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

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

Thyroid Gland Abnormalities

• Hyperthyroid condition often result of tumor. Can produce disease called Graves syndrome

• Hypothyroid condition – cretinism in children and myxedema in adults

Democratic Republic of the Congo Girl 15 with Cretinism

Goggle-eyed myxedemaDemocratic 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

• 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 inflamation reactions and stress management.

• 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

Anterior lobeD = pars distalis, I= pars intermediaN = pars nervosa, S = stem or stalkT = pars tuberalis

Pars distalis or anterior lobe

Pars nervosaor posterior lobe

Intermedia between black lines

Pituitary gland or Hypophysis

AdenohypophysisNeurohypophysis

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

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

Young female dwarf standing next to a boy of normal stature.

gigantism

Growth Hormone function

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