thorid Structure thyorid Location thyorid hormones feedback mechanism Parathyorid gland its location and hormones

1. Date:- 23-11-2016
Assignment Topic:
THYORIDE & PARARTHYORIDE GLAND
SubmittedTo:- Mam SHAFFAF NIZZAMI
SubmittedBy:-
 Name: HIRA AROOJ
 Roll No. 1420425 (502)
 Class: BS-lll
 Semester: v
 Subject: Physiology
 Discipline: Zoology
Govt. College For Women Gulberg LHR

2. CONTENTS:
Thyroid gland: ............................................................ 3
 Location:............................................................... 3
 Thyoride Hormones:-............................................ 3
 Functions of Thyoride Hormone:-.......................... 3
 Regulation Of Thyoride Hormone:........................ 4
 Calcitonin:- ........................................................... 5
Parathyoride Gland: ................................................... 6
 Location:............................................................... 6
 Parathyroid Hormone:.......................................... 6
 Role Of Calcium: ................................................... 6
 Regulation Of PTH………………………….…………………...6
 References:…………………………………………………………………….…7

3. Thyroid gland:
A gland that makes and stores hormones that help regulate the heart rate, blood pressure,
body temperature, and the rate at which food is converted into energy.
Location:
The thyroid gland is located in the lower part of the neck, below the Adam's apple, wrapped
around the trachea (windpipe). It is butterfly-shaped. The thyroid has two lobes that lie on
either side of windpipe, and is usually connected by a strip of thyroid tissue known as an
isthmus.
Thyoride Hormones:-
The primary function of the thyroid is the production of iodine containing hormones,
 Triiodothyronine (T3)
 Thyroxine (T4)
 Peptide hormone calcitonin.
T3 is so named because it contains three atoms of iodine per molecule and T4 contains four
atoms of iodine per molecule. The thyroid hormones have a wide range of effects on the
human body.
Functions of Thyoride Hormone:-
Metabolic:-
The thyroid hormones increase the basal metabolic rate and have effects on almost all body
tissues. Appetite, the absorption of substances, and gut motility are all influenced by thyroid
hormones. They increase the absorption in the gut, creation, uptake by cells and breakdown of
glucose. They stimulate the breakdown of fats, and increase free fatty acids. Despite increasing
free fatty acids, thyroid hormones decrease cholesterol levels, perhaps by increasing the rate of
secretion of cholesterol in bile.

4. Cardiovascular:-
The hormones increase the rate and strength of the heartbeat. They increase the rate of breathing,
intake and consumption of oxygen, and increase the activity of mitochondria. Combined, these
factors increase blood flow and the body's temperature.
Developmental:
Thyroid hormones are important for normal development. They increase the growth rate of
young people, and cells of the developing brain are a major target for the thyroid hormones
T3 and T4. Thyroid hormones play a particularly crucial role in brain maturation during fetal
development.
Regulation Of Thyoride Hormone:
It is important that T3 and T4 levels are neither too high nor too low. The body has a complex
mechanism for adjusting the level of thyroid hormones. First, the hypothalamus, located
just above the pituitary gland in the brain, secretes thyrotropin -releasing hormone (TRH),
which causes the pituitary gland to produce thyroid-stimulating hormone (TSH). Just as the
name suggests, TSH stimulates the thyroid gland to produce thyroid hormones. The
pituitary gland slows or speeds the release of TSH, depending on whether the levels of
thyroid hormones circulating in the blood are getting too high or too low.

5. Calcitonin:-
Calcitonin is a hormone secreted by the thyroid gland that reduces the
concentration of blood calcium level when it has risen to an above normal level. This
polypeptide hormone is made up of 32 amino acids and is produced mainly by the parafollicular
cells (also known as C cells) of the thyroid gland. In fish, birds and other non-mammalian
animals, calcitonin is produced by cells of the ultimobranchial body.
Calcitonin opposes the effects of parathyroid hormone (PTH), which acts to
increase the blood calcium level. Calcitonin lowers blood calcium levels by suppressing
osteoclast activity in the bones and increasing the amount of calcium excreted in the urine. The
hormone also prevents the absorption of calcium from the intestine, as well as increasing the
calcium absorbed by the kidney. However, the production and increased activity of calcitonin is
only short-lived and many patients with chronic hypercalcemia (raised blood calcium) do not
have high blood calcitonin levels. A high calcitonin concentration can be an indicator of
medullary thyroid carcinoma, a cancer of the parafollicular cells which leads to the secretion of
large amounts of calcitonin.

6. Parathyoride Gland:
Location:
The parathyroid glands are organs situated behind the thyroid gland and each is about half the
size of a grain of rice. They are called the parathyroid glands due to their proximity to the
thyroid gland, but the parathyroid glands and the thyroid gland are completely different organs.
Normally, there are a total of four parathyroid glands, with a pair of parathyroid glands (one
above the other) behind each of the two thyroid lobes.
Parathyroid Hormone:
The parathyroid glands secrete parathyroid hormone (PTH). Parathyroid hormone "regulates
the metabolism of calcium". Parathyroid hormone and calcitonin are antagonistic hormones,
which are released in response to blood calcium levels. In other words, PTH acts on the same
target organs as calcitonin, but produces the opposite effects. Parathyroid hormone is released
from the parathyroid glands, and calcitonin is released from the thyroid gland. Parathyroid
hormone is released when blood calcium concentration is too low. PTH activates osteoclasts in
bone. This causes reabsorption of calcium from the bone and release into the blood, restoring
normal blood levels of calcium.
Role Of Calcium:
Calcium is not only a major component of bones, but is also indispensable
for blood clotting and for the contraction of every muscle in the body, including the heart. It is
also an essential mineral for the proper functioning of brain cells. Calcium is stored in the
bones. Its release from the bones into the blood, as well as its absorption in the kidneys or
intestines, is regulated by parathyroid hormone along with vitamin D. Thus, parathyroid
hormone and vitamin D have the function of increasing calcium levels in the blood.
Regulation Of PTH:
Calcium levels can affect the secretion of parathyroid hormone. Low
levels of calcium in the blood induce the secretion of parathyroid hormone, resulting in

7. increased calcium levels. On the other hand, high levels of calcium in the blood inhibit the
secretion of parathyroid hormone, leading to decreased calcium levels. In this manner, calcium
levels in the blood are regulated.
References:
 http://www.hormone.org/hormones-and-health/what-do-hormones-do/what-
does-the-thyroid-gland-do
 http://biology-forums.com/index.php?topic=15641.0
 http://www.webmd.com/a-to-z-guides/parathyroid-hormone#1
 http://www.endocrineweb.com/conditions/thyroid/how-your-thyroid-works