U8 - respiratory system Flashcards
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Functions of the respiratory system
1. to allow oxygen (O2) from the air into the blood, and carbon dioxide (CO2) from the blood to leave into the air 2. to move air in and out of the lungs (breathing) 3. to produce sound for vocalisation
Respiratory tract
- upper respiratory structures are lined with two cells, one secretes mucus the other is lined with cilia
- airborne particles get stuck in mucus
- cilia beat to move the mucus like a conveyer belt up to the pharynx
- this mechanism filters particles from the air and prevents them from clogging the delicate lung tissue
Nasal cavity
- air enters through the nostrils, passing through hairs which filter out dust
- behind each nostril are two nasal cavities
- bony ridges extend into the cavities, creating
a large surface area - air is warmed and moistened as it passes through the cavities, and sampled for odours
by special receptors
Pharynx and Larynx
- pharynx is between nasal cavities and larynx
- larynx is upper part of the trachea, covered by epiglottis during swallowing
- within larynx are vocal chords, and muscular flaps
Trachea
- connecting larynx to the bronchi is the trachea
- held open by c-shaped cartilage rings
- air flowing down trachea is warmed, moistened, and filtered
Bronchi and bronchioles
- base of trachea divides into left and right bronchi which lead to each side of the lung
- inside the lungs bronchi branch into smaller bronchioles
- bronchi are similar to the trachea in structure,
bronchioles lack the cartilage rings because
they expand and contract with the lungs
Lungs
- respiratory structures after the bronchi are part of the lungs
- lungs fill the chest cavity, except for the heart,
trachea, and esophagus - each lung is surrounded by a double membrane called the pleural membrane
- membranes secrete a lubricating fluid which
sticks the lungs to the inside of the thorax
Alveoli
- each bronchiole ends in a cluster of pockets
called alveoli - walls of the pocket are a thin, moist
membrane only one cell thick - have their own venous and arterial supply,
branches of the pulmonary vessels are covered by a network of capillaries where gas exchange with blood occurs - alveoli are flexible, expanding and contracting
with the lungs - the inner surface secretes a lipid that prevents the alveolus from sticking together with surface tension and collapsing moving around the lungs are special white
blood cells that engulf any particles which make it down into the alveoli - have sensory stretch receptors to tell the nervous system that they are fully expanded
ribs
- walls of the chest are supported by ribs
- ribs are moved by two sheets of muscle
(internal and external) called the intercostal
muscles - external muscle layer causes ribs to move
upward and outward, expanding the chest - internal muscle layer causes ribs to move
downward and inward, contracting the chest
diaghpram
- a dome-shaped sheet of muscle immediately beneath the lungs and above the liver
- contraction of the diaphragm causes it to flatten out and move downward
- the rib cage on the sides and the diaphragm
below define the thoracic cavity
lung diseases
pneumonia – infections of the lung tissue
cause fluid to build up within the alveoli
bronchitis – infections of the bronchi cause
overproduction of mucus and a cough
asthma – bronchioles swell in response to
antigens, restricting air flow into the alveoli
emphysema – alveoli break down due to
chemical damage
Mechanical breathing
- breathing is a (mostly) involuntary process
controlled by the respiratory center of the
medulla oblongata - air moves in and out of the lungs due to
pressure differences created by expanding or
contracting the thoracic cavity - breathing can also be voluntary, e.g. holding
breath, or blowing out candles
Inhalation
- respiratory centre sends a signal to the diaphragm and intercostal muscles:
- diaphragm contracts, moving down
