Human Anatomy & Physiology - Respiratory System PDF

HUMAN ANATOMY & PHYSIOLOGY The Respiratory System Hamza Abu Hilail M.Sc. Physiology  Organization and Functions of the Respiratory System  StructurallyConsists of an upper respiratory tract (Nose to Pharynx) lower respiratory tract ( Larynx onwards)  Functionally 1....

HUMAN ANATOMY & PHYSIOLOGY The Respiratory System Hamza Abu Hilail M.Sc. Physiology  Organization and Functions of the Respiratory System  StructurallyConsists of an upper respiratory tract (Nose to Pharynx) lower respiratory tract ( Larynx onwards)  Functionally 1. Conducting portion transports air. includes the nose, nasal cavity, pharynx, larynx, trachea, and progressively smaller airways, from the primary bronchi to the terminal bronchioles 2. The respiratory portion carries out a gas exchange. composed of small airways called respiratory bronchioles and alveolar ducts as well as air sacs called alveoli  Upper Respiratory Tract & Lower Respiratory Tract Upper Respiratory Tract  Organs of the Respiratory system  Nose  Pharynx  Larynx  Trachea  Bronchi  Lungs – alveoli  Respiratory System Functions 1. Supplies the body with oxygen and disposes of carbon dioxide 2. Filters inspired air 3. Produces sound 4. Contains receptors for smell 5. Rids the body of some excess water and heat 6. Helps regulate blood pH  Breathing Breathing (pulmonary ventilation). consists of two cyclic phases: 1. Inhalation, also called inspiration - draws gases into the lungs. 2. Exhalation, also called expiration - forces gases out of the lungs.  Upper Respiratory Tract Composed of the nose and nasal cavity, paranasal sinuses, pharynx (throat) All parts of the conducting portion of the respiratory system.  The nose  Sizevariation due to differences in nasal cartilage  Divided by – nasal septum  Continuous with nasopharynx  Anatomy of the Nasal Cavity  Lateral walls have projections called conchae Increases surface area Increases air turbulence within the nasal cavity  The nasal cavity is separated from the oral cavity by the palate Anterior hard palate (bone) Posterior soft palate (muscle)  Paranasal Sinuses  Cavities within bones surrounding the nasal cavity  Frontal bone  Sphenoid bone  Ethmoid bone  Maxillary bone SINUS  Paranasal Sinuses  Function of the sinuses  Lighten the skull  Act as resonance chambers for speech  Produce mucus that drains into the nasal cavity  Pharynx (Throat)  Muscular passage from the nasal cavity to the larynx  Three regions of the pharynx  Nasopharynx – superior region behind the nasal cavity  Oropharynx – middle region behind mouth  Laryngopharynx – inferior region attached to the larynx  Theoropharynx and laryngopharynx are common passageways for air and food Pharynx (Throat)  Larynx (voice box) Voice box is a cylindrical airway that ends in the trachea Prevents swallowed materials from entering the lower respiratory tract Conducts air into the lower respiratory tract Produces sounds Supported by a framework of nine cartilage pieces held in place by ligaments and muscles  Larynx  Nine (9) c-rings of cartilage form the framework of the larynx  Thyroid cartilage  Cricoid cartilage  Arytenoid cartilages  Cuneiform cartilages  Corniculate cartilages  Epiglottis  Larynx Muscularwalls aid in voice production and the swallowing reflex Glottis – the superior opening of the larynx Epiglottis – prevents food and drink from entering airway when swallowing LARYNX Posterior View of the Larynx  Structure of the larynx  Vocal cords (vocal folds) Vibrate with expelled air to create sound (speech)  Glottis – opening between vocal cords  Sound Production Inferior ligaments are called the vocal folds. Are true vocal cords because they produce sound when air passes between them Superior ligaments are called the vestibular folds. Are false vocal cords because they have no function in sound production, but protect the vocal folds. The tension, length, and position of the vocal folds determine the quality of the sound.  Sound production Intermittent release of exhaled air through the vocal folds Loudness: depends on the force with which air is exhaled through the cords The pharynx, oral cavity, nasal cavity, and paranasal sinuses act as resonating chambers that add quality to the sound Muscles of the face, tongue, and lips help with the enunciation of words Movements of the Vocal Folds Movements of the Vocal Folds  The Larynx  Voice production  Length of the vocal folds changes with pitch  Loudness depends on the force of air across the vocal folds  Intrinsic muscle of larynx 1. Lateral cricoarytenoid  vocal adduction 2. Posterior cricoarytenoid  vocal abduction  Innervation of the larynx  Recurrent laryngeal nerves (branch of Vagus nerve)  Trachea (Windpipe)  Connects larynx with bronchi  Lined with ciliated mucosa  Beat continuously in the opposite direction of incoming air  Expel mucus loaded with dust and other debris away from lungs  Walls are reinforced with C-shaped hyaline cartilage  Trachea At the level of the sternal angle, the trachea bifurcates into two smaller tubes, called the right & left primary bronchi. Each primary bronchus projects laterally toward each lung. The most inferior tracheal cartilage separates the primary bronchi at their origin and forms an internal ridge called the carina.  