1
RESPIRATORY SYSTEMS
Functions:
1º gas exchange: O2/CO2
water/acid-base balance
2º (air-breathers) vocalizations, thermal balance
Basic requirements:
-high surface area
-short diffusion distance for exchange
-gas-exchange region highly vascularized
BREATHING MEDIUM - RELATED FACTORS
medium sets energy costs to breathe
-water high mass, low O2 content → expensive
-air low mass, high O2 content → cheap
breathing cost sets ventilation mode
-water: unidirectional (mostly) → GILLS (AND SKIN)
-air: tidal (birds unidirectional) → LUNGS
2
VENTILATORY ORGANS: OLD OR NEW?
What are basic requirements for gas exchange?
-high surface area
-short diffusion distance for exchange
-gas-exchange surface highly vascularized
Adapt what already exists?
-skin
advantages: next to medium, vascularized, thin
disadvantages: protection function in conflict, SA low
-gut:
advantages: access to medium (pharyngeal region),
vascularized, SA can be increased
New structures
based on gut
-extend portion of pharynx wall into medium → GILLS
-develop internal blind sac from pharynx wall → LUNGS
3
RESPIRATION IN FISH - GILLS
-breathing medium: water - dense, low O2 content
-high metabolic cost to breathe
-unidirectional flow - most efficient
-gas exchange membrane extended into breathing medium
FISH GILL ORGANIZATION
Kardong f 11-4
4
TELEOST GILL
VENTILATION
PUMP CYCLE
-UNIDIRECTIONAL
FLOW OVER GILLS
Eckert f 14-31
TELEOST
GILL STRUCTURE
gill bar
bone or
cartilage
Eckert f 14-33
5
HISTOLOGY OF GILL LAMELLAE
2º lamellae attached to filaments
cell types:
epithelial cells
endothelial cells = pillar cells
chloride cells (ionophores)
mucus cells
PILLAR CELLS (=ENDOTHELIAL CELLS) DEFINE
BLOOD SPACES IN 2º LAMELLAE
Patt and Patt (1969) f 8-1
6
CORROSION CASTING OF BLOOD SPACES IN 2º LAMELLAE
Eckert f 14-34
BLOOD FLOW THROUGH TELEOST GILL
- COUNTERCURRENT EXCHANGE
Eckert f 14-35
7
BLOOD AND WATER FLOW IN OPPOSITE DIRECTIONS
PAST 2º LAMELLAE = COUNTERCURRENT EXCHANGE
Patt and Patt (1969) f 8-2
LAMPREY GILLS LINE
GILL POUCHES
-mouth attached to food
-blocks water intake
through mouth
-water flows into and
out of each pouch
via gill openings
Eckert f 14-32
8
LAMPREY GILL POUCHES
dorso-ventral
pumping
muscles
cartilagenous
branchial arch
pharynx
Kardong f 11-14
external
surface
gill pouch
opening
9
LUNG VENTILATION IN VERTEBRATES
ADVANTAGES OF AIR:
cheap cost to breathe: high O2 content, low mass
PROBLEM: can't extend gas exchange membrane into medium
-still need aqueous layer on membrane surface -gases dissolve in aqueous layer
-moisture loss damages membrane
TRENDS IN AIR-BREATHING
-internalize gas exchange organ: develop blind sac from gut
-increase internal surface area for gas exchange: septation ↑
-decrease blood-air barrier thickness: diffusion distance ↓
10
GAS EXCHANGE AREA INCREASES WITH MORE SEPTATION
Hildebrand f 13-8
LUNG VENTILATION
no ribs: positive pressure ventilation
amphibians
ribs: negative pressure ventilation
reptiles, birds,
ribs + diaphragm: mammals
11
AMPHIBIAN RESPIRATION
ALL MODES
GILLS: ALL LARVAL AND SOME ADULT FORMS
SKIN: ALL AQUATIC AND MOST SEMI-AQUATIC FORMS
LUNGS: SEMI-AQUATIC AND TERRESTRIAL FORMS
LUNGS:
TIDAL VENTILATION: POSITIVE-PRESSURE SYSTEM
-BUCCAL PUMP - JAW MUSCLES (NO RIBS)
STRUCTURE: LUNG SEPTATION MINIMAL
TRACHEA, BRONCHI SHORT
CILIATED EPITHELIUM, GOBLET CELLS
SEPTAL WALLS THICK
BLOOD-AIR BARRIER THICK
POSITIVE-PRESSURE VENTILATION
INSPIRATION: nares open, jaw floor drops, air into buccal cavity,
nares close, jaw floor rises, air into lungs
EXPIRATION: nares open, elastic recoil in lungs pushes air out
Eckert f 14-27
12
BLOOD-AIR BARRIER IN FROG LUNG SEPTUM
Patt and Patt f 8-14
REPTILIAN RESPIRATION
RIBS APPEAR → NEGATIVE PRESSURE
VENTILATION
LUNGS PAIRED (snakes, lizards may have one lung
reduced or absent)
TRACHEA, 1º BRONCHI cartilage reinforced,
ciliated with goblet cells
SEPTATION MORE COMPLEX
FAVEOLI - major and minor subdivisions
-gas exchange in septal walls
13
LIZARD LUNG SHOWING FAVEOLAR DIVISIONS
Gans and Gaunt (1998) f 1-15
FAVEOLAR LUNG STRUCTURE
F FAVEOLUS
SF SUBFAVEOLUS
gas exchange in septal walls
Gans and Gaunt (1998) f 1-6
14
SNAKES: USE ONE LUNG, OTHER REDUCED OR ABSENT
gas exchange region
- anterior
- vascular
- faveolar septation
saccular region
- no gas exchange
- no vascularization
- no septation
Gans and Gaunt f 2-3
FAVEOLAE IN GAS EXCHANGE REGION OF SNAKE LUNG
Gans and Gaunt f 2-4
15
BIRD LUNG
HIGH EFFICIENCY - supports flight metabolic requirements
UNIDIRECTIONAL VENTILATION cross-current gas exchange between blood and air capillaries
LONG CONDUCTING AIRWAYS - HIGH "DEAD" VOLUME
Eckert f 14-9
16
BIRD LUNG AND AIR SACS
trachea
lung
cranial
air sac
caudal
air sacs
Pough et al f 17-15
AIRWAYS IN CROSS-SECTION OF BIRD LUNG:
1º BRONCHUS→ DORSOBRONCHUS
→ PARABRONCHI → VENTROBRONCHUS
direction
of air flow
Hildebrand f 13-12
17
UNIDIRECTIONAL AIR FLOW IN BIRD LUNG
Eckert f 14-26
ANATOMY OF BIRD LUNG
Kardong f 11-35
18
PARABRONCHUS
STRUCTURE
Eckert f 14-25
PARABRONCHI WITH
INFUNDIBULI IN
WALLS
Farner and King (1972) p 294
CROSSCURRENT GAS EXCHANGE IN BIRD LUNG
-most efficient in vertebrates
Hildebrand f 13-11
19
COMPARISON OF AIR FLOW AT GAS EXCHANGE
MEMBRANE IN MAMMALIAN AND BIRD LUNGS
TIDAL
Kardong f 11-35
UNIDIRECTIONAL