Respiratory Anatomy & Physiology (2024) PDF

Respiratory Anatomy & Physiology Zahra B. Macabada, RTRP Introduction & Respiratory Anatomy Learning objectives: Identify, describe and provide functions of the structures of the upper and lower respiratory tract beginning with the nasal cavity and ending at the alveoli. Describe the...

Respiratory Anatomy & Physiology Zahra B. Macabada, RTRP Introduction & Respiratory Anatomy Learning objectives: Identify, describe and provide functions of the structures of the upper and lower respiratory tract beginning with the nasal cavity and ending at the alveoli. Describe the protective mechanism in place to provide immune defense of the airways and types of tissues are found in each area. Describe the structure of the alveoli and the cell types found; include Type I and Type II alveolar cells and alveolar macrophages. Describe the structure and function of the respiratory membrane. What membrane is found around the lungs and how it is innervated. Respiratory System The respiratory system supplies the body with oxygen and removes carbon dioxide. Functions: ○ Ventilation – bring air into the body ○ Filters, humidifies and warms inspired air ○ Respiration – O2 and CO2 Gas exchange between the external environment and the blood ○ Maintains pH homeostasis by removing CO2 ○ Production of sound ○ Olfactory sensation Respiratory System Multiple process must happen to supply the body with oxygen and remove carbon dioxide: ○ Pulmonary Ventilation ○ Diffusion in the lungs (lungs → blood) ○ Gas Transport (blood) ○ Diffusion at the Tissues (blood → tissues) This requires coordination of respiratory (diffusion of gases) and cardiovascular systems (perfusion of blood) Respiratory Anatomical Divisions Upper Respiratory Tract ○ Nasal Cavity ○ Pharynx ○ Larynx Lower Respiratory Tract ○ Trachea ○ Bronchi ○ Lungs Respiratory Functional Divisions Conducting zone – transfers air to and from the lungs ○ Nose, pharynx, larynx, trachea, bronchi, terminal bronchioles Respiratory zone – site of gas exchange ○ Respiratory bronchioles, alveolar ducts, alveoli Respiratory Mucosa The Upper Respiratory Tract is lined by respiratory mucosa – pseudostratified ciliated columnar epithelium (PSCCE) with goblet cells Filters, moistens and warms air ○ Mucus: traps bacteria and foreign debris and moisten airs ○ Cilia – sweeps mucus towards the throat ○ Network of veins – warms passing air “Smokers cough” – smoking paralyzes, damages cilia leading to increased particles in the airways, risk of infection Pulmonary Defense Mechanisms The respiratory system is open to the air and needs protection from contaminants (debris, bacteria) Upper and Lower Airways: ○ Mucus – traps and remove ○ Nasal hairs and nasal conchae (turbinates): trap and remove ○ Cilia: sweeping motion moves debris out of airway ○ Irritant receptors: trigger sneeze, cough reflexes to propel substances out Nostrils, trachea, large airways ( bronchi) Air sacs (Alveoli) ○ Alveolar macrophages: ingest and remove debris and bacteria ○ Surfactant: enhance phagocytosis by macrophages, down- regulate inflammation  Nasal Cavity Nasal cavity ○ External and internal nares – openings to nasal cavity ○ Nasal septum – divides cavity into right and left sides ○ Nasal conchae (turbinates) – increases turbulence of inspired air and exposure to respiratory mucosa Meatus – groove under the nasal conchae ○ Hard and soft palate – floor of nasal cavity, roof of mouth  Paranasal Sinuses Paranasal sinuses – lighten the skull, produce mucus and resonate sound ○ Frontal sinuses ○ Maxillary sinuses ○ Sphenoid sinuses ○ Ethmoid sinuses  Pharynx (Throat) Nasopharynx– superior to the soft palate ○ Pharyngeal tonsil on posterior wall ○ Auditory tube drains into nasopharynx Oropharynx – passageway for food and air ○ Non-keratinized stratified squamous epithelium ○ Palatine tonsils on the lateral walls ○ Lingual tonsil, base of the tongue Laryngopharynx – hyoid bone to the larynx ○ Splits into esophagus (posterior) and larynx  Larynx (Voice box) Larynx– produces sound and prevents food from entering the trachea Muscles that move the larynx, control vocal cords, contribute to swallowing and respiration, prevent aspiration into trachea Cartilage structures protects and prevent collapse of the airway: ○ Epiglottis ○ Thyroid cartilage ○ Cricoid cartilage ○ Arytenoid cartilage (2) ○ Corniculate cartilage (2) ○ Cuneiform cartilage (2)  Epiglottis Epiglottis – spoon shaped elastic cartilage flap that projects from the anterior aspect of the larynx over the glottis The epiglottis keeps food out of the larynx, moved downward to form a lid over the glottis when swallowing  Vocal cords Vocal cords – found within the larynx ○ Vestibular folds – (false vocal cords) mucosal folds superior to true vocal cords Sensitive to touch and will provoke coughing reflex to eject anything that enters the larynx ○ True vocal cords – elastic ligaments attached to the arytenoid and thyroid cartilages Vibrate and produce sound as air is expelled from the lungs Glottis – opening between vocal cords  Trachea (windpipe) Anterior to the esophagus Extends from the larynx to T5 Divides the carina into the right and left primary bronchi ○ Irritant receptors, stimulates cough reflex and airway narrowing to expel irritants Lined with respiratory mucosa C-shaped hyaline cartilage