14.2 Lab + Lecture Notes

Question 1

Endocrine Cell

Answer 1

• secretes a product basal (i.e into surrounding CT)
• can occur singly (e.g. tracheal/GI epithelia)
• can be a shared FXN of another cell type
• generally have prominent basal surface
• surrounded by dense + extensive capillary network
• usually (1 exception - follicular cells of thyroid) lack a lumenal (apical) surface

Question 2

Parathyroid

Answer 2

• most numerous cell = chief cell (sometime called principal cell)
• Oxyphil cell = minority cell type - increase in number with aging - so frequency is not the best way to recognize the cells

Question 3

Thyroid

Answer 3

= source of hormones T3 + T4 (both incorporate iodine in structure)

• secondary funciton = sequestering + storage of iodine
• contain follicular cells = endocrine cells with an apical surface that functions in storing the iodine

Question 4

Follicular cells

Answer 4

= endocrine cells with an apical surface (is rare occurrence)

• apical lumen forms a sealed compartemtn with iodine stored bound to thryoglobulin
• connect with each other via tight junctions - that create an apical and basal polarity to the cells

Question 5

Thyroglobulin

Answer 5

• prominent eosinophilic material
• fills the lumen of thyroid follicle
• better to be called colloid

Question 6

2 types of endocrine cells in thyroid

Answer 6

1) parafollicular cell = less frequent of the two
- called the C-cell
- produces calcitonin
2) ? follicular cell

Question 7

Pituitary

Answer 7

= endocrine organ sitting at base of brain

• surrounded + protected by Sella turcica (indention in base of skull)
• derived from apposition of 2 embryonic tissues
  1) Oral ectoderm –> adenohypophysis
  2) Neural ectoderm –> neurohypophysis

Question 8

Sella Turcica

Answer 8

= indentation in base of skull

- surrounds + protects the pituitary gland

Question 9

Neurohypophysis

Answer 9

• axons of neurons seen here whose cells bodies sit in hypothalamus
• 2 products secreted by the axons are:
  1) ADH
  2) Oxytocin

Question 10

Adenohypophysis

Answer 10

= collection of basal secreting cells surrounded by extensive capillary network

• 3 morphologically distinguishable parts
  1) Pars distalis - comprises bulk of structure
  2) Pars intermedia - lies immediately adjacent to neurohypophysis
  3) Pars tuberalis - surrounding stalk of pituitary (which is itself part of neurohypophysis)

Question 11

Classification of cells of adenohypophyssi

Answer 11

1) Acidophils
2) basophils
- hormones produced by basophils have glycogen precursors (will stain well in PAS stains)
3) Chromophobes

Question 12

Pineal Gland

Answer 12

• sits in center of brain
  = glandular tissue clustered in cords
  = surround by CT that is an extension of pail tissue of brain
• principle product = melatonin (inhibited by light and regulates circadian rhythms)
• has abundant capillaries
• morphologically distinguishable due to corpora arenacea
• parenchyma cell = pinealocyte
• has stromal glia cells too

Question 13

Corpora arenacea

Answer 13

= brain sand
= unique metabolic byproduct
- accumulated throughout life as microscopic calcified particles

Question 14

Pinealocyte

Answer 14

= parenchymal cell of pineal gland

Question 15

Adrenal Gland

Answer 15

• unique because is endocrine organ with a layered organization
• sits above kidney (suprarenal gland)
• surrounded by capsule of CT
• outermost portion = adrenal cortex
• inner portion = adrenal medulla
• the 2 parts are from separate embryonic sources

Question 16

Blood Supply/Flow in Adrenal Gland

Answer 16

• 3 suprarenal arteries - supply blood to gland
• 1 suprarenal vein - carries blood away
• blood flows from periphery to center

Question 17

3 layers of adrenal cortex

Answer 17

• all layers produce steroid hormones –> called corticosteroids
• layers from outside in:
  1) zona glomerulosa
  2) zone fasiculata
• cells have canonical appearance of steroid producing cells
• -> frothy/bubbly cytoplasm due to intracellular cholesterol
  3) Zona reticularis

Question 18

The amount of cholesterol in each layer of cortex depends on..

