Y1 Lungs and Muscles of Respiration 2024-25 PDF

Anatomy of the Respiratory system Year 1 UM1011 Cardiorespiratory (CVR) block 2024/25 Rachel Jones- Teaching Fellow in Anatomy Email: [email protected] UCLAN working days: Monday and Wednesday afternoons! Contact me on: [email protected] c.uk Learning o...

Anatomy of the Respiratory system Year 1 UM1011 Cardiorespiratory (CVR) block 2024/25 Rachel Jones- Teaching Fellow in Anatomy Email: [email protected] UCLAN working days: Monday and Wednesday afternoons! Contact me on: [email protected] c.uk Learning outcomes: M1.I.RES.ANA1: Outline the anatomy and histology of the respiratory tract and tracheobronchial tree. M1.I.RES.ANA2: Describe the anatomical features of the lungs, including major neurovascular supply. M1.I.RES.ANA3: Outline the primary and accessory muscles involved in respiration and the mechanism of breathing. M1.I.RES.ANA4: Describe the structures of the thoracic cage and outline the divisions and major contents of the thoracic cavity. M1.I.RES.ANA5: Outline the anatomical positions and relationships of thoracic structures in relation to surface anatomy. What we will cover today: The bony thoracic cage An overview of the respiratory system Surface anatomy of the chest The lungs, pleura and bronchial tree Muscles involved in respiration Neurovascular supply Brief histology Terminology recap: Superior = towards the head Inferior = towards the feet Anterior or Ventral = to the front Posterior or Dorsal = to the back Medial = closer to the midline Lateral = further away from the midline Proximal = closer to the trunk Distal = further away from the trunk Superficial= closer to the surface of the body Deep= closer to the centre of the body  Respiratory Anatomy PART 1: The Thoracic Cage AKA The ribcage AKA thoracic cage: Thoracic vertebrae Ribs Sternum The thoracic cage is made up of: 1) Sternum 2) 12 pairs of ribs 3) Thoracic vertebrae Its purpose is to provide structure and to protect thoracic contents (ie heart and lungs!) The thoracic cage has an ability to change its volume of space during inhalation/exhalation to allow our lungs to expand. The Rib Cage AKA the Thoracic Cage The Sternum The sternum (AKA the breastbone): Sternal angle AKA angle of Jugular notch Located anteriorly, part of the bony Louis Level of thoracic wall, helps protect the T4 vertebrae internal thoracic viscera. Made up of 3 parts: 1) 1) Manubrium Manubrium 2) Body of the 3) Xiphoid process sternum 2) Body Sternal angle AKA angle of Louis= of the where manubrium joins the body. sternum Found at the level of T4 vertebrae 3) Xiphoid The superior aspect of the process of manubrium is concave- producing a the depression called the jugular notch sternum which is visible underneath the skin. The sternum (AKA the breastbone): Costal cartilages The ribs attach anteriorly to the sternum via costal cartilages The sternum Either side of the jugular notch, there is a large fossa. These fossae articulate with the medial ends of the clavicles, forming the sternoclavicular joints. On the lateral edges of the manubrium, there is a facet for articulation with the costal cartilage of the 1st rib, and a demifacet (half-facet) for articulation with part of the costal cartilage of the 2nd rib. The lateral edges of the body of sternum are marked by articular facets which articulate with the costal cartilages of ribs 3-6. There are 2 smaller demi-facets for ribs 2 and 7. The xiphoid process is the most inferior and smallest part of the sternum. It is variable is shape/ size, with its tip located at the level of the T10 vertebrae. The xiphoid process is largely cartilaginous in structure, and completely ossifies in adulthood. On each side of its upper lateral margin is a demi-facet for articulation with the inferior end of the 7th costal cartilage The Rib Cage AKA the Thoracic Cage The Ribs The ribs: The ribs are a set of twelve pairs of bone which also help create the protective ‘cage’ of the thorax. They articulate posteriorly with the vertebral column, and terminate anteriorly as cartilage (called costal cartilage). The costal cartilage then attach the facets/demi-facets on the sternum we saw on the previous slide. As part of the bony thorax, the ribs protect the internal thoracic organs. They also have a role in breathing – during chest expansion the ribcage moves to permit lung inflation. The ribs: There are twelve pairs of ribs. Although all ribs articulate with the vertebral column posteriorly, only the costal cartilages of the ribs 1-7, articulate directly with the sternum. These are therefore called true ribs. Ribs 