Bronchus
Conducting passages.
Front view of cartilages of larynx, trachea, and bronchi.
Gray's	subject #237 1084
System	respiratory
Artery	bronchial artery
Vein	bronchial vein
Nerve	pulmonary branches of vagus nerve
MeSH	Bronchi
Dorlands/Elsevier	b_23/12198294

A bronchus (plural bronchi, adjective bronchial) is a caliber of airway in the respiratory tract that conducts air into the lungs. No gas exchange takes place in this part of the lungs. Image File history File links Illu_conducting_passages. ... Image File history File links Gray961. ... In biology, an organ is a group of tissues which perform some function. ... Section of an artery For other uses, see Artery (disambiguation). ... Bronchial Artery The bronchial arteries supply nutrients and oxygen to the root of the lungs, the supporting tissues of the lungs, and the visceral pleura of the lungs. ... In the circulatory system, a vein is a blood vessel that carries blood toward the heart. ... The bronchial veins are small vessels that return blood from the larger bronchi and structures at the roots of the lungs. ... Nerves (yellow) Nerves redirects here. ... The pulmonary branches of the vagus nerve can be divided into two groups: anterior and posterior. ... Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ... Elseviers logo. ... In humans the respiratory tract is the part of the anatomy that has to do with the process of respiration or breathing. ... Gas exchange or respiration takes place at a respiratory surface - a boundary between the external environment and the interior of the body. ...

Anatomy

The trachea (windpipe) divides into two main bronchi (also mainstem bronchi), the left and the right, at the level of the sternal angle. The right main bronchus is wider, shorter, and more vertical than the left main bronchus. The right main bronchus subdivides into three segmental bronchi while the left main bronchus divides into two. The lobar bronchi divide into tertiary bronchi. Each of the segmental bronchi supplies a bronchopulmonary segment. A bronchopulmonary segment is a division of a lung that is separated from the rest of the lung by a connective tissue septum. This property allows a bronchopulmonary segment to be surgically removed without affecting other segments. There are ten segments per lung, but due to anatomic development, several segmental bronchi in the left lung fuse, giving rise to eight. The segmental bronchi divide into many primary bronchioles which divide into terminal bronchioles, each of which then gives rise to several respiratory bronchioles, which go on to divide into 2 to 11 alveolar ducts. There are 5 or 6 alveolar sacs associated with each alveolar duct. The alveolus is the basic anatomical unit of gas exchange in the lung. Windpipe redirects here. ... The sternal angle is the angle formed by the junction of the manubrium and the body of the sternum. ... The Respiratory system is a very important part of the human body. ... The left main bronchus (or left primary bronchus, or left principal bronchus) is smaller in caliber but longer than the right, being nearly 5 cm long. ... The tertiary bronchi (also known as the segmental bronchi) arise from the secondary bronchi. ... Each of the tertiary bronchi serves a specific bronchopulmonary segment. ... Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, muscle, and nervous tissue. ... Look up septum in Wiktionary, the free dictionary. ... The primary bronchioles arise from the tertiary bronchi. ... A terminal bronchiole is a bronchiole at the end of the conducting zone. ... The bronchioles are the first airway branches that no longer contain cartilage. ... Alveolar ducts are the tiny end tubules of the branching airways that fill the lungs. ... Detailed drawing of the alveoli from Grays Anatomy, 1918 - Schematic longitudinal section of a primary lobule of the lung (anatomical unit); r. ... Detailed drawing of the alveoli from Grays Anatomy, 1918 - Schematic longitudinal section of a primary lobule of the lung (anatomical unit); r. ...

There is hyaline cartilage present in the bronchi, present as irregular rings in the larger bronchi (and not as regular as in the trachea), and as small plates and islands in the smaller bronchi. Smooth muscle is present continuously around the bronchi. Cartilage is type of dense connective tissue. ... Smooth muscle Layers of Esophageal Wall: 1. ...

In the mediastinum, at the level of the fifth thoracic vertebra, the trachea divides into the right and left primary bronchi. The bronchi branch into smaller and smaller passageways until they terminate in tiny air sacs called alveoli. FIG. 967– Transverse section through the upper margin of the second thoracic vertebra The mediastinum is a non-delineated group of structures in the thorax (chest), surrounded by loose connective tissue. ... A typical thoracic vertebra The thoracic vertebrae (vertebrae thoracales) compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. ...

