Mosby items and derived items © 2007, 2003 by Mosby, Inc.Slide 1 Chapter 16 Endocrine System.

Mosby items and derived items © 2007, 2003 by Mosby, Inc.

Chapter 16Chapter 16Endocrine SystemEndocrine System


Introduction Introduction

• The endocrine and nervous systems function to achieve The endocrine and nervous systems function to achieve and maintain homeostasis (Table 16-1)and maintain homeostasis (Table 16-1)

• When the two systems work together as one system, When the two systems work together as one system, referred to as the neuroendocrine system, they perform referred to as the neuroendocrine system, they perform the same general functions: communication, integration, the same general functions: communication, integration, and controland control

• In the endocrine system, secreting cells send hormone In the endocrine system, secreting cells send hormone molecules via the blood to specific target cells contained in molecules via the blood to specific target cells contained in target tissues or target organstarget tissues or target organs


IntroductionIntroduction

• Hormones—carried to almost every point in the body; Hormones—carried to almost every point in the body; can regulate most cells; effects work more slowly and can regulate most cells; effects work more slowly and last longer than those of neurotransmitterslast longer than those of neurotransmitters

• Endocrine glands are “ductless glands”; many are Endocrine glands are “ductless glands”; many are made of glandular epithelium whose cells made of glandular epithelium whose cells manufacture and secrete hormones; a few endocrine manufacture and secrete hormones; a few endocrine glands are made of neurosecretory tissueglands are made of neurosecretory tissue

• Glands of the endocrine system are widely scattered Glands of the endocrine system are widely scattered throughout the body (Figure 16-2; Table 16-2)throughout the body (Figure 16-2; Table 16-2)


Hormones Hormones

• Classification of hormonesClassification of hormones Classification by general functionClassification by general function

• Tropic hormones—target other endocrine glands and Tropic hormones—target other endocrine glands and stimulate their growth and secretionstimulate their growth and secretion

• Sex hormones—target reproductive tissuesSex hormones—target reproductive tissues

• Anabolic hormones—stimulate anabolism in target cellsAnabolic hormones—stimulate anabolism in target cells

Classification by chemical structure Classification by chemical structure (Figure 16-3; Table 16-3)(Figure 16-3; Table 16-3)

• Steroid hormonesSteroid hormones

• Nonsteroid hormonesNonsteroid hormones


HormonesHormones

• Classification of hormones (cont.)Classification of hormones (cont.)

Steroid hormones (Figure 16-4)Steroid hormones (Figure 16-4)

• Synthesized from cholesterol (Figure 16-5)Synthesized from cholesterol (Figure 16-5)

• Lipid-soluble and can easily pass through the Lipid-soluble and can easily pass through the phospholipid plasma membrane of target cellsphospholipid plasma membrane of target cells

• Examples of steroid hormones: cortisol, aldosterone, Examples of steroid hormones: cortisol, aldosterone, estrogen, progesterone, and testosteroneestrogen, progesterone, and testosterone


HormonesHormones

• Classification of hormones (cont.)Classification of hormones (cont.) Nonsteroid hormones (Figure 16-6)Nonsteroid hormones (Figure 16-6)

• Synthesized primarily from amino acidsSynthesized primarily from amino acids

• Protein hormones—long, folded chains of amino acids; e.g., insulin and Protein hormones—long, folded chains of amino acids; e.g., insulin and parathyroid hormoneparathyroid hormone

• Glycoprotein hormones—protein hormones with carbohydrate groups Glycoprotein hormones—protein hormones with carbohydrate groups attached to the amino acid chainattached to the amino acid chain

• Peptide hormones—smaller than protein hormones; short chain of Peptide hormones—smaller than protein hormones; short chain of amino acids; e.g., oxytocin and antidiuretic hormone (ADH)amino acids; e.g., oxytocin and antidiuretic hormone (ADH)

• Amino acid derivative hormones—each is derived from a single amino Amino acid derivative hormones—each is derived from a single amino acid moleculeacid molecule

Amine hormones—synthesized by modifying a single molecule of tyrosine; Amine hormones—synthesized by modifying a single molecule of tyrosine; produced by neurosecretory cells and by neurons; e.g., epinephrine and produced by neurosecretory cells and by neurons; e.g., epinephrine and norepinephrinenorepinephrine

Amino acid derivatives produced by the thyroid gland; synthesized by Amino acid derivatives produced by the thyroid gland; synthesized by adding iodine to tyrosineadding iodine to tyrosine