rings – prevent trachea from collapsing ○ Incomplete posteriorly to allow the esophagus to expand anteriorly during swallowing (Trachealis muscle)  Thoracic Cavity and Pleural Cavities Thoracic Cavity: ○ Bound by the rib cage, sternum, thoracic vertebrae ○ Separated from the abdominal cavity by the diaphragm ○ Right and left pleural cavities for right and left lung Right and left pleura ○ Mediastinum for heart, esophagus, trachea, great vessels pericardium Location of Lungs Lungs: Anterior ○ Apex Anterior about 2-3 cm above inner 1/3 of clavicle ○ Base Anterior 6th rib mid-clavicular line to 8th rib midaxillary line Posterior: T10 spinous process Descends with diaphragm on inspiration ○ Oblique fissures T3 spinous process to 6th rib mid-clavicular ○ Right lung horizontal fissures 4th rib anteriorly to 5th rib at mid-axillary line Lung Position in Chest Wall  Pleura Lungs are surrounded by pleura: double layered serous membranes ○ Parietal pleura – lines the walls of thoracic cavity ○ Pleural fluid fills the area between layers to allow gliding and resist separation 18ml, thin layer of fluid Lubricates surfaces to prevent friction Creates surface tension that prevents separation of layers ○ Visceral pleura – covers the lung surface Sensory Innervation of Pleura Parietal pleura has sensation of pain in response to injury or inflammation ○ Mediastinal and diaphragmatic part innervates by phrenic nerve Refers pain to (C3, 4, 5) ○ Intercostal nerves Visceral pleura & lung tissue have visceral sensory reflexes, but no pain sensation ○ Parasympathetic fibers from the vagus nerve (CNX), visceral fibers of (CNX) ○ Sympathetic fibers from the sympathetic trunks ○ NO pain or general sensory fibers. Visceral fibers here are responsible for visceral reflexes, such as cough and stretch stimulus Lungs Large spongy organs composed mostly of elastic CT Found in the thoracic cavity within the right and left pleural cavities Apex – superior point, deep to the clavicle Base – inferior broader portion, rests on diaphragm  Lobes of the Lungs Each lung is divided into lobes by fissures Right lung – three lobes; superior, middle, and inferior; has horizontal and oblique fissure Left lung – two lobes; superior and inferior, separated by the oblique fissure  Lung Hilus & Bronchi Bronchi enter the right and left lung at the hilus (root, medial depression) Left primary bronchus: curved, broad 45 degree angle Right primary bronchus: steep, wide, 20-30 degree angle ○ Most likely to be site of foreign bodies inhaled, aspiration  Bronchi Bronchi – mucosa, smooth muscle, cartilage ○ Primary bronchi – first branch from trachea ○ Secondary (lobar) bronchi – one per lobe ○ Tertiary (segmental) bronchi – each supplies a bronchopulmonary segment Bronchial Tree: Bronchioles Bronchioles – mucosa, smooth muscle, connective tissue (no cartilage) ○ Terminal bronchioles – non- ciliated simple cuboidal ○ Respiratory bronchioles – last branch, alveoli begin Cilia, goblet cells become more sparse and smooth muscle and connective tissue gets thinner as airways get smaller  Alveoli Alveoli – tiny air sacs that are the sites of gas exchange between the lungs and the blood The respiratory zone of the lungs begins when the first alveoli appear on respiratory bronchioles ○ Ventilation: bring air into the lungs ○ Respiration: gas exchange  Alveolar Wall Type I alveolar cells – simple squamous epithelium supported by elastic basement membrane Type II alveolar cells – secrete surfactant ○ Surfactant: lipoproteins ○ Coats the alveoli reduces surface tension to prevent collapse of alveoli ○ Binds to pathogens, cells and contributes to control of inflammation and immunity Alveolar macrophages – (a.k.a dust cells, mononuclear phagocytes) engulf debris and prepare it for removal via lymph nodes  Pulmonary and Bronchial Circulation Pulmonary Circulation: ○ Pulmonary arteries and arterioles: enter the lungs at the hilus, travel along main bronchi and bronchioles From the right side of the heart (Deoxygenated) ○ Pulmonary capillaries: surround the alveolar sacs (Acinus) and alveoli ○ Pulmonary veins: follow the bronchi and leave the lungs at the hilus To left side of the heart (oxygenated)  Pulmonary and Bronchial Circulation Bronchial Circulation: ○ bronchial arteries, arterioles and capillaries: supply the lung parenchyma with oxygen and nutrients From the aorta and intercostal arteries (oxygenated) ○ Bronchial veins: drain the bronchial circuit via systemic veins ○ Anastomoses with pulmonary veins: also drain the bronchial circuit via pulmonary veins The Respiratory Membrane The Respiratory Membrane is the microscopic space where alveoli contact blood capillaries. Site of gas exchange between alveoli and blood “thin for diffusion” ○ Alveoli: simple squamous epithelium ○ Interstitial space: 0.5 um ○ Basement membrane: thin connective tissue fuses capillaries and alveoli ○ Pulmonary capillaries: simple squamous epithelium Ventilation Learning objectives: Define the terms ventilation and respiration. In detail, describe the process of ventilation, include the pressure/volume changes, movement of chest wall and movement of lungs. Explain the significance of the pressure within the pleural space and describe what can happen during pneumothorax. Describe how compliance and airway resistance affect ventilation and “work of breathing”.