Download Thyroid Gland - Claire Simms, DVM VTI

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Consists of two lobes on each side of
larynx
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The thyroid gland is composed of tens
of thousands of _____________.
 Each follicle consists of a sphere of
cuboidal glandular cells
surrounding colloid, which contains
thyroid precursor for later use
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Produces two hormones: _________
hormone and __________________
Thyroid Gland
 Thyroid hormone is actually two
hormones: T3 and T4 (triiodothyronine
and thyroxine)
 Produced when TSH from ant pituitary
reaches thyroid gland
 T4 produced in greater abundance
than T3 but is mostly converted to T3
before producing effects on target cells
 ______ more potent and considered the
main thyroid hormone.
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Effects of Thyroid Hormones
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_____________________ effect - regulates metabolic rate (BMR)
 Allows an animal to generate heat and maintain a constant internal body
temperature, when outside temperature changes.
 Production of thyroid hormone increases with exposure to cold
temperatures.
► Increases body’s __________________, which generates more ______.
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Effect on Protein, Carbohydrate, and Lipid Metabolism
 Proteins:
► Encourages synthesis of proteins if diet is adequate in energy sources.
► If energy sources are not adequate in diet, then can actually __________
proteins.
 Carbohydrates:
► Hyperglycemic effect.
► Helps to maintain homeostasis of the blood glucose level by helping to
prevent it from dropping too low.
 Lipids:
► Encourages their ________________________.
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Hypothyroidism
• Inadequate amount of hormone
produced.
• Occurs commonly in middle age ____.
• Symptoms include:
• Alopecia
• Dry skin
• Lethargy
• Reluctance to exercise
• Weight gain/ decreased metabolism
• Seeking out sources of heat.
• Easily treated with thyroid
supplementation
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Hyperthyroidism
• Too much thyroid hormone production.
• Most common endocrine disorder seen in _____.
• Symptoms include:
• Nervousness/irritability/excitability
• Weight loss
• polyphagia, but no weight gain
• Tachycardia
• Vomiting
• Diarrhea
• Polyuria
• Polydipsia
• Treated surgically by removing the thyroid gland, radioactive
treatment, or drugs to suppress thyroid production.
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Goiter
• Non-cancerous, non-inflammatory enlargement of the
thyroid gland.
• Results from ____________ deficient diet
• Because iodine is an important component of
thyroid hormone, a deficiency of iodine results in
a deficiency of thyroid hormone.
• The anterior pituitary attempts to compensate by
producing more TSH. This overstimulates the thyroid
gland, causing ___________________.
• Can be treated and prevented with iodine
supplements.
• Iodized salt should be added to diets if they are
known to be deficient.
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Produced by C cells (parafollicular cells) located between thyroid follicles
Maintains homeostasis of blood _______________ levels
 Calcium is necessary for muscle contraction, blood clotting, milk
secretion, and formation/maintenance of skeleton. Calcium levels must
be kept within a narrow range to allow these to take place normally.
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Prevents _______________ by decreasing blood calcium levels if they
get too high.
 Encourages excess calcium to be deposited into the bones.
Calcitonin
(the other Thyroid hormone)
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Parathyroid Hormone (PTH)
also called parathormone
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Produced by parathyroid glands
 Small, pale nodules in, on, or near the thyroid glands
Helps maintain blood Calcium levels by producing the _____________effect
of calcitonin
 Prevents ______________ by increasing blood calcium if gets too low.
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Causes kidneys to retain calcium and intestines to absorb calcium from food.
► Can take calcium out of storage from the bones.
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Hypocalcemia
• Milk fever- when parathormone is overwhelmed in ____________ animals.
• Called _____________ in small animals
• Can cause muscle weakness and tremors.
• Can progress to seizures and spasms if left untreated.
• “____________ cows”
• Treated by supplementing calcium rapidly into system
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Adrenal glands are located near cranial ends of
kidneys
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Adrenal cortex
 Classic endocrine gland tissue
 Produce (under direction of ACTH):
► __________________
hormones (cortisol)
 Cause blood glucose levels to rise
due to protein and lipid catabolism
causing gluconeogenesis
 Also increase body’s resistance to
stress, decrease immune response,
and decrease inflammation
► ________________
hormones (aldosterone)
 Affects the levels of Na, K, and H in the
body
 Increase sodium reabsorption and
potassium/hydrogen excretion in the
kidneys
Adrenal
Cortex
► _____hormones
(androgens and estrogens)
 small amount with minimal effects
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Hyperadrenocorticism = ____________ Disease.
Symptoms include:
PU/PD/PP
Hair loss
Muscle wasting
Pot belly
Slow wound healing
Usually caused by pituitary tumor, but can be
caused by adrenal tumor or iatrogenic
administration of steroids
Hypoadrenocorticism=_______________ Disease.
