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08-26-09 ALH 3205: Anatomy of the Thorax Thorax: - It is defined as the part of the trunk between the neck and the abdomen. - It is surrounded by the thoracic walls - It contains the thymus gland, the heart, lungs, distal part of the trachea, and most of the esophagus. - Thorax wall consist of skin, fascia, nerves, blood vessels, muscles, and bone. The Skeleton of the Thorax: - Forms the osteocartilaginous cage that protects the heart, lungs, and a portion of some abdominal organs i.e. the liver. - The bony thorax includes the 12 thoracic vertebrae and their intervertebral discs, the 12 pairs of ribs, and their associated costal cartilages, and the sternum. Features of Thoracic Vertebrae: - They have costal facets on their bodies for rib articulations. - They also have costal facets on transverse processes for articulations with tubercles of ribs. - They have long spinous processes. - Ribs 2-9: have superior (on top of each rib) demi facet for articulations with the vertebrae above them and inferior demi facet for articulation with their own vertebrae. - Movement between adjacent vertebrae is extremely limited to protect thoracic viscera. - The bodies of the thoracic vertebrae 5-8: are in contact with the descending thoracic aorta and sometimes the vessel can create an impression on those vertebrae (a slight indentation/erosion that is visible on an x-ray) - Aorta is behind the diaphragm and passes through abdomen column by the vertebral column (does not affect breathing) Ribs: - The first 7 pairs of ribs are called the True Ribs or the Vertebral Sternal Ribs (because the attach to the vertebral column posteriorly, and attach to the sternum anteriorly through the costal cartilage). - Ribs 8-10 are referred to as the False Ribs or Vertebral Chondral Ribs because they attach to vertebrae posteriorly, but anteriorly they attach through their cartilage to the cartilage of rib #7 and then collectively to the sternum. - 11 & 12 are referred to as the free or floating ribs because they both posteriorly attach to respected vertebrae but anteriorly they end in the posteriorly abdominal musculature. Costal Cartilage: contributes to elasticity of the thorax anteiroly. Can undergo arthritic degeneration causing a condition is called Costal Chondritis, where they become stiff and lose theoir elasticity. Breathing becomes difficult and painful Cartiliage of ribs 7, 8, 9, 10: The Infrasternal angle is formed by the costal margin where the right side and left side meet (right in the midline where xyphoid process is located. - Ribs are separated from each other through intercostals spaces. These spaces are occupied with intercostals muscles, nerves, and blood vessels. Typical Ribs 3-9 have certain specific characteristic: a.) Wedge shaped heads with 2 articular facets that are separated by a crest. The facets are for articulations are for the vertebrae above and its own vertebrae. b.) They have a neck that separates the head of the tubercle. c.) They have a tubercle located at the junction of the neck and shaft of the rib. This tubercle has an articular facet on it for articulations with the transverse process of the corresponding vertebrae d.) Each rib 3-9 has a shaft that is thin and flat with and angle at the point of greatest curvature as it comes around to the front. Atypical Ribs - Ribs pair #1 are the broadest, shortest, and most curved of the true ribs - Rib pair #2 is thinner and longer; has 2 facets for articulations with thoracic 1 & 2. - Rib pair #10 is unique that it only had 1 facet for articulation with T10 - Rib pair #11 and #12 have no neck and no tubercle. Clincal Anatomy: Fracture of Ribs: - The weakest part of any rib is just anterior to its angle, which is the point of greatest curvature (where it swings around to the front). - Rib fractures in infants and children are extremely rare because their thorax is very elastic. - Rib fractures are very painful due to the thoracic cage’s movement during breathing. It is extreme pain in a localized region when breathing. - Rib pairs #1 & #2 because of their protection by the clavicle and #11 and #12 because they are floating are the least frequent ribs to break. - Rib fractures sometimes cannot be seen on an x-ray but can be felt thorugh palpation and telling the Pt to breathe. Flail chest: - is often referred to as a stove in chest - occurs when a large setion of the anterior and or lateral chest wall is freelt movable due to multiple fractions. This condition allows for the of the chest wall to move paradoxally (breathing in abdomen will go in: breathing out abdomen will go out) Thoractomy: - any procedure on thoracic wall - Cervical ribs are sometimes present (are small) and are associated with T7. They are of no significance unless they present neurovascular symptoms. For example, if they compress the inferior trunk of the brachial plexus, which will cause a tingling sensation on the medial