HormonesHormones• How hormones workHow hormones work

General principles of hormone actionGeneral principles of hormone action• Hormones signal a cell by binding to the target cell’s specific receptors in a Hormones signal a cell by binding to the target cell’s specific receptors in a

“lock-and-key” mechanism (Figure 16-7)“lock-and-key” mechanism (Figure 16-7)

• Different hormone-receptor interactions produce different regulatory changes Different hormone-receptor interactions produce different regulatory changes within the target cell through chemical reactionswithin the target cell through chemical reactions

• Combined hormone actions:Combined hormone actions: Synergism—combinations of hormones acting together have a greater effect on a Synergism—combinations of hormones acting together have a greater effect on a

target cell than the sum of the effects that each would have if acting alonetarget cell than the sum of the effects that each would have if acting alone Permissiveness—when a small amount of one hormone permits, or enables,a second Permissiveness—when a small amount of one hormone permits, or enables,a second

one to have its full effects on a target cellone to have its full effects on a target cell Antagonism—one hormone produces the opposite effects of another hormone; used Antagonism—one hormone produces the opposite effects of another hormone; used

to “fine tune” the activity of target cells with great accuracyto “fine tune” the activity of target cells with great accuracy

• Most hormones have primary effects that directly regulate target cells and many Most hormones have primary effects that directly regulate target cells and many secondary effects that influence or modulate other regulatory mechanisms in secondary effects that influence or modulate other regulatory mechanisms in target cellstarget cells

• Endocrine glands produce more hormone molecules than are actually needed; Endocrine glands produce more hormone molecules than are actually needed; the unused hormones are quickly excreted by the kidneys or broken down by the unused hormones are quickly excreted by the kidneys or broken down by metabolic processesmetabolic processes


HormonesHormones• How hormones work (cont.)How hormones work (cont.)

Mechanism of steroid hormone action (Figure 16-8)Mechanism of steroid hormone action (Figure 16-8)

• Steroid hormones are lipid-soluble, and their receptors are normally Steroid hormones are lipid-soluble, and their receptors are normally found in the target cell’s cytosolfound in the target cell’s cytosol

• After a steroid hormone molecule has diffused into the target cell, it After a steroid hormone molecule has diffused into the target cell, it binds to a receptor molecule to form a hormone-receptor complexbinds to a receptor molecule to form a hormone-receptor complex

• Mobile-receptor model—hormone passes into nucleus, where it binds Mobile-receptor model—hormone passes into nucleus, where it binds to mobile receptor and activates a certain gene sequence to begin to mobile receptor and activates a certain gene sequence to begin transcription of mRNA; newly formed mRNA molecules move into the transcription of mRNA; newly formed mRNA molecules move into the cytosol, associate with ribosomes, and begin synthesizing protein cytosol, associate with ribosomes, and begin synthesizing protein molecules that produce the effects of the hormonemolecules that produce the effects of the hormone

• Steroid hormones regulate cells by regulating production of certain Steroid hormones regulate cells by regulating production of certain critical proteinscritical proteins

• The amount of steroid hormone present determines magnitude of a The amount of steroid hormone present determines magnitude of a target cell’s responsetarget cell’s response

• Because transcription and protein synthesis take time, responses to Because transcription and protein synthesis take time, responses to steroid hormones are often slowsteroid hormones are often slow


HormonesHormones• How hormones work (cont.)How hormones work (cont.)

Mechanisms of nonsteroid hormone actionMechanisms of nonsteroid hormone action

• The second messenger mechanism—also known as the fixed-membrane-The second messenger mechanism—also known as the fixed-membrane-receptor model (Figure 16-9)receptor model (Figure 16-9)

A nonsteroid hormone molecule acts as a “first messenger” and delivers its chemical A nonsteroid hormone molecule acts as a “first messenger” and delivers its chemical message to fixed receptors in the target cell’s plasma membranemessage to fixed receptors in the target cell’s plasma membrane

The “message” is then passed by way of a G protein into the cell, where a “second The “message” is then passed by way of a G protein into the cell, where a “second messenger” triggers the appropriate cellular changesmessenger” triggers the appropriate cellular changes

Second messenger mechanism—produces target cell effects that differ from steroid Second messenger mechanism—produces target cell effects that differ from steroid hormone effects in several important ways:hormone effects in several important ways:

