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Organs Lung Lobes Alveoli

R Superior Lobe

The right upper lobe of the lung is located in the right superior corner of the thoracic cavity lateral to the trachea and esophagus. It is superior to the horizontal and oblique fissures, which separates the upper lobe from the middle and lower lobes of the right lung. The right upper lobe begins at the apex, the slightly pointed superior-most tip of the right lung. From the apex, the upper lobe widens and extends laterally, where its convex curvature follows the interior of the ribcage. On its medial end, the right upper lobe is concave and has several prominent notches that accommodate the trachea, esophagus, and major blood vessels of the mediastinum. Protruding just inferior to the right upper lobe is the root of the right lung, which contains the primary bronchus, blood vessels, and nerves entering the lung. Air enters the root of the right lung through the right primary bronchus, which divides into three secondary bronchi. Of these three secondary bronchi, the right superior lobar bronchus extends superiorly to provide air to the right upper lobe. Inside the right upper lobe, the right superior lobar bronchus divides into three tertiary bronchi, which provide air to the three bronchopulmonary segments: apical, anterior, and posterior. The apical segment includes the tissue of the apex and extends medially to the root of the lung. The anterior and posterior segments constitute the anterior and posterior regions, respectively, of the inferior regions of the upper lobe.     Source


R Inferior Lobe

The inferior lobe is a section of the human lung. Each lung is divided into lobes, the right lung consists of the superior, middle, and inferior lobes, while the left lung consists of only the superior and inferior lobes. Note that both lungs contain an inferior lobe, and it is roughly a similar size to the superior lobe within each lung. An oblique fissure divides the superior and inferior lobes of the lung, in the right lung a horizontal fissure also separates the middle lobe. The oblique fissure is commonly found to follow the line of the sixth rib, however, variability has been noted. It is possible, though not common, to separate the inferior lobe from the rest of the lung and transplant it into another patient whose lungs do not or cannot function. This is a proposed alternative to entire-lung transplants from cadavers. It is a particularly strong alternative as a donor need not be deceased to donate the inferior lobe. This is known as lobar lung transplantation. Two donors donate one inferior lobe to the patient to replace the patient’s lungs. However, this is not yet a common procedure.     Source


R Middle Lobe

The lung consists of five lobes. The left lung has a superior and inferior lobe, while the right lung has superior, middle, and inferior lobes. Thin walls of tissue called fissures separate the different lobes. only the right lung has a middle lobe. As the name implies, this lobe is located between the upper and lower (also called the superior and inferior) lobes. Each lobe receives air from its own branch of the bronchial tree, called lobar (or secondary) bronchi. Within the lungs, these bronchi are divided into smaller tubes. The smallest of these tubes is called a bronchiole. Bronchioles control the exchange of gases with the alveoli, which are tiny air sacs in the lungs. Each lobe of the lung has the same physiologic function, bringing oxygen into the bloodstream and removing carbon dioxide. Sections of a lobe, or even entire lobes can be removed as a treatment for conditions such as lung cancer, tuberculosis, and emphysema.      Source


L Superior Lobe

The left upper lobe (LUL) is one of two lobes in the left lung. It is separated from the left lower lobe by the left oblique fissure and subdivided into four bronchopulmonary segments, two of which represent the lingula. Like all the pulmonary lobes, it is lined by visceral pleura which reflects at the pulmonary hilum where it is continuous with the parietal pleura. The left upper lobe bronchus arises from the superolateral wall of the left main bronchus to traverse the left hilum into the LUL.      Source


L Inferior Lobe

The inferior lobe is a section of the human lung. Each lung is divided into lobes, the right lung consists of the superior, middle, and inferior lobes, while the left lung consists of only the superior and inferior lobes. Note that both lungs contain an inferior lobe, and it is roughly a similar size to the superior lobe within each lung. An oblique fissure divides the superior and inferior lobes of the lung, in the right lung a horizontal fissure also separates the middle lobe. The oblique fissure is commonly found to follow the line of the sixth rib, however, variability has been noted. It is possible, though not common, to separate the inferior lobe from the rest of the lung and transplant it into another patient whose lungs do not or cannot function. This is a proposed alternative to entire-lung transplants from cadavers. It is a particularly strong alternative as a donor need not be deceased to donate the inferior lobe. This is known as lobar lung transplantation. Two donors donate one inferior lobe to the patient to replace the patient’s lungs. However, this is not yet a common procedure.      Source


Smooth Muscle

Smooth muscle is an involuntary non-striated muscle. It is divided into two subgroups



