The Endocrine System

The The Endocrine SystemEndocrine System is the set of is the set of hormone secreting glands within the body.hormone secreting glands within the body.

An An Endocrine glandEndocrine gland is a ductless organ is a ductless organ and makes and secretes specific chemical and makes and secretes specific chemical messengers into the blood.messengers into the blood.

An An Exocrine glandExocrine gland secretes directly or by secretes directly or by a duct to the outside of the body e.g. a duct to the outside of the body e.g. sweat gland, salivary glandsweat gland, salivary gland

The pancreas is both an endocrine and The pancreas is both an endocrine and exocrine gland (Islets of Langerhans exocrine gland (Islets of Langerhans secrete insulin)secrete insulin)

A A HormoneHormone is a chemical messenger, is a chemical messenger, secreted by a endocrine gland into the secreted by a endocrine gland into the blood which alters the effect of a specific blood which alters the effect of a specific tissue.tissue.

Hormone Gland FunctionADH / Growth

HormonePituitary

Increases water re-absorption by the kidney / bone elongation

Thyroxine ThyroidRegulates Metabolism, growth

and development

Adrenalin AdrenalsRaises heart rate, breathing

rate, blood pressure and blood glucose levels

Insulin Pancreas Uptake of glucose from blood.

Oestrogen OvariesEndometrium Formation, female

secondary sexual characteristics

Testosterone TestesSperm Production, male

secondary sexual characteristics

Melatonin PinealSleep Pattern, Ovulation, Sexual

Maturity

NS is fast acting, ES is slower (growth)

NS is electrical, ES is chemical.

NS has fast transmission, ES is slow

(blood)

NS is short lived response, ES is long

lasting.

NS affects local, ES has widespread affect.

The Pituitary gland is located in the hypothalamus (front of the brain) and is the most important part of the endocrine system.

The Pituitary gland has two parts, the anterior and posterior.

The Anterior part produces two hormones, ADH and Oxytocin.

ADH is involved in water level control in the blood. Oxytocin controls lactation (milk let down) and is

released from the pituitary when an animal is suckled.

The Posterior part of the Pituitary produces a number of important hormones.

These include FSH (Follicle Stimulating Hormone), LH (Luteinizing Hormone), Prolactin and Growth Hormones.

The Pituitary also releases hormones which control the Adrenal and Thyroid glands.

The thyroid glands are found on the trachea.

The main hormone produced is called thyroxine.

This hormone controls the growth and development of animals.

Iodine is required for its production. Lack of thyroxine causes deformation and

retardation. The glands swell if not enough hormone is

produced – this is called goitre in humans.

These are located on either side of the thyroid.

They produce two hormones: Parathormone and Calcitonin.

These hormones control the level of calcium, magnesium and phosphate in the body.

The Thymus A very small gland located on the neck.

Has some involvement in the production of lymphocytes (white blood cells), which are involved in immune response.

The Pancreas produces insulin. It is produced in the pancreas in the Islets of

Langerhans. Insulin is required for the intake of glucose in

cells and prevents the excess breakdown of glycogen.

If insulin is lacking, one outcome is the passing of glucose in the urine.

This is called diabetes mellitus. This can cause coma because the brain needs

glucose. Synthetic Insulin is now available for diabetics. It must be injected because if it was eaten it

would be digested.

The adrenal glands are found near the kidney. They produce over fifty different hormones

which are vital for life. Hydrocortisone is produced in the adrenal

glands and is required to control blood pressure and controls the loss of blood.

Adrenalin is secreted from the adrenal glands during stress.

It redirects blood to the head and increases the heartbeat.

It makes the individual more acute to their surroundings.

It is usually secreted when frightened. Another hormone called non-adrenalin, turns

off the effects of adrenalin.

The gonads are the sex glands - the testes and ovaries.

The hormones produced are involved in the reproductive systems of the animal.

These include testosterone, oestrogen and progesterone.

These hormones will be looked at in more detail in Animal Reproduction.