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 arch Gill filaments 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

Blood Water 100% 20% 30% 35% 40% 45% 50% 55% 60% 30% 35% 40% 45% 50% 55% 60% 90% 85% 80% 75% 70% 75% 60% 90% 85% 80% 75% 70% 75% 60% NOT Countercurrent exchange Fluids flow in the same direction equilibrium between the two fluids occurs

Blood Water 100% 20% 30% 40% 50% 60% 70% 80% 20% 30% 40% 50% 60% 70% 80% 30% 40% 50% 60% 70% 80% 90% 30% 40% 50% 60% 70% 80% 90% Fluid flow in opposite direction Equilibrium never occurs

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 Operculum Mouth

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 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

Movement of the air sacs creates the ventilation (bellows) 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.

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 TracheaTrachea Posterior air sac LungsLungs Anterior 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.