– Effects of the hormone are amplified by the cascade of reactionsEffects of the hormone are amplified by the cascade of reactions

– There are a variety of second messenger mechanisms—examples: IP3, GMP, calcium-There are a variety of second messenger mechanisms—examples: IP3, GMP, calcium-calmodulin mechanisms (Figure 16-10)calmodulin mechanisms (Figure 16-10)

– The second messenger mechanism operates much more quickly than the steroid mechanismThe second messenger mechanism operates much more quickly than the steroid mechanism

• The nuclear receptor mechanism—small iodinated amino acids (TThe nuclear receptor mechanism—small iodinated amino acids (T44 and T and T33) enter ) enter the target cell and bind to receptors associated with a DNA molecule in the the target cell and bind to receptors associated with a DNA molecule in the nucleus; this binding triggers transcription of mRNA and synthesis of new nucleus; this binding triggers transcription of mRNA and synthesis of new enzymesenzymes


HormonesHormones

• Regulation of hormone secretionRegulation of hormone secretion Control of hormonal secretion is usually part of a negative Control of hormonal secretion is usually part of a negative

feedback loop and is called endocrine reflexes feedback loop and is called endocrine reflexes (Figure 16-11)(Figure 16-11)

Simplest mechanism—when an endocrine gland is sensitive Simplest mechanism—when an endocrine gland is sensitive to the physiological changes produced by its target cellsto the physiological changes produced by its target cells

Endocrine gland secretion may also be regulated by a Endocrine gland secretion may also be regulated by a hormone produced by another glandhormone produced by another gland

Endocrine gland secretions may be influenced by nervous Endocrine gland secretions may be influenced by nervous system input; this fact emphasizes the close functional system input; this fact emphasizes the close functional relationship between the two systemsrelationship between the two systems


HormonesHormones

• Regulation of target cell sensitivityRegulation of target cell sensitivity

Sensitivity of target cell depends in part on number of Sensitivity of target cell depends in part on number of receptors (Figure 16-12)receptors (Figure 16-12)

• Up-regulation—increased number of hormone receptors Up-regulation—increased number of hormone receptors increases sensitivityincreases sensitivity

• Down-regulation—decreased number of hormone receptors Down-regulation—decreased number of hormone receptors decreases sensitivitydecreases sensitivity

Sensitivity of target cell may also be regulated by factors that Sensitivity of target cell may also be regulated by factors that affect signal transcription or gene transcriptionaffect signal transcription or gene transcription


Prostaglandins (PGs)Prostaglandins (PGs)

• Unique group of lipid hormones (20-carbon fatty Unique group of lipid hormones (20-carbon fatty acid with 5-carbon ring) that serve important and acid with 5-carbon ring) that serve important and widespread integrative functions in the body but widespread integrative functions in the body but do not meet the usual definition of a hormone do not meet the usual definition of a hormone (Figure 16-13; Table 16-4)(Figure 16-13; Table 16-4)

• Called tissue hormones because the secretion Called tissue hormones because the secretion is produced in a tissue and diffuses only a short is produced in a tissue and diffuses only a short distance to other cells within the same tissue; distance to other cells within the same tissue; PGs tend to integrate activities of neighboring PGs tend to integrate activities of neighboring cellscells


ProstaglandinsProstaglandins

• Many structural classes of prostaglandins have been Many structural classes of prostaglandins have been isolated and identified:isolated and identified: Prostaglandin A (PGA)—intraarterial infusion resulting in an immediate fall Prostaglandin A (PGA)—intraarterial infusion resulting in an immediate fall

in blood pressure accompanied by an increase in regional blood flow to in blood pressure accompanied by an increase in regional blood flow to several areasseveral areas

Prostaglandin E (PGE)—vascular effects: regulation of red blood cell Prostaglandin E (PGE)—vascular effects: regulation of red blood cell deformability and platelet aggregation; inflammation (which can be blocked deformability and platelet aggregation; inflammation (which can be blocked with drugs that inhibit PG-producing enzymes such as COX-1 and COX-2), with drugs that inhibit PG-producing enzymes such as COX-1 and COX-2), gastrointestinal effects: regulates hydrochloric acid secretiongastrointestinal effects: regulates hydrochloric acid secretion

Prostaglandin F (PGF)—especially important in reproductive system, Prostaglandin F (PGF)—especially important in reproductive system, causing uterine contractions; also affects intestinal motility and is required causing uterine contractions; also affects intestinal motility and is required for normal peristalsisfor normal peristalsis

