Pulmonary alveolus in the context of "Respiratory"

Ascariasis is a disease caused by the parasitic roundworm Ascaris lumbricoides. Infections have no symptoms in more than 85% of cases, especially if the number of worms is small. Symptoms increase with the number of worms present and may include shortness of breath and fever at the beginning of the disease. These may be followed by symptoms of abdominal swelling, abdominal pain, and diarrhea. Children are most commonly affected, and in this age group the infection may also cause poor weight gain, malnutrition, and learning problems.

Infection occurs by ingesting food or drink contaminated with Ascaris eggs from feces. The eggs hatch in the intestines, the larvae burrow through the gut wall, and migrate to the lungs via the blood. There they break into the alveoli and pass up the trachea, where they are coughed up and may be swallowed. The larvae then pass through the stomach a second time into the intestine, where they become adult worms. It is a type of soil-transmitted helminthiasis and part of a group of diseases called helminthiases.

The lungs are the primary organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the backbone on either side of the heart. Their function in the respiratory system is to extract oxygen from the atmosphere and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange. Respiration is driven by different muscular systems in different species. Mammals, reptiles and birds use their musculoskeletal systems to support and foster breathing. In early tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping, a mechanism still seen in amphibians. In humans, the primary muscle that drives breathing is the diaphragm. The lungs also provide airflow that makes vocalisation including speech possible.

Humans have two lungs, a right lung and a left lung. They are situated within the thoracic cavity of the chest. The right lung is bigger than the left, and the left lung shares space in the chest with the heart. The lungs together weigh approximately 1.3 kilograms (2.9 lb), and the right is heavier. The lungs are part of the lower respiratory tract that begins at the trachea and branches into the bronchi and bronchioles, which receive air breathed in via the conducting zone. These divide until air reaches microscopic alveoli, where gas exchange takes place. Together, the lungs contain approximately 2,400 kilometers (1,500 mi) of airways and 300 to 500 million alveoli. Each lung is enclosed within a pleural sac of two pleurae which allows the inner and outer walls to slide over each other whilst breathing takes place, without much friction. The inner visceral pleura divides each lung as fissures into sections called lobes. The right lung has three lobes and the left has two. The lobes are further divided into bronchopulmonary segments and lobules. The lungs have a unique blood supply, receiving deoxygenated blood sent from the heart to receive oxygen (the pulmonary circulation) and a separate supply of oxygenated blood (the bronchial circulation).

Breathing (respiration or ventilation) is the rhythmic process of moving air into (inhalation) and out of (exhalation) the lungs to enable gas exchange with the internal environment, primarily to remove carbon dioxide and take in oxygen.

All aerobic organisms require oxygen for cellular respiration, which extracts energy from food and produces carbon dioxide as a waste product. External respiration (breathing) brings air to the alveoli where gases move by diffusion; the circulatory system then transports oxygen and carbon dioxide between the lungs and the tissues.

The respiratory tract is the subdivision of the respiratory system involved with the process of conducting air to the alveoli for the purposes of gas exchange in mammals. The respiratory tract is lined with respiratory epithelium as respiratory mucosa.

Air is breathed in through the nose to the nasal cavity, where a layer of nasal mucosa acts as a filter and traps pollutants and other harmful substances found in the air. The turbinates increase the nasal cavity, helping it warm, humidify, and filter the incoming air (Sobiesk & Munakomi, 2023). Next, air moves into the pharynx, a passage that contains the intersection between the esophagus and the larynx. The opening of the larynx has a special flap of cartilage, the epiglottis, that opens to allow air to pass through but closes to prevent food from moving into the airway.

The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants.

In land animals, the respiratory surface is internalized as linings of the lungs. Gas exchange in the lungs occurs in millions of small air sacs. In mammals and reptiles, these are called alveoli, and in birds, they are known as atria. These microscopic air sacs have a rich blood supply, bringing the air into close contact with the blood. A system of airways, or hollow tubes, allow the air sacs to interface with the external environment; the largest of these is the trachea, which branches in the middle of the chest into the two main bronchi, which enter the lungs and branch into progressively narrower secondary and tertiary bronchi, which in turn branch into numerous smaller tubes known as the bronchioles in mammals and reptiles. In birds, the bronchioles are termed parabronchi. The bronchioles, or parabronchi, generally open into the microscopic alveoli (in mammals) and atria (in birds). Air has to be pumped from the environment into the alveoli or atria by the process of breathing which involves the muscles of respiration.

Gas exchange is the physiological process by which gases move passively by diffusion across a surface. For example, this surface might be the air/water interface of a water body, the surface of a gas bubble in a liquid, a gas-permeable membrane, or a biological membrane that forms the boundary between an organism and its extracellular environment.

Gases are constantly consumed and produced by cellular and metabolic reactions in most living things, so an efficient system for gas exchange between, ultimately, the interior of the cell(s) and the external environment is required. Small, particularly unicellular organisms, such as bacteria and protozoa, have a high surface-area to volume ratio. In these creatures the gas exchange membrane is typically the cell membrane. Some small multicellular organisms, such as flatworms, are also able to perform sufficient gas exchange across the skin or cuticle that surrounds their bodies. However, in most larger organisms, which have small surface-area to volume ratios, specialised structures with convoluted surfaces such as gills, pulmonary alveoli and spongy mesophylls provide the large area needed for effective gas exchange. These convoluted surfaces may sometimes be internalised into the body of the organism. This is the case with the alveoli, which form the inner surface of the mammalian lung, the spongy mesophyll, which is found inside the leaves of some kinds of plant, or the gills of those molluscs that have them, which are found in the mantle cavity.

Tobacco smoking is the practice of burning tobacco and ingesting the resulting smoke. The smoke may be inhaled, as is done with cigarettes, or released from the mouth, as is done with pipes and cigars. The practice is believed to have begun as early as 5000–3000 BC in Mesoamerica and South America. Tobacco was introduced to Eurasia in the late 17th century by European colonists, where it followed common trade routes. The practice encountered criticism from its first import into the Western world onward but embedded itself in certain strata of several societies before becoming widespread upon the introduction of automated cigarette-rolling apparatus.

Smoking is the most common method of consuming tobacco, and tobacco is the most common substance smoked. The agricultural product is often mixed with additives and then combusted. The resulting smoke, which contains various active substances, the most significant of which is the addictive psychostimulant drug nicotine (a compound naturally found in tobacco), is absorbed through the alveoli in the lungs or the oral mucosa. Many substances in cigarette smoke, chiefly nicotine, trigger chemical reactions in nerve endings, which heighten heart rate, alertness and reaction time, among other things. Dopamine and endorphins are released, which are often associated with pleasure, leading to addiction.