8-10 do not articulate directly with the sternum with their own costal cartilages. Instead they attach to the costal cartilages of ribs superior to them. Therefore termed false ribs. Ribs 11 and 12 have no anterior connection with other ribs or with the sternum and are often referred to as floating ribs. The ribs: There are two classifications of ribs – ‘Typical’ and ‘atypical’. The typical ribs have a generalised structure, while the atypical ribs have variations on this structure. Typical ribs: Typical Ribs The typical rib consists of a head, neck and body AKA shaft: The head has 2 articular facets separated by a wedge of bone. The lower facet articulates with the numerically corresponding vertebrae, and the other facet, articulates with the vertebrae above. The neck simply connects the head with the body. Where the neck meets the body, there is a roughed tubercle, with a facet for articulation with the transverse process of the corresponding vertebrae. The body, or shaft of the rib is flat and curved. The internal surface of the shaft has a groove which protects blood vessels and nerves. This is called the costal groove. A-typical ribs: Ribs 1, 2, 10 11 and 12 can be described as ‘atypical’ – they have features that are not common to all the ribs. Rib Rib 1: is shorter and wider than the other ribs. It 1 only has one facet on its head for articulation with its corresponding vertebrae (there isn’t a thoracic vertebrae above it). The superior surface is marked by two grooves, which make way for the subclavian vessels. Rib 2: is thinner and longer than rib 1, and has two articular facets on the head as normal. It has a roughened area on its upper surface, where the serratus anterior muscle attaches. Rib 10: only has one facet – for articulation with its numerically corresponding vertebrae. A-typical ribs: Rib 12 Ribs 11 and 12 articulate only with the bodies of their own vertebrae and have no tubercles or necks. Both ribs are short, have little curve, and are pointed anteriorly The ribs: Ribs 3-9 can be described as ‘typical’. Hea d Superior Nec facet k Tuberc Inferior le facet Articular facet Costal Body angle Costal groove Facet for costal cartilage The ribs: The ribs: Surface anatomy: The Rib Cage AKA the Thoracic Cage The thoracic vertebrae Costovertebral joints The twelve thoracic vertebrae are medium-sized, and increase in size from superior to inferior. Their specialised function is to articulate with ribs, producing the bony thorax. Costovertebral joints The ribs are anchored posteriorly to the 12 thoracic vertebrae (T1–T12) Each thoracic vertebra has two ‘demi facets,’ superiorly and inferiorly placed on either side of its vertebral body. The demi facets articulate with the heads of two different ribs. Costovertebral joints On the vertebral body, each thoracic vertebrae has two ‘demi facets,’ superiorly and inferiorly placed on either side of its vertebral body. The demi facets articulate with the heads of two different ribs Rib 2 articulates with the inferior demi facet of thoracic vertebra 1 (T1) and the superior demi facet of T2 On the transverse processes of the thoracic vertebrae, there is a Transverse costal facet for articulation with the shaft of a single rib. Rib 2 articulates with the costal facets of T2. Transvers e Costovertebral joints Therefore we can say each rib forms two joints: Costovertebral joint – Between the head of the rib, superior costal facet of the corresponding vertebrae, and the inferior costal facet of the vertebrae above. Costotransverse joint – Between the tubercle of the rib, and the transverse process of the corresponding vertebrae.  Respiratory Anatomy PART 2: The Respiratory Tract The respiratory system: Nose We can divide the respiratory system Pharynx structurally into upper and lower: Larynx Upper: Nose, nasal Trachea passages, paranasal sinuses, pharynx and portion of the larynx Bronchi above the vocal cords Lower: Larynx below vocal cords, trachea, bronchi, bronchioles and Lungs lungs The nasal cavity: Air enters the nose via the nasal cavity. Inside the nasal cavity on the lateral wall of each nostril lies 3 bones covered in layers of mucosa. These are called the conchae. On both the left and right side we have a superior, middle and inferior nasal conchae. The function of the conchae is to increase surface area and spin the air so that the inhaled air can be warmed and moistened ready to travel to the lungs to allow effective gaseous exchange. The nasal cavity: The oral cavity: The oral cavity acts as an air inlet in addition to the nasal cavity and lies inferior to the nasal cavity. The