Exam 3 - Respiratory System Flashcards
Structures that compose respiratory system
1) External nose
2) Nasal cavity
3) Pharynx
4) Larynx
5) Trachea
6) Bronchi
7) Lungs
External nose
Encloses for air inspiration. Mouth is not part of respiratory system, even though air can be inspired through it
Nasal cavity
Cleaning, warming, and humidifying chamber for inspired air
Pharynx
Throat; Common passageway for food and air
Larynx
Voice box; Rigid structure helps keep airway constantly open, or patent
Trachea
Windpipe; Air-cleaning tube to funnel inspired air to each lung
Bronchi
Tubes that direct air into lungs
Lungs
Each lung is a labyrinth of air tubes and a complex network of alveoli and capillaries. Air sacs separated by walls of connective tissue containing both collagenous and elastic fibers. Each air sac is the site of gas exchange between air and blood
Simultaneous processes for gas exchange
1) Pulmonary ventilation: Air moving into and out of respiratory passages; Breathing
2) Pulmonary gas exchange: O2 moves out of alveolar air and into the blood. At the same time, CO2 diffuses out of blood and joins air in alveoli
3) Gas transport: CO2 and O2 travel in the blood to and from cells
4) Tissue gas exchange: Gas exchange with the tissues involves the exit of O2 from the blood into cells, while CO2 exits cells to enter the blood
Functions of respiratory system
1) Gas exchange
2) Regulation of blood pH: Can alter pH levels by changing CO2 levels
3) Production of chemical mediators: Lungs produce an enzyme called angiotensin-converting enzyme (ACE), which is an important component of blood pressure regulation
4) Voice production: Air moving past vocal folds makes sound and speech possible
5) Olfaction: Sensation of smell occurs when airborne molecules are drawn into the nasal cavity
6) Protection: Provides protection against some microorganisms by preventing them from entering the body and removing them from respiratory surfaces
Anatomy of external nose
Largest part composed of hyaline cartilage plates. Nasal bones plus extensions of frontal and maxillary bones constitute the bridge
Anatomy of nasal cavity
Begins at nostrils and extends to posterior openings into pharynx, or choanae
Has vibrissae inside the vestibules, or nose hairs
Nasal cavity is separated into left and right halves by wall of tissue called nasal septum
Each side of nasal cavity has three lateral bony ridges called conchae, which increase surface area
Contains olfactory mucosa (located on superior concha) and respiratory mucosa (located on rest of concha)
Purpose of conchae and respiratory mucosa is to filter, warm, and maintain air
Respiratory mucosa
Found on every part of concha but superior concha
Mucus contains lysosomes
Defends against bacteria
When irritated, a sneeze is produced
Purpose is to filter, warm, and maintain air
Functions of nasal cavity
1) Serves as passageway for air
2) Cleans air
3) Humidifies and warms air
4) Contains olfactory epithelium
5) Helps determine voice sound
Paranasal sinuses
Spaces in bone surrounding nasal cavity
Bones: Frontal, sphenoid, ethmoid, and maxillary
Functions:
1) Lighten skull
2) Help warm and moisten air
Sinus headaches occur when paranasal sinuses are inflamed and blocked, leading to pain and pressure in forehead, cheeks, and around eyes
Pharynx
Throat
Common opening of both digestive and respiratory systems
Pharynx receives air from nasal cavity and receives air, food, and drink from oral cavity
Connected inferiorly to respiratory system at larynx and digestive system at esophagus
Has three regions:
1) Nasopharynx
2) Oropharynx
3) Laryngopharynx
Nasopharynx
Superior portion of pharynx
Immediately posterior to oral cavity
Lined with mucous membrane that traps debris
Continuous with middle ear through auditory tubes
Posterior wall houses pharyngeal tonsil, which helps defend body against infection
Oropharynx
Continuation of nasopharynx
Middle portion of pharynx
Air, food, and drink all pass through
Lined with stratified squamous epithelium and protects it from abrasion
Contains two groups of tonsils: Palatine tonsils and lingual tonsils
Laryngopharynx
Continuation of oropharynx
Food and drink pass through to esophagus
Air passes through into larynx
Lined with moist stratified squamous epithelium
Larynx
Voice box
Extends from base of tongue to trachea
Held in place by membranes and muscles superior to hyoid bone
Rigid walls maintain open passageway between pharynx and trachea
Rigidity due to outer casing of nine cartilages connected to one another by muscles and ligaments
Six are paired and three are unpaired
Houses ligaments used for speech and swallowing
Ligaments are found within two separate structures: Vestibular folds and vocal folds
Epithelium covering vestibular and vocal cords are stratified squamous
Rest of larynx lined with pseudostratified ciliated columnar epithelium
