Animal Sciences

- The shoulder is associated with the humerus, a long bone involved in upper arm movement.
- The thigh involves the femur, the longest and strongest bone in the body.
- The wrist consists of carpal bones, small bones that provide flexibility to the hand.
- The ankle comprises tarsal bones, which form the skeletal structure of the foot’s proximal region.

In myelinated axons, the action potential jumps between the Nodes of Ranvier in a process called Saltatory conduction. The myelin sheath acts as an insulator, preventing the signal from dissipating and significantly increasing the speed of nerve impulse transmission. This mechanism is far more efficient than continuous conduction in unmyelinated fibers.

Calcitonin is a peptide hormone secreted by the parafollicular cells (C cells) of the thyroid gland. Its primary function is to regulate blood calcium levels by inhibiting osteoclast activity, thereby reducing bone resorption and lowering calcium concentrations in the bloodstream. This hormone is particularly important in preventing hypercalcemia.

Lymphoid stem cells in the bone marrow give rise to two primary types of immune cells: natural killer (NK) cells and B lymphocytes. NK cells are part of the innate immune system, providing rapid responses to infected or cancerous cells. B lymphocytes, part of the adaptive immune system, produce antibodies. Platelets and neutrophils, on the other hand, originate from myeloid stem cells, not lymphoid stem cells.

The foramen ovale is a vital part of fetal circulation, allowing blood to flow directly from the right atrium to the left atrium, bypassing the non-functional fetal lungs. After birth, the foramen ovale closes due to increased pressure in the left atrium, leaving a depression called the fossa ovalis.