The Endocrine System Eden Area ROP Medical Careers

Endocrine Glands Endocrine glands: Ductless glands; secrete directly into blood Widely distributed throughout the body Secrete hormones: chemical messengers that produce changes in the body Regulate growth/development Regulate metabolism Stimulate other glands Exocrine glands: secrete substances into ducts (EX: sweat gland, sebaceous (oil) glands) NOT part of the endocrine system

Hormones Hormones that are released from the endocrine glands have a target gland in which the hormone has an affect on.

Mechanisms that control hormone secretion Negative feedback: information about the hormone or its effects is fed back to the gland that secretes it 2. Biorhythms: rhythmic alteration in a hormone’s rate of secretion Circadian rhythm: 24-hour rhythm 3. Central nervous system helps control secretion of hormones in two ways: Activation of hypothalamus Stimulation of sympathetic nervous system

The Pituitary Gland Pituitary gland: pea-sized gland located in the center of the brain and attached to hypothalamus Two main parts: Anterior pituitary gland Posterior pituitary gland

The Pituitary Gland (cont’d.) Hypothalamus: controls secretions of the anterior pituitary gland Hypothalamic-hypophyseal portal system: network of capillaries that connects the hypothalamus with the anterior pituitary gland

Pituitary Gland Hormones AKA the “Master gland” because: Secretes hormones that control other glands and affect many organ systems Hormones of the pituitary gland: Prolactin: promotes breast development/milk production after childbirth Growth hormone (GH): essential for the growth/development of body’s tissues, effects length of long bones Thyroid-stimulating hormone (TSH): stimulates thyroid gland to secrete two thyroid hormones Follicle-stimulating hormone (FSH): stimulates ovaries (female), production of sperm (male) Luteinizing Hormone (LH): stimulates ovaries (production of progesterone) and stimulates testes (production of testosterone)

Pituitary Gland Hormones Hormones of the pituitary gland (cont.): Melanocyte-stimulating hormone (MSH):increases the amount of pigment in the skin Oxytocin: stimulates uterine contractions Anti-diuretic Hormone: Retains fluid in the body

Growth Hormone Conditions Dwarfism: insufficient production during childhood Gigantism: Overproduction in childhood Acromegaly: Overproduction during adulthood

Thyroid Gland Largest endocrine gland Located in anterior neck on front and sides of trachea

Thyroid Gland (cont’d.) Thyroid hormones: function to regulate all phases of metabolism, necessary for: Proper functioning of all other hormones Normal maturation of the nervous system Normal growth and development Hormones secreted: Triiodothyronine (T3) & Tetraidothyronine (T4): regulates metabolism Thyrocalcitonin: decreases blood calcium levels (increases calcium storage in bones)

Thyroid Gland (cont’d.) Hypothyroidism: thyroid hormone deficiency resulting in a slowed-down metabolic state Hyperthyroidism: excess of thyroid hormones produces a sped-up metabolic state

Parathyroid Glands Parathyroid glands: Lie along the posterior surface of the thyroid gland Secrete parathyroid hormone (PTH), which increases blood calcium levels (decreases calcium in the bones)

Parathyroid Glands (cont’d.) Hypocalcemia: absence of sufficient calcium causes carpal spasm Hypercalcemia: hyperparathyroidism develops in response to a tumor in the parathyroid gland (causes bone pain and kidney stones)

Adrenal Glands Located above kidneys Two regions: Adrenal medulla: inner region of the adrenal gland, excretes catecholamines Adrenal cortex: outer region of the adrenal gland, secretes steroids

Adrenal Glands (cont’d.) Catecholamines: Epinephrine (Adrenaline): stimulates “fight or flight” response Steroids: (regulate sugar, salt, sex) Cortisol: (sugar) helps maintain blood glucose between meals, “stress hormone” Aldosterone: (salt) regulates blood volume and sodium and potassium levels Sex hormones (small amounts) secondary sex characteristics

Pancreas Long, slender organ that lies across the upper abdomen Functions: exocrine gland and endocrine gland because it secretes hormones (insulin/glucagon) directly into bloodstream. Exocrine function- secretes pancreatic juices that aide in digestion into the digestive system (through a duct) Hormones: Insulin: decreases blood glucose levels Glucagon: increases blood glucose levels

Pancreas (cont’d.) Diabetes mellitus: insulin deficiency or ineffectiveness Signs: Hyperglycemia Glucosuria Polyuria Polydypsia Polyphagia

Diabetes Mellitus Type 1: Insulin Dependent Diabetes Mellitus AKA Juvenile Diabetes Not enough insulin is being produced Type 2: Non-Insulin Dependent Diabetes Mellitus AKA Adult onset Diabetes Mellitus Insulin is produced, but the body is not using it properly Gestational Diabetes Mellitus (GDM): occurs in pregnancy

Gonads (sex glands) Male: testes (located in scrotum) Testosterone: produce sperm Male primary and secondary sex characteristics Female: ovaries (located within the female pelvic cavity) Estrogen Produce ova (eggs) Female primary and secondary sex characteristics Progesterone Affects uterine lining

Thymus Gland Lies in the thoracic cavity behind the sternum Hormones: Thymosins: stimulates the development and maturation of lymphocytes (T-cells)

Pineal Gland (Pineal Body) (“biological clock”) Cone-shaped gland located close to the thalamus in the brain (behind pituitary gland) Hormone: melatonin Controls biorhythms Sleep-wake cycle Delays puberty until appropriate time

The Endocrine glands

Abbreviations Look up definitions! GDM ADH FBS IDDM NIDDM GTT (not gtt) GH TSH