Principles of Anatomy and Physiology Thirteenth Edition Chapter 18 The Endocrine System Copyright © 2012 by John Wiley & Sons, Inc. Gerard J. Tortora Bryan.

Principles of Anatomy and Physiology

Thirteenth Edition

Chapter 18The Endocrine System

Copyright © 2012 by John Wiley & Sons, Inc.

Gerard J. Tortora • Bryan H. Derrickson

Thyroid gland

Trachea

PARATHYROIDGLANDS

PARATHYROID GLANDS(behind thyroid glands)

SKIN

Lung

ADRENALGLANDS

PANCREAS

SMALLINTESTINE

Scrotum

Male

TESTES

Female

OVARY

Uterus

KIDNEY

STOMACH

HEART

THYMUS

TracheaTHYROID GLAND

PITUITARY GLAND

HYPOTHALAMUS

PINEAL GLAND

LIVER

Hormonereceptor

Endocrinecell

Circulating hormone

Bloodcapillary

Distant target cells

(a) Circulating hormones

Paracrine receptor

AutocrinereceptorAutocrine

cell

(b) Local hormones (paracrines and autocrines)

Autocrine

Paracrine

Paracrine cell Nearby target cell

Aldosterone

Steroid hormones

Triiodothyronine (T3)

Thyroid hormones

Norepinephrine

Amines

Oxytocin

Peptides and proteins

A leukotriene (LTB4)

Eicosanoids

Nucleus

Cytosol

Receptor

DNA

mRNA

Ribosome

Newprotein

Activated receptor–hormonecomplex alters gene expression

NewlyFormed mRNAdirects synthesis of specific proteins on ribosomes

New proteins altercell's activity

Target cell

Lipid-soluble hormone diffuses into cell

Blood capillaryFree hormone

Transport protein

2

3

4

1

Activated protein kinases phosphorylatecellular proteins

4

Phosphodiesterase inactivates cAMP

6

Activated adenylatecyclase convertsATP to cAMP

2

Second messenger

Binding of hormone (first messenger) to its receptor activates G protein, which activates adenylate cyclase

1

Adenylate cyclase

Water-solublehormone

Receptor

G protein

ATP cAMP

Protein kinases

Activatedproteinkinases

cAMP serves as asecond messengerto activate proteinkinases

3

Protein

ATP

ADP

Protein - P

Millions of phosphorylatedproteins cause reactions thatproduce physiological responses

5

Blood capillary

Target cell

POSTERIORPITUITARY ANTERIOR

PITUITARY

Infundibulum

Sagittal section of pituitary gland

Hypothalamus

Pituitary gland

Primary plexus ofhypophyseal portal system

HYPOTHALAMUS

Median eminence

Superior hypophysealartery

Hypophyseal portal veins

Sphenoid bone

ANTERIOR PITUITARY

Secondary plexus ofhypophyseal portal system

Anterior hypophysealveins

ANTERIORPOSTERIOR

Inferior hypophyseal artery

(a) Relationship of hypothalamus to pituitary gland

Hypophysealfossa

Capillary plexus ofinfundibular process

POSTERIOR PITUITARY

Posterior hypophysealveins

Infundibulum

Hypophysealportal veins

Hypothalamicneurosecretorycell

(b) Path of releasing and inhibiting hormones

Primary plexus ofhypophyseal portal system

Corticotroph

(c) Histology of anterior pituitary

Lactotroph

Gonadotroph

ThyrotrophSomatotroph

LM all about 65x

Corticotropin-releasinghormone (CRH)

Elevated cortisolinhibits releaseof CRH byhypothalamicneurosecretorycells

Elevated cortisolinhibits releaseof corticotropinby anteriorpituitarycorticotrophs

Cortisol

Adrenalcortex

Corticotropin stimulates secretion of cortisol by adrenal cortex

Corticotropin(ACTH)

Anterior pituitary

CRH stimulates release of corticotropin (ACTH)

Hypothalamus

A low level of hGH andIGFs decreases the rateof glycogen breakdownin the liver and glucoseenters the blood moreslowly

1 6

2 7

3 8

4 9

5 10

hGH and IGFs speedup breakdown of liverglycogen into glucose,which enters the bloodmore rapidly

Blood glucose levelfalls to normal(about 90 mg/100 mL)

Blood glucose levelrises to normal(about 90 mg/100 mL)

