The Bronchial Tree

Bronchial treeThe trachea branches into the bronchial tree. The first split produces two bronchial tubes called the primary bronchi (sing. bronchus)

The left primary bronchus leads to the left lung while the right primary bronchus leads to the right lung.

Right primary bronchusLeft primary bronchus

Trachea

Bronchial tree

The primary bronchi then branch into secondary bronchi, which lead to each of the lobes of the lungs.The right primary bronchus will branch three times (3 lobes), while the left primary bronchus will branch only twice (2 lobes).

Bronchial tree

The secondary bronchi continue to divide into smaller and smaller tubes called tertiary and quaternary bronchi until they finally reach the smallest tubes called the bronchioles.

T

TT

T

T

Bronchial tree

The primary, secondary, tertiary, and quaternary bronchi are much like the trachea in composition but as they get smaller they lose the cartilage and fibrous tissue until the bronchiole walls are composed of only a thin layer of muscular and elastic tissue.

The Alveoli

Alveoli

The bronchioles end in a cluster of minute air sacs called the alveoli (sing. alveolus). The alveoli have a wall composition similar to that of capillaries with a thickness of about .00004 in.

Alveoli

An extensive network of capillaries surrounds each alveolus.

Pulmonary arteries bring deoxygenated (blue) blood from the heart to the capillary network surrounding each alveolus.

Alveolar Capillary Network

O2 and CO2 diffuse back and forth between the alveoli

and the blood (RBC) in the capillaries thus allowing the RBC to drop off CO2 for exhalation and pick up O2

for aerobic metabolism in the cells of the body.

Alveoli

Pulmonary veins then carry the freshly oxygenated (red) blood away from the capillary network and back to the heart.

The process just described – the movement of oxygen from outside the body to inside – is not the act of breathing, instead it is the process of

respiration.

Respiration is not actually the physical act of breathing, but rather the movement of oxygen from the atmosphere to the cells of the body. Respiration includes:

External respiration – is the passage of O2 and CO2 to and from the alveoli and RBC. Internal respiration – is the passage of O2 and CO2 to and from RBC and body cells . Cellular respiration – is the release of energy from the oxidation of food materials (which means using the oxygen to “burn” food).

The Lungs

Lungs

A pair of lungs contains about 300 million alveoli. This subdivides the volume of the lungs and creates a total alveolar surface area of about 1000 ft.2 (like a room 33 ft. x 30 ft.).The advantage to having this is that it allows for a very large surface area for gas exchange.

Lungs

The lungs are “pink” in color, cone shaped and they extend from the diaphragm to the root of the neck. Each primary bronchus enters its respective lung at the hilus of the lung (a depression on the surface of a bodily organ around the point of entrance or exit of vessels, nerves, or ducts).

hilus

Lungs

At the hilus, the pulmonary arteries & veins, bronchial arteries & veins, nerves and lymphatic vessels enter and leave the lungs. Lymph nodes and aereolar tissue also come together at this point to form the root of the lung. Except for at the root, the lungs are freely movable within the chest cavity.

Root

Lungs

Because the heart appears “tilted”, meaning the heart is larger on the left side, there is more room on the right side of the thoracic cavity so this extra space is taken up by lung tissue. This means the left lung is less massive, and therefore smaller than the right.

Note the color of healthy lungs

Lungs

Thus, the right lung is larger and broader than the left, but it is also shorter than the left lung because the diaphragm rises higher on the right to allow room for the liver.

Liver

Lungs

The right lung is divided into three (3) lobes – the superior or upper, middle, and inferior or lower. The left lung is divided into two (2) lobes – the superior or upper and the inferior or lower.

Lungs

The lungs are “light”, porous, and spongy (they would float in water). Each lobe is supplied by a secondary bronchus and a major branch of the pulmonary artery. Each lobe is broken down into subgroups called sub lobes. Each sub lobe receives a tertiary bronchus.

Note the 3 lobes of the right lung and the 2 lobes of the left lung

Nostril

Nasal cavity

Nose hairsMucous membranesSinus openings***Olfactory bulbsNasal septum

Review & addendum

*** Addendum to follow – additional notes on the sinuses

Blue – respiratory tract structures “passed through” Green – accessory structures “passed by”

The Paranasal Sinuses

- Maxillary- Sphenoidal - Ethmoidal - Frontal

The sinuses are “air spaces” in the bones of the skull which are open to the nasal cavity. Their primary function is to lighten the bones of the skull, but they also contribute mucus to the nasal cavity and act as a resonating chamber for sound production.

Acute sinusitis is very common with more than 24 million cases occurring in the United States annually. Roughly ninety percent of adults have had sinusitis at some point in their life.

Sinusitis

Sinusitis is simply the inflammation of the paranasal sinuses, usually due to infection or allergy. Most cases are due to a viral infection (the “common” cold) and last only about 10 days.

Sinusitis can be classified into three categories:

Acute – lasting less than four weeksSubacute – lasting 4 to 8 weeksChronic – lasting for 8 weeks or more

All three “types” of sinusitis have similar symptoms, and are thus often difficult to distinguish on any basis other than duration.

During a cold or an allergy, the sinuses may become blocked by swelling of the mucous membranes. Drainage into the nasal cavity is stopped, but the formation of the mucus continues, and pressure builds up in the sinuses causing headaches – sometimes severe. The condition can become chronic making it necessary to open the wall of the sinus surgically. This is called “draining the sinuses.”

Sinus Headaches

•Maxillary - can cause pain in the cheek area•Frontal - can cause pain above eyes•Ethmoid - can cause pain mostly between the eyes•Sphenoid - can cause pain or pressure behind the eyes or the top of the head

Review

Secondary Bronchi

Primary Bronchi

Tertiary Bronchi

Quaternary Bronchi

Bronchioles

Alveoli

Nostril

Nasal cavity

Nasopharynx

Oropharynx

LarynxNose hairsMucous membranesSinus openingsOlfactory bulbsNasal septum

Pharyngeal tonsils (adenoids)Eustachian (auditory) tubes

Palatine tonsilsTongueOral cavityUvula

Lingual tonsilsEpiglottis

Vocal cordsTrachea

Laryngopharynx

Cilia

Blue – respiratory tract structures “passed through” Green – accessory structures “passed by”