C H A P T E R 17 hormones Part 1streaming.missioncollege.org/dlamkin/media/BIOSC... · The Adrenal...

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PowerPoint® Lecture Slides prepared by Leslie Hendon University of Alabama, Birmingham

C H A P T E R

Copyright © 2011 Pearson Education, Inc.

Part 1

17 The Endocrine System


The Endocrine System: An Overview

•  A system of ductless glands •  Secrete messenger molecules called

hormones •  Interacts closely with the nervous system •  Endocrinology •  Study of hormones and endocrine glands


Endocrine Organs

•  Scattered throughout the body •  Pure endocrine organs are the …

•  Pituitary, pineal, thyroid, parathyroid, and adrenal glands

•  Organs containing endocrine cells include: •  Pancreas, thymus, gonads, and the hypothalamus •  Plus other organs secrete hormones (eg., kidney,

stomach, intestine) •  Hypothalamus is a neuroendocrine organ

•  Produces hormones and has nervous functions •  Endocrine cells are of epithelial origin


Location of the Major Endocrine Glands

Figure 17.1

Pineal gland Hypothalamus Pituitary gland

Parathyroid glands (on dorsal aspect of thyroid gland) Thymus

Thyroid gland

Adrenal glands

Pancreas

Ovary (female)

Testis (male)


Hormones •  Classes of hormones •  Amino acid–based hormones •  Steroids—derived from cholesterol

•  Basic hormone action •  Circulate throughout the body in blood vessels •  Influences only specific tissues— those with

target cells that have receptor molecules for that hormone • A hormone can have different effects on

different target cells (depends on the receptor)


Control of Hormones Secretion

•  Secretion triggered by three major types of stimuli: •  Humoral—simplest of endocrine control

mechanisms • Secretion in direct response to changing

ion or nutrient levels in the blood • Example: Parathyroid monitors calcium • Responds to decline by secreting

hormone to reverse decline

2


Control of Hormones Secretion

•  Secretion triggered by three major types of stimuli (continued) •  Neural

•  Sympathetic nerve fibers stimulate cells in the adrenal medulla

•  Induces release of epinephrine and norepinephrine •  Hormonal

•  Stimuli received from other glands •  Certain hormones signal secretion of other

hormones •  Example: Hypothalamus secretes hormones

stimulates pituitary stimulates other glands


Types of Endocrine Gland Stimuli

Figure 17.2

(a) Humoral stimulus (b) Neural stimulus (c) Hormonal stimulus

Capillary (low Ca2+ in blood)

Parathyroid glands

Thyroid gland (posterior view)

PTH

Parathyroid glands

CNS (spinal cord)

Medulla of adrenal gland

Preganglionic sympathetic fibers

Capillary

Hypothalamus

Thyroid gland

Adrenal cortex Gonad

(Testis)

Pituitary gland

Capillary blood contains low concentration of Ca2+, which stimulates…

Preganglionic sympathetic fibers stimulate adrenal medulla cells… The hypothalamus secretes

hormones that…

…stimulate the anterior pituitary gland to secrete hormones that…

…secretion of parathyroid hormone (PTH) by parathyroid glands. PTH acts to increase blood Ca2+.

…to secrete catecholamines (epinephrine and norepinephrine) …stimulate other endocrine glands

to secrete hormones

1 1 1

2

3 2 2


Control of Hormone Secretion

•  Always controlled by feedback loops •  Blood concentration declines below a

minimum --> More hormone is secreted •  Blood concentration exceeds maximum

--> Hormone production is halted


The Pituitary Gland

•  Secretes nine major hormones •  Attached to the hypothalamus by the infundibulum •  Two basic divisions of the pituitary gland

•  Adenohypophysis (anterior lobe) •  Has three major divisions

•  Pars distalis, pars intermedia, and pars tuberalis

•  Neurohypophysis (posterior lobe) —has two major divisions •  Pars nervosa and infundibular


The Pituitary Gland

Figure 17.3

Tuber cinereum

Mammillary body

Infundibulum Pars nervosa

Pars tuberalis Pars intermedia Pars distalis

Median eminence of hypothalamus

Optic chiasma

(c)

