The endocrine system: Histo Flashcards
Define and compare – exocrine versus endocrine gland.
Exocrine → secrete onto a surface; either directly or through a duct.
Endocrine → secrete internally; ductless glands; secrete hormones; primarily utilize cardiovascular system for distribution.
List the exclusive endocrine glands within the human body. What other organs and tissues also contain hormone-secreting cells that are not exclusively classified as endocrine glands?
exclusive
- hypothalamus
- pituitary
- thyroid
- thymus
- adrenal
both
- testes
- pancreas
- ovaries
Describe the role of the hypothalamus and pituitary gland in the endocrine system. The hypothalamus is part of what two organ systems?
Role of hypothalamus:
- maintain homeostasis
- main visceral control center for body; the autonomic control center; regulates homeostatis and endocrine system functioning
- the pituitary gland is known as the “master gland for the endocrine system”;
- together the hypothalamus and the pituitary gland (hypophysis) regulate virtually all aspects of growth, development, metabolism, and homeostasis.
- Hypothalamus: major link between nervous and endocrine systems; considered the “command center for the endocrine system”; its secretions can regulate other glands
For the hypothalamus, describe and identify the gross anatomical and histological structures of each. Additionally, discuss the hormones produced and/or secreted by each, the cells that produce and/or secrete the hormone, and the principal actions of each hormone.
The hypothalamus produces
9 hormones
- 5 releasing hormones
- impact/control anterior pituitary
- GnRH
- CRH
- TRH
- PRH
- GHRH
- impact/control anterior pituitary
- 2 inhibiting hormones
- which impact/control the anterior pituitary; and
- PIH (dopamin)
- GHIH (somatostatin)
- which impact/control the anterior pituitary; and
- 2 other hormones
- released from the posterior pituitary
- ADH
- Oxytocin
- released from the posterior pituitary
For the pituitary gland describe and identify the gross anatomical and histological structures of each.
Has two significant parts:
- Anterior Pituitary/Anterior Lobe/Adenohypophysis
- Pars Distalis –
* bulk of anterior lobe
* cords of epithelial cells, capillaries; develops from anterior wall of Rathke’s pouch
- Pars Distalis –
- Pars Intermedia –
* thin remnant of posterior wall of Rathke’s pouch;
* surrounds a series of colloid-filled follicles that represent the residual lumen of Rathke’s pouch.
- Pars Intermedia –
- Pars Tuberalis –
* from thickened lateral walls of Rathke’s pouch;
* forms a collar or sheath around infundibulum;
* most cells here are basophilic gonadotropic cells.
- Pars Tuberalis –
- Posterior Pituitary/Posterior Lobe/Neurohypophysis
- Pars Nervosa –
* neurosecretory axons and their endings
- Pars Nervosa –
- Infundibulum –
* contains neurosecretory axons forming the hypothalamo-hypophyseal tracts
* derived in part from an outpocketing of the ectoderm lining the roof of the mouth called of the hypophyseal (Rathke’s) pouch and in part from an outpocketing of the neuroectoderm lining the floor of the hypothalamus called the neurohypophyseal bud
- Infundibulum –
For the pineal gland/body, describe and identify the gross anatomical and histological structures of each. Additionally, discuss the hormones produced and/or secreted by each, the cells that produce and/or secrete the hormone, and the principal actions of each hormone.
- Neuroendocrine gland
- Regulates daily body rhythm;
- day/night cycle (circadian rhythm)
Major hormone production: melatonin
Two cell types:
- Pinealocytes (parenchymal cells) – 95% of cells
- Interstitial (Glial) cells – 5% of cells Characteristic presence of corpora arenacea (brain sand)
For the adrenal glands describe and identify the gross anatomical and histological structures of each. Additionally, discuss the hormones produced and/or secreted by each, the cells that produce and/or secrete the hormone, and the principal actions of each hormone.
Capsule around the gland
Two parts within the adrenal glands:
- cortex
- large area; peripheral, just below capsule; makes up 80%-90% of the gland; steroid-secreting cells
- medulla
- smaller area; centrally located; catecholamine-secreting cells
__zones:
- zona glomerulosa: mineral corticoids,
- aldosterone
- zona fasciculata: glucocorticoids, cortisol
- zona reticularis: androgens, DHEA adrenal
- medulla: epinephrine and norepinephrine (NE) and dopamine
For the islets of Langerhans describe and identify the gross anatomical and histological structures of each. Additionally, discuss the hormones produced and/or secreted by each, the cells that produce and/or secrete the hormone, and the principal actions of each hormone.
