Endocrine Flashcards
The Endocrine System
The endocrine system (endo-, inside, and krinein, -to secrete)
- comprises several glands (pituitary, thyroid, parathyroid, adrenals) and
- Scattered cells in the gonads, pancreas, intestine, and other organs
Primary function of endocrine cells
produce hormones
- the endocrine organs do not have ducts and so are called the “ductless” glands. Hormones are secreted into the blood or extra cellular spaces
Hormones that are released into the circulation act on distant organs (endocrine effect)
For example, pituitary hormones exert an endocrine effect on the thyroid, adrenals, or gonads
Four major endocrine glands:
: the pituitary, thyroid, parathyroid, and adrenals
The pituitary, thyroid, parathyroids, and adrenals are unrelated to each other and have distinct anatomic locations
gynaecomastia
men gets breasts
Pituitary
- located intracranially in an indentation of the base of the cranium called the sella turcica (a Latin term -Turkish saddle)
- consists of two parts (anterior and posterior), which are connected to the hypothalamus via a stalk that contains extensions of neurons and the vessels of the pituitary portal system
The blood vessels transport-from the hypothalamus into the pituitary
-the neuroendocrine releasing factors that regulate the function of the pituitary cells
highly vascular- lots of blood vessels
The Anterior Pituitary ( adenohypophysis )
consists of five distinct cell types, each of which is named according to the hormone it secretes. These hormones are:
growth hormone (GH) prolactin (PRL ) adrenocorticotropic hormone (ACTH) the gonadotropins (luteinizing hormone [LH] and follicle-stimulating hormone [FSH])- teste or ovary, testosterone- ova,estro and progesterone thyrotropic hormone (thyroid-stimulating hormone [TSH])
Growth Hormone (GH) action and target
Somatomedin Synthesis º Growth Simulation
targets liver and other
prolactin
action and target
lactation- targets breast
Thyroid Stimulating Hormone (TSH)
action: Thyroid Hormone Synthesis &
Release
targets thyroid
Follicle-Stimulating Hormone (FSH)
action -spermatogenesis, estrogen synthesis oogenesis
organ: testi
ovary
Adrenocorticotropic Hormone (ACTH)
action Glucocorticoid Synthesis & Release
target adrena cortex
Luteinizing Hormone (LH)
action:
Ovulation
Corpus Luteum, hence Progesterone Production
target ovary
action:
Testosterone Synthesis
target testi
Regulation!!
The secretion of hormones of the anterior pituitary is regulated by
positive stimulation -exerted by the cells in the hypothalamic centers and
negative feedback inhibition -created by the hormones produced by the target endocrine cells in the thyroid, adrenals, and gonads
The Posterior Pituitary (neurohypophysis)
which comes from anterior vs posterior
- release oxytocin (pitressin) and the antidiuretic hormone (ADH)
In contrast to the hormones of the anterior pituitary, which are trophic and stimulate the functions of other endocrine glands, the hormones of the posterior pituitary have no trophic functionsThese hormones act on nonendocrine cells; - oxytocin stimulates the contraction of the pregnant uterus and
- ADH promotes the reabsorption of water from the renal tubules
THE THYROID GLAND
weight : 15-25 g
• derived from primitive gut
• function: storage & release of thyroid hormones
• 2 “butterfly-shaped” lobes connected by narrow band of tissue called the isthmus
-ant to lower part larynx &. Above clavicle
an endocrine gland located in the neck
- consists of two types of cells: follicular cells and C cells
Follicular cells secrete thyroid hormones (thyroxine [T4] and triiodothyronine [T3])- essential for maintaining the intermediate metabolism.
The secretion of T3 and T4 is regulated by TSH
The C cells secrete calcitonin, a polypeptide - involved in the maintenance of calcium homeostasis
The secretion of calcitonin is influenced by the concentration of calcium in serum
Overview of Major Diseases
The most important diseases involving the endocrine glands present as:
- Hyperfunction
- Hypofunction
- Tumors
hypo
– low or deficient; Hyper- high or excessive
endocrine
- secretion into the circulation
exocrine
– secretion via duct into GI system
syndrome
– group of symptoms common to several diseases
disease
specific cause known
benign tumor
one that does not spread (metastasize)
hypertrophy
– grow in size due to constant stimulus
autonomous
– with no feedback control