• Many tissues are known to secrete PGsMany tissues are known to secrete PGs

• PGs have diverse physiological effectsPGs have diverse physiological effects


Pituitary GlandPituitary Gland

• Structure of the pituitary glandStructure of the pituitary gland Formerly known as hypophysisFormerly known as hypophysis

Size: 1.2 to 1.5 cm (about 1⁄2 inch) across; weight: 0.5 g Size: 1.2 to 1.5 cm (about 1⁄2 inch) across; weight: 0.5 g (1⁄60 ounce)(1⁄60 ounce)

Located on the ventral surface of the brain within the Located on the ventral surface of the brain within the skull (Figure 16-14)skull (Figure 16-14)

Infundibulum—stemlike stalk that connects pituitary to Infundibulum—stemlike stalk that connects pituitary to the hypothalamusthe hypothalamus

Made up of two separate glands, the adenohypophysis Made up of two separate glands, the adenohypophysis (anterior pituitary gland) and the neurohypophysis (anterior pituitary gland) and the neurohypophysis (posterior pituitary gland)(posterior pituitary gland)



• Adenohypophysis (anterior pituitary)Adenohypophysis (anterior pituitary) Divided into two parts:Divided into two parts:

• Pars anterior—forms the major portion of adenohypophysisPars anterior—forms the major portion of adenohypophysis

• Pars intermediaPars intermedia

Tissue is composed of irregular clumps of secretory Tissue is composed of irregular clumps of secretory cells supported by fine connective tissue fibers and cells supported by fine connective tissue fibers and surrounded by a rich vascular networksurrounded by a rich vascular network

Three types of cells can be identified according to their Three types of cells can be identified according to their affinity for certain stains (Figure 16-15):affinity for certain stains (Figure 16-15):• Chromophobes—do not stainChromophobes—do not stain

• Acidophils—stain with acid stainsAcidophils—stain with acid stains

• Basophils—stain with basic stainsBasophils—stain with basic stains



• Adenohypophysis (anterior pituitary) (cont.)Adenohypophysis (anterior pituitary) (cont.)

Five functional types of secretory cells exist:Five functional types of secretory cells exist:

• Somatotrophs—secrete GHSomatotrophs—secrete GH

• Corticotrophs—secrete ACTHCorticotrophs—secrete ACTH

• Thyrotrophs—secrete TSHThyrotrophs—secrete TSH

• Lactotrophs—secrete prolactin (PRL)Lactotrophs—secrete prolactin (PRL)

• Gonadotrophs—secrete LH and FSHGonadotrophs—secrete LH and FSH




Growth hormone (GH) (Figure 16-16; Table 16-6)Growth hormone (GH) (Figure 16-16; Table 16-6)

• Also known as somatotropin (STH)Also known as somatotropin (STH)

• Promotes growth of bone, muscle, and other tissues by Promotes growth of bone, muscle, and other tissues by accelerating amino acid transport into the cellsaccelerating amino acid transport into the cells

• Stimulates fat metabolism by mobilizing lipids from storage in Stimulates fat metabolism by mobilizing lipids from storage in adipose cells and speeding up catabolism of the lipids after adipose cells and speeding up catabolism of the lipids after they have entered another cellthey have entered another cell

• GH tends to shift cell chemistry away from glucose catabolism GH tends to shift cell chemistry away from glucose catabolism and toward lipid catabolism as an energy source; this leads to and toward lipid catabolism as an energy source; this leads to increased blood glucose levelsincreased blood glucose levels

• GH functions as an insulin antagonist and is vital to maintaining GH functions as an insulin antagonist and is vital to maintaining homeostasis of blood glucose levelshomeostasis of blood glucose levels




Prolactin (PRL) (Table 16-6)Prolactin (PRL) (Table 16-6)

• Produced by acidophils in the pars anteriorProduced by acidophils in the pars anterior

• Also known as lactogenic hormoneAlso known as lactogenic hormone

• During pregnancy, PRL promotes development of the During pregnancy, PRL promotes development of the breasts, anticipating milk secretion; after the baby is breasts, anticipating milk secretion; after the baby is born, PRL stimulates the mother’s mammary glands to born, PRL stimulates the mother’s mammary glands to produce milkproduce milk



