99

OBJECTIVE

● To identify and understand the important role of the endocrine system in regulating the activity of body cells. To understand and be able to explain the functions of the various hormones and the results of their hyposecretion or hypersecretion within the body.

INTRODUCTION: ENDOCRINE SYSTEM FACTS● The endocrine system works with the nervous system in controlling much of what goes on in the

body. Review the following basic facts regarding the endocrine system:

1. It is composed of glands.

2. Glands produce hormones.

3. Hormones are chemical messengers that are released directly into the blood (no ducts).

4. Hormones work at specific locations (targets).

5. Hormones work by attaching to receptors at the target.

6. Receptors may be on the target cell membrane or inside the target cell (intracellular).

7. The pituitary is often called the master gland of the body since it oversees much of the action of other glands.

8. The pituitary gland is controlled by the hypothalamus.

9. The pituitary gland is functionally and structurally related to the hypothalamus.

10. Structural relationships include direct axonal connections between the hypothalamus and the posterior pituitary and a specialized “portal” system (a capillary network).

11. Functional relationships include the release of releasing and inhibiting hormones by the ventral hypothalamus which affects the anterior pituitary (or adenohypophysis) and the production of oxytocin and ADH by the hypothalamic nuclei which are stored and released as needed by the posterior pituitary (or neurohypophysis).

LAB 11The Endocrine System

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100 | Lab 11 The Endocrine System

PART A: GROSS ANATOMY OF THE ENDOCRINE SYSTEM● Use the models in your lab, your lab manual, and your textbooks, and name and locate all of the

endocrine glands in the body. Fill in the table below.

GLAND HORMONES PRODUCEDAnterior pituitary

Posterior pituitary

Thyroid

Parathyroid

Adrenal

Pancreas

Testes

Ovaries

Pineal

Thymus

PART B: HISTOLOGY OF SELECTED ENDOCRINE GLANDS● Obtain slides of the glands listed above and observe the histological features listed. Be able to

identify each tissue and the cells that perform specific endocrine function(s) within that tissue.

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ThyroidParathyroid

Pituitary

Pancreas

AdrenalGlands

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Lab 11 The Endocrine System | 101

1. Thyroid gland

a. Find follicles. What is produced by the follicles? How is this substance produced?

b. Find parafollicular cells. What is produced here?

c. What chemical element is critical in the production of the major thyroid hormones?

d. What is the target of the hormone produced by the parafollicular cells?

2. Parathyroid gland

a. What is the physical relationship between this gland and the thyroid?

b. Normally, how many parathyroid glands are there?

c. How can one distinguish the parathyroid gland from the thyroid?

d. What hormone is produced by the parathyroid gland? What is its target?

3. Adrenal gland

a. Differentiate between the cortex and the medulla.

b. How many zones are present in the cortex? Identify them.

c. What hormones are produced in each of the cortical zones? (Fill in the following table.)

CORTICAL ZONE HORMONE CLASS SPECIFIC HORMONE/S

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102 | Lab 11 The Endocrine System

d. What is the importance of the adrenal medulla?

e. What histological feature allows the medulla to do its work quickly and efficiently?

f. Why is the medulla often referred to as a “postganglionic sympathetic neuron”?

4. Islets of Langerhans (Pancreas)

a. How many cell types make up the Islets of Langerhans?

b. What hormones are produced by each of the cell types?

CELL TYPE HORMONE

c. What is the major function of the Islets of Langerhans?

5. Pituitary gland

a. How can one distinguish between the anterior and posterior pituitary? Why?

b. What hormones are produced by the posterior pituitary?

c. What are the chemical “signals” that cause the anterior pituitary to release its hormones?

d. Where do these “signals” come from?

e. How do these “signals” get to the anterior pituitary?

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Lab 11 The Endocrine System | 103

PART C: ENDOCRINE TABLES (1 AND 2)● Complete the following table of endocrine glands.

EN

DO

CR

INE

GL

AN

DS

: RE

GU

LA

TIO

N A

ND

EF

FE

CT

S

GL

AN

DH

OR

MO

NE

ST

IMU

LA

TE

DIN

IBIT

ED

TA

RG

ET

EF

FE

CT

S O

F H

OR

MO

NE

POST

ER

IOR

PI

TUIT

ARY

Ant

idiu

rtet

ic (A

DH

) [s

upra

op

tic n

ucle

us o

f hy

po

thal

amus

]

Oxy

toci

n [p

arav

entic

ular

nuc

leus

o

f hyp

oth

alam

us]

AN

TER

IOR

PI

TUIT

ARY

Gro

wth

Ho

rmo

ne (G

H)

pro

lact

in (P

RL)

Thyr

oid

Stim

ulat

ing

H

orm

one

(TSH

)

