BZ214 Exam 3: Evolution of the Lung

flashcards

What are the different types of organs used for respiration and what organisms are they used by?

Internal gills -- used by most aquatic organisms

External gills -- used by amphibians only

vertebrate lungs -- used by tetrapods

How do positive pressure systems of respiration work? what are the costs of positive pressure systems?

animals actively push air into their lungs via buccal pumping and/or gulping air; cost -- animals canNOT breathe and eat at the same time

what are some examples of positive pressure systems for respiration? (air-breathing fish and Anurans)

* __air-breathing fish__ gulp air into their oral cavity and use the pharynx as a suction pump to force air into the pneumatic duct
* __Anurans__ use their internal nares and glottis to force air from the buccopharyngeal space into their lungs
* Nares open and glottis closes; air is sucked into buccopharyngeal space; Nares close and glottis opens; throat is raised so air is forced into lungs
* the subsequent development of axial muscles and ribs has allowed for aspiration (a more efficient form of ventilation that instead uses negative pressure!)

what were the first animals to breathe via aspiration (negative pressure)? what are the benefits of negative pressure systems?

labyrinthodonts; allowed the oral cavity and pharynx to be used more for feeding so that the animal can breathe and eat at the same time

how do negative pressure systems of respiration work?

air is sucked into the lungs by negative pressure (the lungs are expanded to create low pressure inside, so thus air is pulled in)

what are some examples of negative pressure systems for respiration? (reptiles and mammals)

__**Reptiles**__ use the movement from their sprawling gait to expand or contract __one lung at a time__

__**Mammals**__ inflate their lungs via negative pressure by __contracting their diaphragm__

How do Agnathans (lampeys) respire?

tidal ventilation via gill pouches

how do elasmobranchs (sharks) respire?

they use forward movement / ram ventilation to flow water over their gills on each side of a gill septum; countercurrent exchange

how do bony fish respire?

the ventilate via buccal pumping to flow water over their gills, which are in a single chamber beneath a protective operculum; countercurrent exchange

how do amphibian larvae respire?

they have internal gills within a branchial chamber and some also have external gills; the gills are moved by muscles for gas exchange

what is the vertebrate lung a modification of?

the physostomous (“air gulping”) swim bladder

what is the general evolutionary trend in respiratory surfaces as vertebrates evolve?

increasing surface area via increased surface area of gills or increased compartmentalization of the lungs as body size and/or metabolism increases

what characteristics of lungs do amphibians like Anurans (toads and frogs) have?

large, short lungs and short trachea that divide into two bronchi

what characteristics of lungs do Reptiles have?

many heterogeneously partitioned compartments, long trachea, and long bronchi supported by cartilaginous rings

what characteristics of lungs do mammals have?

very finely compartmentalized lungs, trachea divides into right and left primary bronchi, which divide further into smaller bronchi and **respiratory bronchioles** (which contain alveoli, where gas exchange occurs)

what characteristics of lungs do avian animals (like birds) have?

avian animals have a very __unique respiratory system__ with __lungs and air sacs__ and **unidirectional airflow** (NOT tidal)

* there are usually 9 air sacs (which help pump air) connected to the lungs (which remain the same volume at all times)
* air flows first into the posterior air sacs, then through parabronchi into the lungs, then into the anterior air sacs
* **crosscurrent exchange** of gases occurs across the air and blood capillaries

what are the characteristics of tetrapod lungs (in comparison to fish lungs)?

* paired and ventral
* higher surface area-to-volume ratio
* trachea connects the lung to the pharynx
* glottis -- the opening to the trachea
* __trachea and bronchi__ are ringed with __cartilage to prevent collapse__
* low-oxygen blood is received via vessels related to the 6th aortic arches
* __oxygenated blood__ returns __directly to the heart__ __without prior mixing__

what are the characteristics of alveolar lungs and where are they found?

alveolar lungs have **alveoli** (sacs that inflate and deflate to __exchange oxygen and co2__ with blood); they are found in __synapsids__ like __mammals__

what are the characteristics of faveolar lungs and where are they found?

Faveolar lungs have **faveoli** (__air flows__ in __only one direction, cross-current to the blood__) which are more efficient and allow for a higher metabolic rate; found in __sauropsids__ (__birds__ and reptiles)

why are the kidneys essential to life on land? how do they work, and what is the loop of Henley?

to regulate water content; they work via a negative pressure system called the loop of henley that concentrates ions in urine; the loop of henley increases the surface area where diffusion can take place, which allows birds and mammals to have a higher solute concentration in their urine and thus conserve water

* water retention is especially important for endotherms because of their higher metabolic rate, which causes more breathing and water loss