NJDS- Histology

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QUESTION What are three characteristics of endocrine glands?: ANSWER
1) No ducts
2)Deposit hormones directly into bloodstream
3) Richly vascularized
QUESTION What is the dual blood supply of the adrenal medulla?: ANSWER
Arterial blood via the medullary arteries, and venuous blood via the cortical arteries.
QUESTION What is the blood supply of the adrenal glands?: ANSWER
Arterial branches--> subcapsular plexus--> adrenal capsule--> cortical + medullary capillary beds
QUESTION What are the three layers of the adrenal cortex (outermost to innermost)?: ANSWER
1)Zona glomerulosa
2)Zona fasciculata
3)Zona reticularis
QUESTION Characteristics of the zona glomerulosa: ANSWER
Outermost layer of cortex, comprised of cords and clusters of columnar cells which produce mineralocorticoid hormones (mainly aldosterone) when stimulated by angiotensin II or ACTH.
QUESTION Characteristics of zona fasciculata: ANSWER
Middle layer of adrenal cortex, large polyhedral cells which produce glucocorticoid hormones (cortisol and corticosterone) when stimulated by ACTH. Largest part of adrenal gland.
QUESTIONS What do cortisol and corticosterone do?: ANSWER
-Anabolic and catabolic processes
-Help organism withstand stress
-Anti-inflammatory
-Immune supression
QUESTION Characteristics of zona reticularis: ANSWER
Innermost layer of adrenal cortex, irregular darkly staining cells that produce androgens and small amounts of glucorticoids when stimulated by ACTH. Cells also contain lipofuscin pigment.
QUESTION True or False: Cells of the adrenal cortex store their products in secretory granules: ANSWER
False, cells of the adrenal cortex release their products into the bloodstream upon stimulation
QUESTION What is the main cell of the adrenal medulla, and what does it secrete?: ANSWER
Chromaffin cells (modified postganglionic secretory neurons) which secrete epinephrine and norepinephrine upon sympathetic stimulation
QUESTION What is the role of the thyroid gland?: ANSWER
The thyroid gland plays a role in the stimulation of metabolism through the synthesis of thyroxine (T4) and triiodothyronine (T3)
QUESTION What is the most abused non-narcotic drug by physicians?: ANSWER
Sinthroid (speeds up metabolism, keeps you up)
QUESTION What is colloid and what does it contain?: ANSWER
Eosinophilic substance within the thyroid follicles, contains T3 and T4 bound to thyroglobulin.
QUESTION How does a follicular cell of the thyroid obtain thyroid hormone?: ANSWER
When thyroid hormone is in demand, the follicular cell extends pseudopods into the surrounding colloid and brings the colloid into the cell.
QUESTION What are parafollicular (C) cells?: ANSWER
Found between thyroid follicles, larger and paler than follicular cells, secrete CALCITONIN
QUESTION Describe the synthesis of thyroid hormones: ANSWER
-Requires iodide and is regulated by TSH from the ant. pituitary
- Iodide is actively transported into follicular cell, where thyroid peroxidase in the cytoplasm oxidizes it.
- Oxidized iodide moves back into the colloid where it iodinates the tyrosine residues of thyroglobulin.
- Forms MIT and DIT
- MIT +DIT = T3
- DIT + DIT = T4
QUESTION Describe the release of thyroid hormones: ANSWER
TSH--> basolateral membrane of follicular cell--> cytoplasmic extensions of apical membrane bring in some colloid (endocytosis)-->lysosome in FC breaks down components of colloid into MIT, DIT, T3, T4 --> T3 and T4 leave cell, MIT + DIT are broken down into iodine and tyrosine and recycled
QUESTION What are the functions of thyroid hormones?: ANSWER
Thyroid hormones, in general, increase carbohydrate metabolism, fatty acid synthesis and vitamin uptake. They DECREASE cholesterol, phospholipid, and triglyceride synthesis.
QUESTION Describe the 2 cells found in the parathyroid glands, and what happens with age: ANSWER
1)Chief cells: most numerous, cytoplasmic granules contain PTH

2)Oxyphil cells: larger than chief cells, with abundant mitochondria, unknown function

3) With age, parenchyma is gradually replaced by adipose tissue.
QUESTION What is the function of the parathyroid glands?: ANSWER
Regulation of serum calcium levels through the actions of PTH
QUESTION How does PTH act on bone and kidneys?: ANSWER
In bone: PTH stimulates osteoclast activity and number.