Thyroid cartilage
Largest of cartilages
Single shield-shaped piece of cartilage
Adam’s apple
Unpaired cartilage of larynx
Cricoid cartilage
Forms base of larynx
Single piece of cartilage upon which the other cartilages rest
Unpaired cartilage of larynx
Epiglottis
Single piece of cartilage attached to thyroid cartilage and projects superiorly
Freely movable flap
Constructed of elastic cartilage rather than hyaline cartilage
Helps divert food away from trachea opening during swallowing
Unpaired cartilage of larynx
Vestibular folds
False vocal cords
Contain superior pair of ligaments that connect arytenoid cartilages to posterior surface of thyroid cartilage
Structure that ligaments are found within in larynx
Vocal folds
True vocal cords
Contain inferior ligaments
At junction of vocal cords is an opening called the glottis
When vocal cords are inflamed, laryngitis occurs
Structure that ligaments are found within in larynx
Valsalva manuever
Forceful attempt of exhalation against a closed airway
Trachea
Windpipe
Allows air to flow into lungs
Membranous tube attached to larynx
Found behind the esophagus
Consists of dense regular connective tissue and smooth muscle
Reinforced with hyaline cartilage called tracheal rings by preventing collapse
Smooth muscle, trachealis, can narrow diameter of trachea by contracting, which aids in coughing
Mucous membrane lines trachea
Membrane’s goblet cells produce mucus, which traps dust and bacteria
Ciliated epithelium moves mucus into larynx, which enters pharynx, which is then swallowed
Constant, long-term irritation to trachea can cause tracheal epithelium to become moist stratified epithelium that lacks cilia and goblet cells
Bronchi
Trachea divides into two smaller tubes called main bronchi, or primary bronchi, each of which extends to lung
Location where trachea divides into the two main bronchi is a ridge of cartilage called carina
Primary bronchi split into two secondary (lobal) bronchi in the left lung and three secondary bronchi in the right lung, one for each lung lobe
Secondary bronchi split into eight tertiary (segmental) bronchi on the left and ten tertiary bronchi on the right
As gets smaller, less cartilage present and more smooth muscle found in walls
Bronchioles
Result from continued branching of segmental bronchi
Have less cartilage and more smooth muscle
Larger bronchioles are lined with ciliated simple columnar epithelium
Terminal bronchioles arise from bronchioles
Have completed layer of smooth muscle and no cartilage
Lined with simple cuboidal epithelium
Alveoli
Where gas exchange occurs
Sites of pulmonary gas exchange
Small, air-filled chambers where the air and blood come into close contact with each other
Alveolar ducts and alveoli consist of simple squamous epithelium
Respiratory zone
Part of lung where gas exchange occurs, specifically where oxygen is taken up by blood and carbon dioxide is released into air to be exhaled
Macrophages do not accumulate because they move into nearby lymphatic vessels or enter terminal bronchioles, thereby becoming entrapped in mucus that is swept to the pharynx
Order of flow:
Terminal bronchiole
Respiratory bronchioles
Alveolar ducts
Alveolar sacs
Alveoli
Alveolar structure
Two types of cells form alveolar wall:
1) Type I Alveolar Cells/Type I Pneumocytes: thin simple squamous epithelial cells that form 90% of alveolar cells. Most gas exchange takes place through these cells
2) Type II Alveolar Cells/Type II Pneumocytes: Round or cube-shaped secretory cells that produce surfactant, which makes it easier for alveoli to expand during inspiration. Keeps alveoli open
Respiratory Membrane
Formed by alveolar walls and surrounding pulmonary capillaries
Location of pulmonary gas exchange
Extremely thin
Components include:
1) Alveolar cell layer
2) Capillary endothelial layer
3) An interstitial space between alveolar layer and capillary layer
Thoracic wall in pulmonary ventilation
Thoracic wall composed of
1) Thoracic vertebrae
2) Ribs
3) Costal cartilages
4) Sternum
5) Associated muscles
Thoracic cavity is space enclosed by thoracic wall and diaphragm
Diaphragm and other skeletal muscles associated with thoracic wall change thoracic volume during pulmonary ventilation
Provides structure necessary for expansion and contraction of thoracic cavity
Lung structure
Each lung is conical in shape and extends from the diaphragm to a point approximately 2.5xm superior to the clavicle
The portion of the lungs in contact with the diaphragm is the base
Portion of the lungs that extends above the clavicle is the apex
Right lung is larger than left lung
Right lung has three lobes, and left lung has two lobes
Blood supply to lungs
Blood that has passed through lungs and picked up O2 is oxygenated blood
Blood that has passed through tissues and released some of its O2 is called deoxygenated blood
