What are the Primary Endocrine Organs?
- Pituitary gland
- Pineal gland
- Thyroid gland
- Parathyroid glands
- Adrenal glands
What are the Functions of the Endocrine Organs?
- growth and development
- internal environment homeostasis
- energy production, storage, and utilization
- reproduction
Characteristics of Endocrine Organs
- epithelial in origin
- ductless
- highly vascular
- control of effect is mediated by hormones
What is Autocrine cell signalling?
a cell secretes a signal that can influence its own receptors
What is Paracrine cell signalling?
a cell can release a signal that influences the receptors of a neighbor cell
What is Endocrine cell signalling?
a cell releases a signal (hormone) that travels a long way to reach a distant target cell
What is the Hypothalamus and what does it do?
- a portion of the brain that links the nervous system to the endocrine system via the pituitary gland
- hypothalamic nuclei control distant cells via hormones
- secreted releasing hormones into the adenohypophysis
What is the Neurohypophysis?
- posterior pituitary
- neuroectodermal origin
- pars nervosa, infundibular stalk, eminentia mediana
- store ADH and oxytocin from the hypothalamus, then release them into the blood
What are Herring Bodies?
- swellings along the axons of the hypothalamus nuclei where hormones are stored
- in the infundibular stalk
- stores ADH and oxytocin
Which hypothalamic nucleus secretes ADH?
supraoptic nucleus
Which hypothalamic nucleus secretes oxytocin?
paraventricular nucleus
What is ADH?
- antidiuretic hormone
- targets the kidney
- will stimulate the cells to absorb sodium more efficiently, this increasing water resorption and concentration of urine
What is oxytocin?
- stimulates contraction of myoepothelial cells for milk letdown
- release is stimulated by baby animal suckling
What is the Adenohypophysis?
- anterior pituitary
- epithelial origin (roof of pharynx)
- pars distalis, pars intermedia, pars tuberalis
- releasing hormones from the hypothalamus stimulate the cells of the adenohypophysis to release other hormones
What are the acidophil cells of the Pars Distalis and what are the hormones they secrete?
- somatotropes: growth hormone (GH)
- mammotropes/lactotropes: prolactin
What are the basophil cells of the Pars Distalis and what are the hormones they secrete?
- thyrotropes: thyroid-stimulating hormone (TSH)/thyrotropin
- gonadotropes: follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
- corticotropes: adrenocorticotropin (ACTH)
What is the function of the Pineal gland?
- provide regular daily rhythms of bodily activity
- pinealocytes produce hormone melatonin
What is Melatonin and what is its function?
- hormone produced by pinealocytes
- mainly secreted at night
- an effective antioxidant
- involved in signaling the time of day and time of year
- has immune-enhancing and oncostatic properties
What are Parafollicular cells and what is their function?
- also known as clear cells, in the thyroid gland
- secrete calcitonin in response to high blood calcium
- main function to lower serum calcium
- decreases osteoclast activity so less bone turnover
- target bones and kidney
Describe the follicles of the thyroid gland
- small cuboidal cells form the follicle (flattened when less active)
- produce thyroglobulin
- stored in follicle lumen (colloid) until needed
- convert thyroglobulin to thyroxine
- regulated by TSH
Describe the Parathyroid gland
- composed of tightly packed chief cells which make the follicle full of colloid
- secrete parathormone (PTH) into capillaries
- PTH increases calcium
Adrenal Gland Cortex
- arises from mesoderm
- secretes corticosteroids
- Zona glomerulosa, Zona fasciculata, Zona reticularis
Adrenal Gland Medulla
- arises from neural crest
- secretes catecholamines
- chromaffin cells are making epinephrine and norepinephrine
Describe Zona Glomerulosa
- first layer of adrenal gland cortex
- cells secrete mineralocorticoids: aldosterone