• Adenohypophysis (anterior pituitary) (cont.)Adenohypophysis (anterior pituitary) (cont.) Tropic hormones—have a stimulating effect on other endocrine glands; four Tropic hormones—have a stimulating effect on other endocrine glands; four

principal tropic hormones are produced and secreted by the basophils of the principal tropic hormones are produced and secreted by the basophils of the pars anterior (Table 16-6):pars anterior (Table 16-6):

• Thyroid-stimulating hormone (TSH), or thyrotropin—promotes and maintains Thyroid-stimulating hormone (TSH), or thyrotropin—promotes and maintains growth and development of thyroid; also causes thyroid to secrete its hormonesgrowth and development of thyroid; also causes thyroid to secrete its hormones

• Adrenocorticotropic hormone (ACTH), or adrenocorticotropin—promotes and Adrenocorticotropic hormone (ACTH), or adrenocorticotropin—promotes and maintains normal growth and development of cortex of adrenal gland; also maintains normal growth and development of cortex of adrenal gland; also stimulates adrenal cortex to secrete some of its hormonesstimulates adrenal cortex to secrete some of its hormones

• Follicle-stimulating hormone (FSH)—in female, stimulates primary graafian Follicle-stimulating hormone (FSH)—in female, stimulates primary graafian follicles to grow toward maturity; also stimulates follicle cells to secrete follicles to grow toward maturity; also stimulates follicle cells to secrete estrogens; in male, FSH stimulates development of seminiferous tubules of estrogens; in male, FSH stimulates development of seminiferous tubules of testes and maintains spermatogenesistestes and maintains spermatogenesis

• Luteinizing hormone (LH)—in female, stimulates formation and activity of corpus Luteinizing hormone (LH)—in female, stimulates formation and activity of corpus luteum of ovary; corpus luteum secretes progesterone and estrogens when luteum of ovary; corpus luteum secretes progesterone and estrogens when stimulated by LH; LH also supports FSH in stimulating maturation of follicles; in stimulated by LH; LH also supports FSH in stimulating maturation of follicles; in male, LH stimulates interstitial cells in testes to develop and secrete male, LH stimulates interstitial cells in testes to develop and secrete testosterone; FSH and LH are called gonadotropins because they stimulate testosterone; FSH and LH are called gonadotropins because they stimulate growth and maintenance of gonadsgrowth and maintenance of gonads



• Adenohypophysis (anterior pituitary) (cont.)Adenohypophysis (anterior pituitary) (cont.) Control of secretion in the adenohypophysisControl of secretion in the adenohypophysis

• Hypothalamus secretes releasing hormones into the blood, which are then Hypothalamus secretes releasing hormones into the blood, which are then carried to hypophyseal portal system (Figure 16-17; Table 16-5)carried to hypophyseal portal system (Figure 16-17; Table 16-5)

• Hypophyseal portal system carries blood from hypothalamus directly to Hypophyseal portal system carries blood from hypothalamus directly to adenohypophysis where target cells of releasing hormones are located adenohypophysis where target cells of releasing hormones are located (Figure 16-18)(Figure 16-18)

• Releasing hormones influence secretion of hormones by acidophils and Releasing hormones influence secretion of hormones by acidophils and basophilsbasophils

• Through negative feedback, hypothalamus adjusts secretions of Through negative feedback, hypothalamus adjusts secretions of adenohypophysis, which then adjusts secretions of target glands that, in turn, adenohypophysis, which then adjusts secretions of target glands that, in turn, adjust activity of their target tissues (Figure 16-19)adjust activity of their target tissues (Figure 16-19)

• Minute-by-minute variations in hormone secretion can exhibit occasional large Minute-by-minute variations in hormone secretion can exhibit occasional large peaks, caused by pulse in releasing hormone secretion by hypothalamus peaks, caused by pulse in releasing hormone secretion by hypothalamus (Figure 16-20)(Figure 16-20)

• In stress, hypothalamus translates nerve impulses into hormone secretions by In stress, hypothalamus translates nerve impulses into hormone secretions by endocrine glands, basically creating a mind-body linkendocrine glands, basically creating a mind-body link


Adrenal GlandsAdrenal Glands

• Adrenal cortex (cont.)Adrenal cortex (cont.)

