Respiratory System Anatomy Lecture Notes PDF

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BIOM2002 Respiratory System Anatomy Lecture Notes 2020...

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RESPIRATORY SYSTEM

1. Thoracic Walls & Diaphragm The thorax - Irregularly shaped cylinder: • Thoracic cavity contains visceral structures • Thoracic wall consists of skeletal and muscular components and is flexible • Functions: − Breathing: Contains lungs & structures that generate movement essential for breathing − Protection: Vital organs (heart, lungs) − Passageway: Structures passing from head and neck to abdomen + Connections between organs of the thorax and other regions of the body -

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Thoracic cavity contains various visceral structures  heart is flanked by the lungs on either side Thorax can be divided into 3 sections - central cavity, pericardial cavity, pleural cavity The pericardial and pleural cavities are the space b/n the 2 layers of serous membrane which surround the heart and lungs respectively.

Bones of the Thoracic Cage A) Thoracic vertebrae (12) B) Ribs (12 pairs) − True ribs attach directly to the sternum (1-7) − False ribs attach via costal cartilage of rib 7 (8-10) − Floating ribs only attached to vertebral column (11 & 12) C) Sternum: Manubrium (superior), Body (central), Xiphoid process (inferior) *Ribs are described as typical or atypical - difference based on specific anatomical features **Differentiating true, false and floating ribs based on their attachments to the sternum -

Thoracic vertebrae match up with the ribs

Thoracic Vertebrae Twelve vertebral bones characterised by additional articular surfaces for the ribs Thoracic vertebra has a heartshaped vertebral body, two small demifacets for articulation with heads of ribs (superior and inferior costal facets)

(These facets can be used to differentiate the thoracic vertebra from other vertebra) • Transverse process has facet for articulation with tubercle of rib • Long, thin, overlapping spinous processes (Project in an inferior direction) -

12 vertebral bones in the thoracic section of the vertebral column and each thoracic vertebra articulates with the ribs

Typical Ribs (3-9): Smooth flat bone which curve around the thorax Anterior end: Rib is continuous with costal cartilage Posterior end - Head: Articulates with thoracic vertebrae  Two articular surfaces for its own and the superior vertebrae  Articular facets on the head of the rib articulate with the vertebra at the body, while the tubercule on the external surface of the rib articulate with the vertebra at the transverse process - Tubercle (on external surface): Articular facet for costal facet of transverse process of same numbered thoracic vertebra Costal surface: Internal surface, Marked with the costal groove External surface: is Palpable Internal surface: smooth & features a costal groove at the inferior aspect of the internal surface - the costal groove is where the neurovascular structures of the thorax travel

Articulation of Typical Rib and Thoracic Vertebra Head of rib articulates with the superior costal facet at the body of the vertebra Tubercule on the external surface of the rib articulates with the transverse costal facet on the transverse process of the thoracic vertebra

Atypical Ribs: only articulate with one vertebra Rib 1: Flat, almost horizontal, Only articulates with T1  Superior surface marked with grooves for arteries and veins Rib 2: Also flat like Rib 1 Rib 10: Only articulates with T10 vertebra Ribs 11 & 12: Only articulate with their own vertebrae  Do not curve around torso  Do not connect to costal cartilage  Project slightly anteriorly

Typical vs Atypical Ribs - Typical: 3-9 --> articulate with their own numeric vertebra as well as the vertebra above it - Atypical: 1-2, 10-12 --> only articulate with their own numeric vertebra - Rib 1: Atypical and true (true meaning it articulates directly with the sternum) - Rib 8: Typical and false rib (false meaning does not articulate with the sternum

Sternum: anteriorly located & contains 3 compartments 1. Manubrium (superior) − Jugular notch on the midline − Articular surfaces for the body of the sternum, the clavicle and ribs (these are lateral on either side of the jugular notch) 2. Body of the sternum: generally located at the articular sites of the facets of the ribs along the superior surface of the sternum − Flat, often marked with sternebrae − Lateral edges marked with articular surfaces for ribs 3. Xiphoid process (inferior) − Various shapes due to anatomical variations − Attaches to body of sternum and 7th rib (joint b/n the body of the sternum and this ovoid process often becomes ossified with age) **There is an uneven surface where the inferior aspect of the manubrium meets the superior aspect of the sternum Joints of Thorax Costovertebral + costotransverse: b/n the ribs & the vertebrae - Multiple articulations, Separate synovial compartments - Costo = rib - Costovertebral joint: b/n facets on the head of rib and this is on body of vertebra - Costotransverse joint: b/n rib and transverse process of vertebra Costochonral joints: b/n the ribs & the costal cartilage (cartilaginous joint – synchondrosis) Sternocostal: b/n the ribs and the sternum - Rib #1 synchondrosis, #2-7 synovial - Costal cartilage articulates with the sternum Interchondral: b/n the costal cartilage of the false ribs - Synovial, reinforced with ligaments Sternal symphyses: Manubriosternal, Xiphisternal