surface of the forearm. Or, the small rib compresses the sublcavian artery, which will cause ischemic related pain. - In rare incidence, lumbar ribs may be present (primarily L1) and are often confused with a fracture of the spinous process of the lumbar vertebrae. - Costal cartilages are hyaline cartilages Sternum: - Also known as the breast bone. - Is a flat bone in anterior thorax. - 3 parts: 1.) Manubrium o Located at T3 & T4 o Top is thick and has has an indentation called the jugular notch or the suprasternal notch (easily palpable) o On each side of the manubrium just below thew jugular notch is the clavicular notch for articulation of the clavicle o Rib pair #1 articulates with the manubrium just below the clavicular notch. o The angle of Lewis is located where the manubrium meets the body; it is just adjacent to the second pair of costal cartilages, about the level of T4 & T5. 2.) Body o Runs from T5-T9 3.) Xyphoid Process o The smallest and most variable (most mobility) is at the bottom of the sternum *Superior Thoracic Aperture: - is where the neck enters the thorax. - The structures passing through include the trachea, esophagus, nerves, blood vessels, lymphatics. - It is bounded by the first thoracic vertebrae (back), the first pair of ribs (front), and manubrium makes a circle. *Inferior Thoracic Aperture: - Is the border between the thorax and the abdomen - It is covered by the diaphragm - It is bounded by T12, rib pair #12, the costal cartilage of 7-10, and xyphoid sterna point (where xyphoid attaches to body of sternum) Breasts (plates 182-184): - Contain the mammary glands and are located in the superficial fascia of the anterior thoracic wall - Both males and females have breast tissue, but mammary glands develop in females due to estrogen. - At the point of greatest prominence is a nipple surrounded by a pigmented area called the areolar - Post-puberty female breast contains up to 20 lactiferous glands, which drain by a lactiferous duck to the nipple. - The circular base of the female breast runs from rib #2 to rib #6, and transversely from the lateral border of the sternum to the mid-axillary line. - A small portion of breast tissue extends superior laterally (up and to the side) on the inferior border of the pectoralis major muscle. That portion is called the axillary tail of the breast. - About 2/3’s of the breast lies on the fascia of the pectoralis major muscle - About ½ of the breast fascia of the Serratus anterior muscle - Between the breast and the deep fascia is a space called the retromammary space (bursa), which allows for breast movement. - The lactiferous glands are attached to the dermis of the overlying skin by the suspensory (Coopers) ligaments. These ligaments are best developed/strongest in the superior part of the breast. Vascular Supply to the Breast: A.) Arterial Supply: - The anterior intercostals arteries, which are branches of the internal thoracic artery, which is a branch of the subclavian. (Subclavian gets its name because it goes under the subclavian muscle. It gives off the internal thoracic artery right along the sternum. This also has anterior branches that are intercostals and go to the breast) - The lateral thoracic artery is off of the axial artery (a continuation of the subclavian) and the thoracoacromio supplys to a small portion of the breast on top. - Gets arterial blood from posterior intercostal arteries, which arise from the thoracic aorta. B.) Venous Drainage - By the internal thoracic vein and the axiallary vein C.) Lymph Drainage - Lymph from the breast drains into the subareolar plexus and from there, 75% of the lymph drains to the axillary lymph nodes. The axillary lymph nodes are made up of a group of 5 specific nodes: the pectoral, subscapular, apical, lateral, and central lymph nodes. - The balance (other 25%) circulates to the infraclavicular, supraclavicular, and parasternal lymph nodes. - There are some lymph nodes that pass from one breast to the other. - Any blockage/interference with lymph drainage (occurs with breast cancer) produces a leathery appearance to the skin of the breast. The skin often appears to be dimpled (like the skin of an orange). The dimpling is due to the shortening of the suspensory ligaments. Nerves to the breast are associated with the anterior and lateral branches of T4, T5, & T6. Respiration/Inhalation/Ventilation - *Look at external (inspiration) and internal costal (expiration) muscles* - 12 pairs of thoracic spinal nerves. As soon as a spinal nerve passes through an interverebral foramina. Each one divides into a ventral and dorsal ramus. The ventral rami move through the intercostal spaces while the dorsal rami innervate sensory and motor of muscles, joints, bones, and skins of back. Arterial Supply to thoracic wall: - Posterior intercostals arteries (originate from thoracic aorta) - Anterior intercostals arteries come off of the internal thoracic (which is off of the subclavian) - There are