The cartilage and mucous membrane of the primary bronchi are similar to that in the trachea. As the branching continues through the bronchial tree, the amount of hyaline cartilage in the walls decreases until it is absent in the smallest bronchioles. As the cartilage decreases, the amount of smooth muscle increases. The mucous membrane also undergoes a transition from ciliated pseudostratified columnar epithelium to simple cuboidal epithelium to simple squamous epithelium. Cartilage is a type of dense connective tissue. ... The mucous membranes (or mucosae; singular: mucosa) are linings of mostly endodermal origin, covered in epithelium, and are involved in absorption and secretion. ... Cartilage is type of dense connective tissue. ... Cuboidal epithelia are cube-shaped epithelial cells present in single layers (Simple cuboidal epithelium) or multiple layers (Stratified cuboidal epithelium), depending on their location in the body. ... A comparison of squamous epithelia to other epithelial types In anatomy, squamous epithelium is an epithelium characterised by its most superficial layer consisting of flat, scalelike cells called squamous cells. ...

The alveolar ducts and alveoli consist primarily of simple squamous epithelium, which permits rapid diffusion of oxygen and carbon dioxide. Exchange of gases between the air in the lungs and the blood in the capillaries occurs across the walls of the alveolar ducts and alveoli. A comparison of squamous epithelia to other epithelial types In anatomy, squamous epithelium is an epithelium characterised by its most superficial layer consisting of flat, scalelike cells called squamous cells. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) pale blue (liquid) Standard atomic weight 15. ... Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. ... The word capillary is used to describe any very narrow tube or channel through which a fluid can pass. ...

Role in disease

Bronchitis is defined as inflammation of the bronchi. There are two main types: acute and chronic. Acute bronchitis is usually caused by viral or bacterial infections. Chronic bronchitis is a form of COPD, usually associated with smoking or long-term exposure to irritants. Asthma is hyperreactivity of the bronchi with an inflammatory component, often in response to allergens. Bronchitis is an inflammation of the bronchi (medium-size airways) in the lungs. ... Bronchitis is an inflammation of the bronchi of the lungs, that causes the cilia of the bronchial epithelial cells to stop functioning. ... Chronic obstructive pulmonary disease (COPD), also known as chronic obstructive airway disease (COAD), is a group of diseases characterized by limitation of airflow in the airway that is not fully reversible. ... An allergen is any substance (antigen), most often eaten or inhaled, that is recognized by the immune system and causes an allergic reaction. ...

While the left mainstem bronchus departs from the trachea at an angle, the right mainstem bronchus is almost a vertical continuation of the trachea. This anatomy predisposes the right lung to several problems:

• If food, liquids, or foreign bodies are aspirated, they often will lodge in the right mainstem bronchus. Aspiration pneumonia may result.
• If the endotracheal tube used for intubation is inserted too far, it usually lodges in the right mainstem bronchus. This allows ventilation of the right lung, but leaves the left lung useless.
• Patients with inadequate cough reflexes may develop chronic right middle lobe lung infections such as the Lady Windermere Syndrome.

Aspiration pneumonia is a specific form of lung infection (pneumonia) that develops when oral or gastric contents (including food, saliva, or nasal secretions) enter the bronchial tree. ... Diagram of an endotracheal tube (10) that has been inserted into the airway of a patient. ... This article or section needs copy editing for grammar, style, cohesion, tone and/or spelling. ... This article is in need of attention. ...

Additional images

cross sectional cut of a human secondary bronchus

Transverse section of thorax, showing relations of pulmonary artery. Image File history File linksMetadata Download high-resolution version (2816x2112, 2431 KB) Authors own picture. ... Image File history File linksMetadata Download high-resolution version (2816x2112, 2431 KB) Authors own picture. ... Image File history File links Gray503. ...

References

• Moore, Keith L. and Arthur F. Dalley. Clinically Oriented Anatomy, 4th ed. (1999). ISBN 0-7817-5936-6