The smallest airways within the lungs that are not encircled by any cartilage are called bronchioles. Once the trachea divides into the left and right primary bronchi, they then branch into smaller and smaller divisions to lead to bronchioles. The trachea, bronchi, bronchioles, and alveoli all make up the lower respiratory tract. Each lung has around 30,000 bronchioles. Located within the lungs, bronchioles are tubular structures around 1mm in diameter, consisting of connective tissues and some smooth muscles that keep the tubes open. These further divide into smaller tubules, which in turn continue subdividing till they reach the alveoli.       Source



Cartilage rings in the walls of the windpipe help to keep it open however much you twist your neck.      Source



The blood capillaries are where the important functions of the circulation take place: the exchange of material between circulation and cells. Capillaries are the smallest of the body’s blood vessels. They are only one cell thick, and they are the sites of the transfer of oxygen and other nutrients from the bloodstream to other tissues in the body, they also collect carbon dioxide waste materials and fluids for return to the veins. They connect the tiny muscular branches of arteries, called arterioles, with tiny veins (called venules). Ultimately, the capillary is the site of internal or cellular respiration and is responsible for the utilization of oxygen by the tissue and the transporting of carbon dioxide as waste to the veins for elimination by the lungs. The arterial blood system branches extensively to deliver blood to over a billion capillaries in the body. The extensiveness of these branches is much more readily appreciated by knowing that the capillaries provide a total surface area of 1,000 square miles for exchanges of gases, waste, and nutrients between blood and tissue fluid. Oxygen rich blood flows from arterioles or small branches of the artery into the capillary bed and the pressure inside of the arteries is roughly fifty times that on the inside of the veins. It is this pressure difference that forces the blood into the capillary bed. Although the amount of blood flowing through a particular capillary bed is determined in part by a small circular muscle around the arteriole branches, the absence of smooth muscle and connective tissue layers permits a more rapid rate of transport between the blood and the tissue.      Source


Alveolar Sac

This is a hollow cavity found in the lung parenchyma and is the basic unit of ventilation. Lung alveoli are the ends of the respiratory tree, branching from either alveolar sacs or alveolar ducts, which like alveoli are both sites of gas exchange with the blood as well. Alveoli are particular to mammalian lungs. Different structures are involved in gas exchange in other vertebrates. The alveolar membrane is the gas exchange surface. Carbon dioxide rich blood is pumped from the rest of the body into the capillaries that surround the alveoli where, through diffusion, carbon dioxide is released and oxygen absorbed. 


Branch of Pulmonary Vein

Your circulatory system is composed of your heart, which is a 4-chambered pump, and a collection of hollow vessels that carry blood away from your heart, deliver it to all of your tissues and organs, and return it to your heart. Your lungs are an important way station within your circulatory system. This is where your blood becomes oxygenated. your circulatory system forms a closed loop: your heart pumps blood through your arteries, arterioles, capillaries, venules, and veins, only to have that blood return to its original location. The 4-chambered design of your heart is critical for keeping your blood moving in the proper direction. Oxygenated blood returning from your lungs enters the left atrium of your heart, where it is channeled through a one-way valve into the heavily-muscled left ventricle. When your heart beats, the contracting left ventricle pushes blood through another valve into your aorta, which is the largest artery in your body. With each heartbeat, blood moves farther along on a journey that will eventually bring it back to your heart. Upon returning to your heart, deoxygenated blood enters the right atrium, which then directs it through yet another valve into the right ventricle. The right ventricle, which is not as muscular as the left ventricle because it only has to pump your blood a short distance, pushes the deoxygenated blood through one more valve into your pulmonary arteries, which carry it to your lungs. Although the blood vessels that transport blood to and from your lungs are continuous with the remainder of your circulatory system, your heart, pulmonary arteries, lungs, and pulmonary veins are called the ‘pulmonary circuit’ to distinguish them from the ‘systemic circuit,’ which serves the rest of your body. Just like the other veins in your body, your pulmonary veins arise from a network of capillaries. However, the capillaries that give rise to the pulmonary veins differ from capillaries elsewhere in your body. The pulmonary capillaries surround and embrace millions of tiny air sacs, called alveoli, in your lungs. This is where your blood takes up oxygen from the air you inhale. As they leave the alveoli and course toward your heart, your pulmonary capillaries unite to form progressively larger venules and veins, which gather in the crevices that divide the various divisions, or segments, of your lungs. Eventually, all of the veins within one lung segment unite to form a single vein called a segmental vein.       Source


Ciliated Columnar Cell 

Ciliated epithelium tissue prompts your sneeze and also helps keep you healthy in other important ways. Cilia are hair-like structures that sit on top of a tissue. They wave back and forth to help move things. Epithelium is a tissue type. This is typically a very thin tissue that covers structures. The best example of epithelial tissue is the human skin. When you breathe in something like dust – a particle that shouldn’t be in your lungs – the cilia that line your respiratory tract catch these particles and move them out, triggering a sneeze. We Have ciliated epithelium in the lining of our respiratory tract, aka the tubes that lead into your lungs.      Source


