Hi, welcome to this hall on the topic: circulatory systems in mammals In biology.
Table Of Contents
- Meaning of circulatory systems in mammals
- Types of circulatory system
- Differences between diffusion and circulatory system.
- Revision questions
Circulatory Systems In Mammals
Meaning: Circulatory system refers to the continuous movement or flow of blood round the body involving the heart and the blood vessels.
Types Of Circulatory Systems
Circulatory systems in mammals or animals can be grouped into three major categories:
- Closed and opened circulatory systems,
- Single and double circulatory systems,
- Pulmonary and systemic circulatory systems.
Closed And Opened Circulatory Systems
1. Closed circulatory system: The closed circulatory system are made up of blood vessels called arteries from the heart which branch many times into small units called capillaries but eventually join up with other vessels called veins that are connected to the heart. By this design blood is therefore always confined within the activities of the vessels and the heart and never comes in direct contact with the cells of the body.
Some invertebrates like annelids and all the vertebrates have closed circulatory systems. In mammals for example, there is no mixing of oxygenated and deoxygenated blood in the heart. While oxygenated blood is confined to the left part of the heart, deoxygenated blood is confined to the right side.
2. Opened circulatory system: In this system, the blood vessels lead out of the heart but end in blood spaces called haemocoels within the body cavity. In this spaces, the blood comes into direct contact with the cells after which it is returned to the heart. Arthropods and other molluscs have opened circulatory system.
Single And Double Circulatory Systems
1. Single circulatory system: In a single circulatory system, the blood only passes through the heart once every time it makes one complete movement round the body. This system is common in fish which has only two-chambered hearts – one auricle and one ventricle.
2. Double circulatory system: In double circulatory system, the blood passes through the heart twice every time it makes one complete movement round the body. Each time the blood passes through the heart, it goes through a separate pathway. This is found in mammals.
The double circulation gives rise to the two pathways involved in double circulatory system called pulmonary and systemic system.
Differences between diffusion and circulatory system
Diffusion – Circulatory System
- It occurs in small organisms – It occurs in multicellular organisms.
- It takes place at a slow rate – It takes place at a faster rate
- It is less efficient – It is more efficient.
- It does not require the expenditure of energy – it requires the expenditure of more energy.
Differences between open system and closed system
Open system
- Blood bathes the major organs and tissues directly.
- There are no small blood vessels or capillaries connecting arteries with veins.
- It is found in some molluscs arthropods and lower
- Blood returns directly to the heart.
- The blood ends up in blood spaces (haemocoels) within the body.
Close system
- Fluids with nutrients get to the body tissue from the capillaries as tissue fluids and lymph.
- Smaller blood capillaries unite the small arteries with the veins.
- it is found in annelids vertebrates and some invertebrates.
- Blood returns to the heart through the veins.
- Blood flows via the arteries, veins and capillaries.
Pulmonary And Systemic Circulation
1. Pulmonary circulation: Pulmonary circulation involves the movement of blood between the heart and the lungs. In other words, it involves the movement of blood from the heart to the lungs for oxygenation.
2. Systemic circulation: The systemic circulation involves the movement of blood between the heart and all other parts of the body’s beside the lungs. In one complete circulation, blood from any part of the body enters the heart for the first time, it is then sent to the lungs for oxygenation. From the lungs, it is brought back to the heart for the second time before it can be redistributed to all parts of the body. This is the sequence involved in double circulation.
Pulmonary and systemic circulation can be represented mathematically by linear equations as:
Pulmonary circulation = Heart + Lungs
Systemic circulation = Heart + Body.
The appearance of heart twice in the two equations represents the double circulation of blood in the numbers.
Revision Questions
- What is circulatory system?
- In circulatory systems in mammals, state two types of circulatory Systems.
- Briefly explain closed circulatory system and open circulatory system.
- Explain the differences between open system and close system.