COMPANA LEC LE3 (Respiratory)

• Use of oxygen and expulsion of carbon dioxide via diffusion

Function of respiratory system

• External

• Internal

Types of respiration

exchange of gases with the environment (fetal membranes, skin surface ,lungs)

External respiration

Exchange of gases in capillary beds

Internal respiration

• Large surface area of contact

• Thiner barrier

• Adequate time for gas exchange

• Large diffusion gradient

Rate of diffusion

faster diffusion

Thinner barrier is

Q - rate of diffusion

D - Diffusion constant of medium 

A - surface area across which the substance or energy is transferring 

C1 - external concentration

C2 - internal concentration

L -Thickness of barrier 

Fick's law of diffusion

oxygen

The bigger the area or organism, higher demand for

• Ventilation rates

• Number of surface area

• Amount of gas respired

• Body size

Modifiable vertebrate features

• External and Internal vertebrates

1. External and internal gills

2. swim bladders or lungs

3. Skin and buccopharyngeal mucosa

Primary organs in adult vertebrates

• Filamentous outgrowths of the posterior trunk and thigh (African hairy frog)

• Lining of the cloaca

• Lining of esophagus

Less common respiratory devices

• Plethodontid salamanders do not have lungs and use the skin for respiration

• Found in chordate ancestors of vertebrates

• To increase gas exchange (or rate of diffusion) via the skin:

1. Increase surface area for diffusion via skin folds or papillae

2. thinner skin 

Cutaneous respiration

External gills

Develop from surface ectoderm and extend beyond the head, only in amphibians, e. Caecilians and urodeles

Internal gills

• Develop from endodermal walls of the embryonic pharynx.

• Pharynx: foregut that is between the developing oral cavity and esophagus

Spiracle

First to be spherical

Pharyngeal pouches

develop in lateral walls of embryonic pharynx with 6 or more pairs

Visceral grooves

lie opposite the pouches on outside of body

Closing plates

separate the pouches and grooves 

Visceral arches

separate adjacent pouches, each containing its respective aortic arches 

• 6 or more (15) pairs of pouch/sac-like gills (gill chambers)

• pouched gills

• pouches connected to pharynx by afferent branchial ducts and exterior by efferent branchial 

Gills in Agnathans

• 5 naked gill slits

• 1st pair of pharyngeal pouch is modified as the spiracle

• anterior and posterior wall of the 1st 4 gill chambers have a gill surface

• septal gills

• posterior wall of last (5th chamber) has no demibranch

Gills of cartilaginous fishes

• Demibranch

• Gills filaments

• Interbranchial septum

• Gill rakers

• Gill bar

1. Holobranch

2. Hemibranch

3. Pseudobranch

Parts of gills in sharks

Demibranch

gill surfaces in walls of all gill chambers (except the caudal wall of the 5th gill chamber) 

Gill filaments

on demibranch have gill lamellae (with capillary beds) where gas exchange occurs

Interbranchial septum

seperate each gill pouch, demibranchs on either side, ends at a flap valve

Gill rakers 

as gill arch projections that protect demibranch lamellae from water particles

Gill bar

gill arch +blood vessels + nerves + muscles +integument

Holobranch

demibranch on anterior and posterior side

Hemibranch

one side only

Pseudobranch

not for respiration

Dual pump system ventilation

How do sharks breathe

Dual pump system ventilation 

Draw water into the mouth or spiracle and then expel it via the gills

Suction pump, force pump

Equivalent of inhale and exhale

Suction pump

• Inspiration 

• External gill slits closed

• Mouth and spiracle open

• Floor of pharynx is depressed

• Walls of gill chambers expanded by levator and hypobranchial muscles

Force pump

• Expiration

• Mouth and spiracle closed

• Floor of pharynx is elevated

• Constrictor muscles compress branchial chambers and force water out

• Countercurrent flow of blood and water for gas exchange

• Sharks swim with mouths open to lessen energy expenditure

• No interbranchial septa, hemibranchs at the first pair of gill pouches

• Spiracle (lost) while some may develop a pseudobranch

1. Opercular gills

2. Operculum = bony flap that originates from the hyoid arch 

3. 4 to 5 gill pouches

Gills in Bony fishes

gain oxygen from air

low oxygen conditions allow fishes to

Air sacs → lungs or swim bladder

Evolution of air breathing organisms

• In low oxygen conditions such as drying pools and warm, anoxic swamps

• Allow gaining oxygen from air “bimodal breathers”

• Use of outpocketings of gill arches 

Functions of accessory organs 

• some fish can drown if forced to stay under water too long 

• special body structures adapted to breathe air, particularly the labyrinth fishes 

Air breathing in bony fishes 

1. External gills

2. filamentous extension of internal gills 

3. Internal gills 

Larval gills 

External gills

• Outgrowths from the external surface of 1 or more gill arches 

• Found in lungfish and amphibians

Filamentous extension of internal gills 

• Project through gill slits

• Occur in early stages of development of elasmobranchs

Internal gills

hidden behind larval operculum of late anuran tadpoles

Gas or Swim bladders 

• Internal organ (paired or unpaired) filled with gas but not always respiratory in function (most bony fishes)

• Located high in the body cavity for buoyancy 

• Not found in cyclostomes, cartilaginous fishes and some bony fishes 

1. Physoclistous 

2. Physostomous

Types of swim bladders 

Physoclistous 

• Independent of esophagus (no duct)

