Human Anatomy - M.M. Kurepina, A.P. Ozhigova, A.A. Nikitina 2010

Internal Organs
Endocrine System (Glands of Internal Secretion)
Pancreas (Islet Apparatus)

The Endocrine portion of the Pancreas is represented by islets of secretory Cells (islets of Langerhans) located between the exocrine acini (Atlas, Fig. 186). The islets are most numerous in the tail of the gland. Their shape varies from round or oval to stellate, and their size ranges from 100 to 300 µm. A well-developed network of fenestrated capillaries lies between the cells within the islets. The islets are formed by several Cell types. The most numerous ones are Insulin-producing beta cells, while others are Glucagon-producing alpha cells. Later, delta cells were discovered, which produce gastrin and Somatostatin. There are also other cells whose Functions are associated with The production of active Peptides.

Renewal of the Cells of the islet apparatus occurs through their slow division. When there is an excess of CARBOHYDRATES in the diet of humans and animals, insulin-producing cells experience increased stress. As a result of such hyperfunction, their degeneration and death begin. Consequently, a disease known as Diabetes Mellitus develops. Insulin and glucagon are involved in all METABOLISM/4.html">Types of Metabolism.

Differentiation of cells synthesizing insulin and glucagon occurs within 3 months of intrauterine development; by the 12th week, their secretory activity becomes apparent, and by the end of the 5th month, the islets of Langerhans acquire the Structure characteristic of adults. Insulin, together with Growth Hormone, regulates growth processes: its concentration increases during periods of intense growth and after birth.

In addition to the aforementioned Endocrine glands, an endocrine function is performed by the cells described in sections 4.5.1 and 4.5.2, located in the Testes and Ovaries. These are interstitial cells located between the convoluted seminiferous tubules that secrete testosterone, and Sertoli cells in the walls of the seminiferous tubules. In the ovaries, oocytes are surrounded by follicular cells that produce estrogens. Because of the presence of such cells in the testes and ovaries, these Organs are referred to as Gonads.

Review Questions

1. What are the structural and developmental features of endocrine glands?

2. The Pituitary Gland: topography, structural features, and Development of the anterior and posterior lobes.

3. The Pineal Gland: topography, structural features.

4. The Thyroid Gland: topography, structural features, development.

5. The Parathyroid glands: topography, structural features, development.

6. The Adrenal Glands: topography, structural features, and development of the cortical and medullary substances.

7. Structural Features of the islet apparatus of the pancreas.