The Endocrine Glands Flashcards
What are the functions of the endocrine system?
Maintain body homeostasis
Help the body to react to stress in association with the nervous system
Regulate growth and development, including sexual development and reproduction
What are protein and glycoprotein hormones?
Insulin and parathyroid hormone
What are small peptide hormones?
Vasopressin and Oxytocin
What are steroids derived from cholesterol?
Testosterone and Cortisol
What are the major endocrine organs?
Thyroid and Adrenal glands
What are organs with partial endocrine roles?
Pancreas, ovary and testes
What are diffused endocrine systems?
Scattered cells within organs that fulfil an endocrine function
Where does the pituitary gland sit?
In the sella tunica of the sphenoid bone below the hypothalamus
What is the pituitary gland also know as?
Hypophysis
How many lobes does the pituitary gland have?
2 (anterior and posterior)
What is the anterior lobe of the pituitary gland called?
Adenohypophysis
What is the posterior lobe of the pituitary gland called?
Neurohypophysis
Describe the Neurohypophysis?
Develops as a downward growth of the hypothalamus and stays attached via the pituitary stalk
Describe the Adenohypophysis?
Develops as an upward pocket of epithelium in the roof go the oral cavity called Rathke’s pouch
What are hypothalamus hormones that regulate the adenohypophysis?
Growth hormone (GHRH) Somatostatin Thyrotropin-releasing hormone (TRH) Corticotropin-releasing hormone (CRH) Dopamine Gonadotropin-releasing hormone (GnRH)
What cells are within the Anterior pituitary?
Secretory cells
What are acidophils and basophils called?
Chromophils
What are Somatotrophs and lactotrophs?
Acidophils
What are tyrotrophs, corticotrophins and gonadotrophs?
Basophils
What does the posterior pituitary consist of?
Axons of nerve cells in the supraoptic and paraventricular nuclei of the hypothalamus
Where do the nerve cells terminate in the posterior pituitary?
Near capillaries
What are glial cells known as?
Pituicytes
What is the functional unit of the thyroid gland?
Thyroid follicle
What does the follicle contain in the thyroid gland?
Colloid
What is within the colloid in the thyroid follicle?
Iodothyroglobulin
What are the main thyroid hormones?
Triiodothyronine and tetraiodothyronine
Where are C cells found?
Adjacent to the follicular cells, within the basal lamina that surround the follicles
Are the C-cells in contact with the colloid?
No
What do the C-cells secrete?
Calcitonin
What is the function of Calcitonin?
Inhibits osteoclast activity and lowers blood calcium levels
When do the C-cells invade the thyroid?
During embryological development
What are parathyroid glands?
Usually 4 small oval glands on the posterior surface of the thyroid gland.
What do the parathyroid glands secrete?
Parathyroid hormone
How does parathyroid hormone increase serum calcium?
Stimulating release of calcium from bone
Increasing renal calcium reabsorption
Increasing calcium absorption form the gut
What are the three main cell types in the parathyroid gland?
Chief cells, oxyphils and adipose cells
What are chief cells?
They are small, lightly stained cells with dark, central nuclei
What are oxyphils?
Larger eosinophilic cells that appear at puberty and become more numerous with age and have lots of mitochondria
What is the adrenal cortex formed from?
Epithelial cells
What is the arrangement of the adrenal glands?
Surrounded by a thick capsule with connective tissue trabeculae extending inward through the cortex
What are the distinct layers in the adrenal cortex?
Zona glomerulosa, Zona fasciculata and Zona reticularis
What are the three types of cholesterol based steroid hormones the adrenal cortex secretes?
Mineralcorticoids
Glucocorticoids
Sex hormones
What are the Mineralcorticoids involved in?
Electrolyte and fluid homeostasis
Where are the Mineralcorticoids produced?
In the outer layer of the adrenal cortex
What are glucocorticoids involved in?
Aspects of metabolism
Where are glucocorticoids produced?
In the middle layer of the adrenal cortex
What is the principle glucocorticoid produced?
Cortisol
What can control Cortisol secretion?
ACTH
What is the function of the adrenal medulla?
Reinforces the action of the sympathetic nervous system at times of stress
What are the cells like with the adrenal medulla?
Slightly basophilc and arranged in cords and nests
What type of gland is the pancreas?
Endocrine and Exocrine
What is present in the endocrine pancreas?
Islets of langerhans
What are the three principle cell types within the pancreatic islets?
Insulin secreting cells
Glucagon secreting cells
Somatostatin secreting cells
What do the testes produce?
Spermatozoa and testosterone
What do the ovaries produce?
Ova, Oestrogen and Progesterone
What surrounds the Ovarian follicle?
Theca interna
What are amino acid derivative hormones?
Thyroxin and adrenalin
What is a swelling in the axon of the posterior pituitary called?
Herring body
How are the hormones from the hypothalamus delivered to the anterior pituitary?
In high concentration through the hypothalamic-hypophyseal portal system
What are the cells of the anterior pituitary?
Acidophils and Basophils = Chromophils
What is the portion of the pituitary between the anterior and posterior lobes?
Pars intermedia
What is the pars intermedia?
The remnants of the lumen of Rathke pouch
What is contained within the pars intermedia?
Follicles that contain a colloid
What are C cels derived from?
Neural crests
What surrounds the parathyroid gland?
Connective tissue capsule
What forms the adrenal medulla?
Neural crest cells
What is the main mineralocorticoid?
Aldosterone
Function of Aldosterone?
Promotes sodium retention in the distal convoluted tubule of the kidney
What type of hormone is secreted by the zona granulose?
Mineralcorticoids
What type of hormone is secreted by the zona fascicular?
Glucocorticoids
What type of hormone is secreted by the zona reticularus?
Sex hormones
Function of insulin secreting cells?
Lowering of blood glucose
Function of glucagon secreting cells?
Elevation of blood glucose
Function of somatostatin secreting cells?
Inhibit insulin and glucagon secretion
What is an antibody?
An identifiable marker on or in a specific cell