Thyroid Gland & Parathyroid (6&7)

Question 1

Thyroid gland of mammals

Answer 1

Usually bilobed and located just caudal to the larynx, adjacent to the lateral surface of the trachea

Question 2

Thyroid gland of birds

Answer 2

Within the thoracic cavity; both lobes are located near the syrinx, adjacent to the carotid artery near the origin of the vertebral artery.

Question 3

thyroid gland of ruminants and horses

Answer 3

lobes may be connected by a fibrous isthmus

Question 4

thyroid gland in dogs and cats

Answer 4

-connecting isthmus may be indistinct
-ectopic or accessory thyroid tissue is common.

Question 5

Thyroid gland in pigs

Answer 5

main lobe is in the midline

Question 6

the main secretory product of the normal thyroid gland.
-inactive form

Answer 6

Thyroxine (T4)
-also called Tertraiodothyronine

Question 7

3-5 Times more potent than T4
-active form

Answer 7

Triiodothyronine (T3)

Question 7

T2

Answer 7

Diiodotryosine

Question 8

How is thyroid hormone secretion is regulated?

Answer 8

Thyroid hormone secretion is regulated primarily via negative
feedback control through the coordinated response of the
hypothalamic pituitary thyroid axis: thyrotropin releasing hormone
(TRH) binds to the thyrotroph cell in the pituitary and stimulates
secretion of thyrotropin (thyroid stimulating hormone, TSH), which
binds to the follicular cell membrane and stimulates thyroid
hormone synthesis and secretion.

Question 9

Action of thyroid hormone

Answer 9

1. Metabolism
   -Lipid metabolism, Carbohydrate metabolism
2. Growth
3. Development
4. other effects: cardiovascular system, Central nervous system, reproductive system.

Question 10

Action of thyroid hormone on metabolism

Answer 10

increasing basal metabolic rate. One consequence of this activity is to increase body heat production, which seems to result, at least in part, from increased oxygen consumption and rates of ATP hydrolysis.

Question 11

Action if thyroid hormone on lipid metabolism

Answer 11

-Increased thyroid hormone levels stimulate fat mobilization, leading
to increased concentrations of fatty acids in plasma.
-They also enhance oxidation of fatty acids in many tissues. Finally,
plasma concentrations of cholesterol and triglycerides are inversely
correlated with thyroid hormone levels one diagnostic indication of
hypothyroidism is increased blood cholesterol concentration.

Question 12

Action of thyroid hormone in carbohydrate metabolism

Answer 12

stimulate almost all aspects of carbohydrate metabolism, including
enhancement of insulin dependent entry of glucose into cells and
increased gluconeogenesis and glycogenolysis to generate free
glucose.

Question 13

ACTION OF THYROID HORMONE on Growth

Answer 13

Thyroid hormones are anabolic. In conjunction with growth hormone
and insulin, protein synthesis is stimulated and nitrogen excretion is
reduced.

Question 14

Action of thyroid hormone on development

Answer 14

essential to the development of the fetal and neonatal brain

Question 15

Action of thyroid hormone on cardiovascular system

Answer 15

Thyroid hormones increases heart rate,
cardiac contractility and cardiac output. They also promote vasodilation, which
leads to enhanced blood flow to many organs.

Question 16

Action of thyroid hormones on Central nervous system

Answer 16

Both decreased and increased
concentrations of thyroid hormones lead to alterations in mental state. Too little
thyroid hormone makes the animal sluggish, while too much induces anxiety
and nervousness.

Question 17

action of thyroid hormone on reproductive system

Answer 17

Normal reproductive behavior and physiology is
dependent on having essentially normal levels of thyroid hormone.
Hypothyroidism in particular is commonly associated with infertility.

Question 18

they can be catabolic, with increased
gluconeogenesis, protein breakdown, and nitrogen wasting.
This is common in cats. Common clinical signs include
weight loss despite an increased appetite, nervousness, excitability,
vomiting after eating, and increased thirst and urination.

Answer 18

Hyperthyroidism

Question 19

manifest symptoms that include decreased
energy, lethargy, weight gain, dry skin, and hair loss. In young
animals, most commonly leads to stunted growth and
dwarfism.

