Respiratory System and Cardiovascular System Flashcards
(82 cards)
1
Q
What is respiration?
A
Exchange of gasses between surface of an organism and its environment for purpose of metabolism
2
Q
What is external respiration?
A
O2 from environment to blood / CO2 from blood to environment
3
Q
What is internal respiration?
A
O2 from blood to tissues / CO2 from tissues to blood
4
Q
What is ventilation?
A
Or breathing
It is the active process of moving the respiratory medium, water or air, across the exchange area
5
Q
What is gas exchange affected by?
A
Surface area
Diffusion distance (tissue thickness)
Diffusion resistance of tissue
Large gas partial pressure gradient
6
Q
What do we know about animals respiring in water vs air?
A
More dense –> Ventilation of water is costly
Gills - buoyant in water, collapse in air
Partial pressure of O2 variable, < than air
7
Q
How do internal gills work?
A
Associated with pharyngeal slits and pouches.
Protected by bony operculum or interbranchial septum
Ventilation usually involves muscular pump of buccal cavity actively driving water
8
Q
What is ram ventilation?
A
Occurs in active fishes swimming forward through water.
Ventilation is unidirectional
9
Q
What is the structure of gills? How does this suit function?
A
In cross section, each gill is V-shaped (lamellae)
Blood flows in one direction and water in opposite to establish a countercurrent exchange
10
Q
What is concurrent flow?
A
Blood and water flows in the same direction
11
Q
How does ventilation in Air-breathing fish work?
A
Fresh air enters through the mouth
Sternoyoideus
Mixed Air
Open glottis
Elastic recoil + smooth muscles of the lung
Mouth closes
Branchial constricts
Glottis closes
Lung pressurises
12
Q
What is the structure of external gills?
A
Same structure
Larvae of many vertebrates e.g. lungfishes, lissamphibia, some actinopterygians
Ventilation passive, but can be active
13
Q
What are accessory organs for external gills?
A
Any vascularised surface!!
Digestive tract
Mouth
Cloaca
Pectoral fins in embyronic fishes
Skin - cutaneous respiration
14
Q
What do we know about lungless caecilian?
A
Nares are sealed
How does it respire?
Largest tetrapod to lack lungs
Very poorly known species
15
Q
What do we know about the evolution of gas bladders?
A
Swim bladders, lungs
Outpockets of gut/pharynx
Have equivalent nerve and muscle supplies
Homologous?
Buoyancy control and sound
vs respiration
16
Q
What were the lungs like in early tetrapods/lissamphibia?
A
Sacs, sometimes with convolutions to increase the surface area, but still heavily reliant on skin-based diffusion; buccal pumping
17
Q
What were the lungs like in amniota?
A
Complex sacs, faveoli, one-way air flow common (reptilia) - not “primitive”!
18
Q
What are mammalian lungs like?
A
Alveoli, the branching bronchial tree, and diaphragmatic ventilatory drive
19
Q
What happens in aspiration breathing in amniota?
A
Mouth no longer involved
Inhalation is active: Thoracic and diaphragmatic movements
Air inhaled by suction
20
Q
Describe how tetrapod lungs are adapted:
A
Adapted for air breathing
Elastic: Volume expands when air is inhaled; decreases when exhaled
21
Q
What do mammalian lungs end in?
A
Alveoli
22
Q
What do reptilian lungs end in?
A
Faveoli
23
Q
What does faveoli look like?
A
Spongey appearance
Not found at end of highly branched tracheal system
24
Q
What does the diapragm do in human lungs?
A
In front of the liver
Helps drive ventilation
Same fundemental structure and function as other mammals
25
How do reptiles breathe?
Air through trachea into central chamber (in lungs), diffuses into faveoli
In monitor lizards, crocodiles and turtles, chamber is subdivided; unidirectional air flow common
Internal chambers are ventilated by respiratory movements
26
What is some of the lung of some snakes?
A nonexchange region in some snakes in the posterior part of the lung.
27
What do we know about crocodylia breathing?
Highly specialised
"Hepatic piston ventilation": Liver drives lung volume changes via abdominal muscle action
(diaphragmatic muscle behind liver = inspiration)
Lung structure is highly similar to birds (homologous)
28
What are the main parts of the avian lung?
Primary bronchi do not enter lung but extend to posterior air sacs
9 avascular air sacs connected to lungs, extend into most large bones
1-way parabronchi permit air flow through the lungs
29
What are the components of avian lungs?
Anterior air sac
Medioventral bronchus
Parabranch
Mediodorsal bronchus
Mesobronchus
Posterior air sac
Accelerating segment
Primary bronchi
Syrinx
Trachea
30
Where does gas exchange occur in avians?
Small air capillaries open off walls of each parabronchus
Gas exchange with the blood actually occurs in air capillaries
31
What are the steps in avian inhalation and exhalation?
Inhalation 1:
Air through bronchi to lungs and posterior air sacs
Exhalation 1:
Air from posterior air sacs to parabronchi, to faveoli
Inhalation 2: Air from faveoli to anterior air sacs; more fresh air to posterior air sacs
Exhalation 2:
Air from posterior air sacs to parabronchi, to faveoli, plust anterior air sac air out through bronchi and trachea
Multiple steps happen simultaneously = constant flow of O2 through the lungs
32
What happens in archosaur ventilation?