Costovertebral Joints - Head of our rib features two articular facets, a superior and inferior articular facet - We can additionally, see superior and inferior articular facets on the body of our thoracic vertebra • Multifaceted synovial joints • Costovertebral joints:  Head of rib and bodies of adjacent vertebrae  Superior facet of its own numerically equivalent vertebra and inferior facet of the superior vertebra  Synovial joints with 2 compartments & an intra-articular ligament surrounded by a single joint cavity – all contained within one fibrous joint capsule • Costotransverse joints: b/n tubercle of rib and transverse costal facet on the transverse process of its own vertebra   

The inferior articular facet of rib 8 articulates/joins onto the superior costal facet of thoracic vertebra 8 The superior articular facet of rib number 8 articulates with the inferior costal facet on vertebra number 7 So for each typical rib, it articulates with two vertebra - its own as well as the one superior to it

Costovertebral and costotransverse joints

Spans from the superior aspect of rib 8 to the transverse process of rib 7

b/n the rib and vertebral pedicle (b/n the head of the rib and the tubercule) For the costovertebral joints, superior and inferior, they're all contained within a single fibrous joint cavity The radiate ligament of the rib surrounds both of those synovial cavities - the main structure supporting the fibrous joint capsule Joints of costal cartilage Costochondral joints: b/n the ribs and the costal cartilage  Hyaline cartilaginous joints (synchondroses; primary cartilaginous)  Costochondral joints are synchondroses. Costal cartilage is made up of hyaline cartilage and where the hyaline cartilage joins onto the costal surface of the rib, this is a synchondrosis Sternocostal joints: b/n ribs 1-7 and the sternum (Either a synchondrosis or a synovial joint) - Rib 1: Synchondroses (Where the 1st rib meets the manubrium) - Ribs 2-7: Synovial joints (Articulation b/n sternum and costal cartilage)

*Contains: synovial joint with a synovial membrane filled with synovial fluid, a fibrous joint capsule and further reinforced by ligaments **Some of the reinforcing ligaments are the radiate ligaments - different from the ones before - these are sternocostal ligaments Joints of costal cartilage: Interchondral joints: -

Between the costal cartilage of adjacent ribs 7 – 10 (false ribs)

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Synovial joints

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Indirect attachment of ribs 8 - 10 to the sternum (E.g. Rib 8 attaches to the costal cartilage of rib 7, not to the sternum)

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Contribute to a smooth costal margin

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But instead of being b/n 2 bones, these are b/n 2 cartilaginous surfaces

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These joints don't have the same freedom of movement at synovial joint - allow a small amount of movement

Sternal Symphyses: Manubriosternal joint: b/n the manubrium and the body of the sternum • Manubrium is angled posteriorly on the sternum  Sternal angle; Surface anatomy for rib 2  T4/T5 level - bifurcation of trachea, beginning & end of aortic arch & just superior to the pulmonary trunk  Also known as the sternal angle because the manubrium and the sternum meet at a distinct angulation  At the sternal angle, there are 2 articular demi-facets where the second rib articulates  This joint is important for the Xiphisternal joint: b/n the xiphoid & body of the sternum - Often becomes ossified with age

Flexibility of thoracic wall: • Thoracic wall is expandable, important for breathing • Possible because most articulations of the ribs are synovial, allow movement • Posterior attachment of ribs at the vertebra is superior to anterior attachment at the sternum, so entire thoracic wall moves when ribs are elevated  This causes a downward angulation

Superior Thoracic Aperture - Superior thoracic inlet: • The opening at the top of the thoracic cage • Made entirely of skeletal elements  Rib 1, costal cartilage, manubrium, T1 • Oriented obliquely:  Posteriorly at the level of T1  Anteriorly at the level of T2/T3  Posterior aspect is located more superiorly than the anterior aspect • Contains elements of the respiratory, cardiovascular and digestive systems • Structures passing through the thoracic inlet towards the upper limb pass over rib 1 -> Grooves on surface of the 1st rib are visible for the subclavian artery and vein, respectively. These arteries and veins pass b/n the first rib and the overlying clavicle • Structures passing into or from the head travel vertically or out the top of the thoracic head - this includes the common carotid artery and internal jugular vein Respiratory: trachea Cardiovascular: Arteries and veins Digestive system: oesophagus Inferior Thoracic Aperture - Inferior thoracic outlet (aperture) • Large, expandable, consists of bone, cartilage and ligaments − Posterior: Body of T12 − Posterolateral: Ribs 11 & 12 − Anterolateral: Costal cartilage − Anterior: Xiphoid process − the inferior thoracic aperture/thoracic outlet follows the inferior margin of our thorax • Posterior margin inferior to anterior margin  Contrast to the thoracic inlet • Inferior thoracic outlet is Lined/sealed by the diaphragm  Goes more or less around the entire inferior circumference of the thoracic outlet

