Lecture 23: The Respiratory System Lecturer: Dr. Barjis Room: P307 Phone: (718) 260-5285 E-Mail: ibarjis@citytech.cuny.edu

Learning Objectives Describe the primary functions of the respiratory system Identify the organs of the respiratory system and describe their functions Define and compare the processes of external and internal respiration

Learning Objectives Summarize the physical principles governing the movement of air into the lungs and the diffusion of gases into the blood Explain the important structural features of the respiratory membrane Describe how oxygen and carbon dioxide are picked up, transported and released in the blood

Functions of the respiratory system Gas exchange between air and circulating blood Moving air from the exchange surface of the lungs Protection of respiratory surfaces Production of sound Provision for olfactory sensations

Organization of the respiratory system Respiratory system is divided into upper and lower respiratory systems. Upper respiratory system Nose, nasal cavity, paranasal sinuses, pharynx Lower respiratory system Larynx, trachea, bronchi, bronchioles, alveoli

The Components of the Respiratory System The hard palate separates the nasal cavity from the oral cavity

The Respiratory tract Conducting passageways carrying air to and from the alveoli Upper respiratory passages filter, warm and humidify incoming air Lower passageways include delicate conduction passages and alveolar exchange surfaces

The Nose, Nasal Cavity, and Pharynx Nasal conchae creates turbulence as air passes through the nasal cavity. Turbulence makes the air bounce, thus small microorganisms will be trapped in the mucus

The pharynx Shared by the digestive and respiratory systems Divided into three sections: Nasopharynx – superior portion Oropharynx – continuous with the oral cavity The portion of pharynx that receives oth air and food Laryngopharynx

The larynx Receives inhaled air from pharynx through glottis Larynx protects the glottis Food/drink that touch the vestibular or vocal folds trigger coughing reflex Larynx consist of 3 large cartilages Thyroid – is largest laryngeal cartilage Cricoid – ring shaped cartilage Epiglottis – is an elastic cartilage that prevents food and water from entering the larynx

The Larynx

The Larynx Sound production Air passing through the glottis vibrates the vocal folds producing sound waves Pitch depends on conditions of vocal folds Diameter Length Tension

The Glottis

The laryngeal musculature The Larynx The laryngeal musculature Muscles of the neck and pharynx position and stabilize the larynx When swallowing these muscles Elevate the larynx Bend the epiglottis over the glottis Intrinsic muscles control tension on the vocal folds and open the glottis

The trachea A tough, flexible tube running from the larynx to the bronchi Held open by C-shaped tracheal cartilages

The Anatomy of the Trachea

The bronchi Trachea branches in the mediastinum into right and left bronchi Bronchi enter the lungs at the hilus The two primary bronchi branches further to secondary bronchi as they enter the lungs Secondary bronchi branches into tertiary bronchi and tertiary bronchi branches into brancheoles within the lung As they branch, amount of cartilage in their wall reduces and amount of smooth muscle increases

Lobes and surfaces of the lungs Lobes of the lung are separated by fissures Right lung has three lobes Left lung has two lobes

The Gross Anatomy of the Lungs

The bronchial tree System of tubes formed from the primary bronchi and their branches Primary bronchi branch into secondary bronchi Secondary bronchus goes to each lobe of the lungs Secondary bronchi branch into tertiary bronchi Tertiary bronchi supply air to a single bronchopulmonary segment

The Bronchi and Lobules of the Lung

The Bronchi and Lobules of the Lung

The bronchioles Each tertiary bronchus branches several times and give rise to bronchioles Bronchioles branches into terminal bronchioles where each terminal brancheole: Delivers air to a single pulmonary lobule Terminal bronchiole becomes respiratory bronchioles

Summary of air flow Broncheoles Nasal cavity Pharynx Nasopharynx Oropharynx Laryngopharynx Larynx Trachea Bronchi Primary Bronchi Secondary Bronchi Tertiary Bronchi Broncheoles Terminal Broncheoles Respiratory Broncheoles Alveoli –is the only site of gas exchange

Cells of the respiratory membrane include Septal cells Scattered in respiratory membrane Septal cells produce surfactant Surfacant prevents the alveoli from colapsing Alveolar Macrophage Macrophages patrol epithelium and engulf foreign particles Animation: Respiratory Structures (see tutorial)