Homologous form and function in crocodylia and aves (and dinosauria!!)
Unidirectional/flow through
Inspiration = air in through dorsibronchi
Expiration = air out through the parabronchi to the ventrobronchi
33
What is the fish ventilatory mechanism?
Countercurrent
34
What is the avian ventilatory mechanism?
Cross-current
blood travels up to the medium containing gas
35
What is the mammalian ventilatory mechanism?
Uniform pool.
Where medium containing gas can collect and more can come in and more can leave.
36
What are the three major phases of the evolution of ventilation?
Linked to water-land transitions
1. Buccal pump
Lung ventilation powered by cranial musculature only (exhalation passive)
2. Expiration pump
Active exhalation powered by axial muscles (buccal pump retained for inhalation)
3. Aspiration pump
Inhalation is powered by axial muscles
37
What does axial bending do to breathing in laterally undulating vertebrates?
Makes breathing less efficient
Called "Carrier's constraint"
38
What did mammals, birds and crocodiles evolve due to Carrier's constraint?
Dorsoventral undulation
Birds w/bipedalism
Gular pumping as well
39
What features differentiate avian vs. crocodylian breathing?
Crocodylians don't have air sacs
Crocodylian lung exchange surface less specialised
Crocodylians use a hepatic piston for ventilation
40
How might there be an evolutionary constraint operating on having a lung vs. a swim bladder? Can a species easily have both?
Lungs and swim bladders are homologous
Lungs for respiration, swim bladder for buoyancy
Theoretically could have both but would have developmental constraints and possibly functional tradeoffs
Evolution tends to favour either/or
41
Outline how lungs, swim bladders and ventilatory mechanisms (co-) evolved across the vertebrate evolutionary tree:
1. Jawless vertebrates (agnathans)
- Lungs absent
- Swim bladder absent
- Ventilation muscular pumping of water through gill pouches
2. Jawed vertebrates (gnathostomes)
- Lungs absent
- Swim bladder absent
- Ventilation buccal pumping (most) or ram ventilation (in fast swimmers)
3. Bony fish
- Lungs present
- Swim bladder evolved later, from lungs in some lineages
4. Amphibians
- Lungs present but simple (sac-like)
- Swim bladder absent
- Ventilation buccal pumping (positive pressure breathing)
- Some skin respiration
5. Reptiles, birds and mammals
Reptiles
- Lungs more complex with internal partitioning
- Ventilation costal (rib) expansion, som use hepatic piston
Birds
- Lungs highly specialised, rigid lungs with air sacs
- Ventilation unidirectional flow with air sacs, sternum movement
Mammals
- Lungs highly branched alveoli for large suface area
- Ventilation negative pressure via diaphragm
42
How might lifestyle and gill form be related in fish?
Evolutionary pressures related to oxygen demand, habitat and activity level, ventilation method, metabolic needs
43
What does the conductive system of the heart include (briefly)?
The specialised structures that initiate a heartbeat and propagate it throughout the heart to result in coordinated contraction of the different chambers.
44
What are the four tissues that coordinate the contraction of the different chambers of the heart?
Sino-atrial node (SAN)
Atrio-ventricular node (AVN)
Bundle of His (AV Bundle)
Purkinje Fibres
45
What is the Sino-atrial node (SAN)?
Initiates heartbeat in the right atrium
46
What is the atrio-ventricular node (AVN)?
Conducts an impulse from the atria to the ventricular septum
47
What is the Bundle of His (AV bundle)?
Conducts impulse down the ventricular septum
48
What are the Purkinje fibres?
Conducts an impulse into the ventricular myocardium
49
What do all four of the tissues that form the cardiac conduction system consist of?
Modified cardiac myocytes
50
What happens in the SAN?
Firing of the SAN allows the impulse to spread through the adjoining myocardium of the Atria inducing contraction
51
What is the structure of the AVN in mammals?
NOTE - In mammals, there is a connective tissue boundary that separates the atria (and node) from the ventricles
Atrial septal cardiomyocytes
Transitional cells
Compact node
Central fibrous body
52
What are the structures of the Bundle of His and Purkinje fibres?
Similarly to the AV bundles are insulated from the myocardium of the septum/ventricles by connective tissue
53
What needs to occur for normal cardiac function?
A delay between atrial and ventricular contraction to allow for ventricular filling - in mammals the connective tissue boundary between the atria/ventricles forces the depolarisation to go from the atria to the ventricles through the AV node
54
What is the "p" wave of an ECG?
Indicative of atrial depolarisation
55
What is "QRS" complex in an ECG?
Indicative of ventricular depolarisation
56
What is "T" wave in an ECG?
Indicative of ventricular repolarisation
57
What is the "PR" interval in an ECG?
The time between atrial depolarisation and ventricular depolarisation, suggestive of AV conduction time
58
In mammals, avians and crocodilians, you see the 'normal' ECG. What about in other species?
