Question
The diagram shows a section of a human vein.
Answer/Explanation
▶️Answer/Explanation
A
The labelled part is Valve
In a section of a human vein, the function of the valves is to make sure that the blood flows through the heart in the correct direction. Veins are blood vessels that carry deoxygenated blood back to the heart from various parts of the body. To ensure that blood flows efficiently and does not flow backward, veins are equipped with one-way valves.
These valves are flap-like structures located inside the vein. They open in response to the pressure of blood flowing towards the heart, allowing the blood to pass through. However, when the blood tries to flow backward, the valves close, preventing the backflow. This one-way flow of blood is essential in maintaining the circulatory system’s efficiency and preventing the pooling of blood in the extremities.
The contraction of skeletal muscles around the veins also plays a role in aiding the blood flow back to the heart. When muscles contract during movement, they squeeze the veins, pushing the blood towards the heart. This mechanism, combined with the action of the valves, helps maintain a steady and controlled blood flow in the circulatory system.
Question
The diagram shows cross-sections through three types of blood vessel, not drawn to the same
scale.
▶️Answer/Explanation
C
Vein cross-section (W):
Veins are blood vessels that carry blood toward the heart. Their cross-sections typically show thin walls with three main layers: the tunica intima (innermost layer), the tunica media (middle layer), and the tunica externa (outermost layer). Veins have larger lumens (the central opening through which blood flows) compared to arteries, but they lack the thick and elastic walls found in arteries.
Capillary cross-section (X):
Capillaries are the smallest blood vessels and serve as the sites of exchange between blood and surrounding tissues. Their cross-sections are extremely narrow and consist of a single layer of endothelial cells. They lack the tunica media and tunica externa layers found in arteries and veins.
In summary, the cross-section with thin walls and three main layers (tunica intima, tunica media, and tunica externa) is likely to be from a vein. The cross-section with a single layer of endothelial cells is likely to be from a capillary.
Question
Read the following sentence.
In order to prevent the human body from losing heat, the arterioles supplying the skin become narrow.
Which process does this sentence describe?
A constriction
B shivering
C sweating
D vasodilation
▶️Answer/Explanation
A
The process described in the sentence is option A: constriction.
Constriction of the arterioles supplying the skin is a mechanism used by the body to reduce heat loss in cold conditions. When the arterioles constrict, less blood flows near the skin’s surface, reducing the amount of heat that can be lost to the environment. This helps to conserve body heat and maintain the core body temperature.
Question
Which structures in plants and in humans normally carry amino acids?
▶️Answer/Explanation
A
In both plants and humans, amino acids are transported and carried through the circulatory systems.
In plants:
- Phloem: The phloem is the vascular tissue responsible for transporting sugars, organic compounds, and amino acids produced during photosynthesis from the leaves to other parts of the plant, including roots, stems, flowers, and fruits. This transport of amino acids and other nutrients is essential for plant growth and development.
- Arteries: Amino acids are transported in the bloodstream. After digestion and absorption of proteins from the diet, amino acids are released into the bloodstream from the small intestine. From there, they are carried by the blood to various tissues and organs throughout the body. Amino acids are also taken up by specific cells and tissues where they are used for various metabolic processes, protein synthesis, and other essential functions.
Ureters doesn’t play any role.
Question
Which blood vessel contains valves?
A arteriole
B capillary
C renal artery
D renal vein
Answer/Explanation
The correct answer is D) renal vein.
Valves are structures that help prevent the backflow of blood within certain blood vessels, particularly in veins. Veins, in general, contain valves to ensure that blood flows in one direction towards the heart. This is important because veins have lower pressure compared to arteries, and valves help maintain the blood flow towards the heart despite gravity and other factors that could potentially cause backflow.
The renal vein specifically carries blood from the kidneys back to the heart. It contains valves to prevent the backward flow of blood and assist in maintaining the unidirectional flow towards the heart. The other options, arteriole and capillary, do not typically have valves present.