- The endocrine portion is seen in the pancreas as the islets of Langerhans
- most numerous in the tail.
- Stain pale compared to exocrine portion (i.e. pancreatic acini).
The three principle cells of the islets of Langerhans:
- Beta or B Cells
- – 70% of Islet – synthesize and secrete insulin; cells found towards center of islet. lowers blood glucose
- Alpha or A Cells
- – 17% of Islet – synthesize and secrete glucagon; cells found towards periphery of islet raises blood glucose
- Delta or D Cells
- – 7% of Islet – synthesize and secrete somatostatin [identical to growth hormone-inhibiting hormone (GHIH) from hypothalamus];
- cells found towards the periphery of islet. Somatostatin – inhibits insulin and glucagon secretion
For the thyroid gland, describe and identify the gross anatomical and histological structures of each. Additionally, discuss the hormones produced and/or secreted by each, the cells that produce and/or secrete the hormone, and the principal actions of each hormone
- The walls of these thyroid follicles are made up by follicular cells
- (simple squamous to low columnar)
- produce of thyroid hormones.
- Thyroxine (a.k.a. Tetra-iodothyronine or T4) – four atoms of iodine
- Tri-iodothyronine (a.k.a. T3) – three atoms of iodine
- produce of thyroid hormones.
- (simple squamous to low columnar)
T3 and T4 are important for growth, cell differentiation, and control of basal metabolic rate and oxygen consumption of body cells.
For the parafollicular glands describe and identify the gross anatomical and histological structures of each. Additionally, discuss the hormones produced and/or secreted by each, the cells that produce and/or secrete the hormone, and the principal actions of each hormone
- Parafollicular cells (or C cells) are also found in the thyroid gland.
- larger than follicular cells and stain less intensely.
- Parafollicular cells responsible for the production of:
-
Calcitonin (CT)
- decreases the level of calcium
- responsible for inhibiting the action of osteoclasts
-
Calcitonin (CT)
Secretion Regulation of Calcitonin - negative feedback system controls secretion of calcitonin; high blood Ca2+ levels stimulate the secretion of CT, while low blood Ca2+ levels inhibit the secretion of CT.
What are the hormones produced in the pituitary gland
7 hormones of the anterior pituitary and the 5 chromophils that produce them:
- Human growth hormone (hGH)
- secreted by somatotrophs; acidophil.
- Thyroid-stimulating hormone (TSH)
- secreted by thyrotrophs; basophil.
- Follicle-stimulating hormone (FSH)
- secreted by gonadotrophs; basophil.
- Luteinizing hormone (LH)
- secreted by gonadotrophs; basophil.
- Prolactin (PRL)
- secreted by lactrotrophs; acidophil.
- Adrenocorticotrophic hormone (ACTH)
- secreted by corticotrophs; basophil.
- Melanocyte-stimulating hormone (MSH)
- secreted by corticotrophs; basophil.
role of posterior pituitary gland
Posterior Pituitary (a.k.a. Posterior Lobe or Neurohypophysis)
- does not synthesize hormones (i.e. no secretory cells here),
- stores and releases two hormones
- oxytocin (OT)
- labor and lactation
- antidiuretic hormone (ADH)
- vasopressin
- oxytocin (OT)
Parathyroid
The parathyroid glands have a surrounding capsule with septa that enter gland.
There are two types of cells located in the parathyroid glands:
- Chief cells
- produce parathyroid hormone (PTH)
- most numerous of cells; small cell; round, centrally located nucleus; pale-staining, slightly acidophilic cytoplasm
- Oxyphil cells
- larger cell; VERY acidophilic cytoplasm; more common in older individuals; unknown function
PTH increases the level of calcium in the blood as PTH stimulates osteoclasts additionally PTH acts on the kidneys to slow the rate of Ca2+ loss from the blood into the urine. Negative feedback system low Ca2+ simulates hight Ca2+ inhibits
