Histology Flashcards
1
Q
What system is described? The hypothalamus (floor of diencephalon & forming part of the walls of the third ventricle) consists of clusters of neurons that secrete hormones
A
Neuroendocrine system
2
Q
The hypophysis (pituitary) is divided by the third ventricle into what two symmetric structures?
A
Adenohypophysis (anterior)
Neurohypophysis (posterior)
3
Q
What overall system consists of these 2 components?
- hypothalamic adenohypophysiial system
- hypothalamic neurohypophysial system
A
Hypothalamohypophysial system
4
Q
What connects the hypothalamus to the anterior hypophysis? What about the posterior hypophysis?
A
hypothalamic adenohypophysial system (anterior)
hypothalamic neurohypophysial system (posterior)
5
Q
The adenohypophysis consists of the pars ______ which secretes hormones.
The neurohypophysis consists of the pars ______, which stores hormones.
A
distalis
nervosa
6
Q
Rathke’s pouch formation:
- The infundibulum (a diverticulum) develops in the floor of the _________ and grows towards the stomodeum.
- An ectodermal region in the roof of the stomodeum invaginates to form a diverticulum called Rathke’s pouch
- Rathke’s pouch elongates towards the diverticulum
- The infundibulum descends to elongate Rathke’s pouch
- The regressing stalk of Rathke’s pouch can leave residual tissue, which may form a tumor called a ____________________
A
- diencephalon
5. craniopharyngioma
7
Q
The anterior lobe/adenohypophysis
is developed from what embryological structure?
What kind of embryonic tissue is this structure?
A
Rathke’s pouch
Ectoderm
8
Q
The posterior lobe/neurohypophysis
is developed from what embryological structure?
What kind of embryonic tissue is this structure?
A
Infundibulum of the diencephalon
Neuroectoderm
9
Q
Hypothalamohypophysial portal circulation:
Superior hypophyseal a.–>
Primary plexus of hypophyseal portal system–>
Hypophyseal portal vv.–>
_____ _______ of hypophyseal portal system (supplies the anterior pituitary!)–>
Hypophyseal vv.–>
Systemic vv.
A
Secondary plexus
10
Q
TQ
T/F: There is a direct arterial blood supply to the anterior hypophysis
A
FALSE
There is no direct bloody supply to the anterior hypophysis!
11
Q
What receives secretions from endocrine cells of the anterior hypophysis/pars distalis
A
Secondary plexus
12
Q
What supplies the neurohypophysis/pars nervosa and collects secretions from neuroendocrine cells in the hypothalamus?
A
Third capillary plexus (from the interior hypophysial a.)
13
Q
What is the main difference between the blood supplies of the anterior hypophysis and posterior hypophysis?
A
The posterior pituitary is for storage and has a direct blood supply whereas the anterior pituitary has indirect blood supply
14
Q
The pars distalis sits in what structure and is therefore hard to reach during surgery?
A
Sella turcica of sphenoid
15
Q
What is being described?
- Cords of epithelial cells
- Minimal connective tissue
- Fenestrated capillaries/sinusoids are part of secondary capillary plexus
- no blood brain barrier (promotes leakage :) )
A
Pars distalis
16
Q
Which cell of the pars distalis is being described?
- SRH/GHRH stimulates the pituitary to secrete growth hormone (somatotropin)
- Somatotropin/GH stimulates hepatocytes to produce IGF-1, which leads to growth of bone & soft tissue
- Ghrelin from stomach ensures that we have enough E to grow and stimulates somatotropin/GH as well
- Somatostatin inhibits GH
A
Acidophils/Somatotrophs
17
Q
What disorder of growth hormone secretion is described?
- excessive production of growth hormone beginning in CHILDHOOD
- Due to loss of feedback control of GH secretion or GH-secreting tumor in pituitary (adenoma)
- Skeletal growth as well as internal organs
- Sig. problems with blood glucose
- Death due to heart dz or diabetes
A
Pituitary gigantism
18
Q
What disorder of growth hormone secretion is described?
- Excessive ADULT production o GH
- Growth of face (prognathism), hands, & feet
- Increase in viscera
- Overprod. of glucose–>diabetes
- May be due to loss of feedback control of GH secretion or GH-secreting tumor in pituitary (adenoma)
What is the treatment?
A
Dx: Acromegaly
Tx: surgery, radiation, GH-Receptor Antag
19
Q
What disorder of growth hormone secretion is described?
- Growth retardation resulting in abnormally short adult stature
- Caused by hereditary and metabolic disorders leading to insufficient growth hormone
- Problem can be in hypothalamus (no signal) or pituitary (no/decr. response)
- May also be from inadequate nutrition in early life
What is the treatment?
