Respiratory System (15) Flashcards
What happens to the air that enters the lungs?
> Condition of air entering lungs varies depending on external environment e.g. if it is cold/hot
As it moves into the lungs it is warmed/cooled to body temp and is then moistened and cleaned
Blood then transports the gases between the lungs and cells of the body
What is the main role of the respiratory system?
> To supply the body with oxygen and dispose of carbon dioxide
Most energy is derived from chemical reactions which take place in the presence of oxygen and carbon dioxide
What is external respiration?
> The exchange of gases between blood and lungs
O2 diffuses from lungs to blood
CO2 diffuses from blood to lungs
What is internal respiration?
> Exchange of gases between blood and cells
O2 diffuses from blood to cells
CO2 diffuses from cells to blood
What are the organs involved in the respiratory system?
Nose Pharynx Larynx Trachea 2 bronchi Bronchioles Alveoli 2 lungs
What is the nose?
> First respiratory passage that air passes through
Function= begin warming, moistening and filtering air
Very vascular
Functions of the nose- filtering and cleaning
> Hairs trap larger particles and the smaller particles (dust and microbes) stick to mucus
Mucus protects epithelium from irritation and prevents drying
Cilia waft mucus towards nose and throat to be swallowed/expectorated
Functions of the nose- humidification
> As air moves over moist mucosa, becomes saturated with water vapour
Irritation of nasal mucosa results in sneezing to expel irritants
Functions of the nose- olfaction
> Organ for sense of smell
Nerve endings to detect smell are found in roof of nose
Olfactory nerve carries smell nerve impulses to the brain to be interpreted
What are the functions of the pharynx?
> A passageway for air and food- air passes through nasal and oral sections and food passes through oral and larangeal sections
Warming and humidifying- air warmed and moistened as it passes towards lungs
Hearing- Auditory tube allows air to enter the middle ear. Hearing depends on presence of air at atmospheric pressure on either side of the tympanic membrane (eardrum)
Protection- Lymphatic tissue of tonsils produce antibodies in response to swallowed/inhaled antigens
Speech- Acts as a resonating chamber for speech sounds
What is the pharynx?
> 12-14cm
Tube extending from base of skull to level of 6th cervical vertebra
Lies behind the nose, mouth and larynx
What is the nasopharynx?
> Behind the nose
Has auditory tubes on the lateral walls leading to each middle ear
On posterior walls, there are pharyngeal tonsils (adenoids)
Most prominent in children up to 7yrs and gradually astrophy after this
What is the Oropharynx?
> Behind the mouth
> Lateral (side) walls have collections of lymphoid tissue called palatine tonsil
What is the laryngopharynx?
> Extends from oropharynx and continues as oesophagus
What is the larynx?
> Voice box
Extends from laryngopharynx to trachea
After puberty, grows larger in males (adams apple) and deeper voice sounds
Composed of several irregularly shaped cartilages
What are the functions of the larynx?
1) Produce sound- Sound has properties of pitch, volume and resonance
> Pitch- Depends on length and tightness of vocal cords- lengthen at puberty which is why boys’ voice drops
> Volume- Depends on force with which the vocal chords vibrate
> Resonance/tone- Shape of mouth, position of tongue and lips, facial muscles and air in sinuses
2) Speech- Occurs during expiration when sounds produced by vocal chords are manipulated with tongue, cheeks and lips
3) Protection of lower respiratory tract- During deglutition (swallowing), epiglottis covers over the larynx which ensures food passes into oesophagus not into the lower respiratory tract
4) Passageway of air
5) Humidifying, filtering and warming
6) Closed during coughing, sneezing and Valsalva’s manoeuvre
What is Valsalva’s manoeuvre?
1) Air is temporarily held in lower respiratory tract by closing the glottis
2) Causes intra-abdominal pressure to rise when abdominal muscles contract
3) Helps to empty the rectum
4) Acts as a splint to stabilise the trunk when lifting heavy loads
What is the trachea?
