1--Frontal sinus
Sinuses are mucosa-lined airspaces within the bones of the face and skull. The frontal sinuses, situated behind the superciliary arches, are absent at birth, but are generally fairly well developed between the seventh and eighth years, only reaching their full size after puberty. The frontal bone is membranous at birth and there is rarely more than a recess until the bone tissue starts to ossify about age two. Consequently this structure does not show on radiographs before that time. Frontal sinuses are rarely symmetrical and the septum between them frequently deviates to one or other side of the middle line. Sinus development begins in the womb, but only the maxillary and ethmoid sinuses are present at birth. Approximately 5% of people have absent frontal sinuses.
Their average measurements are as follows: height 28 mm, breadth 24 mm, depth 20 mm, creating a space of 6-7 ml.
Each opens into the anterior part of the corresponding middle meatus of the nose through the frontonasal duct which traverses the anterior part of the labyrinth of the ethmoid. These structures then open into the hiatus semilunaris in the middle meatus.
The mucous membrane in this sinus is innervated by the supraorbital nerve, which carries the postganglionic parasympathetic nerve fibers for mucous secretion from the ophthalmic nerve and supplied by the supraorbital artery and anterior ethmoidal artery.
Through its copious mucus production, the sinus is an essential part of the immune defense/air filtration carried out by the nose. Nasal and sinal mucosae are ciliated and move mucus to the choanae and finally to the stomach. The thick upper layers of nasal mucus trap bacteria and small particles in tissue abundantly provided with immune cells, antibodies, and antibacterial proteins. The layers beneath are thinner and provide a substrate in which the cilia are able to beat and move the upper layer with its debris through the ostia toward the choanae.
Inflammations of the frontal sinus can give rise to serious complications, as it is in close proximity to the orbit and cranial cavity (orbital cellulitis, epidural and subdural abscess, meningitis).
2--Sphenoid sinus
The two sphenoidal sinuses (or sphenoid) contained within the body of the sphenoid vary in size and shape; owing to the lateral displacement of the intervening septum they are rarely symmetrical.
The following are their average measurements: vertical height, 2.2 cm.; transverse breadth, 2 cm.; antero-posterior depth, 2.2 cm.
Relations
When exceptionally large they may extend into the roots of the pterygoid processes or great wings, and may invade the basilar part of the occipital bone.
Each sinus opens into the roof of the nasal cavity via apertures on the posterior wall of the sphenoethmoidal recess directly above the choana. The apertures are located high on the anterior walls of the sinuses themselves.
Because only thin shelves of bone separate the sphenoidal sinuses from the nasal cavities below and hypophyseal fossa above, the pituitary gland can be surgically approached through the roof of the nasal cavities by first passing through the anterioinferior aspect of the sphenoid bone and into the sinuses, followed by entry through the top of the sphenoid bone into the hypophyseal fossa.
If a fast-growing tumor erodes the floor of the sinus, the vidian nerve could be in danger. If the tumor spreads laterally, the cavernous sinus and all its constituent nerves could be in danger.
Innervation
The mucous membrane receives sensory innervation by the posterior ethmoidal nerves, and postganglionic parasympathetic fibers of the facial nerve that synapsed at the pterygopalatine ganglion which control secretion of mucous.
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3--Nasal cavity
The nasal cavity (or nasal fossa) is a large air filled space above and behind the nose in the middle of the face.
Function
The nasal cavity conditions the air to be received by the other areas of the respiratory tract. Owing to the large surface area provided by the nasal conchae, the air passing through the nasal cavity is warmed or cooled to within 1 degree of body temperature. In addition, the air is humidified, and dust and other particulate matter is removed by vibrissae, short, thick hairs, present in the vestibule. The cilia of the respiratory epithelium move the particulate matter towards the pharynx where it passes into the esophagus and is digested in the stomach.
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4--Nasal vestibule
Nasal Vestibule is the most anterior part of the nasal cavity. It is enclosed by the cartilages of nose and lined by the same epithelium of the skin (Stratified squamous, keratinized). The other part of the nasal cavity, which is lined by the respiratory epithelium, is called nasal cavity proper. Inside the vestibule are small hairs called vibrissae, which filter dust and other matter that you breathe in.
5--Mouth cavity
The first space of the mouth is the mouth cavity, bounded laterally and in front by the alveolar arches (containing the teeth), and posteriorily by the isthmus of the fauces. The oral cavity is also known as the mouth which swallows food and drinks that then go down the esophagus and into the stomach.
