L31 Gases & respiration 2: Comparative structure & function

Question 1

List 3 features of respiratory membranes that facilitate diffusion.

Answer 1

1. large SA for exchange
2. Thin - small diffusion distance
3. Respiratory membranes retain moisture

Question 2

Aquatic respiration —- gills

Answer 2

• use gill for gas exchange
• Large SA for exchange/ highly vascularized 血管化
• thin membranes result in small diffusion distance
• frequently protected by covering/flaps (operculum)
• water flows unidirectionally into mouth, over gills, and exist via the operculum
• continuous flow of oxygenated water over gills
• some push water over gills using muscles of buccal cavity

Question 3

Explain how the countercurrent mechanism assists in aquatic respiration.

Answer 3

(continuous unidirectional flow of water and blood in opposite directions in the gills using countercurrent exchange)

Gas exchange is maximized.

Very efficient as a small but constant gradient maintained. Equilibrium not reached, diffusion continues to take place. (L31 P4）

Question 4

Describe the mechanisms for respiration in Amphibian.

Answer 4

Amphibian:

• young (larvae) use gills
• most adult use skin and simple lungs
• tidal ventilation
• large SA in lungs but low metabolic rates

Question 5

Describe the mechanisms for respiration in reptiles.

Answer 5

• suction pump ventilates lungs
• 2 phases:

Inspiration: ribs move forward and outward, thorax expand

Expiration: ribs move backward and inward, thorax compresses

use intercostal muscle 肋间 (sometimes exercise interferes with breathing* locomotion and breathing )

• low SA in lungs but also low metabolic rate

Question 6

Describe the mechanisms for respiration in mammals and birds.

Answer 6

Birds & Mammals:

• increased metabolic rate leads to increased demand for oxygen and increased CO₂ removed
• surface area of respiratory membrane in lungs increased dramatically
• mammal have numerous small alveoli
• birds have parabronchi with numerous air capilaries

Question 7

Avian lungs and air sacs

Answer 7

Avian lung:

• stiff with constant volume
• connect with air sacs that act like bellow

Air sacs

• expand and contract to move air through the lung
• most species have 7-9 sacs
• gas exchange does not occur in air sacs

* unidirectional flow of fresh air, gas exchange at the parabronchi (within air capillaries)

* air capillaries intertwine with blood capillaries to enable exchange (very efficient gas exchange)

Question 8

Avian ventilation P6 看ppt

Answer 8

Inspiration:

air sacs expand due to muscle moving the ribs & sternum out, expand body cavity

as caudal air sacs expand, air drown down the airways & into caudal air sac

Question 9

Resistance and velocity of the LRT

Answer 9

high resistance and high velocity on the upper part * trachea

low resistance and low velocity on the lower part * bronchioles alveolar sacs

Question 10

Describe the anatomical structures of the upper and lower respiratory tract (conducting zone and respiratory zone) in mammals and explain their functions.

Answer 10

Upper Respiratory tract:

1. nasal cavity:

*ciliated epithelium with mucus-producing goblet cells; turbinate bones (conchae) increase SA

F: cleaned, warmed, moistened

2. oral cavity

• by-pass NC, important during nasal obstruction and exercise

limited heating, humidification and particle trapping

3. pharynx

4. Larynx

• intricate framework of individual cartilage, muscle & connective tissue
• F: provide patent (open) airway; prevent food and liquid entering trachea during swallowing, initiate cough reflex if food/liquid enter; voice production *vocal cord open during breathing and closed during vocalization

Lower Respiratory tract: (series of branching tubes)

conducting zone: continue warming, humidifying and cleaning the air, goblet cell produce mucus traps foreign particles

5. Trachea

prevent airway collapse

allow for expansion of oesophagus

mucus in trachea triggers cough reflex

6. Bronchi ( 1 bronchus)

• trachea branches into 2 primary bronchi
• branch into narrower tubes *secondary and tertiary bronchi
• bronchi contain supportive cartilaginous plates
• mucus escalator to clean air

7. Bronchioles

• contain smooth muscle
• mucus escalator

8. terminal bronchioles

• last in conducting zone

Respiratory zone 2 sites of gas exchange (respiratory bronchioles * contain alveoli out pockets and alveoli)

9. Alveoli (1 alveolus)

• tiny sac-like structures involved in gas exchange

Question 11

List the cells of alveoli (3) and explain their role in respiration.**

Answer 11

Alveoli contain 3 types of cells:

1) Type 1 alveolar cells:

(pneumocytes) form the structure of alveoli; very thin cells for gas exchange

2) Type 2 Alveolar cells:

- synthesize surfactant that reduces surface tension in alveoli

3) Alveolar macrophages

patrol the inner surface of alveoli and ingest small foreign particles

alveolar pores (of Kohn)

equalize pressure between alveoli

Question 12

Define surfactant and explain how it assists in respiration.

Answer 12

surfactant monolayer

• reduce cohesive forces between water molecules
  1) increase lung compliance, allowing lungs to more easily expand
  2) reduce work of breathing
  3) increases stability of lungs

* prematurely often have insufficient surfactant lead difficulty breathing

Question 13

Describe the avian respiratory cycle.

Question 14

List the differences between respiration in mammals and birds.

Answer 14

Differences: