This document provides an overview of the major endocrine glands and their functions. It describes how the hypothalamus and pituitary gland regulate hormone production and release from other glands like the thyroid, parathyroid, adrenals, gonads and more. Key hormones are identified for each gland along with their roles in processes like metabolism, growth, reproduction and maintaining homeostasis. Histology slides are also included to illustrate the cellular structure of the different endocrine tissues.

1. Lab Exercise 19
THE ENDOCRINE SYSTEM

2. Introduction to Endocrine
 Endocrine glands
 Produce chemical messengers called hormones
 Picked up by blood capillaries and travel throughout the body
 Ductless secretions
 Exocrine glands- secrete material in ducts or tubules (sweat & salivary glands) or on
surface (ovaries). Do not use the cardiovascular sxs.
 Target Areas
 Areas that are receptive to hormones, organs or tissues
 Stomach, heart, & kidneys produce hormones, thus have endocrine functions
 Hormone Functions
 Growth, change in development, metabolism, sexual development, regulation of
the sexual cycle, & homeostasis

4. Hypothalamus
 Has a major role in controlling endocrine functions
 Secretes both releasing & inhibitory hormones that stimulate hormone
secretions from their target areas or prevent the release of hormones from
theses areas.
 Gonadotropic-releasing hormones (GnRH)
 Stimulate the pituitary to release:
 Follicle-stimulating hormone
 Thyrotropic-releasing hormone (TRH)
 Stimulates the pituitary to release thyroid-stimulating hormones (TSH)

5. Pineal Gland
 Developed from the diencephalon of the brain
 Resembles a pine nut
 Melatonin
 Hormone secreted by the pineal gland
 Inhibitory hormone
 Regulates circadian rhythms (Daily body rhythms)
 Depressing effect in some people
 “Hormone of darkness” produced during times of low light & inhibited in bright
light

6. Pituitary Gland
 Divided into 2 divisions
 Anterior pituitary
 Originate from the roof of the oral cavity
 Histology: Cuboidal epithelial cells
 Produce several hormones
 Posterior pituitary
 Originates from the base of the brain
 Composed of nervous tissue
 Hormones are secreted by the hypothalamus

8. Histology: Anterior Pituitary Gland
Slide 45
Posterior
Anterio
Zip Files: Lab 18: Anterior Pituitary gland

9. Posterior Pituitary Gland
 Antidiuretic hormone (ADH)
 Stimulates reabsorption & retention of water by the kidneys
 Also known as a Vasopressin
 Arterioles constrict which causes the elevation of BP
 Oxytocin
 Stimulates contraction of the cells of the mammary glands to release milk and
causes uterine contractions
 Send impulses to the hypothalamus  stimulates the posterior pituitary gland to
release oxytocin which will cause milk to release

10. Thyroid
 2 lateral lobes with a medial isthmus connecting them. Found near the thyroid
cartilage of the larynx.
 Secrete 3 hormones:
 Two: T3
 One: T4
 Basal metabolic rates
 The number of calories required to keep your body functioning at rest
 Stored in the colloid
 Calcitonin
 Another hormone
 Deposition of calcium in bone  decrease osteoclast activity
 Produced in the parafollicular or C cells

11. Histology: Thyroid
 Follicle cells that surrounds the Colloid
 Storage region for thyroid hormones
 Composed of thyroglobulin where the thyroid hormones are formed
 Parafollicular cells
 Found in the spaces between the follicles

12. Parathyroid Glands
 Posterior portion of the thyroid & are 2 pairs of organs
 Chief Cells
 Secrete parathyroid hormones (PTH)
 Opposite of the calcitonin
 Increase calcium levels in the blood
 Increasing calcium uptake in the intestines, increasing kidney reabsorption of calcium,
and releasing calcium from the bones

13. Histology: Parathyroid Glands

14. Thymus
 Active in young people and plays an important part in immunocompetency
 It become smaller as we age and develops more fibrous and fatty tissue
 Thymosin
 Hormone thymus secretes
 Causes the maturation of the T cells
 Originates from bone marrow  thymus  lymph nodes & spleen to carry out
functions
 Maturation is to provide ”cell immunity” against antigens

15. Histology: Thymus

16. Pancreas
 Mixed gland
 Exocrine function
 Digestive in nature
 Pancreatic juice secreted through the pancreatic ducts contains both buffers & digestive
enzymes
 Endocrine function
 Consist of the secretion of the 2 hormones
1. Insulin
 Regulates BG levels
2. Glucagon
 Regulates BG levels
 Delta Cells
 Which secrete somatostatin
 Which inhibits digestive secretions

17. Glucagon & Insulin
 Glucagon
 Produced in specialized cells Alpha cells
 In clusters called Islets of Langerhans
 Also produce insulin  lowers BG levels
 Insulin
 Produced in beta cells
 Stimulates the conversion of glucose to glycogen

18. Histology: Pancreas

19. Adrenal Glands
 Ad= Next to; Renal= Kidney. Located superior to the kidneys
 Composed of:
 Cortex
 Outer
 Medulla
 Inner
 Corticosteroid hormones
 Secreted from the adrenal cortex
 Controlled by ACTH
 Important in water & ion balance in the body; carbohydrate, protein, fat metabolism,
as well as stress management
 Epinephrine & Norepinephrine
 Stimulate the adrenal glands by the sympathetic nervous division causes release of
these hormones from the gland

20. Adrenal Cortex
 3 regions
 Zona Glomerulosa
 Outermost
 Consist of clusters of cells that secrete Mineralocorticoids
 Zona Fasciculata
 Inside zona glomerulosa closer to the medulla
 Parallel bundles of cell that secrete Glucocorticoids
 Zona Reticularis
 Deepest layer
 Branched patterns of cells that produce both Glucocorticoids & Sex Hormones

21. Histology: Adrenal Gland

22. Gonads
 Produce sex hormones  Endocrine glands
 Receptive to follicle-stimulating hormones (FSH) from the Anterior Pituitary
 Produce & Maturation of the sex cells
 Oocytes
 Testes
 Produce Testosterone
 Facial hair & body hair production, expansion of the larynx, and increased muscle &
bone mass

23. Histology: Testes
 Seminiferous tubules & interstitial cells

24. Ovaries
 Produce Estrogen & progesterone
 Enlarged breast, development of additional subcutaneous adipose layer, &
higher voice
 Influence the development of endometrium, causes maturation of the Oocytes
and regulate MC
 Endocrine:
 Produce hormones
 Pregnancy the placenta has a major role in the secretion of estrogen &
progesterone
 Exocrine
 Oocytes (eggs) production

25. Histology: Ovary

26. Know for the Exam
 Histology slides