Animal Histology - Endocrine

8/12/2019 Animal Histology - Endocrine

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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 growthor metabolism. A chemical produced in one part of the body and released into the bloodto trigger or regulate particular functions of the body.

Endocrine glands: Glands that produce and secrete hormones into the blood or lymphsystems, 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.


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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)


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1. Pars Nervosa (Posterior Pituitary or Neurohypophysis) contains axonal projections of HH tract (hypothalamohypophysealtract)

Secretes:

Hormone Target Main EffectsOxytocin Uterus/Mammary Glands Uterine contractions;

lactation

Antiduretic Hormone

(ADH) or Vasopressin

Kidneys or Arterioles Stimulates water retention;

raises blood pressure bycontracting arterioles

3 Features to Know:

axons have product accumulating around end bulb = palisadeszone herringbodies= accumulation of secretory products in axon terminal bulbs

supporting cell type = pituicyte

Red = Pituicyte; Blue = Herring Body


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2. Pars Tuberalis (refer to above overall picture of pituitary gland) entrance of the hypophysioportal blood system into the anterior pituitary

(wraps thepituitary 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 thepituitary

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)
http://en.wikipedia.org/wiki/Pituitary_stalkhttp://en.wikipedia.org/wiki/Pituitaryhttp://en.wikipedia.org/wiki/Pituitaryhttp://en.wikipedia.org/wiki/Pituitary_stalk


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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 (Corticotropin)

Corticotrophs (Basophils)Adrenal Gland Secretion of Glucocorticoids

Endorphins ______ Opioid receptors Inhibit pain perception

FSH/ Follicle StimulatingHormone

Gonadotrophs (Basophils) Ovaries/ Testes Reproduction SystemGrowth

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


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Blue = Acidophils (Chromophils);

Yellow = Chromophobes; Red = Basophils Chromophils)


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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. Follicularcells:

-arranged as a simple cuboidal epitheliumwith 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 CalciumLevels


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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: majorcell type; small cellswith spherical nuclei, and palestaining, granular cytoplasm. (less cytoplasm around nuclei)


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

Secretes:

Hormone Main EffectsParathyroid Hormone Increases blood calcium

levels


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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, chromaffincells(ovoid basophilic cells) arranged in clumps/irregular cordsaround an extensive capillary system.


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Secrets:

Hormone Source Main Effects

Glucocorticoids (type of

steroid hormone)

Adrenal Cortex Increases blood glucose

levels and decreases protein

synthesisMineralocorticoids (type

of steroid hormone)

Adrenal Cortex Increases water reabsoprtion

in the kidney

Epinephrine (Adrenaline)

& Norepinephrine

(Noradrenaline)

Adrenal Medulla Increases blood glucoselevels and heart rate


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Zona Fasciculata (Blue = parallel bundles of

spongiocytes; Red = Spongiocytes)

Zona Reticularis (Red = Reticular

Fibers)


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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


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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

2. 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 sugarlevels; induces

glycogenolysis (conversion

of glycogen to glucose); fatand protein in to energy

metabolites

Insulin Beta Cells Decrease blood sugar levels;

storage of nutrients

absorbed from the intestineinto glycogen, protein, and

fat

Somatostatin * Delta Cells* Reduce rate of foodabsorption from the

intestine. *

Pancreatic Peptide* Gamma Cells* Reduces appetite*

* = not responsible for knowing in lab


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Red = Beta Cells; Blue = Alpha Cells;

White = Acinar Cells (Exocrine)


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Animal Histology - Endocrine