If blood glucose continues to decrease,hypoglycemia inhibitsrelease of GHIH

If blood glucosecontinues to increase,hyperglycemia inhibitsrelease of GHRH

GHIH inhibitssecretion ofhGH bysomatotrophs

GHRH stimulatessecretionof hGH bysomatotrophs

hGH

Anteriorpituitary

GHRH GHIH

Low blood glucose (hypoglycemia)stimulates release of

High blood glucose(hyperglycemia)stimulates release of

Human growth hormone (hGH),also known as somatotropin

Liver (and other tissues)

Thyroid-stimulating hormone (TSH), also known as thyrotropin

Thyroid gland

Ovaries

Follicle-stimulating hormone (FSH)

Testes

Ovaries

Luteinizing hormone (LH)

Testes

Mammary glands

Prolactin (PRL)

Adrenalcortex

Adrenocorticotropic hormone (ACTH), also known as corticotropin

Brain

Melanocyte-stimulating hormone (MSH)

Hypothalamus

Infundibulum

Pituitary gland

Neurosecretory cells

HYPOTHALAMUS

Opticchiasm

Capillary plexusof the posteriorpituitary

ANTERIORPITUITARY

Axons of neurosecretory cells

Axon terminal

POSTERIORPITUITARY

Target tissues

1 High blood osmotic pressure stimulates hypothalamic osmoreceptors

5 Low blood osmotic pressure inhibits hypothalamic osmoreceptors

Osmoreceptors2 Osmoreceptors

activate neurosecretorycells that synthesizeand release ADH

6 Inhibition of osmoreceptors reduces or stops ADH secretion

Hypothalamus

3 Nerve impulsesliberate ADH fromaxon terminals inposterior pituitary intobloodstream

ADH

Sudoriferous (sweat) glands decrease water loss by perspiration from skin

Arterioles constrict,which increasesblood pressure

Kidneys retainmore water,which decreasesurine output

4

Oxytocin (OT)

Uterus Mammary glands Kidneys Sudoriferous(sweat) glands

Arterioles

Antidiuretic hormone (ADH) or vasopressin

Hyoid bone

Superior thyroid artery

Superior thyroid vein

Thyroid cartilage of larynx

Internal jugular vein

LEFT LATERAL LOBEOF THYROID GLAND

Common carotid artery

ISTHMUS OF THYROIDGLAND

Vagus (X) nerve

Trachea

Inferior thyroid veins

Sternum

Pyramidal lobe ofthyroid gland

RIGHT LATERAL LOBEOF THYROID GLAND

Middle thyroid vein

Inferior thyroid artery

Subclavian artery

Thyroidgland

Trachea

(a) Anterior view of thyroid gland

Parafollicular (C) cell

Follicular cell

Thyroid follicle

Thyroglobulin (TGB)(colloid)

Basement membrane

500x

(b) Thyroid follicles

LM

LEFT LATERALLOBE

(c) Anterior view of thyroid gland

RIGHT LATERALLOBE

ISTHMUS

Thyroid cartilage of larynx

(d) Anterior view

Cricoid cartilage of larynxRIGHT LATERAL LOBE OF THYROID GLANDLEFT LATERAL LOBE OF THYROID GLANDISTHMUS OF THYROID GLAND

Trachea

Right lung

Arch of aorta

Portion of thyroid follicle

Follicularcell

Blood capillary

ColloidIodinationof tyrosine

4

Couplingof T1 and T2

5

Oxidationof iodide

3

Pinocytosisand digestionof colloid

6

Synthesisof TGB

2

Iodidetrapping

1Secretionof thyroidhormones

7

Transportin blood

8

TyrosineT1 T2

T4

T3Colloid

TGBI2

Secretoryvesicles Lysosome

Golgi complex T3

T4

T3 T4

Rough ER

I– I– I–

I– I– I–

I– I–

I–

I–

I– Bloodplasma

T3

T4

TBG

TBG

Blood capillary

Key:I– = Iodide; I2 = IodineTGB = thyroglobulinTBG = thyroxine-binding globulin

Elevated T3 inhibits release of TRH and TSH (negative feedback)

5

T3 and T4 released into blood by follicular cells

4

Anteriorpituitary

TSH

TRHHypothalamus

Low blood levels of T3 and T4 or low metabolic rate stimulates release of

1

TRH, carriedby hypophysealportal veins toanterior pituitary,stimulatesrelease of TSHby thyrotrophs

2

TSH released intoblood stimulatesthyroid follicular cells

3

Thyroidfollicle

T3 (triiodothyronine) and T4 (thyroxine) or thyroid hormones from follicular cells

Calcitonin (CT) from parafollicular cells

Thyroidfollicle

Follicularcells

Bloodvessel

Thyroidfollicle

Parafollicular cells

Parathyroidglands (behindthyroid gland)

