UNIT 5 - RESPIRATORY SYSTEM Flashcards
Respiratory system
Group of organs and tissues used for gas exchange (breathing)
Main respiratory structures (8)
- Nasal cavity (nose
- Mouth
- Pharynx (throat)
- Larynx (voice box)
- Trachea (windpipe)
- Bronchi (large airways)
- Bronchioles (small airways)
- Lungs
Nasal cavity
Provides airway for respiration and moistens/warms the entering air. Filtering of air by hairs the mucous (lysozyme) and contains olfactory receptors
Pharynx
Common passageway for air from nasal and buccal cavity to trachea
Larynx
Common path for food and air to separate controlled by swallow reflex and epiglottis. Also the voice box
Epiglottis
Flap of cartilage that protects the glottis, opening to the trachea
Trachea
Long U shape tube connecting larynx to lungs supported by cartilage rings to put air into and out of the lungs
Thyroid cartilage
2 large plates of cartilage on anterior wall of larynx (adams apple)
Bronchi
Two primary bronchi branch into secondary and tertiary bronchi and takes air into lungs from trachea
Right primary bronchus
Serves the right lung
Left primary bronchus
Serves the left lung
Bronchioles
Further divisions of the tertiary bronchi, the air passage inside the lungs
Branching of bronchial tree in order (9)
- Trachea
- Primary bronchi
- Secondary bronchi
- Bronchioles
- Terminal bronchioles
- Respiratory bronchioles
- Alveolar duct
- Alveolar sac
- Alveoli
Alveoli
Air sacs at the end of bronchioles made of a single layer of squamous epithelial cells surrounded by capillaries where gas exchange occurs and accounts for most of the lungs volume with the largest surface area
How many alveoli do we have
300 million
Alveolar epithelial cells (3)
- Forms nearly continuous lining
- Flat shape
- Main site of gas exchange
Other characteristics of alveolar cells (3)
- Free surfaces contain microvilli secreting surfactant
- Reduce tendency to collapse
- Macrophages
Breathing
Process of getting oxygen into lungs and carbon dioxide out of the lungs
Thoracic cavity
Sealed cavity that houses the lungs and the heart
Rib cage
Surrounds the lungs for protection
Diaphragm
Muscle that helps to inhale and exhale and separates the lungs from the abdomen
Lungs
Major organ in chest to transport oxygen and remove carbon dioxide surrounded by two membranes (pleural membranes)
2 types of pleural membranes:
- Parietal pleura (outer): attached to walls of thoracic cavity and lines inner surface
- Visceral pleura (inner): Covers the lungs
Pleural cavity
Fluid filled space between pleural membranes for lubrication between lung & wall of chest cavity, and to hold the two membranes together ensuring lungs don’t collapse
Inspiration (inhalation)
Process of taking air into lungs, breathing in
Expiration (Exhalation)
Process of removing air from lungs, breathing out
Inhalation process (4)
- Air sucked in lung
- Diaphragm contracts and move down
- External intercostal muscles contract and ribs move upward & outward
- Volume of chest cavity increases, decreasing pressure to -1mm Hg in lungs until 0 (atmospheric pressure)
Exhalation process (4)
- Air is forced out lungs
- Diaphragm relaxes and moves up
- External intercostals relax and ribs move downward & inward
- Volume of chest cavity decreases, increasing pressure to +1mm Hg in lungs until intrapulmonary pressure is 0
Relaxed exhalation
Muscle relaxation
Forced exhalation
Muscle relaxation and contraction of internal intercostal and abdominal muscles to increase thoracic pressure, aiding in the rapid expulsion of air from the lungs
What mechanism controls breathing
Autonomic nervous system (involuntary), however we can control the rate and depth of breathing
Breathing control center
AKA pons and medulla oblongata (also the cardiac centers)
Relationship between breathing control center and cardiac center
The more the heart beats, the more breathing occurs. This is because as the heart beats faster, it uses more energy and sends more oxygen to body
Medulla general function
Sends signals to muscles that control respiration
Medulla (inspiratory center)
Accounts for normal inspiration by sending impulses to inspiratory muscles every few seconds and also activates during exercise
Medulla (expiratory center)
Expiration is typically passive due to relaxation of unstimulated inspiratory muscles, but during exercise it stimulates expiratory muscles to cause forceful exhalation
Pons general function
Control rate or speed of respiration
Pons (pneumotaxic area)
Limits duration of inspiration and increases inspiration rate by sending inhibitory impulses to inspiratory area to prevent lungs from overfilling (eg. Exercise)
Pons (apneustic area)
Increases duration of inspiration and decreases inspiration rate by sending inhibitory impulses to the inspiratory area to lengthen the inspiratory period (eg. Occurs when oxygen levels are lower than normal
Hering-Breuer (inflation) reflex
Keeps the lungs from overinflating with inspired air
Process of inflation reflex (3)
