Endocrine System How the body communicates with itself Nervous system – impulses travel down nerves Endocrine system – hormones released into the blood and travel to target organs.

Endocrine System Glands can be one of three types Exocrine – release secretions that are carried within a duct or tube – sweat glands, salivary glands, sebaceous glands Endocrine – release secretions directly into the blood – thyroid gland, adrenal gland, anterior pituitary gland Heterocrine – contain both exocrine and endocrine components – pancreas, testis

Endocrine System Endocrine system may consists of organs containing very specific concentrations of secretory cells (thyroid gland, pituitary gland, adrenal gland) Organs that have dispersed areas of special secretory cells (pancreas), testis, ovary) Dispersed cells within various organs (stomach, intestine, kidney)

Two kinds of secreting cells Nitrogen-secreting cell Steroid –secreting cell

Primary Endocrine Glands Addressed in this Unit Hypophysis (Pituitary Gland) Thyroid Gland Parathyroid Gland Adrenal Gland Pancreas *Testis and ovary will be covered in Reproductive System

Thyroid and Parathyroid Glands Found at 2nd through 4th cartilages of the trachea Small gland with four parathyroid glands attached to the posterior surface. Follicles are the structural unit of the gland. Follicle consists of a wall of simple cuboidal epithelium cells inclosing a space containing a jelly-like substance called colloid. If the colloid distends the follicles, the epithelial cells can become flattened almost like simple squamous. Colloid combines with iodine to form thyroid hormones – regulate body metabolism. Isthmus thyroglobulin

Thyroid Gland Abnormalities Hyperthyroid condition often result of tumor. Can produce disease called Graves syndrome Hypothyroid condition – cretinism in children and myxedema in adults Goggle-eyed myxedema Democratic Republic of the Congo Girl 15 with Cretinism Democratic Republic of the Congo Girl 15 with Cretinism

Thyroid and Parathyroid Glands Between the follicles are located small groups of parafollicular cells which secrete hormone thyrocalcitonin or often called just calcitonin. Calcitonin functions to reduce calcium levels in the blood by actively reducing breakdown of bone and inhibiting re-absorption of calcium in digestive system.

Adrenal Gland Ectoderm;endoderm Adrenal gland is located above each kidney Divided on bases of outer region (cortex) and inner region (medulla) The cortex is divided into three regions (glomerulosa, fasciculatus, and reticularis) Ectoderm;endoderm

Adrenal Gland Adrenal Cortex consists of three regions: Outer region known as the zona glomerulosa. Theses cells are arranged in rounded clumps and secrete hormones known as mineralcorticoids. The most common mineralcorticoid is aldosterone which helps to control electrolyte and water balance. The next region is known as the zona fasciculata. It consists of columns of cells. It secretes hormone known as glucocorticoids including cortisone and hydrocortisone. These hormones help to regulate glucose metabolism and important in inflammation reactions and stress management.

The inner region of the cortex is the zona reticularis The inner region of the cortex is the zona reticularis. Cells of this region form and network of interlinking cells. Secrete sex hormones mainly androgens or male sex hormones. Usually in small proportions if too many can cause bearded lady. Adrenal Medulla Consist of irregularly arranged groups of granular cells and connective tissue Produces two products epinephrine and norepinephrine. Part of the bodies response to an emergency or the fight or flight response.

Pituitary or Hypophysis Small gland about size of large pea located under brain. Often referred to as the “master gland”. Secretes hormones that regulate other endocrine glands Consists of two major lobes, anterior and posterior separated by intermediate lobe. The larger anterior lobe referred to as the adenohypophysis. This is a highly glandular tissue that produces and secretes numerous hormones. The second smaller posterior lobe is referred to as the neurohypophysis. This is neural tissue that secretes two hormones produced by hypothalmus. posterior lobe D = pars distalis, I= pars intermedia N = pars nervosa, S = stem or stalk T = pars tuberalis Anterior lobe

Adenohypophysis Neurohypophysis Pituitary gland or Hypophysis Pars distalis or anterior lobe Pars nervosa or posterior lobe Intermedia between black lines

Adenohypothesis Larger anterior lobe Subdivided into the glandular pars distalis which is most of the lobe and is active in secretion Also contains the pars tuberalis that forms covering for stalk The pars intermedia separates the anterior lobe from the posterior lobe

lactation period Adenohypophysis Cell types in the adenohypophysis are identified as to their staining characteristics Chromophilic cells include the acidophils which stain with eosin stain and are thus reddish and the basophils which stain with hematoxylin and are thus dark blue/purple colored in hematoxylin/eosin staining. Chromophobes do not stain with either stain There are different types of Acidophils that can be separated with very special stains. These can not be separated with H & E stains. They include: Somatrophs – secrete Growth Hormone Mammotrophs – secrete prolactin There are different types of Basophils that can be separated with very special stains. These can not be separated with H & E stains. They include: Thyrotrophs – secrete Thyroid Stimulating Hormone Gonadotrophs – secrete Luteinizing (LH) hormone and Follicle Stimulating Hormone (FSH). ACTH-secrete adenocorticotrophic hormone regulates adrenal cortex Chromophobes lactation period

Young female dwarf standing next to a boy of normal stature. Growth Hormone function Young female dwarf standing next to a boy of normal stature. gigantism

Posterior lobe or Neurohypophysis Consists mostly of nervous tissue, pituitary cell, herring body Does not produce any hormones but does secrete two hormones produced by the hypothalamus Secretes oxytocin – regulates uterine muscle contraction and mammory glands stimulating milk flow Secretes ADH – Antidiuretic hormone which increases water retention by the kidney