A
Dx: Pituitary dwarfism
Tx: Growth hormone injections
20
Q
Varieties of hereditary dwarfism:
- _____________ (normal trunk size, short limbs, large head)
- Hypochondroplasia (similar but normal head size)
- Diastrophic dwarfism (progressive, crippling, skeletal deformities)
A
Achondroplasia
21
Q
Which cell of the pars distalis is being described?
- Mammotrophs
- Secretes prolactin, which stimulates initiation and maintenance of milk production
A
Acidophils/lactotrophs
22
Q
TQ
How is prolactin secretion controlled in acidophils/lactotrophs?
A
Through inhibition via dopamine! Unlike other hormones of the ant. hypophysis, the secretion of prolactin is regulated by inhibition rather than stimulation.
Note: Dopamine is the primary prolactin-inhibiting factor (PIF/PIH)
23
Q
How is secretion of prolactin secretion stimulated in acidophils/lactotrophs?
A
Mainly by suckling during lactation
Also: PRH (prolactin releasing hormone)
24
Q
How does prolactin act as a birth control?
A
Inhibits pulsatile secretion of GnRH, which leads to the suppression of FSH (follicle stimulating hormone) and LH ( ovulation)
25
Dx?
- Women presents with inability to become pregnant caused by lack of ovulation and oligomenorrhea (light period) or amenorrhea (no period)
- Men presents with decrease in fertility and libido
- Either gender may experience galactorrhea
- Reversible
Prolactin-secreting tumors-->hyperprolactinemia
26
The two hormones released by acidophils are growth hormone and prolactin. What are the 4 hormones released by basophils?
LH, FSH, TSH, ACTH
27
Which cell of the pars distalis is being described?
- Produces adrenocorticotropic hormone (ACTH) and liptrophic hormone (LPH)
- Derived from pro-opiomelanocortin (POMC)
- Products of POMC: ACTH stimulates hormone release by adrenal cortex & LPH stimulates lipid mobilization in mammals (NOT humans)
Basophils/corticotrophs
28
Which cell of the pars distalis is being described?
| -Produce follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in response to GnRH from hypothalamus
Gonadotrophs
29
What hormone produced by gonadotrophs stimulates ovarian follicle development/estrogen secretion or production of androgen binding protein by SERTOLI cells
FSH
30
What hormone produced by gonadotrophs causes ovulation and corpus luteum formation or production of testosterone by interstitial (LEYDIG) cells
LH
31
The release of FSH and GnRH is inhibited by estradiol & ______, secreted by the male & female target cells (sertoli cells and granulosa cells)
inhibin--->decr. follicles
32
The release of FSH in both females and males is enhanced by _______secreted by Sertoli cells and granulosa cells
activin-->incr. follicles
33
Which cell of the pars distalis is being described?
- Produce thyroid simulating hormone (TSH) or thyrotropin
- stimulates thyroid gland to synthesize, store, & release thyroid hormones
Thyrotrophs
34
What hormone allows release of TSH from thyrotrophs?
| What hormone inhibits?
TRH-->release
Inhibit via negative feedback suppression by CNS based on amount of circulating thyroid hormone
35
Pars __________:
- Cords of basophilic cells and colloid-filled follicles
- Synthesize proopiomelanocortin
- alpha and beta melanocyte-stimulating hormone stimulates melanin production
- Secretion causes darkening of skin in fish, amphibians, and reptiles as granules of melanin spread through melanophores!
intermedia
36
What is being described?
- Contains no secretory cells
- Unmyelinated axons of secretory neurons of the hypothalamus (paraventricular, supraoptic)
- Hormone storage and release
Neurohypophysis
37
TQ
Axons end in the pars nervosa and form large, fusiform swellings called ______ _______, filled with secretory product.
They are surrounded by specialized glial-like cells called ________
Herring bodies
Pituicytes
38
Hormones moved from the hypothalamus via hypothalamo-hypophyseal tract with ________.
Unmyelinated axons are located in the infundibulum
neurophysin
39
Which hormone produced by the paraventricular nuclei of the neurohypophysis stimulates uterine contraction and stimulates milk ejection?
Oxytocin
40
Which hormone produced by the supraoptic nuclei of the neurohypophysis increases water permeability of kidney tubules to decrease urine output and increase BP
Antidiuretic hormone (ADH)
41
Dx?
- Mass effects
- Hormone over/underproduction
- Hemorrhage/apoplexy
Pituitary adenoma
42
Dx?
