Bsf Exam 4: Endocrine Histology Part 1

Front 1

What are the three hormone chemical classes of the endocrine system?

Water or lipid soluble?

Examples of each

Back 1

1. Proteins, polypeptides - water soluble (ex. insulin and follicle stimulating hormone)

2. Amino acid derivatives - water soluble (ex epinephrine)

3. Steroids - lipid soluble; from cholesterol (ex. testosterone and progesterone)

Front 2

Hormones elicit an action on the target organ by binding to a receptor that initiates ______ (the translation of signal to biochemical reaction)

Back 2

signal transduction

Front 3

Hypophysis, also called _____, is a pea sized gland that is on the base of the ______

This is important in regulating (3):

Back 3

-pituitary gland
-sella turcica

Important in regulating:
-growth
-reproduction
-metabolism

Front 4

What are the two divisions of the hypophysis?

Back 4

-adenohypophysis (anterior pituitary)
tissue derived from roof of mouth, epithelial ectoderm

-neurohypophysis (posterior pituitary)
tissue derived from base of brain (diencephalon), nueral ectoderm

Front 5

Adenohypophysis develops from _______

Back 5

-Rathke's Pouch (evagination of roof of mouth)

Front 6

What are the three divisions of the adenohypophysis?

Back 6

-Pars distalis (anterior lobe) - largest part
-Pars tuberalis - funnel-shaped region that surrounds neural stalk
-Pars intermedia - thin remnant of posterior wall opposed to the infundibulum of neurohypophysis

Front 7

What are the three divisions of the neurohypophysis?

Back 7

-Pars nervosa - Largest portion containing neurosecretory nerve endings
-Infundibulum - stalk-like portion containing axons of neurosecretory nerves
-Median eminence - extends from inferior aspect of hypothalamus, maintains connection w/ brain

Front 8

What are the two categories of the pars distalis?

Back 8

-Chromophils and Chromophobes

*Based on degree of staining

Front 9

The chromophils of the pars distalis can be divided into what two groups?

Back 9

-Acidophils (stain with acid dyes)
-Basophils (stain with basic dyes)

Front 10

Acidophils in chromophils of the pars distalis can be further divided into these functional categories:

Back 10

-somatotrophs - secrete growth hormone (somatomedin is a protein synthesized in liver that stimulates growth of long bones; stimulated by GH)
-Mammotrpohs (lactotrophs) - secrete prolactin (promotes mammary gland development during pregnancy and lactation after birth)

Front 11

Basophils in chromophils of the pars distalis can be further divided into these functional categories:

Back 11

-Corticotrophs - secrete adrenocorticotropic hormone (ACTH) (stimulates adrenal cortex)
-Thyrotrophs - secrete TSH or thyrotropin (stimulates release of TH)
-Gonadotrophs - secrete FSH and LH

Front 12

What do gonadotrophs do in females and males?
*Gonadotrophs are basophils in chromophils of the pars distalis

Back 12

-Females: monthly release of FSH and mid-montly LH surge triggers ovulation
-Males: FSH initiates spermatogenesis and LH stimulates steroid hormone production in Leydig cells

Front 13

What are chromophobes?

Back 13

One of the categories of the pars distalis that is thought to be stem cells that can develop into chromophils
*don't stain

Front 14

What are the nonsecetory cells of the pars distalis?

Back 14

-folliculostellate cells

Front 15

What is the pars intermidia?
What does it secrete?

Back 15

-cleft between pars distalis and pars nervosa

-secretes melanocytes stimulating hormone (MSH) (unknown function)

Front 16

What is the pars tuberalis?

Back 16

-(extension of anterior lobe) forms thin sleeve around infundibular stalk (of posterior lobe)

-Gonadotropins such as FSH and LH are secreted by most cells of the pars tuberalis

Front 17

This portion of the neurohypophysis extends from the floor of the hypothalamus:

Back 17

median eminence

Front 18

This portion of the neurohypophysis bridges the median eminence with the pars nervosa:

Back 18

infundibular stalk

Front 19

What are neurosecretory granules?
What are its contents?

Back 19

-Found in pars nervosa (posterior lobe) of neurohypophysis
(bulk of pars nervosa = unmylinated secretory axons)

Contents:
-oxytocin - hormone that stimulates contraction of smooth muscle in uterus and mammary gland myoepithelial cells (milk ejection)
-Antidiuretic hormone (vasopressin) - increase water resorbtion in renal collecting ducts and induces arterial smooth muscle contraction (increases BP)
-Neurophysins - binding proteins specific for each hormone

Front 20

Herring bodies are accumlations of _____

Back 20

neurosecretory granules

Front 21

What are pituicytes?

Back 21

Glial cells that are associaged with secretory axons. The nuclei are commonly found in the pars nervosa

Front 22

What two arteries supply the hypophysis?

What does each supply?

Back 22

-Superior and inferior hypophyseal arteries (branch of internal carotid artery)

-Superior - supply median eminence & neural stalk
-Inferior - primary supply the posterior lobe

Front 23

What forms the primary capillary plexus?
What drains the primary capillary plexus?