Anterior lobe Posterior lobe

(a)

(d)

Acidophil Basophil Chromophobe cell

Capillary with red blood cells

Spherical cluster of cells

(b)

Corpus callosum

Pituitary (hypophysis)

Brain stem

Mammillary body

Hypothalamus

Pineal

Thalamus


The Anterior Lobe

•  The pars distalis—largest division of the anterior lobe •  Contains five different endocrine cell groups •  Makes and secretes seven different hormones •  Tropic hormones regulate hormone

secretion by other glands •  Include: TSH, ACTH, FSH, LH

•  GH, PRL, and MSH • Act directly on non-endocrine target tissues

3


The Anterior Lobe

•  Growth hormone, GH (somatotropic hormone) •  Produced by somatotropic cells •  Stimulates body growth by stimulating

increased protein production and growth of epiphyseal plates

•  Stimulates growth directly and indirectly by the liver’s secretion of insulin-like growth factor-1.


The Anterior Lobe

•  Thyroid-stimulating hormone, TSH •  Produced by thyrotropic cells •  Signals thyroid gland to secrete thyroid

hormone •  Adrenocorticotropic hormone, ACTH •  Stimulates the adrenal cortex to secrete

hormones that help cope with stress


The Anterior Lobe

•  Melanocyte-stimulating hormone, MSH •  In humans, MSH functions in appetite

supression •  Gonadotropins— are produced by

gonadotropic cells and affect the gonads •  Follicle-stimulating hormone, FSH, and

luteinizing hormone, LH


The Anterior Lobe

•  Prolactin—produced by prolactin cells •  Targets milk-producing glands in the breast—

stimulates milk production •  Endocrine cells of the pars distalis •  Clustered in spheres and branching cords


The Anterior Lobe

Table 17.1 Copyright © 2011 Pearson Education, Inc.

The Anterior Lobe

Table 17.1

4


•  The hypothalamus •  Controls secretion of anterior lobe hormones •  Exerts control by secreting: • Releasing hormones—prompt anterior

lobe to release hormones •  Inhibiting hormones—turn off secretion of

anterior lobe hormones

Hypothalamic Control of Hormone Secretion from the Anterior Lobe


•  Releasing hormones •  Are secreted like neurotransmitters •  Enter a primary capillary plexus •  Travel in hypophyseal portal veins to a

secondary capillary plexus (hypothalamohypophyseal portal system) • From the secondary capillary plexus,

hormones secreted by the anterior lobe enter general circulation and travel to target organs

Hypothalamic Control of Hormone Secretion from the Anterior Lobe

Copyright © 2011 Pearson Education, Inc. Figure 17.4a

The Anterior Lobe

When appropriately stimulated, hypothalamic neurons secrete releasing and inhibiting hormones into the primary capillary plexus.

Hypothalamic hormones travel through the portal veins to the anterior pituitary where they stimulate or inhibit release of hormones from the anterior lobe.

Anterior pituitary hormones are secreted into the secondary capillary plexus.

Hypothalamus Hypothalamic neuron cell bodies

Hypophyseal portal system

Superior hypophyseal artery

(a) Relationship between the anterior pituitary and the hypothalamus

Anterior lobe of pituitary

TSH, FSH, LH, ACTH, GH, PRL

Primary capillary plexus Hypophyseal portal veins Secondary capillary plexus

1

2

3


The Posterior Lobe

•  Is structurally part of the brain •  Its axons make up the hypothalamic–

hypophyseal tract •  Arises from neuronal cell bodies in the

hypothalamus • Supraoptic nucleus • Paraventricular nucleus


The Posterior Lobe

•  Does not make hormones •  Stores and releases hormones made in the

hypothalamus •  Releases two peptide hormones •  Antidiuretic hormone (ADH) [aka, vasopressin] •  Oxytocin (OT)


Relationship Between the Posterior Pituitary and Hypothalamus

Figure 17.4b

Hypothalamic neurons synthesize oxytocin and ADH.