PRIMARY BRONCUS Right & left primary bronchi  Carina marks line of separation between 2 bronchi  Has cartilaginous C shaped supporting rings  Right primary bronchus – larger diameter than left & descends towards lung in steeper angle  Hilum of lung : Access for entry of pulmonary vessels, nerves, bronchi  Bronchial tree A highly branched system of air-conducting passages that originate from the left and right primary bronchi. Progressivelybranch into narrower tubes as they diverge throughout the lungs before terminating in terminal bronchioles. Incomplete rings of hyaline cartilage support the walls of the primary bronchi to ensure that they remain open.  Bronchial tree Rightprimary bronchus is shorter, wider, and more vertically oriented than the left primary bronchus. Foreign particles are more likely to lodge in the right primary bronchus. Theprimary bronchi enter the hilus of each lung together with the pulmonary vessels, lymphatic vessels, and nerves. Each primary bronchus branches into several secondary bronchi (or lobar bronchi).  Bronchial tree The left lung has two secondary bronchi. The right lung has three secondary bronchi. They further divide into tertiary bronchi. Each tertiary bronchus is called a segmental bronchus because it supplies a part of the lung called a bronchopulmonary segment. Bronchopulmonary Segments Bronchopulmonary Segments  Bronchial Tree Secondary bronchi tertiary bronchi bronchioles terminal bronchioles With successive branching, the amount of cartilage decreases and the number of smooth muscles increases, this allows for variation in airway diameter During exertion and when sympathetic division active  bronchodilation Mediators of allergic reactions like histamine  bronchoconstriction The tree  Gross Anatomy of the Lungs Each lung has a conical shape. Its wide, concave base rests upon the muscular diaphragm. Its superior region called the apex projects superiorly to a point that is slightly superior and posterior to the clavicle. Both lungs are bordered by the thoracic wall anteriorly, laterally, and posteriorly, and supported by the rib cage. Gross Anatomy of the Lungs Toward the midline, the mediastinum separates the lungs from each other. Mediastinum, the anatomic region located between the lungs that contains all the principal tissues and organs of the chest except the lung The relatively broad, rounded surface in contact with the thoracic wall is called the costal surface of the lung.  Lungs Left lung  Divided into 2 lobes by oblique fissure  Smaller than the right lung  Cardiac notch accommodates the heart Right lung  Divided into 3 lobes by oblique and horizontal fissure  Located more superiorly in the body due to liver on right side  Pleura and Pleural Cavities  Theouter surface of each lung and the adjacent internal thoracic wall are lined by a serous membrane called pleura. The visceral pleura tightly covers the outer surface of each lung. While the internal thoracic walls, the lateral surfaces of the mediastinum, and the superior surface of the diaphragm are lined by the parietal pleura.  Theparietal and visceral pleural layers are continuous at the hilus of each lung.  Pleural Cavities The potential space between the serous membrane layers is a pleural cavity.  The pleural membranes produce a thin, serous pleural fluid that circulates in the pleural cavity and acts as a lubricant, ensuring minimal friction during breathing.  Pleural effusion – pleuritis with too much fluid  Blood supply of Lungs 1. Pulmonary circulation 2. Bronchial circulation – bronchial arteries supply oxygenated blood to lungs, bronchial veins carry away deoxygenated blood from lung tissue  superior vena cava  Bronchioles  Smallest branches of the bronchi  Respiratory Bronchioles, Alveolar Ducts, and Alveoli  Lungs contain small saccular out pockets called alveoli. They have a thin wall specialized to promote diffusion of gases between the alveolus and the blood in the pulmonary capillaries.  Gas exchange can take place in the respiratory bronchioles, alveolar ducts & alveoli, each lung contains approximately 300 to 400 million alveoli.  Thespongy nature of the lung is due to the packing of millions of alveoli together. Respiratory Membrane (Air-Blood Barrier)  Cells in Alveolus 1. Type I cells : simple squamous cells forming lining 2. Type II cells : or septal cells secrete surfactant Surfactant: substance lowers surface tension, which keeps the alveoli from collapsing after exhalation and makes breathing easy 3. Alveolar macrophages Anatomy of Alveoli and the Respiratory Membrane Central chemoreceptors regulate PH  Breathing Mechanisms Breathing Mechanisms – physical laws The Gas law states that gas molecules always diffuse from a higher-pressure area to a lower- pressure area. Boyle's law states that pressure and volume are inversely related (with the temperature remaining constant), where pressure will increase in a smaller volume of gases, and pressure decreases in a larger volume of gases  Inspiration (Inhalation) An active process where nerve impulses from medulla oblongata cause the contraction of the diaphragm and external intercostal muscles. When these muscles contract, thoracic volume ↑ and the pressure within the lung ↓ (interalveolar pressure) When interalveolar pressure falls below the atmospheric pressure (758 mmHg versus 760 mmHg, respectively), the gases move from the environment into the lungs.  