Inferior Thoracic Aperture  Involves Structures passing through the diaphragm: − Inferior vena cava (T8) − Oesophagus (T10) − Descending Aorta (T12 – aortic hiatus) − 8 – 10 – 12 rule  Structures passing between diaphragm & thoracic wall: Internal thoracic arteries (anteriorly) & Azygous venous system (posteriorly)  Nerves & the diaphragm (Nerves also that pass through the inferior thoracic aperture) − Phrenic nerve: Innervates the diaphragm - C3,4,5 keeps you alive − Vagus nerve: Cranial nerve innervating the guts wandering nerve

The diaphragm  Seals the inferior outlet/aperture of the thorax  Double dome-shaped  Right dome higher due to liver which sits underneath the right dome of the diaphragm  Muscle fibres of the diaphragm radiate from the margins of the outlet to a central tendon in the middle of the diaphragm  Contraction of the diaphragm results in lowering of the height of the dome  flattens it  Central tendon is also attached to the fibrous pericardium of the heart  Openings for structures passing between thorax and abdomen -3 openings in the diaphragm through which the structures pass: Vena Cava, Oesophagus, Aorta  Attachments of the diaphragm ◦ The muscular fibres of the diaphragm converge centrally on the central tendon (white portion in the middle of the diagram) ◦ Diaphragm attaches at xiphoid process, inferior 6 costal cartilages and ribs, to lumbar vertebrae via medial and lateral arcuate ligaments ◦ Crura of diaphragm are musculotendinous bands ◦ Right crus larger longer, arises from L1-L3/4 ◦ Left crus arises from L1- L2/3

Here is the inferior aspect of the diaphragm

Additional anchoring points at the posterior aspect of the diaphragm along the vertebral bodies

This is the posterior aspect of the diaphragm

Diaphragmatic apertures • Caval opening for inferior vena cava  most superior – at the thoracic 8 level (also most anteriorly located of the 3 apertures) • Oesophageal hiatus of oesophagus  Thoracic 10 level • Aortic hiatus for aorta - Not an opening through the diaphragm, instead a gap at posterior edge  Not an opening - rather it is a space b/n the diaphragm at the posterior edge where it meet the vertebra --> bordered on either side by the left and right crus coming down at either side of the aorta

Innervation of diaphragm: Innervated by two phrenic nerves which arise from anterior rami of C3-5 **C3, 4 & 5 keeps the diaphragm alive! A left and right phrenic nerve Emerges as part of the cervical plexus The phrenic nerve is the anterior rami of C3, C4, C5

Muscles of the Thoracic Wall - 3 groups of muscles: 1. Muscles filling the spaces between the ribs  Intercostal spaces 2. Muscles passing between the ribs and the sternum 3. Muscles spanning multiple ribs We only go through the first type Intercostal Muscles • 3 flat mm (muscles) lying in the spaces between adjacent ribs - extend between inferior to superior margins • External intercostals: Most superficial, oblique fibres running anteroinferiorly (Hands in front pockets)  Prominent laterally but deficient medially. This means they extend along the lateral margins of the ribs but are not found much by the costal cartilage at the anterior aspect of the thorax • Internal intercostals: Intermediate layer of mm, Oblique fibres running posteroinferiorly (Hands in back pockets)  Deep of external intercostals - these run in the opposite direction  Prominent medially but deficient laterally  Downward and backward • Innermost intercostals: Deepest layer of intercostals, Oblique fibres running posteroinferiorly - Act in concert with internal intercostals  Run in same direction as internal intercostals -

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Given the angle of the external intercostals, which is anteroinferiorly, when they are shortened/pulled, they pull the ribs upwards and outwards (deep breath) Internal intercostals are involved in forced expiration - breathing out - rib cage pulled downwards and gets smaller