>10 mm (1 cm)
-May grow superiorly into suprasellar region and impinge the optic chiasm to create bitemporal hemianopsia
-Tumor may also erode the sella turcica
-Increases intracranial pressure (w/ HA, N/V)
-Tx: trans-sphenoidal surgery
Pituitary macroadenoma
43
The pineal gland is also known as what two names?
epiphysis cerebri
| pineal body
44
Where is the pineal gland found?
posterior extremity of the 3rd ventricle and attached to the diencephalon by the pineal stalk
45
TQ What is the innervation to the pineal gland? Why is this important?
Postganglionic sympathetics from superior cervical ganglion
This allows the circadian clock to match the light of day
46
What are the most common cell type of the pineal gland?
- Arranged in clumps and cords w/in lobules
- Neuronal-like cells w/ large, irregular, nuclei
Pinealocytes
Notes: Sympathetic nerve fibers from the superior cervical ganglia enter the pineal gland with the blood vessels supplying the brain. When the nerve fibers enter the gland, the myelin sheath is lost and the bare axons are seen throughout the pinealocytes
47
What is brain sand? Why is this important?
Corpora arenacea are radiopaque & are a useful landmark for radiologists since the pineal gland is midline
48
Light signals are sent to the hypothalamus by the retinohypothalamic tract. Information from the superior cervical ganglion is conducted by postganglionic sympathetic fibers into the pineal gland. In this way, darkness stimulates the production of what?
melatonin
49
Melatonin acts on both the hypothalamus and anterior hypophysis to inhibit the secretion of what? (2)
gonadotropin and growth hormone
50
Individuals with tumors of the pineal gland may experience what effect?
precocious puberty
51
- Synthesis and secretion of melatonin is affected by light exposure to the eyes.
- Serum concentrations of melatonin are low during the daylight hours & peak during the dark.
- Therefore, the duration melatonin secretion each day is proportional to the length of the night.
- In this way, melatonin helps to establish what within the body?
circadian rhythm
52
T/F: Melatonin is probably not a major regulatory of normal sleep patterns, but has some effect
TRUE
Has been used alone or in combo with phototherapy
Some indication that melatonin levels are lower in elderly insomniacs relative to age matched non-insomniacs, in which melatonin therapy helps
53
Dx?
- Experience depressive symptoms in the winter
- N or S of 30 degrees
- Depression, lack of energy, increased need for sleep, craving for sweets, weight gain
- Symptoms begin in fall, peak in winter, resolve in spring
Seasonal affective disorder (SAD) or winter depression
54
T/F: There is no direct evidence for pineal effects in humans, but in seasonally breed animals the pineal mediates the responses of the reproductive system to changes in day length
TRUE!
Ex: In deer, decr light in fall-->incr fertility and breeding
55
Melatonin is a gonadosuppressive hormone. Why?
- Pineal gland hormonally regulates gonad development by suppressing the activity of cells that produce gonadotropin releasing hormone in the hypothalamus
- No GNRH, no gonadotropins, no fully fx gonads
Ex: Melatonin is high in young boys but decreases at puberty
56
Pineal abnormalities causing decreased secretion of melatonin will cause what?
Early onset of puberty
Note: vs tumors that stimulate secretion of pineal hormones and retard gonadal development/ delay puberty
57
Formation of the thyroid gland:
- __________ mass of cells invaginates into underlying mesoderm to create the thyroid diverticulum (b/t ant 2/3 and post 1/3 of the tongue)
- The diverticulum grows inferiorly between skeletal elements of 2nd and 3rd pharyngeal arches
- Migrates to a position ant. and above the trachea
Endodermal
58
Each lobe of the thyroid gland consists of follicles filled with colloid. Therefore, where does the thyroid store its products?
extracellularly as thyroglobulin (TGB)
59
How do we regulate the thyroid?
The follicular epithelium has receptors for TSH from the ant. pituitary
```
Brain/hypothalamus-->
TRH-->
Ant. pituitary-->
TSH-->
Thyroid-->
Thyroid hormones (feedback inhib)
```
This controls both synthesis (exocrine) and secretion (endocrine) of hormones
60
Synthesis in the thyroid:
Uptake of aa & iodide into cell-->
Thyroglobulin (TGB) synthesis on RER-->
Addition of iodine to tyrosine residues of TGB by _____ _____, released into lumen by exocytosis (inhib by anti-thyroid drugs)
tyrosine peroxidase
61
TQ
Secretion (endocrine) in the thyroid:
TSH stimulates endocytosis & digestion of colloid-->
Colloid droplets fuse w/ lysosomes-->
Digestive enzymes breakdown TGB, releasing ___, ___, & _____-->
Products diffuse through membrane into capillary-->
Capillary transport by ______-____ protein
T3 (Triiodothyronine), T4 (thyroxine), & iodine
thyroxine-binding protein
62
What happens if you have low blood levels of T3 and T4?
