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Hormones                                   Target Gland
Melanotrophins (MSH)                 .................

Pineal Gland.

a

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Define the following:
(a) Exocrine gland
(b) Endocrine gland
(c) Hormone


(a) Exocrine gland : Glands which pour their secretions through the ducts eg Liver and Pancreas.

(b) Endocrine gland : Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into the blood rather than through a duct. They are ductless. 

(c)Hormone : Hormones are non-nutrient chemicals which act as intercellular messengers and are produced in trace amounts. 
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 Hormones                                   Target Gland

(d) Gonadotrophins (LH, FSH)          ..........

Testis and ovary.

a

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Write short notes on the functions of the following hormones.

(a) Parathyroid hormone (PTH)
(b) Thyroid hormones
(c) Thymosins
(d) Androgens
(e) Estrogens
(f) Insulin and Glucagon.


(a) Parathyroid horomone : 

Parathyroid hormone (PTH) is relesed by the parathyroid glands. It is a peptide hormone. 

Function - The PTH performs the following function:
i. Increases the Ca2+ level in the blood and maintains the calcium balance in the body. 
ii. It acts on bones and stimulates the process of demineralisation. 
iii. It stimulate the reabsorption of the Ca2+ by the renal tubules.
iv. It increases the calcium absorption from the digested food. 

(b)  Thyroid hormones :

Thyroxine/ Tetraiodothyonine (T4) and triiodothyronine (T3) are collectively known as thyroid hoemones. They are secreted by the follicular cells of the thyroid gland and are peptide hormones.

Functions - They perform the following functions.

i. Regulate the basal metabolic rate
ii. Support the red blood cells formation. 
iii. Control the metabolism of carbohydrates, proteins and fats.
iv. Maintain the water and electrolyte balance.
v. Regulate the blood calcium levels.  

(c) Thymosins

Thymosins are released by the thymus gland. They are peptide hormones. 

Functions - They peform the following functions. 

i. Play a major role in the differentiation of T-lymphocytes.
ii. Promote the production of antibodies. 

(d) Androgens 

Androgens are the secreted by the Leydig cells or interstitial cells. Androgens are a group of hormones that consist mainly testosterone. 

Function - They perform the following functions.

i. Regulate the development, maturation and functions of the male accessor sex organs in males.
ii. Stimulate development of secondary sexual characters in males.
iii. Stimulate the process of spematogenesis.
iv. Produce anabolic effect on protein and carbohydrate metabolism.

(e) Estrogens  

Estrogen is secreted by ovary. It is a steroid hormone synthesied by ovarian follicles. 

Functions - They perform the following functions:

 Stimulate the growth and activity of female secondary sex organs. and regulate the female sexual behaviour

(f) Insulin and Glucagon

These are released by the pancreas. The insulin hormone is synthesized by the beta-cells and the glucagon is synthesized by the alpha-cells. 

Functions : They perform the following functions. 

i. They maintain the glucose homeostasis.
ii. The glucagon acts on the liver cells and result in glycogenolysis and thus in the increased glucose levels in the blood. It also reduces the glucose uptake and utilisation. 
iii. Insulin decreases the blood glucose level and enhaces cellular glucose uptake and utilisation. 

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List the hormones secreted by the following

(1) Hypothalamus ,(2) Pituiltary gland , (3) Thyroid gland
(4) Parathyroid gland , (5) Adrenal gland, (6) pancreas

(7) Testis, (8) Ovary, (9) Thymus

(10) Atrium, (11) Kidney , (12) G–1 Tract.


(1) Hypothalamus :

It secretes following hormones:

(a) Hypothalamus: Hormones secreted by the hypothalamus include:

(1) Releasing hormones: These hormones stimulate the secretions of the pituitary hormone. Examples of these hormones are:
(i) Gonadotrophin-releasing hormone
(ii) Thyrotrophin-releasing hormone
(iii) Somatotropin-releasing hormone
(iv) Adrenocorticotrophin-releasing hormone

(2) Inhibiting hormones: These hormones inhibit the secretions of the pituitary hormone. Examples of these hormones are:
(i) Somatostatin
(ii) Growth-inhibiting hormone
(iii) Melanocyte-inhibiting hormone


(2) Pituitary gland :
 Pituitary gland is divided into.

(i) Adeno hypophysis (ii) Neuro hypophysis 

Hormones secreted by the adenohypophysis are:
(i) Growth hormone (GH)
(ii) Prolactin
(iii) Thyroid-stimulating hormone (TSH)
(iv) Adrenocorticotrophic hormone (ACTH)
(v) Luteinizing hormone (LH)
(vi) Follicle-stimulating hormone (FSH)
(vii) Melanocyte-stimulating hormone (MSH)

Hormones secreted by the neurohypophysis are:
(i) Oxytocin
(ii) Vasopressin

(3) Thyroid gland :

Follicle cells of thyroid gland secrete two hormones.

Tetraidothyronine (T4)

Tridothysonine (T3)

C cells of thyroid also secrete thyrocalcitonin.


(4) Parathyroid gland : It secretes parathyroid hormone .

(5) Adrenal gland :
The adrenal gland has outer
(i) Adrenal cortex
(ii) Adrenal medulla.

(i) Adrenal cortex has three parts :

(a) Outer part or zona glomerulosa : It secretes mineral corticoids.

(b) Middle part or zona fasciculata : It secretes glucocorticoids,.

(c) Inner part or zona reticularis : Both middle and inner part secrete sex corticoids.

(ii) Adrenal medulla :
It secretes
i. epinephrine or adrenaline hormone
ii. noradrenaline or norepinephrine hormone.

(6) Pancreas : Its cells called Islets of Langerhans are of two types :

(a) α cells : These secrete glucagon hormone. (b) β cells : These secrete insulin.

(7) Testis: It has interstitial cells or cells of leydig which secrete androgens mainly testosterone.

(8) Ovary: The graafian follicle secretes estrogen hormone.

Corpus luteum secretes progesterone and relaxin hormone.

(9) Thymus :
It secretes thymosin hormone.


(10) Atrium : The atrial wall secretes atrial natiuretic factor (ANF)

(11) Kidney : The juxtaglomerular cells of kidney produce erythropoietrin hormone.

(12) G–1 Tract :

It secretes following hormones.
(i) secretin
(ii) cholecystokinin (CCK)
(iii) enterogastrone or gastric inhibitory peptide (GIP)
(iv) Villikinin
(v) Duocrinin
(vi) Enterocrinin.

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