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135 Cards in this Set

  • Front
  • Back
4 Mechanisms by which cells communicate with each other:
-Direct contact
How can cells directly contact each other and communicate?
Through gap junctions which can exchange small molecules
What does the Adenohypophysis develop from?
An ectodermal upgrowth from the roof of the primitive mouth cavity.
What is the upgrowth called?
Rathke's pouch
What do cells of the anterior wall of Rathke's pouch proliferate to form?
Pars distalis
Pars tuberalis (around the infundibulum)
What do the cells of Rathke's pouch that proliferate less extensively form?
Pars intermedia
What are the colloid-filled cysts that remain in pars intermedia?
Remnants of rathke's pouch
What are the 3 components that make up the Neurohypophysis?
-Pars nervosa
-Infundibular stalk
-Median eminence
What does the median eminence contain?
Neurosecretory cells extending from the hypothalamus into the posterior pituitary.
What are the support cells in the pars nervosa that support the axons from the neurosecretory cells?
Where are the cell bodies of the neurosecretory cells that extend axons into the pars nervosa?
In the Paraventricular and Supraoptic nuclei in the hypothalamus.
What happens when the cell bodies in the PVN and SO nuclei are stimulated physiologically?
They secrete hormones into the pars nervosa.
How do neurosecretory cells in the posterior hypothalamus cause secretion in the adenohypophysis?
By secreting releasing factors into a primary capillary plexus
What happens when releasing hormones stimulate the adenohypophysis?
It releases its trophic hormones into another capillary plexus to go via the blood to target tissues.
Are the islets of langerhans and parathyroid glands under pituitary control?
No; just controlled via metabolism changes and calcium.
What are the 5 cell types in the Adenohyphysis?
1. Somatotrophs
2. Lactotrophs
3. Corticotrophs
4. Gonadotrophs
5. Thyrotrophs
What percent of the adenohypophyseal cell population are somatotrophs?
What do somatotrophs secrete?
Growth hormone
What stimulates GH release?
What inhibits GH release?
What are the effects of GH on
-Somatic cells
-Chondrocytes and myoblasts
Fat: increased lipolysis
Liver: IGF1 secretion
Somatic cells: protein synthesis
via IGF1
Cartilage: mitosis via IGF1
What does GH hyposecretion lead to in children? What is the common cause of it?
-Short stature
-Lack of GRH
What does GH hypersecretion lead to in children? Adults?
Kids - gigantism
Adults - acromegaly
What are 2 other names for Lactotrophs?
What % of the adenohypophyseal cells are Lactotrophs?
What do lactotrophs secrete?
What stimulates and inhibits Prolactin secretion?
-Suckling/pregnancy stimulates
-Dopamine inhibits
What can also stimulate Prolactin secretion?
What is the most common pituitary tumor?
What does Prolactinoma lead to?
-Gonadal dysfunction
Why are Corticotrophs basophilic?
Because they're glycosylated
What % of adenohypophyseal cells are Corticotrophs?
What do corticotrophs secrete?
What does ACTH hyposecretion cause?
Secondary adrenal insuffiency
What is a common cause of secondary adrenal insufficiency?
Withdrawal of a patient from prolonged cortisone or prednisone therapy.
What is Cushing's disease characterized by?
ACTH hypersecretion
What are the 4 main symptoms of Cushing's?
-Truncal obesity
-Moon facies
-Gonadal dysfunction
What do gonadotrophs secrete?
Both LH and FSH
What can cause impaired LH/FSH secretion in women?
-Athletic training
What can an X-linked disorder causing defective GnRH secretion in males lead to?
-Eunuchoid appearance
-Tall stature due to testosterone deficiency and failure of epiphyseal plates to close
What is the smallest percent of the adenohypophyseal cells?
What does krippendorf say inhibits TSH secretion?
What does hypothyroidism lead to in infants? Adults?
Infants = cretinism
Adults = myxedema (hashimotos)
What does increased TSH in hypothyroidism lead to?
What does Hyperthyroidism lead to?
What are the secretory products of the neurohypophysis?
What is the type of neuron that secretes Oxytocin/ADH?
Is oxytocin only secreted by the posterior pit?
No it's also secreted by uterus, placenta, testis, epididymus, etc.
What stimulates Oxytocin secretion?
What 3 cells does oxytocin affect?
-Uterine smooth muscle cells
-Myoepithelial cells
-Prostate gland
What does oxytocin do to uterine smooth muscle and myoepithelial cells in the lactiferous ducts?
Contracts them
What does oxytocin do to the prostate?
Causes expulsion of prostatic secretions at ejaculation
What is ADH secretion regulated by?
Osmoreceptors in regions of the hypothalamus that do not have a bloodbrain barrier.
When is ADH secretion increased?
Increased in nausea
Decreased in alcohol consumption
What 2 cells does ADH act on?
-Nephron collecting duct epithelium
-Vascular smooth muscle
What patients have ADH hyposecretion (central)?
Diabetes inspidus patients
What do patients with Diabetes insipidus urinate?
Insipid amounts of dilute pee
What do patients with ADH hypersecretion (siADH) urinate?
Concentrate urine
What does the thyroid gland develop from?
A downgrowth of endoderm lining the floor of the pharynx
What is the site of origin of the thyroid indicated by?
Foramen cecum
What extends from foramen cecum to the target final site of the thyroid?
Thyroglossal duct
What does the adult thyroid consist of?
2 lobules + an Isthmus
What are the parafollicular cells of the thyroid formed from?
Neural crest
What divides the thyroid into lobules?
A thin connective tissue capsule which makes septations in it.
What do thyroid lobules consist of?