Goblet Cell

Goblet cells and their main secretory product, mucus. Goblet cells are specialized for the synthesis and secretion of mucus. Below the larynx lies the trachea, a tube about 10 to 12 cm (3.9 to 4.7 inches) long and 2 cm (0.8 inch) wide. Its wall is stiffened by 16 to 20 characteristic horseshoe-shaped, incomplete cartilage rings that open toward the back and are embedded in a dense connective tissue. The dorsal wall contains a strong layer of transverse smooth muscle fibres that spans the gap of the cartilage. The interior of the trachea is lined by the typical respiratory epithelium. The mucosal layer contains mucous glands. Ciliated cells are present far down in the airway tree, their height decreasing with the narrowing of the tubes, as does the frequency of goblet cells. In bronchioles the goblet cells are completely replaced by another type of secretory cells named Clara cells.      Source


Basement Membrane

Your skin has three layers. The outer layer, called the epidermis, is composed of epithelial cells. This is the part of the skin that’s visible to the eye and probably peels off in sheets if you’ve had too much fun in the sun. The middle layer is the dermis and is composed of connective tissue. This is where you find all the good stuff: blood vessels, sweat glands, sebaceous glands, and temperature sensors. The third and lowest layer is the subcutaneous fat layer. The basement membrane lies between the epidermis and the dermis, keeping the outside layer tightly connected to the inside layer. Not even the effects of gravity can destroy this anchoring system. So, while skin might droop and sag, it won’t ever completely fall off. Basement membranes aren’t just found in the skin, though. They have important functions all over the body. Any place you find epithelium cells, which cover the inner and outer portions of glands, organs, and structural tissue, and endothelium tissue, which coats the inside of blood vessels, a basement membrane will be in between to hold the layers together. The basement membrane acts as a mechanical barrier, preventing malignant cells from invading the deeper tissues. Early stages of malignancy that are thus limited to the epithelial layer by the basement membrane are called carcinoma in situ. The basement membrane is also essential for angiogenesis (development of new blood vessels). Basement membrane proteins have been found to accelerate differentiation of endothelial cells. Basement membrane (or basal lamina) fulfills several functions, and is sometimes modified for specialized functions. First, it binds cells to the matrix as already described. During development it guides migrating primordial cells to their destinations. It is of prime importance during early development. Early basement membranes are primarily laminin, and non-functional laminin prevents development. Basal lamina also is a barrier to cell penetrating migration, preventing contact between fibroblasts and epithelia, and it is not breached by epithelia except in cases of malignancy. It is permeable, however, to macrophages, lymphocytes, and nerve processes. Basement membrane is also important to tissue regeneration after injury. The surviving basal lamina provide a guide for the migration of regenerating cells. In some cases it is modified after injury, promoting cell migration for wound healing.      Source  



Pulmonary interstitium is a collection of support tissues within the lung that includes the alveolar epithelium, pulmonary capillary endothelium, basement membrane, perivascular and perilymphatic tissues. The pulmonary interstitium can be divided into three zones – axial, parenchymal and peripheral.      Source


Type I Pneumocytes

Can be identified as thin, squamous (flattened) cells whose most obvious feature is their nuclei. Type I pneumocytes are involved in the process of gas exchange between the alveoli and the capillaries. They are squamous (flattened) in shape and extremely thin alveolar cells that are adapted to carry out gas exchange (~ 0.15µm) – minimizing diffusion distance for respiratory gases. Type I pneumocytes are connected by occluding junctions, which prevents the leakage of tissue fluid into the alveolar air space. Type I pneumocytes are amitotic and unable to replicate, however type II cells can differentiate into type I cells if required.       Source 


