The Endocrine System

Eden Area ROPMedical 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

1. 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 rhythm3. 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 responseto 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

ABBREVIATIONSLOOK UP DEFINITIONS!

1. GDM2. ADH3. FBS4. IDDM5. NIDDM6. GTT (not gtt)7. GH8. TSH