Lecture 31: Gases And Respiaration Flashcards
All respiratory surfaces have 3 things in common:
- Large surface area for exchange
- Thin respiratory membrane
- Respiratory surfaces remain moist
What are the 4 stages of respiration?
- Bulk flow if air/ water
- Gas exchange (diffusion)
- O2 and CO2 transport
- Gas exchange at tissue (diffusion)
Aquatic respiration
Multicellular aquatic animals use gills for gas exchange
- Large surface area for exchange
- Highly vascularised
- Thin membranes result in low diffusion resistance
- Frequently protected by coverings (opercular flaps)
Fish gills
- Water flows unidirectionally into fish’s mouth, over gills, and exit the operculum.
- continuously bathed with fresh water
- constant flow if water over gills maximised pO2 on external surfaces
- internally, circulation of blood maintains pO2 gradient by sweeping the O2 away as it diffuses from water
What is countercurrent exchange?
Water and blood flow in opposite directions in the gill using countercurrent exchange.
- very efficient as a small but constant gradient is maintained
- as equilibrium is not reached, diffusion continues to take place.
- gas exchange is maximised
What is concurrent exchange?
- initially a steep gradient permits oxygen diffusion.
- over distance, %O2 reaches equilibrium and diffusion stops.
- less efficient than countercurrent exchange
Avian anatomy- air sacs
What is their function?
-lungs communicate with air sacs
-most species have 7-9 sacs divided into cranial and caudal groups
-gas exchange doesn’t occur in these sacs, they just serve as reservoirs for air
Function:
-lungs to remain fixed volume
-unidirectional flow of fresh air
Avian anatomy- lungs
-divided into perforated tubes called parabronchi
-running between parabronchi are air capillaries
-air capillaries are the gas exchange surfaces
Refer to slide 13 for picture
Avian anatomy- parabronchi
Air capillaries carry air from one parabronchus to another
What do the 2 cycles of avian respiratory involve?
Cycle 1:
Inspiration: air moves to caudal air sacs
Expiration: air moves from caudal air sacs into lungs
Cycle 2:
Inspiration: air moves from lungs into cranial air sacs
Expiration: air is expired from cranial air sacs out of nostrils and mouth
Avian vs mammalian respiration
- lungs communicate with air sacs
- unidirectional flow of air
- lungs are rigid, therefore volume changes very little during ventilation
- no diaphragm
- parabronchi replace alveoli
- favours oxygen uptake at higher altitudes!
What are the parts of the upper respiratory tract and lower respiratory tract.
URT:
- nasal cavities
- oral cavity
- pharynx
- larynx
LRT:
- trachea
- bronchi
- bronchioles
- alveoli
Respiratory system is internalised to prevent dehydration
URT: nasal cavities and their function
-paired nasal cavities, separated by bony nasal septum
-ciliated epithelium with mucous-producing goblet cells
-turbinate bones increase surface area
-sinuses communicate with nasal passages
Function of nasal cavities:
1. Cleaned: hairs act as at filter. Mucous and cilia trap particles and microorganisms.
2. Warmed: contact with large surface area and mucous membranes warms air
3. Moistened: humidified through saturation with water vapour
URT: oral cavity
- can bypass the nasal passageway to breathe
- breathing through mouth is important during: nasal obstruction and exercise
- limited heating, humidification and particle trapping
URT: Larynx and function
-intricate framework of individual cartilages, muscles and connective tissue
Function of larynx:
1. Provides patent airway
2. Regents food and liquid entering trachea during swallowing
3. Voice production
URT: Laryngeal cartilages
Epiglottis: close entrance to trachea during swallowing
Arytenoid cartilage: house the vocal cords
Function of larynx: Epiglottis
- closes entrance to larynx during swallowing
- prevents food/ liquid from entering the trachea
- food directed towards the oesophagus
The lower respiratory tract consist of 2 zones, which structures do each zone contain?
- Conducting zone: larynx, trachea, primary bronchi, secondary bronchi, tertiary bronchi, smaller bronchi, bronchioles, terminal bronchioles
- Respiratory zone: respiratory bronchioles, alveolar sacs
Conducting zone: Trachea
- flexible tube consisting of cartilage rings, joined by connective tissue
- lined with ciliated, respiratory epithelium, interspersed with mucus-producing goblet cells.
- functions as a mucous escalator to rid debris
- majority of animals have incomplete cartilaginous rings, birds have incomplete cartilaginous rings
Conducting zone: bronchi/ bronchioles
Bronchi. Trachea branches into primary bronchi, which contain supportive cartilage plates to prevent collapse.
Bronchioles: small branches if smooth muscle, contain NO cartilage, less than 1mm diameter
Terminal bronchioles: last anatomical structure in the conducting zone
LRT: respiratory zone
And what does it consists of?
- site of gas exchange
- includes respiratory bronchioles and alveoli.
- gas exchange maximised by: large surface area, thin walls, no cartilage, no goblet cells (mucus), not much cilia
Consists of:
- respiratory bronchioles
- alveolar ducts: end in cluster of alveoli
- alveoli
Respiratory zone: Alveoli
Type 1 alveolar cells: form the structure of alveoli
Type 2 alveolar cells: synthesize surfactant
Alveolar macrophages: patrols the inner surface if alveoli
Respiratory membrane
- comprise type 1 pneumocytes, basement membrane and capillary endothelium
- membrane is very thin
- blood takes about 1 second to pass through lung capillaries
- blood becomes nearly 100% saturated with O2 and loses CO2
Surfactant
Surface acting agent
- alveoli are lined with fluid that creates surface tension, opposing expansion
- detergent-like substances that disrupts cohesive forces between water molecules
- surface tension is reduced by surfactant (type 2 alveolar cells)
Surfactant deficiency with premature birth
- surfactant production begins later during gestation
- if babies are born prematurely, they have insufficient surfactant
- work to overcome surface tension is increased
- difficulty breathing
Pleural membranes
-the pleura is a simple, squamous epithelial membrane
-visceral pleura line the lungs
-parietal pleura line the thoracic wall and mediastinum
-the space in between is the intrapleural space:
Intrapleural space contains a very thin film of fluid that:
1. Prevents separation of pleurae
2. Lubricates to permit friction free movement of lungs
3. Holds the lungs against the thoracic wall in a semi inflated state at rest