- Forced inspiration stimulates stretch receptors in lining of lung and sends signals to brain
- Signals inhibit inspiratory area and apneustic area
- Inspiration stops and passive expiration occurs
Breathing control centers
Receives incoming information from pons/medulla and information gets interpreted, integrated and if required, response is initiated
Efferent PNS (control of breathing)
Sends a response initiated by breathing control centers to respiratory muscles (intercostal/diaphragm)
Respiratory muscles (control of breathing)
Respond to message from efferent PNS to increase or decrease rate/depth of breathing
Sensory receptors:
Located in major arteries to measure O2 and CO2 concentrations
Afferent PNS
Sends information of O2 and CO2 concentrations to the breathing control center
Chemoreceptors
Special nerve/receptor that sense changes in chemical composition of blood
2 important chemoreceptors
- Central chemoreceptors
- Peripheral chemoreceptors
Central chemoreceptors
Located in the medulla and respond to changes in H+ and CO2 concentrations in CSF
Peripheral chemoreceptors
Located in aortic bodies (aortic arch) and carotid bodies (end of common carotid) and responds to changes in H+, CO2 and O2 concentrations in blood
Mechanism for normal blood concentrations levels
Via negative feedback loop
Negative feedback control for blood concentration (5)
- Stimulus: Some stimulus disrupts homeostasis (Increase in arterial blood PCO2 or decrease in pH/PO2)
- Receptor: Receives stimulus by central chemoreceptors in medulla or peripheral chemoreceptors in aortic and carotid bodies send signal to inspiratory area in medulla oblongata
- Effector: Muscles of inhalation and exhalation contract more forcefully and frequently (hyperventilation)
- Cause decrease in arterial blood PCO2, increase in pH and PO2
- Repeat
Tidal volume
The volume breathed in or out at rest (300-500ml)
Expiratory reserve volume
The maximum volume of air that can be forced out after normal exhalation (1000-1500ml)
Inspiratory reserve volume
The maximum volume of air that can be inhaled after a normal inhalation
Vital capacity
Maximum volume of air that can be exhaled after maximum inhalation (2800-5000ml)
Residual volume
Volume of air remaining in lung after maximum exhalation
Total lung capacity
Total volume of air that lungs are capable of holding
Dead air space
Air that never enters the alveoli but remains in the air passageways (150ml)
How is oxygen transported into the blood
Almost all of O2 (approx. 98%) is carried by an iron containing protein found inside RBC (hemoglobin) and becomes oxyhemoglobin. Each hemoglobin molecule carries 4 O2, 1 RBC contains 300 million hemoglobin = 1200 million O2 molecules per RBC
How does oxygen get from the blood to the cell
O2 enters blood by diffusion and is transported as oxyhemoglobin via circulatory system to capillaries. In the capillaries, O2 is released from hemoglobin and enters cells by diffusion
How does the CO2 get from the cell to the lungs
Approx. 23% of CO2 combines with hemoglobin (carbaminohemoglobin) and CO2 produced by cell enter blood stream via diffusion (7% CO2 dissolved in plasma). The CO2 reacts with H2) to form bicarbonate and leaves blood by diffusion = 1 hemoglobin can only carry 1 CO2 molecule
How much of O2 and CO2 transported by hemoglobin
O2 98.5%, CO2 23%
How much of O2 and CO2 get transported by getting dissolved in plasma
O2 1.5% CO2 7%
How much of O2 and CO2 transport as bicarbonate
O2 N/A, CO2 70%
Euponoea
Normal breathing
Dyspnoea
Difficult breathing (asthma, bronchitis, emphysema)
Tachypnoea
Fast breathing (anxiety, fever in children)
Hyperpnoea
Deep breathing (exercise, high altitudes)
Aponea
Lack of breathing (drugs, trauma)
Hyperventilation
Increased rate or depth of breathing
Causes of hyperventilation (2)
- Respiratory causes: Asthma, emphysema
- Non respiratory causes: Exercise, fever, hyperthyroidism, anxiety (all increased metabolism)
Consequences of hyperventilation (2)
- Hypocapnia (decrease CO2 levels) = alkalosis (increase pH level) = brain dysfunction such as tingling, unconsciousness
- Hypocapnia (decrease CO2 levels = vasodilation = hypotension (lower bp)
Hypoxia
Reduced oxygen supply to body tissues
Internal causes of hypoxia (functional deficit in body systems) (7):
- Hemoglobin deficiencies: Anemia, carbon monoxide poisoning
- Arterial obstruction
- Hypotension
- Edema: Congestive heart failure, renal failure
- Congenital defects: Septal defect, patent ductus arteriosus
- Obstruction of airways: Asthma, bronchitis
- Diffusion deficiency in lungs: Emphysema, pneumonia, pulmonary edema
External causes of hypoxia (low oxygen levels in environment) (3)
- High altitudes
- Overcrowded rooms
- Diving
Physiological consequences of hypoxia (3):
- Cyanosis
- Tachycardia
- Dizziness
Cyanosis
Blueish skin color due to accumulation of non oxygenated blood
Tachycardia
Autonomic nervous system mediated increase in heart rate
Dizziness
Caused by insufficient oxygen supply to brain
