Chapter 25 Endocrine System

Introduction

Ductless glandsSecrete hormonesControl other organs / cells (target tissue)

ComponentsPituitary glandThyroid glandParathyroid glandAdrenal glandPancreas Others Gonads Hypothalamus Enteroendocrine

glands Thymus

25.1

PituitaryLocated in sella turcicaInfundibulum Stalk connects to

hypothalamus

Adenohypophysis Anterior pituitary Gland tissue

Neurohypophysis Posterior pituitary Neural pituitary

25.3abc

Development of Pituitary

From 6-8 weeks the neurohypophyseal bud grows inferiorly from the hypothalamusthe hypophyseal pouch grows superiorly from the roof of the mouth (Rathke’s pouch)neurohypophyseal bud becomes the posterior lobe (neurohypophysis)hypophyseal pouch becomes the anterior pituitary (adenohypophysis)

5-6 wks

25.14a-d

Adenohypophysis (ant. pit.)

7 hormonesGH growth hormone Stimulates body growth, e.g., epiphyseal plate

PRL prolactin Stimulates mammary glands to produce milk

TSH thyroid stimulating hormone TH, metabolic rate

ACTH adrenocorticotropic hormone Stimulate adrenal cortex to secrete steroids

Adenohypophysis

MSH melanocyte stimulating hormoneFSH follicle stimulating hormone Stimulates development of sperm and

ova

LH luteinizing hormone Stimulates development of sperm and

ova

HypothalamusControls adenohypophysisReleasing hormones Inhibiting hormones

25.3

Hypophyseal portal system

Hormones secreted in hypothalamusEnter capillariesCarried by hypophyseal portal veins Second capillary bed in adenohypophysisHormones affect adenohypophyseal cells

25.5

Neurohypophysis

Nerve cell bodies in hypothalamusAxons to neurohypophysis via infundibulum

25.6

ADH (antidiuretic hormone), vasopressin

Targets DCT and collecting tubules

H2O reabsorption blood volume BP concentration of urine,

volume

23.4b

Oxytocin

Stimulates smooth muscle of uterus during childbirth

24.26cd

Thyroid gland

Located around trachea Just inferior to larynx

25.7

Thyroid follicle

Functional unitSphere of cellsSecrete TH precursorTH stimulates basal metabolic rateInfluenced by TSH

25.7bc

Hyperthyroidism & exophthalmos

Protrusion of one or both eyeballs that results from orbital inflammation, edema, tumors, or injuries; cavernous sinus thrombosis; or enlargement of the eyeball (as in congenital glaucoma and unilateral high myopia). In hyperthyroidism, edema and lymphoid infiltration of the orbital tissues may cause unilateral or bilateral exophthalmos. http://www.merck.com/mrkshared/mmanual/section8/chapter92/92c.jsp

Grave’s disease / hyperthyroidism

Graves' disease patient with exophthalmos and vitiligo. Vitiligo is a skin condition resulting from loss of pigment which produces white patches. It may be an autoimmune process http://www.aad.org/pamphlets/Vitiligo.html

http://www.thyroidmanager.org/Chapter11/11-text.htm

Parafollicular cells

Located between folliclesSecrete calcitonin blood Ca++ levels Inhibits osteoclasts Ca++ secretion in kidney Mainly in childhood

25.7bc

Parathyroid glandsLocation: 2 pairs of tiny glands on posterior surface of thyroid glandPTH blood Ca++

Stimulates osteoclasts excretion of Ca++ by

kidney Activates vitamin D

25.9a

Adrenal glandLocated on superior surface of kidneyAdrenal medulla Secretes norepinephrine &

epinephrine Targets sympathetic

effector organs

Adrenal cortex Secretes corticosteroids sER

25.10

Adrenal cortexAldosterone reabsorption of H2O and Na+ in

kidney

Cortisol Helps body deal with stress blood glucose levels Anti-inflammatory, suppresses

immune response

Pancreas

Exocrine pancreas Digestive enzymes

Endocrine pancreas Islets of Langerhans cells

Secrete glucagon blood sugar levels

cells Secrete insulin blood sugar levels

25.12