Respiratory Muscles PDF

RESPIRATORY MUSCLES 1.1 Muscle Diaphragm Movement Primary muscle of inspiration Flattens when contracted to increase the vertical dimension of the thoracic cavity Not a single muscle o Embryologically derived from two separate hemidiaphragms that fuse during gestation and operates as a single muscle...

RESPIRATORY MUSCLES 1.1 Muscle Diaphragm Movement Primary muscle of inspiration Flattens when contracted to increase the vertical dimension of the thoracic cavity Not a single muscle o Embryologically derived from two separate hemidiaphragms that fuse during gestation and operates as a single muscle o Right hemi-diaphragm is normally slightly higher than the left Muscular portion of the diaphragm has three regions of origin (outlined with broken lines) o Lumbar part ▪ Two crura originate from the bodies of the upper two (left) or three (right) lumbar vertebrae o Costal part ▪ Muscle fibers arise from the inner surfaces of the lower six ribs o Sternal part ▪ Muscle fibers originate from the inner surface of the xiphoid These fibers extend centrally to insert into its central tendon o The central tendon is the structure the diaphragm’s muscle fibers primarily pull upon when they concentrically contract o Central tendon is connected to the pericardial sac that lies on superior side of diaphragm Positions of Diaphragm in Relation to the Thorax o The dome (cupola) of the diaphragm may rise as high as the level of the 4th intercostal space at rest ▪ 4th ICS on right and 5th ICS on the left ▪ Domes descend 2 spaces bilaterally when contracted o Major factors affecting position of diaphragm ▪ Recoil of lungs after expiration causes diaphragm to move higher into thoracic cavity ▪ Force exerted on superior surface of diaphragm due to fluid in lungs Diaphragm does not return to normal resting position ▪ Force exerted on abdominal surface of diaphragm by abdominal viscera when lying down or during pregnancy ▪ Intra-abdominal tension caused by abdominal muscle contractions Standing causes abdominal muscle contractions that push abdominal contents upward on abdominal surface of diaphragm Thorax Accessory Muscles of Respiration Anterior Thoracic Muscles Pectoralis Major and Minor Serratus Anterior Neck Accessory Muscles of Respiration Anterior Scalene Middle Scalene Posterior Scalene Neck Accessory Muscles of Respiration Sternocleidomastoid Superficial Intercostal Muscle Layers of the Thoracic Wall External Intercostal Muscles Middle Intercostal Muscle Layers of the Thoracic Wall Internal Intercostal Muscles Deep Intercostal Muscle Layer of the Thoracic Wall When inspiration is deep and forceful Elevate ribs to expand thoracic cavity Act primarily on the vertebral column Attach to the cervical transverse processes at the first 2 ribs Can assist in inspiration by elevating the first and second ribs Both cervical and brachial plexuses exit between anterior and middle scalenes Phrenic nerve descends vertically on the anterior scalene Named by its bony attachments o Mastoid process of the temporal bone superiorly and inferiorly o Medial clavicle and manubrium Can assist in inspiration by elevating the rib cage Most activity of the intercostal muscles is isometric and supports the intercostal space o They resist paradoxical movement during inspiration Active during inspiration Fibers pass downward/ forward o Elevates ribs Anteriorly replaced with membrane Continuous with external obliques Can maintain eupnea if the diaphragm is unable Contribution to eupnea is position dependent Most activity of the intercostal muscles is isometric and supports the intercostal space o They resist paradoxical movement during inspiration Accessory muscles of active expiration Fibers oriented upward/ backward o Depresses ribs Posteriorly replaced with membrane Continuous with internal obliques Separated from deep layer