Which of the following statement best describes endocrine glands?

Cells of similar structure and function are grouped together to form a tissue. Tissues can be found in many different types of organisms, including animals and plants. There are four main types of tissues in animals: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. Each type of tissue has a specific function and is composed of specialized cells that work together to perform that function.

An organ is a structure made up of two or more tissues that work together to perform a specific function. A system is a group of organs that work together to perform a specific function. A membrane is a thin layer of tissue that covers a surface or divides a space or organ.

After birth, blood is primarily produced in the red bone marrow of the infant. Red bone marrow is a spongy tissue found in the hollow centers of certain bones, such as the skull, ribs, pelvis, and long bones of the arms and legs. Red bone marrow is responsible for producing red blood cells, white blood cells, and platelets.

In adults, some of the blood production shifts to other organs such as the spleen and liver. However, in infants, the red bone marrow is the main site of blood cell production until about 5 years of age when it begins to gradually transition to the other organs.

The urethra is a tube that connects the bladder to the external environment and serves as a passageway for urine to exit the body during urination. In males, the urethra also serves as a passageway for semen to exit the body during ejaculation, making it a part of both the male reproductive system and the urinary system.

The other options listed are:

a. Ureter - a tube that connects the kidney to the bladder and is a part of the urinary system

c. Testes - the male reproductive organs that produce sperm and are a part of the male reproductive system

d. Epididymis - a tube that connects the testes to the vas deferens and is a part of the male reproductive system.

Blood then carry them to target cells or organs throughout the body. Hormones are chemical messengers that help to regulate various physiological processes such as growth, metabolism, and reproduction. Unlike exocrine glands (option a), which secrete their products into ducts that carry them to external surfaces such as the skin or digestive tract, endocrine glands have no ducts and release their secretions directly into the circulatory system. Salivary glands (option d) are exocrine glands that secrete saliva into ducts leading to the mouth. Option b is also incorrect as it does not accurately describe endocrine glands.