Flashcards in Endocrine Deck (33)
what are the main functions of the endocrine systems?
1) Maintain body homeostasis.
2)Help the body to react to stress in concert with the nervous system.
3)Regulate growth and development, including sexual development and reproduction
what are the main types of hormones?
1) Protein and glycoprotein hormones. Examples: Insulin, parathormone.
2) Small peptide hormones. Examples: vasopressin, oxytocin.
3)Hormones that are derivatives of amino acids. Examples: thyroxin, adrenalin
4)Steroids derived from cholesterol. Examples: testosterone, cortisol.
how does the endocrine system accomplish these functions?
the synthesis and secretion of hormones, chemical messengers that typically are released into the blood to act at specific distant receptors
what does the endocrine system consist of?
-major endocrine organs
-organs with a partial, but significant , endocrine role
-diffuse endocrine system: scattered cells within organs that fulfil an endocrine function
what is most of endocrine tissue origin?
what is the exception to endocrine tissue that is not epithelial origin?
adrenal medulla (basically a modified sympathetic ganglion, it is derived from the neural crest), hypothalamus (part of the brain), posterior pituitary (part of the brain)
Name 4 major endocrine glands.
what controls the pituitary gland?
why is the pituitary gland called the master gland?
its hormones regulate the activity of many other endocrine glands
why does the pituitary gland sit?
in the sella turcica of the sphenoid bone, and is just below the hypothalamus
what are the two lobes of the pituitary gland?
-anterior lobe or adenohypophysis
-posterior lobe or neurohypophysis
how does the posterior lobe/ neurohypophysis develop?
downward growth of the hypothalamus and stays attached to the hypothalamus by the pituitary stalk
how does the anterior lobe/adenohypophysis develop?
upward pocket of epithelium in the roof of the oral cavity called Rathke’s pouch
Describe the hypothalamic- hypophyseal portal system?
a system that delivers factors to the anterior pituitary at relatively high concentration as hormone secretion in the anterior lobe of the pituitary is itself controlled by hormones from the hypothalamus above
Describe the structure of the anterior pituitary.
consists of packed secretory cells interspersed with fenestrated endothelium-lined vascular sinuses. These vessels are the second capillary bed in the hypothalamic-hypophyseal portal system
how do the secretory cells in the anterior pituitary react to dyes?
-Acidophils: stain with acid dyes.
-Basophils: stain with basic dyes.
-Chromophobes: take up either stain only very weakly
what are acidophils and basophils collectively called?
Describe the structure of the posterior pituitary.
-consists of the axons of nerve cells in the supraoptic and paraventricular nuclei of the hypothalamus. These travel down the pituitary stalk and terminate near capillaries in the posterior pituitary
-Within the posterior pituitary there are special glial cells called pituicytes (P). Swellings in the axons, called Herring bodies (HB), represent aggregations of oxytocin or antidiuretic hormone (vasopressin).
what is the functional unit of the thyroid gland?
thyroid follicle, a spherical space lined by epithelial cells that are low cuboidal when inactive
what do the 2 main thyroid hormones do : T3 and T4?
regulate cell basal metabolism rate and heat production. They also have a role in development and growth
Describe thyroid C cells.
C cells or parafollicular cells are found adjacent to the follicular cells. They are within the basal lamina that surrounds the follicle, but are not in contact with the colloid. They are easy to see in sections stained for their secretory product: calcitonin. Calcitonin inhibits osteoclast activity and lowers blood calcium. C cells are derivatives of the neural crest - these cells invade the thyroid during embryological development
what produces parathyroid hormone :a polypeptide hormone that is necessary for life?
Usually 4 small oval glands on the posterior surface of the thyroid gland
How does parathormone increase serum calcium by?
-Stimulating release of calcium from bone
- Increasing renal calcium reabsporption
- Increasing calcium absorption from the gut
what are the 3 cell types in the parathyroid glands?
-principal of chief cells-secrete PTH
-oxyphils- larger eosinophilic cells
- occasional adipose cells
what are the two different embryological origins of the two parts of the adrenal gland?
-The adrenal cortex is formed of epithelial cells.
-The adrenal medulla is formed of neural crest cells (like the sympathetic ganglia and dorsal root ganglia). It is essentially a modified sympathetic ganglion where the postganglionic neurons have lost their axons and instead release their transmitter (adrenalin or noradrenalin) into the blood
what is the adrenal gland surrounded by?
a thick capsule with connective tissue trabeculae extending inward through the cortex
what are the 3 distinct layers or zones of the adrenal cortex?
From outer to inner:
What are the 3 types of cholesterol-based steroid hormones secreted by the adrenal cortex?
1) Mineralocorticoids - involved electrolyte and fluid homeostasis
2) Glucocorticoids - involved in metabolism
3) Sex hormones
what is the function of the adrenal medulla?
-reinforces the action of the sympathethic nervous system at times of stress
-contain granules of adrenaline and noradrenaline that are released into the blood in response to sympathetic stimulation. This prepares the body for the ‘fight or flight’ response, increasing heart rate, raising blood pressure, causing bronchodilation