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Information about Bronchi

Conducting passages.
Front view of cartilages of larynx, trachea, and bronchi.
subject #237 1084
Systemrespiratory
Arterybronchial artery
Veinbronchial vein
Nervepulmonary 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.

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.

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.

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.

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.

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.

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.

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.

Additional images

Enlarge picture
cross sectional cut of a human secondary bronchus



Transverse section of thorax, showing relations of pulmonary artery.


References

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


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Anatomy of torso, respiratory system: Lungs and related structures
lungs
conducting zone
respiratory zone
pleurae
organ (Latin: organum, "instrument, tool") is a group of tissues that perform a specific function or group of functions. Usually there is a main tissue and sporadic tissues. The main tissue is the one that is unique for the specific organ.
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Arteries are muscular blood vessels that carry blood away from the heart.[1] All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood.

The circulatory system is extremely important for sustaining life.
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In human anatomy, the bronchial arteries help supply the lungs with oxygenated blood. Although there is much variation, there are usually two bronchial arteries that run to the left lung, and one to the right lung.
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vein is a blood vessel that carries blood toward the heart. The majority of veins in the body carry low-oxygen blood from the tissues back to the heart; the exceptions being the pulmonary and umbilical veins which both carry oxygenated blood.
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The bronchial veins are small vessels that return blood from the larger bronchi and structures at the roots of the lungs. The right side drains into the azygos vein, while the left side drains into the left superior intercostal vein or the accessory hemiazygos vein.
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A nerve is an enclosed, cable-like bundle of axons (the long, slender projection of a neuron). Neurons are sometimes called nerve cells, though this term is technically imprecise since many neurons do not form nerves, and nerves also include the glial cells that
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The pulmonary branches of the vagus nerve can be divided into two groups: anterior and posterior.

Anterior

The Anterior Bronchial Branches (rami bronchiales anteriores; anterior or ventral pulmonary branches), two or three in number, and of small size, are
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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. Created and updated by the United States National Library of Medicine (NLM), it is used by the MEDLINE/PubMed
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Elsevier, the world's largest publisher of medical and scientific literature, forms part of the Reed Elsevier group. Based in Amsterdam, the company has substantial operations in the UK, USA and elsewhere.
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In humans the respiratory tract is the part of the anatomy that has to do with the process of respiration.

The respiratory tract is divided into 3 segments:
  • Upper respiratory tract: nose and nasal passages, paranasal sinuses, and throat or pharynx

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Gas exchange or respiration takes place at a respiratory surface - a boundary between the external environment and the interior of the body. For unicellular organisms the respiratory surface is simply the cell membrane, but for large organisms it usually is carried out in
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trachea, or windpipe, is a tube that has an inner diameter of about 20-25 mm and a length of about 10-16cm. It extends from the larynx to the primary (main) bronchi in mammals, and from the pharynx to the syrinx in birds, allowing the passage of air to the lungs.
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The sternal angle is the angle formed by the junction of the manubrium and the body of the sternum in the form of a secondary cartilaginous joint (symphysis). This is also called the manubriosternal joint or Angle of Louis. The sternal angle is a palpable clinical landmark.
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The right main bronchus (or right primary bronchus, or right principal bronchus), wider, shorter, and more vertical in direction than the left, is about 2.5 cm. long, and enters the right lung nearly opposite the fifth thoracic vertebra.
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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. It enters the root of the left lung opposite the sixth thoracic vertebra.
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The tertiary bronchi (also known as the segmental bronchi) arise from the secondary bronchi. The respiratory epithelium lining their lumen is surrounded by a layer of smooth muscle. This layer is composed of two ribbons of smooth muscle that spiral in opposite directions.
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Each of the tertiary bronchi serves a specific bronchopulmonary segment. These segments each have their own artery. Thus, each bronchopulmonary segment is supplied by a bronchus, and an artery.
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Connective tissue is one of the four types of tissue in traditional classifications (the others being epithelial, muscle, and nervous tissue.) It is largely a category of exclusion rather than one with a precise definition, but all or most tissues in this category are similarly:
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septum (Latin: something that encloses; plural Septa) is a partition separating two cavities or spaces. Examples include:
  • Nasal septum: the cartilage wall separating the nostrils of the human nose.

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The primary bronchioles arise from the tertiary bronchi. They are histologically distinct from the tertiary bronchi in that their walls do not have hyaline cartilage and they have Clara cells in their epithelial lining.
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A terminal bronchiole is a bronchiole at the end of the conducting zone. At the transition into the respiratory zone, alveoli become present.

External links

  • Terminal+bronchiole at eMedicine Dictionary
  • Diagram at davidson.edu
  • Histology at umdnj.

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A respiratory bronchiole is a bronchiole at the beginning of the respiratory zone. It has cuboidal epithelia.

Additional images




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Alveolar ducts are the tiny end tubules of the branching airways that fill the lungs. Each lung holds approximately 1.5 to 2 million of them. The tubules divide into alveolar sacs at the distal end.
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alveolus (plural: alveoli, from Latin alveus, "little cavity"), is an anatomical structure that has the form of a hollow cavity. Mainly found in the lung, the pulmonary alveoli
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Hyaline cartilage consists of a slimy mass of a firm consistency, but of considerable elasticity and pearly bluish color. It contains no nerves or blood vessels, and its structure is relatively simple.
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Smooth muscle is a type of non-striated muscle, found within the "walls" of hollow organs and elsewhere like the bladder and abdominal cavity, the uterus, male and female reproductive tracts, the gastrointestinal tract, the respiratory tract, the vasculature, the skin and the
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The mediastinum is a non-delineated group of structures in the thorax (chest), surrounded by loose connective tissue. It is the central compartment of the thoracic cavity.
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The thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. They are intermediate in size between those of the cervical and lumbar regions; they increase in size as one proceeds down the spine, the upper
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Cartilage is a type of dense connective tissue. It is composed of collagen fibers and/or elastin fibers, and can supply smooth surfaces for the movement of articulating bones.
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The mucous membranes (or mucosae; singular: mucosa) are linings of mostly endodermal origin, covered in epithelium, and are involved in absorption and secretion. They line various body cavities that are exposed to the external environment and internal organs.
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