Transcript BIO 2310 - MSU Denver

Respiratory System

External respiration- gas exchange between
environment & body by diffusion
 Internal respiration – gas exchange between
blood & cells & usage of gas by cells
 Ventilation – bringing gas in contact with
respiratory exchange surface
– Water through gills
– Air in & out of lungs
Respiratory system

Cutaneous respiration
 Amphibians
Pharynx

External gills
 Some urodeles, dipnoans
 Form from skin ectoderm
 Beginning function early in life
Internal Gills

Within the contours of the body
 Development
– Internal pharyngeal pouches
– External visceral grooves
– Visceral arches for support
– Aortic arches
– Gill opening
Pharyngeal gills
Mouth
Pharynx
Gill filaments
Gill arch
Cartilaginous support
Gill Bar

All gill structures between the openings,
including visceral arches
 Visceral Skeleton
 Blood vessels (from aortic arch) and nerves
 Branchial muscles
 Respiratory epithelium – gill filaments with
lamellae to increase surface area
Gill surface
Gill structure

Gill septae or interbranchial septum is
between gills and the gill bar extends to
body surface for more support
Gill Structure

Gill rakers
 Inner surface of gills
 Keeps food out of gills
Gill structure according to
filaments
Holobranch – gill filaments on both sides of
gill
 Hemibranch – gill filaments on one side of
gill
 Pseudobranch – false gill, faces into spiracle
and monitors oxygen requirements to eye

Blood flow through gills

Afferent branchial artery
 Capillary beds for diffusion
 Efferent branchial artery
 Countercurrent flow
– Water flows inside to outside
– Blood flows outside to inside
Counter current exchange
NOT Countercurrent Blood
exchange
20%

Fluids flow in the
same direction
 equilibrium
between the two
fluids occurs
30%
35%
40%
45%
50%
55%
60%
Water
100%
90%
85%
80%
75%
70%
75%
60%
Blood
Water
20%
Fluid flow
in opposite direction
Equilibrium never
occurs
20%
30%
40%
50%
60%
70%
80%
30%
40%
50%
60%
70%
80%
90%
100%
Key Points
What does the term “countercurrent”
actually mean. How does this relate to the
water and blood flow?
 What is the advantage of countercurrent
flow?

Misc. Gill functions

Sodium absorption & excretion
 Nitrogen waste excretion
Gill Classification

Pouched gills
 5-15
 Agnathans
 External & internal branchial pores
 Pulsations of branchial muscles move water
in and out of same openings, as mouth is
attached to prey
Lampreys
Gill slits
Gill Classification

Septal gills
 Septae support gills and look like a set of
stacked plates = Elasmobranchs
 Spiracle is modified first gill pouch for
water intake
 Ventilation of gills
Gill Classification

Opercular gills
 Little or no septum because
 Operculum covers and protects gills
 Most do not have spiracle, some do
 Ventilation is similar to shark
Opercular gills
Gill arch
Gill filaments
Mouth
Operculum
Opercular gill
Opercular gill
Swim Bladder

Homology to lungs
 Develops from endoderm
 Swim bladder dorsal, lungs ventral
 About ½ bony fish have swim bladders
 20 fish genera are air breathers
 Seen in Devonian period 350-400 mya
Swim Bladder

Pneumatic duct
 Present during development
 Connects pharynx and swim bladder
 May stay open, may close
Swim bladder

Physostomous
 Bladder open – open pneumatic duct
 Physoclistous
 Bladder closed – closed pneumatic duct
Swim bladder

Physoclistous swim bladder is hydrostatic
 Gas gland – anterior area of bladder where
gas is secreted from blood to bladder
 Rete mirabile – marvelous network, red due
to blood vessels
 Countercurrent blood flow
Key Points

What is the function of a hydrostatic swim
bladder?
 Why must the pneumatic duct be closed for
a hydrostatic bladder?
Swim Bladder

Physostomous Swim Bladder
 Ventilation from mouth to pneumatic duct
to swim bladder
Misc. Swim Bladder functions

Resonance chamber for sound production
 Sound & pressure reception
– Weberian ossicles in some catfish, minnows,
carp that transmit sound waves to inner ear ears
Key Points

