Endocrine System: Anatomy and Physiology

What are three layers of the eyeball?

Fibrous

Vascular

Inner

What is the main artery supplying the eye?

Ophthalmic artery

What hormone does adipose tissue secrete and what is its function?

Leptin

Controls hunger and satiation

What hormone does the heart secrete and and what is its function?

Atrial natriuretic peptide

Decreases reabsorption of sodium and water in renal tubes

What are the six endocrine glands?

Pineal

Pituitary

Thyroid

Parathyroid

Thymus

Adrenal

What five organs have secondary endocrine functions?

Heart

Stomach

Pancreas

Ovaries

Testes

What tissue has an endocrine function?

Adipose tissue

What is an endocrine gland?

Collection of secretory cells surrounded by capillaries, allowing hormones to diffuse into the bloodstream

What two systems control homeostasis?

Autonomic nervous system

Endrocine system

What is the pineal gland and where is it found?

Small body attached to the roof of the third ventricle of the brain

What are the two types of cells in the pineal gland?

Pinealocytes: hormone secreting cells

Glial cells

What is the function of the pineal gland?

Secrets melatonin

What is the main function of melatonin?

Controls how and when we sleep

What three factors affect the secretion of melatonin?

Amount of daylight

Hour of the day

Number of daylight hours we get

What are four additional functions of melatonin?

Coordination of daily and circadian rhythm

Mood

Inducting sleepiness during darkness

Maturation of sex organs

What is the location of the pituitary gland?

Hypophyseal fossa of the sphenoid bone

Below the hypothalamus

Attaches by the infundibulum

What are the two main parts of the pituitary gland?

Anterior pituitary

Posterior pituitary

What is the structure of the anterior pituitary?

Upgrowth of hormone secreting glandular tissue from the pharynx

What is the structure of the posterior pituitary?

Downgrowth of nervous tissue from the brain

What is the pituitary stalk?

Network of nerve fibres connecting the posterior pituitary gland and the hypothalamus

What are the four functions of the growth hormones secreted by the anterior pituitary gland?

Growth and cell division

Protein synthesis

Fat breakdown

Increased blood glucose levels

When is growth hormone secretion the highest?

Childhood and adolescence

At night during deep sleep

Stimulated by hypoglycaemia, exercise and anxiety

What two hormones regulate the growth hormone?

Growth hormone releasing hormone

Growth hormone release inhibiting hormone

What hormone is suppressed by the growth hormone?

Thyroid stimulating hormone

What two hormones are secreted by the posterior pituitary?

Oxytocin

Antidiuretic hormone

What are the two functions of oxytocin?

Stimulates uterine smooth muscle for childbirth

Stimulates muscle cells for breast lactation

What is the location of the thyroid gland?

Anteriorly to the larynx and trachea

At the level of C5,6 and 7 and T1

What are the three main components of the thyroid gland?

Right lateral lobe

Left lateral lobe

Isthmus

What is the structure of the thyroid gland?

Follicles lined with cuboidal follicular cells

Parafollicular cells between follicles

How does the thryoid gland lower calcium blood levels?

Stimulates osteoblasts to store calcium in bones

Oppose parathyroid hormone which increases blood calcium

Where is the thyroid stimulating hormone secreted from?

Anterior pituitary

What is the function of the thyroid stimulating hormone?

Stimulates growth and activity of the thryroid gland

Secretes thyroxine and tri-iodothyronine

What are the two functions of the thyroid hormones?

Increase metabolic rate and heat production

Regulate carbohydrate, protein, and fat metabolism

How do thryoid hormones influence cells?

Enter nuclei to regulate gene expression

Enhance adrenaline and noradrenaline effects

What are the four parathyroid glands?

Right superior pituitary

Right inferior pituitary

Left superior pituitary

Left inferior pituitary

What is the structure of the parathyroid glands?

Enclosed by fine connective tissue capsule

Surrounded by sinusoid network

What hormone is secreted by the parathyroid glands?

Parathyroid hormone

What is the function of the parathyroid hormone?

Increases blood calcium levels by releasing calcium stored in bone

Stimulates osteoclasts which increase calcium reabsorption from renal tubules

What hormone does PTH act in a complementary manner to maintain normal blood calcium levels?

Calcitonin

What are pancreatic islets?

Clusters of cells scattered through the pancreatic gland where hormones are secreted into the blood

What are the main three cells of the pancreatic islets and what is their function?

Alpha cells secrete glucagon

Beta cells secrete insulin

Delta cells secretes somatostatin

What are the two actions of insulin?

Stimulates glucose uptake in cells

Promotes glycogenesis

What are the two actions stimulated by glucagon?

Glyocogenolysis

Gluoneogenesis

What is the role of somatostatin?

Inhibits insulin, glucagon and growth hormone

What is the location of the adrenal glands?

Upper pole of each kidney

What are the two parts of the adrenal glands?

Cortex

Medulla

What are the three steroid hormones produced by the adrenal cortex from cholesterol?

Glucocorticoids

Mineralocorticoids

Gonadocorticoids

What two hormones are secreted by the adrenal medulla?

Adrenaline

Noradrenaline

What is the main functions of the glucocorticoids?

Regulate metabolism, immune response and stress

What are the four effects of the glucocorticoids?

Glycogen breakdown and gluconeogenesis

Lipolysis

Protein breakdown

Mild sodium and water retention

What are the three effects of high glucocorticoid levels?

Anti inflammatory

Immunosuppressive

Delayed wound healing

What is the main function of the mineralocorticoids?

Maintains water and electrolyte balance

What are the two effects of the mineralocorticoids?

Sodium and potassium ion extention in kidneys

Water retention

Regulated by potassium ions and angiotensin

What is the Renin Angiotensin Aldosterone System?

What are the effects of adrenaline?

Increases heart rate and blood pressure

Increases metabolic rate

What are the effects of noradrenaline?

Vasodilation to vital organs