Answer 18

1) Whether enzyme that cleaves cholesterol (SCC) is rate-limiting step
2) Local availability of cholesterol carrier proteins (StAR)

Question 19

Medullary Arteries

Answer 19

= long cortical arteries

= arteries that traverse the cortex

Question 20

Adrenal Medulla

Answer 20

• 2 major products

- chromatin cells (named for high affinity for chromium salt dyes)

Question 21

Pancreas

Answer 21

• majority of it = exocrine gland that empires products into common bile duct
• islets of langerhans = islands of endocrine tissue in the exocrine tissue
• 4 types of intermixed cells (can be differentiated via antibody stains)
• products = glucagon, insulin, SST, PP
• products do not stain well in H&E compared to exocrine zymogen granules
• pancreas has unique circulation

Question 22

Unique circulation of Pancreas

Answer 22

• Blood enters islets via arterioles
• leaves via capillaries that then enter exocrine tissue
• exocrine pancreas sees concentrations of islet-produced hormones at higher concentrations than generally found in circulation

Question 23

Define a “hormone” through describing the possible types of secretions

Answer 23

• Autocrine secretion - affects the producing cells
• paracine secretion - affects the neighboring cells
• neurocrine secretion - secretion from a neuron to a cell (specialized type of paracrine)
• “true” endocrine - affects distant cells

Question 24

Describe the relevant general morphologic features of endocrine cells/organs/tissues

Answer 24

• fenestrated capillaries
• surrounded by close + extensive capillary (fenestrated) network
• cells lack polarity - more specifically most lack of true “apical” surface
• have prominent basal surfaces usually due to secretions

Question 25

What are the two types of hormones (per the slides) and their characteristics

Answer 25

1) Protein hormones (amino/peptide) - usually extracellular receptors, not lipid soluble, often soluble in aqueous environments and do not require carriers 2) Steroid Hormones - mostly constitutive secretion - regulated by how fast secreted - often have carrier proteins, and/or binding proteins - lipid soluble - intracellular receptors

Question 26

Three types of hormone receptors

Answer 26

- cell membrane - intracellular - nuclear membrane

Question 27

Control of hormones

Answer 27

- via releasing factors --> positive feedback | - via inhibiting factors --> negative feedback

Question 28

What are the two relevant nuclei in the hypothalamus discussed in lecture

Answer 28

- PVN (paraventricular nuclei) | - SON (supraoptic nuclei)

Question 29

Describe the components of the Pituitary Neurohypophysis

Answer 29

= posterior pituitary - Neuropil = descending axons from hypothalamic neurons form PVN, SON - Capillaries = sinusoidal by anatomical size (walls are fenestrated) - Pituicytes = resident glial cells - control the blood/brain barrier - Herring Bodies = dilated endings of axons, containing hormones for release into circulation

Question 30

What are the hormones secreted from neurohypophysis

Answer 30

1) ADH - targets kidney collecting ducts - FXN: water retention 2) Oxytocin - FXN: milk "let-down"

Question 31

What is the unique pituitary circulation and where have we seen it before

Answer 31

= Venous portal system - has two capillary beds connected by a vein - 1st time we saw this was in liver portal system

