cgier 27 Flashcards
the exchange of gasses between an organism and its environment is
respiration
the functions of respiration
- supply 02 to the body
- removes co2 from the body
- aka gas exchange
is highly effective in producing ATP from glucose but requires steady 02 levels
aerobic respiration
warm blooded animals aka homeotherms have
high 02 requirements and most animals need continuous supply of 02 for cellular respiration .
Level of respiration = oxygen requirement = index of metabolic activity
the functions of respiratory system
- helps u breath in and out
- talk and smell
- warms and moistens air to body temp and humidity level
- protects ur airways
- gas exchange
Three distinct stages of gas exchange
1- external respiration: transfers 02 into the blood from atompsthere
2- gas transport : transports 02 and c02 in the blood
3- internal respiration: cellular respiration 02 uptake and c02 production within the cells
respiratory pathway of external respiration
nostrils -> nasal cavity -> pharynx -> larynx -> trachea -> bronchi-> bronchioles -> alveoli
the upper respiratory tract includes
- Nasal Passages, Eustachian Tubes, Middle ear and mastoid cavities
- pharynx and larnyx
- epiglottis
The back of the nasal cavities is continuous with
throat aka pharnyx
An opening in the floor of the pharynx leads to
larnyx
contains vocal cords
larynx
larynx contains cartilage embedded in its wall to
prevents the larynx from collapsing
— flap that automatically closes off the larynx during swallowing so that food and liquid enter the oesophagus rather than the lower airway.
epiglottis
the most common form of infections in the world
respiratory tract infections
- usually viral but can be bacterial
- mild symptoms but can be severe in children, elderly, immuncompromised patients.
- common cold, sore throat, earache, blocked sinuses, nasal congestion
is a single tube which branches into left and right bronchus ( one in each lungs )
trachea , surrounded by rings of hyaline cartilage which reinforces the tube walls
the lungs they branch extensively into smaller (secondary)
- bronchi and then many bronchioles
-Ciliated epithelium in trachea, bronchi, bronchioles.
Cilia beat upwards pushing the mucus secreted by the goblet cells assisted by the cough reflex
Mucociliary Escalator
Bronchioles lead into
bronchiolar/alveolarducts.
these ends in alveoli which are site of 02 and c02 exchange in the bloodstream
Gases diffuse freely through the walls of the —- and into the — that surround
alveolus into the capillaries
Alveolar wall contains 2 major cell types
Alveolar epithelial cells – Type I and Type II (also called pneumocytes)
1. type 1: squamous and extremely thin cover 95% alveolar surface involved in gas exchnage
2. type 2: granular and roughly cuboidal cover 5% secretes pulmonary surfactant
a phospholipid acts as detergent and reduces surface tension to prevent alveoli from collapsing
surfactant
surface tension is produced by the
lining of the lungs , surface area is 480 million in alveoli in 2 lungs 70-80 m in adults
Some premature babies born under 32 weeks gestation do not secrete
surfactant bc their lungs have immature or insuffienct type 2 penumocyte. This leads to difficulty in lung expansion and alveoli begins to collapse ( atelectasis ) Requires; immediate treatment, mechanical ventilation, oxygen throat, synthetic or natural surfactant
Large, spongy, elastic organs within the
thoracic cavity ( left and right lungs , right lung has 3 lobes and left has 2 lobes bc left lung is smaller to give space for the heart) . These lobes are divided into segments
is composed of anterior sternum, posterior spinal column, rib cage (12 pairs of ribs), diaphragm
thoracic cage
The lungs are covered by a —
visceral pleura
—in contact with the inner wall of the thorax; —- in between
parietal pleura , pleaural cavity
a film fluid in the —- provided — for the lungs and the chest wall
pleaural cavity, lubrication
are serous membranes (secrete serous mucous). Can become infected resulting in pleurisy
pleural walls
has a negative atmospheric pressure of —- mm Hg. This acts like a suction to keep the lungs —-
Intrapleural space , -4 , inflated
Pulmonary ventilation dependent on 3 pressures:
- Atmospheric pressure
- Intra alveolar pressure – will always equalise to atmospheric pressure
- Intra pleural pressure – always negative
( the difference between 2 and 3 is the difference in pressure that drives the air flow, air flows from high to low pressure)
- Atmospheric pressure >intra pulmonary pressure >intra pleural pressure
In intrapulmonary pressure
during inspiration the pressure inside of the lungs —- as the volume — and pressure — during expiration
decreases, increases, increases
In intrapleaural pressure , pleaural cavity pressure becomes more — when chest well expands during — and returns to initial value as the chest wall recoils
negative , inspiration
during each breath, the pressure gradient move
0.5 litres of air into and out of the lungs
Why is intrapleural pressure negative?