In kidneys: PTH makes cells of renal tubule resorb calcium and prevent resorption of phosphate. Also, PTH induces production of the active form of vitamin D, which enhances calcium reapsorbtion in intestine.
QUESTION What are the characteristics of the pituitary gland?: ANSWER:
-Derived from both neural and oral ectoderm
-Produces and stores hormones for growth, metabolism, and reproduction
-Divided into anterior and posterior pituitary
QUESTION What are the 3 sections of the anterior pituitary (aka adenohypophysis) and what layer is it derived from?: ANSWER
1) Anterior lobe (pars distalis)
2) Pars tuberalis
3) Pars intermedia

Anterior pituitary is derived from oral ectoderm (Rathke's pouch)
QUESTION What are the two components of the posterior pituitary and what layer is it derived from?: ANSWER:
Composed of pars nervosa and the infundibulum (neural stalk), derived from neural ectoderm)
QUESTION What is the hypophyseal portal system?: ANSWER:
Portal venous system is the only connection between the anterior and posterior pituitary. Portal system transports neurosecretory hormones from the hypothalamus -->ant. pituitary, where they modulate secretion of ant. pituitary hormones.
QUESTION What are somatotrophs? What releases and inhibits them?: ANSWER
Acidophilic chromophil from the pars distalis, secretes GROWTH HORMONE, which increases metabolic rate and the growth of long bones.

Releasing hormone: SRH
Inhibiting hormone: Somatostatin
QUESTION Characteristics of mammotrophs: ANSWER
Type of acidophilic chromophil from the pars distalis, secrete PROLACTIN, which is for development of mammary glands during pregnancy + milk secretion.

Releasing hormone: PRH
Inhib. hormone: PIH
QUESTION Characteristics of corticotrophs: ANSWER
Basophilic chromophil from pars distalis, secrete ACTH which stimulates release of hormones from adrenal cortex

Releasing hormone: CRH
QUESTION Characteristics of thyrotrophs: ANSWER
Basophilic chromophil in pars distalis, secrete TSH

Releasing hormone: TRH (thyrotropin releasing hormone)
Inhib. hormone: presence of serum T3 and T4
QUESTION Characteristics of gonadotrophs: ANSWER
Basophilic chromophil in pars distalis. Secrete follicle stimulating hormone (FSH) and leutinizing hormone (LH)

Releasing hormone: GnRH
Inhib. hormone: serum estrogen, progesterone, and testosterone
QUESTION How do basophil hormones differ from acidophil hormones?: ANSWER
Basophils differ from acidophils in that they have no specific inhibiting hormones (instead, basophils are inhibited by neg. feedback-- presence of substance released from target organs)
QUESTION What is the most common secretory cell type in the pars tuberalis of the ant. pituitary?: ANSWER

Gonadotrophs
QUESTION What is secreted by the cells of the pars intermedia?: ANSWER

Melanocyte stimulating hormone(MSH)
QUESTION What are Herring bodies?: ANSWER
Neurosecretory granules accumulate in the pars nervosa and cause distension of the axon, forming pale basophilic Herring bodies.
QUESTION What is a pituicyte?: ANSWER
Glial cell bordering the axon in the pars nervosa (posterior pituitary)
QUESTION What are the two hormones secreted from the posterior pituitary?: ANSWER
1)ADH- increases water permeability in renal collecting tubules, concentrating urine.

2)Oxytocin: causes smooth muscle contraction in childbirth, and mammary gland milk ejection
QUESTION What governs the function of the pineal gland?: ANSWER
Circadian rhythms
QUESTION What are 3 things found in the pineal gland?: ANSWER
1)Pinealocytes which secrete melatonin and seratonin
2)Astrocyte-like interstitial cells
3) Corpora arenacea: concentric basophilic calcifications

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