And

reno

cott

ico

tro

pic

H

orm

one

(AC

TH)

Folli

cle

Stim

ulat

ing

H

orm

one

(FSH

)

Lutc

iniz

ing

Ho

rmo

ne

(LH

)

THYR

OID

G

LAN

DTh

yro

xin

(pro

duc

ed b

y fo

llicu

lar

cells

)

Cal

cito

nin

(pro

duc

ed

by

par

afo

llicu

lar

cells

)

PAR

ATH

YRO

ID

GLA

ND

Para

thyr

oid

Ho

rmo

ne

(PTH

) (se

cret

ed b

y ch

ief c

ells

)

TA

BL

E 1

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104 | Lab 11 The Endocrine System

EN

DO

CR

INE

GL

AN

DS

: RE

GU

LA

TIO

N A

ND

EF

FE

CT

S

GL

AN

DH

OR

MO

NE

ST

IMU

LA

TE

DIN

IBIT

ED

TA

RG

ET

EF

FE

CT

S O

F H

OR

MO

NE

AD

RE

NA

L G

LAN

D (C

ort

ex)

Glo

coco

rtic

oid

s (C

ort

iso

l)

Min

eral

oco

rtic

oid

s (A

ldo

ster

one

)

Go

nad

oco

rtic

oid

s (s

ex h

arm

one

s)

AD

RE

NA

L G

LAN

D (M

edul

la)

Ep

inep

hrin

e &

N

ore

pin

ephr

ine

PAN

CR

EA

S

Insu

lin (

cel

ls in

isle

ts

of L

ang

erha

ns)

Glic

ago

n (a

lpha

ce

lls in

isle

ts o

f La

nger

hans

)

TEST

STe

sto

tero

ne

OV

ER

IES

Est

rog

en

Pro

ges

tero

ne

PIN

EA

L G

LAN

DM

elat

oni

n

THYM

US

GLA

ND

Thym

ic H

arm

one

s (T

hym

op

oie

tins

&

Thym

osi

ns)

TA

BL

E 2

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Lab 11 The Endocrine System | 105

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STRUCTURAL AND FUNCTIONAL RELATIONSHIPSOF THE PITUITARY AND HYPOTHALAMUS

HYPOTHALAMUS

Supraopticnucleus

Optic chiasma

Paraventricularnucleus

Infundibulum

Hypophyseal portalsystem

Primary CapillaryPlexus

Hypothalamic-hypophysealtract

Neurohypophysis

Hypophysealportal veins

Secondary capillaryplexus

Adenohypophysis

Kidneys

ADH

Oxytocin

Uterus

Bones

Breast

OvaryTestes

Adrenal cortex

Thyroid gland

TSH

GH

ProlactinACTH

LHFSH

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106 | Lab 11 The Endocrine System

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Nuclei of Hypothalamus Neurohormone production

Oxytocinand ADH

Infindibulum(Pituitary Stalk)

(Adenohypophysis)AnteriorPituitary

(Neurohypophysis) Posterior Pituitary

PITUITARYGLAND

HYPOTHALAMUS

Hypothalamic-Hypophyseal:

–Tract–Portal system

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Lab 11 The Endocrine System | 107

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Posterior pituitary hormones

Releasing hormone(hypothalamus)

Pituitaryhormone Target Effects

ADHStoresADH

Kidneys, sweatglands,

circulatory systemWater balance

OTFemale

reproductivesystem

Triggers uterinecontractions

during childbirth

Anterior Pituitary Hormones

Releasing hormone(hypothalamus)

Pituitaryhormone Target Effects

LHGnRHReproductive

system

Reproductivesystem

Stimulates productionof sex hormonesby gonads

GnRH FSHStimulates productionof sperm and eggs

TRH TSH Thyroid gland

Stimulates the releaseof thyroid hormone(TH). TH regulatesmetabolism

PRH(inhibitedby GHIH)

GHRH(inhibitedby GHIH)

PRLMammary

glandsPromotes milkproduction

GH Liver, bone,muscles

Includes targets toproduce insulin-likegrowth factors (IGF).IGFs stimulate bodygrowth and a highermetabolic rate.

