for class XII

Endocrine gland

Endocrine gland is the gland without duct for secreting. The secretions are defused into blood. Through blood circulation, reach various parts of body. These secretions or hormones control, coordinate and integrate various physiological processes and activities of body. Different endocrine glands together make endocrine system in the body.

Differences

Exocrine endocrine
Gland with ducts ductless gland
Found near site of action usually found way from the site of action also
Secretions are enzymes secretions are hormones

Glands are either endocrine or exocrine but pancreas is both exocrine and endocrine in function. The endocrine part produces insulin and glucagons that regulate metabolism of glucose. The exocrine part produces pancreatic juice for digestion of food. It is called heterocrine gland.

Differences between hormone and enzyme


Pituitary gland
This is important gland. The other endocrine glands are influenced by hormones of this gland. So pituitary gland is called master gland.
Locaton it is found at the base of brain below diencephalons and enclosed in a depression. It is also known as hypophysis. It is small about size of a pea na weighs about 5 gm.

It consists of three lobes
1. anterior lobe
2. intermediate lobe
3. posterior lobe
the anterior and intermediate lobes are together known as adenohypophysis. The posterior lobe is known as neurohypophysis.

Adenohypophysis secretes 7 hormones
1. Follicle Stimulating Hormone FSH
Functions in female, it stimulates development and maturation of ovarian follicles to produce eggs.
In males, promote spermatogenesis

2. Luteinizing Hormone
Functions in female, stimulate ovulation, formation of corpus luteum,
secretion of Progesterone and estrogen
in male, it is known as intersticial cell stimulating Hormone ICSH induces secretion of testosterone
3. lactogenic hormone or Prolactin

function stimulates lactation, milk production after child birth.
4. Adrenocorticotropin Hormone

Function stimulaes adrenal cortex to secrete adrenocorticosteroid hormone
Hyposecretion atrophy of adrenal gland
Hypersecretion excessive growth of adrenal cortex

5. Thyrotropin or Thyroid Stimulating Hormone TSH

Function stimulate thyroid gland
Hyposecretion thyroid atrophy
Hypersecretion stimulate thyroid gland to produce excessive thyroxine

6. Growth Stimulating Hormone GSH or Somatotropin
Function controls growth of body
Hyposcretion cause dwarfism in childhood
Myxoedema in adult reduce genital organ, reduce fertility

7. Melanocyte Stimulating Hormone MSH

Functions stimulate pigmentation of skin, secreted by intermediate lobe


Neurohypophysis

It stores and releases 2 hormones

1. Oxytocin (Pitocin) it affects uterine contraction during child birth in females

2. Vasopressin or Antidiuretic hormone ADH it increases BP it regulates reabsorption of water, hyposecretion large urine volume (diuresis) hypersecretion small urine volume (antidiuresis)

Thyroid gland

It is another important endocrine gland. It is found on either side of the trachea. There are two lobes which are joined by connective tissue called isthmus.

Structure - it is bilobed gland. It is about 5x3 cm in size. It weighs about 25 to 40 grams. Each lobe consists of follicles. The follicles secrete hormones. The hormones are:
o Thyroxine -- iodine is the major component of thyroxine.
o Thyrocalcitone -- it regulate the Calcium level in blood.

Thyroid gland produces hormone when it gets activated by thyroid stimulating hormone TSH from anterior lobe of pituitary gland.

Role of thyroxine hormone
o Regulate metabolic activities
1. general metabolism
2. growth and differentiation
3. metamorphosis
Less secretion or thyroidectomy(removal of thyroid gland) causes following
o cretinism -- in childhood, retard growth mentally and physically
o myxoedema – in adulthood, lowering of basal metabolism, sluggish appearance, dry, pale skin low temp. etc.
o simple goiter - due to deficiency of iodine leads to enlargement of thyroid gland, swelling of neck called simple goiter.
Hyperthyroidism
o Increased metabolic rate
o Exopthalmic goiter or Grave’s disease
o Bulging of eye ball
o Irregular heart beat
o Nervousness
o Loss of weight etc

Thyrocalcitonin
It is hypocalcemic, hypophosphatemic and secreted when Ca++

Parathyroid gland

It is found embedded in dorsal surface of thyroid gland. There are lobes two on each thyroid gland. These are rounded masses. Each is about 2 to 4 mm in size and 50 mg in weight . there are masses of polygonal cells called chief cells. These cells secrete parathormone or collip’s hormone. Low concentration of blood Calcium causes secretion of Parathormone.