Lack of mineralcorticoids and or glucocorticoids
causing decreased Na and increased K
Symptoms include:
Weakness
Lethargy
Vomiting
Diarrhea
Weight loss
Can be caused by a sudden withdrawal of
corticosteroid drugs
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 Adrenal medulla
► Resembles ____________ tissue
► Controlled
by sympathetic portion of
nervous system (fight or flight)
► Produces:
 Epinephrine and norepinephrine
► Increases
HR and CO, increases BP,
dilates air passageways in lungs, and
decreases GI function
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Adrenal
Medulla
Pancreas
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Located near ______________
 Both exocrine and endocrine functions
► Endocrine component - small % of total organ volume
►Pancreatic islets (islets of Langerhans): groups of cells
scattered throughout the pancreas
 Alpha cells - produce _______________
 Beta cells - produce _______________
 Delta cells - produce ________________
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Pancreatic
Hormones
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Insulin: _________ blood glucose
 Causes glucose, amino acids, and fatty
acids to be absorbed into body cells
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Glucagon: ________ blood glucose
 Stimulates liver cells to convert stored
glycogen to glucose
 Stimulating gluconeogenesis
► Amino
acids and fatty acids converted to
glucose
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Somatostatin: Inhibits release of
insulin, glucagon, and Growth
Hormone, and decreases GI activity
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Pancreatic Dysfunction:
Diabetes Mellitus
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•
•
•
Caused by deficiency of _________
Results from build up of _________
Symptoms include:
 Polyuria
 Polydipsia
 Polyphagia
 Weight loss
 Weakness
Not curable but treatable through
injections of insulin and diet
changes
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Gonads: Testes
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Interstitial cells: clumps of
endocrine cells
 Produce testosterone when
stimulated by _____
► a.k.a.
“interstitial cell
stimulating hormone” (ICSH)
in the male
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Testosterone: primary
androgen
 Provides for development of male
secondary sex characteristics and
accessory sex glands
 Necessary for spermatogenesis
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Gonads: Ovaries
Produce ______ (eggs) and hormones in cycles
► Controlled by ________ and ____(from anterior pituitary)
► Hormones produced in
ovaries:
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1.Estrogens
2.Progesterone
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__________ stimulates ovarian follicles to
develop
 Cells of follicles produce and release
________________
 Amount of estrogen produced
increases as follicle grows
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Increasing estrogen levels cause physical
and behavioral changes
 Swollen vulva
 Receptive to male
 Feedback to anterior pituitary: increased
estrogen causes anterior pituitary to
__________production of FSH and
__________ production of LH
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Estrogen
When follicle is fully mature, LH level peaks
 In most animal species, ___________
occurs when LH peaks
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Group of hormones produced by
___________ ____________ (CL)
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High ___ level stimulates cells of empty
follicle to multiply and develop into CL
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Progesterone - principal progestin
 Prepares uterus to receive fertilized
ovum
 Needed to maintain ___________
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In pregnant female, hormone signal
(varies between species) is sent from
uterus, and CL is maintained
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If no pregnancy occurs, lack of hormone
signal causes CL to shrink and disappear
Progestins
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Produce _________________ stimulates red bone marrow
to increase production of
RBCs
►Stimulated
by hypoxia, loss
of RBCs, increased aerobic
exercise
►As
RBC production increases,
more oxygen is delivered to
kidneys, which slows production of
erythropoietin
Kidneys
►Lack
of production may result in
anemia
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Stomach and Small Intestines
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Stomach: ________ is produced by G-cells in the wall of
the pyloric antrum
 Stimulated by the presence of food in the stomach
 Causes HCl secretion, digestive enzyme secretion, and encourages
contraction of the stomach
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Small Intestines: Chyme entering the small intestines
causes Secretin and CCK to be released
 Both cause the stomach motility to decrease and inhibit gastric
secretions
 __________ stimulates the pancreas to secrete bicarbonate into the
duodenum to neutralize the acidity of chyme
 _______ stimulates the gallbladder to contract, allowing bile to aid
in the digestion of fats
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Placenta
► Surrounds
developing fetus during pregnancy
► Acts as interface with maternal circulation
► Produces hormones to support and maintain
pregnancy
 Small amounts of ___________ and _________________
are produced to help maintain pregnancy
 Chorionic gonadotropin (horses, humans)
► Basis
for OTC pregnancy tests
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Located in the cranial _____________
Very important during early
development, will _______ as animal
approaches adulthood.
Important in immune system
development
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Produces:
 Thymosin
 Thymopoietin
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Seem to transform cells of the thymus
into t-lymphocytes (_________) which
help to attack foreign invaders in the
body.
Thymus
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Pineal Body
► Influences
body’s biological clock
► ________________ – hormone-like substance that
affects moods and wake-sleep cycles
 Also plays a role in timing of seasonal estrous cycles in some
species
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Melatonin
Production varies with daylight
-sets body’s biological clock
Production varies with age
-associated with sleep patterns
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Prostaglandins
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Derived from unsaturated fatty acids
► Sometimes called tissue hormones due to the fact they travel short
distances.
► Organized in groups A-I
► Produced in a variety of body tissues including:
 Skin, intestines, brain, kidneys, lungs, reproductive organs, eye
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Effects:
 Influence blood pressure, GI function, Respiratory function,
Kidney function, Blood clotting, Inflammation, Reproductive
functions
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PGE’s initiate inflammation, so NSAIDs inhibit PGE production.
► PGF2- alpha is used to synchronize estrous cycles in livestock
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