Two blood flow routes to lungs:
1) Blood flow to alveoli: Deoxygenated blood flows through pulmonary arteries to pulmonary capillaries, where it becomes oxygenated and returns to heart through pulmonary veins
2) Blood flow to tissues of bronchial tree: Oxygenated blood flows through bronchial arteries to capillaries, where O2 is released
Lymphatic supply to lungs
Lungs have two lymphatic supplies:
1) Superficial lymphatic vessels: Deep to connective tissue that surrounds each lung, called visceral pleura. These vessels drain lymph from superficial lung tissue and the visceral pleura
2) Deep lymphatic vessels: Follow bronchi. Vessels drain lymph from bronchi and associated connective tissues
No lymphatic vessels located in walls of the alveoli
Both superficial and deep lymphatic vessels exit lung at hilum
Pleura
Two pleural cavities within thoracic cavity
Each houses one lung
Pleural cavities lined with serous membrane
Mediastinum separates the two pleural cavities in the central region
Parietal pleura: Serous membrane that covers inner thoracic wall, the superior surface of the diaphragm, and the mediastinum
At hilum, parietal pleura is continuous with visceral pleura, which covers surface of lung
Pleurisy: Inflammation of pleurae; Result in sharp chest pain when breathing
Pleura in pulmonary ventilation
Facilitates the expansion and contraction of lungs during breathing
During inhalation, pressure within pleural cavity decreases
Pleural fluid within pleural cavity maintains adhesion between pleural layers, ensuring that the lungs expand and contract with the chest wall during breathing movements
Muscles of inspiration in pulmonary ventilation
Muscles of inspiration act to increase the volume of the thoracic cavity and include:
1) Diaphragm: Contraction causes central tendon to move downward. Downward movement facilitated by relaxation of abdominal muscles, which moves abdominal organs out of way. Continued contraction of diaphragm causes it to flatten as lower ribs are elevated
2) External intercostals: Increase thoracic volume by elevating ribs. As ribs are elevated, costal cartilages allow lateral rib movement and lateral expansion of thoracic cavity
3) Pectoralis minor
4) Scalenes
5) Sternocleidomastoid
Quiet breathing: External intercostal muscles contract, elevating ribs and moving sternum
Muscles of expiration in pulmonary ventilation
Muscles of expiration act to decrease thoracic volume by depressing ribs and sternum and include:
1) Internal intercostals
2) Abdominal muscles
Expiration is passive, so thorax wall and lungs spring back into smaller relaxed state, due to removed tension. External intercostals relax and ribs move downward. Contractions of abdominal muscles cause thoracic cavity volume to decrease and push abdominal organs upward into diaphragm, which moves it superiorly
Partial pressure and relationship to the concentration of gases in the body
Higher partial pressure of oxygen in lungs = more oxygen dissolved into blood
Higher partial pressure of carbon dioxide than air in alveoli = higher partial pressure of blood than alveoli
Henry’s Law: Concentration of gas in a liquid is proportional to the partial pressure of that gas;
As partial pressure of oxygen or carbon dioxide increases, the concentration of that gas in the blood will increase
Dalton’s Law: Total pressure of a gas is the sum of the individual pressures of each gas
Partial pressure: Individual pressure of each gas
Pulmonary volumes
Tidal volume: Normal volume of air inspired and expired with each breath. At rest, the quiet pulmonary ventilation results in a tidal volume of approximately 500mL
Inspiratory reserve volume: The amount of air that can be inspired forcefully after a normal inspiration
Expiratory reserve volume: Amount of air that can be forcefully expired after a normal expiration
Residual volume: The volume of air still remaining in the respiratory passages and lungs after the most forceful expiration
Pulmonary capacities
The sum of two or more pulmonary volumes
1) Inspiratory capacity: Tidal volume plus the inspiratory reserve volume. Amount of air a person can inspire maximally after a normal expiration
2) Functional residual capacity: Expiratory reserve volume plus the residual volume. Amount of air remaining in the lungs at the end of a normal expiration
3) Vital capacity: Sum of inspiratory reserve volume, the tidal volume, and the expiratory reserve volume. Maximum volume of air a person can expel from the respiratory tract after a maximum inspiration
4) Total lung capacity: Sum of inspiratory and expiratory reserve volumes plus the tidal volume and residual volume
Relationship between alveolar pressure and the movement of air into and out of lungs
Air pressure in alveoli is intrapulmonary pressure
When person inspires, the intrapulmonary pressure decreases because the alveolar volume has increased