Oxytocin and ADH are transported along the hypothalamic- hypophyseal tract to the posterior lobe.

Oxytocin and ADH are stored in axon terminals in the posterior pituitary.

Oxytocin and ADH are released into the blood when hypothalamic neurons fire.

Paraventricular nucleus

Supraoptic nucleus

Optic chiasma

Hypothalamus

Inferior hypophyseal artery

Oxytocin ADH

Infundibulum (connecting stalk) Hypothalamic- hypophyseal tract

Axon terminals Posterior lobe of pituitary

(b) Relationship between the posterior pituitary and the hypothalamus

1

2

3

4

5


The Posterior Lobe

•  ADH (vasopressin) •  Made in supraoptic nucleus •  Targets kidneys to reabsorb water

•  Oxytocin •  Produced in the paraventricular nucleus •  Induces smooth muscle contraction of

reproductive organs, ejects milk during breast feeding, and signals contraction of the uterus during childbirth

Copyright © 2011 Pearson Education, Inc. Table 17.1


The Thyroid Gland

•  Located in the anterior neck •  Largest pure endocrine gland •  Composed of follicles and areolar connective

tissue •  Produces two hormones •  Thyroid hormone (TH) •  Calcitonin


The Thyroid Gland

Figure 17.5a

Hyoid bone Thyroid cartilage

Common carotid artery

Epiglottis

Superior thyroid artery

External carotid artery

Isthmus of thyroid gland

Left subclavian artery Left lateral lobe of thyroid gland

Inferior thyroid artery

Trachea

Right subclavian artery

Aorta

(a) Gross anatomy of the thyroid gland, anterior view


The Thyroid Gland

Figure 17.5b

Colloid-filled follicles

Follicular cells (secrete thyroid hormone)

Parafollicular cell (secretes calcitonin)

(b) Photomicrograph of thyroid gland follicles (160×) Copyright © 2011 Pearson Education, Inc.

The Parathyroid Glands

•  Lie on the posterior surface of the thyroid gland

•  Contain two types of endocrine cells •  Chief cells • Produce parathyroid hormone (PTH) •  Increases blood concentration of Ca2+

•  Oxyphil cells • Function unknown

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The Parathyroid Glands

Figure 17.6a, b

(b) Photomicrograph of parathyroid gland tissue (360×)

Capillary

Parathyroid cells (secrete parathyroid hormone) Oxyphil cells

Pharynx (posterior aspect)

Thyroid gland Parathyroid

glands

Trachea Esophagus

(a) Location of parathyroid glands, posterior view


The Adrenal (Suprarenal) Glands

•  Pyramid-shaped glands located on the superior surface of each kidney

•  Supplied by about 60 suprarenal arteries •  Nerve supply is almost exclusively

sympathetic fibers


The Adrenal (Suprarenal) Glands

•  Two endocrine glands in one •  Adrenal medulla—a cluster of neurons • Derived from neural crest • Part of the sympathetic nervous system

•  Adrenal cortex—forms the bulk of the gland • Derived from somatic mesoderm

•  All adrenal hormones help one cope with danger, terror, or stress


The Adrenal Medulla

•  Chromaffin cells •  Are modified ganglionic sympathetic neurons •  Secrete amine hormones epinephrine and

norepinephrine • Enhance “fight-or-flight” response • Hormones are stored in secretory vesicles

•  Are arranged in spherical clusters and some branching cords


The Adrenal Cortex

•  Secretes lipid-based steroid hormones •  Cortex is composed of three layers (zones) •  Zona glomerulosa—cells arranged in

spherical clusters •  Zona fasciculata—cells arranged in parallel

cords; contains lipid droplets •  Zona reticularis—cells arranged in a

branching network


The Adrenal Cortex

•  Hormones are corticosteroids •  Adrenal corticosteroids are of two main

classes •  Mineralocorticoids •  Glucocorticoids

•  Also secretes androgens

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Mineralocorticoids

•  Aldosterone—secreted by the zona glomerulosa •  Secreted in response to decline in blood