necessary to prevent lung collapse due to surface tension of the alveolar fluid and the elastic fibres.
Pneumothorax
collapsed lung, results from loss of negative intrapleural pressure.
breathing is brought by —– and — the volume of — by means of —- — and —-
increasing and decrease
volume of the thorax
respiratory muscles, intercostals, diaphragm
taking air into ur lungs is
inhaling/inspiration
- active process
- volume increases and air pressure( intrapulmonary pressure) in lungs decreases
- stimulating the diaphragm so it contracts becomes less flat and lowered.
-Also involves the intercostal muscles - short muscles that lie between the ribs.
-External intercostal muscles contract as diaphragm is lowered-raising rib cage and pushing sternum outward
letting air out of the lungs is
- exhalation/ expiration
- passive no energy needed
- diaphragm and intercostal releases chest falls inwards
- rose of intrapulmonary pressure and reduction of volume
-Can be made active (uses energy) by contracting the muscles of the abdominal wall and the internal intercostal muscles – e.g. in a forced exhalation; and during vigorous exercise - Abdominal muscles pull ribs downward and force abdominal contents upward
- Internal intercostal muscles contract pulling ribs down = lung volume reduced
breathing is controlled by
-respiratory centre of the brain stem
-3 groups of neurons located within the medulla oblongata and pons of the hind- brain
Medulla
* Dorsal respiratory group- stimulates
inspiratory movements
medulla
* Ventral respiratory group- stimulates
expiratory movement
Pons
* Pontine respiratory group – divided into
two areas
– Pneumotaxiccenter–
continuously sends inhibitory signals to the inspiratory center of the medulla, controls the length of each breath
– Apneusticcenter-stimulatesthe inspiratory neurons of the dorsal and ventral groups
Respiratory rate and depth of inspiration controlled by
Medulla and Pons in response to specific stimuli . Concentration of the chemicals is controlled by chemoreceptors
Central Chemoreceptors (in medulla) near inspiratory area is sensitive to
CO2
and H+ concentration in blood
Increased blood CO2 and H+ levels causes excitation of the inspiratory
area.
Why? – to increase respiratory rate and expel CO2
Low levels CO2 - decrease respiratory rate
Peripheral Chemoreceptors in the Carotid artery and Aortic arch sensitive to
increased CO2 and H+ ions concentration and a drop in oxygen
Basic breathing rhythm generated by
neuronal oscillatory (i.e. on/off) circuit in inspiratory area
Inspiratory circuit fires 2 seconds
→ nerve impulse → diaphragm and external intercostal muscles contract → inspiration
Inspiratory circuit dormant 3 seconds
→ expiratory area dormant → expiration by default, becomes active in forceful breathing
- 12 breaths/min quiet breathing,
more info
But, during exercise expiratory area activated. Also, Pneumotaxic area continuously transmits impulses to inspiratory area which have a negative effect and turn off inspiratory signal [prevents over-inflation of lungs]:
– Strong impulse = 0.5 sec inspiration → secondary effect to increase breathing to 30- 40 breaths/min;
– Weak impulse = 5 - 7 sec inspiration.
* Hering - Breuer Reflex: stretch receptors in lung tissue (see diagram previous slide), bronchi, bronchioles may on activation transmit inhibitory signal via the vagus nerve (X) to the inspiratory area; prevents over-inflation of the lung
