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Terms in this set (75)
What is endocrinology?
The study of intercellular communication
What are the different types of signicalling
Type of cell signalling where hormone leaves cell and reacts with same cell
Type of cell signalling where a factor is bound to cell and reacts with receptors on another cell next to it
Type of cell signalling where a cell produces a factor and releases it in the local environment and the cells around it have receptors that react with the factor
Type of cell signalling where factors are produced and released in the blood and travels to receptors in the body.
Type of cell signalling that is a gland WITH a duct (all the other types of signalling are DUCTLESS)
What are some facts about the Pituatary gland?
AKA the Master endocrine gland -
- Combines neural structures with Endocrine glands
- Suspended from hypothalamus by pituitary stalk
- Secretes eight hormones
Where is the Pituatary gland (Hypophysis) located?
Located in the Sella Turcica, a cavity with the Sphenoid Bone
What are the 3 parts of the anterior pituitary
AKA Adenohypophysis: Made of endocrine tissue so stains darker compared to Posterior Pituitary
Pars Anterior (Anterior Pituitary)
Pars Intermedia: Between Anterior and Tuberalis
Pars Tuberalis : Section that wraps around stalk (not attached to brain)
What are the 2 parts of the posterior pituitary
AKA Neurohypophysis : Made of neuro tissue so has a lighter stain compared to anterior pituitary
Infundibulum: Stem that attaches it to brain
THe Pituitary forms what what 2 types of tissue
Neural and Oral
What parts of the Pituitary form from the neural component
The posterior pituatary
Starts off as the Diencephalon
Neurohypophysis and Infundibulum
What parts of the Pituitary form from the oral component
The anterior pituitary
Starts off as the Rathke's Pouch
Adenohypophysis (Pars Distalis, Pars Intermedia, and Pars Tuberalis)
How many stages are involved in the Anterior pituatary?
1) Hypothalamic Nuclei within the brain that releases a signal that stimulates the Anterior pituitary
2) AP release hormones into bloodstream
How many stages are involved in the Posterior pituatary?
Hypothalmic nuclei from the brain go all the way down to Posterior Pituitary and activate it to release hormones into blood.
What are the 3 different types of secretion and their differences
Primary: Releasing hormones from hypothalamus to affect other cells (portal system)
Secondary: Direct Effects of the hormones themselves (autoregulation) (If there is alot already less will be released and vice versa
Tertiary: Hormones are produced which stimulate cells to produce other hormones which go on to effect other cells.
What are 2 important cells within the anterior pituitary
Important cells apart of the anterior pituitary. Stains lightly because they dont produce hormones
Important cells apart of the anterior pituitary that are stained cuz they carry hormones. Some are stained basophilic while esonophils are stained by Acidophils
Basophilic cells that are Chromophils found in the anterior pituitary. Secretes Follicle Stimulating Hormone (FSH) and Secretes Luteinizing Hormone (LH)
What does FSH do?
Controls Follicular Development in Ovaries and Gametogenesis in Testis
What does LH do?
Causes Luteinization of Ovary and helps Leydig cell function in Testis
Basophilic cells that are Chromophils found in the anterior pituitary. Secretes Thyrotropin - TSH
What does TSH (Thyrotropin) do?
Stimulation of Thyroid Gland which helos with Iodide uptake, Thyroglobin Synthesis, Thyroxine and Triiodothyroine release
Basophilic cells that are Chromophils found in the anterior pituitary. Secretes Adrenocorticotropin (ACTH)
What does Adrenocorticotropin (ACTH) do?
Stimulation of Adrenal Gland resulting in Increase Steroidogenesis (Mineralo- and glucocorticoids, androgenic steroids)
Basophilic cells that are Chromophils found in the anterior pituitary. Are thought to be similar to Corticotroph cells. Secretes α- melanocyte-stimulating hormone (α - MSH)
What does α- melanocyte-stimulating hormone (α - MSH) do?
Stimulation production of melanin in melonocytes in the skin resulting in Skin Darkening
What are the 4 types of basophil cells that are Chromophils?
What are the 2 types of Acidophils cells that are Chromophils?
Acidophils cells that are Chromophils found in the anterior pituitary. Secretes Growth Hormone (GH)
What is the function of Growth Hormone (GH)
Stimulation of Growth:
Muscle and Bone
All Internal Organs
Cell proliferation and protein synthesis
Acidophils cells that are Chromophils found in the anterior pituitary. Secretes Prolactin (PRL)
What does Prolactin (PRL) do?
Controls the Initiation and Maintenance of Lactation
What are some examples of Hypothalamic Releasing Hormones the anterior pituitary may be stimulated by?
