The Respiratory System Flashcards
(26 cards)
How does gas exchange take place in small organisms?
gas exchange by diffusion across body surface
How does gas exchange take place in more complex/larger organisms?
specialised respiratory surface
+ circulatory system
(needed to move gas around: surface of body too small in relation to body volume)
What is a respiratory surface?
surface across which oxygen + carbon dioxide are exchanged
What are the ideal properties for a respiratory surface?
- high surface/volume ratio (large resp surface in relation to volume of animal)
- thin (diffuse gas)
- wet (dissolve gas: pass through membrane)
- well supplied in blood
- in contact with source of oxygen (air, water)
What is the believed ancestral origin of lungs?
-fish ancestral to land animals had air bladder that functioned as lung (outgrowth from gut)
-some relatives of these exist today:
ex: lungfish have both gills and lungs
(-problems with gills: vulnerable to damage and water loss)
Where do lungs initially develop in embryo?
-lung buds (homolog structure found in lung fish)
=outgrowth from foregut (beginning part of gut)
-in land animals (humans): lungs lie under/ventrally to gut
-lined with endoderm but surrounding support tissues are mesodermal
What are the components of the respiratory tract in humans?
Upper Respiratory Tract
- nasal cavity
- pharynx
Lower Respiratory Tract
- larynx
- trachea
- main + subsidiary bronchi
- bronchioles + alveoli
- associated blood vessels (pulmonary arteries + veins)
Thoracic Walls
-bony thoracic skeleton
-diaphragm
-intercostal muscles
(all 3 used for bringing air in/out of system)
-muscles of arm + abdomen (accessory muscles sometimes used)
What are the composition and function(s) of the ribcage?
Composition:
-12 pairs of ribs
-midline sternum
(ribs attached to sternum through costal cartilages
Function:
- protection of lungs
- also protection of heart + upper part of abdominal contents (liver, stomach, spleen…)
What are the major divisions of the thoracic cavity?
3 major divisions of thoracic cavity:
- 2 sperate pleural cavities
- mediastinum: central wall of tissue containing heart + major blood vessels + wrapped in fat membranes = wall (separates pleural cavities)
What is the pleura (of lungs)?
- pleura = double layer of membrane wrapped around each lung
- inner layer = visceral pleura
- outer layer = parietal pleura
-both layers in very close contact
=pleural cavity only a potential space (only contains a small amount of fluid - lubrication)
-if air/fluid enters pleural cavity: lung collapses
What is the size of the lung relative to the pleural cavity? Why?
lung is shorter than pleural cavity: -when quiet breaths/at rest = lung doesn't fill pleural cavity -when deep breath: = lung has space to expand into bottom of pleural cavity (diaphragm goes down, lung can fill that space)
What are the differences between the right and left lungs?
Right lung:
- a bit larger: 3 lobes
- divided by horizontal fissure + oblique fissure
Left lung:
- smaller: 2 lobes (space needed for heart)
- only oblique fissure
What is the hilum and what does it comprise?
Each lung has a hilum = root where structures enter/leave lung
- 1 main bronchus
- autonomic nerves
- 1 pulmonary artery (deoxygenated blood to lung)
- 2 pulmonary veins (oxygenated blood away from lung)
- small blood vessels
- lymphatic vessels
What forms the loose sleeve allowing lung roots to move up and down during breathing?
-hilum is also where visceral and parietal layers become continuous
=loose sleeve
(prevents tearing)
How do the lungs develop?
series of branching events:
- initial lung bud divides in tree-like way to form the bronchi and then smaller bronchioles etc
- alveoli develop at very end (premature babies have difficulty breathing)
Describe the bronchial tree in each lung
Each lung has
- 1 primary bronchus (division of trachea into each lung)
- 2 (left) or 3 (right) secondary/lobar bronchi (for each lobe)
- many smaller bronchi and bronchioles
Describe the cartilage in the bronchial tree
-cartilage = support
-almost full rings around trachea and primary bronchi
-as bronchi get thinner cartilage more fragmented
(less need for support)
-eventually no cartilage at all in respiratory bronchiole leading up to alveoli
What are alveoli and what is their purpose?
-alveoli = respiratory surface
-lined with simple squamous epithelium
=thin layer for gas diffusion (CO2 and O2)
What is emphysema?
- disease of the lung
- collapse of small bronchioles and alveoli (become saggy, walls break down)
- deterioration linked to age but accelerated by smoking/pollution
- black on outside of lung: tar/soot in lymphatics
How does gas exchange occur before birth?
What is the change that occurs at birth?
-before birth: gas exchange across placenta
-at birth: abrupt switch to breathing air
=lungs need to be ready for use
How long does lung development take?
- 9 months for mature lungs
- most of lung maturation takes place in last weeks of pregnancy
- 50-70 million alveoli at birth
- alveoli continue to form until 8 yrs of age
What is surfactant?
- lipoprotein secreted by cells in lungs
- stops thin-walled alveoli and terminal bronchioles from collapsing/sticking together
- artificial surfactant often sprayed into lungs of premature babies (have difficulty breathing)
In what directions must the thoracic cavity be expanded to draw air into lungs?
- bilaterally
- superiorly/inferiorly
- anteroposteriorly
Describe inhalation
- breathing in
- increase in volume = lower pressure
- ribs move up + out
- diaphragm flattens
- arm muscles can be used
