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
RESPIRATORY MEDIUM:
WATER OR AIR?
AQUATIC TO TERRESTRIAL TRANSITION IMPOSES
FUNCTIONAL CHALLENGES
unidirectional
Kardong f 11-42
unidirectional
ventilation
tidal ventilation
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
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
RESPIRATORY MEDIUM:
WATER OR AIR?
-correlated with circulation
AQUATIC
- BREATHE WATER
SERIAL CIRCULATION
Kardong f 12-6
TERRESTRIAL
-BREATHE AIR
PARALLEL CIRCULATION
GILL VENTILATION IN VERTEBRATES
-fish
-amphibians: all larval, some adults - Necturus
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
GILL BAR IN DOGFISH (CVH65)
filament with 2º lamellae
cartilagenous
gill bar
water flow
CHONDROCYTES IN GILL ARCH
CARTILAGENOUS ROD (CVH184)
LAMELLAE ON BOTH SIDES
OF GILL FILAMENT (CVH65)
filament
2º lamellae on filament
HISTOLOGY OF GILL LAMELLAE
2º lamellae attached to filaments
cell types:
epithelial cells
endothelial cells = pillar cells
chloride cells (ionophores)
mucus cells
2º LAMELLAE (CVH134)
epithelial
cells
pillar
cells
CVH134
CHLORIDE CELLS AT BASE OF 2º LAMELLAE (CVH134)
CVH134
mucous cells
CVH147
filament
blood vessels
afferent/efferent
GILL POUCHES IN LAMPREY HEAD
(HORIZONTAL SECTION, CVH99)
branchiopore
filaments
lining pouch
pharynx
gill
bar
CVH99
pumping
muscle fibres
run dorso-ventral
gill pouch
cartilagenous
gill bar
dorsoventral muscle
gill bar
CVH99
LUNG VENTILATION IN VERTEBRATES
ADVANTAGES OF AIR:
cheap cost to breathe: high 02 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 exchange organ: develop blind sac from gut
↑
-decrease blood-air barrier thickness: diffusion distance ↓
-increase internal surface area for exchange: septation
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
CUTANEOUS RESPIRATION IN FROG (CVH32)
capillary in
epidermis
CVH20
SEPTATION IN
FROG LUNG
trachea
1º bronchus
septae
SEPTUM IN FROG LUNG (CVH20)
GX = gas exchange
capillaries at surface
GX
smooth
muscle
GX
GX
CVH20
capillary
epithelial
cell
capillary
epithelial
cell
TOAD LUNG (CVH167) - SEPTATION > FROG LUNG
PLEURA AND SEPTAE CONTAIN ELASTIN (CVH167)
septae
pleura
SEPTAL WALL IN GAS EXCHANGE REGION (CVH167)
smooth muscle
and elastin
capillaries
epithelial
cells with flanges
SEPTAL WALL BETWEEN GAS EXCHANGE REGIONS
(CVH167)
-fewer capillaries
-connective tissue in wall (elastin)
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
TURTLE TRACHEA - SIMILAR TO MAMMALIAN (CVH97)
CVH97
respiratory epithelium
hyaline cartilage
RESPIRATORY EPITHELIUM IN TURTLE TRACHEA (CVH27)
PSEUDOSTRATIFIED, CILIATED COLUMNAR EPITHELIUM
WITH GOBLET CELLS
TURTLE LUNG (CVH88)
intra-abdominal muscle
faveoli
intrapulmonary
bronchus
EPITHELIUM: CONDUCTING TO GAS EXCHANGE
TRANSITION (CVH88)
FAVEOLUS
- gas exchange
BRONCHUS - conducting portion
- simple
-respiratory epithelium
squamous
epithelium
RESPIRATORY EPITHELIUM (CVH88)
GAS EXCHANGE REGION - FAVEOLUS
*
*
(CVH88)
GAS EXCHANGE REGION IN SUBFAVEOLUS (CVH88)
capillaries
SEPTUM IN FROG LUNG (CVH20)
*gas exchange
capillaries at surface
*
smooth
muscle
*
*
BIRD LUNG
HIGH EFFICIENCY - supports flight metabolic requirements
UNIDIRECTIONAL VENTILATION cross-current gas exchange between blood and air
capillaries
CROSS SECTION OF PARABRONCHUS (PB)
WITH INFUNDIBULI (IN) (CVH109)
IN
PB
CVH110
CVH109
air capillaries
IN
PB
AIR CAPILLARIES IN GAS EXCHANGE REGION (CVH109)
RESPIRATORY SYSTEMS
Basic requirements:
high surface area
short medium-blood diffusion distance
exchange surface highly vascularized
SEAL LUNG (CVH186)
HUMAN LUNG (HUM59)