6--Pharynx
The human pharynx (plural: pharynges) is the part of the throat situated immediately posterior to (behind) the mouth and nasal cavity, and superior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx (epipharynx), the oropharynx (mesopharynx), and the laryngopharynx (hypopharynx). The pharynx is part of the digestive system and also the respiratory system; it is also important in vocalization.
7--Epiglottis
The epiglottis is a flap that is made of elastic cartilage tissue covered with a mucous membrane, attached to the entrance of the larynx. It projects obliquely upwards behind the tongue and the hyoid bone, pointing dorsally. The term, like tonsils, is often incorrectly used to refer to the uvula. There are taste buds on the epiglottis.
Anatomy and function
The epiglottis guards the entrance of the glottis, the opening between the vocal folds. It is normally pointed upward while one is breathing with its underside functioning as part of the pharynx, but while one is swallowing, elevation of the hyoid bone draws the larynx upward; as a result, the epiglottis folds down to a more horizontal position, with its superior side functioning as part of the pharynx. In this manner it prevents food from going into the trachea and instead directs it to the esophagus, which is posterior.
The epiglottis is one of nine cartilaginous structures that make up the larynx (voice box). While one is breathing, it lies completely within the pharynx. When one is swallowing it serves as part of the anterior of the larynx.
In some languages, the epiglottis is used to produce speech sounds, though this sound-type is rather rare. Further information can be found under epiglottal consonant.
8--Vocal folds
The vocal folds, also known commonly as vocal cords, are composed of twin infoldings of mucous membrane stretched horizontally across the larynx. They vibrate, modulating the flow of air being expelled from the lungs during phonation.
Open during inhalation, closed when holding one's breath, and vibrating for speech or singing (oscillating 440 times per second when singing A above middle C), the folds are controlled via the vagus nerve. They are white because of scant blood circulation.
8--Thyroid cartilage
The thyroid cartilage is the largest of the nine cartilages that make up the laryngeal skeleton, the cartilage structure in and around the trachea that contains the larynx.
It is composed of two plate-like laminae that fuse on the anterior side of the cartilage to form a peak, called the laryngeal prominence. This prominence is often referred to as the "pomus Adamus" or "Adam's apple". The laryngeal prominence is more prominent in adult male than female because of the difference in the size of the angle: 90° in male and 120° in female.
The lip of the thyroid cartilage just superior to the laryngeal prominence is called the superior thyroid notch, while the notch inferior to the thyroid angle is called the inferior thyroid notch.
Its posterior border is elongated both inferiorly and superiorly to form the superior horn of thyroid cartilage and inferior horn of thyroid cartilage
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9--Cricoid cartilage
The cricoid cartilage, or simply cricoid (from the Greek krikoeides meaning "ring-shaped"), is the only complete ring of cartilage around the trachea.
Location
The cricoid cartilage sits just inferior to the thyroid cartilage in the neck, and is joined to it medially by the median cricothyroid ligament and postero-laterally by the cricothyroid joints. Inferior to it are the rings of cartilage around the trachea (which are not continuous - rather they are C-shaped with a gap posteriorly). The cricoid is joined to the first tracheal ring by the cricotracheal ligament, and this can be felt as a more yielding area between the firm thyroid cartilage and firmer cricoid.
It is also anatomically related to the thyroid gland; although the thyroid isthmus is inferior to it, the two lobes of the thyroid extend superiorly on each side of the cricoid as far as the thyroid cartilage above it.
The posterior part of the cricoid is slightly broader than the anterior and lateral parts, and is called the lamina, while the anterior part is the band; this may be the reason for the common comparison made between the cricoid and a signet ring.
10--Trachea
The trachea has an inner diameter of about 21 to 27 millimetres (0.83 to 1.1 in) and a length of about 10 to 16 centimetres (3.9 to 6.3 in). It commences at the larynx, level with the fifth cervical vertebra, and bifurcates into the primary bronchi at the vertebral level of T4/T5.
There are about fifteen to twenty incomplete C-shaped cartilaginous rings that reinforce the anterior and lateral sides of the trachea to protect and maintain the airway. The trachealis muscle connects the ends of the incomplete rings and contracts during coughing, reducing the size of the lumen of the trachea to increase the air flow rate. The esophagus lies posteriorly to the trachea. The cartilaginous rings are incomplete to allow the trachea to collapse slightly so that food can pass down the esophagus. A flap-like epiglottis closes the opening to the larynx during swallowing to prevent swallowed matter from entering the trachea.