```
Hypothalamus releases TRH-->
Pituitary releases TSH-->
Thyroid releases T4 and T3-->
Combines with thyroid binding proteins from the liver-->
Form hormones!
```
This then inhibits the pituitary from releasing more TSH.
63
What are the 4 functions of thyroid hormone?
1. Stimulates basic metabolic rate
2. Augments thermogenesis
3. Augments glucose production
4. Required for normal development of CNS
64
Causes of the following?
- Increased metabolic rate
- Weight loss
- Heat intolerance
Hyperthyroidism (excessive TSH) by:
- Excessive stimulation by adenohypophysis
- Loss of feedback control by thyroid gland (Graves)
- Ingestion of T4 (for wt loss)
65
TQ
Dx?
-Autoimmune disorder that produces antibodies to TSH receptors on follicular epithelium
-Antibodies bind and chronically stimulate-->too much thyroid hormone
-Exopthalamos: collagen deposition behind the eye (orbital fat TSHR-R)
-Tx: surgical removal, radioactive iodine
-Post-Tx regimen requires thyroid hormones
Graves' disease
66
Causes of the following?
- Insuff production of thyroid homrone
- low metabolic rate, feeling of being cold, wt gain
Hypothyroidism (not enough TSH):
- Decreased iodine intake
- Loss of pituitary stimulation
- Post-therapeutic/destruction of thyroid by immune system
67
TQ
Dx?
-Autoimmune dz assoc with hypofunction of thyroid gland
-Autoantibodies (antimicrosomal Ab) to thyroid peroxidase & thyroglobulin
-Tx: Oral thyroid meds
Hashimoto's dz
68
Dx?
- Vary in size and may involve all or some of the glands/lobes
- Endemic or sporadic
- Endemic caused by iodine def
- Pituitary releases more TSH but gland cannot respond
- Avoided by adding iodine to diet
- Tx=surgery
Goiter: enlargement of thyroid gland
Note: multinodular goiter if many nodules involved
69
Dx?
- Severely stunted physical & mental growth due to untreated congenital deficiency of thyroid hormones
- Endemic, genetic, or sporadic
- Sporadic and genetic forms result from abnormal development or fx of the fetal thyroid gland. Almost eliminated by newborn screening programs + lifelong thyroid hormone tx.
Congenital hypothyroidism
70
Dx?
- Poor length growth and bone maturation and puberty severely delayed
- Ovulation impeded and infertility common
- Neuro impairment mild to reduced muscle tone and coordination to cannot stand/walk
- Cognitive impairment mild to severe (nonverbal and dependent on others)
- Tx: salt
Congential hypothyroidism
71
What are C cells? What do they contain?
Parafollicular cells in the follicular epithelium of the thyroid that contain small granules of calcitonin
72
What does calcitonin do?
- Decreases calcium concentration by inhibiting bone resorption
- Binds to receptor on osteoclast
- Hypercalcemia: high Ca stimulates calcitonin
73
The parathyroid glands originate from endoderm of the 3rd & 4th pouch. The position of the glands reverses during development. Therefore, the pair of glands that is ultimately inferior develops from the _____ pouch, and the pair of glands that is ultimately superior develops from the _____ pouch.
3rd
4th
74
What are the two cell populations supplied by sinusoidal capillaries?
Cells are arranged in cordlike or follicular-like clusters
- Chief/principal cell (more numerous)
| - Oxyphil/acidophilic cell
75
Chief (principal) cells secrete what hormone?
Parathyroid hormone (PTH)
76
TQ
| T/F: The parathryoid gland is the only endocrine gland with adipose tissue
TRUE
77
How is parathyroid hormone regulated?
