Lecture 9: Histology of Endocrine Organs Flashcards
1
Q
What is difference between the endocrine and nervous system?
A
- Nervous:
- Rapid communication
- Short lived effects
- Endocrine:
- Slower communication via release of hormones into blood and binding on receptor cells
- Longer lasting effects
2
Q
What are the stimuli that control hormonal release?
A
- Humoral
- Neuronal
- Hormonal
3
Q
What is humoral stimuli?
A
- Release of hormones are controlled by levels of ions and nutrients in blood/body fluids
- Ex: PTH stimulated by low Ca2+ levels
4
Q
What is neuronal stimuli?
A
- Release of hormones stimulated by nerve signals
- Ex: Epinephrine is relased from adrenal gland signaling via sympathetic nerve fibers
5
Q
What is hormonal stimuli?
A
- Hormones secreted into the blood by another endocrine tissue
- Ex: TSH from pituitary gland stimulates TH release in the thyroid
6
Q
How are endocrine glands organized?
A
- Epithelioid cells are arranged as cords/follicles
- lacks free surfaces (does not open to lumen)
- Well vascularized
- Vessels have fenestrated endothelium
- Large pores help hormones travel
7
Q
What are the direct targets of hypothalamic hormones?
A
- Anterior pituitary gland (releasing and inhibiting factors)
- Posterior pituitary gland
- ADH: kidneys and ureters
- Oxytocin
- Adrenal medulla (sympathetic innervation)
8
Q
What are the indirect targets of hypothalamic hormones?
A
- Tropic (releasing/inhibitory hormones)
- Indirectly influences these organs via the anterior pituitary:
- Thyroid gland: TSH
- Adrenal cortex: ACTH
- Mammary gland: PRL
- Gonads: FSH/LH
- Bone: GH, MSH
9
Q
What are the embryoligcal origins of the anterior and pituitary gland?
A
- Anterior Pituitary: Surface Ectoderm
- From Rathke’s Pouch
- Posteriot Pituitary: Neuroectoderm
- From diencephalon
10
Q
What type of cells compose most of the anterior pituitary gland?
A
Glandular epithelial cells controlled by neurohormones released from hypothalamus
11
Q
What composes most of the posterior pituitary gland?
A
Axons from hypothalamus and support cells
Looks like nerve tissue
12
Q
Identify the various components of the pituitary gland and what they make up.
A
- Pars Distalis: Makes up anterior pituitary
- More basophilic
- More rough ER to make hormones
- Pars Nervosa: Makes up most of posterior pituitary
- Neural tissure
- Pars Tuberalis: surrounds infundibulum
- Cyst intermedia: remnant of lumen of Rathke’s pouch
13
Q
What are some major cell types in the anterior pituitary?
Are they acidophilic or basophilic?
A
Acidophilic:
- Somatotropic cells
- Mammotropic cells
Basophilic:
- Thyrotropic cells
- Corticotropic cells
- Gonadotropic cells
14
Q
What do somatotroph cells release?
How do they stain?
A
- Secrete Growth Hormone (GH) in response to GHRH
- Acidophilic (lighter)
15
Q
What do mammotroph cells release?
How do they stain?
A
- Secrete prolactin to stimulate milk production
- Acidophilic (stain lighter)
16
Q
What do corticotroph cells release?
How do they stain?
A
- Secrete ACTH: stimulates adrenal cortex to secrete stress related hormones and mediate metabolism
- Secrete MSH: stimualte melanocytes to produce melanin to mediate behavior, arousal, and hunger
- Basophilic (stains lighter)
17
Q
What do thyrotroph cells release?
How do they stain?
A
- Secrete TSH
- Basophilic (stain darker)
18
Q
What do gonadotropic cells release?
How do they stain?
A
- Secrete FSH and LH
- Basophilic (stain darker)
19
Q
Identify the following structure.
What is this a remnant of?
A
Pars Intermedia
- Has a cleft, which is a remnant of the lumen of Rathke’s pouch
20
Q
What does the pars nervosa consist of?
A
- Unmyelinated axons from hypothalamus
- Herring bodies: axonal nerve terminals that store ADH and oxytocin
- Pituicytes: glia like
- Fenestrated capillaries
21
Q
How does blood supply to the hypothalamo-hypophyseal portal system work?
A
- Primary Capillary Plexus: neurons of hypothalamus that release hormones for anterior pituitary gland travel through capillary system
- Hormones travel through portal veins in anterior pituitary
- Secondary Capillary Plexus: hormones from anterior pituitary gland enter general circulation to teach targers
22
Q
How does the hypothalmo-hypophyseal tract work in the posterior pituitary gland?
A
- Hypothalamus synthesize ADH and oxytocin
- ADH and oxytocin are transported to posterior pituitary for storage
- ADH and oxytocin are released via hypothalamic signals
23
Q
Where is the pineal gland located?
What does it consist of?
A
Outpocketing of diencephalon’s roof of the third ventricle
Consists of
- Pinealocytes: secretes melatonin
- Neuoglia
- Calcified granular material
24
Q
What is the function of the pineal gland?
A
- Regulates growth, development, and circadian rhythms
- Snythesizes serotonin and melatonin
25
What are the histological characteristics of the thyroid gland?
