Download Animal Histology- Endocrine System:

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
Oxytocin
Target
Uterus/Mammary Glands
Antiduretic Hormone
(ADH) or Vasopressin
Kidneys or Arterioles
Main Effects
Uterine contractions;
lactation
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
ACTH/Adrenocorticotropic
hormone (Corticotropin)
Endorphins
Secretory Cell Type
Corticotrophs (Basophils)
______
Target
Main Effects
Adrenal Gland
Secretion of Glucocorticoids
Opioid receptors
Inhibit pain perception
Ovaries/ Testes
Reproduction System
Growth
Liver, Adipose Tissues
Promotes Growth: lipid and
carbohydrate metabolism
FSH/ Follicle Stimulating
Hormone
Gonadotrophs (Basophils)
Human Growth Hormone
(Somatrotropin)
Somatotrophs (Acidophils)
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
Thyroid Gland
Secretion of Thyroid
Hormone
TSH/ Thyroid Stimulating
Hormone
Thyotrophs (Basophils)
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
Thyroid Hormone
Cell Source
Follicular Cells
Calcitonin
Parafollicular Cells
Main Effects
Stimulates metabolic
activity
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
Parathyroid Hormone
Main Effects
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
Glucocorticoids (type of
steroid hormone)
Source
Adrenal Cortex
Mineralocorticoids (type
of steroid hormone)
Epinephrine (Adrenaline)
& Norepinephrine
(Noradrenaline)
Adrenal Cortex
Adrenal Medulla
Main Effects
Increases blood glucose
levels and decreases protein
synthesis
Increases water reabsoprtion
in the kidney
Increases blood glucose
levels and heart 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
Melatonin
Main Effects
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
2. Beta Cells: (secrete insulin)
- majority of cells in the Islet
- center of Islet
- rounder/larger nuclei
Secrets:
Hormone
Glucagon
Source
Alpha cells
Insulin
Beta Cells
Somatostatin *
Delta Cells*
Pancreatic Peptide*
Gamma Cells*
Main Effects
Increases blood sugar
levels; induces
glycogenolysis (conversion
of glycogen to glucose); fat
and protein in to energy
metabolites
Decrease blood sugar levels;
storage of nutrients
absorbed from the intestine
into glycogen, protein, and
fat
Reduce rate of food
absorption from the
intestine. *
Reduces appetite*
* = not responsible for knowing in lab
Red = Beta Cells ; Blue = Alpha Cells ;
White = Acinar Cells (Exocrine)