oral cavity is bordered superiorly by a hard palate, more anteriorly and a soft palate posteriorly. The soft palate ends at a region known as the uvula. – don’t mix this Soft up with the epiglottis! palate Hard palate Uvula The oral cavity: Soft palate Uvul a Tongue The pharynx: The pharynx can be divided into 3 parts: Nasopharynx, oropharynx and laryngopharynx Nasopharynx= posterior to nasal cavities and above soft palate Oropharynx= posterior to oral cavity, inferior to the level of the soft palate, and superior to the upper margin of the epiglottis Laryngopharynx= extends from the superior margin of the epiglottis to the top of the oesophagus Food travels down oesophagus to stomach Air travels down to trachea to lungs The tracheobronchial tree: The trachea, bronchi and bronchioles form the tracheobronchial tree – a system of airways that allow passage of air into the lungs, where gas exchange occurs. Laryngeal cartilage: You will learn more about the larynx (voice box) in further lectures over the next two years. However appreciate that the larynx is where we find our vocal cords. Sound is created by forcing air through the vocal folds of the larynx which vibrate to make noise. This is how we talk/sing! So air travels through the larynx in to the trachea. There are a few cartilage structures surrounding the larynx Larynx Laryngeal cartilage: Laryngeal cartilage Larynx Choking: Things ‘go down the wrong way’ and cause us to choke because of an anatomical flaw that we share with most other air-breathing vertebrates. Our breathing tube, the trachea, isn't segregated from the one we use for swallowing, the oesophagus. Air, food, and drink all share the same commute down the throat until the trachea branches off, right around your Adam's apple. Normally, the epiglottis keeps food and drink from going down the windpipe. This sturdy flap of cartilage is designed to snap shut automatically when we swallow, closing off the airway and shunting the sustenance down the oesophagus to meet its digestive fate! The trachea AKA the wind pipe: Posterior Anterior Through the larynx, air then travels view view through the trachea which is the Tracheal tube through which air is transported mucosa to the lungs. It runs from the level of the lower border of the cricoid Tracheal cartilage to T4 vertebral level. is Cartila muscle ge Here it bifurcates into the left & rings Trache right primary (main) bronchi al rings The trachea is formed of ‘horse shoe’ or ‘C shaped’ rings of hyaline cartilage, held together by dense connective tissue Posteriorly, at the junction where the Why is it important trachea is in contact with the tracheal rings are C oesophagus, the trachea has a shaped not full membrane void of cartilage and circles? covered in smooth muscle, the trachealis muscle The trachea AKA the wind pipe: Horse shoe shaped tracheal rings Why might this be important? The trachea: At the bifurcation of the trachea lies the carina; a Anterior ridge that can be seen on a bronchoscopy (little camera) The carina is a key landmark in determining pathologies. Widening/ distortion of the carina can often indicate cancer in the lymph nodes that lie just inferior to the carina. The name of these lymph nodes is Inferior tracheobronchial lymph nodes Cross section through trachea Bronchoscopy:  The bronchi: e trachea bifurcates into the left & right primary (main) bronchi The bronchi have characteristic hyaline cartilage rings, supporting them, the same as in the trachea. The position each bronchi sits at is different; the right is wider, shorter and lies at a steep vertical angle, whereas the left is narrower and more horizontal. Why might this be important to know….? Inhaled foreign objects are more likely to get lodged in the right side bronchus The secondary bronchi: The left & right primary (main) bronchi divide further into secondary (lobar) bronchi; 2 on the left and 3 on the right. We will see shortly that these divisions correspond to the number of lobes in each lung! The secondary bronchi then further divide to give tertiary (segmental) bronchi; usually 10 for each lung The tertiary bronchi: The secondary bronchi further divide to give tertiary (segmental) bronchi; usually 10 for each lung Terminal and respiratory bronchioles: Terminal bronchiole Each tertiary bronchi gives rise to many terminal bronchioles – these now differ in structure as they no longer have hyaline Respirat cartilage in their walls ory bronchi oles Respiratory bronchioles branch from these terminal bronchioles Each respiratory bronchiole ends in an acinus of clustered alveoli