Mammalian circulatory system and blood vessels
Select Lesson
Exam Board
Select an option
Practical skills
Control systems
Origins of genetic variation
Modern genetics
Microbiology and pathogens
Energy for biological processes
Exchange and transport
Surface area to volume ratio and gas exchange
Cell membrane structure and permeability
Simple and facilitated diffusion
Osmosis and investigating water potential
Active transport and co-transport
Gas exchange in fish, insects, plants and humans
Mammalian circulatory system and blood vessels
Haemoglobin and the Bohr effect
Heart structure and the cardiac cycle
Heart rate regulation and electrocardiograms
Transport in plants - xylem
Transport in plants - phloem
Classification and biodiversity
Cells, viruses and reproduction of living things
Biological molecules
Carbohydrates: types, structure and function
The structure and function of lipids
The structure and function of proteins
Nucleic acids: DNA and RNA
DNA replication
DNA, genes and chromosomes
RNA, protein synthesis and the genetic code
Enzymes: activation energy, properties and structure
Factors affecting enzyme activity
Inorganic ions: iron, hydrogen, sodium and phosphate
The properties and functions of water
Explainer Video
Summary
Mammalian circulatory system and blood vessels
In a nutshell
Large organisms have a small surface area to volume ratio, so substances cannot enter or exit in sufficient quantities or by simple diffusion. These organisms need transport systems, like the circulatory system, to move substances from exchange surfaces to cells and to remove waste.
Mammalian circulatory system
Mammals have a closed, double circulatory system. This means that blood is enclosed in vessels and that it passes through the heart twice for each complete circuit around the body.
The first passage takes deoxygenated blood from the heart to the lungs and back to the heart. The other circulates oxygenated blood around the body and back to the heart.
| 1. | Brain, head and neck | 10. | Vena cava |
| 2. | Arms | 11. | Pulmonary vein |
| 3. | Lungs | 12. | Hepatic vein |
| 4. | Heart | 13. | Hepatic artery |
| 5. | Liver | 14. | Hepatic portal vein |
| 6. | Gut | 15. | Renal vein |
| 7. | Kidneys | 16. | Renal artery |
| 8. | Pulmonary artery | 17. | Blood flow from lower limbs |
| 9. | Aorta | 18. | Blood flow to lower limbs |
Passage through the circulatory system
| 1. | Deoxygenated blood is pumped from the heart to the lungs through the pulmonary artery. |
| 2. | Oxygenated blood leaves the lungs and travels to the heart through the pulmonary vein. |
| 3. | Blood is pumped from the heart to the body through the aorta. |
| 4. | Blood travels from the body to the kidneys through the renal vein. |
| 5. | Blood travels from the kidneys towards the heart through the renal artery. |
| 6. | Blood travels from the body to the heart through the vena cava. |
| 7. | Deoxygenated blood is transported from the liver to the heart through the hepatic vein. |
| 8. | Oxygenated blood is transported from the heart to the liver through the hepatic artery. |
| 9. | Deoxygenated blood travels from the gastrointestinal tract, gallbladder, pancreas and spleen to the liver through the hepatic portal vein. |
Blood vessels
There are four types of blood vessels; arteries, arterioles, veins and capillaries.
Arteries
Most arteries carry oxygenated blood from the heart to the body, with the exception of the pulmonary artery which carries deoxygenated blood. Arteries have elastic tissue in their outer walls that allow them to stretch and recoil as the heart beats. They also have a thick muscular middle layer of smooth muscle that allows the artery to constrict, dilate and withstand high blood pressure. Arteries also have a folded endothelium which allows them to stretch to accommodate blood flow.
Arterioles
Arteries eventually narrow into arterioles which direct blood to where it is needed in the body. Muscles in the arterioles are able to contract and restrict blood flow or relax to allow maximum blood flow.
Veins
Veins carry deoxygenated blood from the body to the heart, except for the pulmonary vein which carries oxygenated blood. Veins have less elastic tissue in their walls and have a thinner muscular middle layer as blood returns to the heart under low pressure. Veins have valves that prevent blood flowing backwards.
Capillaries
Arterioles narrow into capillaries which are adapted for substance exchange with cells. They are one cell thick and located near exchange surfaces which reduces the diffusion distance between the capillary and the cell. Lots of capillaries are arranged into capillary beds which increases the surface area for exchange.
Tissue fluid
Definition
Tissue fluid is the watery substance that surrounds cells. It is composed of small molecules from the blood plasma.
Examples
Oxygen, water and nutrients.
The cells will take in some substances, like oxygen and nutrients, from the tissue fluid and release their metabolic waste into it. This process occurs in capillary beds and it is described below.
| A. | The hydrostatic pressure is greatest nearer the arteries and higher in the capillaries compared to the tissue fluid. |
| B. | The hydrostatic pressure difference results in the expulsion of fluid from the capillaries into the surrounding tissues. This forms tissue fluid. |
| C. | The expulsion of fluid lowers the hydrostatic pressure in the capillaries. This means that the hydrostatic pressure is lowest near the veins. |
| D. | The water potential is lower in the capillaries than in the tissue fluid. Therefore, water enters the capillaries by osmosis. |
| E. | Any excess tissue fluid will be drained into the lymphatic system. |
FAQs - Frequently Asked Questions
What is tissue fluid?
Tissue fluid is the watery substance that surrounds cells. It is composed of small molecules from the blood plasma.
Which kinds of organisms have a circulatory system?
Large organisms have a small surface area to volume ratio, so substances cannot enter or exit in sufficient quantities or speed by simple diffusion. These organisms need transport systems, like the circulatory system, to move substances from exchange surfaces to cells and to remove waste.
What circulatory system do mammals have?
Mammals have a closed, double circulatory system. This means that blood is enclosed in vessels and that it passes through the heart twice for each complete circuit around the body.