In fish, amphibians and reptiles, an extra peak is present
African Lungfish
- SV
- P
- QRS
- T
Gunther's caecilian
- SV (larger)
- P
- QRS
- T
Corn Snake
- SV
- P
- QRS
- T
Emu
- P (+SV?)
- QRS
- T
59
What is the significance of the extra peak in an ECG of some species?
Reflects a specific anatomical difference between species
During embryonic development, the heart consists of a number of regions including the sinus venosius at the atrial pole
What happens to this tissue in later cardiac development differs between species
60
What happens to the sinus venosus in species with less complex heart structures?
The sinus venosus persists and is a contractile pre-heart chamber linking the caval veins to the right atrium
61
What happens to the sinus venosus in species with more complex heart structures?
The sinus venosus becomes incoporated into the right atrium
62
What impact does the Sinus Venosus have on Sino-Atrial node development?
In mammals there is a morphologically distinct sinus node structure that is incorporated into both the sinus venarum and right atrium which therefore depolarises both simultaneously upon firing
In animals with a separate sinus venosus there is no distinct sinus node but they do have equivalent tissue within the sinus venosus and then the wave of depolarisation passes on to the atria giving the distinct SV and P waves on the ECG.
63
Do avians have a distinct sino-atrial node?
NO
They have node-like tissue incorporated into both sinus venerum and atrium
64
What sinus venosus do crocodilians have?
A smaller-sized sinus venosus, as there is a partial incorporation into the right atrium, which results in electrical incorporation of the sinus into the right atrium without full physical incorporation
65
What do we know about conduction across the AV boundary and into the ventricles?
In mammals we've seen that there is a distinct AV node and bundle (Bundle of His) connecting the atria to the ventricles across an insulated boundary, the annulus fibrosis, between these two tissues
66
Do avians have an annulus fibrosus?
Yes
67
What is an annulus fibrosus?
An insulating layer between the atria and ventricles
68
Do fish, amphibia and reptiles have an annulus fibrosus?
No
69
What insulation do crocodilians have between the atria and ventricles?
They have insulation on the ventral part but not the dorsal portion
70
How do species that lack the annulus fibrosus conduct an impulse?
Similarly to those that have it!
Why?
71
What are the embryological origins of cardiac tissues?
Where do the AV node bundle and connective tissue (annulus fibrosus) originate?
In the embryo, these tissues are produced by a subset of cardiac myocardial cells - those that are at the atrioventricular junction and those that are at the tips of the developing atrial/ventricular (where present) septa
These cells are distinct from other myocardial cells as they express specific markers e.g. TBX3
72
What are the components of the embryonic heart?
Septum primum
Atrium
Atrioventricular canals
Ventricle
Interventricular septum
Dorsal endocardial cushion
73
When considered in 3d, these tissues in the embryonic heart form two connected rings. In mammals, these become specific structures. What are these structures?
Dorsal junction becomes the AV node, and the ventricular septal ring the AV bundles, whilst the atrial septal and AV rings produce the connective tissue boundary
74
When considered in 3d, these tissues in the embryonic heart form two connected rings. What happens in avians?
There is no distinct AV node produced from these tissues, but the AV conduction system is more extensive:
- In birds, more of the specialised myocardium produced during development is converted into conductive tissue such that the birds have a ring of tissue rather than a true node and a number of accessory bundles
75
So for the species that don't have the annulus fibrosus, what happens during development?
They still express the same markers of lineage as species that have the annulus fibrosus e.g. TBX3
As adults, though, the fibrosus tissue does NOT form, leaving a myocardial connection between the atria and ventricles
76
The myocardium does not produce the connective tissue barrier, but does it do anything else?
It persists into the adult as conductive tissue which transmits the depolarisation between the atrium and ventricle as all depolarisations anatomically must pass through these regions of specialised myocardium
77
Why is it important that the depolarisations only go through these specialised myocardial cells?
These specialised myocardial cells have different gap junction proteins (connexins) to normal myocardium
The depolarisation is able to travel faster between normal cardiomyocytes than through the gap junctions of conductive tissue myocardium
Physiologically this is desirable as it creaes a gap between contraction of the atrium and that of the ventricle to allow for ventricular filling before ejection
78
Does not having insulating connective tissue have any impact on cardiovascular function?
It does change the directionality of the ventricular contraction
Without an annulus fibrosus the wave of ventricular contraction starts at the base (where the specialised AV myocardium connects the atria to the ventricle) and spreads down to the apex of the ventricle.
79
What is the most significant contraction with an annulus fibrosus?
The most significant contraction is in an apex to base direction as the AV bundles largely divert the depolarisation through the ventricular septum to the apex and then spread back towards the base
80
What are the components of the adult ectotherm?
Compact wall
Luminal
1. AVC
Epicardial
2. Base
Both
3. Apex
81
What are the components of the adult endotherm?
Compact wall
Luminal
1. AVN
2. Apex
Epicardial
4. Base
3. Apex
82
What can we conclude about the cardiac cycle, tissues and structure?
In all species there is regulation of the cardiac cycle by specialised myocardial tissues
The structure of these tissues differs between species, most particularly between ectothermic and endothermic animals
These changes in structure result in subtle changes in cardiac physiology