Answer 19

Hypothyroidism

Question 20

A hormone known to participate in calcium and phosphorus metabolism.
1. Major source is from?
2.Where is it secreted in birds, fish, amphibians

Answer 20

Calcitonin
1. parafollicular or C cells in the thyroid gland.
2. ultimobranchial glands

Question 21

Physiologic effects of calcitonin in bones

Answer 21

Suppresses resorption of bone by inhibiting the activity of osteoclasts. Preventing calcium release into blood and stimulates phosphorus excretion in urine

Question 22

Physiologic effects of calcitonin in kidney

Answer 22

Calcium and phosphorus are prevented from being lost in urine
by reabsorption in the kidney tubules. Calcitonin inhibits tubular
reabsorption of these two ions, leading to increased rates of their loss in
urine.

Question 23

Physiologic effects of calcitonin in fish, rodents, and some domestic animals

Answer 23

play a significant role in calcium homeostasis

Question 24

Small, light-colored nodules on protruding from its surface. "Besides the thyroid" -What hormone those these glands produce

Answer 24

Parathyroid glands -Parathyroid hormone (PTH) or parathormone

Question 25

The most important endocrine regulator of calcium and phosphorus concentration in extracellular fluid. -major target cells?

Answer 25

Parathyroid gland / hormone - bone and kidney

Question 26

Physiologic effects of the parathyroid hormone

Answer 26

1. Mobilization of calcium from bone. 2. Enhancing absorption of calcium from the small intestine 3. Suppression of calcium loss in urine

Question 27

PTH process on the mobilization of calcium from bone

Answer 27

stimulate osteoclasts to reabsorb bone minerals, liberating calcium into the blood.

Question 28

PTH process on Enhancing absorption of calcium from the small intestine

Answer 28

Parathyroid hormone stimulates this process, but indirectly by stimulating the production of the active form of Vitamin D in the kidney. Vitamin D induces the synthesis of a calcium binding protein in intestinal epithelial cells that facilitates efficient absorption of calcium into the blood.

Question 29

PTH process on suppression of calcium loss in urine

Answer 29

Parathyroid hormone puts a brake on the excretion of calcium in urine, thus conserving calcium in the blood. This effect is mediated by stimulating tubular reabsorption of calcium. Another effect of parathyroid hormone on the kidney is to stimulate the loss of phosphate ions in urine. This effect of PTH on the kidneys is most rapid.

Question 30

Refers to low blood calcium concentration. - Clinical signs?

Answer 30

Hypocalcemia -neuromuscular excitability, spasms, tetany, cardiac dysfunction.

Question 31

a concentration of blood calcium higher than normal.

Answer 31

Hypercalcemia

Question 32

Importance of Calcium

Answer 32

-essential structural component of the skeleton -Plays a role in muscle contraction, blood coagulation, enzyme activity, neural excitability, secondary messengers, hormone release, membrane permeability.

Question 33

Major pools of calcium in the body

Answer 33

1. Intracellular calcium 2.Calcium in blood and extracellular fluid. 3. Bone calcium

Question 34

Site where the dietary calcium is absorbed.

Answer 34

Small intestine -dependent on expression of a calcium-binding protein in epithelial cells

Question 35

this structure serves as a vast reservoir of calcium.

Answer 35

Bone

Question 36

Function of kidney in calcium homeostasis

Answer 36

The kidney is critically important in calcium homeostasis. Under normal blood calcium concentrations, almost all of the calcium that enters glomerular filtrate is reabsorbed from the tubular system back into blood, which preserves blood calcium levels. If tubular reabsorption of calcium decreases, calcium is lost by excretion into urine.

Question 37

A hormone that functions to reduce blood calcium levels. -Secreted in response to hypercalcemia -what are its effects?

Answer 37

Calcitonin - Suppression of renal tubular reabsorption of calcium. -inhibition of bone resorption, which would minimize fluxes of calcium from bone into blood

Question 38

The actions of PTH and calcitonin

Answer 38

They are antagonistic on bone resorption but synergistic in decreasing the renal tubular reabsorption of phosphorus

Question 39

Hormones that may contribute to the maintenance of calcium homeostasis

Answer 39

Adrenal corticosteriods, estrogens, thyroxine, somatotropin, glucagon