Endocrine System

Endocrine System

PituitaryGland

It is just about the size of pea. It hangs from the hypothalamus. It is considered as the most important of the endocrine glands because it controls the activities of the other endocrine glands as well as other body processes.This gland produces the growth hormone which stimulates cell division and the growth of muscle an bones.

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Pineal Gland

It is an outgrowth of the brain. It produces melatonin, a hormone that regulates the body’s day-night cycles. During the day, when more of this hormone produced, the body is active. At night, when less of the hormone produced, the body feels drowsy.

Thyroid GlandIt is located at the base of the neck.

This gland produces thyroxine that controls the rate at which the body cells use food to release energy. Another hormone this gland produces is calcitonin. Which reduces blood calcium levels by causing calcium to be deposited in the bones. Thyroid hormones also help in regulating body growth and development.

Parathyroid GlandsThese are two pairs of pea-sized glands

found near the thyroid gland. The hormone produce by this glands helps control the level of calcium in blood. If the calcium level is low, the glands increase their hormone production which cause the bones to release more calcium in the blood. If the blood level of calcium is too high, the glands lessen their production of the hormone.

Thymus Glands

Is located in the upper thorax behind the breast bone and extends below the thyroid gland. The thymus is large in infants and children but smaller in adults. In old age, the thymus becomes mostly tissues and fat.Thy thymus forms parts of the body’s immune system. The function of this gland is to cause lymphocytes (WBC) to become T cells-the cells which become part of the body’s defense against infection.

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Adrenal GlandThese are a pair of con-shaped glands, each on

top of a kidney. It has two parts-the cortex and the medulla. The cortex produces hormones that affect the body metabolism. Metabolism is a process by which the body converts food into energy and living tissue. The hormones produced by the adrenals prepare the body for stress. For example, epinephrine (also called adrenaline) increases pulse rate and rate of breathing; it also speeds up the conversion of food into energy.

Pancreatic IsletsThe pancreas is a long, soft organ that lies

transversely along the posterior abdominal wall, posterior to the stomach, and extends from the region of the duodenum to the spleen. This gland has an exocrine portion that secretes digestive enzymes that are carried through a duct to the duodenum. The endocrine portion consists of the pancreatic islets, which secrete glucagons and insulin.

Alpha cells in the pancreatic islets secrete the hormone glucagons in response to a low concentration of glucose in the blood. Beta cells in the pancreatic islets secrete the hormone insulin in response to a high concentration of glucose in the blood.

Pancreas—Islets of Langerhans

GonadsThe gonads are the testes in the male and the

ovaries in the female.

TestesMale sex hormones, as a group, are called androgens. The

principal androgen is testosterone, which is secreted by the testes. A small amount is also produced by the adrenal cortex. Production of testosterone begins during fetal development, continues for a short time after birth, nearly ceases during childhood, and then resumes at puberty. This steroid hormone is responsible for:

The growth and development of the male reproductive structures

Increased skeletal and muscular growthEnlargement of the larynx accompanied by voice changesGrowth and distribution of body hairIncreased male sexual driveTestosterone secretion is regulated by a negative feedback

system that involves releasing hormones from the hypothalamus and gonadotropins from the anterior pituitary.

Male Testis

OvariesTwo groups of female sex hormones are produced in the

ovaries, the estrogens and progesterone. These steroid hormones contribute to the development and function of the female reproductive organs and sex characteristics. At the onset of puberty, estrogens promotes:

The development of the breastsDistribution of fat evidenced in the hips, legs, and breastMaturation of reproductive organs such as the uterus and

vagina

Progesterone causes the uterine lining to thicken in preparation for pregnancy. Together, progesterone and estrogens are responsible for the changes that occur in the uterus during the female menstrual cycle.

Female Ovaries

Diseases of the Endocrine System

Hypothyroidsm

Hyperthyroidsm

Cretinism Gigantism & Dwarfism

Diabetes Mellitus

Hypofunction of Testes and

Ovaries