Animal Histology- Endocrine System: - Rutgers University



Animal Histology- Endocrine System:

Overview:

Hormone: A substance, usually a peptide or steroid, produced by one tissue and conveyed by the bloodstream to another to effect physiological activity, such as growth or metabolism. A chemical produced in one part of the body and released into the blood to trigger or regulate particular functions of the body.

Endocrine glands: Glands that produce and secrete hormones into the blood or lymph systems, including the thyroid, parathyroid, hypothalamus, pineal, pituitary, adrenal, islets of Langerhans in the pancreas, and the gonads (testes and ovaries). The effects of these hormones may affect one organ or tissue, or the entire body.

Exocrine Glands: Glands which secrete substances through ducts to surrounding surfaces. Includes sweat, salivary and tear glands, as well as the mucous glands in the digestive, respiratory, and genitourinary systems. These glands are greatly affected in CF. Their ducts may be obstructed by mucus.

I. Pituitary Gland:

Location: base of brain

Composed of 4 parts:

1. Pars Nervosa (Posterior Pituitary)

2. Pars Tuberalis

3. Pars Intermedia

4. Pars Distalis (Anterior Pituitary)

1. Pars Nervosa (Posterior Pituitary or Neurohypophysis)

∙ contains axonal projections of HH tract (hypothalamohypophyseal tract)

Secretes:

|Hormone |Target |Main Effects |

|Oxytocin |Uterus/Mammary Glands |Uterine contractions; lactation |

|Antiduretic Hormone (ADH) or Vasopressin |Kidneys or Arterioles |Stimulates water retention; raises blood |

| | |pressure by contracting arterioles |

3 Features to Know:

∙ axons have product accumulating around end bulb = palisades zone

∙ herring bodies = accumulation of secretory products in axon terminal bulbs

∙ supporting cell type = pituicyte

Red = Pituicyte ; Blue = Herring Body

2. Pars Tuberalis (refer to above overall picture of pituitary gland)

∙ entrance of the hypophysioportal blood system into the anterior pituitary

(wraps the pituitary stalk in a highly vascularized sheath)

∙ projects off the pars distalis

∙ composed of cuboidal cells, and blood vessels

3. Pars Intermedia

∙ boundary between the anterior and posterior lobes of the pituitary

∙ composed of pale staining cells, arranged in follicles, or as a few rows of

basophilic cells and associated capillaries

Secretes:

|Hormone |Main Effects |

|Melanocyte Stimulating Hormone (MSH) |Controls degree of pigmentation of melanocytes |

Blue = Pars Nervosa (Posterior Pituitary); Yellow = Pars Intermedia;

Red = Pars Distalis (Anterior Pituitary)

4. Pars Distalis (Anterior Pituitary or Adenohypophysis)

∙ irregular cords of cells, between capillaries.

a. chromophils = actively secreting (stain)

(2 types) basophils and acidophils

b. chromophobes = not actively secreting (do not stain)

Secrets:

|Hormone |Secretory Cell Type |Target |Main Effects |

|ACTH/Adrenocorticotropic hormone |Corticotrophs (Basophils) |Adrenal Gland |Secretion of Glucocorticoids |

|(Corticotropin) | | | |

|Endorphins | ______ |Opioid receptors |Inhibit pain perception |

|FSH/ Follicle Stimulating Hormone |Gonadotrophs (Basophils) |Ovaries/ Testes |Reproduction System Growth |

|Human Growth Hormone (Somatrotropin) |Somatotrophs (Acidophils) |Liver, Adipose Tissues |Promotes Growth: lipid and carbohydrate |

| | | |metabolism |

|LH/ Lutenizing Hormone |Gonadotrophs (Basophils) |Ovaries/ Testes |Sex Hormone Production |

|PRL/Prolactin |Lactotrophs or Mammotrophs (Acidophils)|Ovaries/Mammary Glands |Secretion of Estrogens/Progesterone; Milk|

| | | |Production |

|TSH/ Thyroid Stimulating Hormone |Thyotrophs (Basophils) |Thyroid Gland |Secretion of Thyroid Hormone |

Blue = Acidophils (Chromophils) ; Yellow = Chromophobes ; Red = Basophils Chromophils)

II. Thyroid:

Location: butterfly shaped organ, on anterior side of neck around larynx and

trachea.

