This document provides an overview of the endocrine system. It describes the key endocrine glands including the hypothalamus and pituitary gland, thyroid gland, parathyroid glands, thymus gland, adrenal glands, and pancreatic islets. For each gland, it discusses their location in the body, structure, the hormones they produce, and their functions in regulating other glands and metabolic processes through feedback loops in the body. The relationship between the hypothalamus and pituitary gland in controlling the endocrine system is also summarized.

1. Chapter 19 ENDOCRINE SYSTEM
1. Compare the basic organization and function of the ES and
the NS
2. Describe the structural and functional organization of the
hypothalamus and the pituitary and explain their relationship
3. Discuss the locations and structures of the thyroid,
parathyroid, and adrenal glands as well as the thymus and
the endocrine part of the pancreas.
4. List the hormones (and their function) produced by these
glands.
5. Briefly review the results of abnormal hormone production

2. Endocrine System Overview
 Ductless glands produce
hormones
 Gland may be entire organ or
interspersed bits of tissue
 Chemical classification of
hormones
 Target tissues are identified
by receptors

3. Hypothalamus
Control Center for
internal environment
Regulates nervous and endocrine systems via
3 mechanisms:
1. ANS centers exert nervous control on adrenal
medulla
2. ADH and Oxytocin production
3. Regulatory hormone production (RH and IH)
controls pituitary gland directly and all other
endocrine glands indirectly
Fig 19-3

4. Pituitary Gland (= Hypophysis)
Structure:
Infundibulum - connection to hypothalamus
In the sella turcica
Two parts with an embryonic double origin
Posterior Pituitary = neurohypophysis Storage shed for
ADH and Oxytocin (produced in ?)
Anterior Pituitary = adenohypophysis production of 7
peptide hormones, see fig 19.5
Histology
Fig 19-4

5. Hypophyseal Portal System
 Portal systems:
two capillary networks
in serial arrangement
Advantage?
 Named after their
destination: . . .
 Portal veins: blood
vessels that link two
capillary networks
Fig 19-6

6. Thyroid Gland
 Anterior surface of trachea
just inferior of thyroid
cartilage (or Adam’s apple)
 Two lobes connected by
isthmus
 Microscopic thyroid follicles
produce thyroid hormone
 C Cells - produce calcitonin
(Ca2+)
Fig 19-7

7. Thyroid Gland Function
 Thyroxin (T4) and
triiodothyronine (T3)
 speed up metabolic
rate
 Calcitonin  lowers
blood Ca2+ levels
 Thyroid pathologies:
Hyper- and
Hypothyroidism
Goiter
Exophthalmus

8. Hyperthyroidism
Hypothyroidism
Slowing of mind
and body

9. Four Parathyroid Glands
Parathyroid hormone
(PTH; sometimes
also called
parathormone)
Function: antagonist
to Calcitonin Fig 19-9
4 tiny glands embedded in the back of the thyroid
(superior and inferior)

10. Thymus Gland
 Inside thoracic cavity
immediately
posterior to sternum
above the heart
 Most active in
infancy and
childhood - Largest
just before puberty
 Thymosin - enhances
lymphocyte
production and
competence.
(important for immune
system)

11. Adrenal or Suprarenal Gland
 Cortex: corticosteroid production
aldosterone, cortisol, sexhormone
 Medulla: modified sympathetic ganglion
produces adrenaline and noradrenaline
(parallels sympathetic division of ANS)
 Histology
Fig 19-10

12. Pancreas
 Part of endocrine and
digestive systems.
(99% exocrine)
 Pancreatic islets or islets of Langerhans
  cells: glucagon ( blood sugar levels by
stimulating liver to convert glycogen to glucose)
  cells: insulin ( blood sugar levels by causing the
cells to take up glucose for use by the mitochondria)
  cells: somatostatin