Lecture 31: Gases And Respiaration

Question 1

All respiratory surfaces have 3 things in common:

Answer 1

1. Large surface area for exchange
2. Thin respiratory membrane
3. Respiratory surfaces remain moist

Question 2

What are the 4 stages of respiration?

Answer 2

1. Bulk flow if air/ water
2. Gas exchange (diffusion)
3. O2 and CO2 transport
4. Gas exchange at tissue (diffusion)

Question 3

Aquatic respiration

Answer 3

Multicellular aquatic animals use gills for gas exchange

1. Large surface area for exchange
2. Highly vascularised
3. Thin membranes result in low diffusion resistance
4. Frequently protected by coverings (opercular flaps)

Question 4

Fish gills

Answer 4

• 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

Question 5

What is countercurrent exchange?

Answer 5

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

Question 6

What is concurrent exchange?

Answer 6

• initially a steep gradient permits oxygen diffusion.
• over distance, %O2 reaches equilibrium and diffusion stops.
• less efficient than countercurrent exchange

Question 7

Avian anatomy- air sacs

What is their function?

Answer 7

-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

Question 8

Avian anatomy- lungs

Answer 8

-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

Question 9

Avian anatomy- parabronchi

Answer 9

Air capillaries carry air from one parabronchus to another

Question 10

What do the 2 cycles of avian respiratory involve?

Answer 10

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

Question 11

Avian vs mammalian respiration

Answer 11

• 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!

Question 12

What are the parts of the upper respiratory tract and lower respiratory tract.

Answer 12

URT:

• nasal cavities
• oral cavity
• pharynx
• larynx

LRT:

• trachea
• bronchi
• bronchioles
• alveoli

Respiratory system is internalised to prevent dehydration

Question 13

URT: nasal cavities and their function

Answer 13

-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

Question 14

URT: oral cavity

Answer 14

• can bypass the nasal passageway to breathe
• breathing through mouth is important during: nasal obstruction and exercise
• limited heating, humidification and particle trapping

Question 15

URT: Larynx and function

Answer 15

-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

Question 16

URT: Laryngeal cartilages

Answer 16

Epiglottis: close entrance to trachea during swallowing

Arytenoid cartilage: house the vocal cords

Question 17

Function of larynx: Epiglottis

Answer 17

• closes entrance to larynx during swallowing
• prevents food/ liquid from entering the trachea
• food directed towards the oesophagus

Question 18

The lower respiratory tract consist of 2 zones, which structures do each zone contain?

Answer 18

1. Conducting zone: larynx, trachea, primary bronchi, secondary bronchi, tertiary bronchi, smaller bronchi, bronchioles, terminal bronchioles
2. Respiratory zone: respiratory bronchioles, alveolar sacs

Question 19

Conducting zone: Trachea

Answer 19

• 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

Question 20

Conducting zone: bronchi/ bronchioles

Answer 20

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

Question 21

LRT: respiratory zone

And what does it consists of?

Answer 21

• 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

Question 22

Respiratory zone: Alveoli

Answer 22

Type 1 alveolar cells: form the structure of alveoli
Type 2 alveolar cells: synthesize surfactant
Alveolar macrophages: patrols the inner surface if alveoli

Question 23

Respiratory membrane

Answer 23

• 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

Question 24

Surfactant

Answer 24

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)

Question 25

Surfactant deficiency with premature birth

Answer 25

• surfactant production begins later during gestation
• if babies are born prematurely, they have insufficient surfactant
• work to overcome surface tension is increased
• difficulty breathing

Question 26

Pleural membranes

Answer 26

-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