The latissimus dorsi adducts the shoulder while the deltoid abducts the shoulder. Which best describes the relationship between these muscles?
They are fixators.
The deltoid is the prime mover.
They are synergists.
They are antagonists.
QUESTION 38 Which type of capillary is found in skeletal muscles?
Sinusoidal
Continuous.
Discontinuous.
Fenestrated.
The Correct Answer and Explanation is :
Question 1: Relationship Between Latissimus Dorsi and Deltoid Muscles
The correct answer is: They are antagonists.
The latissimus dorsi and deltoid muscles work in opposite directions to move the shoulder joint. The latissimus dorsi primarily adducts the shoulder, meaning it moves the arm towards the body, while the deltoid abducts the shoulder, which means it moves the arm away from the body. These two muscles have opposing actions at the shoulder joint, so they are considered antagonists.
In muscle physiology, antagonistic muscles are pairs that work in opposite directions to produce movement. For example, when one muscle contracts to move a joint in one direction, the antagonist must relax to allow that movement. In this case, when the deltoid contracts to abduct the arm, the latissimus dorsi must relax to permit that motion, and when the latissimus dorsi contracts to adduct the arm, the deltoid must relax to allow for that motion. This antagonistic relationship is crucial for controlled and smooth movement across joints.
While they are not synergists, as they do not assist each other in the same movement, they help provide balance and coordination for shoulder joint actions. They also are not fixators or prime movers in this case, as their role in shoulder movement is defined by their opposing actions rather than stabilizing or producing the main movement.
Question 2: Type of Capillary Found in Skeletal Muscles
The correct answer is: Continuous capillaries.
Skeletal muscles primarily contain continuous capillaries, which are the most common type of capillary found in the body. These capillaries are characterized by a continuous endothelial cell lining with tight junctions, which help regulate the movement of substances between the blood and the muscle tissue.
Continuous capillaries are important in skeletal muscles because they provide an efficient exchange of nutrients, oxygen, and waste products while maintaining a selective barrier to prevent unwanted substances from entering muscle tissue. These capillaries allow for the diffusion of essential molecules required for muscle function and repair, especially during physical activity when the muscles’ metabolic demands are high.
In contrast:
- Fenestrated capillaries have pores in their endothelial lining and are typically found in tissues involved in filtration or absorption, such as the kidneys or the intestines.
- Sinusoidal capillaries are larger, with irregular openings and are found in organs like the liver, spleen, and bone marrow, where large molecules or cells need to pass between the bloodstream and tissue.
- Discontinuous capillaries are similar to sinusoidal but have larger gaps, making them suitable for organs requiring even greater permeability.
The continuous capillaries in skeletal muscles ensure that nutrients and oxygen are efficiently delivered to muscle fibers during exercise, supporting muscle function and recovery.