What is unique about the thyroid?
* Contains **follicles** with a layer of follicular cells (simple cuboidal/simple columnar) surrounding **colloid** fluid
* Colloid contains thyroglobulin (storage form of T3 and T4)
* Only gland to store hormones outside of the cell
26
How are thyroid hormones synthesized and releasd?
1. Thyroglbulin synthesized in rER and stored extracellulary
2. T3 and T4 are bound to thyroglobulin and iodinated at the apical surface
3. TSH stimulates internalization thyroglobilun via endocytosis, freeing T3 and T4-released to basal surface into blood
27
**Parafollicular C Cell**
Where is it located?
What is its function?
What is its embryolical origin?
* Next to follicles in thyroid goand (periphary)
* Function: Lower Blood Calcium Levels
* Secretes calcitonin (*tone down calcium*)
* Stimulates excretion of Ca2+ by kidneys
* Decreases Ca2+ releasing activity of osteoclasts
* Increases osteogenesis by osteoblasts
* _Neural Crest Derived_
28
What is Grave's Disease and its sypmtoms?
How does it occur?
* Abnormal antibodies stimulate TSH receptors, _increasing secretion of T3 and T4 from thyroid_
* Symptoms:
* Elevated metabolism
* Sweating
* Rapid HR
* Weight Loss
* Eyeballs may protrude
* More common in women
29
How does hypothyroidism occur?
What is its symptoms?
* Insufficient T3 and T4 production most likely due to an autoimmune disease
* Symptoms:
* Low metabolic rate
* Weight gain
* Lethargy
* Chilliness
* Edema
* Mental sluggishness
30
What can cause a goiter?
* Thyroid enlargement due to **iodine** deficiency
* Follicular cells keep making thyroglobulin but cannot iodinize it to make T3 or T4
31
**Parathyroid Glands**
What cell types are present?
What hormones do they release?
* Found on posterior surface of thyroid
* Function: Regulate calcium and phosphate levels
* Chief Cells: release PTH to increase calcium levels
* Oxyphil cells: unknown function
32
How does PTH regulate calcium levels?
* If calcium levels low (\<9.5 mg/dL), parathyroid releases PTH into bloodstream
* Stimulates osteoclasts to resorb bone and release Ca2+ stores
* Stimulates kidney to convert inactive form of Vitamin D to Calcitriol
* Calcitriol increases Ca2+ absorption by intestines
* As calcium levels increase, PTH is inhibited
33
What are the three layers of the adrenal cortex and what are their functions?
* **Zona Glomerulosa:** Influence Na+ and K+ levels
* _Aldosterone:_ secreted in response to low BP/BV
* **Zona Fasciculata:** Influences glucose metabolism and immune system
* _Cortisol:_ secreted to deal with stress and mediate glucose. Also negative feedback to immune system
* **Zona Reticularis:** Influence secondary sex characteristics
* Androgens released
34
Label the following components of the adrenal gland.
What hormones are secreted by 1-4?
1. Zona glomerulosa: aldosterone
2. Zona fasciculata: Cortisol
3. Zona Reticularis: Androgens
4. Medulla: NE and EPI
5. Cortex
6. Medulla
35
**Adrenal Medulla**
What cells compose it?
What is its embryological origin?
* Inner core of adrenal gland
* Stiumlated by presynaptic sympathetic to secrete epinephrine and norepinephrine
* Neural Crest derived
36
Histologically, what is the difference betwen epinephrine and norepinephrince cells?
* Epinephrine: smaller with granules and less electron dense
* Norepinephrince: larger with granules and less electron dense
37
**Addison's Disease**
What causes it?
What are its symptoms?
* _Hyposecretion_ of glucocorticoids and mineralcorticoids
* Blood glucose and sodium levels drop
* Causes: autoimmune disease or inherited metabolic disease leading to enzyme deficiencies
* Symptoms
* Hypotension
* Fatigue
* Loss of appetite
38
**Cushing's Syndrome**
What causes it?
What are its symptoms?
* _Hypersecretion_ of glucocorticoids
* Causes:
* ACTH secreting tumor in pituitary gland
* Tumor in adrenal cortex
* Symptoms:
* High serum glucose levels
* Protein loss in muscle
* Muscle weakness
* Lethargy
* Swollen Face
* Fat redistribution
* Depression of immune responses
39
How is the pancrease organized?
**Exocrine Portion:** majority of pancreas
* Aids in digestion
* Organized as _pancreatic acini_
**Endocrine Portion:**
* Organized as pancreatic islets or islets of Langerhans
* Scattered among exocrine cells
40
What cells are found in the endocrine pancreas?
* **Alpha cells:** secrete _glucagon_ when glucose levels are low
* Releases glucose from liver glycogen stores
* **Beta cells:** _insulin_ when glucose levels are high
* Promotes glycogen storage and entry of glucose into cells
* **Delta cells:** _somatostatin_ to slow the release of insulin and glucagon
* Stimulated by high levels of nutrients in the blood
* **F cells:** _pancreatic polypeptide_ that inhibits release of somatostatin
41
What is the pancreatic blood supply?
* Insuloacinar portal system
* Acinar vascular system
