air, filter incoming air, and distribute air evenly to alveoli in all parts of the lungs
Alveoli provide a large surface area for gas exchange
During gas exchange:
Oxygen diffuses through the alveolar walls and enters blood in nearby capillaries
Carbon dioxide diffuses from the blood through alveolar walls and enters the alveoli

16. Lungs
Suspended in the thoracic cavity by a bronchus and various large blood vessels
These tubular structures enter each lung on the medial surface through a region called the hilum
Covered by the visceral pleura which fold back to become the parietal pleura at the hilum
The visceral pleura and parietal pleura essentially touch each other and are separated only by a thin film of serous fluid (located in the pleural cavity) that serves as lubrication to reduce friction during breathing and helps to hold the pleural membranes together

18. Lungs Right lung is larger than the left lung
The right lung is divided by fissures into the superior, middle, and inferior lobes
The left lung is divided by fissures into the superior and inferior lobes

19. Lungs
Lobes
Each lobe is supplied by a lobar bronchus, has connections to blood and lymphatic vessels, and is enclosed by connective tissues
Each lobe is further divided by connective tissues into lobules
Each lobule contains terminal bronchioles (along with their respective alveolar ducts, alveolar sacs, alveoli, nerves, blood vessels, and lymphatic vessels)