Composed of:

1. Follicles:

-surround central mass of stored precursor = the colloid or

thyroglobulin

2. Follicular cells:

-arranged as a simple cuboidal epithelium with a basement membrane

- granules in cells = intracellular colloid

- produce thyroxine

3. Parafollicular or C cells (on outside of the follicle):

- produce calcitonin

Secretes:

|Hormone |Cell Source |Main Effects |

|Thyroid Hormone |Follicular Cells |Stimulates metabolic activity |

|Calcitonin |Parafollicular Cells |Decreases Blood Calcium Levels |

Red = Parafollicular Cells; Blue = Follicular Cells

Red arrows= Follicular Cells; Blue arrows = Colloid (thyroglobulin);

Yellow arrow = Parafollicular (C cells)

III. Parathyroid: (may see fat in gland)

Location: 4 small glands (2 pairs) sitting in the neck behind the thyroid gland

∙ cells are arranged in irregular cords, supported by reticular fibers, surrounded by capillaries

∙ 2 types of cells in the parathyroid:

1. Chief Cells: major cell type; small cells with spherical nuclei, and pale staining, granular cytoplasm. (less cytoplasm around nuclei)

2. Oxyphil Cells: found in clumps, at periphery of gland; much larger than chief cells. (lots of cytoplasm around nuclei)

Secretes:

|Hormone |Main Effects |

|Parathyroid Hormone |Increases blood calcium levels |

Blue= Oxyphil Cells; Red = Chief Cells

IV. Adrenal Gland: each surrounded by a CT capsule

Location: triangular shaped organs sitting on top of each kidney.

2 Main Parts:

1. Cortex:

3 Layers:

a. Zona glomerulosa: beneath the connective tissue capsule, consists of irregular clusters of columnar cells

b. Zona fasciculata: the thickest layer, located under the zona glomerulosa; consists of straight cords of cells perpendicular to the surface, called spongiocytes = very high cholesterol content and appear light staining

c. Zona reticularis: inner most layer, consists of thin cords of cells with increased acidophilic staining

2. Medulla: central core gland, surrounded by cortex, chromaffin cells(ovoid basophilic cells) arranged in clumps/irregular cords around an extensive capillary system.

Secrets:

|Hormone |Source |Main Effects |

|Glucocorticoids (type of steroid hormone) |Adrenal Cortex |Increases blood glucose levels and |

| | |decreases protein synthesis |

|Mineralocorticoids (type of steroid |Adrenal Cortex |Increases water reabsoprtion in the kidney |

|hormone) | | |

|Epinephrine (Adrenaline) & Norepinephrine |Adrenal Medulla |Increases blood glucose levels and heart |

|(Noradrenaline) | |rate |

Zona Fasciculata (Blue = parallel bundles of spongiocytes; Red = Spongiocytes)

Zona Reticularis (Red = Reticular Fibers)

V. Pineal Gland: (Look for accumulation of calcified material = BRAIN SAND)

Location: in brain (third eye)

∙ connected to third ventricle of brain

∙ covered by the Pia Mater

∙ associated with capillary supply

2 Types of Cells:

1. Pinealicytes: (major cell type) found in clumps and highly branched

2. Neuroglial: (supporting cells) flattened nuclei

Secrets:

|Hormone |Main Effects |

|Melatonin |Released in response to darkness : regulates circadian rhythm |

Blue = Pinealcytes ; Red = Brain Sand

VI. Pancreas: digestive organ possessing both endocrine and exocrine functions

Location: adjacent to stomach and duodenum of small intestine

Endocrine Functions:

Islets of Langerhans- found scattered between exocrine acini of the pancreas; arranged in clumps between capillaries

2 Cell Types (responsible for identifying):

1. Alpha Cells: (secrete glucagon)

- darker nuclei and more eosinophilic cytoplasm

- periphery of Islet

- flatter/ smaller nuclei

1. Beta Cells: (secrete insulin)

- majority of cells in the Islet

- center of Islet

- rounder/larger nuclei

Secrets:

|Hormone |Source |Main Effects |

|Glucagon |Alpha cells |Increases blood sugar levels; induces |

| | |glycogenolysis (conversion of glycogen to |

| | |glucose); fat and protein in to energy |

| | |metabolites |

|Insulin |Beta Cells |Decrease blood sugar levels; storage of |

| | |nutrients absorbed from the intestine into |

| | |glycogen, protein, and fat |

|Somatostatin * |Delta Cells* |Reduce rate of food absorption from the |

| | |intestine. * |

|Pancreatic Peptide* |Gamma Cells* |Reduces appetite* |

* = not responsible for knowing in lab

Red = Beta Cells ; Blue = Alpha Cells ; White = Acinar Cells (Exocrine)

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