MineralocorticoidsMineralocorticoids

• Have an important role in regulatory process of sodium in the bodyHave an important role in regulatory process of sodium in the body

• AldosteroneAldosterone

Only physiologically important mineralocorticoid in the human; primary Only physiologically important mineralocorticoid in the human; primary function is maintenance of sodium homeostasis in the blood by function is maintenance of sodium homeostasis in the blood by increasing sodium reabsorption in the kidneysincreasing sodium reabsorption in the kidneys

Aldosterone also increases water retention and promotes loss of Aldosterone also increases water retention and promotes loss of potassium and hydrogen ionspotassium and hydrogen ions

Aldosterone secretion is controlled by the renin-angiotensin-Aldosterone secretion is controlled by the renin-angiotensin-aldosterone system (RAAS) and by blood potassium concentration aldosterone system (RAAS) and by blood potassium concentration (Figure 16-32)(Figure 16-32)



• Adrenal cortex (cont.)Adrenal cortex (cont.)

GlucocorticoidsGlucocorticoids

• Main glucocorticoids secreted by the zona fasciculata are cortisol, Main glucocorticoids secreted by the zona fasciculata are cortisol, cortisone, and corticosterone, with cortisol the only one secreted in cortisone, and corticosterone, with cortisol the only one secreted in significant quantitiessignificant quantities

• Affect every cell in the bodyAffect every cell in the body

• Are protein-mobilizing, gluconeogenic, and hyperglycemicAre protein-mobilizing, gluconeogenic, and hyperglycemic

• Tend to cause a shift from carbohydrate catabolism to lipid Tend to cause a shift from carbohydrate catabolism to lipid catabolism as an energy sourcecatabolism as an energy source

• Essential for maintaining normal blood pressure by aiding Essential for maintaining normal blood pressure by aiding norepinephrine and epinephrine to have their full effect, causing norepinephrine and epinephrine to have their full effect, causing vasoconstrictionvasoconstriction


Adrenal GlandsAdrenal Glands Glucocorticoids (cont.)Glucocorticoids (cont.)

• High blood concentration causes eosinopenia and marked High blood concentration causes eosinopenia and marked atrophy of lymphatic tissuesatrophy of lymphatic tissues

• Act with epinephrine to bring about normal recovery from injury Act with epinephrine to bring about normal recovery from injury produced by inflammatory agentsproduced by inflammatory agents

• Secretion increases in response to stressSecretion increases in response to stress

• Except during stress response, secretion is mainly controlled by Except during stress response, secretion is mainly controlled by a negative feedback mechanism involving ACTH from the a negative feedback mechanism involving ACTH from the adenohypophysisadenohypophysis

• Secretion is characterized by several large pulses of increased Secretion is characterized by several large pulses of increased hormone levels throughout the day—the largest occurring just hormone levels throughout the day—the largest occurring just before waking (Figure 16-33)before waking (Figure 16-33)

Gonadocorticoids—sex hormones (androgens) that are Gonadocorticoids—sex hormones (androgens) that are released from the adrenal cortexreleased from the adrenal cortex



• Adrenal medullaAdrenal medulla Neurosecretory tissue—composed of neurons specialized to Neurosecretory tissue—composed of neurons specialized to

secrete their products into the bloodsecrete their products into the blood

Adrenal medulla secretes two important hormones—epinephrine Adrenal medulla secretes two important hormones—epinephrine and norepinephrine; they are part of the class of nonsteroid and norepinephrine; they are part of the class of nonsteroid hormones called catecholamineshormones called catecholamines

Both hormones bind to the receptors of sympathetic effectors to Both hormones bind to the receptors of sympathetic effectors to prolong and enhance the effects of sympathetic stimulation by the prolong and enhance the effects of sympathetic stimulation by the ANS (Figure 16-34)ANS (Figure 16-34)


Pancreatic IsletsPancreatic Islets

• Structure of the pancreatic islets (Figure 16-35)Structure of the pancreatic islets (Figure 16-35)

Elongated gland, weighing approximately 100 g Elongated gland, weighing approximately 100 g (3.5 ounces); its head lies in the duodenum, extends (3.5 ounces); its head lies in the duodenum, extends horizontally behind the stomach, and then touches horizontally behind the stomach, and then touches the spleenthe spleen

Composed of endocrine and exocrine tissuesComposed of endocrine and exocrine tissues

• Pancreatic islets (islets of Langerhans)—endocrine portionPancreatic islets (islets of Langerhans)—endocrine portion

• Acini—exocrine portion—secretes a serous fluid containing Acini—exocrine portion—secretes a serous fluid containing digestive enzymes into ducts draining into the small intestinedigestive enzymes into ducts draining into the small intestine