Trachea

Right internal jugular vein

Right common carotid artery

Middle cervical sympathetic ganglion

Thyroid gland

RIGHT SUPERIORPARATHYROID GLAND

Inferior cervicalsympathetic ganglion

RIGHT INFERIORPARATHYROID GLAND

Vagus (X) nerve

Right brachiocephalic vein

Brachiocephalic trunk

Trachea

LEFT SUPERIORPARATHYROID GLAND

(a) Posterior view

Esophagus

LEFT INFERIORPARATHYROID GLAND

Left inferior thyroid artery

Left subclavian artery

Left subclavian vein

Left common carotid artery

Venule

Capillary

Arteriole

Chief cell

Oxyphil cell

240x(b) Parathyroid gland

LM

Blood vesselParafollicular cell

Follicular cellThyroid gland

(c) Portion of thyroid gland (left) and parathyroid gland (right)

Chief cell

Oxyphil cellParathyroid gland

Parathyroid

ThyroidCapsule

Thyroid gland

(d) Posterior view of parathyroid glands

PARATHYROIDGLAND

PARATHYROIDGLAND

PARATHYROID HORMONE (PTH)promotes release of Ca2+ frombone extracellular matrix intoblood and slows loss of Ca2+

in urine, thus increasing bloodCa2+ level.

CALCITONIN inhibitsosteoclasts, thus decreasingblood Ca2+ level.

Low level of Ca2+ in blood stimulates parathyroid gland chief cells to release more PTH.

High level of Ca2+ in blood stimulates thyroid gland parafollicular cells to releasemore CT.

1 3

4 2

CALCITRIOL stimulatesincreased absorption ofCa2+ from foods, whichincreases blood Ca2+ level.

6

PTH also stimulatesthe kidneys to releaseCALCITRIOL.

5

Parathyroid hormone (PTH) from chief cells

Chief cell

Inferior phrenic arteries

Celiac trunkLEFT ADRENAL GLAND

Left middle suprarenal artery

Left inferior suprarenal artery

Left suprarenal vein

Left renal artery

Left renal vein

Right superiorsuprarenal arteries

RIGHT ADRENALGLAND

Right middlesuprarenal artery

Right inferiorsuprarenal artery

Right renal artery

Right renal vein

Kidney

Adrenalglands

Inferior vena cava Abdominal aorta

Superior mesenteric artery

(a) Anterior view

CAPSULE

ADRENALCORTEX

ADRENALMEDULLA

(b) Section through left adrenal gland

Kidney

ADRENAL GLAND

(c) Anterior view of adrenal gland and kidney

Zona glomerulosa secretes mineralocorticoids, mainly aldosterone

Capsule

(d) Subdivisions of adrenal gland

Adrenal cortex:

Zona fasciculata secretes glucocorticoids, mainly cortisol

Zona reticularis secretes androgens

Adrenal medulla chromaffin cells secrete epinephrine and norepinephrine (NE)

50xLM

Dehydration,Na+ deficiency,or hemorrhage

Decrease inblood volume

Decrease inblood volume

Angiotensinogen

Increased renin

Increasedangiotensin I

Increasedangiotensin II

Blood pressureincreases untilit returns to normal

Vasoconstrictionof arterioles

Increased bloodvolume

IncreasedK+ inextracellularfluid

In kidneys, increased Na+

and water reabsorptionand increased secretion ofK+ and H+ into urine

Increasedaldosterone

Juxtaglomerularcells of kidneys

Liver

ACEACE

Lungs (ACE = angiotensin converting enzyme)Lungs (ACE = angiotensin converting enzyme)

AdrenalcortexAdrenalcortex

1

2

3

6

8 7

9

5

4

15

10

11 12

16

13

14

Some stimulus disruptshomeostasis by

Decreasing

Glucocorticoid levelin blood

Neurosecretorycells inhypothalamus

Receptors

Input Increased CRH anddecreased cortisol

Corticotrophs inanterior pituitary

Control center

Return to homeostasiswhen response bringsglucocorticoid level inblood back to normal

Output Increased ACTH

Cells of zonafasciculata inadrenal cortexsecrete glucocorticoids

Effectors

Increased glucocorticoidlevel in blood

Androgens (mainly dehydroepiandrosterone, or DHEA) from zona reticularis cells

Epinephrine and norepinephrine from chromaffin cells

Adrenalcortex

Adrenalmedulla

Common hepatic artery

Abdominal aorta

Celiac trunk

Splenic artery

Spleen(elevated)