11--Apex
The apex of the lung is rounded, and extends into the root of the neck, reaching from 2.5 to 4 cm. above the level of the sternal end of the first rib.
A sulcus produced by the subclavian artery as it curves in front of the pleura runs upward and lateralward immediately below the apex.
12--Human right lung
The human right lung is divided into three lobes (as opposed to two lobes on the left), superior, middle, and inferior, by two interlobular fissures:
Fissures
* One of these, the oblique fissure, separates the inferior from the middle and superior lobes, and corresponds closely with the fissure in the left lung. Its direction is, however, more vertical, and it cuts the lower border about 7.5 cm. behind its anterior extremity.
* The other fissure, the horizontal fissure, separates the superior from the middle lobe. It begins in the previous fissure near the posterior border of the lung, and, running horizontally forward, cuts the anterior border on a level with the sternal end of the fourth costal cartilage; on the mediastinal surface it may be traced backward to the hilum.
Lobes
The middle lobe, the smallest lobe of the right lung, is wedge-shaped, and includes the lower part of the anterior border and the anterior part of the base of the lung. (There is no middle lobe on the left lung, though there is a lingula.)
The superior and inferior lobes are similar to their counterparts on the left lung.
Difference in size
The right lung, although shorter by 5 cm. than the left, in consequence of the diaphragm rising higher on the right side to accommodate the liver, is broader, owing to the inclination of the heart to the left side. Consequently, the volume, the total capacity and the weight of the right lung is higher than that of the left.
Impressions
On the mediastinal surface, immediately above the hilum, is an arched furrow which accommodates the azygos vein; while running upward, and then arching lateralward some little distance below the apex, is a wide groove for the superior vena cava and right innominate vein; behind this, and nearer the apex, is a furrow for the innominate artery.
Behind the hilum and the attachment of the pulmonary ligament is a vertical groove for the esophagus; this groove becomes less distinct below, owing to the inclination of the lower part of the esophagus to the left of the middle line.
In front and to the right of the lower part of the esophageal groove is a deep concavity for the extrapericardiac portion of the thoracic part of the inferior vena cava.
13--Lobar bronchus
Secondary bronchi (also known as lobar bronchi) arise from the primary bronchi, with each one serving as the airway to a specific lobe of the lung.
Structure
They have relatively large lumens that are lined by respiratory epithelium. There is a smooth muscle layer below the epithelium arranged as two ribbons of muscle that spiral in opposite directions. This smooth muscle layer contains seromucous glands. Irregularly arranged plates of hyaline cartilage surround the smooth muscle. These plates give structural support to the bronchus and maintain the patency of the lumen.
A bronchus has cartilage plates, smooth muscle, and mucus-secreting gland-cells in its wall. It also has lining cells with cilia departing towards the mouth; this removes dust and other small debris.
Secondary bronchi of right lung
* superior lobe bronchus (or eparterial bronchus)
* middle lobe bronchus
14--Horizontal fissure
The horizontal fissure of right lung (or transverse fissure) is a fissure separating the superior lobe from the middle lobe.
The left lung has no middle lobe, so there is no horizontal fissure on that lung.
The Horizontal fissure usually extends from the oblique fissure along the border of the 4th rib.
15..Oblique fissure
In the lung, the oblique fissure (or major fissure) separates the inferior lobe of either lung from the remainder of the lung. (In the right lung, it separates the inferior from the superior and middle lobe; in the left lung it separates the inferior and superior lobe, as there is no middle lobe in the left lung.)
The oblique fissure extends from the spinous process of T2 (posteriorly) to 6th costal cartilage (anteriorly).
16..Human right lung
The human right lung is divided into three lobes (as opposed to two lobes on the left), superior, middle, and inferior, by two interlobular fissures:
Fissures
* One of these, the oblique fissure, separates the inferior from the middle and superior lobes, and corresponds closely with the fissure in the left lung. Its direction is, however, more vertical, and it cuts the lower border about 7.5 cm. behind its anterior extremity.
* The other fissure, the horizontal fissure, separates the superior from the middle lobe. It begins in the previous fissure near the posterior border of the lung, and, running horizontally forward, cuts the anterior border on a level with the sternal end of the fourth costal cartilage; on the mediastinal surface it may be traced backward to the hilum.