some subcostal vessels that come off of the thoracic aorta. Thoracic Cavity: - Has 3 compartments: 2 lateral compartments (each containing a lung), Central Compartment containing everything else - Each lung is surrounded by a pleural sac. There are 2 layers to the pleural sac: the outer parietal pleura, which adheres to the thoracic wall, the inner viscera pleura that covers the surface and invaginates into the fissures of each lung. The space between the 2 pleura areas is a potential space. (they can slide between each other but are very hard to pull apart - The parietal pleura adheres to thoracic wall, mediastenum, and diaphragm. - The parietal pleura is named based on location. The costal pleura is part of the parietal pleura that is on the inside surface of the skin. - The medialstinal pleura is part of the pleura that lines the mediastum - The diaphragmatic pleura is part of the pleura that adheres to the superior surface of the diaphragm. - The cervical pleura, which is often referred to as the cupula pleura, is part of the pleura that extends 3 cm up to the neck where the dome of apex of the lung is located (up on top) Lungs: - Soft spongy, extremely elastic - Are attached to heart, trachea, and mediastinum (at the root of the lung). This is an area of continuity where the 2 layers of pleura come together. - The hyalum (doorway) of the lung contains the main stem bronchi, the pulmonary vessels, and nerves, - The right lung has 3 lobes while the left lung has 2 lobes due to space - The Right lung has an horizontal and oblique fissure dividing it into 3 lobes, while the left lung only has an oblique fissure dividing it into 2 lobes. - The lobes of the right lung are described as superior, middle, and inferior. - The lobes of the left lung are described as superior and inferior. - Each lung has an apex on top (by the cupula) - Each lung is described as having 3 surfaces and 3 borders. - A border is where 2 surfaces meet - Each lung has a costal surface (in contact with rib cage), diaphragmatic surface, and a mediastinal surface (down midline) - The anterior border is where the costal and medialstinal surfaces meet. - The inferior border surrounds the diaphragmatic surface - The posterior border is where the costal and mediastinal surfaces meet posteriorly, Bronchi: - The right main bronchus and left main bronchus (also known as the left and right primary bronchi) course inferiorly and laterally from the trachea. They are supported by C shaped rings of cartilage except at the point of bifurcation where there is a triangular piece of cartilage called the curina. The curina keeps the 2 primary bronchi properly oriented. - The right main stem bronchus is shorter and more vertical, which is why inhaled objects will tend to lodge on the right side. - The left main stem bronchus courses/travels to the inferior to the arch of the aorta and anterior to the esophagus. - Each main stem bronchi divides into secondary bronchi, and each secondary bronchus divides into a lobe of a lung. Right lung has 3 secondary bronchi and Left lung has 2 secondary bronchi. Each secondary bronchi divides into tertiary which supply segments of each lung. - Vasculature of Lung - Each lung has a pulmonary artery carrying oxygen deficient blood to the lung for gas exchange - Has to 2 pulmonary veins that return oxygen rich blood to the atrium. - The pulmonary artery sends a branch to each lobe of each lung. - Bronchial arteries are what supply oxygen rich blood to lung tissue and pleura and arise from thoracic aorta. After supplying the lung tissue and pleura with oxygen and nutritional requirements. The bronchial arteries anastomose (join with) with the pulmonary arteries. - Lymphatic Plexuses: there are 2 in the lung and they commincute with each other . A superficial lymphatic plexus that drains to tracheobronchial lymph nodes. There are deep lymphatic plexus in the lung and drains into pulmonary lymph nodes along the primary bronchi. (cancer can spread quickly from one lung to another due to lympathics) Nerves Associated with Lung - Parasympathetic nerves to the bronchi are associated with CN10 (Vagus). When they become active, they innervate the smooth muscle of the bronchial tree. Second, it inhibits the smooth muscles in the pulmonary vessels causing vasodilation. Third, it increases glandular secretions in the lungs. - Sympathetic Innervation is inhibitory to the bronchial smooth muscle causing bronchial dilation ( this is different for the parasympathetic because the parasympathetic inhibits smooth muscle in the vessels only). It is more motor to the vascular smooth muscle causing vasoconstriction. It inhibits glandular secretions. - The right vagus nerve enters the thorax anterior to the right subclavian artery where it then gives off the right recurrent laryngeal nerve that is motor to the larynx. The right vagus continues to go down and it gives off a esophageal plexus, cardial plexus, etc. (many groups of