Lecture 7 - Insect Respiration and Circulation Flashcards
Respiratory System of Insect
(3)
The respiratory system of an insect consists of spiracles and trachea that are connected
(A) The spiracles are present on the external surface of the insect
(B) The trachea are present on the internal surface of the insect
Circulatory System of Insect
(3)
The circulatory system of an insect consists of dorsal blood vessel
These dorsal blood vessel is made up of of multi-chambered heart and aorta (Muscular tube)
The aorta is present on the thorax of the insect and it goes toward the head of the insect
Background information: Respiratory Systems of Insects
(2)
Air will enter through their spiracles which are holes in the abdomen and thorax of insect
Air enters the spiracle to travel through a network of tubes known as the trachea to reach the cells in the insect body
2 main components of the respiratory system
a. Spiracles
b. Trachea
Spiracles
(5)
These are external opening on the external surface of the insect
There are ONLY one pair of spiracles per segment
Usually these spiracles occur on the mesothorax, metathorax and the abdominal segments (1-8)
There are no spiracles on the head, prothorax, and genital segments
The spiracles are connected to the longitudinal tubes known as the tracheoles
Trachea
(2) +EG
These are series of air-filled tube that are unique to insects
These trachea are lined with cuticle and are extensively branched (Eg. 39% of body volume of the June Beetles)
Components of Insect Trachea
(3)
a. Tracheal Trucks
b. Taenidia
c. Tracheoles
Tracheal trunks
Longitudinal Truck
Taenidia
Spiral cuticular thickening that line ONLY the trachea, w/o the taenidia the trachea would collapse
Tracheoles
(2)
- These are the smallest diameter tubes ( < 1 micron in diameter that extend b/t the muscles)
- Deliver oxygen to all cells of the body, and each tracheoles end blindly
Trachea in Silkworm larva
Each spiracle consists of 103,000 tracheoles with a combination of 1.5 million together
What happens when an insect is a rest in a respiratory system?
(3)
- When an insect is at rest, there are fluids known as resting tissue at the tips of the tracheoles
- O2 will enter the tissue, and the purpose of the fluid at the resting tissue is to assist in gas exchange
- When the insect is active, there is a change in fluid, as it moves into the cell of the insect to provide more space for gas exchange (this allows for more O2 exchange and CO2 moving out)
Passive Diffusion in Small Insects
(4)
Passive diffusion occurs in small and non active insects
O2 moves by passive diffusion in insect by the spiracles
The spiracles are the major source that is used to prevent dessication (water loss) as the spiracles are usually only ½ to ⅓ open
This allows for continuous O2 uptake and CO2 storage which causes suction
CO2 expel in Small insect
(3)
CO2 is stored in the hemolymph as bicarbonate and is expelled by the cyclical bursts
The cyclical bursts creates a negative pressure that is sucked into the trachea
When the concentration of the CO2 in the trachea is greater than 6.5%, this causes the spiracles to relax and CO2 is expelled
Example of Cyclical Bursts interval in other insects
(2)
(A) Every 20 mins it is expelled in the termites
(B) Every 6hr it is expelled in the moth pupae
How do insects prevent water loss?
(2)
Spiracles are ⅓ open
Cyclical bursts
Steps of Active Diffusion in Large Insects
(4)
Large insects would need to use active transport as they move air into and out of the tracheal system
This is done by opening the forward spiracles (meso and metathorax spiracles) and the rear segment (abdominal segment)
Insect close forward spiracles and forces air out of the rear spiracles by increasing their blood pressure and muscle contraction
Insects close spiracles in the rear segment which creates a negative pressure to allow for air to come into the forward spiracles