Function
It increases Calcium level mobilizing from bone and reducing its elimination in urine, decreases phosphate level eliminating in urine, and affects growth of bones, membrane permeability, nerve functioning and muscular activity. The production of this hormone is controlled by concentration of Calcium level in blood. Excess Calcium inhibits its production.

Disorder
Low level of Parathormone leads muscle spasms, sustained contraction or tetany of muscle in larynx, face, hand and feet. Abnormally low levels may lead of death. High level of Parathormone causes excess Calcium in blood. As Calcium is taken from bone, bone becomes soft and porous. Decalcification is called Osteoporosis.



Adrenal glands

There are two small yellowish glands found at anterior tip o kidney. They are conical and have two distinct regions. The outer region is called cortex and inner region is called medulla.

Hormones of adrenal cortex

Cortex region secretes over 50 different hormones. They can be catagorised into three types.
• Mineralocorticoids
Functions
- regulate water
- Na + ,K+ metabolism
- Prevent loss of Na +
- Eliminate K+
- Increase water reabsorption
- Eg Aldosterone

• Glucocorticoids
Functions
- conversion of aminoacid, fatty acid into glucose called gluconeogenesis
- increase blood sugar level
- eg cortisol

• Sex corticoids
Fuctions
- have same functions as sex hormones
- promote secondary sex characters

Hyposecretion of adrenal cortex causes Addition’s disease
Symptoms
- muscular weakness
- ready fatigability
- loss of weight, dehydration
- hypotension
- anorexia( loss of appetite)
- vomiting, diarrhea
- mental confusion
- hypoglycemia
- decreased ability to withstand infection
- haemorrhage


Hypersecretion of adrenal cortex causes Cushing’s syndrome. It is mainly due to excess Glucocorticoids.
Symptoms
- protein depletion
- poor wound healing
- poor muscle development
- thin skin and red cheeks
- moon face fat pad, buffalo hump
- pendulous abdomen

Adrenal virilism it is due to disorder of secretion of adrenal cortex
symptoms
- produces masculine type like beards, moustache, male voice in female
- uterus and ovaries degenerate, menstruation stops

Hormones of adrenal medulla

Adrenaline or epinephrine
Functions
- prepares body for emergency or at the time of fight
- dilation of pupil
- Diversion of blood supply to organs
- Strenuous work of organs
- Decreased gastro intestinal activity
- Bronchodilation

Nor adrenaline or nor epinephrine
Functions
- increase BP by vasoconstriction
- CNS stimulation
- Heat production
- Decrease cardiac out put
- Powerful exciter
- Tonus hormone


Pancrease

It is heterocrine gland having both the exocrine and endocrine part in one. It is situated at the C shaped curve of duodenum. The endocrine part is found towards the tail of Pancreas. It consists of some specialized cells. The alpha cells produce Glucagon, Beta cells produce Insulin and delta cells produce Somatostatin.

Functions of Glucagon
It converts glycogen into glucose when glucose level falls down in blood

Functions of Insulin
It converts excess glucose into glycogen for storage in the liver. The hyposecretion of insulin causes rise in the glucose level in the blood. It causes a disease called Diabetes mellitus(DM)
Symptoms - increased thirst due to increased urination usually at night.
- appearance of glucose in urine( glucosuria) when it rises to about 200
mg in 100 cc of blood
- loss of body weight
- poor wound healing specially in foot
- attacks vision
- causes heart diseases
somatostatin controls the secretion of both glucagon and insulin