Lobes
The middle lobe, the smallest lobe of the right lung, is wedge-shaped, and includes the lower part of the anterior border and the anterior part of the base of the lung. (There is no middle lobe on the left lung, though there is a lingula.)
The superior and inferior lobes are similar to their counterparts on the left lung.
Difference in size
The right lung, although shorter by 5 cm. than the left, in consequence of the diaphragm rising higher on the right side to accommodate the liver, is broader, owing to the inclination of the heart to the left side. Consequently, the volume, the total capacity and the weight of the right lung is higher than that of the left.
Impressions
On the mediastinal surface, immediately above the hilum, is an arched furrow which accommodates the azygos vein; while running upward, and then arching lateralward some little distance below the apex, is a wide groove for the superior vena cava and right innominate vein; behind this, and nearer the apex, is a furrow for the innominate artery.
Behind the hilum and the attachment of the pulmonary ligament is a vertical groove for the esophagus; this groove becomes less distinct below, owing to the inclination of the lower part of the esophagus to the left of the middle line.
In front and to the right of the lower part of the esophageal groove is a deep concavity for the extrapericardiac portion of the thoracic part of the inferior vena cava.
17..Diaphragm
The thoracic diaphragm, or simply the diaphragm, is a sheet of internal skeletal muscle that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity (heart, lungs & ribs) from the abdominal cavity and performs an important function in respiration. A diaphragm in anatomy can refer to other flat structures such as the urogenital diaphragm or pelvic diaphragm, but "the diaphragm" generally refers to the thoracic diaphragm. Other vertebrates such as amphibians and reptiles have diaphragms or diaphragm-like structures, but important details of the anatomy vary, such as the position of lungs in the abdominal cavity.
18..Human left lung
The human left lung is divided into two lobes, an upper and a lower, by the oblique fissure, which extends from the costal to the mediastinal surface of the lung both above and below the hilum.
As seen on the surface, this fissure begins on the mediastinal surface of the lung at the upper and posterior part of the hilum, and runs backward and upward to the posterior border, which it crosses at a point about 6 cm. below the apex.
It then extends downward and forward over the costal surface, and reaches the lower border a little behind its anterior extremity, and its further course can be followed upward and backward across the mediastinal surface as far as the lower part of the hilum.
Impressions
On the mediastinal surface, immediately above the hilum, is a well-marked curved furrow produced by the aortic arch, and running upward from this toward the apex is a groove accommodating the left subclavian artery; a slight impression in front of the latter and close to the margin of the lung lodges the left innominate vein.
Behind the hilum and pulmonary ligament is a vertical furrow produced by the descending aorta, and in front of this, near the base of the lung, the lower part of the esophagus causes a shallow impression.
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19..Lingula of the left lung
The human left lung, unlike the right, contains no middle lobe. However, the term lingula is used to denote a projection of the upper lobe of the left lung that serves as the homologue. Some sources define the lingula as a distinct lobe.
There are two bronchopulmonary segments of the lingula: Superior and inferior.
It is thought that the lingula of the left lobe is the remnant of the middle lobe of the left lung, which has been lost through evolution, but this cannot be proven.
20..Cardiac notch of left lung
The anterior border of the right lung is almost vertical, and projects into the costomediastinal sinus; that of the left lung presents, below, an angular notch, the cardiac notch, in which the pericardium is exposed. Opposite this notch the anterior margin of the left lung is situated some little distance lateral to the line of reflection of the corresponding part of the pleura. The cardiac notch lies along the fifth and sixth intercostal space, and the spaces can be used to access the heart in pericardiocentesis to relieve cardiac tamponade.
22..Oblique fissure
In the lung, the oblique fissure (or major fissure) separates the inferior lobe of either lung from the remainder of the lung. (In the right lung, it separates the inferior from the superior and middle lobe; in the left lung it separates the inferior and superior lobe, as there is no middle lobe in the left lung.)
The oblique fissure extends from the spinous process of T2 (posteriorly) to 6th costal cartilage (anteriorly).
23..Bronchus
A bronchus (plural bronchi, adjective bronchial) is a passage of airway in the respiratory tract that conducts air into the lungs. The bronchus branches into smaller tubes, which in turn become bronchioles. 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 at the anatomical point known as the carina. The right main bronchus is wider, shorter, and more vertical than the left main bronchus. The right main bronchus subdivides into three lobar bronchi, while the left main bronchus divides into two. The lobar bronchi divide into tertiary bronchi, also known as segmentalinic bronchi, each of which supplies a bronchopulmonary segment. A bronchopulmonary segment is a division of a lung 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 two to 11 alveolar ducts. There are five or six 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 fourth 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 those 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.