When a person expires, the intrapulmonary pressure increases because the alveolar volume has decreased
Pressure difference between atmospheric pressure and intrapulmonary pressure that results in air movement during one respiratory cycle
760mmHg at sea level
Intrapulmonary pressure fluctuates with breathing and always eventually equalizes with atmospheric pressure
Relationship between lung collapse and surfactant and pleural pressure
Pneumothorax or hemothorax or collapsed lung
Surfactant: Mixture of lipoprotein molecules produced by type II pneumocytes of alveolar epithelium. Reduces surface tension in alveoli. Reduces tendency of lungs to collapse
Pleural pressure: Pressure within pleural cavity. When thoracic wall expands during inspiration, the parietal pleura exerts an outward force on the visceral pleura covering the lungs, and the lungs expand. Pleural pressure pulls the lungs outward and is lower than intra-alveolar pressure. Maintains slightly negative pressure between lungs and chest wall. Keeps lungs expanded by counteracting their tendency to recoil and collapse. Similar to a vacuum seal holding lungs open
Partial pressure gradients for O2 and CO2
Partial pressure gradient for O2 is into blood from alveoli. Once in blood, the partial pressure gradient for O2 is into the body’s cells into the blood
Carbon dioxide moves out of the body’s cells and into the blood. Once in the blood, the partial pressure gradient for CO2 is out of the blood into the alveoli
CO2 is opposite of that for O2
Factors that affect gas movement through the respiratory membrane
Membrane thickness: Increasing the thickness of respiratory membrane decreases the rate of gas diffusion; Diseases increase its thickness, therefore decreasing rate of gas diffusion; Most common cause of increased respiratory membrane thickness is an accumulation of fluid in the alveoli, known as pulmonary edema
Diffusion coefficient of gas: Measure of how easily a gas diffuses through a liquid or tissue
Surface area: More surface area means more gas movement
Fetal hemoglobin vs. Maternal hemoglobin
As fetal blood circulates through the placenta, O2 is released from mother’s blood into the fetal blood, and CO2 is released from fetal blood into the mother’s blood. These forms of hemoglobin are particularly effective for O2 transport because:
1) The concentration of fetal hemoglobin is approximately 50% greater than the concentration of maternal hemoglobin
2) For a given O2 partial pressure, fetal hemoglobin has a higher affinity for O2 than maternal hemoglobin does
Transport of O2 in the blood
O2 transportation: Once O2 diffuses through the respiratory membrane into the blood, it is transported to all cells of the body. Approximately 98.5% of O2 is transported reversibly bound to hemoglobin within red blood cells, and the remaining 1.5% is dissolved in the plasma. Cells use O2 in aerobic cellular respiration to synthesize ATP
Factors affecting hemoglobin’s affinity for O2:
1) Partial pressure of O2: 25% of the O2 bound to hemoglobin is released
2) Temperature: Increased blood temperature decreases affinity for hemoglobin for O2
3) Blood pH: Decreased pH decreases affinity for hemoglobin for O2
4) Partial pressure of CO2: Increased CO2 partial pressure decreases affinity for hemoglobin for O2
5) BPG concentration: Increase in BPG decreases affinity for hemoglobin for O2
6) Cigarette smoking: Increased cigarette smoking increases affinity for hemoglobin for O2
Transport of CO2 in the blood
CO2 transportation: CO2 is formed as a by-product of the breakdown of glucose when cells use O2 to produce ATP. CO2 diffuses out of individual cells into the blood. Blood concentration of CO2 needs to be tightly regulated because too much CO2 in the blood causes blood to become acidic. There are three ways CO2 is transported in the blood:
1) Dissolved in plasma: 7% of CO2 dissolves directly in plasma
2) Bound to hemoglobin: 23% of CO2 is transported bound to hemoglobin. CO2 ability to bind to hemoglobin depends on amount of O2 bound; Smaller amount of O2 bound means greater amount of CO2 able to bind
3) Converted to bicarbonate ion (HCO3): 70% of blood is transported in form of HCO3, dissolved in either cytoplasm of red blood cells or plasma of blood
In lungs:
1) Bicarbonate ions move into red blood cells and bind with hydrogen ions to form carbonic acid
2) Carbonic acid is split by carbonic anhydrase to release carbon dioxide and water
3) CO2 diffuses from blood to alveoli
Forces promoting lung collapse
1) Decreased elasticity of lungs
2) Decreased surface tension of alveolar surfactant; Disrupts surface tension
CO2 and HCO3
CO2 + H2O leads to carbonic acid, or H2CO3
H2CO3 leads to H+ + HCO3
Pathway goes back and forth
CO2 starts in tissues and is removed from lungs
CO2 is diffused to alveoli
Factors that affect O2 and CO2 transport in blood