Expiration (exhalation) ▪ A passive process where elastic tissues of the lungs and diaphragm recoil to their original position. ▪ The diaphragm and external intercostal muscles relax and recoil, and thoracic volume decreases, raising intra-alveolar pressure ▪ When interalveolar pressure rises above the atmospheric pressure (762 mmHg versus 760 mmHg, respectively), gases move from the lungs into the environment Inspiration vs. Expiration  Pulmonary Ventilation - Inspiration Pulmonary ventilation is the mechanism by which air is exchanged between the atmosphere and the alveoli. Air is exchanged due to the expansion and contraction of the lungs. Contraction of the diaphragm pulls down, enlarging the intrapleural cavity. Elevation of the ribs also expands the intrapleural cavity. These factors decrease the intrapleural cavity pressure: thus, air flows into the lungs (inspiration).  Pulmonary ventilation -Expiration During expiration the diaphragm relaxes the ribs are pulled down. This increases the intrapleural cavity pressure. This results in the movement of air out of the lungs. Normal quiet breathing is accomplished entirely by the movement of the diaphragm. In the "normal sized" person, about 6 liters of gas per minute move in and out of the lungs. Ventilation can increase up to almost 100 liters per minute during maximal exercise.  Control of breathing Four major factors affect normal breathing: 1.Stretching in the lungs and thoracic walls 2.O2 level in the blood 3.CO2 level in the blood 4.H+ levels in the blood.  Control of breathing Low blood PO2: increase alveolar ventilation (peripheral chemoreceptors in the carotid bodies & aortic bodies detect low O2 concentrations). High blood Pco2: increase alveolar ventilation. High CSF, H+ ion concentration: increase breathing rate and alveolar ventilation. CO2 combines with water to form carbonic acid (H₂CO₃), which in turn, releases H+ ions in CSF.  External & Internal Respiration External Respiration: Occurs in the lungs to oxygenate the blood and remove CO2 from the deoxygenated blood. O2 diffuses from the alveoli into capillaries, while CO2 diffuses from the capillaries into alveoli. Internal respiration (tissue respiration): Occurs in the body tissues to provide O2 to tissue cells and remove CO2 from the cells. Gas Exchange at the Alveoli & Cells Pulmonary vs. Systemic Capillaries Pulmonary Capillaries: Alveolar Po2 = 104 mmHg Pulmonary capillaries Po2 = 40 mmHg Result: O2 enters capillaries Alveolar Pco2 = 40 mmHg Pulmonary capillaries Pco2 = 45 mmHg Result: Co2 enters alveoli Systemic capillaries: Systemic capillaries Po2 = 104 mmHg Tissues Po2 = >40 mmHg Result: O2 enters tissues Systemic capillaries Pco2 = 40 mmHg Tissues Pco2 = < 45 mmHg Result: Co2 enters capillary  Muscles that ASSIST with respiration The scalenes muscle helps increase thoracic cavity dimensions by elevating the first and second ribs during forced inhalation. The ribs elevate upon contraction of the external intercostals, thereby increasing the transverse dimensions of the thoracic cavity during inhalation. Contraction of the internal intercostals depresses the ribs, but this only occurs during forced exhalation.  Muscles that ASSIST with respiration Other accessory muscles assist with respiratory activities. 1. The pectoralis minor, serratus anterior, and sternocleidomastoid help with forced inhalation 2. while the abdominal muscles(external and internal obliques, transversus abdominis, and rectus abdominis) assist in active exhalation  Ventilation Control by Respiratory Centers of the Brain The trachea, bronchial tree, and lungs are innervated by the Autonomic nervous system. The involuntary, rhythmic activities that deliver and remove respiratory gases are regulated in the brainstem through the medulla oblongata and pons.  Neural Control of Ventilation The most important respiratory centers : (DRG) dorsal respiratory group, formerly called the inspiratory area (VRG) ventral respiratory group, Formerly called the expiratory area Located in reticular formation in the medulla oblongata Inspiratory area: establish the basic rhythm every 2 seconds to phrenic and intercostal nerve Expiratory area: work just in forceful breathing, take orders from the inspiratory area, and give the order to assist exhalation of muscle  Neural Regulation of Respiration Activity of respiratory muscles is transmitted to the brain by the phrenic and intercostal nerves Neural centers that control rate and depth are located in the medulla The pons appears to smooth out the respiratory rate Normal respiratory rate (eupnea) is 12–15 respirations per minute Hypernia is increased respiratory rate often due to extra oxygen needs  Neural Control of Ventilation Respiratory centre Generates baseline respiration rate In the reticular formation of the medulla oblongata Chemoreceptors Sensitive to rising and falling oxygen levels 1.Central chemoreceptors: located in the medulla oblongata, sensitive to change in acidity H+ and Pco2 2.Peripheral chemoreceptors: sensitive to change in H+, Po2, and Pco2 Aortic bodies: return by the vagus nerve (X) Carotid bodies: return glossopharyngeal nerve (IX) Location of Peripheral Chemoreceptors Neural Regulation of Respiration