Epithelial types recap: Trachea and bronchi histology: The majority of the respiratory tree, from the nasal cavity to the bronchi, is lined by pseudostratified columnar ciliated epithelium. The bronchioles are lined by simple columnar to simple cuboidal epithelium as the tube gets narrower. The alveoli possess a lining of thin simple squamous epithelium that allows for gas exchange. So the epithelium found in the trachea and bronchi is pseudostratified columnar epithelium. The ciliated cells are located across the apical surface and facilitate the movement of mucus across the airway tract. Goblet cells secrete mucus to trap pathogens The alveoli: Type 1 pneumocyte Type 2 pneumocyte The alveolar wall has a completely different structure to the bronchioles. There are no cilia or smooth muscle and instead, the wall is lined by thin simple squamous epithelial cells called pneumocytes. Most of these are regular pneumocytes called Type 1 pneumocytes, responsible for gas- exchange. But some, called Type 2 pneumocytes, have the ability to secrete a substance called surfactant. Surfactant decreases the surface tension within Surfactant the alveoli and therefore helps keep them open (prevents them collapsing and sticking to each other). Histology of the alveoli: Surfactant and premature babies: Surfactant is a mixture of fats and proteins and acts as a lubricant to prevent our alveoli sticking together. Allows these air sacs to slide against one another without sticking. Surfactant production begins in the developing foetus at around 24-28 weeks gestation. Most babies produce enough surfactant for their lungs by around 34 weeks gestation. A baby born prematurely, before this date will likely not have enough surfactant and this can cause Respiratory Distress Syndrome (RDS) shortly after birth. The alveoli: Histology of the respiratory tract overview: The human airway, from the nasal passage to the alveolar sacs, is covered with a continuous epithelial sheet that differs in morphology and cellular composition between the conducting and respiratory zones. In the most proximal regions of the conducting zone, including the nasal passage, trachea, and bronchi, the airway epithelium exhibits a columnar, pseudostratified morphology. The height of this epithelium decreases in more distal regions of the conducting zone and resembles a cuboidal epithelium in the small airway. The major cell types of the large airway epithelium are goblet cells that produce and secrete mucus, ciliated cells that promote mucus motility through coordinated movement of their apical cilia, and basal cells that line the basement membrane and do not contact the apical surface of the epithelium. In the bronchioles, the cuboidal epithelium contains secretory club cells and fewer ciliated cells than in more proximal airway regions. The alveolar epithelium is lined with type I and II alveolar epithelial cells (AECs). The alveolar cells fuse to endothelial cells by their basal membranes to form the gas exchange barrier. Respiratory tract overview:  Respiratory Anatomy PART 3: The Lungs Main function of the lungs! The lungs: The lungs are the functional organs of respiration. We have 2 lungs- located within the chest, either side of the mediastinum and are protected anteriorly by the ribcage. The diaphragm lies inferior to lungs which separates the thoracic cavity from the abdominal cavity. The function of the lungs is to oxygenate blood. They achieve this by bringing inhaled air into close contact with oxygen-poor blood in the pulmonary capillaries They can expand down to the lower border of the ribs; the costal margin and extend as far up as the clavicle. The pleura: Each lung (right and left) is contained within a serous membrane called a pleural sac. The pleural sacs flank both sides of the heart and occupy most of the thoracic cavity. Each pleural sac is composed of two serous layers called: the parietal pleura and visceral pleura. The thin space between these two layers is called the pleural cavity. This thin pleural cavity contains a thin layer of liquid called pleural fluid which provides lubrication between the two layers of pleura as the lungs expand which helps prevent friction. The pleura: PARIET AL PLEUR A LUNG Hilum of lung VICER AL PLEUR A The pleura: The parietal pleura lines internal surface of thoracic cavity. Parietal Pleura is named differently depending on the area it is lining: Diaphragmatic parietal pleura- lines superior surface of diaphragm Mediastinal parietal pleura- lines lateral surface of mediastinum (which contains the heart). Costal parietal pleura- lines