24..Carina of trachea
In anatomy, the carina is a cartilaginous ridge within the trachea that runs anteroposteriorly between the two primary bronchi at the site of the tracheal bifurcation at the lower end of the trachea (usually at the level of the 4th to 5th thoracic vertebrae, which is in line with the Angle of Louis).
The mucous membrane of the carina is the most sensitive area of the trachea and larynx for triggering a cough reflex. Widening and distortion of the carina is a serious sign because it usually indicates carcinoma of the lymph nodes around the region where the trachea divides.
25..Lingula of the left lung
The human left lung, unlike the right, contains no middle lobe. However, the term lingula is used to denote a projection of the upper lobe of the left lung that serves as the homologue. Some sources define the lingula as a distinct lobe.
There are two bronchopulmonary segments of the lingula: Superior and inferior.
It is thought that the lingula of the left lobe is the remnant of the middle lobe of the left lung, which has been lost through evolution, but this cannot be proven.
26..Human left lung
The human left lung is divided into two lobes, an upper and a lower, by the oblique fissure, which extends from the costal to the mediastinal surface of the lung both above and below the hilum.
As seen on the surface, this fissure begins on the mediastinal surface of the lung at the upper and posterior part of the hilum, and runs backward and upward to the posterior border, which it crosses at a point about 6 cm. below the apex.
It then extends downward and forward over the costal surface, and reaches the lower border a little behind its anterior extremity, and its further course can be followed upward and backward across the mediastinal surface as far as the lower part of the hilum.
Impressions
On the mediastinal surface, immediately above the hilum, is a well-marked curved furrow produced by the aortic arch, and running upward from this toward the apex is a groove accommodating the left subclavian artery; a slight impression in front of the latter and close to the margin of the lung lodges the left innominate vein.
Behind the hilum and pulmonary ligament is a vertical furrow produced by the descending aorta, and in front of this, near the base of the lung, the lower part of the esophagus causes a shallow impression.
Pulmonary arteries
The pulmonary arteries carry deoxygenated blood from the heart to the lungs. They are the only arteries (other than umbilical arteries in the fetus) that carry deoxygenated blood.
In the human heart, the pulmonary trunk (pulmonary artery or main pulmonary artery) begins at the base of the right ventricle. It is short and wide - approximately 5 cm (2 inches) in length and 3 cm (1.2 inches) in diameter. It then branches into two pulmonary arteries (left and right), which deliver de-oxygenated blood to the corresponding lung.
In contrast to the pulmonary arteries, the bronchial arteries supply mainly nutrition to the lungs themselves.
Pulmonary vein
The pulmonary vein is a large blood vessel that carries blood from the lungs to the left atrium of the heart. In humans there are four pulmonary veins, two from each lung. They carry oxygenated blood, which is unusual since almost all other veins carry deoxygenated blood.
Types
They are four in number, two from each lung, and are destitute of valves. They are
* right inferior
* right superior
* left inferior
* left superior
* right superior
* left inferior
* left superior
Path
They commence as a network of capillaries on the walls of the alveoli i.e. air sacs, where they are continuous with the capillary ramifications of the pulmonary artery. The capillaries on each alveolus join together and form one vessel, which upon uniting form a single trunk for each lung lobe; three for the right, and two for the left lung.
The vein from the middle lobe of the right lung generally unites with that from the upper lobe so that ultimately two trunks from each lung are formed. The individual trunks perforate the fibrous layer of the pericardium and open separately into the upper and back part of the left atrium.
Occasionally the three veins on the right side remain separate, and not infrequently the two left pulmonary veins end by a common opening into the left atrium. Therefore, the number of pulmonary veins opening into the left atrium can vary between three and five in the healthy population.
At the root of the lung, the superior pulmonary vein lies in front of and a little below the pulmonary artery; the inferior is situated at the lowest part of the hilus of the lung and on a plane posterior to the upper vein. Behind the pulmonary artery is the bronchus.
Within the pericardium, their anterior surfaces are invested by the serous layer of this membrane.
The right pulmonary veins pass behind the right atrium and superior vena cava; the left in front of the descending thoracic aorta.