• Structure of the pancreatic islets (cont.)Structure of the pancreatic islets (cont.) Pancreatic islets—each islet contains four primary Pancreatic islets—each islet contains four primary

types of endocrine glands joined by gap junctionstypes of endocrine glands joined by gap junctions

• Alpha cells (A cells)—secrete glucagon (Figure 16-36)Alpha cells (A cells)—secrete glucagon (Figure 16-36)

• Beta cells (B cells)—secrete insulin; account for up to 75% of Beta cells (B cells)—secrete insulin; account for up to 75% of all pancreatic islet cellsall pancreatic islet cells

• Delta cells (D cells)—secrete somatostatinDelta cells (D cells)—secrete somatostatin

• Pancreatic polypeptide cells (F, or PP, cells)—secrete Pancreatic polypeptide cells (F, or PP, cells)—secrete pancreatic polypeptidespancreatic polypeptides



• Pancreatic hormones (Table 16-9)—work collaboratively Pancreatic hormones (Table 16-9)—work collaboratively to maintain homeostasis of food molecules (Figure 16-37)to maintain homeostasis of food molecules (Figure 16-37)

Glucagon—produced by alpha cells; tends to increase blood Glucagon—produced by alpha cells; tends to increase blood glucose levels; stimulates gluconeogenesis in liver cellsglucose levels; stimulates gluconeogenesis in liver cells

Insulin—produced by beta cells; lowers blood concentration of Insulin—produced by beta cells; lowers blood concentration of glucose, amino acids, and fatty acids and promotes their glucose, amino acids, and fatty acids and promotes their metabolism by tissue cellsmetabolism by tissue cells

Somatostatin—produced by delta cells; primary role is regulating Somatostatin—produced by delta cells; primary role is regulating the other endocrine cells of the pancreatic isletsthe other endocrine cells of the pancreatic islets

Pancreatic polypeptide—produced by F (PP) cells; influences the Pancreatic polypeptide—produced by F (PP) cells; influences the digestion and distribution of food molecules to some degreedigestion and distribution of food molecules to some degree


GonadsGonads

• Testes (Figure 16-2; Table 16-10)Testes (Figure 16-2; Table 16-10)

Paired organs within the scrotum in the malePaired organs within the scrotum in the male

Composed of seminiferous tubules and a Composed of seminiferous tubules and a scattering of interstitial cellsscattering of interstitial cells

Testosterone is produced by the interstitial cells Testosterone is produced by the interstitial cells and is responsible for the growth and maintenance and is responsible for the growth and maintenance of male sexual characteristicsof male sexual characteristics

Testosterone secretion is mainly regulated by Testosterone secretion is mainly regulated by gonadotropin levels in the bloodgonadotropin levels in the blood


GonadsGonads

• Ovaries (Figure 16-2; Table 16-10)Ovaries (Figure 16-2; Table 16-10) Primary sex organs in the femalePrimary sex organs in the female

Set of paired glands in the pelvis that produce several types Set of paired glands in the pelvis that produce several types of sex hormonesof sex hormones

• Estrogens—steroid hormones secreted by ovarian follicles; Estrogens—steroid hormones secreted by ovarian follicles; promote development and maintenance of female sexual promote development and maintenance of female sexual characteristicscharacteristics

• Progesterone—secreted by corpus luteum; maintains the lining Progesterone—secreted by corpus luteum; maintains the lining of the uterus necessary for successful pregnancyof the uterus necessary for successful pregnancy

• Ovarian hormone secretion depends on the changing levels of Ovarian hormone secretion depends on the changing levels of FSH and LH from adenohypophysisFSH and LH from adenohypophysis


PlacentaPlacenta

• Tissues that form on the lining of the uterus as Tissues that form on the lining of the uterus as a connection between the circulatory systems a connection between the circulatory systems of the mother and the developing childof the mother and the developing child

• Serves as a temporary endocrine gland that Serves as a temporary endocrine gland that produces human chorionic gonadotropin, produces human chorionic gonadotropin, estrogens, and progesterone (Table 16-10)estrogens, and progesterone (Table 16-10)


Thymus (Figure 16-2)Thymus (Figure 16-2)

• Gland located in the mediastinum just Gland located in the mediastinum just beneath the sternumbeneath the sternum

• Thymus is large in children, begins to atrophy Thymus is large in children, begins to atrophy at puberty, and, by old age, the gland is a at puberty, and, by old age, the gland is a vestige of fat and fibrous tissuevestige of fat and fibrous tissue

