The spermatic cord is actually a bundle of fibers and tissues that form a cord-like structure that runs through the abdominal region down to the…. In male anatomy, the corpus spongiosum of penis is a mass of erectile tissue that lies along the underside of the penis and is located below the pair…. The coccygeal muscle is located in the pelvic cavity.
This muscle originates at the sacrospinous ligament, near the center of the pelvis, and inserts…. The jejunum is one of three sections that make up the small intestine.
Learn about its function and anatomy, as well as the conditions that can affect…. The vagus nerve is the longest of the 12 cranial nerves. Here, learn about its anatomy, functions, and the kinds of health problems that can occur. Health Conditions Discover Plan Connect. Read this next. Leg Anatomy. Medically reviewed by William Morrison, M.
Spermatic cord Medically reviewed by the Healthline Medical Network. Corpus spongiosum penis Medically reviewed by the Healthline Medical Network. Coccygeal muscle Medically reviewed by the Healthline Medical Network. 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. The two lungs, which contain all the components of the bronchial tree beyond the primary bronchi, occupy most of the space in the thoracic cavity. The lungs are soft and spongy because they are mostly air spaces surrounded by the alveolar cells and elastic connective tissue.
The bronchus branches into smaller tubes called bronchioles. The bronchi and bronchioles are considered anatomical dead space, like the trachea and upper respiratory tract, because no gas exchange takes place within this zone. The human trachea divides into two main bronchi also called mainstem bronchi , that extend laterally but not symmetrically into the left and right lung respectively, at the level of the sternum. The point where the trachea divides into the bronchi is called the carina.
The right main bronchus is wider, shorter than the left main bronchus, which is thinner and longer. The right main bronchus subdivides into three lobar bronchi, while the left main bronchus divides into two. The lobar bronchi also called secondary bronchi divide into tertiary bronchi, each of which supplies air to a different bronchopulmonary segment.
A bronchopulmonary segment is a distinct region of the lung separated from the rest of the lung by connective tissue. Each bronchopulmonary segment forms a discrete functional unit in the lung that is independent of the other segments. This property allows a bronchopulmonary segment to be surgically removed without affecting other segments. There are 10 segments in the right lung and 8 to 9 segments in the left lung due to anatomical differences. The segmental bronchi divide into many primary bronchioles that divide into terminal bronchioles.
Each terminal bronchiole then gives rise to several respiratory bronchioles, which go on to divide into two to 11 alveolar ducts.
There are five or six alveolar sacs associated with each alveolar duct. The alveolus is the smallest anatomical unit of the lung, and the site of gas exchange between the lung and the bloodstream.
The histology of the bronchi are largely similar to that of the trachea. There is hyaline transparent and consisting of collagen cartilage present in the bronchi, in rings that are more irregular than those in the trachea. There are also small plates and islands of hyaline cartilage in the primary and terminal bronchioles.
Smooth muscle is present continuously around the bronchi similar to the trachealis muscle of the trachea and is innervated with the parasympathetic nervous system.
The amount of bronchial smooth muscle increases as the amount of hyaline cartilage decreases as the bronchi become smaller further into the lungs. The mucous membrane lining the bronchi also undergoes a transition—from ciliated pseudostratified columnar epithelium to simple cuboidal epithelium to simple squamous epithelium further into the lungs. Like the trachea, the bronchi and bronchioles are part of the conducting zone, so they moisten and warm air and contribute to the volume of anatomical dead space.
The bronchi and bronchioles are also part of the mucociliary escalator that removes mucus and pathogens from the lungs. A unique characteristic of the bronchi and bronchioles is bronchoconstriction, in which the smooth muscle of the bronchi or bronchioles tightens.
This leads to coughing, wheezing, and dyspnea shortness of breath. It is caused by activation of the parasympathetic nervous system and release of acetylcholine in the bronchi, as well as by overproduction of mucus or allergic reactions and inflammation. It is a symptom of diseases such as bronchitis chronic inflammation and mucus production in the bronchi and asthma an acute attack of bronchoconstriction, often allergic. Both cause obstruction of the airways and make it more difficult to breathe.
Bronchoconstriction is treated with anti-inflammatory drugs, such as corticosteroids, and prevented by maintaining lung health, such as through avoiding smoking, air pollution, and airborne allergens.
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