Transcript Orientation to the Human Body
The Endocrine System
Glands and Hormones
Anatomy & Physiology II Chapter 12
Endocrine System Components
endocrine system - glands, tissues, and cells that secrete hormones endocrinology – the study of this system and the diagnosis and treatment of its disorders endocrine glands – organs that are traditional sources of hormones hormones - chemical messengers that are transported by the bloodstream and stimulate physiological responses in cells of another tissue or organ, often a considerable distance away
Endocrine Organs
Pineal gland Hypothalamus Pituitary gland Thyroid gland Thymus Adrenal gland Pancreas Parathyroid glands Posterior view Gonads: Ovary (female) Testis (male) Trachea
major organs of endocrine system
The Endocrine System
Consists of a group of glands that produce hormones Works with nervous system to control and coordinate all other body systems Affects body systems by chemical stimuli
Hormones
Chemical messengers with regulatory effects on cells or organs Hormones from endocrine glands are released directly into tissue fluids; not through ducts Some affect many tissues ◦ Growth hormone ◦ ◦ Thyroid hormone Insulin Some affect a specific tissue (target tissue) ◦ Thyroid-stimulating hormone (TSH) ◦ Adrenocorticotropic hormone (ACTH)
Hormone Chemistry
Amino acid compounds ◦ Proteins or related compounds ◦ All hormones except steroids ◦ ◦ Lipids ◦ Made of fatty acids ◦ Most are steroids, derived from the steroid cholesterol Produced in adrenal cortex and sex glands Prostaglandins are also lipids
Hormone Regulation
◦ ◦ Negative feedback (most common) ◦ Endocrine gland oversecretes hormone Tissue becomes too active Tissue negatively effects gland to decrease secretion Positive feedback ◦ Hormone response produces more hormone Rhythmic pattern
Other Hormone Secreting Tissues
Tissues other than endocrine glands also secrete hormones Brain Digestive organs Kidney
The Endocrine Glands
The Pituitary
Pituitary (hypophysis) gland Master gland Releases hormones that affect working of other glands Controlled by hypothalamus
The hypothalamus, pituitary gland, and target tissues
Arrows indicate the hormones’ target issues and feedback pathways.
ZOOMING IN • What two structures does the infundibulum connect?
Control of the Pituitary
Hypothalamus Sends releasing hormones (RH) and inhibiting hormones (IH) ◦ Hormones stimulate and suppress anterior pituitary secretions ◦ ◦ Produces antidiuretic hormone (ADH) and oxytocin Stored in posterior pituitary Nerve impulses stimulate secretions
Control of Pituitary: Feedback from Target Organs
TRH 1 TSH 2 + 5
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+
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6 3 Negative feedback inhibition 4 Target organs +
negative feedback increased target organ hormone levels inhibits release of hormones
Thyroid hormone + Stimulatory effect
–
Inhibitory effect
•
positive feedback -
stretching of uterus increases OT release, causes contractions, causing more stretching of uterus, etc. until delivery
Hormones of the Anterior Lobe
Growth hormone (GH) or somatotropic Thyroid-stimulating hormone (TSH) or thyrotropic Adrenocorticotropic hormone Prolactin (PRL) Gonadotropins ◦ Follicle-stimulating hormone (FSH) ◦ Luteinizing hormone (LH)
Hormones of the Posterior Lobe
Antidiuretic hormone (ADH) Oxytocin
Tumors of the Pituitary
Excessive number of tumor growth hormone (GH) cells in childhood ◦ Gigantism Overactive GH-producing tumor cells in adulthood ◦ Acromegaly Tumors that destroy secreting tissues ◦ Underactivity