by nerves and vessels Depresses the ribs facilitating active expiration Anteriorly o The transversus thoracis muscle ▪ Deepest layer of muscle Laterally o The innermost intercostals ▪ Innermost layer → inside of breast plate Posteriorly o The subcostal muscles cross one or two intercostal spaces 1.2 Muscle Genioglossus Soft Palate Tensor Veli Palatini Levator Veli Palatini Palatoglossal Palatopharyngeus Uvular muscles Movement Pharyngeal Muscles (External Circular Layer) Superior Pharyngeal Constrictor Middle Pharyngeal Constrictor Inferior Pharyngeal Constrictor Pharyngeal Muscles (Internal Longitudinal Layer) Stylopharyngeus Palatopharyngeus Salpingopharyngeus Tensor Palatine Genioglossus Hyoid Muscles Extrinsic Muscles of the Larynx (Suprahyoid Muscles) Stylohyoid Geniohyoid Mylohyoid Digastric Stylopharyngeus Extrinsic Muscles of the Larynx (Infrahyoid Muscles) Omohyoid Sternohyoid Sternothyroid Extrinsic Muscles of the Larynx (Infrahyoid Muscles) Thyrohyoid The tongue consists of intrinsic and extrinsic skeletal muscles o Extrinsic muscle supports the tongue in the oral cavity by muscular connections to bones and the pharynx Extrinsic muscle Large fan-shaped muscle Constitutes the bulk of the tongue mass Protrudes the tongue Skeletal muscles tense or elevate soft palate Tensor Veli Palatini o Tenses the soft palate and opens the nasopharynx o Relaxation of this muscle allows soft palate to occlude the airway Soft palate is raised during swallowing to close isthmus of the pharynx between oral and nasal pharynx Soft palate lowers to close isthmus of fauces for air to pass through nose or to maintain substance in oral cavity Fibers extend laterally and circle the pharyngeal wall Constrict walls of pharynx during swallowing Superior Pharyngeal Constrictor Middle Pharyngeal Constrictor o Overlaps the Superior Pharyngeus Inferior Pharyngeal Constrictor o Overlaps the Middle Pharyngeus o Divides into two muscles ▪ Cricopharyngeus Muscle located at C6= esophageal sphincter Elevates (shortens/ widens) larynx and pharynx during swallowing and speaking Lifts larynx against the base of the tongue o Epiglottis is not essential to close the inlet Opens the nasopharynx Opens the oropharynx Opens the hypopharynx/ laryngopharynx Move the larynx as a unit Elevate the hyoid bone and larynx Move the larynx as a unit Contract and depress the hyoid bone Depress the larynx Active in swallowing The only infrahyoid muscle that elevates the larynx*** Intrinsic Muscles of the Larynx (Muscles of the Laryngeal Inlet) Aryepiglottic Oblique Arytenoid Muscles Intrinsic Muscles of the Larynx (Muscles of the Laryngeal Inlet) Thyroepiglottic Muscle Intrinsic Muscles of the Larynx (Muscles of the Vocal Cords) Cricothyroid Intrinsic Muscles of the Larynx (Muscles of the Vocal Cords) Thyrarytenoid Intrinsic Muscles of the Larynx (Muscles of the Vocal Cords) Vocalis Intrinsic Muscles of the Larynx (Muscles of the Vocal Cords) Posterior Cricoarytenoid Intrinsic Muscles of the Larynx (Muscles of the Vocal Cords) Lateral Cricoarytenoid Intrinsic Muscles of the Larynx (Muscles of the Vocal Cords) Interarytenoids 1.3 Muscle Narrow the inlet Widens the inlet Elongates cords Main tensors Shortens cords Main relaxers Shortens cords Relaxes Sole abductors of the vocal cords Contract to widen/ abduct the glottis Primary adductors of the vocal folds Contracts to narrow/ adduct the glottic = transverse and oblique muscle fibers Adducts arytenoid cartilages Closes posterior glottis Movement Trachealis Muscle Airway Smooth Muscle Replaced by smooth muscle sheet that fills posterior gaps of trachea Increases resistance in the airway Posteriorly occludes the esophagus Lines walls of bronchi and bronchioles o + significant amounts of collagen and elastic connective tissue fibers Contraction produces airway constriction Relaxation produces airway dilation