TAIL OF PANCREAS

BODY OF PANCREAS

Inferior pancreatic artery

Superior mesenteric artery

Inferior pancreaticoduodenal artery

Gastroduodenal artery

Dorsal pancreatic artery

Anterior pancreaticoduodenalarteryDuodenum of small intestine

HEAD OF PANCREAS

(a) Anterior view

PancreasKidney

Blood capillary

(b) Pancreatic islet and surrounding acini

Exocrine acini

Alpha cell(secretes glucagon)

Beta cell(secretes insulin)

Delta cell(secretes somatostatin)

F cell (secretespancreatic polypeptide)

Pancreaticislet

40xLM

200xLM

Exocrineacinus

Betacell

Alphacell

Pancreaticduct

(c) Pancreatic islet and surrounding acini

Duodenum(cut open)

Pancreas

(d) Anterior view of pancreas dissected to reveal pancreatic duct

Low blood glucose(hypoglycemia) stimulates alpha cells to secrete

1 High blood glucose (hyperglycemia) stimulates

beta cells to secrete

5

Glucagon acts on hepatocytes (liver cells) to:

2

Glucose released by hepatocytes raises blood glucose level to normal

3

If blood glucosecontinues to rise, hyperglycemia inhibitsrelease of glucagon

4

• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)

Insulin acts on various body cells to:

• accelerate facilitated diffusion of glucose into cells• speed conversion of glucose into glycogen (glycogenesis)• increase uptake of amino acids and increase protein synthesis• speed synthesis of fatty acids (lipogenesis)• slow glycogenolysis• slow gluconeogenesis

Blood glucose level falls

If blood glucose continuesto fall, hypoglycemiainhibits release of insulin

6

7

8

INSULINGLUCAGON

Glucagon from alphacells of pancreatic islets

Insulin from beta cellsof pancreatic islets

Pancreatic polypeptide fromF cells of pancreatic islets

Somatostatin from deltacells of pancreatic islets

Alpha cell

Delta cell

Beta cell

F cell

Estrogens and progesterone

Ovaries

Testosterone

Testes

STRESS RESPONSES

1. Increased heart rate and force of beat

2. Constriction of blood vessels of most viscera and skin

3. Dilation of blood vessels of heart, lungs, brain, and skeletal muscles

4. Contraction of spleen 5. Conversion of glycogen

into glucose in liver 6. Sweating 7. Dilation of airways 8. Decrease in digestive

activities 9. Water retention and

elevated blood pressure

STRESSORSstimulate

HypothalamusCRHGHRHTRH

Nerveimpulses

Sympathetic centersin spinal cord Anterior

pituitary

Sympathetic nerves

TSHhGHACTH

Adrenalmedulla

Epinephrine andnorepinephrine

Visceral effectors

ACTH hGH TSH

Cortisol IGFsThyroid hormones

(T3 and T4)

STRESS RESPONSESLipolysisGluconeogenesisProtein catabolismSensitized blood vesselsReduced inflammation

STRESS RESPONSESLipolysisGlycogenolysis

STRESS RESPONSESIncreased useof glucose toproduce ATP

Adrenalcortex

Liver Thyroidgland

Supplementand prolong“fight-or-flight”responses

(a) Fight-or-flight responses (b) Resistance reaction

Key:CRH = Corticotropin-releasing hormoneACTH = Adrenocorticotropic hormoneGHRH = Growth hormone–releasing hormonehGH = Human growth hormoneTRH = Thyrotropin-releasing hormoneTSH = Thyroid-stimulating hormone

Stomodeum

Hypophyseal(Rathke’s) pouch

Neurohypophyseal bud

Hypothalamus

Thyroid diverticulumRespiratory diverticulum

Esophagus

Pharyngeal pouches

4 3 2 1

(a) Location of neurohypophyseal bud, hypophyseal (Rathke’s) pouch, thyroid diverticulum, and pharyngeal pouches in 28-day embryo

Neurohypophyseal bud

Mouth cavity

Hypophyseal(Rathke’s)

pouch

Infundibulum Infundibulum

Pars intermedia

Hypothalamus

Infundibulum

Anteriorpituitary

Posterior pituitaryMesenchyme

(b) Development of pituitary gland between 5 and 16 weeks

(a) A 22-year-old man with pituitary giantism shown beside his identical twin

(b) Acromegaly (excess hGH during adulthood)

(c) Goiter (enlargement of thyroid gland)

(d) Exophthalmos (excess thyroid hormones, as in Graves’ disease)

(e) Cushing’s syndrome (excess glucocorticoids)