O2: When levels of O2 partial pressure are low, hemoglobin affinity for O2 stays stable. An increase in blood pH results in an increased affinity of hemoglobin for O2. An increase of temperature decreases O2 tendency to remain bound to hemoglobin
CO2: When levels of O2 partial pressure are low, hemoglobin binds to more CO2. In turn, as more CO2 binds to hemoglobin, the affinity of hemoglobin for O2 decreases. A decrease in blood pH results in a decreased affinity of hemoglobin for CO2. When body temperature increases, more CO2 enters the blood, lowering the pH, which removes excess CO2 from the body
Alveolar ventilation and pulmonary capillary perfusion
Alveolar ventilation: Relationship between ventilation of alveoli and blood flow to the alveoli; Delivery of air to alveoli
Pulmonary capillary perfusion: Flow of blood to alveoli through pulmonary capillaries
Relationship: If perfusion is impaired, the effectiveness of ventilation is reduced, and vice versa
Respiratory areas of brainstem
Brainstem is site of automatic regulation of pulmonary ventilation
Medullary respiratory center in the medulla oblongata consists of two sets of neurons:
1) Ventral respiratory group: Responsible for generating the normal, involuntary rhythm of breathing, called eupnea. Pre-Botzinger complex establishes basic rhythm of pulmonary ventilation. Stimulates the intercostal and abdominal muscles
2) Dorsal respiratory group: Stimulate the diaphragm
Pontine respiratory group found within the pons is involved with switching between inspiration and expiration
Effect of blood pH, CO2, and O2 levels on pulmonary ventilation
O2 partial pressure levels: Small changes in O2 partial pressure levels do not cause changes in respiratory rate or pulmonary ventilation. If partial pressure levels of O2 decrease below 80mmHg, oxygen-carrying capacity of blood is significantly reduced
CO2 partial pressure levels: Small increase in CO2 in bloodstream triggers a large increase in the rate and depth of pulmonary ventilation
Blood pH: Lower pH stimulates respiratory center, resulting in a greater rate and depth of pulmonary ventilation reducing CO2 levels, and blood pH increases to normal levels
Hering-Breuer Reflex
Limits the depth of inspiration and prevents overinflation of lungs. This reflex depends on stretch receptors in the walls of bronchi and bronchioles of the lungs. Reflex is only important in adults when tidal volume is large, such as during exercise. In infants, it plays a role in regulating basic rhythm of pulmonary ventilation and in preventing overinflation of the lungs
Effect of cerebral cortex and limbic system to pulmonary ventilation
Cerebral cortex: Pulmonary ventilation is controlled both voluntarily and involuntarily. For example, during talking or singing, air movement is controlled to produce sounds, as well as to facilitate gas exchange
Limbic system: Emotions acting through limbic system of the brain can affect respiratory center. For example, strong emotions can cause hyperventilation or produce the sobs and gasps of crying
Voluntarily controlled and modified by emotions
Effect of exercise on pulmonary ventilation
During exercise, respiratory rate changes are controlled through various inputs to the respiratory center. Initially, there is a very rapid increase that occurs too quickly to be accounted for by changes in metabolism. After initial immediate increase in respiratory rate, there is a gradual increase that levels off within 4-6 minutes. If exercise intensity is high enough to exceed anaerobic threshold, blood pH drops, which increases pulmonary ventilation. In response to training, athletic performance increases because cardiovascular and respiratory systems become more efficient at delivering O2 and picking up CO2
Vital capacity increases slightly; residual volume decreases slightly
At maximal exercise, tidal volume and minute ventilation increases
Gas exchange between alveoli and blood increases at maximal exercise
Alveolar ventilation increases
Increased cardiovascular efficiency leads to greater blood flow through the lungs
Developmental aspects of respiration
Fetus:
Autonomous respiration at 28 weeks of gestation
Lungs filled with fluid
Gas exchange takes place through placenta
At birth:
Respiratory centers activated
Respiratory rate increases
Old age:
Respiratory efficiency decreases with old age
Hypercapnia vs Hypocapnia
Hypercapnia: Too much CO2
Hypocapnia: Lower than normal CO2
Homeostatic imbalances that reduce lung compliance
1) Deformities of thorax
2) Ossification of costal cartilage
3) Paralysis of intercostal muscles
Effects of aging with pulmonary ventilation
Vital capacity and maximum minute ventilation decrease
Residual volume and dead space increase
Ability to remove mucus from respiratory passageways decreases
Gas exchange across respiratory membrane is reduced