internal surface of ribs Cervical parietal pleura- extends above rib 1 to the root of the neck The visceral pleura surrounds and is intimately attached to each lung; Following the contour of the lobes. The visceral pleura is contiguous with the parietal pleura at the hilum of each lung The pleural cavity: Parietal pleura The pleural cavity (AKA pleural Visceral pleura space)= located in between the parietal pleura and visceral pleura. Pleural fluid located in this space lubricates/ facilitates gliding movement of lungs within the thoracic wall during breathing- prevents friction! Lobes of the lungs: Rig Lef ht t The lungs are divided into lobes 2 lobes on left: Superior & inferior divided by oblique fissure 3 lobes on right: Superior, middle & inferior divided by oblique fissure and horizontal fissure. Lobes of the lungs: Rig Apex Lef Apex ht t Superior lobe Superior Anterior lobe border Anterior Oblique Horizont border fissure Costal al fissure surface Middle Costal lobe surface Inferior lobe Inferior lobe Lingula Oblique fissure Inferior Base Base Inferior border border The hilum of the lungs: The hilum= located on the medial aspect of each lung. Is the site where the bronchi, arteries, veins & nerves enter/ exit the lung. Like the doorway into the lung! Bronchopulmonary segmentation of the lungs: In addition to having lobes, the lungs can be further divided into 10 segments (each) These segments have their own artery (and air supply!) so are functionally independent and can be removed by surgery (eg in the case of lung cancer) without affecting the function of surrounding segments. Rig Lef ht t The lungs in summary: Superior, Superior Lobes middle and and inferior inferior Oblique Oblique Fissures only and horizontal Bronchopulmona ry segments 10 8-10 Unique Larger and heavier Superior lobe features than left lung, characterised by shorter and wider the lingual and a (due to higher right deep cardiac notch hemidiaphragm The pulmonary circulation heart recap: Arteries = AWAY Veins = RETURN In pulmonary circulation, arteries carry deoxygenated blood and veins carry oxygenated blood. Pulmonary circulation: The pulmonary arteries deliver blood to capillaries around the alveoli where gaseous exchange takes place. Pulmonary veins return blood back to the heart Can you remember the name of the entrance to the lung on each lungs medial aspect through which these vessels run? = The Hilum  Branches off the arch of Aorta RCC LCC Common RSC LSC carotids take blood to the head and neck Subclavian’s take blood to the upper limbs. AKA thoracic aorta- until it Descending passes through diaphragm, then aorta transports its called the blood to thorax, abdominal aorta abdo/pelvis and Vasculature: The trachea and bronchial tree also need some blood supply and receive their blood supply directly from the thoracic aorta Bronchial arteries branch from thoracic aorta or sometimes also branch from the posterior intercostal arteries Vasculature: The trachea and bronchial tree are drained by slightly different routes on the left and right hand side. On the left, bronchial veins drain into the accessory hemiazygos vein which drains in to azygos (on right), into SVC. On the right, bronchial veins drain into the azygos vein. Lymphatics: The inferior tracheobronchial lymph nodes can blunt the carina when enlarged → indicating pathology Bronchoscopy Bronchoscope travels down the trachea to enter a main bronchus The bronchoscope must move around the carina to get to the bronchus If cancer cells have metastasized at the inferior tracheobronchial lymph nodes, they become enlarged and carina becomes distorted and immobile. The diaphragm: central tendon of the diaphragm Most important muscle of respiration Separates thoracic and abdominal cavity by forming floor of thoracic cavity and roof of abdominal cavity Comprised of 2 domes Peripherally is muscular – muscle fibres unite as a central tendon of the diaphragm more centrally. Diaphragm is innervated by the phrenic nerve (C3, C4, C5 … Keeps the diaphragm ALIVE!) The diaphragm: Diaphragm has 3 areas of attachment: 1) Costal cartilages and inner surface of ribs 7 – 12 2) Lumbar vertebrae and associated discs 3) Xiphoid process of sternum The parts of the diaphragm that arise from the vertebrae are known as the right and left crura: Right crus – Arises from L1-L3 and their intervertebral discs Left crus – Arises from L1-L2 and their intervertebral disc Diaphragm is innervated by the phrenic nerve (C3, C4, C5 … Keeps the diaphragm ALIVE!) The diaphragm: Contraction of diaphragm results in a downward movement of central