unit 5: respiration Flashcards
Upper respiratory tract
Air is inhaled through the external nares (nostrils)
Air then passes through the nasal cavity
As air enters it passes through shelves called the nasal conchae> filters air
The posterior portion of the nasal cavity is the internal nares this connects to the pharynx
Larynx
Connects the pharynx with the trachea (formed by 9 pieces of cartilage)
Contains vocal cords, glottis and epiglottis
Glottis: an opening between the vocal folds
Epiglottis: flap of elastic cartilage that moves during the swallowing of food; covers the glottis and prevents food from entering the larynx
Trachea
Extends of the larynx towards the lungs
16-20 stacked C-shaped hyaline cartilage connected by dense connective tissue
Cartilaginous rings provide structural support and prevent trachea from collapsing
Lungs
Lungs are separated by the heart and other structures
Each lung is surrounded by two membranes:
-Visceral pleura: adheres to the surfaces of the lungs
-Parietal pleura: lines the walls of the thoracic cavity
Between the two pleura is the pleural cavity which contains a small amount of lubricating fluid
Lower respiratory tract
Primary bronchi divide to form secondary and tertiary bronchi that supply the lobes of each lung
Tertiary bronchi divide into bronchioles that in turn branch again
The smallest of these branches are called terminal bronchioles, which
form pulmonary lobules
Up to this point, all the structures are part of the conducting zone of the respiratory system (no exchange of gases with cells)
In each lobule, there are alveoli, which is a collection of cup-shaped pouches: why do you think they are this shape?
This is the site of gas exchange
Alveoli
Type I alveolar cells:
Gas exchange occurs between these cells and pulmonary capillaries
Type II alveolar cells:
Secrete surfactant: a layer of fluid found between cells and air
Prevents collapsing of the alveoli and allows for easier breathing
Starts being produced by fetal lungs after 26 weeks’ gestation
Macrophages (dust cells)
Gas exchange of alveoli
Each alveolus is surrounded by a layer of simple squamous epithelium
The layers that gas molecules must cross to move from inside the alveoli to the inside of the red blood cell:
alveolar epithelium
endothelium (capillary cell wall)
plasma membrane of red blood cells
Boyles law: volume and pressure and inversely correlated
Gases fill a container completely, unlike liquids
If the volume of a container increases, the pressure of the gases inside will decrease and vice versa
As volume capacity increases pressure decreases
As volume capacity decreases pressure increases
Breathing
Volume of thoracic cavity changes by the action of surrounding muscles
Normal quiet inhalation (inspiration)
Diaphragm and external intercostals contract
This increases the volume of the thoracic cavity
Pressure in the lungs (intrapulmonary pressure) decreases, making it lower than atmospheric pressure
Air rushes into the lungs
During labored inhalation, sternocleidomastoid, scalenes, and pectoralis minor also contract
normal quiet exhalation
Diaphragm and external intercostals relax
This decreases the volume of the thoracic cavity
Pressure in the lungs (intrapulmonary pressure) increases, making it higher than atmospheric pressure
Air is pushed out of the lungs
During forceful exhalation, abdominal and internal intercostal muscles also contract
Nervous control of breathing
Control breathing is found in the medulla oblongata and pons of the brainstem
dorsal respiratory group and ventral respiratory group
Found in the medulla oblongata
DRG contains inspiratory centre
VGR contains expiratory centre
When the DGR is activated, it stimulates the diaphragm and external intercostals to contract
When the DRG is inactive the diaphragm and external intercostals relax leading to quiet exhalation
For forceful exhalation the VGR will be activated by the inspiratory center leading to the contraction of abdominal muscles and internal intercostals
potine respiratory group
Found in the pons
Contains
Pneumotaxic center: resposible for shorter inspirations (ex. During exercise); works by inhibiting inspiratory center
Apneustic center: responsible for longer inspirations (high altitude); works by stimulation inspiratory center
stimuli that changes respiratory rate
Voluntary control
Involuntary control
Receptors are present that detect different things that affect breathing
For example, stretch receptors in the lungs detect the stretching of lungs during inhalation. At a certain point, they will send a message to the brain which will shut down the inspiratory centre to allow exhalation to occur (Hering-Breuer reflex
Chemoreceptors found in the brainstem and also near main blood vessels also monitor levels of CO2, O2 and H+ ions
determining respiration status
Spirometer is an apparatus that can be used to measure the volume of air exchanged during breathing and the respiratory rate
The record is called a spirogram
terms of spirgram
Tidal volume: the volume of air inspired or expired during normal quiet breathing
Expiratory reserve volume: the volume of additional air expired during a forced exhalation
Inspiratory reserve volume: the volume of additional air inspired during a very deep inhalation
vital capacity: all the air that can be exhaled after maximum inspiration (sum of inspiratory reserve, tidal volume, and expiratory reserve) Residual volume: volume of air still present in the lungs after a forced exhalation
Total lung capacity: all the air that can be contained in the lungs (sum of vital capacity and residual volume)
transport of gases: oxygen
Only a small amount of O2 is dissolved in plasma (1.5%)
Most of the O2 is attached to hemoglobin (98.5%)
O2 attached to hemoglobin= oxyhemoglobin
One hemoglobin molecule can bind up to four O2 molecules
O2 must be released by hemoglobin before it can diffuse across membranes
transport of gases: carbon dioxide
7% of CO2 is dissolved in plasma
23% is attached to the globin portion of hemoglobin = carbohemoglobin or carbaminohemoglobin
One hemoglobin molecule can bind to four CO2 molecules
70% is converted into carbonic acid (H2CO3) by an enzyme called carbonic anhydrase, which is found in red blood cells
Carbonic acid can also be broken down to bicarbonate and hydrogen ions
At any point, there are varying concentrations of CO2, H2CO3, HCO3-, and H+
respiratory patterns
Eupnea: normal breathing dyspnea
Dyspnea: difficult breathing (eg. asthma) tachypnea
Tachypnea: fast breathing (eg. anxiety) hyperpnea
Hyperpnea: deep breathing (eg. exercise) apnea
Apnea: breathing stops (eg. choking)
- NOTE: these are patterns and not the same as having a disorder
Hypoxia
Reduced supply of oxygen reaching the tissues
* Internal causes:
Decreased ability of oxygen exchange (e.g., fluid in the lungs)
Decreased hemoglobin or ineffective hemoglobin (anemia)
Obstructions in blood vessels
Hypotension
Edema (too much interstitial fluid)
Congenital heart defects
Obstruction of airways (eg. asthma, bronchitis)
Diffusion deficiency in the lungs (eg. emphysema, pneumonia)
- External causes:
*Low oxygen levels in environment (eg. high altitudes, overcrowded rooms, diving)
Hypoxia physiological consequences
Cyanosis: bluish colour to the skin due to the accumulation of deoxygenated blood
* Tachycardia: autonomic nervous system mediated increased heart rate
* Dizziness: insufficient oxygen supply to the brain
hyperventilation
Increased rate of breathing in which the rate of CO2 breathed out exceeds the body’s production of CO2
- Respiratory causes:
Abnormal functioning of the lungs which include conditions such
as emphysema - Non-respiratory causes:
Increased metabolism (eg. hyperparathyroidism, exercise, fever) * Anxiety
hyperventilation physiological consequences
Drastically reduces the amount of CO2 because person is breathing out CO2 faster than his/her tissues produce it (but does not affect oxygen levels)
Blood pH increases (more alkaline) which can lead to respiratory alkalosis
Vasodilation occurs and blood pressure drops
Can lead to dizziness, brain dysfunction and unconsciousness