Question 32

Define the different anatomical features of the two parts of the pituitary gland

Answer 32

``` 1) Neurohypophysis = Posterior Pituitary - 3 parts A) Pars Nervosa B) Infundibular Stalk C) Median Eminence 2) Adenohypophysis A) Pas Distalis B) Pars Intermedia C) Pars tuberalis ```

Question 33

Describe the pituitary embryology and give a brief overview of the steps of development

Answer 33

- Two parts of pituitary are formed from 2 separate tissues A) Neural ectoderm forms the neurohypophysis B) Oral Ectoderm forms the adenohypophysis - Steps in development 1) Beginning formation of Rathke's pouch from oral ectoderm and infundibular process from neural ectoderm 2) Neck of Rathke's Pouch gets constrained by growth of mesoderm 3) Rathke's pouch pinches off 4) Pinched off segment conforms to neural process - forming pars distalis, pars intermedia, pars tuberalis 5) Pars tuberalis encircles infundibular stalk (settles into mature conformation)

Question 34

What are the 5(7) hormones produced from the adenohypophysis, their corresponding staining and function

Answer 34

1) Growth Hormone: GH, SST - Acidophil - FXN: growth 2) Prolactin (PRL) - acidophil - FXN: milk secretion 3) Adrenocorticotropin (ACTH) - Basophil - FXN: Adrenal Cortex Hormone 4) Gonadotropins: FSH + LH - Basophil - FXN: stimulates germ cell development 5) Thyroid Stimulation hormone (TSH) - Basophil - FXN: thyroid hormone

Question 35

Describe the 5 layers (outside-->in) of the adrenal gland and relevant hormone types produced from each

Answer 35

1) Capsule 2) Cortex: Zona Glomerulosa - secretes mineralcorticoids 3) Cortex: Zona Fasiculata - secretes glucocorticoids 4) Cortex: Zona reticularis - secretes gonadocorticoids 5) Adrenal Medulla - secretes NE + Epi

Question 36

Describe the embryologic origin of the adrenal gland

Answer 36

- Cortex and medullar are from 2 separate embryologic origins - Neural crest cells - develop into chromatin cells + migrate into developing cortex and invade center to give rise to the medulla - Cortex comes from the intermediate mesoderm?

Question 37

Discuss the blood supply/flow of blood of the adrenal gland

Answer 37

- 2 routes for blood to travel in adrenal gland 1) Capsular artery --> cortical arteriole --> capillary bed through the cortex via adrenocortical sinusoid --> adrenomedullary collecting vein (in zona reticularis) --> Medullary capillary --> central adrenomedullary vein 2) Traverse cortex via medullary arteriole (from capsular artery) --> medullary capillary --> central adrenomedullary vein - pathway #2 allows a decreases the collection of cortical compounds on the way to medulla = effective way to supply/get to just the medulla

Question 38

What are the major hormone products of each part of the adrenal cortex, what type of corticosteroid they are, and their function

Answer 38

1) Aldosterone (mineralocorticoid) - from zona glomerulosa - FXN: blood pressure/ sodium absorption 2) Cortisol (glucocorticoid) - from zona fasciculata - FXN: Fat/Carb/Protein mobilization; ACTH influence 3) Dihydroepiandrostenidone (DHEA) (androgens) - from zona reticularis - FXN: secondary sex characteristics

Question 39

What are the major hormone products of each part of the adrenal medulla, and what cell is responsible for them

Answer 39

= Chromaffin cells | - Secrete epinephrine (adrenaline) + NE (noreadrenaline)

Question 40

What are the hormone products of the thyroid gland, what cells do they come from, and what is their function

Answer 40

1) T3 (triodothyronine) + T4 (thyroxine) - from the follicular cells - FXN: Protein syntehsis/degradation, glycogenesis, lipolysis, HR, General growth + metabolism 2) Calcitonin - from C-cells (parafollicular cells) - FXN: lowers blood calcium

Question 41

Describe thyroid embryology

Answer 41

- developed early in embryonic life from the foregut endoderm - near the base of developing tongue - (parathyroids from pharyngeal pouches)

Question 42

Describe the thyroid production of T3 and T4

Answer 42

- Thyroglobulin is made from follicular cells and secreted into colloid - In colloid it forms MIT (monoiodinated thyroglobulin) + DIT (diiodinated thyroglobulin) = the storage form of bound iodine - these molecules are endocytosed and exposed to lysosomes to release the iodine to be used for T3/T4 synthesis (colloid components recycled)

Question 43

Describe the ultrastructure + shape of follicular cells

Answer 43

- Shape of follicular cells is highly dependent on their level of activity - can range from columnar to cuboidal Ultrastructure includes: - Rich basal rER - connected via tight junctions - nucleus is round + central - apically have golgi complexes, secretory granules, phagosomes/lysosomes, microvilli

Question 44

What are two thyroid pathologies

Answer 44

- Goiter = from iodine deficiency (increases TSH production) | - Grave's Disease = chronic stimulation and release of thyroid hormones

Question 45

Describe the Hormones released from the parathyroid glands, the cells that release them and their functions

Answer 45

1) Parathormone (PTH) - PTH Principal cells (chief cells) = 95% of the cells - FXN: calcium regulation (antagonist of calcitonin) - darkish staining cells 2) Oxyphil cells - unknown hormone or function - 5% of the cells - light staining cells

Question 46

Describe the hormone produced by the pineal gland and other components of the gland

Answer 46

- Hormone = melatonin - Hormone producing cell = pinealocytes - may contain lipofuscin - FXN: in circadian rhythms - also have glial cells here - Brain Sand (Corpora arencea) = calcified metabolic product + identifier of pineal gland in histology

Question 47

Describe the hormones produced by the pancreatic islets (in the order they are developed), the cells that produce them, and their function

Answer 47

1) Glucagon - produced by alpha cells - FXN: raises blood glucose 2) Insulin - produced by beta cells - FXN: lowers blood glucose 3) SST - produced by delta (D) cells - FXN: inhibits pancreatic secretions 4) Pancreatic polypeptide (PP) & Vasoactive intestinal peptide (VIP) - produced by PP (D) 5) Ghrelin - produced by E cells - FXN: appetite regulation

Question 48

What is the Diffuse Neuroendocrine System (DNES)

Answer 48

- Neuroendocrine compounds (cells) in the GI and respiratory system - below is a partial list of examples in GI followd by their secreting cell in parenthesis (not to be memorized - Stomach: Gastrin (G) + SST (D) - Duodenum/Jejunum: Secretin (S) + CCK (I) + Glucose-dependent (K) + SST (D) + Motilin (M) - ileum/colon: enteroglucagon (L) + Peptide YY [abbrev. PYY] (L) + Neurotensin (N) + SST (D)