> Also known as the windpipe
Continuation of the larynx and divides at the carina into the left and right primary bronchi
One bronchus goes to each lung
Carina is rich in sensory nerve endings and irritation to this can cause a powerful cough reflex
What are the functions of the trachea?
1) Support and patency- arrangement of cartilage and elastic tissue prevents obstruction of airway when head and neck move. Absence of cartilage at the back allows the trachea to indent as food is swallowed and moves down the oesophagus
2) Muscociliary escalator- regular beating of cilia moves debris toward the surface to larynx where it can be swallowed/coughed up
3) Cough reflex- Nerve endings in larynx, trachea and bronchi are sensitive to irritation which leads to air release under pressure, expelling mucus and/or foreign material from mouth
4) Warming, humidifying and filtering
What are the bronchi and bronchioles?
> 2 bronchi formed when trachea divides
Right bronchus- wider, shorter, more vertical than the left, more prone to obstruction. After entering lung at hilum, divides into 3 branches, one to each lobe, each branch then divides into many smaller branches
Left bronchus- narrower. After entering lung at hilum, divides into 2 branches, one to each lobe, each branch then divides into progressively smaller airways
Controlled by autonomic nervous system
What are the functions of the bronchi and bronchioles?
1) Control of air entry- Diameter of respiratory passageways alters by contraction/relaxation of involuntary muscles in their walls which regulates the amount of air entering the lungs
2) Warming and humidifying
3) Support and patency
4) Removal of particles
5) Cough reflex
What is the respiratory membrane?
> An air-blood barrier which is composed of alveolar and capillary walls and their fused basal laminas
Alveolar walls are a single layer of type 1 epithelial cells and they permit gas exchange by simple diffusion
Type 2 cels secrete surfactant
Gas exchange takes place across this membrane
What are alveoli?
> Air sacs
Gas exchange takes place across the respiratory membrane which is made from alveolar wall and capillary wall
Surrounded by fine elastic fibres
Contain open pores which connect adjacent alveoli and allow air pressure throughout the lung to be equalised
Macrophages are present which keep alveolar surfaces sterile
Surrounded by dense network of capillaries
What is the structure of the lungs?
> 2 of them, one each side of the midline
In the thoracic cavity
Cone shaped
Apex- rounded, rises into the neck
Base- concave, semilunar in shape, sits on thoracic surface of diaphragm
Costal surface- convex, broad outer surface of the lungs which lies against the costal cartilages, ribs and intercostal muscles
Medial surface- Concave, contains roughly triangular shaped area called the hilum
Has structures such as bronchus, major blood vessels, lymph vessels and nerve supply
How are the lungs divided?
> Area between lungs is mediastinum
R lung divided into 3 lobes- superior, middle and inferior
L lung divided into 2 lobes- superior and inferior
What is the pleura?
> Closed sac of serous membrane which contains small amount of serous fluid
Lung is enclosed within the pleura
2 different types- visceral and parietal
What is the visceral pleura?
> Adheres to the lung, covering each lobe
What is the parietal pleura?
> Adheres to inside of the chest wall and upper surface of diaphragm
What is the pleural cavity?
> In health, a potential space which is separated by a thin film of serous fluid
This fluid allows pleura to glide over each other which prevent friction during breathing
What is normal lung capacity?
> Normal breathing= 15 complete respiratory cycles per min (inspiration, expiration, pause)
Lungs and air spaces never completely empty, this remaining capacity= anatomical dead space (approx 10ml)
What is tidal volume?
> Amount of air passing in and out of lungs during each cycle of respiration
Approx 500ml at rest
What is inspiratory reserve volume (IRV)?
The extra volume of air that can be inhaled into lungs during maximal inspiration
What is expiratory reserve volume (ERV)?
The largest volume of air that can be expelled from the lungs during maximal expiration