Ca binds to extracellular region of Ca-sending receptor (CaSR) on a chief cell-->
Intracellular G protein signals suppress PTH secretion-->
Decr in Ca-->
PTH secretion stimulated-->
Incr Ca
78
PTH acts on:
- osteoblasts/osteoclasts to promote osteoclast activity
- renal tubules to stimulate resorption of calcium
- Controls rate of Ca uptake in GI tract by regulating production of Vit D (kidneys)
(Vit D stimulates cells of intestinal mucosa to absorb Ca and synthesize _______ (carrier protein))
osteoblasts!!
calbindin
79
- Blood calcium is low but bone calcium not released
| - Results in spontaneous depolarization of neurons & muscle fibers resulting in tetany
Hypoparathyroidism (def in PTH)
80
- High blood calcium levels
- Bone loss-->osteomalacia and osteitis fibrosa cystica
- Causes abnormal calcium deposition in aa. and kidneys
Hyperparathyroidism
81
Pancreas development:
- Week 4: two endodermal outpockets of duodenum develop ventral and dorsal pancreas
- _______ pancreas forms the head of the pancreas and associates with common bile duct, while the other forms body and tail
- Week 12: pancreatic acini develop from ducts
- Wks 12-16: Endocrine cells observed on exocrine acini
Ventral
82
What are the 2 portions of the pancreas?
- Exocrine (acini that synthesize and secrete digestive enzymes through a duct into duodenum)
- Endocrine (islets of Langerhans)
83
What forms the islets of Langerhans?
- Endocrine cells A, B, D, and F
| - Vascular component (insuloacinar portal system that enables local action of insular hormone on the exocrine pancreas)
84
T/F: The pancreas has a dual blood supply? If so, what is it?
TRUE!
- Insuloacinar portal system-->islets of Langerhans
- Acinar vascular system-->pancreatic acini
85
TQ
What is the following pancreatic hormone produced by and function as?
Glucagon
Alpha cells
Increases glucose blood levels
86
TQ
What is the following pancreatic hormone produced by and function as?
Insulin
Beta cells
Increases transport of glucose into cells & decreases blood glucose levels
87
TQ
What is the following pancreatic hormone produced by and function as?
Somatostatin
Delta cells
Inhibits release of insulin & glucagon, & the secretion of HCl by parietal cells
88
TQ
What is the following pancreatic hormone produced by and function as?
Gastrin
Delta cells
Stimulates production of HCl by parietal cells in the stomach
89
TQ
What is the following pancreatic hormone produced by and function as?
Pancreatic polypeptide
F cells
Inhibits the secretion of somatostatin & the secretion of pancreatic enzymes
90
The adrenal cortex is of __________ origin and produces steroid hormones
The adrenal medulla is of ____________ origin and produces ____________
The adrenal cortex is of mesodermal origin and produces steroid hormones
The adrenal medulla is of neuroectodermic origin and produces catecholamines
91
What are the 3 zona's of the adrenal gland?
outside-->inside
zona glomerulosa
zona fasciculata
zona reticularis
92
TQ
| The adrenal medulla has a _____ blood supply through the long cortical aa. as well as sinusoids from cortex
direct
93
What does the zona glomerulosa produce in response to angiotensin II and ACTH?
Mineralocorticoids (Aldosterone)
Involved in electrolyte (Na and K) & water balance
94
TQ
What does the zona fasciulata secrete? (2)
What do the cells look like?
Glucocorticoids and androgens
Cells have many lipid droplets so looks vacuolated (foamy)
Also called spongicytes
95
TQ
What does the zona fasciculata secrete? (2)
What does it regulate?
Stress hormones!:
-Glucocorticoids cortisol and corticosterone
Regulates: carb, protein, fat metab
- Liver: promotes uptake of FA, AA, and carbs
- Catabolic effect
- May suppress immune system (decr lymphocytes)
96
How does the zona reticularis differ from the zona fasciculata?
The zona reticularis secretes mostly androgens (little glucocorticoids), while zona fasciculate produces both.
97
Which cells of the adrenal medulla are described?
- polyhedral cells in cords/clumps
- sympathetic postganglionic neurons
- lost axons & dendrites during embryonic devel-->secretory cells
- secrete granules of epi or nor-epi
chromaffin cells
| silver stain
98
What is described?
- Secreted in response to intense emotional reactions
- defensive reaction to stress
- incr HR
- Dilates blood vessels to cardiac & skeletal m.
- Bronchiole dilation
- Vasoconstriction of blood vessels to GI
Catecholamines
99
Dx?
- Benign tumor of chromaffin cells
- Episodic secretion of epinephrine and nor-epi
- sympathetic nervous system hyperactivity (incr HR, BP, palpitations, diaphoresis, anxiety, HA, nausea, pallor)
- Life threatining HTN and cardiac arrhythmias
Pheochromocytoma
100
What can the infamous feud in American folklore b/t the Hatfields and Mccoys be explained by?
Hint: leads to rage and violent outbursts
von hippel-lindau
3/4 of the Mccoys had pheochromocytomas (adrenal gland tumors)
