Endocrine

Endocrine

Function• Influences growth, metabolism, and homeostasis over prolonged

periods• Secretes hormone products into interstitial spaces which are then

absorbed into the blood and transported throughout the body• Hormonal control is much slower than nervous control, but the

effects of the endocrine system are much longer lasting

Key Features of Endocrine Glands• A rich capillary blood supply is necessary for secretion and

reception of hormones• Endocrine glands are, by definition, ductless• Organelles required to synthesize specific hormones are in great

supply

Hormone Classifications

Amino Acid Derivatives• Hormones derived from the amino acid tyrosine• Epinephrine, norepinephrine, and thyroxine

Polypeptide Hormones• Hormones with a peptide structure• Insulin, prolactin, NGF, EGF, GH, PTH, TSH, enkephalin,

TRH, ADH

Steroids• Hormones derived from cholesterol• Testosterone, cortisol, aldosterone, progesterone, estradiol

Pituitary Gland• Controlled by hypothalamus

• Infundibulum serves as a communication channel between the hypothalamus and pituitary

• The hypothalamohypophyseal neural tract is the passageway for two hypothalamic hormones to the posterior pituitary

• The hypothalamohypophyseal portal system carries hypothalamic hormones that regulate secretion from the anterior pituitary

• The anterior pituitary secretes hormones that regulate lactation, metabolism, growth, stress response, and reproduction

Pituitary Gland

A

B

A: Adenohypophysis (anterior pituitary): 1. Pars distalis. 2. Pars intermedia 3. Pars tuberalisB: Neurohypophysis (posterior pituitary): 1. Infundibulum 2. Pars nervosa

E

A

D C

B

Practice

Adenohypophysis

A: Chromophobes

B: Basophilic chromophils Gonadotrophs– FSH and LH

Corticotrophs– ACTHThyrotrophs– TSH

C: Acidophilic chromophils Somatotrophs– GH Mammotrophs– Prolactin

A

B

C

Practice

Neurohypophysis

A

A: Pituicytes

H: Herring Bodies

ReviewFill in the missing hormones secreted from the pituitary or list their respective functions

Hormone Function

FSH

Causes follicle maturation and testosterone production in leydig cells

ACTH

Stimulates T3 and T4 secretion from thyroid

GH

Stimulates mammary glands

ADH

Smooth muscle contraction and milk letdown

LH

TSH

Prolactin

Oxytocin

Follicle maturation and spermatogenesis

Stimulates adrenal cortex

Controls growth

Stimulates water resorption

Thyroid

A

B

4

A: Follicular cells

B: Parafollicular cells

Parathyroid

A: Adipose tissue.

C: Capillaries

P: Principal or chief cells

O: Oxyphil cells

A

B

Practice

A

B

Pancreas

A

A: Islets of Langerhans contain four different cells: 1. α-cells 2. β-cells 3. δ-cells. 4. PP– cells

Stomach

AB

Gastrin or G-cells

A: Parietal cell.

B: Chief cell.

Adrenal Gland

A B C D

A: Zona glomerulosa

B: Zona fasciculata

C: Zona reticularis

D: Medulla

Practice

Clinical Connections

Pheochromocytoma

Source: http://en.wikipedia.org/wiki/Pheochromocytoma

• Neuroendocrine tumor of the adrenal medulla• Results in excessive secretion of catecholamines• Diagnosed by measuring plasma or urine levels of

catecholamines

Enteroendocrine Cell

A

A: Argentaffin cells

B: Central Lacteal

B

Practice

Review

Anterior PituitaryFSHLHACTHTSHGHProlactin

Posterior PituitaryADHOxytocin

ThyroidT3 and T4Calcitonin

ParathyroidPTH

PancreasGlucagonInsulinSomatostatinPancreatic Peptide

StomachGastrin

AdrenalAldosteroneCortisolDHEA

Argentaffin CellCCKSecretinSerotonin

Know the following hormones, where they are secreted, their function, and target organ.