Growth Hormone releasing hormone (GHRH)
Gonadotropin-releasing hormone (GnRH)
Corticotropin Releasing Hormone (CRH)
Thyrotropin-releasing hormone (TRH)
Plus some inhibiting hormones, e.g.:
Somatostatin (growth hormone-inhibiting hormone, GHIH)
What is the blood supply for the pitiuitary gland
A Hypophyseal Portal System which is derived from internal carotid artery: Has 2 branches:
Superior hypophyseal arteries:
Supplies Pituitary stalk and median eminence
Second capillary plexus in adenohypophysis -
Inferior hypophyseal arteries:
Supply neurohypophysis and Pituitary stalk
Second Capillary plexus in adenohypophysis
How is Adenohypophysis Secretion regulated
There are portal system that run from the brain to the anterior pituitary through long portal vessels. There are capilary beds in the posterior pituitary that connects to the anterior with short portal vessels. They all travel through the anterior pituitary before going through blood system
What 2 structures are associated with the Neurohypophysis (posterior pituitary)? What are the main characteristics? Main function?
Contains Unmyelinated axons (~100K) that come from Supraoptic (SON)and Paraventricular nuclei (PVN) of the brain
Their main function is to produce a Hormonal release which is triggered by neuronal impulse
What 2 types of cells can you find in the Neurohypophysis
Pituicytes and Herring Bodies
A type of cell that can be found in the Neurohypophysis. It is a Membrane Bound Neurosecretory Granules that is filled with hormone waiting to be released.
A type of cell that can be found in the Neurohypophysis. It is a highly branched glial cells
that help keep the tissue alive
What 2 hormones are released from Posterior Pituitary
Anti Diuretic Hormone (ADH) (Arginine Vasopressin)
Where is Anti Diuretic Hormone (ADH) (Arginine Vasopressin) produced? What does it do?
In the Supraoptic Nucleus of the Posterior Pituitary:
- Increases reabsorption of H2O at the collecting tubules
- Concentrates Urine
Where is Oxytocin produced? What does it do?
In the Paraventricular Nucleus of the Posterior Pituitary:
- Milk ejection reflex in response to nursing, distention of the vagina or cervix
- Stimulates Prolactin release from adenohypphysis (via short portal system)
What are the 2 main parts of the Adrenal Glands? WHere are they located
Located on top of the kidneys they consist of a
- Cortex - epithelial origin
- Medulla - neural crest
Describe the blood supply/drainage of the adrenal glands
Starts out from the outside at the Capsule arteries
and drains to th eCortical Arteries and finally the Medullary Arteries.
All drain through the gland into Suprarenal vein
(blood drains from outside gland towards inside)
What are the 3 main layers of the adrenal cortex
Zona Glomerulosa? Function?
The 1st layer of the adrenal cortex. It has Columnar or Pyramidal Cells and is Largely responsible for cell proliferation. Contains more "rounder" cells
Main function: Secretion of Mineralocorticoids (aldosterone) which help Regulation of blood pressure and blood volume
Zona Fasciculata? Function
The 2nd layer of the adrenal cortex. Contains Polyhedral Cells Called Spongiocytes that are Organized in one or two cell thick cords (cord like cells)
Main function: Secretion of Glucocorticoids (Cortisol)
which help with Carbohydrate Metabolism, Suppress immune response, and In connective tissues, decrease synthesis and promote protein and lipid degradation (helps in the tear down and build up of muscle)
Zona reticularis? Function?
The last layer of the adrenal cortex. Contains Irregularly shaped smaller cells that are Organized in irregular cords, forming an anastomozing network
Function: Secretion of Androgens (Dehydroepiandrosterone - DHEA, DHEAS) and, possibly, Glucocorticoids
- Only sex steroid secreted in significant quantities by adrenal cortex
- Possible role in immunity and stress response
- Can be converted into testosterone
How are adrenal hormone secretions regulated?
Through a Negative Feedback Loop: ie.
1) Corticotrophin-releasing hormone released from the hypothalamus
2) Adrenocorticotropic hormone (ACTH) released from the Adenohypophysis (anterior pituitary)
3) ACTH and CRH secretion are inhibited by serum concentrations of glucocorticoid released by adrenal cortex (more in the blood signal hypothalamus and AP to stop making hormones)
What hormones are created by the medula of the adrenal gland
Epinephrine (80%) smaller with fewer secretory granules
Norepinephrine (20%) larger with more secretory granules
*The Release of these hormones are activated by preganglionic sympathetic neurons and glucocorticoids
What are Chromaffin Cells?
A type of cell that you would find in the Medulla of the adrenal gland. They
- Arise from Neural Crest Cells
- They are Modified sympathetic post-ganglionic neurons without axons and dendrites
What are Islets of Langerhans? General characteristics?
Cells that are found in the Endocrine Pancreas.
- Lightly stained polygonal cells that are arranged in cords and separated by capillaries.
- Clustered (100-200 um in diameter) up to 1 million islets/pancreas
- More abundant in the tail of pancreas
What are the 2 different cells found in the Islets of Lnagerhans? How do they differ?