Several thyroid follicles
What is a thyroid follicle composed of?
-Simple layer of epithelial cells
-Colloid filled space
What type of epithelial cells are follicular cells?
They range from squamous when inactive to columnar when active.
What is colloid?
The extracellularly stored secretion of follicular cells
What does colloid consist of?
Mostly thyroglobulin
Are there many parafollicular cells?
No only a few
Do parafollicular cells contact colloid?
What do parafollicular cells look like compared to follicular cells?
What do parafollicular cells secrete?
What does calcitonin do?
Inhibits bone resorption by osteoclasts to reduce blood calcium levels.
Which side of a follicular cell of a thyroid follicle is apical?
The colloid side is apical
The outside is basal
How are follicular cells linked? At what side?
-Via junctional complexes
-At the apical side
What does TSH do when it binds its receptor?
Stimulates Thyroglobulin gene transcription and Thyroperoxidase synthesis
Where is the thyroglobulin mRNA translated?
In the RER
What happens to Thyroglobulin during transport from the RER to the golgi?
It is glycosylated
What happens to Thyroglobulin at the Golgi?
It is packaged into vesicles for exocytosis into the colloid.
How does Iodide get into follicular cells?
By active transport via Na/I symporter at the basal membrane.
What has to happen to iodide before it gets used?
Oxidation to iodine
What oxidizes iodide? Where? What is the product?
Thyroid peroxidase; in the follicular cell. Product is Iodine
What happens to Iodine?
It is spit out into the colloid.
What happens to Iodine in the colloid?
Another molecule of Thyroid peroxidase puts iodine onto thyroglobulin.
How does thyroid hormone on thyroglobulin get from the colloid to circulatory system when stimulated by TSH?
By pinocytosis of colloid containing thyroglobulin back into the follicular cell.
What happens to the bite taken up?
It fuses with lysosomes which release enzymes to degrade thyroglobulin and release T3/T4
How do T3/T4 get from the follicular cell into the blood?
By diffusion
How do T3/T4 circulate in plasma?
Bound to TBG
How is free hormone transported into target cells?
By diffusion or carriers
What happens to T4 at targets?
It's converted into T3
What does T3 do?
Binds its receptor in the nucleus and then binds HRE to turn on DNA.
What is the effect of T3?
Stimulation of O2 consumption and Heat production by stimulation of Na/K ATPase in all cells except 3.
What Na/K ATPase is not stimulated by T3's effects?
That in
What are Propothyouracile, Methimazole, and Carbimazole?
Thyroid peroxidase inhibitors used to treat hyperthyroidism
What do excess iodide and lithium inhibit?
Thyroglobulin proteolysis
How would Propothyouracil affect the morphology of follicular cells?
It would make them squamous
How would high TSH affect the morphology of follicular cells?
It would make them cuboidal
What is hypothyroidism in infants? Adults?
Infants - cretinism
Adults - myxedema
What is cretinism?
Mental retardation, short stature, and puffy face and hands.
What is myxedema?
Chronic fatigue
Puffy face and hands
Treatment for hypothyroidism?
What is levothyroxine?
What is hyperthyroidism?
Graves disease
What happens if you remove the parathyroid glands?
1. Blood calcium decreases
2. You go into tetany
3. You die
How many parathyroid glands are there?
Usually 4
What are the 2 types of cells in PT glands? Which are more numerous? Which are bigger?
Chief cells - more
Oxyphil cells - bigger
What do Chief cells secrete?
What do oxyphil cells secrete?
Don't know
What do oxyphil cells look like?
What regulates PTH synthesis and secretion?
Calcium receptors
What increases PTH secretion?
Lack of Calcium binding its receptor.
Why doesn't calcium binding its receptor on the parathyroids increase vesicular exocytosis of PTH?
Because stimulus-secretion coupling in the parathyroid cells occurs via Mg2+
What inhibits PTH gene transcription?
High levels of vit D
What does PTH do to bone?
Stimulates resorption to increase blood calcium
What does PTH do to kidney?
Increases calcium reabsorption
Decreases phosphate reabsorption
Increases Vit D activation
What is the result of Vit D activity?
Increased intestinal calcium reabsorption
What are the 4 zones of the adrenal medullae? What does each secrete?
1. Zona glomerulosa, Aldo
2. Zona fasciculata, glucocorts
3. Zona reticularis, DHEA and glucocorticoids
4. Medulla - catecholamines
What do the cells in the zona glomerulosa look like?
Clusters of small cells with little cytoplasm
What do the glomerulosa cells secrete?
Mineralcorticoids (aldosterone)
What regulates secretion of the mineralcorticoids?
The renin angiotensin system
What is hyposecretion of aldosterone?
Addison's disease
What does Addison's disease lead to?
What does the cell arrangement in the zona fasciculata look like?
-Arranged in long straight cords
-Separated by sinusoidal capillaries
What do the cells in the zona fasciculata secrete?
DHEA + Cortisol
What is secreted from the Zona reticularis?
DHEA and Cortisol
What regulates secretion of DHEA and cortisol?
CRH and ACTH system
What causes CAH?
Lack of 21 hydroxylase
What results from CAH?
-Virilism in girls
-Increased ACTH
-Hypertrophy of the adrenals
What do the cells in the Zona Reticularis look like?
They are small with abundant lipofuscin granules
What are the cells in the Adrenal Medullae?
Pale staining chromaffin cells that are modified neurons
What catecholamines are secreted from the medulla?
What exactly stimulates the secretion of Epi/Norepi from the medulla?
The release of ACh from preganglionic sympathetic neurons
What is Pheochromocytoma?
A tumor of the adrenal medulla
What are symptoms of Pheochromocytoma?