I think that the best phrase to fit into the blank is a "scientific theory".
A scientific theory is developed through experiments which use the scientific method, and a theory can be improved if additional data is available or if people provide suggestions which make the theory fit the data better.
Endocrine gland - a group of cells that secretes substances into the blood or directly into an organ.
Differ from exocrine glands, endocrine glands have no ducts and secrete products (hormones) directly into blood.
Hormone - a substance produced by cells that helps specific groups of cells to perform specific functions. It is a product of endocrine gland which functions as chemical messengers to stimulate other cells.
Duct – a channel or tube that conveys a substance. It is part of the exocrine glands (such as salivary glands) which makes contact with surface .
Answer:
Explanation:
The central nervous system (CNS) does not have capacity to repair itself but, the PNS or the peripheral nervous system can repair and regenerate itself. The PNS can regenerate its damaged axon only when its cell body or cyton and its neurilemma are intact. The proximal end of the cyton has growth cones. The axon grows from the cones.