The Thyroid Gland
Largest endocrine gland Lateral lobes on either side of larynx Connecting band (isthmus) Enclosed by connective tissue capsule
Hormones of the Thyroid Gland
Thyroxine (T4) ◦ Principle hormone ◦ Increases energy and protein metabolism rate Triiodothyronine (T3) ◦ Increases energy and protein metabolism rate Calcitonin ◦ Regulates calcium metabolism ◦ Works with parathyroid hormone and vitamin D
Thyroid Gland Disorders
Hypothyroidism ◦ congenital hypothyroidism (decreased TH) hyposecretion present a birth (formerly cretinism) ◦ myxedema (decreased TH) ◦ adult hypothyroidism ◦ treat with oral thyroid hormone Hyperthyroidism ◦ Graves disease ◦ Thyroid storm Thyroiditis ◦ Hashimoto disease
Thyroid Gland Disorders
goiter – any pathological enlargement of the thyroid gland ◦ endemic goiter ◦ dietary iodine deficiency, no TH, no - feedback, increased TSH stimulates hypertrophy toxic goiter (Graves disease) autoantibodies mimic the effect of TSH on the thyroid causing hypersecretion overgrown thyroid produces functional TH
Endemic Goiter
Tests of Thyroid Function
Blood tests ◦ Uptake of radioactive iodine ◦ Thyroid-stimulating hormone level Oral radioactive iodine to measure accumulation in thyroid
The Parathyroid Glands
Four glands in posterior capsule of thyroid Secrete parathyroid hormone (PTH) ◦ Works with calcitonin to regulate calcium metabolism
Calcium Metabolism
Calcium balance requires Calcitriol (dihydroxycholecalciferol) ◦ Produced by modifying vitamin D in liver then in kidney Parathyroid hormone Calcitonin
Disorders of the Parathyroid Glands
Tetany ◦ Inadequate production of parathyroid hormone (PTH) Fragile bones and kidney stones ◦ Excess production of parathyroid hormone (PTH)
The Adrenal Glands
Two small glands on top of kidneys Each gland has two parts that act as separate glands ◦ Medulla ◦ Cortex
Hormones from the Adrenal Medulla
Fight-or-flight hormones Epinephrine (adrenaline) Norepinephrine (noradrenalin)
Hormones from the Adrenal Cortex
Glucocorticoids ◦ Cortisol or hydrocortisone Mineralocorticoids ◦ Aldosterone Sex hormones
Disorders of the Adrenal Cortex
Addison disease ◦ Hypofunction of adrenal cortex Aldosteronism ◦ Hyperfunction of adrenal cortex resulting in excess secretion of aldosterone Cushing syndrome ◦ Hypersecretion of cortisol Adrenogenital Syndrome (AGS) ◦ Hypersecretion of adrenal androgen
Adrenal Disorders
Cushing syndrome - excess cortisol secretion ◦ hyperglycemia, hypertension, weakness, edema ◦ rapid muscle and bone loss due to protein catabolism ◦ abnormal fat deposition moon face and buffalo hump
Adrenal Disorders
adrenogenital syndrome
(AGS) ◦ adrenal androgen hypersecretion (accompanies Cushing) ◦ enlargement of external sexual organs in children and early onset of puberty newborn girls exhibit masculinized genitalia ◦ masculinizing effects on women increased body hair, deeper voice and beard growth
The Pancreas and Its Hormones
Islets of Langerhans are specialized pancreas cells that secrete Insulin ◦ Lowers blood sugar level ◦ Stimulates protein synthesis (manufacture of amino acids into protein) Glucagon ◦ Increases blood sugar
Bile duct
Pancreas
Tail of pancreas Pancreatic islet Exocrine acinus Pancreatic Duodenum Head of ducts pancreas Beta cell Alpha cell Delta cell Pancreatic islet
c: © Ed Reschke exocrine digestive gland and endocrine cell clusters (pancreatic islets) found retroperitoneal, inferior and posterior to stomach.