A cells: Are acidophils and produce glucagon
B cells: Are Basophils and produce insulin
They are regulated by Glucose concentration and sympathetic fibers
What is the function of Glucagon? Where does it come from?
To Increase blood glucose. Comes from A cells in the Islets of Langerhands in the Pancreas
What is the function of Insulin ? Where does it come from?
To Decrease blood glucose. Comes from B cells in the Islets of Langerhands in the Pancreas
What are some general characteristics of the Thyroid gland
- Two lobes and isthmus
- Originates from endoderm
- Highly vascularized
- Contains about 20-30 million Follicles that each have a
Colloid (Middle of follicle containing central cavity) Follicles vary in diameter
Describe the epithelium of Thyroid cells. What is the function of Thyroid cells.
Called Follicular Epithelium and consists of Simple squamous to columnar epithelium that have receptors for TSH.
Function: to produce, Storage, Activation, and Secretion of Thyroid hormone.
Parafollicular Cells (C cells)? Characteristics and Function?
Cells found in the Thyroid. They are Larger cells that can either be a part of follicular epithelium or isolated clusters. They also have Reduced Staining.
Function: releases Calcitonin?
What does Calcitonin do?
Lowers blood calcium levels by inhibiting bone reasporption. This is triggered by an increase in blood calcium levels.
What are the 2 types of thyroid hormone that are secreted? What are their functions? Where are they stored?
Thyroxine (T4) (number refers to # of iodine attached)
- Cell differentiation
- Control of oxygen consumption
- Basal metabolic rate
- Metabolism of proteins, lipids and carbohydrates
Stored in the Extracellular Colloid as Thyroglobulin. Can store up 2 a 3 months supply
How is thyroid hormone synthesized?
1) Synthesis of Thyroglobulin
2) Release of Thryoglobulin into follicle
3) Uptake of circulating iodide
4) Intracellular oxidation of Iodide
5) Transport of Iodide into follicle
6) Iodination of tyrosines in thyroglobulin (combine)
7) Reuptake and digestion of thyroglobulin within cell, releasing T3 and T4
How is the thyroid gland regulated
Through a Negative Feedback Loop (similar to adrenal gland)
The Thyroid produces T3 and T4 which interact with its target tissues as well as the Anterior Pituitary and hypothalumus which tells them to stop producing TSH and TRH respectively which stops they thyroid gland from releasing hormones.
TSH secretion from the anterior pituitary to the thyroid gland is increased/decreased/inhibitied by..
TSH Secretion Stimulates what?
Increased by cold
Decreased by heat and stress
Inhibited by Thyroid Hormones
TSH Secretion Stimulates:
- Production and release of T3 and T4
- Follicular cell uptake of colloid
- Hydrolysis of thyroglobulin
What are general characteristic of Parathyroid gland
- 4 small glands , located behind the thyroid gland
- Derived from pharyngeal pouches (Superior 2 from fourth pouch; Inferior 2 from third pouch)
- Contained within connective tissue capsule
What are the 2 main cells found in the Parathyroid glands
Cells that are apart of the Parathyroid glands. They are Parathyroid Hormone Secreting cells. They are Small polygonal with a vesicular nucleus; Pale staining - slightly acidophilic and have Irregularly shaped granules
Cells that are apart of the Parathyroid glands. They are a Smaller population compared to chief cells but are Larger polygonal cells. Acidophilic mitochondria
What is the main function of Parathyroid hormone?
Increase serum Ca+ concentration in the blood. Does so in different ways
How does Parathyroid hormone effect the bone to increase Ca+ levels. What 2 proteins are involved?
Parathyroid hormone stimulates bone absorption which will release calcium.
Increases RANKL expression:
- Osteoblasts (make bone) has a cell surface protein called RANKL (RANK Ligand) which binds with a receptor on Osteoclasts (reaborb bone) called RANK. When they bind together they from mature osteoclasts which help to increase reabsorbtion of bone
Decrease OPG expression:
OPG is a protein similar to RANK that is free and binds to RANKL sitting on osteoblasts. By decreasing them this frees up more to bind with Osteoclasts so that they can mature and bone reasborbtion can increase.
How does Parathyroid hormone effect the kidney to increase Ca+ levels
In the Kidney Parathyroid hormone increases Ca+ reabsorption and decreases Phosphate reabsorption (Phosphate and calcium come together to form bone but with less Phosphate less bone will be made and more calcium will be in the body) . It also increases Phosphate excretion and increase Vit. D which stimulates calcium absorption in the gut.
How does Parathyroid hormone effect the gut to increase Ca+ levels
Increases Ca+ reabsorption in the gut which is stimulated by Vitamin D.
In summary how does the Parathyrod hormone help increase Ca+
It increases the reabsorption (breakdown) of bone and releasing the calcium, stops the kidneys from getting rid of calcium while getting rid of phosphate so that there can be more calcium (Calcium and phosphate together make bone), and in the gut calcium absorption is increased.
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