Alveolar Organization

The pleural cavities and pleural membranes Each lung is covered by one pleura Pleura is a serous membrane lining the pleural cavity Parietal pleura - covers the inner surface of thoracic wall Visceral Pleura - covers the surface of the lungs Pleural fluid – fills and lubricates the space between the pleura

Respiratory physiology is a series of integrated processes Internal respiration Exchange of gases between interstitial fluid and cells or between the blood and interstitial fluid or capillaries and interstitial fluid. Oxygen diffuses from the capillaries to the interstitial fluid and from the interstitial fluid to the cell Carbon dioxide diffuses from the cell to the interstitial fluid and from the interstitial fluid to the capillaries. External respiration Exchange of gases between interstitial fluid and the external environment i.e. gas exchange between circulating blood and alveoli. Oxygen diffuses from the alveoli to the capillaries Carbon dioxide diffuses from the capillaries to the alveoli.

Respiratory physiology is a series of integrated processes The steps of external respiration include: Pulmonary ventilation Gas diffusion Transport of oxygen and carbon dioxide Oxygen bounds to hemoglobin and is transported from the lungs to the cells. Carbon dioxide is transported in the form of bicarbonate ions from the cell to the lungs Reactions are completely reversible

An Overview of Respiratory Processes and Partial Pressures in Respiration Animation: Respiratory Processes and Partial Pressures in Respiration (see tutorial)

An Overview of Key Steps in Respiration

Pulmonary Ventilation The physical movement of air into and out of the lungs Movement of air Relationship between intrapulmonary pressure and atmospheric pressure determines direction of air flow Boyle’s Law Boyle’s law state that pressure and volume has inverse relationship i.e. the higher the volume the lower the pressure, and the lesser the volume the higher the pressure Volume depends on movement of diaphragm and ribs

Mechanisms of Pulmonary Ventilation

Respiratory cycle Respiratory cycle is single cycle of inhalation and exhalation Amount of air moved in one cycle is called tidal volume Animation: Pulmonary Ventilation (see tutorial)

Mechanisms of breathing Quiet breathing (eupnea) In quite breathing diaphragm and external and internal intercostals muscles are required (work) Forced breathing (hyperpnea) In forced breathing in addition to the diaphragm and intercostals muscles accessory muscles are needed

Respiratory volumes Tidal Volume (VT) Amount of air inhaled or exhaled with each breath Vital capacity Tidal volume plus expiratory and inspiratory reserve volumes Residual volume Air left in lungs after maximum exhalation

Respiratory Volumes and Capacities

Gas Exchange The gas laws Daltons Law and partial pressure Individual gases in a mixture exert pressure proportional to their abundance In a mixture of gases like air the total pressure is the sum of pressure by the individual gas Diffusion between liquid and gases (Henry’s law) The amount of gas in solution is directly proportional to their partial pressure

Henry’s Law and the Relationship between Solubility and Pressure

Henry’s Law and the Relationship between Solubility and Pressure

Diffusion and respiratory function Gas exchange across respiratory membrane is efficient due to: Differences in partial pressure Small diffusion distance Lipid-soluble gases Large surface area of all alveoli Coordination of blood flow and airflow

Oxygen transport Carried mainly by RBCs, bound to hemoglobin The amount of oxygen carried by hemoglobin depends upon: PO2 pH temperature BPG Fetal hemoglobin has a higher O2 affinity than adult hemoglobin

The Oxygen-Hemoglobin Saturation Curve

The Effect of pH and Temperature on Hemoglobin Saturation

A Functional Comparison of Fetal and Adult Hemoglobin

Carbon dioxide transport 7% dissolved in plasma 70% carried as carbonic acid 23% bound to hemoglobin carbaminohemoglobin

Carbon Dioxide Transport in Blood

A Summary of the Primary Gas Transport Mechanisms

Respiratory reflexes Respiratory centers are modified by sensory information including Chemoreceptor reflexes Level of carbon dioxide Baroreceptors reflexes Hering-Breuer reflexes Prevents overinflation Protective reflexes

You should now be familiar with: The primary functions of the respiratory system The organs of the respiratory system and their functions The processes of external and internal respiration The physical principles governing the movement of air into the lungs and the diffusion of gases into the blood The important structural features of the respiratory membrane How oxygen and carbon dioxide are picked up, transported and released in the blood