volume or blood pressure •  Is the terminal hormone of the renin-

angiotensin mechanism


Glucocorticoids

•  Cortisol is the main type •  Secreted by zona fasciculata and zona

reticularis •  Helps the body deal with stressful situations


The Adrenal Gland–Gross and Microscopic

Figure 17.7a, b

Cortex

Kidney

Medulla Adrenal gland

Capsule Aldosterone

Epinephrine and norepinephrine

Cortisol and androgens

Zona glomerulosa

Zona fasciculata

Zona reticularis

Adrenal medulla

(a)Drawing of the histology of the adrenal cortex and a portion of the adrenal medulla

(b) Photomicrograph (140X)

Hormones secreted

Co

rtex

Me

du

lla


Stress and the Adrenal Gland

Figure 17.8

Short-term stress More prolonged stress Stress

Hypothalamus

CRH (corticotropin- releasing hormone)

Corticotroph cells of anterior pituitary

To target in blood Adrenal cortex (secretes steroid hormones)

Glucocorticoids Mineralocorticoids

ACTH

Catecholamines (epinephrine and norepinephrine)

Short-term stress response 1.Increased heart rate 2.Increased blood pressure 3.Liver converts glycogen to glucose and releases glucose to blood 4.Dilation of bronchioles 5.Changes in blood flow patterns leading to decreased digestive system activity and reduced urine output 6.Increased metabolic rate

Long-term stress response 1.Retention of sodium and water by kidneys 2.Increased blood volume and blood pressure

1.Proteins and fats converted to glucose or broken down for energy 2.Increased blood glucose 3.Suppression of immune system

Adrenal medulla (secretes amino acid– based hormones)

Preganglionic sympathetic fibers

Spinal cord

Nerve impulses


The Pineal Gland

•  Located on the roof of the diencephalon •  Shaped like a pine cone •  “Pineal sand” is radiopaque •  Used as a landmark to identify other brain

structures in X rays •  Pinealocytes secrete melatonin •  A hormone that regulates circadian rhythms


The Pancreas

•  Located in the posterior abdominal wall •  Contains endocrine and exocrine cells •  Exocrine cells • Acinar cells —secrete digestive enzymes

•  Endocrine cells • Pancreatic islet cells —islets of Langerhans • About one million islets—scattered

throughout the pancreas

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The Pancreas

•  Main endocrine cell types •  Alpha cells (α cells)—secrete glucagon • Signals liver to release glucose from glycogen • Raises blood sugar

•  Beta cells (β cells)—secrete insulin • Signals most body cells to take up glucose

from the blood • Promotes storage of glucose as glycogen in

liver • Lowers blood sugar


The Pancreas

•  Pancreatic islets contain two rare cell types •  Delta (∂) cells • Secrete somatostatin •  Inhibits secretion of insulin and glucagon

•  F (PP) cells • Secrete pancreatic polypeptide • May inhibit exocrine activity of the

pancreas


The Thymus

•  Located in the lower neck and anterior thorax •  Important immune organ •  Site at which T-lymphocytes arise from

precursor cells


The Gonads

•  Main sources of sex hormones •  Testes and ovaries

•  Male •  Interstitial cells secrete androgens • Primarily testosterone • Promotes the formation of sperm • Maintains secondary sex characteristics

Male Hormones PLAY


The Gonads

•  Female •  Ovaries

•  Androgens secreted by the theca folliculi •  Converted to estrogen by follicular granulosa

cells • Estrogen • Maintains secondary sex characteristics

• Progesterone • Prepares the uterus for pregnancy


Other Endocrine Structures

•  Endocrine cells occur within •  The heart • Atria contain atrial natriuretic peptide

