Respiratory System Cockroach

What is the Respiratory System of Cockroach?

The respiratory system of cockroach is well developed and elaborate to compensate for the absence of respiratory pigment in the blood. It consists of a system of air tubes or tracheae through which every tissue of their body remains in direct contact with the air for gaseous exchange. The air enters and exits from the tracheae through the spiracles.

Anatomy Of The Respiratory System In Cockroaches

The cockroach's respiratory system is efficient and specially adapted for land life. Much of it consists of the tracheal system, a complex network of tubes that convey oxygen directly to tissues and organs. This is a representative of an insect breathing mechanism and thus places cockroaches at an advantage to proliferate in many environments.

Spiracles (Number, Structure, Control)

• There are ten pairs of spiracles or stigmata arranged segmentally, 2 pairs in the thorax and 8 pairs in the abdomen.

• Each spiracle is a slit-like aperture guarded by bristles or hairs to prevent the passage of dirt.

• The spiracles are opened and closed by valves regulated by sphincter or spiracular muscles.

• This mechanism prevents undue loss of water through the spiracles and also regulates the flow of the air through them.

• The aperture of each spiracle leads internally into a short chamber called atrium from which arises the main tracheal trunk.

Tracheae (Large Tubes)

• The haemocoel of cockroach contains a system of network of elastic, close branching and silvery white tubes called tracheae.

• The tracheae are formed by the pushing of the ectoderm. Hence, its wall consists of three layers: taenidia or intima, basement membrane and epithelium.

• The intima is the cuticular lining which prevents the tracheae from collapsing.

Tracheoles (Fine Tubes Reaching Cells)

• The ultimate branches of tracheae end in tracheole cells from which arise very fine tubes called tracheoles.

• The tracheoles have thinned cuticle lining and they end blindly in the tissue cells.

• In a resting insect when respiratory activity is not high, the tracheoles are filled, not with air but with a tissue fluid of cells in which oxygen dissolves.

Mechanism of Respiration in Cockroach

Respiration in cockroaches involves the intake, distribution, and exchange of gases. It is a very complex process.

Inhalation and Air Distribution

• Air is inhaled through spiracles.

• These spiracles form the entrance into large tracheal tubes.

• The tracheal tubes divide into smaller and smaller tubes called tracheoles.

• Through these tracheoles, the air diffuses directly into the body cells.

Gas Exchange at Cellular Level

• Gas exchange in cockroaches occurs at the cellular level through direct diffusion using the tracheal system

• Cells have oxygen from the tracheoles.

• Carrying carbon dioxide in the direction of the tracheoles.

• Driven by concentration gradients, the opening and closing are regulated to control the amount of air that passes through.

• During dry conditions when the rate of evaporation is high, they close themselves to prevent loss of water from the body.

Spiracle Regulation

The tracheal tubes and tracheoles make up the foundation of the cockroach's breathing apparatus, allowing for excellent gas exchange.

Structure and Function of Tracheal Tubes

• Large, air-filled tubes that come off the spiracles

• Anastomose into smaller and finer tubes to increase surface area

• Provide a pathway for the air to reach deeper tissues

Description of Tracheoles

• Very fine tubes off the tracheal tubes.

• Reach individual cells for direct gas exchange.

• Contain fluid at the tips to oxygen for diffusion.

Role of Hemolymph in Cockroach Respiration

Hemolymph is a colorless fluid that serves as the blood of the insect. The hemolymph of cockroaches does not have any gas transport. It largely transports nutrients and carries waste products. It also keeps the cellular activity that allows support of the tracheal delivery system.

Adaptation For Survival

Cockroaches have adapted to survive in different environments.

Prevention of Water Loss

Spiracles are closed most of the time to prevent water loss. The spiracles can be closed preventing water loss in a controlled way.

Tolerance to Low Oxygen Environments

The extensively branching tracheal system allows for efficient oxygen delivery.

Tolerance to High CO2 Levels

Low oxygen environments can be tolerated by lowering the metabolic rate. High CO2 environments can be tolerated due to the effectiveness of their tracheal system.

Survival Underwater

Some species can close their spiracles for a prolonged period and stay underwater.

Comparison of Cockroach and Human Respiration

Different organisms have evolved specialized respiratory systems. While humans use lungs for respiration, cockroaches have tracheal systems. Let’s take a look at the differences between the respiratory systems of the two.

Respiratory System of Cockroach NEET MCQs (With Answers & Explanations)

Important topic for NEET exam are:

• Anatomy of the respiratory system (Spiracles, tracheae, tracheoles)

• Mechanism of Respiration

• Role of Hemolymph

Practice Questions for NEET

Q1. In cockroach, air from atmosphere enters by

1. Trachea

2. Tracheoles

3. Spiracles

4. Chitin

Correct answer: 3) Spiracles

Explanation:

The respiration in cockroaches takes place through the trachea, which opens through 10 pairs of small holes called spiracles (2 pairs of thoracic and 8 pairs of abdominal) `

- wherein

Spiracles are further subdivided into Tracheoles from air to all the parts. The exchange of gases takes place at the tracheoles by diffusion.

Hence, the correct answer is option 3) Spiracles.

Q2. Respiratory movement in cockroach is coordinated by

1. Autonomous system

2. Nerve centres in thoracic ganglia

3. Myogenic centres in thoracic ganglia

4. Any two of them

Correct answer: 2) Nerve centres in thoracic ganglia

Explanation:

Tracheal Ventilation: It is the airflow within the tracheal system, which mainly results from the contraction and relaxation of abdominal muscles also known as tergo-sternal muscles. This process is perfectly regulated and coordinated at the nerve centres located in the thoracic ganglia. This facilitates proper ventilation within organisms like insects to keep optimal oxygen levels, and carbon dioxide is expelled by the tracheal system.

Hence, the correct answer is Option 2) Nerve centres in Thoracic ganglia.

Q3. Assertion: The blood in a cockroach lacks a respiratory pigment and appears colorless.

Reason: Gaseous exchange in cockroaches takes place solely through diffusion in the hemolymph.

1. If both the assertion and reason are true, with the reason providing a correct explanation for the assertion.

2. If both the assertion and reason are true, but the reason does not adequately explain the assertion.

3. If the assertion is true, but the reason is false.

4. If both the assertion and reason are false

Correct assertion: 3) If the assertion is true, but the reason is false.

Explanation:

The assertion that the blood in a cockroach lacks a respiratory pigment and appears colorless is true. Cockroaches have an open circulatory system, and their blood is known as hemolymph. It does not contain respiratory pigments like hemoglobin, resulting in a colorless appearance. However, the reason provided, stating that gaseous exchange occurs solely through diffusion in the hemolymph, is false. In cockroaches, the gaseous exchange also takes place through a specialized network of tubules called tracheae, which allow direct air exchange with tissues.

Hence, the correct answer is option (3) If the assertion is true, but the reason is false.

Also Read:

• MCQs on respiratory and Excretory System of Cockroach

• Digestive system of Cockroach

• Muscular Tissue