Branch of Pulmonary Artery

The pulmonary arteries originate from the truncus arteriosus (as does the aorta), and in the developed heart, the pulmonary trunk (pulmonary artery or main pulmonary artery) begins at the base of the right ventricle. The pulmonary trunk is a short and stout (wide) structure that is about 5 cm in length and 3 cm in diameter, which branches into 2 pulmonary arteries; the left and right pulmonary arteries, which act to deliver deoxygenated blood to its respective lung. On the other hand, pulmonary veins are large blood vessels that receive oxygenated blood from the lungs to delivery to the rest of the body. There are 4 total pulmonary veins—with 2 pulmonary veins coming from each lung, left and right—that empty into the left atrium of the heart. Two pulmonary veins emerge from the hilus of each lung, and each pulmonary vein receives blood from 3-4 bronchial veins apiece before draining into the left atrium. The pulmonary veins are fixed to the pericardium travel alongside the pulmonary arteries. The right superior pulmonary vein passes in front of and a tad below the pulmonary artery at the root of the lung, and the inferior pulmonary vein is situated at the lowest part of the lung hilum. In reference to the heart, the right pulmonary veins pass behind the right atrium and superior vena cava return, and the left pulmonary veins pass in front of the descending thoracic aorta. Finally, the bronchus is located behind the pulmonary artery. While veins usually carry deoxygenated blood from tissues back to the heart, in this case, pulmonary veins are among the few veins that carry oxygenated blood instead. Oxygenated blood from the lungs is circulated back to the heart through the pulmonary veins that drain into the left atrium. Once blood is pumped from the left atrium through the mitral valve into the left ventricle, this oxygenated blood will then be pumped from the left ventricle through the aortic valve to the rest of the body’s organs and tissues through the aorta.      Source


Basal Cell

The basal layer is the innermost layer of the epidermis, and contains small round cells called basal cells. The basal cells continually divide, and new cells constantly push older ones up toward the surface of the skin, where they are eventually shed. The basal cell layer is also known as the stratum germinativum due to the fact that it is constantly germinating (producing) new cells. The basal cell layer contains cells called melanocytes. Melanocytes produce the skin coloring or pigment known as melanin, which gives skin its tan or brown color and helps protect the deeper layers of the skin from the harmful effects of the sun. Sun exposure causes melanocytes to increase production of melanin in order to protect the skin from damaging ultraviolet rays, producing a suntan. Patches of melanin in the skin cause birthmarks, freckles and age spots. Melanoma develops when melanocytes undergo malignant transformation.      Source


Mucin Secretion

Mucins’ key characteristic is their ability to form gels; therefore they are a key component in most gel-like secretions, serving functions from lubrication to cell signaling to forming chemical barriers. They often take an inhibitory role. Some mucins are associated with controlling mineralization, including nacre formation in mollusks, calcification in echinoderms and bone formation in vertebrates. They bind to pathogens as part of the immune system. Although some mucins are membrane-bound due to the presence of a hydrophobic membrane-spanning domain that favors retention in the plasma membrane, most mucins are secreted as principal components of mucus by mucous membranes or are secreted to become a component of saliva.


Type 2 Pneumocyte

Type II pneumocytes are responsible for the secretion of pulmonary surfactant, which reduces surface tension in the alveoli. They are cuboidal in shape and possess many granules (for storing surfactant components). Type II pneumocytes only comprise a fraction of the alveolar surface (~5%) but are relatively numerous (~60% of total cells). Type II pneumocytes secrete a solution containing surfactant that creates a moist surface inside the alveoli to prevent the sides of the alveolus adhering to each other by reducing surface tension. Alveoli are lined by a layer of liquid in order to create a moist surface conducive to gas exchange with the capillaries. It is easier for oxygen to diffuse across the alveolar and capillary membranes when dissolved in liquid. While this moist lining assists with gas exchange, it also creates a tendency for the alveoli to collapse and resist inflation. Surface tension is the elastic force created by a fluid surface that minimises the surface area (via cohesion of liquid molecules). Type II pneumocytes secrete a liquid known as pulmonary surfactant which reduces the surface tension in alveoli. As an alveoli expands with gas intake, the surfactant becomes more spread out across the moist alveolar lining. This increases surface tension and slows the rate of expansion, ensuring all alveoli inflate at roughly the same rate.       Source


Free Alveolar Macrophage

The alveolar macrophage stands as the guardian of the alveolar–blood interface, serving as the front line of cellular defense against respiratory pathogens. Alveolar macrophages are the primary phagocytes of the innate immune system, clearing the air spaces of infectious, toxic, or allergic particles that have evaded the mechanical defenses of the respiratory tract, such as the nasal passages, the glottis, and the mucociliary transport system. By secretion of oxygen metabolites, lysozyme, antimicrobial peptides and proteases, and through processes of phagocytosis and intracellular killing, alveolar macrophages can eliminate the small inocula of typical microbes which are aspirated daily in the normal host. Alveolar macrophages also function as regulators of innate alveolar defenses against respiratory infection. When faced with larger numbers of infectious particles or more virulent microbes, alveolar macrophages synthesize and secrete a wide array of cytokines (including interleukins-1, -6, and tumor necrosis factor-α), chemokines (including interleukin-8), and arachidonic metabolites. Using these cell to cell signals, alveolar macrophages initiate inflammatory responses and recruit activated neutrophils into the alveolar spaces.      Source