Blood supply of thoracic wall - Primarily via two stem arteries Thoracic aorta: Descending portion of the aorta located within the thorax Internal thoracic artery: Descending aa on the posterior surface of the sternum - Branches of the subclavian aa - Supplies the anterior aspect of the thoracic wall - From the internal thoracic artery, numerous small segmental branches are given off. These are the anterior intercostal arteries, and these provide segmental blood supply along the thorax. Intercostal arteries: - Posterior intercostal aa: Small branches arising directly from the aorta - Provide the segmental blood supply along each rib and its associated muscles Remembering the arch of the aorta departs from the left ventricle of the heart, and it goes upward, leftward and backward, traversing through the thorax very far posterior early. So it lies just on the bodies of thoracic vertebra. The thoracic aorta gives off many posterior intercostal arteries which branch off of the thoracic aorta - Anterior intercostal aa: Small branches arising from the internal thoracic Runs in the costal groove which sits on the inferior aspect of the internal surface of the rib *The anterior and posterior intercostal arteries will often anastomose laterally along thoracic wall Venous Drainage of Thoracic Wall Anterior intercostal veins: Empty into internal thoracic which then empties into brachiocephalic Posterior intercostal veins: Empty into azygos venous system - Azygos vein drains right side - Hemiazygos & accessory hemiazygos drain left side, empty into azygos - Empties into the superior vena cava (entire azygous system) *The Venous drainage follows from the arterial supply. So venous drainage of the thoracic wall is via anterior intercostal veins for the anterior of the thorax. Anterior intercostal veins runs along the posterior aspect of the sternum as well as segmentally along the anterior aspect of the thoracic wall Innervation of the Thoracic Wall Diaphragm: supplied by Phrenic nerve Intercostal muscles: supplied by Intercostal nerves − Arise from T1 to T11 − Motor innervation to mm - Intercostals, subcostals & transverse thoracis mm (Motor innervation arising from the first thoracic level innovates muscles of the first intercostal space. Those arising from the second thoracic level/T2 will serve muscles in the second intercostal space and so on) − Sensory innervation to skin

Here we can see all the neurovascular structures: intercostal vein and nerve sitting in the costal groove on the internal surface of the rib at its inferior aspect Order is vein more superiorly to the artery. Artery is more superior to the nerve

Movements of the Thoracic Wall Many joints of the thoracic wall are synovial joints that allow for movement Muscles of the thoracic wall are involved in generating the movements for breathing. When we take a deep breath in, note that the diameter of thoracic cage increases, our diaphragm flattens out and the ribs are pulled upward and outward, thus increasing the area of our thorax ◦ ◦

Changes in the volume of the thorax forces air in or out of the lungs Muscles of the thoracic wall involved in generating movements for breathing  Anteroposterior and lateral changes in the thoracic wall due to rotation of the ribs on the vertebrae: − External intercostals (Ribs and sternum move upwards - mainly facilitated by the external intercostals) − Bucket handle-type movement (For lateral movements: like a bucket - ribs are attached posteriorly to the vertebra, anteriorly to the sternum and rotate upwards. This movement is facilitated by the external intercostal muscles - during inhalation) − When exhaling, the ribs come back down - bucket handle dropped down

• Vertical changes in the thoracic wall due to contraction of the diaphragm • Any mm in the neck or back attaching to the ribs can act as accessory respiratory mm − Abdominal & neck mm − Forced breathing

Muscles of Respiration:

Diaphragm is the main muscle of inspiration - contraction of the diaphragm pulls the muscle fibres closer together to flatten the dome External intercostals elevate the ribs, pulling the ribs upwards and outwards to increase the space of the thoracic cavity These both allow the lungs to inflate For (forced) expiration: The internal intercostal muscles pull the ribs downwards to collapse the cavity and decrease the space within the thorax, therefore providing forced expiration

2. Upper respiratory tract: Nasal and Oral Cavities, Larynx and Pharynx Upper respiratory system has many functions Nasal Cavity: - Smell - Airway/breathing - Resonance for sound production  resonance chamber - Alters the quality of sound we produce Oral cavity - Eating - Talking - (Airway/breathing) Larynx - Airway/breathing - Phonation - Voice-box  provides a pathway for air to enter & exit - Contains vocal cords to produce sound

Pharynx - Swallowing - Immune tissue - Behind the nasal cavity, oral cavity and larynx

Oesophagus

Nasal cavity - Mucous membrane and features of medial wall

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Medial wall of the nasal cavity: Flat structure Lined by highly specialised & vascular mucous membrane (lines the nasal septum, separating the 2 halves of the nasal cavity) Highly vascular mucous membrane (warms up the air as it p...