tendon Increase in vertical size of thoracic cavity in inhalation Relaxation results in diaphragm returning to resting position. Decrease in vertical size of thoracic cavity in exhalation Movement bucket handle: Thoracic volume is increased in three planes during inspiration. A) Anteroposterior increase is illustrated with pump handle movement B) Transverse increase is illustrated using bucket with two handles. Lifting handles is like raising right and left ribs at the costovertebral and costosternal joints. C) Vertical dimension is increased by downward pull of diaphragm. Respiration: Mechanism Openings in the diaphragm: There are 3 major openings in the diaphragm which allow 3 very important structures to pass from the thoracic to the abdominal cavity. Inferior vena cava Aorta IVC passes through at T8 level Oesophagu Oesophagus passes through s at T10 level Aorta passes though at T12 level Learn these levels! VENA CAVA = 8 letters OESOPHAGUS= 10 letters Chest XRAY:  Respiratory Anatomy PART 4: Muscles of the thoracic wall Intercostal spaces: Space between ribs is called the intercostal space (numbered according to the rib superior to it) Each intercostal space contains intercostal muscles which help to move the ribs during breathing/ changing the volume within the thoracic cavity during respiration. We have external, internal and innermost intercostal Mm. Intercostal spaces: The intercostal muscles: External intercostal Mm. The most superficial layer of intercostal muscle Run from the inferior border of one rib to the superior border of the rib below Contraction causes ribs to elevate Hands in pockets direction! External intercostal muscles The intercostal muscles: Internal intercostal Mm. The middle layer of intercostal muscle Run from the superior border of one rib to the inferior border of the rib above Contraction draws adjacent ribs nearer together Only function in forced exhalation Internal Hands on chest direction intercostal muscles The intercostal muscles: Innermost intercostal Mm. The deepest layer of intercostal muscle Separated from the other 2 layers of muscle by the neurovascular bundle Same attachment points and action as internal intercostal Innermost intercostal muscles Neurovascular supply to intercostal spaces: Intercostal nerve Intercostal artery Intercostal vein Neurovascular supply to intercostal spaces: Each intercostal space has a separate blood and nervous supply (neurovascular bundle) This neurovascular bundle runs along the inferior aspect of the rib in the costal groove These run anteriorly from the spinal column to the sternum Always in the arrangement (superior -> inferior) Intercostal Vein Intercostal Artery Intercostal Nerve  Accessory muscles of respiration Accessory muscles of Pec minor inhalation removed! Sternocleidomastoid m., pectoralis minor m. & Scalene Mm. Accessory muscles of exhalation External oblique m., internal oblique m., transversus m., rectus abdominis m.  Relaxed inhalation Active/Forced inhalation Diaphragm contracts Diaphragm contracts and external and external intercostals elevate thoracic cavity plus the accessory muscles Sternocleidomastoid m., intercostals elevate pectoralis minor m. & Scalene Mm. elevate thoracic cavity the ribs and sternum Relaxed exhalation Active/Forced exhalation The muscles above relax, this allows the lungs to recoil and The muscles above push air out, internal and innermost intercostals contract, reducing transverse dimension of thoracic cavity. relax, this allows the Plus the accessory muscles External oblique m., lungs to recoil and push internal oblique m., transversus m., rectus abdominis m. depress the ribs and squeeze the air out abdominal cavity Additional resources and suggested videos: Videos/ websites https://teachmeanatomy.info/thorax/ Teach me Anatomy https://www.youtube.com/watch?v=0fVoz4V75_E Osmosis- You tube channel Books/ ebooks Grays Anatomy for students Mcminn’s Atlas of Clinical Anatomy. Good for viewing dissected specimens. Recap Learning outcomes: M1.I.RES.ANA1: Outline the anatomy and histology of the respiratory tract and tracheobronchial tree. M1.I.RES.ANA2: Describe the anatomical features of the lungs, including major neurovascular supply. M1.I.RES.ANA3: Outline the primary and accessory muscles involved in respiration and the mechanism of breathing. M1.I.RES.ANA4: Describe the structures of the thoracic cage and outline the divisions and major contents of the thoracic cavity. M1.I.RES.ANA5: Outline the anatomical positions and relationships of thoracic structures in relation to surface anatomy. Thank you for listening! 