Pancreatic Hormones
1-2 million pancreatic islets (Islets of Langerhans) produce hormones ◦ other 98% of pancreas cells produces digestive enzymes Insulin - secreted by B or beta ( ) cells ◦ secreted during and after meal when glucose and amino acid blood levels are rising ◦ stimulates cells to absorb these nutrients and store or metabolize them lowering blood glucose levels promotes synthesis glycogen, fat, and protein suppresses use of already stored fuels brain, liver, kidneys and RBCs absorb glucose without insulin, but other tissues require insulin ◦ insufficiency or inaction is cause of diabetes mellitus
Pancreatic Hormones
glucagon – secreted by A or alpha ( ) cells ◦ released between meals when blood glucose concentration is falling ◦ in liver, stimulates gluconeogenesis, glycogenolysis, and the release of glucose into the circulation raising blood glucose level ◦ ◦ glucagon also released to rising amino acid levels in blood, promotes amino acid absorption, and provides cells with raw material for gluconeogenesis Somatostatin - secreted by D or delta ( ) cells ◦ in adipose tissue, stimulates fat catabolism and release of free fatty acids partially suppresses secretion of glucagon and insulin gastrin - secreted by G cells ◦ stimulates stomach acid secretion, motility and emptying22
Pancreatic Hormones
hyperglycemic hormones raise blood glucose concentration ◦ glucagon, growth hormone, epinephrine, norepinephrine, cortisol, and corticosterone hypoglycemic hormones lower blood glucose ◦ insulin
Diabetes Mellitus
most prevalent metabolic disease in world ◦ disruption of metabolism due to hyposecretion or inaction of insulin ◦ symptoms: polyuria (excess urine output), polydipsia (intense thirst) and polyphagia (hunger) revealed by elevated blood glucose, glucose in urine and ketones in the urine transport maximum – limit to how fast the glucose transporters can work to reabsorb ◦ excess glucose enters urine and water follows it causes polyuria, dehydration, and thirst
Types of Diabetes Mellitus
Type 1 (IDDM) – 5 to 10% of cases in US ◦ insulin is always used to treat Type 1 insulin injections, insulin pump, or dry insulin inhaler monitoring blood glucose levels and controlled diet ◦ autoantibodies attack and destroy pancreatic beta cells ◦ ◦ Type 2 (NIDDM) – 90 to 95% of diabetics ◦ problem is insulin resistance failure of target cells to respond to insulin risk factors are heredity, age (40+),obesity, and ethnicity treated with weight loss program and exercise since: loss of muscle mass causes difficulty with regulation of glycemia adipose signals interfere with glucose uptake into most cells ◦ oral medications improve insulin secretion or target cell sensitivity
Pathology of Diabetes
pathogenesis: ◦ cells cannot absorb glucose, must rely on fat and proteins for energy needs ◦ weight loss and weakness fat catabolism increases free fatty acids and ketones in blood ketonuria promotes osmotic diuresis, loss of Na + irregular heartbeat, and neurological issues and K ketoacidosis occurs as ketones decrease blood pH deep, gasping breathing and diabetic coma are terminal result +,
Pathology of Diabetes
chronic pathology (chronic hyperglycemia) ◦ leads to neuropathy and cardiovascular damage from atherosclerosis and microvascular disease arterial damage in retina and kidneys (common in type I), atherosclerosis leads to heart failure (common in type II) diabetic neuropathy – nerve damage from impoverished blood flow can lead to erectile dysfunction, incontinence, poor wound healing, and loss of sensation from area
Metabolic Syndrome
Also called syndrome X or insulin-resistance syndrome Related to type 2 diabetes High state of hyperglycemia and obesity Caused by insulin resistance in combination with high plasma glyceride levels, low HDL levels, and hypertension Treated with weight loss, diet, exercise; drugs to lower blood pressure and cholesterol; drugs to lower insulin resistance
The Sex Glands
Ovaries and testes produce hormones to Develop sexual characteristics Maintain reproductive organs
Hormones of the Sex Glands
Male sex hormone ◦ Testosterone Female sex hormones ◦ Estrogen ◦ Progesterone
The Thymus Gland
Mass of lymphoid tissue in upper chest superior to heart Important in development of immunity Produces thymosin ◦ Assists in maturity of T lymphocytes
The Pineal Gland
Cone-shaped structure posterior to midbrain Produces melatonin ◦ Influences sleep–wake cycles ◦ Appears to delay onset of puberty
Other Hormone-Producing Tissues
Substances that regulate body actions are also produced by Stomach Small intestine Kidneys Brain Atria of heart Placenta
Prostaglandins
Group of hormones made by most body tissues Produced, act, and rapidly inactivated in or close to origin Constrict structures Dilate structures Promote inflammation
Hormones and Treatment
Hormones are extracted from animal tissue, manufactured in the lab, or genetically engineered Growth hormone Insulin Adrenal steroids Epinephrine (adrenaline) Thyroid hormones Oxytocin Androgens Estrogen and progesterone
Hormones and Stress
Stress response involves both nervous and endocrine system Hormones released during stress help body cope Unchecked levels of hormones can harm body
Aging and the Endocrine System
Pancreas ◦ Adult-onset diabetes mellitus Thyroid ◦ Decreased hormone secretion Pituitary ◦ Decreased bone mass