(ANP) •  The GI tract • Enteroendocrine cells

•  The placenta • Sustains the fetus and secretes several

steroid protein hormones

9


Other Endocrine Structures

•  The kidneys • Cells of the juxtaglomerular apparatus

(JGA) secrete renin • Endothelial cells and interstitial connective

tissue—secrete erythropoietin •  The skin • Modified cholesterol molecules convert to a

precursor of vitamin D


Pituitary Disorders

•  Gigantism •  Hypersecretion of GH in children

•  Pituitary dwarfism •  Hyposecretion of GH

•  Diabetes insipidus •  Pars nervosa does not make enough ADH


Disorders of the Pancreas: Diabetes Mellitus

•  Caused by •  Insufficient secretion of insulin •  Resistance of body cells to the effects of

insulin •  Type 1 diabetes •  Develops suddenly, usually before age 15 •  T cell–mediated autoimmune response

destroys beta cells


Diabetes Mellitus

•  Type 2 diabetes •  Adult onset •  Usually occurs after age 40 •  Cells have lowered sensitivity to insulin •  Controlled by dietary changes and regular

exercise


Disorders of the Thyroid Gland

•  Grave’s disease •  Most common type of hyperthyroidism •  Immune system makes abnormal antibodies • Stimulates the oversecretion of TH by

follicle cells •  Leads to nervousness, weight loss, sweating,

and rapid heart rate



•  Myxedema •  Adult hypothyroidism •  Antibodies attack and destroy thyroid tissue •  Low metabolic rate and weight gain are

common symptoms

10



•  Endemic goiter •  Due to lack of iodine in the diet

•  Cretinism •  Hypothyroidism in children •  Short, disproportionate body, thick tongue,

and mental retardation


Thyroid Disorders

Figure 17.10


Disorders of the Adrenal Cortex

•  Cushing’s syndrome •  Caused by hypersecretion of glucocorticoid

hormones—usually a pituitary tumor •  Addison’s disease •  Hyposecretory disorder of the adrenal cortex •  Deficiencies of both mineralocorticoids and

glucocorticoids


Thyroid Disorders

Figure 17.11


The Endocrine System Throughout Life

•  Thyroid gland •  Forms from a thickening of endoderm on the

floor of the pharynx •  Parathyroids and the thymus gland •  From endoderm lining the pharyngeal

pouches


Embryological Origin of Selected Endocrine Organs

•  Pineal gland •  Originates from ependymal cells

•  Pituitary gland—dual origin •  Adenohypophysis originates from the roof

of the mouth •  Neurohypophysis grows inferiorly from the

floor of the brain

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•  Adrenal gland—dual origin gland •  Adrenal medulla—from neural crest cells of

nearby sympathetic trunk ganglia •  Adrenal cortex—from mesoderm lining the

coelom



(b) Week 6. Inferior extension of the floor of the diencephalon forms the neurohypophyseal bud.

Neurohypophyseal bud

Hypophyseal pouch

Anterior Posterior

Hypothalamus

Brain


Pharyngeal pouches

Future parathyroid glands

Esophagus

(a) Week 5. Thyroid, thymus, and parathyroid glands form from pharyngeal endoderm. Hypophyseal pouch extends superiorly from ectoderm in the roof of the mouth.

Hypophyseal pouch

Future thyroid gland

Future thymus

Lung bud

Future mouth

Figure 17.12a, b



Figure 17.12c, d

(c) Week 7. Hypophyseal pouch pinches off the surface ectoderm and is closely associated with the neurohypophyseal bud.


Hypophyseal pouch

(d) Week 8. Hypophyseal pouch forms the anterior lobe of pituitary; neurohypophyseal bud forms the posterior lobe. Distinct portions of each differentiate.

Anterior lobe

Pars tuberalis

Pars distalis

Pars intermedia

Third ventricle of brain

Posterior lobe

Infundibulum

Pars nervosa



•  Endocrine organs operate effectively until old age •  Anterior pituitary

•  Increase in connective tissue and lipofuscin •  Decrease in vascularization and number of hormone-

secreting cells •  Adrenal cortex

•  Normal rates of glucocorticoid secretion continue •  Adrenal medulla

•  No age-related changes in catecholamines



•  Thyroid hormones •  Decrease slightly with age

•  Parathyroid glands •  Little change with aging

•  GH, DHEA, and the sex hormones •  Marked drops in secretion with age

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