• Not respiratory in function: buoyancy

• Specialized

• Marine dwellers

• May be used for “hearing” or sound production via vibrations 

Physostomous

• Connected to esophagus by pneumatic duct

• Functions as a primitive lung

• Primitive or unspecialized 

• Freshwater dwellers 

hydrostatic organ (regulating a fish’s specific gravity)

swim bladders primarily serves as a

oval body on posterior part of bladder

Gas is resorbed via the ______

• hearing = by way of pressure waves transmitted via the swim bladder and small bones called Weberian ossicles

• Sound production = muscles attached to the swim bladder contract to move air between ‘sub-chambers’ of the bladder. Resulting vibration creates sound in fish such as croaks, drums, and grunts 

• respiration - swim bladder of lungfish has number subdivisions or septa and oxygen and CO2 is exchanged between the bladder and the blood 

Functions of swim bladders

• Internal organ derived from gut tube that is filled with air and functions in respiration 

• Derived from physostomous bladders 

Functions of lungs

• Usually paired

• Higher surface-to-volume ratio

• Join ventral side of gut via trachea 

• Receive deoxygenated blood via vessels

• Return oxygenated blood directly to heart without prior mixing 

evolution of lungs from amphibians to mammals

• adaptation to increasing body size or metabolic rate by increasing the compartmentalization of lungs

• With associated structures: larynx, trachea, syrinx, etc

primary evolutionary trend of lungs

• 2 large, simple sacs with short bronchi 

• Ventral outpocketings of the gut but lie dorsal to it

• Larynx 

1. Arytenoid cartilages: dorsal pair for support of vocal cords

2. Cricoid cartilages: ventral pair derived from primitive visceral arches 

Lungs of anura

• simple, long slender sacs with smooth walls

• Most species rely entirely on cutaneous or gill respiration 

Lungs of urodela

Pulse (Expiration) Pump Ventilation 

• Fresh air is stored within buccopharyngeal space (the floor serves as the pump)

• Cutaneous respiration allows carbon dioxide to escape via the skin 

• Variations based on degree of compartmentalization

• Trachea and bronchi longer than amphibians and are supported by cartilaginous rings

• Each bronchus enters lung near the middle or anterior end but not the apex/tip 

Lungs of reptiles

• Dorsal arytenoids and ventral cricoids join the hyoid apparatus (except in snakes) 

• Vocal cords in some lizards only 

Larynx of reptiles

• Entrance of air in partly closed glottis and sound-producing flap

• Snakes rub scales of adjacent body regions 

Hissing of reptiles

• Inspiration via negative pressure

• Expiration is passive or via constriction

• Aspiration pump of amniotes allows the oral cavity and

• pharynx to perform feeding functions

• it also requires strong ribs, intercostal and abdominal muscles

• Labyrinthodonts are the first known aspiration breathers 

Characteristics of aspiration pump ventilation

• Unique respiratory morphology also involved in thermoregulation 

• Smaller lungs compared to reptiles and mammals but with 9 accessory air sacs

• Air sacs are involved in ventilation but not in gas exchange/respiration

1. One interclavicular sac

2. Two cervical sacs

3. Two anterior thoracic sacs

4. Two posterior thoracic sacs

5. Two abdominal sacs 

Lungs of birds

• very long trachea

• Syrinx: avian voice box; point where trachea bifurcates into two primary bronchi

• Ventilation: aspiration pump

• Gas exchange: 2-cycle crosscurrent (unidirectional) 

Trachea in birds

1. On first inhalation, air flows through the trachea and bronchi and primarily into the posterior air sacs

2. On exhalation, air moves from the posterior air sacs and into the lungs

3. With the second inhalation, air moves from the lungs and into the anterior (front) air sacs

4. With the second exhalation, air moves from the anterior air sacs back into the trachea and out 

2-cycle crosscurrent flow ventilation

sternum moves downward then forward

During inspiration:

• sternum moves backward then upward

• Vertebral ribs move caudally through muscles attached to uncinate processes 

• Movement of vertebral ribs retract the sternal ribs reducing the thoraco-abdominal cavity

During expiration

• lungs even more finely divided

• Lobes absent or present

• Trachea divides into right and left primary bronchi the enter lung anterior and dorsal to center

• Primary bronchi divide into smaller bronchi and finally into bronchioles (membranous) which further divide into respiratory bronchioles where gaseous exchange occurs 

• end at alveolar duct systems 

Lungs for mammals

• Paired arytenoids + cricoid + thyroid + several other small cartilages including the epiglottis (closes glottis when swallowing) + vocal cords

Larynx of mammals

aspiration pump (bidirectional air flow), Trachea → 1^o bronchi → 2^o bronchi → bronchioles → alveoli 

ventilation of mammals 

uniform pool

Gas exchange in mammals

produce sound from vocal cords

voice production for reptiles and mammals

generate sound from tracheal ridges in trachea

voice production for frogs

produces sound from syrinx (right above the tracheal bifurcation)

voice production for birds

cartilages and intrinsic laryngeal muscles 

Mammalian larynx consist of 

lobes of the lungs

lobes of the lungs

Patterns of Gas transfer in chordates

Patterns of Gas transfer in chordates

Buccal pump: lung ventilation powered by cranial musculature only (exhalation passive)

Expiration pump: Active exhalation powered by axial muscles (buccal pump retained for inhalation)

Aspiration pump: Inhalation powered by axial muscles

Different pumps and definition