Weberian Ossicles are associated with swim
bladders in some fish. However, they
function like our middle ear ossicles. Name
our middle ear ossicles. What is the term for
describing nonrelated structures that
function similarly?
Tetrapod Respiratory Tree

Paired lungs (left & right)
 More surface area than fish and more
compartmentalization (e.g. lobes)
 Trachea connects throat with bronchial tree
 Blood flow is tremendous for gas exchange
Amphibian Respiration

Air is moved by pulse pump or forcing it
through gulping
 Anurans
 Larynx – cartilaginous entry into trachea
 Glottis is opening in larynx
 Arytenoid cartilages flank the glottis and
support vocal cords; Cricoid is last part of
larynx
Anuran Respiration

Trachea and bronchi
 Supported by cartilaginous rings
 Lungs are the location of gas exchange
 Ventilation involves gulping (pulse pump)
and internal nares are functional for first
time in evolutionary history
Respiration
& gas exchange
Amphibian Respiration

Urodeles
 Lungs often of minor importance
 Respiration often through external gills and
skin
Reptile Respiration

Similar to amphibians in anatomy
 Ventilation is by suction
 Inspiration involves creating negative
pressure inside chest cavity via intercostal
and abdominal muscles
 Expiration is passive
Mammal Respiration

Larynx
 Vocal cords
 Arytenoid cartilage supports vocal cords
 Cricoid cartilage
 New Thyroid cartilage
 New epiglottis
Mammal Respiration

Trachea
 Incomplete cartilaginous rings
 Cilia
Mammal Respiration

Bronchi
 Primary, secondary, tertiary
 Bronchioles – tiniest of airways, lacking
cartilage in walls
Mammal respiration

Lungs
 Alveoli
 Millions of tiny air sacs where gas exchange
occurs
Mammal Respiration

Ventilation
 Diaphragm creates sucking or negative
pressure for inspiration
 Expiration is passive
Avian Respiration

Very unique respiratory system
 Trachea delivers air to Bronchi
 The primary bronchi divided into
– Several Ventrobronchi
– Several Dorsobronchi
– Thousands of Parabronchi between
Avian Respiration

Air capillaries
 Open ended in the walls of parabronchi
 Form a honeycomb appearance
 Highly vascularized
Avian Respiration

Extremely efficient ventilation
 One way air flow
 Air sacs act as bellows to allow continuous
ventilation
 Efficient diffusion between air capillaries
and blood capillaries

All these bronchi are connected to the
mesobronchus, the trachea and the air sacs

Volume of the sacs
changes by
movement of the
sternum and the
posterior ribs.
 Air flow is
bidirectional in the
mesobronchus but
unidirectional in the
anterior/posterior
bronchi and
parabronchi


During inspiration
the air sacs expand
and draw air in
through the trachea
and mesobronchus.
Some goes to the
posterior sacs and
some goes through
the posterior
secondary bronchi
parabronchi and
anterior secondary
bronchi to the
anterior sacs.
Movement of the air
sacs creates the
ventilation (bellows)


During expiration the
air sacs “collapse” and
air is forced from the
posterior sacs through
the posterior
secondary bronchi, the
parabronchi and the
anterior secondary
bronchi into the
trachea.
Air from the anterior
sacs is also expired
through the trachea.

Air flow through the
parabronchi is
unidirectional and
maintained throughout
both inspiration and
expiration.
Avian Respiration

Air sacs
 Abdominal – 2
 Posterior thoracic – 2
 Anterior thoracic – 2
 Cervical – 2
 Interclavicular - 1
Air sacs
Trachea
Anterior air sac
Lungs
Posterior air sac
Avian Respiration

Air Sac Functions
 Penetrate some bones making them lighter
(hollow)
 Ventilation – continuous, but no exchange
of gases
 Thermoregulatory
 Buoyancy in water fowl
Key points

Why do you suppose avian respiration is so
efficient – more so than in mammals?
Avian respiration

Unique syrinx
 In interclavicular air sac region
 Vocal apparatus
Key Points

Name two respiratory structures unique to
birds.
 Name two respiratory structures unique to
mammals.