nerves) - The left vagus also descends downward on the left side of the aorta, where it then gives off the left recurrent laryngeal nerve. It also then continues down the abdomen giving off many branches. - The recurrent laryngeal nerves (left and right) supply all the intrinsic muscles of the larynx. ( if you can’t move your larynx, you can’t make noise) - The phrenic nerve on both sides are the only motor nerves to the diaphragm. Half of the fibers in each phrenic nerve are sensory and the other half if motor. The right phrenic nerve descends along the IVC (inferior vena cava) and the left phrenic nerve descends right across the left atrium and then down the diaphragm. - The phrenic nerve is made up of CN3 CN4 CN5 and it keeps the person alive. Medialstinum: - Is the central part of the thorax between the 2 pleural spaces. It extends from the superior thoracic aperature to the diaphragm. From the sternum anteriorly in the front to the thoracic vertebrae posteriorly. - The structures of the mediastinum are surrounded by connective tissue, nerves, blood, lymph vessels, and fat. - Functionally, the looseness and degree of elasticity of the connective tissue coupled with the elasticity of the lungs allows for volume changes in the thoracic cavity. - The superior medialstium runs from the superior thoracic apperature down to a plane that runs from a sternal angle (at T4). - The inferior medialstinum runs from the sterna angle back to T4 and all the way down to the diaphragm. The inferior medialstinum is further divided into an anterior, middle, and posterior portion. - The middle part of the inferior medialstinum contains the heart and the great vessels. The anterior part of the inferior medialstinum contains whatever is in front of the heart (lymph tissues, lymph nodes, connective tissue, fat, nerves) - Behind the heart in the posterior portion of the inferior medialstinum is the thoracic aorta, the thoracic duct (returns 75% of lymph to vascular system), and esophagus. - The superior medialstinum contains the thymus gland, the arch of the aorta, the SVC (superior vena cava), vagus nerve, phrenic nerve, brachiocephalic veins, and trachea - The pericardium is a doubled wall fibroserous sac enclosing the heart and the origin of the great vessels (great vessel is a vessel that directly enters or leaves the heart) - The pericardium is behind the sternum and runs anteriorly to the front to the 2nd to the 6th costal cartilage, and posteriorly, to T5 and T8. - The fibrous or outer portion is fused with the tunica adentia (tunica externa layer of the great vessels) and is attached to the posterior surface of the sternum by the sternopericardial ligaments. - The pericardium gives the heart a mechanical support when it contracts - The pericardium is fused with the central tendon of the diaphragm - The serous pericardium (itself) has an outer and inner surface - The inner surface is visceral and the outer surface is parietal and is attached to the fibrous pericardium (between the 2 are the pericardial space) 5 Functions of the Respiratory System 1.) Ventilation: air into and out of the lungs 2.) External Respiration: is the gas exchange between the alveoli and capillary blood. 3.) Gas Transport: how physically are the gases transported by the bloodstream 4.) Internal Respiration: gas exchange between the systemic capillaries and the metabolically active cells of the body (tissues) 5.) Cellular respiration: the metabolic use of oxygen of the cells of the body (krebs cycle, mitochondria) The anatomical positions of the respiratory system are categorized as being in the conducting position or the respiratory position. - The conducting position contains all the anatomical structures that provide a pathway through which the air must travel to get to the respiratory division (oral cavity, pharynx, larynx, trachea, bronchi) - The respiratory position is where the external respiration takes place(respiratory bronchioles, alveolar ducts, and alveoli) - The volume of air in the conducting position is referred to as the dead space - The minute ventilation (volume of air you breathe in and out every minute) is a function of breathing rate and tidal volume (volume of air you breathe in OR out with every breath) VE= BR x TV 6000 ml/min = 12 breaths/min x 500 ml/breath - Averaging breathing rate is 12 breaths per minute. - Average tidal volume is 500 ml/breath - DSA = dead space (person’s weight in lbs.) Remember: **Nose: - Is important for ventilation - It moistens and warms the air **3 primary functions of the pleura: - Seruous fluid that is synthesized and secreted acts as a lubricant for smooth lung movement. - Remember that the pressure in the pleural space is sub-atmospheric which causes the lung to adhere to the thoracic wall. - The pleura effectively isolates everything in the medialstinum from the lungs - At rest, inspiration is active and expiration is passive.
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