Back 23

-formed from superior hypophyseal arteries (network of fenestrated capillaries in median eminence)

-hypophyseal portal veins drain the primary capillary plexus

Front 24

Give the blood flow of the superior hypophyseal arteries:

Back 24

primary capillary plexus --> hypophyseal portal veins --> secondary capillary plexus

Front 25

Both secondary plexus and the posterior lobe exit the hypophysis into the ______

Back 25

-cavernous sinuses

Front 26

What is the critical function of the blood flow of the hypophysis?

Back 26

-Neurosecretory hormones are synthesized by hypothalmic neurons and are stored in median eminence (supplied by superior hypophyseal artery)
-Hormones can then be released at the primary capillary plexus and carried into the secondary plexus where they stimulate/inhibit effect on cells of the pars distalis

Front 27

The thyroid can be found immediately inferior to the ____

Back 27

larynx

Front 28

What joins the right and left lobe of the thyroid?

Back 28

isthmus

Front 29

What portion of the thyroid are thyroid secretory products stored?
What is the storage form of thyroid secretions?
What makes this different from other endocrine glands?

Back 29

-follicles
-colloid
-endocrine glands are stored extracellularly

*colloid is the inside of the spherical follicles

Front 30

What are the two cell types of the thyroid?

Back 30

-Follicular cells (principal cells)
-Parafollicular cells (C cells)

Front 31

What do the follicular cells of the thyroid secrete?
What are their functions?

Back 31

-Thyroxine (T4)
-Triiodothyronine (T3)

-regulation of cell and tissue metabolism
-induce increased protein synthesis and carbohydrate metabolism
-important in body growth and nervous system development (hormone binds nuclear receptors and stimulate RNA transcription)

Front 32

Which of the follicular cells of thryoid is more abundant? Which is more potent? Which is converted to the other by variious organs?

Back 32

-Thyroxine (T4) is secreted 10 times more, but is much less potent
-Thyroxine (T4) is converted to triiodothyronine (T3) by various organs

Front 33

What is thyroglobulin?

Back 33

inactive storage form of thyroid hormones (primary constituent of colloid)

Front 34

Iodide is pumped from ____ to ____ by iodine pumps

Back 34

blood to follicular cells

Front 35

What does thyroid peroxidase to?

Back 35

oxidizes iodide to iodine (iodine is released at apical surface into follicle lumen)

Front 36

That happens to tyrosine residues that are present in thyroglobin?q

Back 36

-it is iodinated in the follicular lumen

Front 37

What are the steps of the release of thyroid hormones into the bloodstream?

Back 37

-Follicular cells take up colloid droplets (via receptor mediated endocytosis)
-colloid resorption droplets fuse with lysosomes and preteases cleave iodinated residues from thyroglobulin
-monoiodotyrosine and diiodotryrosine becomes deiodenated (via thyroid deiodinase)
-liberation of T3 and T4

Front 38

What are the characteristics of the parafollicular cells (C cells)?
From where do they arise?
What do they secrete?

Back 38

-type of thyroid cell located between follicles and do not contace follicular lumen

-arise from neural crest

-secrete calcitonin - control blood calcium levels (concentration rises with rise in serum calcium levels - cause osteoclasts to revert to inactive state)

Front 39

Where are the parathyroid glands located?

Back 39

-four small glands which are located behind the thyroid

Front 40

How are vessels, lymphatics and nerves carried into the parathyroid gland?

Back 40

-connective tissue projects into the gland creating CT septa, that carries these into the gland

Front 41

What are the two cell types of the parathyroid gland?

Back 41

-Chief Cells (Principal cells)
-Oxyphil Cells

Front 42

What do the chief cells of the parathyroid gland secrete?
What is the function of this?

Back 42

-secretes PTH caused by the decrease in circulating calcium
-OsteoClast stimulating factor secretion is induced when PTH binds to receptors on osteoBlasts
-reduces calcium elimination (urine) and increases vitamin D production through kidney

*Chief cells are the most numerous cell types

Front 43

What are the function of the oxyphil cells of the parathyroid gland?

Back 43

-unknown function (may represent inactive or necrotic chief cells)

Front 44

What two hormones regulate calcium levels?

Back 44

-Calcitonin (from thyroid - parafollicular cells)
-PTH (from parathyroid - chief cells/principal cells)

*calcitonin has more rapid effect than PTH

Front 45

What changes occur in the parathyroid glands with age?

Back 45

secretory cells are replaced by adipose cells with increased age

*50-60% of the gland is adipose in older individuals

Front 46

Hormones that bind to cell surface receptors initiate signal transduction via different mechanisms, ALL of which involve what?

Back 46

protein kinase

Front 47

Endocrine glands differ from exocrine in that they (do/do not) have ducts.

Back 47

do NOT have ducts

-instead secretes hormones using blood stream or tissue fluids