- external intercostals contract, moving the ribs upwards and outwards - these muscular movements increase the height and width of the thoracic cavity, increasing the volume
- the lungs, stuck to the inside of the thorax because of the pleural membranes, expand as well
- as lung volume increases, the pressure of
air inside the lungs decreases - when the pressure in the lungs is lower than
atmospheric pressure, air rushes into the
lungs through the respiratory tract
Exhalation
- lungs fill with air until the stretch receptors in
the alveoli register that they are full - diaphragm and intercostal muscles relax, and the thoracic cavity returns to its original volume
- as lung volume decreases, the air inside
gains pressure - when this pressure is greater than atmospheric pressure, the air rushes out
- exhalation is usually passive in this manner, but it can be forced by contraction of the internal intercostals, which move the ribs down and in
Nervous control of breathing
- breathing rate is controlled by nervous
receptors that respond to chemicals in the
blood - respiratory center of the medulla is sensitive
to the concentrations of CO2 and H+ - when these increase (↑CO2 and lower pH), the center causes breathing rate to increase as well
-two other receptors, the carotid bodies in
the carotid arteries, and the aortic bodies in
the aorta, are sensitive to O2 - when O2 is low, the bodies tell the respiratory
center to increase breathing rate - both of these bodies are partly sensitive to
CO2 and H+ like the respiratory center
respiratory reflexes
sneeze – receptors in the nasal cavity, cause
inhalation followed by forced exhalation
(usually through the nose)
cough – receptors in the pharynx and
trachea, cause inhalation followed by forced
exhalation through the mouth
external respiration
O2 diffuses into blood in pulmonary capillaries and CO2 diffuses out of blood into the alveolus
internal respiration
O2 diffuses into tissue fluid from systemic capillaries and CO2 diffuses into blood from tissue fluid
haemogoblin
- normal hemoglobin protein is called deoxyhemoglobin, or Hb
- Hb has an affinity for O2 at higher pH (about
7.4), and each protein will bind up to four O2
molecules - at higher temperature (38°C) and lower pH
(7.3), Hb loses its affinity for O2 and releases
the bound molecules
Oxygen transport
O2 is taken up by the Hb in red blood cells, forming oxyhemoglobin (HbO2):
Hb + O2 → HbO2
deoxyhemoglobin + oxygen → oxyhemoglobin
Carbon Dioxide Transport
- 60% forms carbonic acid, releasing HCO3-
into the plasma: - H2O + CO2 ↔ H2CO3 ↔ H+ + HCO3-
water + carbon dioxide ↔ carbonic acid ↔
hydrogen ion + bicarbonate ion
( this reaction is catalysed by the enzyme
carbonic anhydrase found in RBCs ) - 30% of the CO2 is taken up by hemoglobin to
form carbaminohemoglobin (HbCO2) - remaining 10% dissolves in the plasma
- hemoglobin combines with excess H+ to form
reduced hemoglobin (HHb), futher buffering
the blood pH
Carbon dioxide transport is converted into what
- 60% converted to HCO3 in plasma
- 30% binds w Hb to form HbC02
- 10% dissolves as C02 gas
External respiration equations
at ↓temperature and ↑pH, HbCO2 releases its
CO2 and picks up O2:
HbCO2 → Hb + CO2 then Hb + O2 → HbO2
(HHb releases H+ and picks up O2)
carbonic anhydrase breaks down H2CO3:
(H+ + HCO3- → H2CO3 → H2O + CO2)
Result: O2 diffuses from alveolus into blood,
CO2 diffuses from blood into alveolus
Temperature and PH of Lungs
pH = 7.4
temperature = 37º
Temperature and pH of tissues
pH = 7.3
temperature = 38º
Oxygen transport equation
O2 is found in air, diffuses into the blood
during external respiration:
100% carried by Hb in RBCs in the form of HbO2
Internal respiration equation
at ↑temperature and ↓pH, HbO2 releases its
O2and picks up CO2:
(HbO2 → Hb + O2 then Hb + CO2 → HbCO2)
carbonic anhydrase creates H2CO3:
(H2O + CO2 → H2CO3 → H+ + HCO3-)
excess H+ combines with Hb to form HHb
Result: O2 diffuses out of blood and into tissue
fluid, while CO2 diffuses out of tissue fluid
and into blood