• Considered to be primarily a lymphatic organ, Considered to be primarily a lymphatic organ, but the hormone thymosin has been isolated but the hormone thymosin has been isolated from thymus tissue (Table 16-10)from thymus tissue (Table 16-10)

• Thymosin—stimulates development of T cellsThymosin—stimulates development of T cells


Gastric and Intestinal Mucosa Gastric and Intestinal Mucosa

• The mucous lining of the GI tract contains cells that produce The mucous lining of the GI tract contains cells that produce both endocrine and exocrine secretions both endocrine and exocrine secretions (Table 16-10)(Table 16-10)

• GI hormones such as gastrin, secretin, and cholecystokinin GI hormones such as gastrin, secretin, and cholecystokinin (CCK) play regulatory roles in coordinating the secretory and (CCK) play regulatory roles in coordinating the secretory and motor activities involved in the digestive processmotor activities involved in the digestive process

• Ghrelin—hormone secreted by endocrine cells in gastric Ghrelin—hormone secreted by endocrine cells in gastric mucosa; stimulates hypothalamus to boost appetite; mucosa; stimulates hypothalamus to boost appetite; slows metabolism and fat burning; may be a contributor slows metabolism and fat burning; may be a contributor to obesityto obesity


Heart Heart

• The heart has a secondary endocrine roleThe heart has a secondary endocrine role

• Hormone-producing cells produce several atrial Hormone-producing cells produce several atrial natriuretic peptides (ANPs), including atrial natriuretic peptides (ANPs), including atrial natriuretic hormone (ANH) (Table 16-10)natriuretic hormone (ANH) (Table 16-10)

• ANH’s primary effect is to oppose increases in ANH’s primary effect is to oppose increases in blood volume or blood pressure; also an blood volume or blood pressure; also an antagonist to ADH and aldosteroneantagonist to ADH and aldosterone


Other Endocrine Glands and Organs Other Endocrine Glands and Organs (Table 16-10)(Table 16-10)

• Major endocrine glands produce more hormones Major endocrine glands produce more hormones that are outlined in this book (e.g., inhibin that are outlined in this book (e.g., inhibin secreted by the ovaries)secreted by the ovaries)

• Many tissues (perhaps all tissues) produce Many tissues (perhaps all tissues) produce hormones, most of which are beyond the scope hormones, most of which are beyond the scope of this book (e.g., leptin and resistin secreted by of this book (e.g., leptin and resistin secreted by adipose tissue)adipose tissue)


Cycle of Life: Endocrine SystemCycle of Life: Endocrine System

• Endocrine regulation begins in the wombEndocrine regulation begins in the womb

• Many hormones are active from gestational periodMany hormones are active from gestational period Evidence that a hormonal signal from fetus to mother signals Evidence that a hormonal signal from fetus to mother signals

the onset of laborthe onset of labor

• Hormones related to reproduction begin at pubertyHormones related to reproduction begin at puberty

• Secretion of male reproductive hormones—continuous Secretion of male reproductive hormones—continuous production from puberty, slight decline in late production from puberty, slight decline in late adulthoodadulthood

• Secretion of female reproductive hormones declines Secretion of female reproductive hormones declines suddenly and completely in middle adulthoodsuddenly and completely in middle adulthood


The Big Picture: The Endocrine The Big Picture: The Endocrine System and the Whole BodySystem and the Whole Body

• Nearly every process in the human organism is kept in Nearly every process in the human organism is kept in balance by the intricate interaction of different nervous balance by the intricate interaction of different nervous and endocrine regulatory chemicalsand endocrine regulatory chemicals

• The endocrine system operates with the nervous system The endocrine system operates with the nervous system to finely adjust the many processes they regulateto finely adjust the many processes they regulate

• Neuroendocrine system adjusts nutrient supplyNeuroendocrine system adjusts nutrient supply

• Calcitonin, parathyroid hormone, and vitamin D balance Calcitonin, parathyroid hormone, and vitamin D balance calcium ion usecalcium ion use

• The nervous system and hormones regulate reproductionThe nervous system and hormones regulate reproduction

Mosby items and derived items © 2007, 2003 by Mosby, Inc.Slide 1 Chapter 16 Endocrine System.

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Transcript of Mosby items and derived items © 2007, 2003 by Mosby, Inc.Slide 1 Chapter 16 Endocrine System.