CRH ACTH Adrenalglands

Induces targets toproduceglucocorticoids whichregulate metabolismand the stressresponse

ENDOCRINE TABLE

-

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108 | Lab 11 The Endocrine System

HYPOTHALAMIC-PITUITARY AXIS

Ventral hypothalamus RH IH

Hypothalamus

Paraventricularnucleus (oxytocin)

Supraopticnucleus (ADH)

Infundibulum(pituitary stalk)

Hypothalamic-hypophyseal tract

Primary plexus

Hypothalamic-hypophyseal

portal system

Secondary plexus

Anterior pituitary(adenohypophysis)

Posterior pituitary(neurohypophysis)

Neurohormonereleasing axon tracts

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Lab 11 The Endocrine System | 109

Hypothalamus

Direct control bynervoussystem

Direct releaseofhormones

Indirect control through releaseof regulatory hormones

Key to Pituitary hormones

ACTHTSHGHPRLFSHLHMSHADH

Adrenocorticotropic hormoneThyroid-stimulating hormoneGrowth hormoneProlactinFollicle-stimulating hormoneLuteinizing hormoneMelanocyte-stimulating hormoneAntidiuretic hormone

Adrenalmedulla

Adrenalcortex

Adrenalgland

ACTH ADH

TSHGH

PRL FSH LH MSH

Somatomedins

Glucocorticoids

Thyroidhormones

Inhibin InhibinTestosterone Estrogen

Progesterone

Anteriorpituitary gland Posterior

pituitary gland

Kidneys

Males: Smoothmuscle in ductusdeferens andprostate gland

Females: Uterinesmooth muscleand mammaryglands

Melanocytes(uncertain significancein healthy adults)

Ovaries of femaleTestes of malesMammary

glands

Bone,muscle,other tissues

Thyroid gland

Epinephrine andnorepinephrine

Oxytocin

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110 | Lab 11 The Endocrine System

1 Capillary blood contains low concentrationof Ca2+, which stimulates...

2 ..secretion of parathyroid hormone (PTH) 2 ..to secrete catecholamines

2 ..stimulate theanterior pituitarygland to secretehormonesthat...

3 ..stimulate other endocrine glandsto secrete hormones

1 Preganglionic SNS fiber stimulates adrenalmedulla cells...

1 The hypothalamus secretes hormones that...

Three types of stimuli for hormone release

Capillary(low Ca2+

in blood)

Parathyroidglands

Thyroidgland(posteriorview)

Parathyroidglands

a Humoral b Neural c Hormonal

CNS (spinal cord)

PreganglionicSNS fiber

PTH

Medulla ofadrenal gland

Capillary Thyroid gland Adrenal cortex Gonad(Testis)

Hypothalamus

Pitulary gland

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Lab 11 The Endocrine System | 111

Cou

rtes

y of

Mic

hael

Cry

der

TRH GRH GnRH

Endocrine Hormone Chart (produced in Hypothalamus butstored in Posterior Pituitary)

R = Releasing HormonesTropicNon-Tropic

InhibitedBy:

Anterior Pituitary

TSH

ThyroidGland

Adrenal

Cortex

Aldosterone:↑blood

volume &pressure,↓blood K+

levels

Thyroxin:GHIH

SH: NotSeen

Insulin: decrease in bloodglucose or (GHIH)

Glucagon: Increase inblood sugar glucose levels

PTH: Calcitonin &feedback inihibition

Melatonin:Light

Thymic Hormones:Unknown

Calcitonin:PTH &

feedbackinhibition

Cortisol:feedbackinhibition

exerted bycortisol

Medulla Ovaries Teates

Gonads

ACTH LH LH GHPRL+

BreastTissues

PancreasAlpha

PancreasBeta

Parathyroid

PTH

Bones Brain

Melatonin

Pineal Thymus

ThymopoietinThymosins

T-lymphocytes

Insulin

Bloodstream

Glucagon

Liver &Muscles

Liver, Bone,Muscle, Cartilage,

Adipose, etc.

PRH GHRH OT+ ADH

Posterior Pituitary

OT+ ADH

Uterus+Breasts

OT+: Lack ofappropriate

neural stimuli

ADH: Adequatehydration of the

body & by alcohol

FSH: Feedbackinhibition

exerted byinhibin/Estrogen

&Testosterone

PRL: (PIH)Dopamine

ACTH: Feedbackinhibition exertedby glucocorticoids

LH: Feedbackinhibition exertedEstrogen/Progest-

erone &Testosterone

GH: By Feedbackinhibition exertedby GH & IGF’s, by

hyperglycemia,hyperlipidemia,

obesity, & emotionaldeprivation from↑GHIH or ↓GHIH

TSH: Feedbackinhibition exerted byinhibin/Estrogen &

Testosterone

Kidneys

T3,T4F

AllCells

Epinephrine& NE:

Autonomics

Estrogen &Progesterone:

FeedbackInhibition

Testosterone:FeedbackInhibition

Bones CellskidneysFemaleRepro

SexOrgans

Females Males

CalcitoninP.F.

Aldosterone,cortisol,SexHormones

Epinephrine,NE

Estrogen,Progeste-

rone

Testost-erone

ENDOCRINE FLOWCHART

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